Flow of microorganisms in a hospital stair shaft — Full-scale measurements and mathematical model

Measurements of air flow and microorganism concentration have been made in the stair shafts of a hospital, using a diving bell-type of pressure-recording instrument, and a sampler for the microorganisms, respectively. Results of experiments were used to calculate the flow rate of microorganisms between the floors of the hospital. A mathematical model based on simplified transport equations is proposed, which would allow the prediction of the flow field and the distribution of microorganisms in the stair shaft. Comparisons between measurements and numerical calculations indicate that the mathematical model is able to predict the global flow field, qualitatively. The application of the numerical method can help to reduce the experimental work, as well as to investigate the complex exchange mechanisms of microorganisms.     

强电场作用下早龄期混凝土的氯离子迁移特征

电化学除氯技术能有效降低混凝土结构中的有害氯离子,降低混凝土结构失效风险。采用强电场方式对混凝土结构进行电化学除氯,并在不同的早龄期时间介入40、80、120 min的强电场作用,测试了内部氯离子含量变化和分布特征,并对通电后养护28 d试件进行回弹强度试验。研究结果表明：早龄期介入强电场作用能显著提高除氯效率,达到相同除氯效果时的作业时间约为传统电化学方法的1/300;氯离子分布特征表明,自由氯离子分布较传统电化学参数作用时更均匀,结合氯离子仍然存在保护层中间堆积现象;强电场作用后进行标准养护,回弹测试结果表明,强电场对混凝土的保护层宏观强度无明显影响。     

Characterization of metastable crystalline phases in the AlGe alloy system

Metastable crystalline phases have been produced in Al-Ge alloys by melt spinning liquid alloys and by rapidly heating thin films which are initially amorphous. The structures and compositions of these nonequilibrium phases have been characterized using convergent beam electron diffraction and energy dispersive X-ray spectroscopy. The results of these studies are compared directly with those of previous authors in order to resolve the controversy which has existed in the literature concerning the identity of the metastable phases which form in Al-Ge alloys when processed by novel techniques such as rapid solidification.     

减速带激励下汽车的非线性振动特性分析

研究了在减速带激励下具有磁流变阻尼器悬架系统汽车的非线性动力学行为.汽车采用七自由度模型,磁流变阻尼器采用Sigmoid模型.根据第二类Lagrange方程建立了汽车振动微分方程,并采用四阶Runge-Kutta法进行了数值仿真.首先以减速带高度为参数对汽车运动进行分岔分析,然后通过时间历程图、相位图、Poincaré截面分析了汽车在不同减速带高度时所呈现的不同运动形式,得到了系统发生混沌运动时减速带的高度范围,并分析了系统经拟周期运动通向混沌运动的途径.研究结果为汽车平顺性控制和安全性设计提供了理论指导.     

Using computational intelligence for large scale air route networks design

Due to the rapid development of air transportation, Air Route Networks (ARNs) need to be carefully designed to improve both efficiency and safety of air traffic service. The Crossing Waypoints Location Problem (CWLP) plays a crucial role in the design of an ARN. This paper investigates this problem in the context of designing the national ARN of China. Instead of adopting the single-objective formulation established in previous research, we propose to formulate CWLP as a bi-objective optimization problem. An algorithm named Memetic Algorithm with Pull–Push operator (MAPP) is proposed to tackle it. MAPP employs the Pull–Push operator, which is specifically designed for CWLP, for local search and the Comprehensive Learning Particle Swarm Optimizer for global search. Empirical studies using real data of the current national ARN of China showed that MAPP outperformed an existing approach to CWLP as well as three well-known Multi-Objective Evolutionary Algorithms (MOEAs). Moreover, MAPP not only managed to reduce the cost of the current ARN, but also improved the airspace safety. Hence, it has been implemented as a module in the software that is currently used for ARN planning in China. The data used in our experimental studies have been made available online and can be used as a benchmark problem for research on both ARN design and evolutionary multi-objective optimization.     

深度学习在自然语言处理领域的研究进展

通过定量与定性相结合的方式全面分析了深度学习在自然语言处理领域的研究情况。采用CiteSpace和VOSviewer对深度学习在自然语言处理领域的研究国家、机构、期刊分布、关键词共现、共被引网络聚类及时间轴视图等进行知识图谱绘制,理清研究脉络。通过深入挖掘领域内的重要文献,总结深度学习在自然语言处理领域的研究趋势、存在的主要问题或发展瓶颈,并给出相应的解决办法与思路。对于如何跟踪深度学习在自然语言处理领域的研究成果给出建议,为该领域的后续研究与发展提供参考。     

Stability of a rotating pretwisted nonuniform cantilever with a tip mass subjected to dissipative and follower forces

The stability of a rotating pretwisted non-uniform viscoelastic cantilever beam subjected to a tangential force applied at its free end is determined by a method of approximation based on an adjoint variational principle. The coupled equations of motion are derived from a conservation law, the adjoint boundary value problem is introduced, and an approximate stability determinant is developed from the variational principle. The stability determinant is solved numerically for a variety of choices of values for the rotary inertia of the beam, transverse and rotary inertia properties of a mass capping the free end, the rotational speed, and the pretwist angle, and several graphs are presented to show the influence of these parameters upon the value of the critical flutter load.