不同钢结构体系的稳定问题分析思路探讨

钢结构体系的建立是结构设计上的重点难点,其对结构的稳定性起到关键影响。很多工程师面对复杂的钢结构布置无从下手,或模型出现严重漏洞而无法解决。本文从钢结构体系的建立入手,通过屈曲分析、p-Δ分析、计算长度等分析方法对两个钢结构模型进行计算,解决工程上强弱支撑体系的确定、计算长度系数、二阶分析等核心稳定问题并梳理设计思路。     

基于带通Σ-Δ调制器的硅微机械陀螺力反馈闭环检测

为了提高硅微机械陀螺(SMG)的性能,研究了一种基于四阶机电结合带通Σ-Δ调制器(SDM)的硅微机械陀螺力反馈闭环检测方法。基于谐振器级联谐振前馈(CRFF)结构设计了该方法的仿真模型,并利用商用软件SD TOOLS计算了环路参数。采用MATLAB/SIMULINK对设计结果进行了行为级仿真,结果表明,1 Hz条件下环路的信噪比达到了109.2dB,符合设计预期。在此基础上,以现场可编程门阵列(FPGA)为数字处理核心搭建了硅微机械陀螺数字化测控电路并进行了性能测试。结果表明,采用带通SDM闭环检测技术和数字化闭环驱动技术后,硅微机械陀螺的Allan方差零偏不稳定性约为1.15(°)/h,角度随机游走约为7.74×10-2(°)/√h,且信噪比参数满足了设计目标。得到的结果证明了设计方法的正确性;显示提出的带通SDM力反馈闭环检测方法有助于提高SMG的性能,拓展其应用领域。     

Fatty acid composition of several wild microalgae and cyanobacteria, with a focus on eicosapentaenoic, docosahexaenoic and α-linolenic acids for eventual dietary uses

A total of 13 species of microalgae and 14 strains of cyanobacteria, collected directly in the Portuguese coast and lagoons, were characterized for their fatty acid contents, focusing on two with a market potential — i.e. eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA); and another already with alternative (yet somehow more expensive) natural sources — i.e. α-linolenic (ALA) acid. The purpose of this work was their eventual inclusion as additives in food or feed. ALA was the most abundant PUFA in Nannochloropsis sp. (0.616 ± 0.081 mg_FA.L_culture^{− 1}.d^{− 1}), and EPA in Phaeodactylum tricornutum (0.148 ± 0.013 mg_FA.L_culture^{− 1}.d^{− 1}); Pavlova lutheri was particularly rich in EPA (0.290 ± 0.005 mg_FA.L_culture^{− 1}.d^{− 1}) and DHA (0.140 ± 0.037 mg_FA.L_culture^{− 1}.d^{− 1}). Despite several previous reports on similar topics and encompassing some of our microalgal species, the wild nature of our strains accounts for the novelty of this work — in addition to the characterization of a few wild cyanobacteria. Eustigmatophyceae class was the best producer of ALA, while Prymnesiophyceae was the best for EPA and ALA. Nodularia harveyana exhibited the highest ALA level (0.611 ± 0.022 mg_FA.L_culture^{− 1}.d^{− 1}) and Gloeothece sp. was highest in EPA (0.030 ± 0.004 mg_FA.L_culture^{− 1}.d^{− 1}).     

近红外光谱仪数据采集系统的研制

根据阵列检测型近红外光谱仪对采集卡动态范围和信噪比的要求,设计和实现了以USB2.0为通信协议的16位数据采集系统。系统采用Δ-∑模数转换器ADS1610,将CCD信号数字化。应用可编程逻辑技术,实现了TCD1304检测器的驱动和积分时间的256挡选择。系统的有效分辨率为15位,信噪比为58 dB,缓存容量为4K×16 bit,CCD积分时间30 ms~0.5 s可编程控制。研制的采集系统与分光系统结合,具有很好的市场价值和应用前景。     

磁力测量在隐伏含铁建造型金矿床及外围矿权区中的应用

坦桑尼亚某金矿区及外围矿区均处在空旷的季节性沼泽地带内,由于受自然条件的限制,在地质（没有基岩露头）、化探（沼泽性黑土覆盖厚度大）、电法（低阻屏蔽干扰严重）等找矿方法效果均不佳的情况下,磁力测量发挥了间接寻找隐伏含铁建造型金矿床的重要作用,取得了反映地下深部与金矿床有关的含铁建造引起的良好磁力异常,为矿区和外围矿区的钻探工程布置,进一步扩大矿床规模,提供了强有力的磁测资料。     

Spectrophotometric study of the copigmentation of malvidin 3-O-glucoside with p-coumaric,vanillic and syringic acids

Anthocyanins are a natural source of pigments in plants and their processed food products have become attractive and excellent candidates to replace the synthetic colourants due to their characteristic intense colours and associated health benefits. The intermolecular copigmentation between anthocyanins and other colourless compounds has been reported to be an important way to enhance and stabilise the colour intensity of aqueous solutions. In the present work we report the equilibrium constant, stoichiometric ratio and the thermodynamic parameters (ΔG°, ΔH° and ΔS°) related to the intermolecular copigmentation reactions of the anthocyanin malvidin 3-O-glucoside with one hydroxycinnamic acid (p-coumaric acid) and two O-methylated hydroxybenzoic acids (vanillic and syringic acid). Different factors which affect their interactions such as copigment concentration, pH and temperature of the medium are examined at two pH levels (pH = 2.50 and 3.65) corresponding to those of the major food mediums where these reactions take place (fruit juices, wine, jams etc.).     

WBAN中Δ-Σ调制器的设计及纳米级实现

基于15 bit字长累加器和预设LSB噪声抑制技术,在90 nm CMOS工艺下对MASH结构Δ-Σ调制器进行了优化设计和实现。实验结果表明,优化后的Δ-Σ调制器能够在噪声抑制性能、器件尺寸及功耗上达到最优化的平衡,器件尺寸仅为40.5μm×45μm,功耗仅为34μW,满足无线人体局域网器件微型化和超低功耗的严格要求。作为阶段性研究,实验结果为下一步无线收发器的设计提供了重要的理论及设计参考。     

ΔLogR法估算页岩气储层有机碳含量探讨

页岩气测井评价的一项重要内容就是确定储层中的有机碳含量。为了能够较简便、准确地估算页岩气储层中有机碳含量,基于常规测井资料,通过ΔLogR法估算页岩储层有机碳含量实验,提出了求取有机碳含量的"RDT-TOC"直接关联法、"RTOC-DTTOC"法和适应中扬子地区海相页岩低阻储层的岩性密度法模型,并通过实例进行了验证分析。     

60kg级埋弧焊丝熔敷金属的疲劳裂纹扩展速率

采用MTS-810低频疲劳试验机,在试验频率为10 Hz条件下,应用三点弯曲法对两种60 kg埋弧焊丝熔敷金属进行裂纹扩展速率实验;绘制熔敷金属裂纹扩展速率da/dN与应力强度因子幅ΔK之间的关系曲线。结果表明:利用线性拟合法得到H08Mn2SiA焊丝匹配HJ431焊剂及SJ101焊剂的Paris方程C系数分别为7.5×10^(-42)和1.2×10^(-49),m系数分别为17.32和20.9,计算得出裂纹扩展门槛值ΔK_(th)分别为93.38 MPa·m^(1/2)和101.34 MPa·m^(1/2)。     

细长钢筋混凝土柱在地震荷载作用下的P-Δ效应

基于分层截面方法,对细长钢筋混凝土柱的P-Δ效应进行了研究。为了对钢筋混凝土柱的周期性行为进行有效分析(这种周期性行为可以根据外加轴向力的大小表现出荷载-位移关系曲线的改变),采用了分层截面方法,并且还采用程序在钢筋的应力-应变关系曲线中考虑了粘结滑移作用[Kwak HG,Kim JK.Implementation of bond-slipeffect in analyses of RC frames under cyclic loadsusing layered section method.Engineering Struc-tures2006,28(12):1715-27]。为了检验这种方法的有效性,以及确定在钢筋混凝土细长柱的综合反应中各种作用的重要性,采用了非线性动力分析方法对60组水平和竖向地震作用下位于常用范围内的长细和稳定度参数的构件进行分析。基于得到的大量分析结果,评估了轴向力、P-Δ效应和竖向地震力对结构反应的影响以及它们的相应贡献。此外,通过与精确的非线性动力分析中得到的结果相比较,评估了在钢筋混凝土结构的抗震设计中采用能力需求曲线的适用性。