Super-Planckian thermal radiation enabled by hyperbolic surface phonon polaritons

Excitation of surface resonance modes and presence of resonance-free hyperbolic modes are two common ways to enhance the near-field radiative energy transport, which can find wide applications in noncontact thermal management and energy harvesting. Here, we identify another way to achieve the super-Planckian thermal radiation via hyperbolic surface phonon polaritons (HSPhPs). Based on the fluctuation-dissipation theory, the near-field radiative heat flux between bulk hexagonal boron nitride (hBN) planes with the optical axis perpendicular to the radiative energy flow can be 120 times as large as the blackbody limit for a gap distance of 20 nm. When the film thickness is reduced to 10 nm, the radiative heat flux is found to increase by 26.3%. The underlying mechanism is attributed to the coupling of Type I HSPhPs inside the anisotropic hBN film, which improves the energy transmission coefficient over a broad wavevector space especially for waves with extremely high wavevectors. This work helps to deepen the understanding of near-field radiation between natural hyperbolic materials, and opens a new route to enhance the near-field thermal radiation.     

Aerodynamic performance analysis of trains on slope topography under crosswinds

This work used the computational fluid dynamics method combined with full-scale train tests to analyze the train aerodynamic performance on special slope topography. Results show that with the increment in the slope gradient, the aerodynamic forces and moment increase sharply. Compared with the flat ground condition, the lateral force, lift force, and overturning moment of the train on the first line increase by 153.2%, 53.4% and 124.7%, respectively, under the slope gradient of 20°. However, with the increment of the windward side's depth, the windbreak effect is improved obviously. When the depth is equal to 10 m, compared with the 0 m, the lateral force, lift force and overturning moment of the train on the first line decrease by 70.9%, 77.0% and 70.6%,respectively. Through analyzing the influence of slope parameters on the aerodynamic performance of the train, the relationships among them are established. All these will provide a basic reference for enhancing train aerodynamic performances under different slope conditions and achieve reasonable train speeds for the operation safety in different wind environments.     

材料、叙述、视角与汉唐墓葬美术史书写——由郑岩:《逝者的面具—汉唐墓葬艺术研究》引起的思考

本文对郑岩教授新作《逝者的面具—汉唐墓葬艺术研究》进行了概括与评述,并结合书中一些重要的论文案例,注意到作者在材料、叙述、视角等方面的特色,从而对该书的写作进行了客观评价与反思。     

Polybrominated Diphenyl Ethers in Surface Sediment from Songhua River Basin, Northeast of China

Sixty sediment samples were collected from the main Songhua River in three years. Twelve polybrominated diphenyl ether ( PBDE) congeners ( BDE17, 28, 47, 66, 99, 100, 153, 154, 138, 183, and BDE?209) w...     

Evolution of insoluble eutectic Si particles in anodic oxidation films during adipic-sulfuric acid anodizing processes of ZL114A aluminum alloys

The effects of insoluble eutectic Si particles on the growth of anodic oxide films on ZL114A aluminum alloy substrates were in-vestigated by optical microscopy (OM) and scanning electron microscopy (SE...     

Acquisition algorithm assisted by AGC control voltage for DSSS signals

An appropriate acquisition configuration in terms of signal quality can optimize the acquisition performance. In view of this, a new approach of acquisition assisted by the control voltage of automatic gain control(AGC) is proposed. This approach judges the signal power according to the AGC control voltage and switches the working modes correspondingly and adaptively. Non-coherent accumulation times and the detection threshold are reconfigured according to the working mode. Theoretical derivation and verification by simulation in typical situations are provided, and the algorithm is shown to be superior in terms of the mean acquisition time, especially in strong signal scenarios compared with the conventional algorithm.     

我国城市流浪人员的救助管理与完善对策——以调研上海市救助管理现状为例

当前上海市在流浪人员救助管理过程中,还存在一些亟待解决的问题,主要体现在四个方面:对长期滞留人员安置困难,救助工作仍停留于表面问题的解决,救助管理的专业力量还比较缺乏,救助管理人员的职业风险比较大。基于此,建议:增加救助站的服务内容,把技能培训工作常态化,让流浪乞讨人员有学习知识的机会;提高救助管理人员的福利待遇,增强救助职业的吸引力;在大的临时性救助站附近增设警务站,方便突发性暴力事件得到及时处置;出台相应法规政策,逐步引导民间组织和人员参与救助工作。     

安徽中小企业发展现状及创新路径研究

近几年,在政府大力扶持之下,安徽中小企业快速发展,已成为推动经济持续、健康发展的重要力量,但在发展过程中也存在一些不容忽视的问题。本文从企业总量、地区分布、企业产值、所有制类型等方面对安徽中小企业进行调查,在此基础上分析安徽中小企业在发展过程中存在的问题,并提出相应的建议和对策,对丰富中小企业发展理论、制定安徽中小企业发展政策具有一定的意义。     

A novel spherical-ordered macroporous CuO nanocatalyst for the electrochemical reduction of carbon dioxide

Journal of Applied Electrochemistry - The electrocatalytic reduction of CO2 is a promising research direction in resource utilization and sustainable energy development. However, there is still a...     

Identification of intra-individual variation in intracranial arterial flow by MRI and the effect on computed hemodynamic descriptors

Magnetic Resonance Materials in Physics, Biology and Medicine - To determine the intra-individual flow variation in serially acquired studies, and the influence of this variation on subsequent...