A high-throughput chaotic advection microreactor for preparation of uniform and aggregated barium sulfate nanoparticles

A high-throughput (105.5 g/h) passive four-stage asymmetric oscillating feedback microreactor using chaotic mixing mechanism was developed to prepare aggregated Barium sulfate (BaSO₄) particles of high primary nanoparticle size uniformity. Three-dimensional unsteady simulations showed that chaotic mixing could be induced by three unique secondary flows (i.e., vortex, recirculation, and oscillation), and the fluid oscillation mechanism was examined in detail. Simulations and Villermaux–Dushman experiments indicate that almost complete mixing down to molecular level can be achieved and the prepared BaSO₄ nanoparticles were with narrow primary particle size distribution (PSD) having geometric standard deviation, σ_g, less than 1.43 when the total volumetric flow rate Q_total was larger than 10 ml/min. By selecting Q_total and reactant concentrations, average primary particle size can be controlled from 23 to 109 nm as determined by microscopy. An average size of 26 nm with narrow primary PSD (σ_g = 1.22) could be achieved at Q_total of 160 ml/min.     

Priority-MECE: A Mobile Edge Cloud Ecosystem Based on Priority Tasks Offloading

Mobile Networks and Applications - With the rapid development of Internet of things, the traditional city model is no longer applicable. Therefore, the emerging concept of smart city meets the...     

依托"大数据行业应用"虚拟教研室培养跨学科人才

在实施国家大数据战略和创新型国家建设的引导下,培养跨学科思维与能力是创新型人才培养的核心要求.大数据是一个典型的学科交叉的技术,资源分散是当前高校大数据人才培养存在的主要问题.该文以长沙理工大学"大数据行业应用"虚拟教研室建设为例,打造"大数据"特色跨学科跨专业教学组织,从课程体系、实践环节、师资队伍、质量监督等方面提出建设措施,为培养跨学科创新型复合型人才提供参考.     

高光谱成像用高帧频CMOS图像传感器北大核心

针对高帧频、全局曝光和光谱平坦等成像应用需求,设计了一款高光谱成像用CMOS图像传感器。其光敏元采用PN型光电二极管,读出电路采用5T像素结构。采用列读出电路以及高速多通道模拟信号并行读出的设计方案来获得低像素固定图像噪声(FPN)和非均匀性抑制。芯片采用ASMC 0.35μm三层金属两层多晶硅标准CMOS工艺流片,为了抑制光电二极管的光谱干涉效应,后续进行了光谱平坦化VAE特殊工艺,并对器件的光电性能进行了测试评估。电路测试结果符合理论设计预期,成像效果良好,像素具备积分可调和全局快门功能,最终实现的像素规模为512×256,像元尺寸为30μm×30μm,最大满阱电子为400 ke^(-),FPN小于0.2%,动态范围为72 dB,帧频为450 f/s,相邻10 nm波段范围内量子效率相差小于10%,可满足高光谱成像系统对CMOS成像器件的要求。     

不同场景下铜排通流能力研究

随着电子技术的发展,设备的功率越来越高,铜排作为大通流部件在电气设备和电力系统中有着广泛的应用.铜排在工作时通大电流,设计时必然要考虑其带来的温升问题.温升过大时会加速部件老化甚至导致故障造成经济损失.该文通过对在空气自然对流、强制风冷、封闭或半封闭,截面积相同但厚度不同4种场景下铜排通流能力的测试和分析,得出铜排通流与场景及和尺寸的关系,强制风冷环境温升最低,利于通流,同时薄的铜排单位长度有着更大的散热表面积.该文的结论为相关技术人员提供一些铜排设计和技术上的参考.