A high efficiency input/output magnetically coupled interleaved buck–boost converter with low internal oscillation for fuel-cell applications: Small signal modeling and dynamic analysis

Dynamic behavior of DC–DC converters plays a crucial role in stability of renewable energy exploitation systems. This paper presents small signal modeling of an input/output magnetically coupled interleaved buck–boost converter for fuel-cell applications to help the designers with the better understanding of converter dynamics. Aiming to have a continuous converter transfer function for a smooth transition between the operation modes and an improved inner dynamics, a damping network and an input/output coupling have been added to the interleaved structure of well-known cascaded buck–boost converter. Having the same step-up/step-down voltage transfer ratio, smooth transition and improved inner dynamics make this converter quite suitable for renewable energy applications. The paper presents a small signal ac equivalent circuit model of the proposed converter based on state space averaging (SSA) method. Simulation results show remarkable improvements in converter dynamic behavior in both time and frequency domains. Prototype setup of 360 W and 36 V output voltage for a fuel cell with a brand of “FCgen 1020ACS” Ballard Power Systems, Inc. was implemented. Experimental results are presented to verify the theoretical model and its expected merits.     

Condition assessment for automatic tool changer based on sparsity-enabled signal decomposition method

Automatic tool changer (ATC) is one of the key basic parts in CNC machining centers, and the globoidal indexing cam and the groove cam are the functional units for tool changing. Thus the condition monitoring is important for highly efficient and precision machining. In this paper, a condition monitoring system is constructed for the ATC, especially for the globoidal indexing cam, including vibration signal acquisition, fault feature extraction and localization, and condition assessment. In the constructed system, sparsity-enabled signal decomposition method is introduced to extract transient component and reduce noises in the complex vibration signals, and the transient component is always a key feature for fault localization. Simulation study shows that the sparsity-enabled signal decomposition method is effective in transient feature extraction. The experimental application in condition assessment for the ATC demonstrates that the constructed condition monitoring system has the potential to assess the working condition of the ATC in practical application.     

Ultrasonic-vibration-assisted laser annealing of fluorine-doped tin oxide thin films for improving optical and electrical properties: Overlapping rate optimization

An ultrasonic-vibration-assisted laser annealing method was developed to enhance the performance of fluorine-doped tin oxide (FTO) thin films. The influences of ultrasonic vibration, laser scan line overlapping rate (L_OR) and laser spot overlapping rate (S_OR) on surface morphology, FTO layer thickness, RMS roughness, crystal structure and photoelectric properties of the FTO films were investigated. The results indicated that the presence of ultrasonic vibration during laser annealing could significantly enhance the film compactness, and using moderate L_OR and S_OR values resulted in significantly decreased FTO layer thicknesses and RMS roughnesses as well as slightly increased crystallite sizes, thus yielding significantly improved optical transmittance values and slightly enhanced electrical conductivity values. It was found that the optimal L_OR and S_OR values for ultrasonic-vibration-assisted laser annealing of the FTO films were 80% and 90%, respectively. The as-obtained film possessed the best overall photoelectric property with an average transmittance (400–800?nm) of 85.9%, a sheet resistance of 8.7?Ω/sq and a figure of merit of 2.51?×?10^–2 Ω^–1. This work may be of great significance in terms of performance optimization of transparent conducting oxide (TCO) thin films.     

Ultrasonic vibration-assisted laser engineering net shaping of ZrO2-Al2O3 bulk parts: Effects on crack suppression,microstructure, and mechanical properties

Laser additive manufactured zirconia-alumina ceramic (ZrO₂-Al₂O₃) parts demonstrate severe problems resulting from cracking and inhomogeneous material dispersion. To reduce these problems, we propose a novel ultrasonic vibration-assisted laser engineered net shaping (LENS) process for fabrication of bulk ZrO₂-Al₂O₃ parts. Results showed that the initiation of cracks and the crack propagation were suppressed in the parts fabricated by LENS process with ultrasonic vibration. For the parts fabricated without ultrasonic vibration, the sizes of cracks decreased with the increase of laser power. Scanning electron microscope analyses proved that the introduction of ultrasonic vibration was beneficial for grain refinement and uniform material dispersion. Due to the suppressed cracking, refined grains, and homogenized material dispersion, the parts fabricated with ultrasonic vibration demonstrated better mechanical properties (including higher microhardness, higher wear resistance, and better compressive properties), compared with the parts fabricated without ultrasonic vibration.     

障板上矩形薄板在浅水环境中的振动及声辐射解析分析

通过推导得到浅水环境中矩形板声辐射阻抗矩阵的解析表达,进一步结合振动假设模态方法及辐射表面单元辐射器思想求解浅水环境中矩形板的振动响应,分析水深对矩形板模态附加质量的影响,给出矩形板模态附加质量随水深的变化情况,得到波导模态的激发对附加质量的影响,并通过对辐射抗矩阵的特征分析得到附加质量在板上分布的主要模式;进一步结合声辐射模态辐射效率,分析水深变化对矩形板振动响应峰值及远场声辐射的影响,分析结果表明:水深度变化对振动响应峰值及声辐射功率的影响与第1阶声辐射模态的辐射效率随深度的变化具有一致性。     

某轻型载货车储气罐支架振动断裂分析与优化

为了有效解决某轻型载货车储气罐支架的断裂故障,首先基于建立的储气罐支架有限元模型进行振动特性分析,分析结果表明其前三阶固有频率接均处于发动机激励频率范围之外,不会产生共振。其次测试各种道路的时域载荷,测试结果表明其中角度搓板路的激励频率与储气罐支架第一阶固有频率相接近,从而引起共振,不满足振动特性要求。然后对其进行振动强度分析,分析结果表明其应力水平不达标,其最大应力点与开裂处一致。再对其进行振动疲劳寿命预测分析,分析结果表明其疲劳寿命也不达标,其危险点也与失效位置相同。再采用集成平台对储气罐支架的结构进行优化设计,优化之后其模态频率、振动强度和振动疲劳均符合性能要求,并且其重量也有所减轻,总体优化效果较佳。最后整车试验结果表明优化之后储气罐支架的振动大幅度降低,并且没有发生失效。     

基于混沌理论的弧形闸门支臂振动特性

为了研究弧形闸门支臂的振动问题,采用混沌理论对时间序列进行处理,确定延迟时间τ、嵌入维数m进行相空间重构,并计算时间序列的混沌特征值,进而研究弧形闸门在启闭过程中振动的复杂性。以某水电站弧形闸门支臂振动为研究对象,根据支臂振动加速度原型观测资料,分析不同开度的振动情况,发现启门振动的复杂程度高于闭门工况,小开度的振动复杂程度更高,且支臂振动的复杂程度为与面板连接位置最大,与闸墩连接位置最小,中间位置介于前两者之间。为弧形闸门短期振动预测提供了支持。     

严重突出煤层穿层钻孔“钻冲筛运”一体化瓦斯治理技术研究与应用

鹤煤公司八矿地质构造复杂、断层褶曲发育,尤其井田深部断层多,并且煤层透气性低且松软,打钻塌孔、喷孔严重,瓦斯抽放效果不好,给煤炭开采和瓦斯综合治理带来了困难。针对鹤煤公司八矿穿层钻孔瓦斯治理技术措施进行井下现场探索与研究,通过在3205底抽巷经过多次技术方案论证、实践,摸索出一套钻冲筛运一体化整套技术流程,并分析高压水力冲孔瓦斯涌出特征、有效影响半径。通过采用高压水力冲孔、振动筛选、转载装运,提高了水力冲孔效果和效率,改善了工作环境。     

山西沁水盆地3号煤层水平井施工技术探究

近年来,建设单位在山西沁水盆地郑庄区块部署较多的煤层气水平井,目的层为3号、15号煤层气储层,施工中受技术及地层因素的影响,多次出现煤层顶板坍塌、卡钻甚至埋钻事故,严重地影响了钻井效率,造成极大的经济损失。针对施工中存在的技术问题,采用无线随钻仪器双伽马技术来控制施工轨迹沿煤层夹矸钻进的方法来指导施工,通过对仪器电信号数据的充分辨识和利用,基本摸清了煤层赋存形态及结构,控制了施工轨迹;采用多种方法进行通井、遇阻划眼,确保井眼圆滑通畅。取得了快速、安全、高效的施工效果,达到了顺利完井的目的,解决了该区块水平井施工的技术难题,对该区水平井的施工具有指导意义。     

一种振动矢量测量及调整的方法

针对消失模生产中振实设备的振动过程不满足工艺要求的情况下会产生的问题,详细阐述了基于消失模振实、紧实过程的测量方法和评价方法,通过使用该种方法可以得出振动矢量和振幅,进而对振实紧实设备和振动紧实工艺进行调整和优化,杜绝干砂振动紧实过程中的各种问题,保证铸件质量。可以普遍应用在干砂振实设备研发、校检、定期维护等各个过程,可以有效提升设备的工艺符合性,减少模样及铸件不合格品的产生。