A new route to fabricate large-area, compact Ag metal mesh films with ordered pores

Ordered Si nanowire (SiNW) arrays can be fabricated by metal-assisted chemical etching. The metal mesh films (MMFs) are extremely important for achieving a high quality of the SiNWs. We have developed a two-step chemical deposition method to obtain compact porous Ag MMFs. By the separation of the nucleation and growth stages of the metal in the two-step deposition processes, the overgrowth of the metals to form randomly aggregated irregular metal particles can be overcome. Hexagonally arranged polystyrene (PS) latex microspheres have been employed as a template for the deposition of porous Ag MMFs. The spacing of the pores in the Ag MMFs is determined by the diameter of PS microspheres, and the pore size can also be tuned by changing Ar plasma etching time. One of the main advantages of the two-step deposition method lies in that Ag MMFs can be produced with PS microspheres that are not limited to a single layer, which dramatically simplifies the tedious processes of producing a monolayered PS template. The two-step chemical deposition method shows great potential in metal-assisted chemical etching.     

大气湍流像差对空间零差二进制相移键控相干光通信误码性能的影响

通过研究不同大气湍流条件下的系统误码率(BER)来说明大气湍流引起的波前畸变给零差二进制相移键控(BPSK)相干光通信系统带来的恶劣影响。结果显示,大气湍流引起的像差可以独立于系统信噪比(SNR)作用于相干光通信系统,导致误码出现。即使在SNR无限大的情况下,当接收光信号的波面峰谷值(PV)大于一个波长后,就容易出现误码;并且随着SNR的降低,对波面PV的要求更加严格。另外,大气湍流引起的光强起伏和相位畸变会导致相干混频效率急剧下降,从而增加系统误码率。     

Supercapacitor electrodes with especially high rate capability and cyclability based on a novel Pt nanosphere and cysteine-generated graphene

In the present work, supercapacitors based on graphene/Pt films show especially high rate capability (120 F g(-1) even at 50 A g(-1)) and cyclability (no attenuation over 10,000 cycles) and peculiar nanosphere morphology after electrochemical cycling. Furthermore, supercapacitors based on the graphene powder with a binder exhibit high specific capacitance (249 F g(-1) at 0.1 A g(-1)), long cycle life (no attenuation over 40,000 cycles) and high rate capability (150 F g(-1) even at 50 A g(-1)), which are much better than those of most graphene electrode materials. These indicate the great potential of the cysteine reduced graphene electrodes in energy storage.     

Coherent beam combination of an optical array using adaptive fiber optics collimators

A novel adaptive-fiber-optics-collimator (AFOC) compensating both piston-type and tip/tilt-type phase errors of output beam is introduced, and has been employed in experiments of coherent beam combination (CBC) of a delta distributed fiber array. Feedback control is realized using stochastic parallel gradient descent (SPGD) algorithm. Excellent CBC effect has been achieved when piston and tip/tilt errors among beamlets corrected. The necessity of wavefront tip/tilt control in CBC is verified. Experimental results exhibit great potential applications of this kind of AFOC in fiber amplifier arrays.     

含硝基胍E-β-法尼烯类似物的合成及生物活性研究

以蚜虫报警信息素的主要成分E-β-法尼烯(E-β-farnesene,简称EBF)为先导,分别用不同取代硝基胍替代EBF中的共轭双键,设计合成了10个未见文献报道的EBF类似物,其结构均经1HNMR,IR和HRMS分析确证,并对化合物的生物活性进行了测试,分析比较了不同取代硝基胍的生物活性差异.生物活性试验结果表明,目标化合物对桃蚜(Myzus persicae)均具有一定的生物活性,其中化合物9a～9e的活性优于E-β-法尼烯.     

Accuracy analysis on centroid estimation algorithm limited by photon noise for point object

The variance of the position of point object because of photon noise for centroid estimation algorithm is derived for the first time when the background cannot be eliminated by threshold. On this foundation, the accuracy of centroid estimation algorithm is analyzed by comparing its estimated efficiency (the ratio of the Cramer-Rao lower bound of point object and the variance for centroid algorithm) based on the classic estimation theory. The results indicated that the following factors influence the accuracy of centroid estimation algorithm: SBR (the ratio of the outputs from the signal light and the background), the Gaussian width of signal spot and the size of detected window. The effects of these factors are also described.     

Bit-error rate for free-space optical communication with tip-tilt compensation

In this paper, a new kind of method is developed to analyse the bit-error rate for a free-space optical communication system, which is based on the three most important parameters of scintillation statistics, i.e. fraction of time of fade and surge, mean frequency of level crossings, and mean duration of fade and surge. By using this method, the relationship between the bit-error rate and scintillation is clearly identified. The tip-tilt error deteriorates the performance of a free-space optical communication system. Fine tracking ability of adaptive optics (through tip-tilt compensation) can overcome this difficulty. The fade and surge statistical parameters with tip-tilt compensation are evaluated for the plane wave model. The bit-error rate as a function of the scintillation statistical parameters (with tip-tilt compensation) is developed. The results show that the bit-error rate is reduced notably through tip-tilt compensation for free-space optical communication.     

利用倾斜镜对太阳像作平场处理

提出一种利用高速倾斜反射镜对太阳像进行平场处理的新方法。介绍了此方法的原理和实际工作过程，并给出了实验结果。结果表明，应用高速倾斜反射镜可以非常有效地对太阳像进行平场处理，提高太阳像成像质量。