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摘要： This paper studies how the underlying factors that determine an individual's wage changes over their life-cycle, how these factors change at di erent education levels, and when a worker makes job-to-job moves. Using a longitudinal matched employer-employee data set from the Portuguese Ministry of Labor; I nd that human capital accumulation and job mobility play an important role in wage growth during the beginning of an individual's career. More speci cally, I nd that after 20 years of work wages increase, on average 41%. A large fraction of the returns to labor market experience is rooted in the returns to general training (25%) but sorting into better paying rms and job/titles is responsible for a signi cant 19% and 10% of the returns to labor market experience, respectively. Job-to-job mobility also enhances life-cycle earning (14%), as does the ability of the worker (32%).

关键词： Kihong Park  

摘要： While there are several computational studies on differential mobility analyzers (DMA), there is none for high flow DMA to classify nanoparticles less than 3 nm. A specific design of a high flow DMA, a half mini DMA, is investigated to predict its performance through numerical modeling in the incompressible flow regime. The governing equations for flow field, electric field and aerosol transport are solved using COMSOL 5.3. The transfer function of the half mini DMA is compared with that of a nano DMA (TSI 3085). The results show that both the height of the transfer function and resolution (R) of the half mini DMA are much better than those of nano DMA in sub-2 nm particle size range. Finally, the transfer function of half mini DMA is evaluated for different values of aerosol flow rate to the sheath flow rate (q/Q). Comparison of the simulated transfer function with existing models from Knutson-Whitby and Stolzenburg is also elucidated. It is found that the former model overestimates the resolution;whereas the latter is close to the simulation results for q/Q above 0.067. This work provides a useful method to study the flow regimes and transfer function of a high flow DMA. Copyright (c) 2018 American Association for Aerosol Research

关键词： Binary particle systems   discrete element method   fluidized bed   mixing characteristics   particle properties  

摘要： The fluidization of quartz in the fluidized bed has great influence on the combustion and gasification of refuse-derived fuel (RDF). The combined computational fluid dynamics (CFD) and discrete element method (DEM) approach was used to explore the gas-solid hydrodynamics and mixing characteristics in a three-dimensional fluidized bed. All numerical analyses were performed referring to the experiments (Goldschmidt, Beetstra, and Kuipers 2004). The simulation results indicated that the quartz volume fraction agrees well with the experimental data. Furthermore, the cylinder-shaped RDF particles can mix well with the quartz particles as they were added from upside. For binary systems, it is necessary to investigate solid flow characteristics as well as pressure drops and examine the influence of superficial gas velocity on the solid mixing. Two main parameters are discussed: mixing degree and the time required to reach the steady state. It is also found that inlet gas velocity and particle properties (particle density ratio, shape and size) are significant factors on particle mixing in a fluidized bed.

关键词： Ricci孤立子   曲率   势函数  

摘要： 过去几十年中,人们越来越关注满足特殊结构方程度量的黎曼流形的研究。其中一个最重要的例子是Ricci流和Ricci孤立子。Ricci流是研究黎曼流形最有力的工具之一,它在Hamilton和Perelman证明Poincaré猜想过程中起着关键作用,并且广泛用于研究流形的拓扑结构、几何性质和其它复杂结构。Ricci流方程本身作为偏微分方程的研究也十分重要,它给出了关键度量的规范方法。关于Ricci孤立子有两个重要的研究方向,一是研究黎曼流形的Ricci孤立子结构对拓扑结构的影响,另一个是研究它在几何学中的影响。本文,我们将归纳总结Ricci孤立子曲率及势函数的估计结果。

关键词： Mobile app traffic classification   Flow feature selection   Classification robustness   Machine learning  

摘要： In machine-learning based mobile app traffic classification, flow feature distributions can easily drift due to changes in network environments, user habits etc. Unstable features may negatively influence mobile app traffic classification robustness, so to remedy this problem, this paper investigates how to obtain optimal feature sets for improving classification robustness of mobile app traffic. Specifically, we develop a method to search for stable and discriminative features by jointly analyzing mobile app traffic characteristics and assessing the degree of feature drift. Along these lines, we first analyze the in-flow behavior characteristics of traffic flows, so as to extract a potential feature set for mobile app traffic data. Next, we present two new metrics to assess the degree of drift experienced by the flow features from different perspectives and design a composite metric to score these features by considering the degree of drift as a penalty factor of discrimination power. Based on these metrics, we further propose an algorithm to search for optimal features with high discrimination power but low degree of drift. Existing flow features and feature selection algorithms were implemented for our comparison experiments. Our experimental results on real mobile app traffic data demonstrate the effectiveness of our feature set and feature selection algorithm on improving classification robustness.

关键词： 动态表面张力   动态吸附   表面活性剂   药物制剂  

摘要： 动态表面张力(DST)是体现液体表面张力变化的一个物理量,是评价液体运动特性的关键物理属性之一,目前在工业、农业等领域已受到广泛关注。本文从动态表面吸附、DST测定方法等方面详细介绍了DST;以表面活性剂溶液的DST为切入点,从液体的雾化、扩散润湿、表界面特性等角度讨论了液体DST对改善药物喷雾干燥过程的影响,及其对流化床制粒包衣效果的作用;通过分析固体物料遇水瞬间的行为,探讨了辅料增溶效果、片剂崩解机制等;旨在通过总结归纳国内外DST研究成果,阐述DST在药剂学研究中的应用价值。

关键词： 招平断裂   玲珑断裂   水化学   D,18O同位素   补给高程   东汤地热田   天然温泉  

摘要： 招远东汤地热田是胶东现有16处天然温泉典型之一,以东汤地热田为例,剖析胶东地热田的补径排特征,对胶东各地热田的资源评价及开发利用具有重要的现实意义。该文通过地热地质条件综合分析、地热流体与基岩水及第四系水水化学成分对比、D,18O同位素分析、模型概化等手段综合研究,认为东汤地热田主要受招平断裂带与玲珑断裂带的控制,其复合部位为地热流体入渗、深循环的主径流通道。地热流体的Cl-,F-,Ba2+,Li-,Sr2+,H2Si O3等离子及TDS含量明显高于其周边的水体,且随第四系水、基岩水及地热流体埋藏深度的增加,其δD与δ18O值逐渐偏负,确定地热流体与其周边的水体并无水力联系;通过地热流体D,18O同位素与大气降雨线的关系,得出地热流体补给来源于大气降雨。由D同位素高程效应,算得地热流体补给高程为314～414 m左右,结合招平断裂与玲珑断裂的复合部位延伸方向,确定地热田的主要补给区为距离地热田东北方向15 km的双顶山山区。该文补径排特征的研究,对胶东其他天然温泉的补径排特征及补给区的研究具有一定的借鉴意义。

关键词： 表面张力   饱和吸附量   最大压差   吸附等温式  

摘要： 分别测定得到6种短链醇溶液在不同浓度下的表面张力,考察了分子结构对表面张力和吸附性能的影响,提出了适用于综合实验的醇类稀溶液浓度范围,并利用Origin软件分别基于传统数据处理方式和曲线拟合方式计算得到吸附分子的横截面积。通过此实验,力求针对最大压差测定方法、处理实验数据和理论知识点3个目标层次,使学生尽可能全面地掌握表面化学相关实验原理和技术、数据处理方法,加深影响表面张力和吸附测定的因素和相应的概念、理论的理解,努力培养和提高学生实际应用能力。

关键词： 表面张力  

摘要： 新年到了,趁着假期,小魔豆到野外疯玩了一通,一回到家,妈妈就拿出酒精棉好好给小魔豆擦了手。酒精棉是妈妈自己做的,桌子上就放了瓶医用酒精,小魔豆看看那瓶酒精,又看看边上的矿泉水瓶,问妈妈:'这酒精和水看着一模一样,可它们的性质、功用却那么不同,要是把它们放在一起,会发生什么情况呢?''当然就混合喽,酒精浓度被稀释了。

关键词： 成矿阶段   流体包裹体   石英脉型   达亚纳钨钼矿  

摘要： 位于内蒙古东乌旗地区的达亚纳钨钼矿是一中小型石英脉型钨钼矿床,矿体产于黑云母花岗岩岩体上部和与地层接触带的裂隙中。本文经过系统的野外调查、岩相学、包裹体及H、O同位素实验,探讨达亚纳钨钼矿成矿流体演化。