低速大排量风能吸功泵流量特性研究

针对大功率液压型风力发电液压系统的需要,设计一种利用双圆柱凸轮驱动多排液压缸、换向阀配流的低速大排量风能吸功泵,并对所设计的风能吸功泵流量特性进行理论分析和仿真研究.提出在换向阀阀芯处增加节流槽,减小配油过程的压力冲击.根据换向阀的工作特点,建立了单腔室流量特性数学模型,得出在低转速工况下影响风能吸功泵内泄漏的主要因素...     

基于单片机AT89C52的漏磁检测实验系统开发

本文介绍了基于单片机技术的漏磁检测系统。首先介绍了漏磁检测的原理,然后结合电子电路技术,单片机技术,开发了一套漏磁检测实验系统。该系统包括信号的采集,预处理,模/数转换,数据结果存储,数据串口发送。单片机的软件系统采用模块化设计,分为数据采集、数据存储、数据串口发送模块等。     

基于E-Web的液体泄漏检测仪

针对管道液体泄漏的特点，提出一种泄漏预测方法并实施。首先介绍了液体泄漏预测的原理和方法，然后通过对液体泄漏检测仪的功能需求分析，建立了基于E-Web的检测仪功能模型。根据功能模型的要求，分别从软硬件的角度对检测仪的运行环境、体系结构、设计和实现方法进行深入的讨论。最后，指出在嵌入式设备网络化过程中应注意的一些关键问题。     

汽轮机侧齿汽封与梳齿汽封流动特性研究

对汽轮机上侧齿汽封和梳齿汽封进行建模,基于数值求解方法,用有限体积法对控制方程进行离散,并求解湍流模型的封闭方程组,在不同的进口压力下,分析了侧齿汽封和梳齿汽封的三维流动特性。分析结果表明侧齿汽封并不一定优于梳齿汽封,对于高低齿形式的汽封,梳齿汽封的密封性能较好,泄漏量较少,对于平齿形式的汽封,侧齿汽封的密封性能较好,泄漏量较少,转子的凸台对汽封泄漏量的影响很大。为汽封齿的设计加工提供了理论依据,为汽轮机的汽封改造提供了技术参考。     

Electric field dependence of ferroelectric stability in BiFeO3 thin films co-doped with Er and Mn

Bi_0.9Er_0.1Fe_1−xMn_xO₃ (BEFM_xO, x = 0.00–0.03) films are synthesized by a sol–gel technique. The BEFO film exhibits a conduction mechanism based on electron tunneling. The high applied electric field causes dissociation of the defect complex, and the resulting oxygen vacancies contribute to fake polarization. Consequently, the BEFO film has poor polarization stability at high applied electric fields. Coexistence of two phases (with space groups R3c:H and R3m:R) and reduced concentrations of oxygen vacancies and Fe²⁺ in BEFM_xO are achieved by co-doping with Er and Mn. The presence of bulk-based conduction in the BEFM_xO films then leads to ferroelectric domain switching contributing to the real polarization and to excellent ferroelectric stability. In addition, the BEFM_0.02O film shows a typical symmetrical butterfly curve, the highest remnant polarization of ~109 μC/cm², and the highest switching current of ~1.66 mA. It also has the smallest oxygen vacancy concentration and thus the smallest amount of defect complex, which means that there are fewer pinning effects on ferroelectric domains and therefore excellent ferroelectric stability. This excellent ferroelectric stability makes the BEFM_xO films obtain good stability and reliability in the application of ferroelectric memory devices.     

浅谈螺旋密封原理及在电动工具中的应用

介绍了螺旋密封的两种基本结构、工作原理及封液能力的计算和设计方法,得出螺旋密封无泄漏的条件。通过试验,验证了旋向问题的重要性,为螺旋密封的应用提供了经验。     

Dielectric properties of Fe-doped Ba0.65Sr0.35TiO3 thin films fabricated by the sol–gel method

Fe-doped Ba_0.65Sr_0.35TiO₃ (BST) thin films have been fabricated on Pt/Ti/SiO₂/Si substrate using the sol–gel method. The structural and surface morphology, dielectric, and leakage current properties of undoped and 1 mol% and 2 mol% Fe-doped BST thin films have been studied in detail. The results demonstrate that the Fe-doped BST films exhibit improved dielectric loss, tunability, and leakage current characteristics as compared to the undoped BST thin films. The improved figure of merit (FOM) of Fe-doped BST thin film suggests a strong potential for utilization in microwave tunable devices.     

干气密封的应用

在现代石化行业中,常常采用离心泵来输送液态烃,液态烃属于易燃、易爆的危险介质,一旦大量泄漏到环境中,将带来极大的安全隐患和环境污染,对生产装置的安全造成严重的威胁。因此,这类液态烃泵轴封的可靠性和密封性在很大程度上决定了泵是否能可靠、稳定、安全地运行。针对干气密封在液态烃泵上的应用进行了说明。     

Enhanced performance of sandwich structure Pb0.8La0.1Ca0.1Ti0.975O3 thin film for pyroelectric applications

Using the advantages of low-temperature crystallization and high orientation in Pb_0.8La_0.1Ca_0.1Ti_0.975O₃ (PLCT) film, a dense PLCT/porous PLCT/dense PLCT sandwich structure was obtained in the present study. It is found that dense PLCT layer can both sustain the porous density in the core layer and also lead to better preferential orientation of the sandwich structure. In the sandwich structure, low dielectric constant (ε_r = 43) and leakage current density (J < 9 × 10^− 5A/cm²) are simultaneously achieved. Because of high orientation in sandwich structure, the pyrocoefficient (p > 185 µC/m² K) is still keeping a relatively large value. The resulting high figure of merit (F_V′ = 4.5 µC/m² K, F_d′ = 228 µC/m² K) make the sandwich structure films good candidate for pyroelectric thin-film devices.