用单摆测重力加速度的不确定度评定

本文根据国际、国内有关不确定度应用办法的规定，对用单摆测重力加速度的实验进行了详细的不确定度分析。     

模拟函数法测定重力加速度

模拟函数法测重力加速度是针对传统的重力加速度测定中没有考虑空气阻力影响而采用的一种新型方法。本文采用此法测定了当地的重力加速度，得到了较满意的效果。     

Is the Pioneer Anomaly a Counter Example to the Dark Matter Hypothesis?

The Hubble law is extended to massive particles based on the de Broglie wavelength. Due to the expansion of the universe the wavelength of an unbound particle would increase according to its cosmological redshift. Based on the navigation anomalies of the Pioneer 10 & 11 spacecraft it is postulated that an unbound massive particle has a cosmological redshift z=(c/v ₀)H ₀ t, where c is the speed of light in vacuum, v ₀ is the initial velocity of the particle, H ₀ is Hubble’s constant and t is the duration of time that the particle has been unbound. The increase in wavelength of the particle corresponds to a decrease in its speed by Δv=−cH ₀ t. Furthermore, it is hypothesized that the solar system has escaped the gravity of the Galaxy as evidenced by its orbital speed and radial distance and by the visible mass within the solar system radius. This means that spacecraft which become unbound to the solar system would also be galactically unbound and subject to the Hubble law. This hypothesis and the extended Hubble law may explain the anomalous acceleration found to be acting upon the unbound Pioneer 10 & 11 spacecraft. Thus, the Pioneer anomaly may be a counter example to the dark matter hypothesis. Because photons have a speed which make them unbound to the Galaxy, it is predicted that the navigation beam in open space would undergo a cosmological redshift in its frequency which would be detectable with modern clocks.     

基于衍射微透镜的光学加速度传感器设计

提出了一种基于菲涅耳衍射微透镜的新型光学加速度传感器,它能够解决导航系统中惯性传感器普遍存在的抗电磁干扰和电磁冲击能力差等缺陷。其传感原理是把一个反光膜平行地置于衍射微透镜的后方,加速度的变化会改变反光膜的位置,根据微透镜前方会聚点处光强的变化,感知加速度的大小。介绍了传感器及其动力学系统的工作原理,并对衍射微透镜和动力学系统的微弹性机械结构进行了设计和加工,最后对传感器的性能和误差进行了分析。原理验证性实验的结果表明这种新型光学加速度传感器的原理正确,并且结构简单,灵敏度高。     

对"拉船靠岸"习题的教学思考

通过对一道习题的教学处理，让学生在解答中体会解决问题的一般方法．     

“一锅”三组分合成新型1,5-苯并二氮杂䓬类化合物与抗牛病毒性腹泻病毒(BVDV)活性

以特氨酸、邻苯二胺和芳香醛为原料,乙醇为溶剂,对甲苯磺酸为催化剂,多组分一锅法构建了一系列含有吡咯烷酮的1,5-苯并二氮杂?类化合物.该方法反应条件温和,操作简单,产物收率高.探索了抗牛病毒性腹泻病毒(BVDV)病毒活性,结果显示合成的苯二氮?类衍生物具有显著的抗BVDV活性,EC₅₀值好,且无明显的细胞毒性,为抗BVDV制剂的研究提供了有意义的参考物.     

采用双层靶提高激光薄膜相互作用中加速质子的产额

 在激光等离子体相互作用实验中测量到的加速质子,来源于薄膜靶表面的碳氢沾染物。为了提供稳定充足的质子源,设计一种新的复合靶,在2.5 μm塑料溅射200 nm 金薄层形成双层靶,并在中等强度激光功率密度下开展研究,采用磁谱仪和CR-39探测器测量得到其能谱,结果表明：双层靶结构能够有效地增加质子的产额,并可能改善加速质子束的单能性。     

Rate Acceleration of the Baylis‐Hillman Reaction within Microreactors

Based on microreactors, the representative Baylis‐Hillman reaction of cyclopent‐2‐enone coupled with 4‐nitrobenzaldehyde in the presence of imidazole could be accelerated by manipulating the temperature and electric field. Furthermore, the electric field was used in promoting Baylis‐Hillman reaction for the first time with the rate acceleration approximately 5.2‐fold higher than that carried out in conventional vessels as well as 4.0‐fold under control of temperature. Meanwhile, the products of Baylis‐Hillman reaction at every time point could be collected and then determined by capillary micellar electrokinetic chromatography.     

An expeditious and greener one-pot synthesis of 4H-chromenes catalyzed by Ba(OTf)2 in PEG-water

Abstract

An expeditious synthesis of 4H-chromenes has been achieved by three-component one-pot condensation of 1,3-diketone, aldehyde, and malononitrile using Ba(OTf)₂ as catalyst in PEG-water at room temperature. Results from various reaction media and different metal triflates as catalysts show that choice of proper catalyst and the solvent system play a key role in the synthesis of 4H-chromene-3-carbonitrile derivatives. The catalyst can be recovered and reused at least five times without loss of activity. The application of an eco-friendly, noncorrosive, and reusable catalytic system with high isolated yield of the products makes this method advantageous.