Measuring number‐concentrations of nanoparticles and viruses in liquids on‐line

BACKGROUND: The surge of studies on artificial and natural nanoparticles has revealed a new world for engineering and life sciences, but in most instances, the small scale has made their number‐concentration determination in liquids a challenging problem. Former success has mostly been limited to special particles measured by indirect techniques. A new approach is required for this determination to facilitate the production and application of nanoparticles in different systems. RESULT: Here, an approach is described using a nanoparticle tracking system based on Brownian motion, which can be used to determine the number‐concentration of nanoparticles, including viruses, in liquids on‐line. Extensive analysis showed the influence of suspension concentration and particle size on the accuracy of measurements. Natural nanoparticles of Adenovirus and several types of artificial nanoparticles, including precision nanobeads, uniform inorganic silica microspheres, monodisperse gold metal colloids and aggregated Aerosil nanoparticles, were measured and compared by counting the monitored particle number obtained using light scattered from individual particles, from which the particle number‐concentration, the product yield and the aggregation could be evaluated. CONCLUSION: This approach was compared with the mathematical calculation method and the emission spectrophotometry technique used for practical applications. The results showed this new approach had improved accuracy for determination of the particle number‐concentration. Copyright © 2010 Society of Chemical Industry     

Coke deposition mechanism on the pores of a commercial Pt-Re/γ-Al2O3 naphtha reforming catalyst

Coke deposition mechanism on a commercial Pt-Re/γ-Al₂O₃ naphtha reforming catalyst was studied. A used catalyst that was in industrial reforming operation for 28 months, as well as the fresh catalyst of the unit were characterized using XRD, XRF, and nitrogen adsorption/desorption analyses. Carbon and sulfur contents of the fresh and the used catalysts were determined using Leco combustion analyzer. The pore size distributions (PSD) of the fresh and the used reforming catalysts were determined using BJH and Comparison Plot methods. The Comparison Plot method produced the most reasonable PSDs for the catalysts. Through comparison of the PSDs of the fresh and the used catalysts, it was revealed that coke deposited on both micropores and mesopores of the catalyst at a constant thickness of 1.0 nm. The constant coke thickness on the catalyst pore walls in the naphtha reforming process (temp. ∼ 500 °C) implies that coke deposition reaction is the slow controlling step in comparison to the fast mass transfer rate of coke ingredients into the pores. The bulk density of the deposited coke on the used catalyst was calculated as 0.966 g/cm³.     

An inexact interior point method for optimization of differential algebraic systems

This paper presents an inexact factorization technique in the context of an interior point method for optimal control of systems described by Differential Algebraic Equations (DAEs). The proposed method is based on a numerically banded structure arising in the normal equations. The structure implies that banded factorization techniques can be used to calculate inexact Newton directions at a low computational cost. Numerical experiments show that a narrow band in the normal equations can be selected without impeding the convergence of the method.     

Numerical Investigation of Forced Convection Conjugate Heat Transfer from Offset Square Cylinders Placed in a Confined Channel Covered by Solid Wall

Flow over two isothermal offset square cylinders in a confined channel is simulated for different Reynolds numbers to disclose the forced convection heat transfer from the heated square cylinders to the ambient fluid. The spacing between the cylinder in the normal direction and the blockage ratio are fixed. The channel walls are covered by solid walls of thickness equal to the size of the cylinder and conjugate heat transfer is considered by including these walls. Heat transfer from the cylinders to the ambient fluid as well as that conducted within the solid wall through the conjugate interface boundary are investigated in connection with Reynolds number and are reported for both steady and periodic flows. Simulation is carried out for Reynolds number varying from 10 to 100 with air as the fluid. The onset of the vortex begins when the Reynolds number equals 48. The conjugate interface temperature declines when the Reynolds number grows. The isotherms in the solid wall show two dimensionality near the cylinder region.     

Nutritive value of mango seed kernel

Seed kernels of two cultivars (Chausa and Dusheri) of mango (Mangifera indica) were analysed for chemical composition, lipid classes, fatty acid composition, amino acid profile and chemical evaluation of protein quality. The seed kernels constituted about 18% of the total fruit and had 5% protein, 6–7% crude fat, 0.19–0.44% tannins, iodine value of 34–44 and saponification number 202–213. Oleic acid (42%) and stearic acid (39%) were the principal fatty acids in the oil. The in vitro digestibility was low in these cultivars, possibly due to the presence of tannins. Sulphur-containing amino acids (methionine+cystine) and isoleucine were the limiting amino acids in Chausa and Dusheri, respectively. The essential amino acid index and protein quality index were high, thus indicating the good quality of the protein in mango seed kernel.     

2150 t/h切圆燃烧锅炉旋流指数的试验研究

为减小切圆燃烧锅炉的汽温偏差,以2 150 t/h四角切圆燃烧锅炉为试验对象,研究了炉膛火焰中心与旋流指数的关联以及燃烧调整对旋流指数的影响.在试验分析的基础上,结合汽温偏差变化,得到了炉膛火焰中心随旋流指数的变化轨迹.从风箱炉膛压差控制的角度进行了计算,并分析了加大配风不均衡性对旋流指数的影响.结果表明:加大配风不均衡性会导致旋流指数增大;旋流指数与负荷不存在确定的对应关系;降低氧体积分数过程中旋流指数减小,降低氧体积分数后降负荷过程中旋流指数的变化幅度增大,易引起汽温偏差增大和超温现象;燃烧器下摆会增大旋流指数;反切分离燃尽风(SOFA)过大时,反向旋流指数的增大同样会引起两侧汽温偏差增大.     

Flow boiling in microchannels and microgravity

A critical review of the state of the art of research on internal forced convection boiling in microchannels and in microgravity conditions is the main object of the present paper.     

基于深度残差网络的雷达目标数量估计方法

传统雷达目标检测方法一般将单个距离单元的目标当成单目标进行检测,而不会估计距离单元内目标的数量。针对该研究空缺,提出一种基于深度残差网络的雷达目标数量估计方法。该方法将雷达信号转换成时频图并输入至训练好的深度残差网络。残差网络根据单个目标与多个目标对应时频图的差异即可准确得到雷达目标数量的估计值。仿真表明该方法能有效地估计出雷达目标数量。     

基于乘客多运动行为的公交客流计数判定方法

针对基于单目视觉的公交乘客人数统计判定方法不稳定、计数结果不准确的现状,结合公交车门附近乘客运动行为的复杂性和多样性,以及乘客运动行为对计数判定方法的干扰,给出一种基于乘客多运动行为分析的计数判定方法。采用轨迹聚类的方式对乘客运动行为进行分析,结合轨迹的空间特征和方向特征计算轨迹距离,并使用层次聚类方法进行聚类。分析聚类结果中每一类别所对应乘客类的运动行为,讨论各乘客类的运动行为对常用计数判定准则的影响,由此提出一种改进的公交车客流计数判定方法。利用采集的乘客上下公交车视频图像进行实验,结果表明,该方法能获得较高的统计精度和较好的稳定性。     

基于Cauchy矩阵的线性变换的研究

P-置换是实现分组密码扩散原则的关键组件.一般来说,分支数越大,扩散效果越明显.人们利用MDS矩阵设计最优线性变换作为分组密码组件的扩散层.在达到最优线性变换的同时,针对扩散矩阵还应满足矩阵中元素尽量少的要求,对Cauchy型MDS矩阵分别与Hadmard矩阵和循环移位矩阵的相互结合方式构造最优线性层的方法进行了研究.对Cauchy-Hadmard矩阵(同时是Cauchy矩阵和Hadmard矩阵)构造线性变换的一种方法进行了分析,给出了算法的C语言的关键程序,根据算法给出了一个最优线性变换的示例;对循环移位矩阵构造Cauchy矩阵进行了尝试和证明.结果显示Cauchy-Hadmard矩阵满足矩阵元素最少和运算复杂度低的要求,利用循环移位矩阵无法构造出Cauchy矩阵.这些结论为设计分组密码组件的扩散层提供了重要的方法参考.