投资者概念关注对股票收益的影响研究—基于百度搜索数据

我国股票市场存在明显的概念炒作现象,扭曲了市场的良性定价机制。本文基于有限注意视角揭示投资者概念关注对股票收益的影响机制,使用百度搜索数据衡量投资者概念关注,以“一带一路”、“5G”和“PM2.5”概念板块的股票为研究样本进行实证研究。结果表明:在控制了Fama-French三因素以及投资者个股关注情况下,投资者概念关注对所属概念板块的股票收益有显著正向影响,但这种影响作用会在随后几期反转为负向影响。投资者个股关注一方面会强化投资者概念关注对股票收益的正向影响,另一方面投资者个股关注越高,个股的流动性就越强,从而会弱化投资者概念关注对股票收益影响作用的反转效应。研究结论丰富了投资者关注的理论研究,为抑制概念炒作提供理论依据和实现途径。     

2D Catalysts for CO2 Photoreduction: Discussing Structure Efficiency Strategies and Prospects for Scaled Production Based on Current Progress

Currently, the excessive consumption of fossil fuels is accompanied by massive emissions of CO₂, leading to severe energy shortages and intensified global warming. It is of great significance to develop and use renewable clean energy while reducing the concentration of CO₂ in the atmosphere. Photocatalytic technology is a promising strategy for carbon dioxide conversion. Clearly, the achievement of the above goals largely depends on the design and construction of catalysts. This review is mainly focused on the application of 2D materials for photocatalytic CO₂ reduction. The contribution of synthetic strategies to their structure and performance is emphasized. Finally, the current challenges, and prospects of 2D materials for photoreduction of CO₂ with high efficiency, even for practical applications are discussed. It is hoped that this review can provide some guidance for the rational design, controllable synthesis of 2D materials, and their application for efficient photocatalytic CO₂ reduction.     

Diastereomeric isomerization of Fischer's base analogs of LTAM molecules in organic solvents: mechanistic investigation

Three possible mechanistic routes for the diastereomeric isomerization of the leuco-triarymethane (LTAM) molecules have been proposed, depending on the formal breaking of the carbon-carbon double bond via either heterolytic, homolytic or molecula splitting/reassembling.     

Numerical simulation of the modulated flow pattern for vertical upflows by the phase separation concept

The multiphase heat transfer could be enhanced by creating thin liquid film on the wall. The phase separation concept is called due to the separated flow paths of liquid and gas over the tube cross section to yield thin liquid film. Our proposed heat transfer tube consists of an annular region close to the wall and a core region, interfaced by a suspending mesh cylinder in the tube. The heat transfer tube is a multiscale system with micron scale of mesh pores, miniature scale of annular region and macroscale of tube diameter and length. Great effort has been made to link from micron scale to macroscale. The Volume of Fluid (VOF) method simulates air/water two-phase flow for vertical upflow. The three-dimensional system was successfully converted to a two-dimensional one by using three equivalent criteria for mesh pores. The non-uniform base grid generation and dynamic grid adaption method capture the bubble interface. The numerical results successfully reproduce our experimental results. The numerical findings identify the following mechanisms for the enhanced heat transfer: (a) counter-current flow exists with upward flow in the annular region and downward flow in the core region; (b) void fractions are exact zero in the core region and higher in the annular region; (c) the liquid film thicknesses are decreased to 1/6–1/3 of those in the bare tube section; (d) the gas–liquid mixture travels much faster in the annular region than in the bare tube; (e) three-levels of liquid circulation exists: meter-scale bulk liquid circulation, moderate-scale liquid circulation around a single-elongated-ring-slug-bubble, and microliquid circulation following the ring-slug-bubble tails. These liquid circulations promote the fluid mixing over the whole tube length and within the radial direction. The modulated parameters of void fractions, velocities and liquid film thicknesses in the annular region and three-levels of liquid circulation are greatly beneficial for the multiphase heat transfer enhancement.     

化学与非致命武器

非致命武器逐渐发展成为一类重要的武器装备。目前非致命武器通常是指可以在不导致人员死亡或大量死亡及设备严重毁坏,对环境破坏程度较小的情况下,实现特定军事或某些非军事目的的武器。这些非致命武器在高技术局部战争和一些特定的反恐怖或维和行动中具有广阔的应用前景。     

Construction of a geometrical concept within a dialectical learning environment

The goals of the study were to design and investigate a teaching-learning environment that encourage freedom and autonomy of pre-service teachers in constructing their own new geometrical concept, and to analyze the dialectic process of the concept construction in the designed environment. A dialectic process of the participants’ defining activity emerged from the necessity to resolve the tensions between hypothesizing the concept’s examples and the appropriate critical attributes. Such a process created a vivid learning trajectory, in which learners examined logically the ways in which the examples, the critical attributes and the definition match. In this way, the three elements of the mathematical concept cannot play a passive role, or be neglected, and it appeared that prototypical examples were not created, so that no example is more dominant than others. The groups constructed different concepts, but with full harmony between its definition, example space, and concept-critical attributes.     

Demonstration of Automated Adjustment and Coupling of Fiber Array to PICs Based on the Detection of Edges

ABSTRACT

Progress in integrated photonics enables development of photonics integrated circuits (PIC) with new unique properties and overcomes current limits in information and communication technologies. The effective coupling of optical radiation between telecom optical fiber and photonic integrated circuits is necessary. To address these challenges, we present our concept of photonics integrated circuit (PIC) fully customized packaging with microwave, direct current, and fiber array ports with automated active alignment system. Automated adjustment and coupling of single-mode fiber (SMF) arrays with 8 fibers to PIC based on the detection of edges and markers on PIC and SMF arrays were successfully realized.     

一个综合QFD技术的概念阶段装备成本估算方法

提出了一种基于性能特点和质量功能展开(QFD)技术的装备成本估算方法,可用于概念设计阶段进行准确的费用估算.应用QFD技术分析得出费用估算所需信息,并利用最小二乘法得出装备成本估算所需费用因子后结合预研装备的的性能值可计算出装备成本.最后通过实例对该方法进行了演示,并给出在不同预算下装备研制成功的概率.     

Broad band antireflection coating on zinc sulphide simultaneously effective in SWIR, MWIR and LWIR regions

In recent years multi-spectral imagery is steadily growing popularity. Multi-channel imaging which includes short-wave infrared (SWIR), mid-wave infrared (MWIR) and long-wave infrared (LWIR) systems are useful for threat detection, tracking, thermal signature detection and terrain analysis. In this paper, a broad band antireflection coating on ZnS substrate, simultaneously effective in SWIR, MWIR and LWIR is reported. The coating design approach was evolved using gradient index concept, where refractive index varies gradually from incident media to the ZnS (n = 2.2) substrate. The gradient index profile depicted by 4th degree polynomial n(t) = −0.45t⁴ + 1.9t³ − 2.7t² + 1.9t + 1,where n(t) is the refractive index at the distance t from ambient, and t is the thickness in micron. The profile is best approximated by eight discrete step index layers, whose first layer is thorium fluoride (n = 1.42; lowest index stable material available). Other seven layers are replaced by two equivalent layer system of real materials thorium fluoride and zinc sulphide. Final 15 layers design is deposited by e-beam evaporation. The maximum layer thickness was restricted around 0.7 μm to overcome the stress problem in the film. This 15 layers coating has shown average transmission 95% in 0.9–10.5 μm spectral band having peak 99% at 9 μm.     

药片与模糊集

根据概念原理举例说明模糊集取大取小运算的不完备性,即词不达意的问题.