非球谐振子势的精确解

严格求解了三维非球谐振,势的Schrodinger方程给出了精确的能谱方程和归一化的径向波函数.获得了径向幂次算符r^s的矩阵元和平均值的计算公式及其递推关系.     

A Nanometer Aerosol Size Analyzer (nASA) for Rapid Measurement of High-concentration Size Distributions

We have developed a fast-response nanometer aerosol size analyzer (nASA) that is capable of scanning 30 size channels between 3 and 100 nm in a total time of 3 s. The analyzer includes a bipolar charger (Po²¹⁰), an extended-length nanometer differential mobility analyzer (Nano-DMA), and an electrometer (TSI 3068). This combination of components provides particle size spectra at a scan rate of 0.1 s per channel free of uncertainties caused by response-time-induced smearing. The nASA thus offers a fast response for aerosol size distribution measurements in high-concentration conditions and also eliminates the need for applying a de-smearing algorithm to resulting data. In addition, because of its thermodynamically stable means of particle detection, the nASA is useful for applications requiring measurements over a broad range of sample pressures and temperatures. Indeed, experimental transfer functions determined for the extended-length Nano-DMA using the tandem differential mobility analyzer (TDMA) technique indicate the nASA provides good size resolution at pressures as low as 200 Torr. Also, as was demonstrated in tests to characterize the soot emissions from the J85-GE engine of a T-38 aircraft, the broad dynamic concentration range of the nASA makes it particularly suitable for studies of combustion or particle formation processes. Further details of the nASA performance as well as results from calibrations, laboratory tests and field applications are presented below.     

Optimizing phase imaging via dynamic force curves

Tapping mode (TM, also called intermittent contact mode) atomic force microscopy (AFM) has been routinely used in many laboratories. However, consistent or deliberate control of measuring conditions and interpretation of results are often difficult. In this article, we demonstrate how measurement parameters (drive frequency, cantilever stiffness and oscillation amplitude) affect the tapping tip's state. This has been done by systematic dynamic force measurements performed on mica and polystyrene surfaces together with computer simulations. Our study shows the following results. (1) Weaker cantilevers, smaller amplitude and higher drive frequency (around the resonance) lead to an extension of the attractive region (greater phase lag) in amplitude–phase–distance curves and thus can help to achieve stable high-setpoint TM imaging with minimal tip–sample pressure. (2) Bistability of tapping tips often exists and may cause height artefacts if the setpoint falls in the bistable region. (3) Tapping tips with high vibrating energy (stiff cantilevers and large amplitude) driven at resonance are only slightly perturbed by tip–sample interactions and usually remain monostable during the sweep of the scanner position. This can help to achieve good phase contrast without significant artefacts when the setpoint falls in a continuous negative–positive phase shift transition region. (4) Low energy cantilevers (compliant cantilevers and small amplitude) usually result in large phase shift and can be used to acquire large phase contrast images. However, height artefacts will occur when the setpoint falls in the bistable region usually existing for such cantilevers. (5) Computer simulations are useful in understanding the bistability in dynamic force curves and determining either material properties or the optimal imaging parameters.     

恒流法测定热扩散系数

介绍了一种准确测定材料热扩散系数和导热系数 的方法－恒流法,该方法使用的仪器设备简单,测度时间短,准确度高,复现性好,适合于作学生分组实验,也宜于在生产实践和科学研究中广泛推广应用。     

Method for calculating the complete expansion of the Glauber amplitude for nucleus-nucleus scattering

A method for calculating the complete expansion of the Glauber amplitude for nucleus-nucleus scattering processes is proposed. An example of the calculation of the elastic differential cross section is given as an illustration.     

Transmission Characteristics of 90° Bent Photonic Crystal Waveguides

There are several key factors that affect the transmission characteristics of the 90° (L-shaped) bent photonic crystal waveguides. The first factor is the direct coupling efficiency from the incident lights into the waveguides. The second one is the bandgap deviations of the photonic crystals. And the third factor is the optical reflections in the bent corners. In this article, we compare three types of L-shaped bent photonic crystal waveguides. One is the original type, which has an abrupt right-angle bend. Another is an improved 90° bend with a 45°-mirror. The other is an L-shaped bent photonic crystal waveguide with a 45°-transitional section. We investigate their respective frequency responses and observe the improvements in the total transmission efficiencies provided by the latter types.     

Two-photon pumping of random lasers by picosecond and nanosecond lasers

We experimentally demonstrated two-photon pumping of random lasers using picosecond and nanosecond pump lasers. The picosecond laser pumping experiment was performed with 400 ps laser pulses at 770 nm, and the gain media was a Coumarin 480D dye solution doped with TiO₂ nanoparticles. Onset of laser action was observed at a pump laser pulse energy below 500 μJ. The nanosecond laser pumping experiment was performed with 7 ns laser pulses at 1064 nm, and the gain media was a Rhodamine 640 dye solution doped with TiO₂ nanoparticles. Onset of laser action was observed at a pump laser energy ∼18 mJ. Our results suggest that there exists an optimal pulse duration of the pumping laser in two-photon pumped random lasing that leads to minimum photodamage of the gain media and still keeps a high pumping efficiency. PACS 33.50.Dq; 42.55.Mv; 42.55.Zz     

Measurement of underground motion at the SSRF site

For the Shanghai Synchrotron Radiation Facility (SSRF) and future Shanghai Free‐Electron Laser projects, ground vibration is an important factor and, in order to attenuate it, the construction of a deep tunnel is under consideration. This paper concentrates on the investigation of ground vibration at different underground levels down to 60 m below surface, in order to understand the effect of vibration attenuation with depth. The effect of traffic is also studied using a 10 ton truck, with ground motion compared in different directions. Finally, a summary and some suggestions on these two projects are given.