水泥混凝土路面板使用寿命分析

根据不同的情况,找出现有水泥混凝土路面板破坏的原因,对使用寿命进行分析,为以后水泥混凝土路面板设计提供依据。     

Quantitative study of the effect of electromagnetic field on scale deposition on nanofiltration membranes via UTDR

Ultrasonic time-domain reflectometry (UTDR) as an in situ, non-invasive real-time technique has been successfully utilized to quantify membrane fouling and cleaning. This study describes an existing ultrasonic technique for quantitative study of the effect of magnetic fields on CaCO₃ scale deposition on the membrane surface during crossflow nanofiltration (NF). The fouling experiments were conducted with CaCO₃ solution containing Ca²⁺ of 1.8 and 3 mmol/L. The experimental electromagnetic field (EMF) was 0.02 T. A commercial NF membrane and a highly sensitive ultrasonic sensor were used in all the experiments. Results show a good relationship between the ultrasonic measurements and the development of CaCO₃ scale on the NF membrane surface. An increase in the amplitude of differential signal with operation time results from the deposition of the CaCO₃ scale layer. In addition, the movement of the differential signal in the time domain observed is associated with an increase in the thickness of the fouling layer. The UTDR technique is capable of measuring the rate of fouling layer formation under different treatment conditions, i.e. with non-magnetic field (NMF) and EMF. Scale layer of deposited CaCO₃ obtained in the experiment with NMF is denser and thicker than that with EMF. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses imply that the magnetic treatment suppresses the formation of calcite crystals and prefers vaterite and aragonite. Furthermore, the ultrasonic technique is sensitive to the different fouling rate between experiments carried out with 1.8 and 3 mmol/L CaCO₃ solutions. The thickness of the fouling layer measured by weight measurement is consistent with that obtained by UTDR in real time. The thinner and less dense scale layer is the main reason for the slower flux decline. Overall, independent measurements such as the flux-decline data, SEM analysis and weight measurement corroborate the ultrasonic measurements.     

泰州财富广场规划方案创作随笔

通过对泰州财富广场规划方案的创作,体会到在旧城改造中,应复兴城市历史延绵中形成的繁华商业活动中心,增强城市的活力和内聚力,它不应是传统商业街的旧形态,而是对城市空间的再评价,再认识和再塑造.     

我国城市机动化问题的认识与对策

小汽车快速增长既是我国大城市当前一个普遍现象，也是各界争议的热门话题，本文试图站在客观公正的立场上讨论小汽车增长的机制动因利弊得失，澄清机动化的概念可能的途径以及对城市发展的影响，阐明中国城市在快速城市化和机动化双重压力下，应该采取的正确对策。     

Sharpening polycrystalline phase boundary for potassium sodium niobate ceramics with MnF2 modification

The influence of anion on structure and performance is unclear in potassium sodium niobate ((K,Na)NbO₃; KNN)-based ceramics, while cation doping has been widely researched. Here, the phase structure and electrical properties are explored in MnF₂-doped KNN ceramics. Significantly, sharp rhombohedral–orthorhombic (R–O) and orthorhombic–tetragonal (O–T) phase boundary as well as reduced diffusion degree is exhibited in the ceramics along with little changed phase transition temperatures due to the optimized F⁻ content at O site, which is different from that of cation replacement for A and B sites. Notably, the domain wall motion is facilitated due to the increased A vacancy and decreased O vacancy along with strengthened polarity, originating from the higher valence state and electronegativity of F⁻ with respect to O²⁻. And then, enhanced ferroelectricity is realized via MnF₂ modification, the piezoelectricity is elevated in turn. This work presents a new idea of anion doping for controlling structure and properties in perovskite materials.     

直流电机换向火花的检测与调整

分析了直流电机换向火花产生的主要原因,提出了如何对电磁部分和机械部分引起的火花进行检测,通过检测得到正确判断,进行恰当地调整,使电机运行状况得到改善。     

坦克扭力轴刚性变化实验研究

分析了扭力轴刚性对坦克的舒适性和可靠耐久性的影响,阐述了随行驶里程的增长扭力轴刚性的变化。通过实验,对2种型号不同行驶里程的坦克扭力轴刚度变化进行了研究,得到了其变化趋势;实验结果表明:随行驶里程的增长扭力轴的刚性会降低,车辆悬挂性能下降,舒适性提高。     

空空导弹单吊挂在轨分离安全分析

单吊挂在轨的分离安全分析是采用轨式发射的空空导弹系统总体设计的重要内容之一,其分析主要包括弹体干涉分析和吊挂阻滞分析。文中对基于允许值的空空导弹单吊挂在轨的分离安全分析方法进行了介绍,阐明影响单吊挂在轨段分离安全的因素,提出解决措施,最后以某型导弹为例进行了分析。文中的方法可为弹架分离安全性设计提供参考。     

Preparation and characterization of porous PDMS beads for oil and organic solvent sorption

In this article, poly (dimethyl siloxane) (PDMS) porous beads were prepared by suspension polymerization method using n‐octane and carbon tetrachloride (CCl₄) as diluents and pore formation agents. The apparent density, porosity and other characteristics were characterized. The absorption experiments showed that the porous PDMS beads exhibited more absorption capacity and faster absorption rate toward oils than the nonporous or oligoporous PDMS beads did, moreover they are of remarkable stability and recyclability, which could provide a path to absorb the oils floating on water. POLYM. ENG. SCI., 54:2965–2969, 2014. © 2014 Society of Plastics Engineers     

Sintering Behavior and Dielectric Properties of Ultra‐Low Temperature Fired Silver Molybdate Ceramics

Ag₂MoO₄ ceramic was prepared by using the solid‐state reaction method, which could be sintered at 450°C for 2 h, having a relative permittivity of 8.08, a Qf value of 17 000 GHz, and a temperature coefficient of resonance frequency about ?133 ppm/°C. Ag₂MoO₄ ceramic was chemically compatible with silver but reacted seriously with aluminum to form (Ag_0.5Al_0.5)MoO₄ during the sintering. The fitting of infrared spectra and the Shannon's additive rule were employed to study intrinsic dielectric behaviors of the ceramics at microwave region. Ionic displacive polarization and the electronic polarization contributed almost equally to the dielectric permittivity of the ceramic at microwave region. The Ag₂MoO₄ ceramics could be a good candidate for ultra‐low temperature co‐fired microwave devices.