NONLINEAR DYNAMICS AND SYNCHRONIZATION OF TWO COUPLED PIPES CONVEYING PULSATING FLUID

In this paper, the nonlinear dynamical behavior of two coupled pipes conveying pulsating fluid is studied. The connection between the two pipes is considered as a distributed linear spring. Based on this consideration, the equations of motion of the coupled two-pipe system are obtained. The two coupled nonlinear partial differential equations, discretized using the fourth- order Galerkin method, are solved by a fourth-order Runge-Kutta integration algorithm. Results show that the connection stiffness has a significant effect on the dynamical behavior of the coupled system. It is found that for some parameter values the motion types of the two pipes might be synchronous.     

直升机卫星通信系统关键技术研究

基于直升机卫星通信系统的特点,分析了卫星通信系统中姿态角提取、坐标变化及抗遮挡等关键技术,采用链路分析估算方法,提出了针对关键技术点的测试方案设计,通过工程案例验证,实现了对系统的测试与评估。     

噢易机房BOSS系统在实践中的应用及分析

噢易机房BOSS系统提供Dos和Windows双模式操作,教学可能需要很多个不同类的操作系统,不同的系统里面安装不同的教学软件,安装第一个系统的时候从这个系统中创建多个频道,频道和真实的系统完全一样。这样的话可以减少磁盘的使用空间,方便维护与管理,可快速搭建个人私密的开放系统环境,方便学生在机房保存学习资料、完成作业或进行课程设计、毕业设计等任务。     

网购平台在线声誉机制作用的实证研究方法评析

在线声誉机制是网购平台重要的信号机制,是平台可持续成长的基础.从理论基础、研究假设、数据来源、变量选择、模型应用等方面,全面梳理了在线声誉机制作用的实证研究方法,包括Hedonic回归、Logit、Probit、Poisson、Tobit、截取正态回归、样本选择回归、固定效应、广义最小二乘法等模型的应用.最后展望未来相关研究及方法,并构建在线声誉机制作用的实证研究综合框架.     

基于信息管理系统在水利工程建设管理中的应用探讨

本文提出采用信息管理系统加强对水利工程建设进行管理,阐述了信息系统应用于水利工程建设中的必要性,并针对水利工程管理信息系统中存在的问题进行论述,归纳和总结出几点改善措施,希望能够为全面提升水利工程管理工作效率提供保障.     

LED微阵列投影系统设计

为满足便携式投影仪的市场需求,设计了一种基于LED微型阵列的投影系统。该系统由显示单元和投影物镜构成。采用尺寸为12 mm×9 mm的自发光LED微型阵列作为系统的显示单元,利用光学设计软件设计了投影物镜。投影物镜采用反远距光学结构,全视场角为80°,焦距为8 mm,属于强光、广角镜头。在空间频率20 lp/mm处,该物镜的调制传递函数大于0. 85,畸变小于2%,符合投影系统的设计要求。该投影系统具有体积小,结构简单,投影效果好,易加工等诸多优势,可为第三代投影技术的发展提供参考。     

Ethylthio-substituted sandwich phthalocyaninato europium (III) semiconductors for sensing NO2 and NH3: Effect of the extended π-conjugate systems on tuning the conductivity and sensing behavior

By using the π-conjugated phthalocyanine macrocycle as the versatile building block, a series of five sandwich-type ethylthio substituted phthalocyaninato europium complexes, namely double-decker Eu[Pc(SC₂H₅)₈]₂ (Pc-1), triple-decker Eu₂[Pc(SC₂H₅)₈]₃ (Pc-2), and their corresponding dimers, [Pc(SC₂H₅)₈]₂Eu₂[BiPc(SC₂H₅)₁₂] (Pc-1@Pc-1), [Pc(SC₂H₅)₈]₃Eu₃[BiPc(SC₂H₅)₁₂] (Pc-1@Pc-2) and [Pc(SC₂H₅)₈]₄Eu₄[BiPc(SC₂H₅)₁₂] (Pc-2@Pc-2), are synthesized and prepared into the solution-processed films by a simple quasi-Langmuir-Shäfer (QLS) method. Combination between the extending π-conjugated system in the longitudinal and transverse directions of Pc macrocycles and/or radical nature of Pc-1 unit among different semiconducting molecules result in unusually small energy gaps (0.345–0.91 eV). Consequently, all of the semiconductors exhibit excellent conductivities. Among these materials, the conductivity for the radical species Pc-1@Pc-1, Pc-1@Pc-2 and Pc-1 is about 3–4 times larger than that for the non-radical compounds Pc-2@Pc-2 and Pc-2. Moreover, the QLS films of five semiconductors take excellent linear responses for both oxidizing NO₂ (100–300 ppb) and reducing NH₃ (4–8.6 ppm). Respectively, the sensitivity (in % ppm⁻¹) gets increased in the order of Pc-1 < Pc-2 < Pc-1@Pc-1 < Pc-1@Pc-2 < Pc-2@Pc-2 for NO₂, and Pc-1@Pc-2 < Pc-1 < Pc-1@Pc-1 < Pc-2@Pc-2 < Pc-2 for NH₃. Depending on the highly extended π-conjugated systems, Pc-2@Pc-2 and Pc-2 films achieve the highest sensitivity of 208.2% ppm⁻¹ and 0.97% ppm⁻¹ to NO₂ and NH₃, respectively. In addition, with a less than 2 min response time within a limit of detection at 10 ppb for NO₂ and 0.48 ppm for NH₃, good reproducibility and selectivity have been revealed for the Pc-2@Pc-2 and Pc-2 films among the best gas sensors obtained so far for all the solution-processed films based on organic semiconductors in dry air at room temperature. More importantly, it is firstly demonstrated that the high NO₂ sensing is resulted from low Oxd₁, and high NH₃ sensing is resulted from high Red₁ among the sandwich Pc-based semiconductors.     

Synthesis and Structure Determination of SCM-15: A 3D Large Pore Zeolite with Interconnected Straight 12×12×10-Ring Channels

A new germanosilicate zeolite named SCM-15 (Sinopec Composite Material No. 15), the first zeolite containing a 3-dimensional (3D) channel system with interconnected 12-, 12-, and 10-ring channels (pore sizes: 6.1×7.2, 6.1×7.4, and 5.2×5.9 Å), has been synthesized using neutral 4-pyrrolidinopyridine as organic structure-directing agents (OSDAs). Its structure has been determined by combining single-crystal electron diffraction (SCED) and synchrotron powder X-ray diffraction (SPXD) data. The unique open framework structure of SCM-15 is related to that of FOS-5 ( BEC ), ITQ-7 ( ISV ), PKU-16 ( POS ), ITQ-26 ( IWS ), ITQ-21, Beta polymorph B, and SU-78B, since all these framework structures can be constructed from similar chains which are connected through shared 4-ring or double 4-ring (d4r) units. Based on this relation, six topologically reasonable 3D large or extra-large pore hypothetical zeolites are predicted.     

On the dynamics of the Szekeres system

The gravitational Szekeres differential system is completely integrable with two rational first integrals and an additional analytical first integral. We describe the dynamics of the Szekeres system when one of these two rational first integrals is negative, showing that all the orbits come from the infinity of ${\mathbb{R}}^4$ and go to infinity.