基于场指纹法的金属管道小腐蚀坑的监测方法

FSM即场指纹法,是一种基于电位列阵的金属管道在线腐蚀监测的方法。该方法的核心在于将电极列阵分布在被测管道外部,利用电阻与管道厚度的关系,通过测量电极之间的电压来监测管道内壁的腐蚀情况。但是测量电极间的电压同时受腐蚀坑的面积和深度的影响,而一个电压值无法确定两个未知参数,故存在不可解问题。目前计算腐蚀坑的公式是将面积设定为固定值,由此得出的结果一般表现为坑的面积偏大而深度偏小,这也是当前FSM法最大的缺陷之一。在介绍FSM方法的基础上,针对传统FSM法对于小腐蚀坑的监测存在不可解问题,创新性地提出了一种综合利用主电压和辅电压来准确区分小腐蚀坑的面积和深度的方法。理论分析和实验表明,提出的主辅电压法可以大幅度提高小腐蚀坑的监测精度。

一种基于场指纹法的金属管道小腐蚀坑的求解方法

针对场指纹法(FSM)对小腐蚀坑检测精度偏低的问题,根据小腐蚀坑会对被测管道的电流分布产生影响的现象,提出一种细分的电阻链网络模型,利用主辅电压和细分电阻网络的特定关系来准确求解小腐蚀坑,并且分析发现不同位置、不同深度和不同直径的小腐蚀坑对主辅电压有着特定的影响,进而提出了一种利用主辅电压来准确求解小腐蚀坑的方法。该方法的本质在于引入了多个已知参量,从而可以求解出多参量的小腐蚀坑。理论分析和实验表明,提出的求解小腐蚀坑的方法能够有效提高小腐蚀坑的检测精度,发展并完善了FSM方法。

无平衡电抗器24脉自耦变压整流技术研究

提出了一种利用电压矢量合成的无平衡电抗器24脉自耦变压整流器拓扑结构,自耦变压器每相5个绕组,根据不同绕组之间叠加的电压矢量使4组整流桥在同一时刻只有两个二极管导通,并将电压矢量差值最大的线电压送至输出端,主整流桥与辅整流桥根据不同时区主辅电压矢量的合成依次自然换向,不对称的输出电压矢量构成形式使整流桥可直接并联输出24脉波直流电压.论文推导了自耦变压器的匝比、系统输入电流表达式及输出电压表达式,并通过对网侧电流谐波含量及变压器等效容量的计算分析了系统的性能,最后通过仿真以及实验验证了设计的合理性.

场指纹法管道腐蚀监测系统小腐蚀坑的高精度识别方法

场指纹法(Field Signature Method,FSM)的本质是电位矩阵法。FSM管道腐蚀监测系统将测量电极矩阵布局在钢制管道外壁上,并往管壁中通入恒定电流,利用电极间电压与管壁厚度的对应关系,通过测量极间电压的变化来实时监测管壁腐蚀。FSM系统已经成功应用于国内外的各种油气管道腐蚀监测,在全面腐蚀、局部冲蚀监测方面有很好的精度(±0.5%WT,Wall Thickness,壁厚),但坑蚀监测精度较差(±15%WT)。本文在介绍FSM原理的基础上,提出了小腐蚀坑的定义,分析了小腐蚀坑不可识别问题形成的原因及其影响,并提出了一种解决方法——主辅电压法(Major and Assistant Voltage Method,MAVM)。大量的仿真分析表明,主辅电压法可以大幅提高坑蚀的监测精度,对发展和完善FSM理论和实际应用有较大意义。

Influences of electric-hydraulic chattering on backward extrusion process of 6061 aluminum alloy

The possibility of the electric-hydraulic chattering technology and its application in the cold extrusion were presented.The conventional and electric-hydraulic chattering assisted backward extrusion processes were performed on 6061 aluminum alloy billets at room temperature.The experimental results showed that 5.65% reduction in the extrusion load was attained if the die and ejector were vibrated at a frequency of 100 Hz and amplitude of 0.013 mm in the longitudinal direction.The friction coefficient at the billet and tool system interface determined from the finite element analysis（FEA） decreased from 0.2 without chattering to 0.1 with application of electric-hydraulic chattering.The higher values of instantaneous velocity and direction change of material flow were achieved during the chattering assisted backward extrusion process.The strain distribution of the chattering assisted backward extrusion billet revealed lower maximum strain and smoother strain distribution in comparison with that produced by the conventional extrusion method.

Realizing High Breakdown Voltage SJ-LDMOS on Bulk Silicon Using a Partial n-Buried Layer

A new design concept is proposed to eliminate the substrate-assisted depletion effect that significantly degrades the breakdown voltage （BV） of conventional super junction-LDMOS. The key feature of the new concept is that a partial buried layer is implemented which compensates for the charge interaction between the p-substrate and SJ region,realizing high breakdown voltage and low on-resistance. Numerical simulation results indicate that the proposed device features high breakdown voltage,low on-resistance,and reduced sensitivity to doping imbalance in the pillars. In addition, the proposed device is compatible with smart power technology.

New Lateral Super Junction MOSFETs with n^+-Floating Layer on High-Resistance Substrate

A new super junction LDMOST structure that suppresses the substrate-assisted depletion effect is designed with an n^＋-floating layer embedded in the high-resistance p-type substrate by implanting phosphor or arsenic. This effect results from a charge imbalance between the n-type and p-type pillars when the n-type pillars are depleted by p-type substrate. The high electric field around the drain is reduced by the n^＋-floating layer due to the REBULF effect,which causes the redistribution of the bulk electric field in the drift region,and thus the substrate supports more biases. The new structure features high breakdown voltage, low on-resistance,and charge balance in the drift region.

Development of hydraulic power unit and accumulator charging circuit for electricity generation,storage and distribution

It is the purpose of the present paper to convert hydraulic energy to electric energy and saves both the pressure and electrical energy for re - use during the next system upstroke using two secondary units coupled to induction motor to drive cylinder loads. During upstroke operation, the variable pump/motor （P/M） driven by both electric motor and the second （P/M） works as hydraulic pump and output flow to the cylinders which drive the load. During load deceleration, the cylinders work as pump while the operation of the two secondary units are reversed, the variable （P/M） works as a motor generating a torque with the electric motor to drive the other （P/M） which transforms mechanical energy to hydraulic energy that is saved in the accumulator. When the energy storage capacity of the accumulator is attained as the operation continues, energy storage to the accumulator is thermostatically stopped while the induction motor begins to work as a generator and generates electricity that is stored in the power distribution unit. Simulations were performed using a limited PT2 Block, i.e. 2nd-order transfer function with limitation of slope and signal output to determine suitable velocity of the cylinder which will match high performance and system stability. A mathematical model suited to the simulation of the hydraulic accumulator both in an open-or close-loop system is presented. The quest for improvement of lower energy capacity storage, saving and re-utilization of the conventional accumulator resulting in the short cycle time usage of hydraulic accumulators both in domestic and industrial purposes necessitates this research. The outcome of the research appears to be very efficient for generating fluctuation free electricity, power quality and reliability, energy saving/reutilization and system noise reduction.

Co-simulation and Experimental Study for Wingspan of Flapping Wing Micro Aerial Vehicle

The 3D model of flapping wing mechanism and veins is constructed in 3D computer aided design (CAD) software UG.Then the co-simulation model is established by using multibody dynamics software ADAMS and MATLAB.The validation of this co-simulation model is verified by comparing the simulation results with final experiments.The simulation results and experiments reveal that the relation between flapping frequency and driving voltage of motor is approximately linear under various wingspans.The variance of flapping frequency among different wingspans augments gradually with increasing voltage.Furthermore,the simulation results suggest that flapping frequency is sensitive to wingspan and decreases with increasing wingspan of veins,and the relation between flapping frequency and moment of inertia of veins is also approximately linear for various voltages.

一种内燃机车空调控制逆变电源设计

介绍了一种内燃机车用空调控制逆变电源。该逆变电源将辅发电压转换成三相交流电压提供给空调机组的室内风机、室外风机、压缩机及电加热器工作,同时该电源还具有对空调机组进行起动控制、故障保护控制等功能。分析了空调控制逆变电源的结构及控制方法,提供了相关流程图,并设计了相应的故障检测等辅助电路。