羽绒服防钻绒性试验方法探析

羽绒服防钻绒性试验方法的研究一直是制约羽绒制品发展的瓶颈.科学有效的测试方法与试验设备对羽绒服防钻绒性能的研究影响重大.本文将以中华人民共和国国家标准(GB/T12705-91)中规定的织物防钻绒性试验方法为依据,同时比较国外在该领域的发展状况,深入分析国家标准试验方法中试验原理与设备的科学性、有效性,提出现有的回转箱测试方法可能存在的不足,探讨防钻绒性试验方法与设备研究的新思路.     

群桩横向非线性力学响应的三维有限元数值模拟

利用有限元软件ANSYS,针对群桩横向力学响应问题,进行了三维有限元数值模拟.计算模型中,考虑了土体的材料非线性、桩-土界面状态非线性等因素,对群桩横向力学响应的影响.通过算例分析,验证了模型的正确性.在此基础上,进一步研究了群桩-土横向相互作用的非线性特性,计算结果对于桩基础的分析和设计,有较好的参考价值.     

Analysis of finite-time practical stability for time-varying polytopic systems

The problem of finite-time practical stability (FTPS) for time-varying polytopic systems is discussed. Three equivalent conditions for FTPS are first proposed. To facilitate the system analysis, a sufficient linear matrix inequality (LMI) criterion on the FTPS is further provided. The definition of finite-time practical boundedness and a sufficient LMI criterion are also provided to overcome the exogenous disturbance. A numerical example is used to illustrate the effect of the proposed approach.     

DS1306实时时钟与PIC单片机构成的应用系统设计

对比分析了几种实时时钟芯片的功能,说明DS1306的应用优势.介绍了SPI串行总线结构及一种DS1306与PIC16F73单片机构成的应用系统的接口电路和控制程序,通过应用系统设计总结了其使用特点.应用系统的设计证明,DS1306是一种性能优良、使用方便的器件.     

低分辨率人脸图像识别性能研究

首先介绍了人脸识别中常用的PCA方法、LDA方法和Fisherface方法,然后通过在ORL数据库和Yale数据库上的试验发现当分辨率从原始分辨率降低到20×20左右的过程中,原始空间、PCA子空间和Fisherface子空间方法的识外浊能均没有显著变化．降低分辨李能有效提高现有人脸识剐算法的速度．     

综采工作面旋转调斜对接工艺研究

针对淄博矿业集团岱庄煤矿4324不规则综采工作面需两次旋转调斜的现实,通过分析旋转调斜对接工艺参数、工艺设计及对接方法,提出在此类顶底板条件下采用虚心旋转调斜是十分合适的,虚心旋转调斜比实心旋转调斜更有利于工作面的生产。该研究解决了岱庄煤矿不规则工作面的综采问题。     

基于消息队列遥测传输协议的灌溉系统

现有物联网应用领域存在性能差、安全性低、个性化智能推送不足等问题,为此,基于消息队列遥测传输(message queuing telemetry transport,MQTT)协议、NodeMCU开发板、阿里钉钉APP,提出一种自动灌溉系统。采用高级加密标准(advanced encryption standard,AES)与MD5信息摘要算法改进MQTT数据传输协议,实现数据的安全推送与交互、作物的远程智能灌溉与数据的实时监测,既保证了数据安全稳定高速地传输,用户又能根据个性化需求和消息传递性能要求,满足农业生产中的规模化的自动灌溉作业。测试结果表明,该系统安全性强、推送成功率高,消息发送和接收时间短,系统的可扩展性强,此外开发成本方面也具有较大的优势,可以满足目前物联网发展的需求。     

n-Pentylamine-intercalated layered perovskite-type oxide

A novel n-pentylamine-intercalated layered perovskite-type oxide, C5H11NH3-Sr2Nb3O10, was prepared and characterized by using XRD, FT-IR, Raman spec-trascopy, and elemental analysis. It was shown that the intercalated n-pentylamine adopted a bilayer formation with some overlap and tilt, and the lattice of the perovskite layer was distorted due to the intercalation of n-pentylamine. The as-prepared sample gave clear electric hysteresis loop and did not show fatigue after 1011 switching circles, and therefore, could be considered as a new kind of fatigue-free ferroelectric materials.     

Rb-Sr chronological characteristics of Jurassic granitoid gravels in north margin of Dabie block, Central China

Granitoid gravels are discovered from alluvial fan conglomerates, the base of Jurassic Fenghuangtai Formation (J₂ ²), in the north margin of Dabie block and the south part of the Hefei Basin. These granitoid gravels make up 5%–10% of all gravels by volume percent. For the four components, K-feldspar, biotite, amphibole and whole rock divided from two selected granitoid gravel samples, their Rb-Sr isotopes are measured, which gives two formation ages of granitoids: (428±20) Ma and (430±54) Ma, and means that the Early Paleozoic granitoid intrusive rocks once existed in the Dabie Mountain provenances of Jurassic. The granitoids occur in the tectonic setting of post-collision uplift according to lithogeochemical discriminant analysis.