Corrosion Mechanism of Alumina-magnesia Dry Materials for Smelting Manganese/chromium Steel in Coreless Medium Frequency Induction Furnaces

Alumina-magnesia dry materials are widely used in induction furnace linings, but they show different kinds of damage when melting different kinds of alloy steel. In this paper, the chemical composition, phase composition, and microstructure of the post-use dry materials for the working liners melting different kinds of steel were evaluated. Furthermore, the corrosion mechanism of the steel on the furnace lining materials was comprehensively analyzed. The findings reveal a significant ability of the Mn element in the molten steel to diffuse and penetrate into the refractories. Mn oxidizes to form MnO at the steel-refractory interface, and then forms a liquid phase with Al_(2)O_(3). The Cr element is dissolved into corundum and spinel of the refractories, resulting in lattice defects and structural damage of the materials. TiO2reacts with Al_(2)O_(3) to form Al_(2)TiO_(5), which plays a crucial role in preventing crack formation and propagation. Part of Ti4+dissolves into magnesia-alumina(MA), densifying the materials. TiO2also slows down the reaction between the Cr element and refractory components, further improving the corrosion resistance of the materials.

Analysis and experiment of cross-section flattening incoreless tube bending

In order to predict the flattening rate of the cross-section accurately during the tube ben- ding, the generation principle, the solution and the influence factor of the cross-section flattening were studied. On the basis of the plane-stress and the assumption that the plastic volume is con- stant, three-dimensionai strain formulas were established in consider of the cross-section flattening. Considering the wail-thickness change, the approximate calculation formulas of short axis flattening rate were deduced, with the outer diameter and the inner diameter as parameters. Because different materials have different cross-section flattening rates, a material correction factor was introduced to modify the formula based on experiments. Finally, the validity of the theoretical formulas was proved according to the calculation and the experiment results, which can provide a reference for the forming quality prediction in tube bending.

Investigation on Static Characteristics of an Axial-Flux Permanent Magnet Machine with Coreless Stator

The static characteristics of an axial-flux permanentmagnet( AFPM) machine with coreless stator were investigated.Two-dimensional analytical method for prediction of the no-load magnetic field in the AFPM machine with coreless stator was derived. Electromotive force( EMF) and axial attraction force were deduced from the analytical method. These values obtained from analytical method were compared with those from finite element method( FEM) and agree well. Finally,a prototype was built for experimental validation and back EMF was measured. The results confirmed the validity of the proposed analytical method.

Multimode Interference Refractive Index Sensor Based on Coreless Fiber

A multimode interference refractive index （KI） sensor based on the coreless fiber was numerically and experimentally demonstrated. Two identical single mode fibers （SMF） are spliced at both ends of a section of the coreless fiber which can he considered as the equivalent weakly guiding multimode fiber （MMF） with a step-index profile when the surrounding refractive index （SKI） is lower than that of the coreless fiber. Thus, it becomes the conventional single-mode multimode single-mode （SMS） fiber structure but with a larger core size. The output spectra will shift along with the changes in the SKI owing to the direct exposure of the coreless fiber. The output spectra under different SKIs were numerically studied, as well as the sensitivities with different lengths and diameters of the coreless fiber. The predication and calculation showed the good agreement with the experimental results. The proposed RI sensor proved to be feasible by verification experiments, and the relative error was merely 0.1% which occupied preferable sensing performance and practicability.

Atomically precise coreless AuCu bimetallic nanoclusters for Ullmann C-O coupling

Bimetallic nanocluster with atomic precision has gained widespread attention due to its unique synergism.The coreless Au_(4)Cu_(5)bimetallic nanoclusters were selected as models to explore the relationship between their microstructure and performance,and compare with the coreless monometallic nanoclusters,core–shell nanoclusters,and single atom catalyst(SAC).The experimental results show that the coreless bimetallic nanocluster catalyst Au_(4)Cu_(5)/activated carbon(AC)exhibits high activity and stability in the Ullmann C–O coupling reaction,much higher than coreless monometallic nanoclusters(Au_(11)/AC and Cu_(11)/AC),core–shell nanoclusters(Au_(25)/AC,Cu_(25)/AC,and Au_(1)Cu_(24)/AC),and single atom catalysts(Au SAC and Cu SAC).Moreover,the coreless Au_(4)Cu_(5)/AC catalyst efficiently catalyzed the Ullmann C–O coupling of benzyl alcohol for the first time.This structure–activity relationship was successfully extended to other coreless bimetallic systems,such as Au_(4)Cu_(4)/AC nanocluster,and it is expected to provide new insights for the design of bimetallic catalysts with well-defined performance.

采用改进遗传算法优化LS-SVM逆系统的外转子无铁心无轴承永磁同步发电机解耦控制

为了实现外转子无铁心无轴承永磁同步发电机(outer rotor coreless bearingless permanent magnet synchronous generator,ORC-BPMSG)的精确控制,提出一种基于改进遗传算法(improved genetic algorithm,IGA)优化最小二乘支持向量机(least square support vector machine,LS-SVM)逆系统的解耦控制策略。首先,基于ORC-BPMSG的结构及工作原理,推导其数学模型,并分析其可逆性。其次,建立LS-SVM回归方程,并采用IGA优化LS-SVM的性能参数,从而训练得到逆系统。然后,将逆系统与原系统串接,形成伪线性系统,实现了ORC-BPMSG的线性化和解耦。最后,将提出的控制方法与传统LS-SVM逆系统控制方法进行对比仿真和实验。仿真和实验结果表明:所提出的控制策略可以较好地实现ORC-BPMSG输出电压和悬浮力、以及悬浮力之间的解耦控制。

基于相位差的轴向磁通无铁心电机早期轻微匝间短路故障诊断

针对轴向磁通定子无铁心电机早期匝间短路故障问题,提出一种基于零序分量和定子电流分量相位差的轴向磁通定子无铁心电机的早期匝间短路故障诊断和定位方法。首先,根据定子绕组电感极小的特点建立了匝间短路故障数学模型;其次,对故障前后的短路电流、相电流、零序分量等进行了傅里叶分析,通过零序电压基波幅值变化对匝间短路故障进行识别;最后,通过对比零序电压基波与定子三相电流初相位差来进行故障相定位。结果表明,匝间短路故障相的相电流基波初始相位与零序电压基波初相位差的绝对值近似180°,而健康相的相位差与180°相差较大。基于相位差可以实现轴向磁通无铁心电机早期匝间短路故障的诊断与定位,为永磁电机的匝间短路故障诊断提供了参考。

基于量子力学的PT对称无铁芯变压器机理提出及研究进展

正如光纤替代铜线成为信息传输媒介,这一变革引领了互联网的出现,改变了世界。无铁芯变压器(coreless transformer,CLT)若能替代有铁芯变压器,必将改变电能的传输技术甚至方式,引发能源领域新的一场技术变革。文中在世界上首次基于量子力学理论的宇称时间对称原理(parity-time symmetry,PT对称)实现了高效、高性能的CLT。文中首先论述CLT的研究现状及基于PT对称原理提出PT对称CLT思想的来源;进而,介绍所提出的SS型和SP型PT对称CLT的机理和工作特性,并与有铁芯变压器进行对比;然后,介绍所推广出的两种广义PT对称CLT;最后,总结PT对称CLT的优势及尚需解决的问题。文中的研究表明,PT对称CLT不仅可以达到有铁芯变压器相同的运行特性,且可以实现单位功率因数运行,有望将在中、小功率的高频电能变换中首先得到应用。

轴向磁通定子无铁心发电机磁场解析及转子优化设计

定子无铁心轴向永磁发电机(CAFPMSM)具有结构简单、启动转矩低、功率密度高等优点,在小型风力发电机、汽油发电机等场合具有潜在应用前景。但CAFPMSM的转子磁场呈现典型的三维特性,其对无铁心绕组损耗的影响有别于传统电机。基于对电机转子磁场等效磁路的解析结果,以优化电机输出电压畸变率、降低电机绕组损耗为目的,通过加入导磁极的方式,对电机的转子结构进行优化设计。首先建立新型结构电机磁路等效模型,计算各磁路磁阻以及漏磁系数,然后利用有限元软件,验证理论解析的准确性,最后设计制造试验样机,并对其进行反电动势以及绕组涡流损耗测试。试验结果表明,新型结构电机反电动势波形畸变率、绕组产生的涡流损耗及绕组温升均有所降低。

纤维缠绕建造技术的研究与展望

纤维缠绕建造技术是一种以无芯纤维缠绕技术为基础,采用自主建造机器人来实现大尺寸纤维缠绕结构及其构件的快速、准确和自动化建造的新型技术。本文针对纤维缠绕技术具有扩展到大尺寸建筑及其构件建造的潜力,首先重点介绍了纤维缠绕技术的基本原理、材料系统、机械设备和关键技术,其次梳理和归纳了这一新型建造技术在建筑施工领域中的应用,最后进一步探索和展望纤维缠绕建造技术的未来发展方向。

一种基于自由衰减振荡的固定占空比控制的无铁芯变压器

针对基于无铁芯变压器的DC-DC变换器工作频率过高的问题,提出了一种基于自由衰减振荡的无铁芯变压器的DC-DC变换器。首先,建立无激励源的串联型-串联型拓扑电路理论模型,讨论特征根的演化过程,分析系统自由衰减振荡的运动行为。其次,设计基于自由衰减振荡无铁芯变压器的DC-DC变换器。实验结果表明,该变换器的开关频率可明显低于无铁芯变压器的工作频率,且其输出功率与无铁芯变压器的工作频率可被自由衰减振荡系统的特征根所描述。最后,构建一个实验样机,该样机采用固定占空比控制,当无铁芯变压器的工作频率为206 kHz、开关频率为103 kHz和69 kHz时,变换器的最高整机效率为91.2%,变压器效率在任何工况下均高于96%。

人工血泵用空心杯电机设计

为了改善目前血泵用电机存在的稳定性差、效率低等问题,课题组设计了一种电枢直径为4.8 mm,转速为35000 r/min的血泵用空心杯微电机。结构上采用空心杯结构,以避免齿槽效应、减小涡流效应;基于ANSYS Maxwell有限元分析软件,采用RMxprt模块对空心杯电机进行了结构设计和性能分析,采用Maxwell3D模块建立了空心杯电机的三维有限元仿真模型,在此基础上通过静态磁场、空载和额定负载下的仿真,获得了空心杯电机工作状态下的电磁数据,并对该空心杯电机的电磁设计性能进行了分析。结果表明:实验所设计血泵用空心杯电机结构设计合理,电磁性能良好,空心杯电机效率约为79%。该研究为血泵用空心杯电机的设计与优化提供了参考。

砂岩型铀矿随钻井斜-γ测井系统研制

砂岩型铀矿无岩心钻探过程中,为了实时监测井身质量、提升铀矿勘查效率,本研究研制一种适应于砂岩型铀矿无岩心钻探的随钻井斜-γ测井系统,实现钻进过程中井斜和γ数据的实时、准确测量。本研究开发一种集成高精度三轴数字重力加速度传感器的井斜测量模块,并采用基于十二位置算法的校准软件优化井斜测量数据。同时,针对井下钻孔的尺寸限制,研制一种基于小体积光电倍增管和NaI探测晶体的随钻γ探测器。为确保数据实时传输及处理,研制具有泥浆脉冲信号高速接收功能的司钻控制器以及无线数据通讯功能的上位机软件。研制完成的随钻井斜-γ测井系统探管直径38.15 mm,耐压50 MPa,工作温度-20至85℃。经检定测试,该系统的倾角测量范围介于0~90°之间,精度达到±0.12°;γ测量范围介于0~10930×10^(-6)eU之间,铀含量测量最大相对误差3.1%。在通辽钱家店铀矿床地区开展随钻测井以及电缆测井试验,随钻井斜-γ测井系统探测的矿段γ异常位置与电缆测井结果保持一致。开发的随钻井斜-γ测井系统满足砂岩型铀矿无岩心钻探的需求,为无岩心勘探技术领域提供设备和技术支撑。

空心杯电机非对称同心式绕组成型工艺技术研究

空心杯电机与传统齿槽电机相比具有输出功率密度大、体积小、重量轻、运行平稳、响应快速等特点,其应用越来越广泛。空心杯电机杯型绕组成型工艺是空心杯电机制造中的关键,杯型绕组加工质量直接影响电机的性能。本文提出了一种空心杯电机非对称同心式杯型绕组的成型工艺技术,对非对称同心式绕组的结构及杯型绕组成型工艺进行分析,通过具体产品的生产验证了该工艺方法的可行性及有效性。

UFS产品断路的失效分析及改善

通用闪存存储(UFS)产品具备了高性能、大容量、低能耗、可靠性和兼容性等特点,因此UFS产品内部各层互连要求极高,在生产过程中极易发生断路问题。本文主要深入研究UFS产品的整个结构以及断路异常问题,分析产品内部的承接基板发生裂纹的主要影响因素,并且通过DOE测试改善由基板发生裂纹所导致UFS产品断路的异常,最终基于测试结果为后续UFS产品的生产可靠性和安全性提供方向和建议。

封装基板技术在微电子产品中的应用

阐述封装基板的特点,刚性基板和柔性基板在材料、性能方面的区别,并选取FCBGA基板、无芯基板以及埋嵌芯片技术作为分析对象,详细分析封装基板技术在微电子产品中的实际应用。

基于Halbach阵列盘式无铁心永磁同步电机优化设计——楔形气隙结构电机

从优化结构角度出发,提出基于Halbach阵列楔形气隙盘式无铁心永磁同步电机,该类电机具有效率高、重量轻、噪声低、结构简单等优点,通过改变气隙结构以进一步提高盘式无铁心永磁同步电机的气隙磁密,达到提高电机性能的目的。利用FEM方法对16极盘式永磁同步电机进行建模,选取不同的空气罩尺寸来分析比较,确定适合的求解域,进而对均匀气隙与楔形气隙两种结构进行了静态气隙磁场分析比较。实验结果表明,样机出力由均匀气隙结构200W提高至楔形气隙结构的250W,效率由91.8%升高到92.4%,功率因数由0.985提高到0.993,优化设计达到了目的。

空心线圈电感的计算与实验分析

介绍了体内微机电系统空心线圈电感的计算,主要对非同轴的线圈互感计算进行详细研究,分析了初次级线圈主要几何参数如轴向和径向距离、夹角、线圈半径等对互感的影响.计算结果表明:轴向距离和径向距离增大,互感均减小,但轴向距离对互感的影响要大得多;夹角越大,互感减小,夹角为90°时,互感几乎为0;当线圈半径变化时,互感有个最大值.同时给出一种三轴移动测试平台,可以快捷精确地调节线圈间的轴向径向距离和夹角,在此基础上建立了互感测试系统,测试结果与计算值是相符合的.

定子无铁心轴向磁场永磁电机的解析设计

对定子无铁心轴向磁场永磁电机而言,最准确的设计方法是三维有限元法,但该方法异常耗时。为解决这一问题,本文提出一种解析设计方法。首先推导出了定子无铁心轴向磁场永磁电机的空载磁场三维解析模型。在此基础上,使用绕组函数法推导出电机的反电动势波形解析式,根据绕组端部长度估算值等参数计算出电感、电阻,分析了电机的各项损耗并给出其各自的计算公式;然后根据电机等效电路推导了其稳态性能的表达式;最终使用该设计方法设计了三种不同功率级别、不同绕组形式的样机。样机试验测量结果与计算值相吻合,验证了设计方法的正确性。

基于DSP的盘式无铁心永磁同步电动机调速系统

高磁能积永磁体的出现使盘式永磁电机的定、转子可以设计成无铁心结构,减少了在同等输出功率和轴转矩条件下电机的重量,避免了铁心损耗且减少了转矩脉动。结合这些特性,设计了基于DSP的盘式无铁心永磁电机调速驱动系统。该系统以TMS320LF2407为控制核心,EXB841作为功率驱动单元,整个系统结构紧凑,集成度好。采用空间矢量脉宽调制(SVPWM)方法,有效抑制了电流谐波分量和转矩脉动。实验表明,系统稳态转速平稳且无静差;超调量小;能够获得最大启动转矩,响应快,转速上升时间仅为30ms,具有令人满意的调速性能。