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关键词： Gemini表面活性剂   表面张力   泡沫性能   耗散粒子动力学模拟   聚集形态  

摘要： 以1-溴十二烷、2-甲氨基乙醇、1,3-二溴丙烷、1,4-二溴丁烷、1,6-二溴己烷、1,8-二溴辛烷、1,10-二溴癸烷和1,12-二溴十二烷为原料,制得含有双羟基的Gemini表面活性剂〔缩写为12(OH)-s-12(OH),其中s=3、4、6、8、10和12〕。并测定了双羟基Gemini表面活性剂的热稳定性及其在水溶液中的表面张力及泡沫性能;采用耗散粒子动力学(DPD)方法预测了Gemini表面活性剂在水溶液中的聚集形态。结果表明,该类型Gemini表面活性剂具有较好的热稳定性和泡沫性能,随着连接基团长度的增加(s≤6),其在水溶液中的临界胶束浓度(CMC)从0.62mmol/L(s=3)降至0.21mmol/L(s=6)左右,且当连接基团长度s>6后CMC基本不变。随着Gemini表面活性剂摩尔分数的增加,胶束形态从球状胶束→棒状胶束→层状胶束→反胶束网络结构逐渐转变,且连接基团长度的改变几乎不影响其在水溶液中的胶束形态转变。

关键词： 表面活性剂   聚醚   有机硅   表面张力   润湿性能   乳化性能  

摘要： 利用端氢硅油和烯丙基聚醚合成了聚醚有机硅表面活性剂,探讨了不同结构的端氢硅油对产物的表面张力、润湿性能、发泡稳泡性能以及乳化性能的影响,并用FTIR对产物进行表征。结果表明,产物的表面张力、润湿性能和乳化性能随着Si-O疏水基m值的增加而降低,当Si-0疏水基m值为1时表面张力最小,可降至23,625mN/m,此时产物的润湿性能和乳化性能最佳;当Si-0疏水基m值为3时,产物的发泡、稳泡性能最佳。

关键词： 共轴微通道   气水两相流   流型   表面张力  

摘要： 本文以共轴流微通道芯片为研究对象,采用分散相为氩气、连续相为十二烷基硫代硫酸钠(SDS)的水溶液,在400μm×600μm矩形通道内形成气液两相流。改变表面活性剂的浓度,观察表面张力改变下流型的变化趋势,绘制出以连续相毛细数为横坐标、分散相韦伯数为纵坐标的流型分布图。实验得到滴流、滴状射流、弹状流、环状流的四种流型。随着表面张力减小,弹状流与环状流之间的边界向右移,滴流与射流之间的向边界右移。弹状流与滴流、射流之间的边界向右移不明显。

关键词： 包卷式纸箱   渗透性   表面张力   内结合强度   直角测试   拉力测试  

摘要： 目的根据纸板粘合机理,从纸板特性指标角度进行研究,建立包卷式纸箱封合质量标准评价体系,实现通过纸板表面性能相关指标测试,即可评判预测包卷式纸箱在线封合质量的目的。方法通过设计不同试样进行直角粘合模拟测试及拉力测试,研究瓦楞纸板的表面性能参数对包卷式纸箱封箱效果的影响,找到纸板表面吸水渗透性、表面张力、纸纤维内结合强度等指标的合理范围,建立包卷式纸箱封合质量标准评价体系。结果根据试验结果预测,纸板印刷面吸水量低于1 g/m^2,表面张力低于38mN/m,内结合强度低于100 J/m^2的纸板,包卷式纸箱粘合封箱强度较低。结论可以通过增加测试纸板表面吸水渗透性、表面张力、纸纤维内结合强度等指标,建立包卷式纸箱的封合质量标准评价体系,对包卷式纸箱在线封合质量进行预测。

关键词： Bubbling fluidized bed combustor   Axial temperature distribution   Exhaust emissions   Combustion efficiency   Thermal efficiency   Mass and energy balance  

摘要： Combustion and emission characteristics of Egyptian sugarcane bagasse and cotton stalks powders were investigated in a bubbling fluidized bed combustor (BFBC) using silica sand as an inert bed material. Mixing and fluidizing characteristics of the two biomass materials and bed material of a certain size distribution were studied. It was found that, the feed rate ranged from 70 to 113g/min and feed rate of 51g/min for cotton stalks and sugarcane bagasse, respectively may be suitable for better combustion characteristics in the BFBC. The effect of different operating parameters on the axial temperature and gas concentration profiles (O-2, CO2, CO, H2S, SO2 and NOx) was investigated. It was found that the formation of NOX during combustion doesn't represent a problem as the nitrogen content of fuel is low, the bed temperature of fluidized bed is below 900 degrees C, and the particle size of the biomass is small. It was found that combustion efficiency ranged from 90 to 100% and from 93 to 98.8% for sugarcane bagasse and cotton stalks, respectively. Thermal efficiency was found to be in the range of (33.7-41%) and (32.5-48.7%) for sugarcane bagasse and cotton stalks, respectively. A verification model for mass and heat balance of combustion experiments was constructed to confirm that the measured values of different parameters were measured accurately with acceptable percent of error.

关键词： Medical visualizations   aneurysms   blood flow   parametrization   classification  

摘要： We present a Cerebral Aneurysm Vortex Classification (CAVOCLA) that allows to classify blood flow in cerebral aneurysms. Medical studies assume a strong relation between the progression and rupture of aneurysms and flow patterns. To understand how flow patterns impact the vessel morphology, they are manually classified according to predefined classes. However, manual classifications are time-consuming and exhibit a high inter-observer variability. In contrast, our approach is more objective and faster than manual methods. The classification of integral lines, representing steady or unsteady blood flow, is based on a mapping of the aneurysm surface to a hemisphere by calculating polar-based coordinates. The lines are clustered and for each cluster a representative is calculated. Then, the polar-based coordinates are transformed to the representative as basis for the classification. Classes are based on the flow complexity. The classification results are presented by a detail-on-demand approach using a visual transition from the representative over an enclosing surface to the associated lines. Based on seven representative datasets, we conduct an informal interview with five domain experts to evaluate the system. They confirmed that CAVOCLA allows for a robust classification of intra-aneurysmal flow patterns. The detail-on-demand visualization enables an efficient exploration and interpretation of flow patterns.

关键词： Flow patterns   Pneumatic conveying   Classification model   Machine learning   Signal analysis  

摘要： Dense-phase pneumatic conveying of pulverized coal experiments with superficial gas velocity ranged from 0.59 m s(-1) to 2.43 m s(-1) were carried out on the self-established 50 mm I.D. industrial pipe facility. The fluctuations of pressure, solid velocity, solid concentration and the average cross-section concentration were analyzed in terms of relative standard deviation (RSD), powder spectrum density analysis (PSD) and wavelet analysis. Further, a novel classification model of flow patterns for dense-phase pneumatic conveying of pulverized coal was proposed. The model was based on the relationships among superficial gas velocity, particle velocity and solid concentration. K-means method, std method, k-medoids and CART method were compared firstly and then the k-means method and CART method were introduced to classify the flow patterns. The bagged trees method and 5-fold cross-validation were used to train the classification model, whose accuracy was 95.2% and 91.9%. It meant that the new classification model was able to classify the flow patterns in the pneumatic conveying of pulverized coal. In the end, the change of flow patterns and transmission of flow patterns were explained by the wavelet analysis method from the aspects of different signal scales and power spectrum analysis. The new classification model will be of great help for the industry to have a better understanding on the classification and control of flow patterns. (C) 2019 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

关键词： Fluidized beds  

摘要： This article discusses a simulation study performed to investigate the effect of particle collision on inter-particle and gas-solid heat transfer processes, and other related bed flow characteristics. The effect of particle elasticity is presented using different values of the particle-particle coefficient of restitution. The simulation study was carried out using a two-dimensional model of a fluidized bed reactor incorporated to ANSYS Fluent 16.2 software. Two different materials, steel beads and sand particles, were used as the bed material fluidized by air. The simulation results are compared to those from previous studies on fluidized bed reactors containing a single bed material. The coefficient of restitution affected the bed hydrodynamics. Specifically, an increasing coefficient of restitution resulted in an increasing bed pressure drop and decreasing void fraction, granular temperature, particle velocity, and collision frequency. Conversely, increasing the particle coefficient of restitution resulted in decreasing the particle-particle heat exchange coefficient and the gas-particle heat transfer coefficient. The gas-particle heat transfer coefficient for sand particles was higher than that for steel beads. The effect of the coefficient of restitution on the flow characteristics from a binary mixture bed was quite similar to those of single material beds found in previous studies. This study demonstrated that the restitution coefficient clearly affected both the particle-particle and gas-particle heat transfer processes.

摘要： A new instrument, the High-speed Particle Phase Discriminator (PPD-HS), developed at the University of Hertfordshire, for sizing individual cloud hydrometeors and determining their phase is described herein. PPD-HS performs an in situ analysis of the spatial intensity distribution of near-forward scattered light for individual hydrometeors yielding shape properties. Discrimination of spherical and aspherical particles is based on an analysis of the symmetry of the recorded scattering patterns. Scattering patterns are collected onto two linear detector arrays, reducing the complete 2-D scattering pattern to scattered light intensities captured onto two linear, one-dimensional strips of light sensitive pixels. Using this reduced scattering information, we calculate symmetry indicators that are used for particle shape and ultimately phase analysis. This reduction of information allows for detection rates of a few hundred particles per second. Here, we present a comprehensive analysis of instrument performance using both spherical and aspherical particles generated in a well-controlled laboratory setting using a vibrating orifice aerosol generator (VOAG) and covering a size range of approximately 3-32 mu m. We use supervised machine learning to train a random forest model on the VOAG data sets that can be used to classify any particles detected by PPD-HS. Classification results show that the PPD-HS can successfully discriminate between spherical and aspherical particles, with misclassification below 5% for diameters > 3 mu m. This phase discrimination method is subsequently applied to classify simulated cloud particles produced in a continuous flow diffusion chamber setup. We report observations of small, near-spherical ice crystals at early stages of the ice nucleation experiments, where shape analysis fails to correctly determine the particle phase. Nevertheless, in the case of simultaneous presence of cloud droplets and ice crystals, the introduced particle shape ind

关键词： Annular-blade distributor   Bed pressure drop   Distributor pressure drop   Heat transfer coefficient   Immersed heater   Swirling fluidized bed  

摘要： The present work investigates the heat transfer between the immersed heater and bed and hydrodynamics of the bed in swirling fluidized bed. The heat transfer process and bed hydrodynamics characteristics for swirling fluidized bed reactor (SFBR) were compared to those of conventional fluidized bed reactor (CFBR). Then the influence of particle diameter on the bed flow characteristics and heat transfer process in SFBR were studied. The heat transfer coefficient was calculated at different superficial air velocities, radial positions, and bed heights. Compared to a CFBR, the bed pressure drop and distributor pressure drop for SFBR were lower, that characterizes swirling bed reactor. The heat transfer coefficient of SFBR was higher than the corresponding of CFBR at lower portion of the bed and it was lower at the upper portion of the bed for all radial positions and for all air superficial velocities. Increasing particle diameter in SFBR resulted in decreasing both the heat transfer coefficient and bed pressure drop.