Two New and a Known Compound from Lawsonia inermis

A new obtusafuran derivative, lawsonicin ( 1 ), and a new naphthaquinone, lawsonadeem ( 2 ), along with a known constituent, vomifoliol ( 3 ), were isolated from the aerial parts of Lawsonia alba and characterized by chemical transformation and spectroscopic experiments, including 2D‐NMR techniques.     

原子相干态中的压缩现象

计算表明,与场的相干态类似的原子相干态,具有不同于场的相干态的压缩行为;进一步证明:直接类比于(?)(ξ)不能得到“原子压缩算符”.     

光学双稳性临界点的相变行为

本文详细地讨论了光学双稳性(OB)的临界现象。理论分析主要以忽略量子涨落的Fokker-Plank方程的静态解为基础。结果发现,OB的临界现象可以纳入Landau二级相变理论的框架,并且有关临界指数之间的关系也服从标度律。 关键词：     

Structural,morphological and mechanical properties of niobium nitride thin films grown by ion and electron beams emanated from plasma

The influence of variation in plasma deposition parameters on the structural, morphological and mechanical characteristics of the niobium nitride films grown by plasma-emanated ion and electron beams are investigated. Crystallographic investigation made by X-ray diffractometer shows that the film synthesized at 10?cm axial distance with 15 plasma focus shots (PFS) exhibits better crystallinity when compared to the other deposition conditions. Morphological analysis made by scanning electron microscope reveals a definite granular pattern composed of homogeneously distributed nano-spheroids grown as clustered particles for the film synthesized at 10?cm axial distance for 15 PFS. Roughness analysis demonstrates higher rms roughness for the films synthesized at shorter axial distance and by greater number of PFS. Maximum niobium atomic percentage (35.8) and maximum average hardness (19.4?±?0.4?GPa) characterized by energy-dispersive spectroscopy and nano-hardness analyzer respectively are observed for film synthesized at 10?cm axial distance with 15 PFS.     

Charge Transport and Magnetotransport Properties of Polyimide Irradiated by 80keV Co Ions

Charge transport properties of polyimide films implanted with 80 keV Co ions at two different fluences （series I： 1.25 × 10^17 ions/cm^2, series Ⅱ： 1.75 × 10^17 ions/cm^2） are studied in detail. For series I, the temperature dependence of surface resistivity fits Mott＇s equation very well. It is on the insulating side of the insulator-metal transition （IMT）. However, for series Ⅱ, the temperature dependence of surface resistivity is not in agreement with Mott＇s equation. It is on the metallic side of lMT. The magnetotransport properties of these two series are also studied. No significant magnetoresistive effect is observed for series I at both 5 K and 300 K. For series Ⅱ, an obvious magnetoresistive effect is observed at 5 K, while there is no magnetoresistive effect at 300 K. Rutherford backscattering spectrometry （RBS） is applied to confirm the actual fluence for these two series.     

Optimized K-means (OKM) clustering algorithm for image segmentation

This paper presents the optimized K-means (OKM) algorithm that can homogenously segment an image into regions of interest with the capability of avoiding the dead centre and trapped centre at local minima phenomena. Despite the fact that the previous improvements of the conventional K-means (KM) algorithm could significantly reduce or avoid the former problem, the latter problem could only be avoided by those algorithms, if an appropriate initial value is assigned to all clusters. In this study the modification on the hard membership concept as employed by the conventional KM algorithm is considered. As the process of a pixel is assigned to its associate cluster, if the pixel has equal distance to two or more adjacent cluster centres, the pixel will be assigned to the cluster with null (e. g., no members) or to the cluster with a lower fitness value. The qualitative and quantitative analyses have been performed to investigate the robustness of the proposed algorithm. It is concluded that from the experimental results, the new approach is effective to avoid dead centre and trapped centre at local minima which leads to producing better and more homogenous segmented images.     

Generation of 287 W, 5.5 ps pulses at 78 MHz repetition rate from a cryogenically cooled Yb:YAG amplifier seeded by a fiber chirped-pulse amplification system

We generate linearly polarized, 287 W average-power, 5.5 ps pulses using a cryogenically cooled Yb:YAG amplifier at a repetition rate of 78 MHz. An optical-to-optical efficiency of 41% is obtained at 700 W pump power. A 6 W, 0.4 nm bandwidth picosecond seed source at 1029 nm wavelength is constructed using a chirped-pulse fiber amplification chain based on chirped volume Bragg gratings. The combination of a fiber amplifier system and a cryogenically cooled Yb:YAG amplifier results in good spatial beam quality at large average power. Low nonlinear phase accumulation as small as 5.1 x 10(-3) rad in the bulk Yb:YAG amplifier supports power scalability to a > 10 kW level without being affected by self-phase modulation. This amplification system is well suited for pumping high-power high-repetition-rate optical parametric chirped-pulse amplifiers.