基于信任链的骚扰电话预判技术研究

当前,骚扰电话乱象屡禁不止,严重影响了人民群众的正常生活,甚至威胁到个人财产安全,因此简单有效地识别骚扰电话技术成为亟待解决的问题。区别于现有的对电话号码进行黑白名单标记、大数据分析等识别方法,提出基于信任链的骚扰电话预判技术,从可信度量的角度计算来电号码的可靠程度,并针对高危受害群体的典型应用场景进行分析,通过对骚扰电话的预判,降低其受到电话骚扰甚至电话诈骗的可能性。     

计及RSC控制的DFIG短路电流直流分量解析表达

现有文献针对计及转子变流器(RSC)控制的双馈感应风电机组(DFIG)定子短路电流解析表达,将定子磁链当作一阶直流衰减分量或忽略功率外环控制。基于DFIG电压、磁链和RSC控制方程,得到定子电流关于定子电压和定子功率的传递函数,提出定子电流的精确解析表达式。基于RSC内、外环PI参数关系,推导直流分量衰减时间常数和角频率关于PI参数的表达式。分析了RSC内外环PI参数对定子电流直流衰减分量的影响。仿真结果验证了解析表达式的准确性,为PI参数选取和保护装置测量、整定提供依据。     

Multicolour tunable luminescence of thermal-stable Ce3+/Tb3+/Eu3+-triactivated Ca3Gd(GaO)3(BO3)4 phosphors via Ce3+ → Tb3+ → Eu3+ energy transfer for near-UV WLEDs applications

A series of single-component blue, green and red phosphors have been fabricated based on the Ca₃Gd(GaO)₃(BO₃)₄ host through doping of the Ce³⁺/Tb³⁺/Eu³⁺ ions, and their crystal structure and photoluminescence properties have been discussed in detail. A terbium bridge model via Ce³⁺ → Tb³⁺ → Eu³⁺ energy transfer has been studied. The emission colours of the phosphors can be tuned from blue (0.1661, 0.0686) to green (0.3263, 0.4791) and eventually to red (0.5284, 0.4040) under a single 344 nm UV excitation as the result of the Ce³⁺ → Tb³⁺ → Eu³⁺ energy transfer. The energy transfer mechanisms of Ce³⁺ → Tb³⁺ and Tb³⁺ → Eu³⁺ were found to be dipole-dipole interactions. Importantly, Ca₃Gd(GaO)₃(BO₃)_4:Ce³⁺,Tb³⁺,Eu³⁺ phosphors had high internal quantum efficiency. Moreover, the study on the temperature-dependent emission spectra revealed that the Ca₃Gd(GaO)₃(BO₃)_4:Ce³⁺,Tb³⁺,Eu³⁺ phosphors possessed good thermal stability. The above results indicate that the phosphors can be applied into white light-emitting diodes as single-component multi-colour phosphors.     

引江济巢工程对改善巢湖水质的数值模拟分析

巢湖受周围城市工业化及农业生产迅速发展的影响,湖区及流域的生态环境发生了巨大变化,尤其是近几年巢湖水质达到重富营养化水平。引江济巢工程是改善巢湖水质的重要工程措施,采用EFDC生态动力学模型模拟了巢湖不同调水流量、调水线路、调水时间对水环境的影响。结果表明,引江济巢工程在一定程度、时间上使巢湖湖区水质发生一定程度的改善,但若入湖水质不达标,调水也增加了巢湖的富营养化风险。     

Experimental Investigation of Heat Storage and Heat Transfer Rates during Melting of Nano-Enhanced Phase Change Materials (NePCM) in a Differentially-Heated Rectangular Cavity

In this work, an experimental study of melting heat transfer of nano-enhanced phase change materials(NePCM) in a differentially-heated rectangular cavity was performed. Two height-to-width aspect ratios of the cavity, i.e., 0.9 and 1.5, were investigated. The model Ne PCM samples were prepared by dispersing graphene nanoplatelets(GNP) into 1-tetradecanol, having a nominal melting point of 37℃, at loadings up to 3 wt.%. The viscosity was found to have a more than 10-fold increase at the highest loading of GNP. During the melting experiments, the wall superheat at the heating boundary was set to be 10℃ or 30℃. It was shown that with increasing the loading of GNP, both the heat storage and heat transfer rates during melting decelerate to some extent, at all geometrical and thermal configurations. This suggested that the use of NePCM in such cavity may not be able to enhance the heat storage rate due to the dramatic growth in viscosity, which deteriorates significantly natural convective heat transfer during melting to overweigh the enhanced heat conduction by only a decent increase in thermal conductivity. This also suggested that the numerically predicted melting accelerations and heat transfer enhancements, as a result of the increased thermal conductivity, in the literature are likely overestimated because the negative effects due to viscosity growth are underestimated.     

Modification of pool boiling regimes by sand deposition

Sand spots, attached to a copper ball surface by means of polyvinyl acetate adhesive and distributed over the surface with areal density that ranges between one spot per 1.18 cm² (for low‐density spots) and one spot per 0.51 cm² (for high‐density spots), serve as a temporary heat transfer enhancer during the quenching in liquid nitrogen. Highest heat flux densities, achieved during quenching, lie in the range 10.8 to 20.2 W/cm², depending on the sand layer structure. Application of the temporary enhancer increases an amount of heat, evacuated by highly effective nucleate and transition boiling, by factor of 4.5 as compared with the bare sample. The process of sand layer preparation, data acquisition peculiarities, relationship between heat exchange efficiency and the spots areal density, along with sand grit size are discussed in this paper.     

槽式太阳能集热管内相变微胶囊悬浮液的热力性能分析

针对传统使用水基和油基的太阳能集热器换热效果低和管壁热应力大的问题，以相变微胶囊悬浮液为工作流体，对抛物型槽式太阳能集热器进行了三维建模。采用蒙特卡罗射线追踪法结合有限容积法和有限元法的方法求解了太阳能集热管的光?热?力耦合问题，采用欧拉?欧拉多相流模型研究了相变微胶囊悬浮液在集热管内的流动换热特性。结果表明，相变微胶囊悬浮液强化了集热管内的对流换热，不仅降低了集热管的沿程壁温，且减少了集热管的周向温差，均化了集热管温度分布。集热管周向等效热应力呈花瓣型分布，对应的5个高温度梯度的位置附近(圆周角θ=5°, 90°, 175°, 225°和315°)出现等效应力局部峰值。吸热管内壁面θ=90°处轴向热应力为压应力，作用于整个管程，而径向热应力和切向热应力为拉应力，主要作用在进出口端。相变微胶囊悬浮液浓度越高，强化换热效果越好，集热管热应力越小，但产生的压降也随之增大。     

内插螺旋立式上行管流场及传热性能的实验研究

通过粒子图像测速流场实验与传热实验相结合，研究了内插螺旋立式上行管的螺旋节距、丝径、中径比等结构参数在不同Re下对流场、阻力及传热性能的影响。结果表明，内插螺旋能够有效扰动和混合管内流体，使管内形成多个纵向旋涡的流体结构、增大管壁附近液体涡量，有利于强化传热。当Re相同时，管内平均流速v、Nu和综合换热性能PEC均随丝径增大而增大，随中径比减小而增大；随节距增大，3种参数均出现增大的趋势，节距大于20 mm后开始减小。管内流体的阻力f随丝径和节距增大而减小，随中径比增大而增大。综合比较，在较低Re时，节距p=20 mm、丝径e=1.6 mm、中径比D/d=0.75时综合传热效果最好。