红枣环磷酸腺苷提取工艺的条件优化

目的优化红枣(Zizyphus jujube)环磷酸腺苷(cAMP)索氏提取工艺。方法以料液比、超声提取时间、索氏提取时间为影响因素,采用单因素试验和正交试验对超声波辅助索氏提取法提取红枣环磷酸腺苷的工艺进行优化,在此基础上,采用大孔吸附树脂法对粗提物进行纯化。结果单因素实验结果发现,环磷酸腺苷的提取率随料液比的增加而升高,当料液比超过1:25后趋于稳定;随超声提取时间的增加先升高,25 min后略有下降;随着索氏提取时间增加而升高。对正交试验极差分析和方差分析发现料液比(A)对红枣环磷酸腺苷的提取影响显著,超声时间(B)、索氏时间(C)对红枣环磷酸腺苷的提取影响不显著。各因素影响先后顺序为ABC,最佳提取条件为料液比1:30,超声时间30 min,索氏提取时间5 h,此时提取率达到1591.16μg/g。结论超声波辅助索氏提取法能增强红枣环磷酸腺苷的提取率。     

基于信息压缩矩阵交替变换的分数阶系统结构、阶次与参数的同时辨识方法

在愈来愈被关注的分数阶控制研究中,分数阶系统辨识的理论与方法是一个重要方向. 目前相关研究极少涉及分数阶系统的结构和阶次辨识. 首先讨论了分数阶线性SISO系统辨识的有色噪声模型,然后构造了具有"移位性质"的信息向量和信息压缩矩阵,并给出了信息压缩矩阵分解变换的理论分析及其证明;在此基础上,提出了一种利用信息压缩矩阵交替变换提取相关信息的算法,论述了最优估计模型结构与阶次的判定准则,从而同时辨识分数阶系统时域模型的结构、阶次与参数;仿真研究表明,本文方法能够获得满意的辨识结果,具有良好的抑制噪声干扰能力;不仅能够准确地辨识系统模型的结构与阶次,而且能够辨识噪声模型的结构与阶次.     

4种不同涂膜处理对软枣猕猴桃贮藏品质的影响

目的 探究不同涂膜处理对采后软枣猕猴桃贮藏品质的影响。方法 以烟台“丰绿”软枣猕猴桃为实验材料,用褐藻酸钠、褐藻寡糖、壳聚糖、壳寡糖4种涂膜剂对采摘后的软枣猕猴桃进行涂膜处理,对其贮藏期间相关品质指标及果实形态变化进行检测分析。结果 在20℃贮藏过程中,与对照组相比, 4种处理在一定时间内均能抑制软枣猕猴桃果实质量损失率和软化程度,减少可溶性固形物、维生素C含量的下降,有效控制果实腐烂率。在贮藏过程中可使软枣猕猴桃果实保持较高水平的超氧化物歧化酶、过氧化氢酶、过氧化物酶活力。结论 综合分析,成熟的软枣猕猴桃在20℃贮藏环境中,褐藻寡糖涂膜处理保鲜效果最优,更有利于果实的贮藏。     

火车轮裂纹检测传感器的研究

火车的车轮在高速行驶的过程中,由于受到各方面力的作用,可能会产生裂纹,需要对其进行检测。本文从声发射的机理出发,一步步阐述了一种新型的声发射传感器——火车轮裂纹检测传感器设计的原理,同时给出了其中内置的前置放大器的设计原理及结构图。传感器使用固体材料作为传感器的传播介质,用新型的压电材料作为敏感元件,提高了灵敏度。     

含孤石的山坡建筑地基处理

针对山坡建筑地基特点提出了３种基础处理型式,对含孤石的某山坡建筑群,采用型式二,把挖孔,桩基和独立柱基结合使用,解决受力问题,避免了大量的挡土墙,孤石一基础也到了妥善处理。     

Towards 6G wireless communication networks:vision,enabling technologies,and new paradigm shifts

The fifth generation(5G)wireless communication networks are being deployed worldwide from 2020 and more capabilities are in the process of being standardized,su...     

STBC-Based (Turbo) STTC Codes Built by Set Partitioning for Three Transmit Antennas: Construction and Performances

Simulating wideband fading channels, multiple-input multiple-output (MIMO) channels, and diversity-combined fading channels often demands the generation of multiple uncorrelated Rayleigh fading waveforms. In this letter, two appropriate parameter computation methods, namely the method of exact Doppler spread (MEDS) and L_p -norm method (LPNM), for deterministic sum-of-sinusoids (SoS) channel simulators are investigated to guarantee the uncorrelatedness between different simulated Rayleigh fading processes. Numerical and simulation results show that the resulting deterministic SoS channel simulator can accurately and efficiently reproduce all the desired statistical properties of the reference model     

基于三层分布式技术的公路收费系统的研究

该系统结合数字音视频监控技术、网络技术和数据库技术,提高公路收费过程、财务管理的自动化程度;提高工作效率和服务质量,最大限度地增加政府非经营性公路的管理透明度,防止票款流失,杜绝假票和违规收费,确保收费及时、足额地上缴国库。     

Performance evaluation for underlay cognitive satellite-terrestrial cooperative networks

With the continuously increasing demand for broadband applications and services, underlay cognitive satellite-terrestrial networks, enabling to accommodate better wireless services within the scarce spectrum, have attracted tremendous attentions recently. In this network, satellite communications are allowed to operate in the frequency bands allocated to terrestrial networks under the interference constraints imposed by terrestrial network, which may lead to a performance degradation of the satellite network. To guarantee the performance of the primary terrestrial network as well as the secondary satellite network, we introduce the cooperation into cognitive satellite-terrestrial networks and investigate the performance of the new framework, i.e., cognitive satellite-terrestrial cooperative network (CSTCN). Specifically, by restricting the transmit power of satellite communications with interference power constraints imposed by terrestrial communications, we firstly obtain the received signal-to-interference-plus-noise ratio (SINR) of the considered network. Moreover, by employing the moment generating function (MGF) approach, closed-form expressions for symbol error rate (SER) and outage probability (OP) of the considered cognitive network are derived. The analytical results obtained in this paper can provide theoretical support for optimizing the performance of satellite-terrestrial networks.     

汽车液压助力转向器计算机测控系统的研究

设计了汽车液压助力转向器计算机测控系统。系统应用先进的计算机测控原理与信息技术,采用微机控制液压系统和伺服电机系统来模拟转向器在现场的工作状况,实现了驱协与加载方式的自动化。该系统性能稳定、操作简单、测量速度快、测试精度高。