宇宙线研究在中国——纪念宇宙线发现100周年

今年是宇宙线发现100周年。本文回顾了宇宙线研究在中国的传入和发展历程,重点考察了我国早期留学物理学者的前沿工作、云南高山站的建立、宇宙线研究所的拟议和停办、高山乳胶室的发展,并简要论述了20世纪80年代以来的超高能现象研究和天体物理研究。宇宙线研究在中国的曲折历程是我国基础科学发展的缩影,科学知识扩展的需要是科学仪器和科学机构发展变化的内在动力。     

陕西南部生态移民减贫效应研究

陕西南部生态移民计划于2011—2020年实现240万人的移民搬迁,对其减贫效率进行定量评价,可为精准扶贫和移民减贫战略提供启示和借鉴。本文利用对陕西南部商洛、安康和汉中三市1032农户4年的平衡面板数据,采用农户陷入贫困的维度数和贫困剥夺得分为贫困代理变量,使用双重差分法、基于倾向得分匹配的双重差分法和固定面板效应回归方法,对陕西南部生态移民公共政策的减贫效应进行了评价。结果显示,陕西南部生态移民政策对迁移农户的减贫效应显著,高风险偏好和拥有更多外部机会的农户更容易脱贫。在后续的生态移民政策实施过程中,应着重培育产业发展,防止搬迁农户陷入收入贫困,同时,引导农户改变风险态度并提升自我发展能力,为农户提供更多的外部机会,使生态脆弱地区农户通过生态移民摆脱贫困。     

The variation of the residual ionization with pressure at different altitudes,and its relation to the cosmic radiation

Measurements have been made of the residual ionization in a closed vessel of steel one inch thick, shielded by a two inch casing of lead, over a range of pressure from atmospheric to one thousand pounds per sq. inch, at Pike's Peak (alt. 14,000 ft.), Colorado Springs (alt. 6,ooo ft.), and New Haven (alt. 6,000 ft.). The ionization-pressure curves presents features of interest in relation to the interpretation of the processes associated with ionization in the vessel. However, in the present investigation they are used simply to obtain average relative value of the ionization due to the cosmic rays at the three altitudes concerned. A method of correcting the observations for absorption by the iron sphere, the lead case, and the walls of the buildings, has been developed. It is found that the data for the three stations can be correlated by the assumption of a pair of frequencies in the original cosmic radiation; and, as a matter of fact, an infinite number of such pairs are possible. They are represented in graphical form in Fig. 7 If we permit the assumption of three different frequencies in the cosmic radiation, it is possible in general to assign two of the frequencies, and determine an infinite number of possibilities as regards the third, distributed over a definite range. The possibilities inherent in the assumption of three frequencies are contained in tabular form in Table XVII. Of course, the inclusion of observations from more than three altitudes would serve to fix more definitely the possibility as regards the analysis. However, the result of the analysis for the three stations concerned is possibly of interest for comparison with other data, and as an indication of the kind of information which it is possible to extract from observations of this kind. It is probable that the very large range of possibilities inherent in a solution with three coefficients of absorption will be rather surprising to anyone who considers a situation of this kind for the first time.In addition to those whose assistance has already been acknowledged, I wish to acknowledge the assistance of Professor J. W. Broxon, who visited me while on Pike's Peak, and assisted in setting up the apparatus; and my thanks are due to Mr. C. A. Kotterman, and particularly to Mr. Andrew Longacre, and Mr. W. E. Ramsey for assistance in the reduction of the observations, and in the computational work.     

双波段红外参比技术在水分检测和控制中的应用

文章利用水在一定的红外辐射波段里具有的特定吸收机理,采用双波段红外参比技术,开发了一种水分在线检测和控制装置,对半成品药物进行在线检测水分;同时采用Smith 预估法解决了控制的滞后问题.通过实验证明该检测方法有效,装置可靠、稳定,并且满足了控制精度的要求,使用效果良好,具有较大的推广价值.     

Voltage-induced penetration effect in liquid metals at room temperature

Room-temperature liquid metal is discovered to be capable of penetrating through macro- and microporous materials by applying a voltage. The liquid metal penetration effects are demonstrated in various porous materials such as tissue paper, thick and fine sponges, fabrics, and meshes. The underlying mechanism is that the high surface tension of liquid metal can be significantly reduced to near-zero due to the voltage-induced oxidation of the liquid metal surface in a solution. It is the extremely low surface tension and gravity that cause the liquid metal to superwet the solid surface, leading to the penetration phenomena. These findings offer new opportunities for novel microfluidic applications and could promote further discovery of more exotic fluid states of liquid metals.