LBM investigation of a Cu-water nanofluid over various configurations of pipes in the mixed convection flow

Increasing the heat capacity of heat exchangers is a crucial need for modern devices. The thermal conductivity of the usual fluids and the Nusselt (Nu) number of flows containing such fluids are two bottlenecks in the way of increasing heat delivery in the heat exchangers. For this reason, nanofluids have been introduced. The effect of utilizing a Cu-water nanofluid as a coolant of two hot pipes in a square cavity is investigated numerically with a two-component lattice Boltzmann method. The volume fraction of nanoparticles is assumed to be constant (0.03) while the Richardson (Ri) number varies from 0.02 to 20. Results show that the effectiveness of nanoparticles is better observed in the natural convection mode. However, sedimentation is also very probable at high Ri numbers, which significantly reduces the effectiveness of the nanoparticles. Configurations which produce a natural convection stream similar to the forced convection one as well as the configurations with high spacing and hence, low heat stream interactions, are the best choices for a uniform heat rate from the pipes.     

Three-level designs: Evaluation and comparison for screening purposes

Since their introduction by Box and Hunter, resolution criteria have been widely used when comparing regular fractional factorials designs. In this article, we investigate how a generalized resolution criterion can be used to assess some recently developed three-level screening designs, such as definitive screening designs (DSDs) and screening designs from weighing matrices. The aim of this paper is to capture the projection properties of those three-level screening designs, complementing the work of Deng and Tang, who used generalized resolution and minimum aberration criteria for ranking different two-level designs, particularly Plackett-Burman and other nonregular factorial designs. An advantage of generalized resolution, extended here to work on three-level designs, is that it offers a useful criterion for ranking three-level screening designs, whereas the Deng and Tang resolution is used mainly for the assessment of two-level designs. In addition, we applied a projection estimation capacity (PEC) criterion to select three-level screening designs with desirable properties. Practical examples and the best projections of the designs are presented in tables.     

水-油连续螺旋折流板换热器热力性能研究

利用计算流体力学(Computational Fluid Dynamic, CFD)方法，针对连续螺旋折流板换热器建立物理模型和数学模型，在管侧介质为水和壳侧介质为原油条件下，研究不同原油流量及螺旋角对螺旋折流板换热器内部流场、换热性能及阻力性能的影响，并拟合了水油换热时螺旋折流板换热器的Nu、f与Re的关联式。结果表明：22°螺旋角的螺旋折流板换热器与其它较小螺旋角换热器对比，壳侧压降和换热系数逐渐减小，综合换热性能最佳。通过对壳侧原油为层流状态下的阻力系数和对流换热系数关系式进行拟合，更好地指导水-油连续螺旋折流板换热器的热力设计。     

基于蜻蜓翅脉结构的连续碳纤维增强树脂基复合材料仿生设计与增材制造

以具有轻质高强优异性能的蜻蜓翅脉结构为设计灵感，在分析翅脉网格结构抗冲击原理的基础上，设计了传统和仿生两类对比结构。采用熔融挤出3D打印机成功制备了具有不同结构的连续碳纤维增强聚乳酸复合材料试样，并对不同结构复合材料试样的拉伸性能和抗冲击性能进行了测试和对比分析。研究分析结果表明：由于拉伸力方向上的连续碳纤维含量相对较少，限制了仿生结构复合材料抗拉强度的提高，但仿生结构的平均抗拉强度为传统结构的1.18倍；当仿生结构复合材料试样受到冲击力时，其内部六边形结构的连接角度会发生变化，从而极大消耗冲击能量，同时具有六边形网格结构的连续碳纤维可以有效阻碍裂纹的扩展，因此仿生结构的平均冲击韧性可以达到传统结构的2.46倍；仿生蜻蜓翅脉结构可以显著提高增材制造复合材料的综合力学性能，且对于抗冲击性能的提高具体突出效果。连续碳纤维增强树脂基复合材料的有效可行的仿生蜻蜓翅脉结构设计和增材制造，可极大扩展其在高冲击载荷领域中的相应应用。     

多方向投影寻踪与高光谱遥感图像特征提取

介绍了投影寻踪算法的基本原理，构造了面向易混分类别的高光谱遥感数据投影寻踪指标，在单方向投影寻踪算法的基础上，提出了序贯多方向投影寻踪算法.在该算法提取出的特征方向上，易混分地物类别的分类精度提高6%左右，但存在压制其他地物的矛盾.     

三级连续碳化法生产纳米碳酸钙新工艺研究

采用有效容积依次递增的预塔、中塔、后塔三个碳化塔串联,塔内气液连续逆流操作、塔间气液连续并流或错流操作,严格控制氢氧化钙浆液的浓度、流量、温度和碳化气的浓度、流量,并通过pH计或电导仪进行跟踪检测碳化度,可实现纳米碳酸钙生产工艺连续化、产品质量稳定化、产量规模化.     

连续乳化的水相与油相流量控制系统设计

乳化炸药连续生产中的水相和油相流量配比控制十分重要。此文介绍了一种控制系统的设计，内容包括水相和油相流量控制过程与原理、计算机的数据采样与存取。分析了系统因素造成的流量控制滞后原因，提出了相应解决方案。     

基于随机Petri网的井下连续运输系统可靠性研究

在分析煤矿井下连续运输系统结构、运行特征的基础上,应用随机Petri网理论构建煤矿井下连续运输系统SPN模型,实现了系统部件故障维修过程的动态描述。同时,结合马尔科夫方法对某煤矿井下连续运输系统进行可靠性分析,计算得出其系统有效度和不可用度。该研究为分析煤矿井下连续运输系统可靠性提供新的思路。     

地下矿体连采顶板控制技术研究

低品位贫矿体地下连续开采技术是实现矿山高效生产的采矿方法，其中顶板控制是该采矿方法的关键技术之一。利用相似材料模拟试验和FLAC-3D研究方法，对某有色金属矿山厚大、低品位的3#矿体的地下连续开采进行了系统研究，包括矿体顶板自然崩落性、顶板人工诱导崩落时序系统以及开采过程中顶板应力变化规律的研究。研究结果表明，3#矿体顶板初次垮落步距为96 m，顶板自然崩落性较差。采用顶板人工诱导崩落技术，在顶板切割诱导槽进行诱导放顶，合理地布置矿体开采和顶板崩落之间的时间和空间顺序，使采空区顶板随矿体开采逐步垮落，能够保证矿体的安全回采。顶板应力随开采过程呈现逐渐升高的趋势，顶板垮落前应力值降低，但应力变化幅度不大。研究证实，采用顶板人工诱导崩落技术对连续开采的地下矿体顶板可以进行有效控制。