破解太阳中微子失踪之谜

 2001至2003这3年时间里,太阳中微子的研究进入了一个黄金时期。在这个时期中,一个困扰了物理学家40年的难题被漂亮地解决了。这个难题的解决对于物理学和天文学来说都非常重要。本文将简要回顾3年来关于太阳中微子研究的惊人进展。太阳中微子的产生20世纪上半叶,物理学家们普遍相信太阳发光图1太阳内部的典型核聚变反应是由于其内部不断发生从氢到氦的核聚变反应。根据这一理论,在太阳内部每4个氢核(即质子)转化成1个氦核(4He)、2个正电子(e+)和2个神秘的中微子(νe),见图1所示。     

内部审核在计量体系中的作用

介绍内部审核制度在计量测试工作中的目的和作用，提出了内部审核工作应注意的事项，如内部审核工作计划的完整性，内部审核工作的有效性，管理者工作内容的全面性，以及后续工作的完善性。     

简析"静止液体内部压强公式验证"实验的设计策略

“静止液体内部压强公式验证”在现行教材中有两种实验方法。通过分析实验的设计策略，说明其作用、效果及操作上的困难，指出合理的与不合理诸因素，从而提出改进实验的方法，化难为易，提高实验教学效果。     

Bistable Behaviour of N Two-Level Atoms Interacting with the Field inside a High-Q Cavity Containing a Nonlinear Kerr-Like Medium

Taking the intensity-dependent coupling between atoms and cavity mode into account, we investigate a system consisting of N homogeneously broadened two-level atoms interacting with the field inside a single-mode Fabry- Perot cavity containing a nonlinear Kerr-like medium. We derive the steady-state bistable behaviour of the system, and further analyse in details the influence of several critical parameters on the bistable behaviour.     

Mindlin板几何非线性分析的附加内部剪应变法

本文在几何非线性分析的Ｍｉｎｄｌｉｎ板元中引入单元附加内部剪应变，有效地解决了薄板情况下的剪切自锁问题．文中导出了相应的能量相容条件，给出了有限元非线性列式的全过程及有关簿板及中厚板大挠度问题的数值结果．     

Diffusion of Acetic Acid Across Oil/Water Interface in Emulsification-Internal Gelation Process for Preparation of Alginate Gel Beads

Alginate has been widely used in cell microencapsulation and drug delivery systems in the form of gel beads or microcapsules.Although an alternative novel emulsification-internal gelation technology has been established and both the properties and the potential applications of the beads in drug delivery systems have been studied,the mechanism has not been well understood compared with the traditional droplet method(external gelation technology).On the basis of our previous knowledge that the novel technology is composed of complicatedly consecutive processes with multistep diffusion and reaction,and the diffusion of acetic acid across oil/water interface being the prerequisite that determines the occurrence and rate for the reactions and the structures and properties of final produced gel beads,a special emphasis was placed on the diffusion process.With the aid of diffusion modeling and simple experimental design,the diffusion rate constant and diffusion coefficient of acetic acid across oil/water interface were determined to be in the orders of magnitude of 10-6 and 10-16,respectively.This knowledge will be of particular importance in understanding and interpreting the formation,structure of the gel beads and the relationship between the structure and properties and guiding the preparation and quality control of the gel beads.     

硬木热解过程中颗粒内部二次反应的数值研究Ⅱ.数值模拟结果

为了研究生物质（硬木）热解过程中颗粒内部的二次反应，对流化床环境下单颗粒生物质热解模型进行了求解。计算针对典型大颗粒和典型小颗粒在流化床反应器反应条件下的热解过程，对不同大小颗粒内部各种产物的生成、消耗、积累以及逃逸行为进行了定量描述。计算结果表明：对于直径为2mm的小颗粒，颗粒内二次裂解的份额可以忽略，但是对于直径10mm的大颗粒，热争过程中有超过20%的一次焦油参加了颗粒内部二次反应，颗粒内二次裂解显著地改变了热解产物分布，改变了热解产物的品质。     

Theoretical Study of the Photochemical Reaction Mechanism of Bicyclo [4.1.0 ] heptane

IntroductionPhotochemical reactions, which involve a three-membered ring, have been of great interest to experi-mental photochemists[1—10]. A main reason for thisphenomenon is that the cyclopropane ring exhibits somereaction characteristics of double bon…     

点式模糊化拟一致结构诱导的双拓扑

引入点式模糊化拟一致结构u,并由其分别导出了模糊化内部算子和模糊化闭包算子,进而诱导两个模糊化拓扑(?)和η_u.结果表明,若u是点式模糊化拟一致结构,则T_u=η_u不一定成立;若u是点式模糊化一致结构,则(?)=η_u成立.     

U型通道内部流动与换热的数值研究

应用数值方法研究了燃气轮机叶片内部U型通道内流动与顶部换热特性.采用SST k-ω模型,分析了U型通道内光滑和带凹坑顶部结构以及不同Re数和旋转数对U型通道内部流动和顶部换热的影响。结果表明:在静止条件下,带凹坑结构的通道顶部Nu数较高,并且随着凹坑深度的增加,通道顶部换热能力增强;并且凹坑结构对通道压降的影响较小。随雷诺数增大,凹坑对通道顶部换热增强的幅度降低。在旋转状态下,随着旋转数的增加,通道顶部换热能力增强,但通道压降增大。