Dipping Process Characteristics Based on Image Processing of Pictures Captured by High-speed Cameras

The dipping process was recorded firstly by high-speed camera system; acceleration time, speed, and dipping time were set by the control system of dipping bed, respectively. By image processing of dipping process based on Otsu's method, it was found that low-viscosity flux glue eliminates the micelle effectively, very low speed also leads to small micelle hidden between the bumps, and this small micelle and hidden phenomenon disappeared when the speed is ≥0.2 cm s-1. Dipping flux quantity of the bump decreases by about 100 square pixels when flux viscosity is reduced from4,500 to 3,500 mpa s. For the 3,500 mpa s viscosity glue, dipping flux quantity increases with the increase of the speed and decreases with the increase of the speed after the speed is up to 0.8 cm s-1. The stable time of dipping glue can be obtained by real-time curve of dipping flux quantity and is only 80–90 ms when dipping speed is from 1.6 to 4.0 cm s-1. Dipping flux quantity has an increasing trend for acceleration time and has a decreasing trend for acceleration. Dipping flux quantity increases with the increase of dipping time, and is becoming saturated when the time is ≥55 ms.

Influence of tool rotational speed on microstructure and sliding wear behavior of Cu/B_4C surface composite synthesized by friction stir processing

An attempt was made to synthesize Cu/B4C surface composite using friction stir processing（FSP） and to analyze the influence of tool rotational speed on microstructure and sliding wear behavior of the composite. The tool rotational speed was varied from 800 to 1200 r/min in step of 200 r/min. The traverse speed, axial force, groove width and tool pin profile were kept constant. Optical microscopy and scanning electron microscopy were used to study the microstructure of the fabricated surface composites. The sliding wear behavior was evaluated using a pin-on-disc apparatus. The results indicate that the tool rotational speed significantly influences the area of the surface composite and the distribution of B4C particles. Higher rotational speed exhibits homogenous distribution of B4C particles, while lower rotational speed causes poor distribution of B4C particles in the surface composite. The effects of tool rotational speed on the grain size, microhardness, wear rate, worn surface and wear debris were reported.

Influence of multipass high rotating speed friction stir processing on microstructure evolution,corrosion behavior and mechanical properties of stirred zone on AZ31 alloy

The influence of multipass high rotating speed friction stir processing(FSP)on the microstructure evolution,corrosion behavior,and tensile properties of the stirred zone(SZ)was investigated by EBSD,TEM,SEM,electrochemical workstation and electronic universal testing machine.The mean grain size of the SZ is significantly refined,and it increases with the increase of the processing pass.In addition to an obvious increase in the number,the distribution ofβ-Al12Mg17 precipitates also becomes more uniform and dispersed with increasing the processing pass.Compared with the as-received AZ31 alloy,the tensile properties of the SZ are hardly improved,but the corrosion resistances are significantly enhanced.The corrosion potential of the SZ prepared by 4-pass FSP is increased from−1.56 V for the unprocessed AZ31 alloy to−1.19 V,while the corrosion current is decreased from 1.55×10^−4 to 5.47×10^−5 A.

A Recursive Method of Time-Frequency Analysis for the Signal Processing of Flutter Test with Progression Variable Speed

Focused on the non-statlonarity and real-time analysis of signal in flutter test with progression variable speed （FTPVS）, a new method of recursive time-frequency analysis is presented. The time-varying system is tracked on-line by building a time-varying parameter model, and then the relevant parameter spectrum can be obtained. The feasibility and advantages of the method are examined by digital simulation. The results of FTPVS at low-speed wind-tunnel promise the engineering application perspective of the method.

Evaluating Traffic Congestion Using the Traffic Occupancy and Speed Distribution Relationship: An Application of Bayesian Dirichlet Process Mixtures of Generalized Linear Model

Accurate classification and prediction of future traffic conditions are essential for developing effective strategies for congestion mitigation on the highway systems. Speed distribution is one of the traffic stream parameters, which has been used to quantify the traffic conditions. Previous studies have shown that multi-modal probability distribution of speeds gives excellent results when simultaneously evaluating congested and free-flow traffic conditions. However, most of these previous analytical studies do not incorporate the influencing factors in characterizing these conditions. This study evaluates the impact of traffic occupancy on the multi-state speed distribution using the Bayesian Dirichlet Process Mixtures of Generalized Linear Models (DPM-GLM). Further, the study estimates the speed cut-point values of traffic states, which separate them into homogeneous groups using Bayesian change-point detection (BCD) technique. The study used 2015 archived one-year traffic data collected on Florida’s Interstate 295 freeway corridor. Information criteria results revealed three traffic states, which were identified as free-flow, transitional flow condition (congestion onset/offset), and the congested condition. The findings of the DPM-GLM indicated that in all estimated states, the traffic speed decreases when traffic occupancy increases. Comparison of the influence of traffic occupancy between traffic states showed that traffic occupancy has more impact on the free-flow and the congested state than on the transitional flow condition. With respect to estimating the threshold speed value, the results of the BCD model revealed promising findings in characterizing levels of traffic congestion.

A beam position measurement system of fully digital signal processing at SSRF

This fully digital beam position measurement instrument is designed for beam position monitoring and machine research in Shanghai Synchrotron Radiation Facility. The signals received from four position-sensitive detectors are narrow pulses with a repetition rate up to 499.654 MHz and a pulse width of around 100 ps, and their dynamic range could vary over more than 40 dB in machine research. By the employment of the under-sampling technique based on high-speed high-resolution A/D conversion, all the processing procedure is performed fully by the digital signal processing algorithms integrated in one single Field Programmable Gate Array. This system functions well in the laboratory and commissioning tests, demonstrating a position resolution (at the turn by turn rate of 694 kHz) better than 7 μm over the input amplitude range of -40 dBm to 10 dBm which is well beyond the requirement.

Managing Complexity and Speed of Processes in the Organizations—A Philosophical and Practical Approach

The business challenges of today are managing complexity and the speed of changes with processes and systems since there are continuously new requirements from market, consumers, suppliers, employees, government etc. For example, when product and service innovations are launched on the market, the relevant processes, policies, people, systems, and technologies should have been prepared and set up in advance. Depending on the business sector, the implementation of new processes and systems as well as their continuous improvement can be easy to very complex and of course very costly. Responding to those challenges, there are several methodologies and approaches like Continuous Improvement Process, Lean Management and Kaizen etc. On the other hand, the application of these methodologies to other industries like service and technology companies is not always successful since their conditions and requirements are different than those of manufacturing organizations. Because of these reasons, the management needs to find out （new） ways of working and to implement new solutions in order to master those challenges and problems. This is not always easy and successful. There are different types of solution options that can be applied situational in every organization. Philosophy can help essentially by asking and answering critical questions in order to provide with solution options to reduce the complexity and to increase the speed of processes. There are several proven and new governance concepts, frameworks, and tools which follow their philosophies. This paper demonstrates how those challenges can be responded and managed as well as how a philosophical approach can help primarily to provide with appropriate solutions.

STRUCTURE EVOLUTION OF POLYMER CHAINS FOR NECKING FORMATION IN HIGH-SPEED FIBER SPINNING PROCESS

Finite element method is used to simulate the high-speed melt spinning process, based on the equation system proposed by Doufas et al. Calculation predicts a neck-like deformation, as well as the related profiles of velocity, diameter, temperature, chain orientation, and crystallinity in the fiber spinning process. Considering combined effects on the process such as flow-induced crystallization, viscoelasticity, filament cooling, air drag, inertia, surface tension and gravity, the simulated material flow behaviors are consistent with those observed for semi-crystalline polymers under various spinning conditions, The structure change of polymer coils in the necking region described by the evolution of conformation tensor is also investigated. Based on the relaxation mechanism of macromolecules in flow field different types of morphology change of polymer chains before and in the neck are proposed, giving a complete prospect of structure evolution and crystallization of semi-crystalline polymer in the high speed fiber spinning process.

鳝鱼自动剖切机设计与试验

目的:设计一款专门用于剖杀细长且表面光滑的鱼类剖切机构。方法:以表体黏滑的鳝鱼为研究对象,开展夹持与剖切作业机理分析。以剖切质量和剖切时间为试验指标,探究夹轮转速、剖刀转速、夹轮表面几何形状等主要参数对剖切质量和剖切时间的影响规律。结果:影响剖切质量的主要因素为刀片转速和夹持轮限位高度,影响剖切时间的最主要因素为夹轮转速。当夹轮限位高度为5 mm、刀片转速为1 350 r/min、夹轮转速为167 r/min时,可获得较高的剖切质量评分与剖切时间。结论:使用夹持轮可以有效输送鳝鱼,通过调配夹持轮转速、刀片转速和限位高度可以实现高效高速剖腹。

两种直动式高速电磁阀数值模拟与动态响应对比分析

针对直动式高速电磁阀动铁芯与阀芯加工、装配工艺要求高,一致性较差的问题,提出了一种动铁芯与阀芯可分离的结构,基于AMESim平台建立此款电磁阀电–磁–机–气多物理场耦合模型,考虑了动铁芯与阀芯撞击与分离的情况,并在试验台上进行了验证。然后与另一种动铁芯与阀芯“绑定”的结构形式进行比较分析。结果表明:两种电磁阀在动态响应与影响动态响应的关键参数存在差别。在同等条件下,第一种结构形式的电磁阀动态响应整体略差,但是其对动铁芯–阀芯加工、装配工艺的要求较低。

高速铁路多列车客票预分与通售策略协同优化

在客票预分方案中设置通售票能使分配票额有效适应售票过程中动态变化的购票需求,但也容易出现通售票过早肢解,从而导致后续长途OD对旅客购票失败、通售票无法充分利用。为避免此情况出现以进一步提高通售票的利用率,考虑通售票销售策略与铁路客票预分方案的协同优化问题,实现由OD固定票、通售票构成的客票预分方案与通售票发售策略(以下简称“通售策略”)的协同优化。首先,基于旅客随机购票需求描述、旅客购票列车选择分析,构建铁路客票预分方案与通售策略协同优化模型,以客票总收益最大化为目标,考虑列车席位能力、列车服务、客票量上下限以及通售发售策略等约束;其次,在生成多套购票需求样本的基础上,结合旅客出行购票过程的仿真,设计模型求解的粒子群算法。算例结果表明对比不考虑通售策略的客票预分方案,本文优化方法能使列车平均客座率提高4.96%、列车客票总收益提高2.74%,充分验证了引入通售策略能有效实现客票的灵活与充分利用。

战斗部破片光电测速系统设计

战斗部破片的飞行速度是体现其性能指标的重要参数;针对目前在战斗部破片速度参数测试中存在对测试环境要求高,测试面积小,设备结构易被破片误击而损坏,成本昂贵等问题,设计了非接触式战斗部破片光电测速系统,包含原向反射膜、反射式光电探测装置、光电转换电路、信号处理电路及测速装置;阐述了系统结构组成和测速原理,通过反射式光电探测装置与光电转换电路,将得到的光信号转换为电信号,利用集成信号处理电路对电信号滤波放大,比较整形处理,由FPGA,STM32及其他外设组成的测速装置自动处理数据输出并显示战斗部破片的飞行速度结果;实验结果表明:该系统能够可靠,稳定地完成战斗部破片速度的测量任务;与传统测速系统相比,具有不受限于环境,测试区域大,易维护,低成本,操作简单等优势。

泵反转液力透平转速特性研究

为了研究液力透平的转速特性,采用Fluent软件动网格中的SDOF求解器对一台比转速为48的离心泵反转作液力透平进行数值模拟,分析了液力透平在启动过程中转速的变化规律。结果发现:随着转速的增大,透平高效区变宽,高效点明显向大流量偏移。流量越大,透平的飞逸转速就越大,各流量工况下的飞逸转速约为额定转速的1.4倍。在负载系数B_(g)为1.4905时,其负载力矩达到临界值,继续增加负载,叶轮不在工作,此时的水动力矩小于负载力矩。

高速列车车轮两阶段退化建模及可靠性分析

针对高速列车车轮在退化过程中呈现两阶段特征的问题,提出一种基于两阶段非线性Wiener过程的高速列车车轮退化建模及可靠性分析方法。采用CUSUM(CUmulative SUM)算法实现车轮退化过程变点判别,在此基础上,利用马尔可夫链蒙特卡罗方法估计模型未知参数。针对车轮两阶段退化过程较为复杂、可靠度解析形式难以求解的问题,通过蒙特卡罗模拟方法求解得到车轮可靠度函数曲线和可靠寿命。最后以某机车同转向架车轮单个镟修周期内的实测数据为例,验证了模型的有效性。结果表明:受运营环境影响,同转向架不同侧车轮退化过程出现变点的位置不同;相较于未考虑阶段性特征的退化模型,所提模型可靠性评估结果更符合现场实际;通过不断获取车轮退化数据,可采用所提模型计算并更新车轮可靠寿命值,为车轮镟修周期的进一步优化提供了理论指导。

高质量加工五次多项式速度规划算法研究

通过分析直线、指数、S曲线以及正弦函数几种常用的加减速算法,针对传统的速度规划算法存在的加工曲线不连续以及加工过程出现振荡、加工精度低等问题,提出适用于高质量加工的五次多项式速度规划算法,将整个加工过程分段,细化每一段的方程,并介绍对于待定的NURBS曲线使用五次多项式速度规划算法进行插补的过程,针对快速插补和实时插补两个阶段进行优化。结尾根据仿真加工实验图像得出结论,该算法实现了加工过程中运动曲线的连续变化、柔性变化。并将加工精度控制在理想范围之内,适应于高质量的加工。

二轴摩擦型V带传动工作过程分析与带速选择

引入梯形中位线定理,以几何图形和胡克定律对各力之间关系,进行了清晰的阐述。提出了有效拉力释放系数Hα的概念,定义了常规因子K_(1),提供了一种最大有效拉力的计算方法,通过比例系数Xα证明了Hα的适用性和准确性。绘制了综合性能曲线图,探讨了紧边极限拉力F_(1)、松边极限拉力F_(2)、最大有效拉力F_(ec)、最大功率P_(0)等随带速v的变化规律。给出了最大应力与功率曲线图,阐明了最佳带速的选择方法、任意包角α0下最大功率P_(0)的计算方法,定义了安全系数S_(0)。

高速斜撑超越离合器楔合动态响应研究

针对斜撑式超越离合器高速楔合容易产生故障的实际情况,对其楔合动态过程进行研究。工作过程中,斜撑式超越离合器内部楔块之间、楔块与内外环间以及各部件同保持架间存在碰撞。首先基于Hertz接触理论,求解了碰撞刚度,为明确各参数对高速斜撑超越离合器动态响应的影响程度,建立了包括楔合延迟时间、冲击力矩、最大转速差等在内的评价指标。同时,将高速斜撑超越离合器的楔合动态过程进行划分,以研究几何参数对不同响应阶段的影响。最后,开展了楔块与内环的摩擦条件、弹簧力、碰撞刚度、阻尼和负载等对高速斜撑超越离合器楔合动态响应的研究。结果表明,不同参数对所定义的评价指标的影响程度不同,极端情况下可导致楔合失败。该研究可为工程实践提供一定的理论参考和指导。

基于光速变换的激光打孔切割设备设计

传统机械加工存在加工效率低、环境友好性差等缺点,激光加工刚好解决了这些难题。激光切割打孔技术利用激光发生器输出高能量密度的激光束,激光束扫描加工表面,通过局部区域熔化气化,从而快速成型。鉴于此,设计了一款激光打孔切割设备。首先从打孔切割设备的功能与性能需求入手,分析激光打孔切割工艺内容,提出打孔机机械系统方案。根据现代化设计理论原理,借助三维建模软件,完成了X、Y、Z轴的机械结构设计。包括电机的选取、导轨和丝杠的设计算,并完成了寿命以及强度刚度的校核。通过运用PLC控制技术来实现Z轴的移动,确保激光发生器移动至需要加工的位置。根据工艺需求确定了激光发生器的选型,并分析了激光切割速度和功率对加工结果的影响。

基于MEEMD算法的二冲程柴油发动机机体振动分析

二冲程低速柴油机具有复杂的振动特性,传统的经验模态分解(Empirical Mode Decomposition,EMD)算法对其振动信号处理效果不理想。为此,采用修正多元集合经验模态分解(Modified Ensemble Empirical Mode Decomposition,MEEMD)算法对低速柴油机机体振动信号进行分解。首先,采用三轴加速度计测量发动机机体振动。然后利用均方根(Root Mean Square,RMS)对三轴振动强度进行分析。最后,对x轴上的信号进行MEEMD分析。结果表明:砌块在x轴方向的振动强度最大;与EMD算法相比,MEEMD算法可以抑制模态混合,有助于更好地识别块振动激励。

基于KA-SRCN-pSTAP的低空风切变风速估计方法

针对由于独立同分布(IID)样本严重不足,导致极化空时自适应(pSTAP)处理性能下降,进而导致低空风切变风速估计不准确的问题,本文提出了一种基于知识辅助的稀疏表示杂波零陷极化空时自适应(KA-SRCN-pSTAP)的低空风切变风速估计方法。该方法首先利用杂波脊的先验知识辅助构造极化空时稀疏字典,然后利用极化空时稀疏字典,通过SRCN算法挑选原子并对到杂波线性子空间补空间上的投影矩阵进行估计,从而得到pSTAP权矢量,最后构造pSTAP滤波器对地杂波进行抑制,准确估计低空风切变风速。该方法仅使用少量IID样本,将SRCN算法与极化-空时域相结合,完成对风切变风速的有效估计。仿真实验结果证明该方法可以有效实现少样本情况下的风速准确估计。