基于贝叶斯因子分析模型的激光回波信号增强方法

激光回波易被噪声污染,被干扰或遮挡时会出现数据缺失.针对该问题,提出一种基于贝叶斯因子分析(Bayesian fac-tor analysis,BFA)模型的激光回波信号增强算法.首先利用因子分析(factor analysis,FA)模型对激光回波进行建模,从而将信号增强问题转换为对模型参数的求解问题;然后将自动相关...     

磁性随机存储器的发展及其缓存应用

随着半导体工艺的进步,晶体管尺寸不断缩小,阈值电压随之下降,传统静态随机存储器的静态功耗逐渐成为系统的瓶颈.而新兴的磁性随机存储器由于具有密度高、极低的漏电流、非易失等特性,成为了后摩尔时代解决静态功耗作为工作存储器的有力竞争者.基于此,本文介绍了MRAM的特性,调研了近三年的MRAM芯片研究成果,重点阐述了MRAM应...     

三级离心式混输泵气液两相增压特性实验研究

本文对三级离心式混输泵在单相水和空气-水两相条件下的增压特性进行实验研究.单相水条件下,增压特性与设计值相符.气体的掺混导致混输泵增压能力表现不同阶段的变化.三种转速下(3500,4000,4500 r·min-1),保持气相流量恒定,随液相流量降低,两相增压逐渐偏离单相.液相流量恒定,随入口含气率升高,两相增压依次划...     

金丝引线键合失效的主要因素分析

通过对金丝引线键合工艺失效模式的研究,分析影响金丝引线键合失效的各种因素,并提出相应的解决措施.为金丝引线键合的实际操作和理论学习提供技术指导,从而更好的降低键合器件的失效率、提高键合产品的成品率和键合效率.     

多关节机械手在晶圆减薄机中的应用

从机械手工艺应用、结构设计、电气控制、推广应用等几方面介绍了多关节机械手在晶圆减薄机中的应用。晶圆减薄机作为封装领域的重要设备,它的开发和应用,对我国封装产业的发展具有重大意义。多关节机械手是全自动晶圆减薄设备晶圆传输的核心部件,直接体现了设备的自动化程度。     

Prediction of Gas-Liquid Pressurization Performances of Multistage Multiphase Pumps Based on Similarity Laws and Neural Networks北大核心CSCD

It is very important to accurately predict the gas-liquid pressurization performance of multiphase pumps for the economy and safety of oil-gas production. Existent prediction models and methods are limited by narrow parameter ranges and low pump stages. A gas-liquid experimental platform at the industrial level was built, and the gas-liquid pressurization performances of a 25-stage centrifugal multiphase pump were obtained. A prediction method for gas-liquid pressurization performances was proposed for multiphase pumps with high stages at variable rotational speeds. Firstly, the artificial neural network of gas-liquid boosting pressure in the pump with low stages at a constant rotational speed, was constructed. Then, the boosting pressures at variable rotational speeds were converted to the designed condition by the 2-phase similarity law. Finally, based on the isothermal compression hypothesis, the inter-stage flow parameters were updated and the boosting pressures in pumps with high stages were acquired. The relative errors of prediction results of gas-liquid pressurization were less than 15% in pumps with different stage numbers (3~25 stages) and rotational speeds (2 500~3 500 r·min-1). The proposed method can be applied to other types of multiphase pumps, to determine the stage numbers of multiphase pumps and make production evaluation in oil-gas industry. © 2023 Editorial Office of Applied Mathematics and Mechanics. All rights reserved.     

LY12CZ激光熔覆的疲劳性能

通过有效控制固体YAG脉冲式激光器的电流、脉冲宽度、频率、光斑直径、扫描速度等有关工艺参数,模拟飞机腐蚀损伤的铝合金试样表面激光熔覆Al-Y(Y的质量分数为4%)合金,Al-Si(Si的质量分数为12%)合金,充分时效后进行疲劳实验、疲劳断口分析和金相分析。结果表明,熔覆Al-Y合金试样的安全寿命达到熔覆Al-Si合金试样寿命的339%,熔覆层和基体结合得比较紧密,熔覆层气孔、夹杂等缺陷较少,疲劳断口裂纹扩展区存在疲劳条带和疲劳台阶,熔覆Al-Si合金试样的熔覆层气孔缺陷较多,没有呈现低周疲劳的特征。     

气相色谱法测定牡蛎中多溴联苯醚

利用气相色谱-电子捕获检测器(GC-ECD),建立了牡蛎中11种多溴联苯醚(PBDEs)同时测定方法。优化了气相法与质谱联用法仪器条件,考察了不同提取溶液、固相萃取柱、净化方式等前处理条件对提取和净化效果的影响。结果表明,GC-ECD对高溴组分更灵敏;牡蛎加标样品经正己烷-二氯甲烷(1:1,V/V)提取,弗洛里硅土柱-浓硫酸净化,GC-ECD测定,PBDEs各组分标准曲线线性良好(r 0. 998),二至九溴联苯醚和十溴联苯醚方法检出限分别为0. 05 ng/g和0. 1 ng/g,回收率范围为80. 3%～104%,相对标准偏差范围为3. 0%～12%。方法可用于牡蛎中二至十溴联苯醚同时检测。