Spar平台垂荡-纵摇内共振特性研究

考虑变化的排水体积和初稳心高的影响,建立垂荡一纵摇的耦合运动方程,简化的运动方程是非线性的,采用多尺度法得到了耦合运动方程的一阶定常响应解。运用非线性动力学理论,研究了Spar平台发生垂荡主共振时垂荡一纵摇耦合运动的饱和现象、幅值跳跃现象和解的稳定性等问题,并提出了相关的工程建议。     

Rotary inertia and temperature effects on non-linear vibration, steady-state response and stability of an axially moving beam with time-dependent velocity

Free non-linear transverse vibration of an axially moving beam in which rotary inertia and temperature variation effects have been considered, is investigated. The beam is moving with a harmonic velocity about a constant mean velocity. The governing partial-differential equations are derived from the Hamilton's principle and geometrical relations. Under special assumptions, the two partial-differential equations can be mixed to form one integro-partial-differential equation. The multiple scales method is applied to obtain steady-state response. Elimination of secular terms will give us the amplitude of vibration. Additionally, the stability and bifurcation of trivial and non-trivial steady-state responses are analyzed using Routh-Hurwitz criterion. Eventually, numerical examples are presented to show rotary inertia, non-linear term, temperature gradient and mean velocity variation effects on natural frequencies, critical speeds, bifurcation points and stability of trivial and non-trivial solutions.     

Stepwise Optimized 3D Printing of Arbitrary 3D Structures at Millimeter Scale with High Precision Surface

3D printing based on additive manufacturing has attracted widespread attention in the fields of microbiology and microelectronics due to its advantages of waste reduction, arbitrary manufacturing, and rapid prototyping in potential applications. These techniques can create structures at the centimeter scale, however, there are some limitations in terms of resolution and geometric constraints. Here, a micro–nano 3D printing protocol based on additive manufacturing to achieve the 3D structure (3DS) not only possessing millimeter scale structural dimensions but also nanometer features are proposed. A theory is verified to assist the design and fabrication of the 3DS with millimeter scale and nanometer precision. The structures are predesigned and the scanning strategy is optimized before 3D printing to improve the manufacturing efficiency and precision. A customized 3DS with a height of 2.2 mm is obtained, which is a challenge for the conventional two‐photon polymerization fabrication. Furthermore, a 1.2 mm 3DS with inside scaffold and smooth surface is efficiently achieved within 2.7 h with a nanometer surface roughness by using the proposed stepwise optimized 3D printing process. This study offers a flexible and low‐cost technology to generate highly customizable, precisely controllable 3DS for potential applications in microelectronics and microdevices.     

两种油管材料在模拟油田水溶液中的CO2腐蚀行为

    结合某油田现场应用情况,利用高压釜、扫描电镜和X-射线衍射(XRD)等手段,对比研究了N80和GB-N80-3Cr两种材料在模拟油田水环境中腐蚀行为.结果表明,温度对腐蚀速率影响较大,随着温度的增加,腐蚀速率呈增大趋势;温度高于60℃时,N80材料开始出现台地状局部腐蚀,而GB-N80-3Cr在所有测试温度下均未见局部腐蚀出现,且GB-N80-3Cr的腐蚀速率明显低于N80材料.     

HQ460热轧带钢粉状氧化铁皮形成原因及消除措施

利用X光衍射仪对HQ460热轧带钢粉状氧化铁皮进行了检测分析。结果表明,粉状氧化铁皮形成的主要原因是铁皮中FeO含量偏高。生产中通过采取调整化学成分,提高加热温度、除鳞温度和轧制温度,降低卷取温度等措施,最终消除了粉状氧化铁皮这一缺陷。     

基于多尺度理论的三维表面形貌表征研究

首次将多尺度理论应用于三维表面形貌表征,采用不同的观察尺度对原始表面进行最小二乘、Motif法过滤,得到多尺度基面和多尺度表面,并基于WM函数进行图形、粗糙度参数表征研究。研究发现:多尺度理论的应用可以将形状偏差和波纹度视为某相对较大观测尺度下的粗糙度,并成功定量过滤,从而有效地解决传统粗糙度表征中形状偏差和波纹度的影响,提供一种契实可行的用于表征表面形貌和评定表面功能的理论或方法,更加准确地表达三维表面特性与其表面形貌参数的基本关系。     

变惯量曲轴系统扭转振动的参数分岔分析

变惯量参数在一定程度上会影响曲轴系统扭转振动的分岔特性,然而现有研究缺乏对此参数的分岔理论分析。本文针对上述问题展开研究,分析了当曲轴系统的转动频率、不平衡激励频率与固有频率近似满足 的情况下,变惯量参数和调谐参数对系统分岔行为的影响。首先应用多尺度法得到系统共振情况下的平均方程和分岔方程;其次应用奇异性理论得到系统的稳态振幅随参数变化的分岔图,分析并求解系统发生分岔的临界点,得到系统的稳定/分岔区间;最终选取工程实际物理参数,将理论结果与数值仿真进行对比,验证了理论分析的正确性。进行变惯量曲轴系统的参数分岔分析,有助于曲轴系统的优化设计。     

基于ARM7TDMI微处理器的矿用电子皮带秤的设计与实现

简要介绍了ARM7TDMI微处理器的发展过程及矿用电子皮带秤的分类技术,重点分析了计算机ARM7TDMI微处理器系统的特性,探讨了当前典型ARM7TDMI微处理器矿用电子皮带秤以及矿用电子皮带秤的设计和实现。     

改进的AHP算法在Web集群系统负载均衡中的应用

判断矩阵的建立和调整是AHP算法的关键。对Satty的1~9标度方法进行改进,引入3标度法建立判断矩阵。从正互反矩阵充分必要条件出发,提出判断矩阵不一致时的调整方法,以提高判断矩阵的一致性和减少计算量。该方法应用于Web集群系统负载均衡中,确定影响服务器负载的四大类参数的权重。实验表明,改进的AHP算法在判断矩阵不一致时,在尊重原始数据的基础上,调整判断矩阵的计算量减少,判断矩阵的一致性更好,同时可以提高负载均衡系统的性能。