Reaction Engineering Approach (REA) to model the drying kinetics of droplets with different initial sizes—experiments and analyses

Droplets with different initial sizes, which are typical in conventional liquid atomization for spray drying applications, will result in varying drying and crust formation histories. It is essential for any droplet drying model to accurately capture such fundamental phenomena. This study used a newly constructed glass-filament single droplet rig to evaluate the applicability of the Reaction Engineering Approach (REA) in describing such effect. For the three initial sizes (1, 2 and 3 μL) tested, the glass filament gravimetric method clearly distinguished the different drying kinetics and the crust formation phenomenon, delineated by the drying behavior. Analysis from the drying kinetics revealed that the main premise of the REA, which utilizes a material-specific master activation energy curve, is applicable to droplets of different initial sizes at all the three air temperatures tested. This allowed the REA to accurately predict the different temperature and moisture histories given by droplets with different initial sizes. The result supports the REA as a good modeling approach for a wide range of initial droplet conditions. A new master curve approach was proposed to predict the diameter change of droplets with different initial concentrations. Validation with the current and past experimental data revealed that this approach has strong potential to account for the different feed concentrations typically found in spray drying applications.     

新立地区嫩三段储层非均质性及其影响因素分析

针对新立地区嫩三段各层位储层岩石学、物性、非均质性、微观孔隙结构等特征认识不清的问题,综 合运用岩心薄片、扫描电镜、压汞曲线及测井等资料,对该区储层宏观非均质性（平面、层内、层间）和微观 非均质性（孔隙）进行了研究。结果表明,新立地区嫩三段储层呈现强非均质性特点。同时,分析了该区储 层非均质性的影响因素,认为沉积微相从根本上控制了储层非均质性的形成,而成岩作用引起的一系列 变化则使储层非均质性增强。     

带自适应斜坡补偿的COT控制Buck变换器

提出了一种采用自适应斜坡补偿(ARC)的恒定导通时间控制Buck变换器。引入了两个斜坡电压,实现对电感电流下降斜率的检测;通过负反馈环路调节斜坡斜率,使斜坡斜率跟随电感电流下降斜率的变化。最终斜坡补偿带来的额外极点被固定下来,以便于补偿设计。在此基础上,引入瞬态增强电路,提高了负载阶跃响应速度。在5 V输出电压下,负载从3 A到100 mA阶跃时,输出上冲电压减小了150 mV,恢复时间缩短了10 μs。负载从100 mA到3 A阶跃时,输出下冲电压减小了130 mV,恢复时间缩短了12 μs。     

A person re-identification algorithm based on pyramid color topology feature

Multimedia Tools and Applications - Due to illumination variations, person re-identification algorithms based on color features are not robust in practical applications. Different persons may have...     

多比特数字信号频率测量方法

文中提出一种可直接测量多比特数字信号频率的方法，叙述了基本原理及实施方法。此方法的特点是实施简单，成本低廉、精度高。当信号频率较高且量化的比特数较多时，上述优越性别明显。     

数字式自动衰减器设计

文中介绍以数控衰减器ＡＤ７１１８为核心配以衰减控制码电路组成数字式自动衰减器的设计。自动衰减器量根据输入信号电平高低自动调节并具有衰减分贝值的数字显示及数字输出。     

基于Curve Fitting Toolbox反应器停留时间分布的确定

反应器停留时间分布的确定是建立反应器流动模型的基础。本文介绍了用MATLAB的Curve Fitting Toolbox计算反应器停留时间分布的方法。通过在图形界面下导入数据及平滑处理、采用平滑样条拟合数据以及数值积分等操作,确定了反应器停留时间分布的特征值,并且以确定系数R~2、误差平方和以及均方根误差评价拟合模型的精确度。研究表明:计算结果与文献相吻合。该法运行可靠,无需编程、易于掌握。与传统计算方法相比,操作更为便捷,强有力的图形界面也使计算变得更加简单而直观。     

基于卡尔曼预测的差动共焦轮廓跟踪测量方法

针对轴向扫描式差动共焦测量法(ASDCM)测量轮廓效率低下问题,提出一种基于卡尔曼预测的差动共焦轮廓跟踪测量方法。该方法使用激光差动共焦轴向响应曲线数百纳米量程的线性区间实现了表面连续轮廓高精度线性传感测量,提高了测量效率;同时引入基于卡尔曼预测器的轮廓跟踪原理利用已测轮廓点数据对未测表面预测并跟踪,扩展了线性传感轮廓测量法测量范围。实验结果表明,该方法相对于ASDCM法测量效率提升了8倍,且实现了轮廓PV值大于线性传感测量范围的标准椭圆柱高精度跟踪测量,激光聚变靶丸内轮廓圆度重复测量标准差达3 nm。为精密元器件表面连续轮廓的高精度、快速、无损测量提供了一种高质量方法。     

三元乙丙橡胶J-4090和6950C的结构与性能研究

研究2种应用于汽车海绵密封条的牌号为J-4090和6950C的三元乙丙橡胶（EPDM）的微观结构及其复合材料（包括密实胶和发泡胶）的性能。结果表明：与EPDM 6950C相比,EPDM J-4090的乙烯基质量分数较大,第三单体（亚乙基降冰片烯）质量分数较小,相对分子质量分布较宽;与EPDM 6950C密实胶相比,EPDM J-4090密实胶的硫化速率和交联密度较小,抵抗变形的能力较差,硫化体系用量增大20%的EPDM J-4090密实胶的物理性能达到EPDM 6950C密实胶一致的水平。与EPDM 6950C发泡胶相比,硫化体系用量增大20%的EPDM J-4090发泡胶的挤出胀大比略大,发泡特性和物理性能相近。     

Advance in the Polymerization Strategy for the Synthesis of β-Peptides and β-Peptoids

Peptide mimics, possessing excellent biocompatibility and protease stability, have attracted broad attention and research in the biomedical field. β-Peptides and β-peptoids, as two types of vital peptide mimics, have demonstrated great potential in the field of foldamers, antimicrobials and protein binding, etc. Currently, the main synthetic strategies for β-peptides and β-peptoids include solid-phase synthesis and polymerization. Among them, polymerization in one-pot can minimize the repeated separation and purification used in solid-phase synthesis, and has the advantages of high efficiency and low cost, and can synthesize β-peptides and β-peptoids with high molecular weight. This review summarizes the polymerization methods for β-peptides and β-peptoids. Moreover, future developments of the polymerization method for the synthesis of β-peptides and β-peptoids will be discussed.