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51.
We design a continuous-wave Tm:YLF laser with a composite slab crystal end-pumped by two fiber-coupled laser diodes at room temperature. We achieve a maximum continuous wave output power of 105 W for the bonded slab Tm:YLF laser; the corresponding slope efficiency is 47.7% and the optical-to-optical conversion efficiency is 42.0% with respect to the incident pump power. The laser operated at 1,907.5 nm with a beam quality factor of M2 3.2 at the highest output power.  相似文献   
52.
ABSTRACT

A new catalytic kinetic fluorescent quenching method for the determination of trace gold(III) was investigated. The method was based on the catalytic effect of gold on oxidation of 3-(3′-methylphenyl)-5- (2′-arsenoxylphenylazo) rhodanine by hydrogen peroxide in potassium hydrogen phthalate–hydrochloric acid (pH = 3.4). Under the optimum conditions, the great decrease of fluorescence intensity has a linear relationship against the concentration of gold in the range of 0 to 12.0 µg·L?1 with a detection limit of 6.0 × 10?10g·L?1. The coexistent metal ions can be separated, and gold can be enriched by TBP resin of solid-phase extraction, which greatly improves the selectivity and sensitivity of the system. The method can be used to determine trace amounts of gold in ore samples successfully with satisfactory results.  相似文献   
53.
The DAMA project is an observatory for rare processes and it is operative deep underground at the Gran Sasso National Laboratory of the I.N.F.N. In particular, the DAMA/LIBRA (Large sodium Iodide Bulk for RAre processes) set-up consists of highly radiopure NaI(Tl) detectors for a total sensitive exposed mass of ?250 kg. Recent results, obtained by this set-up by exploiting the model independent annual modulation signature of Dark Matter (DM) particles, have confirmed and improved those obtained by the former DAMA/NaI experiment. A model independent evidence for the presence of Dark Matter particles in the galactic halo is cumulatively obtained at 8.2?σ C.L. No systematics or side reactions able to account for the measured modulation amplitude and to contemporaneously satisfy all the many specific requirements of the signature have been found or suggested by anyone over more than a decade. An example of one of the many possible model dependent corollary quests for the candidate particles and for the related astrophysical, nuclear and particle physics scenarios is presented considering the whole cumulative exposure. Future perspectives are shortly addressed.  相似文献   
54.
Dai Y  Yao J 《Optics letters》2008,33(4):390-392
We propose a novel technique to implement arbitrary pulse shaping of an ultrashort pulse by intensity-only modulation in the frequency domain. The intensity-only modulation is realized by nonuniformly spaced sampling in the frequency domain. By properly designing the sampling function, multiple pulses in the time domain will be generated with one of which being the desired waveform. The desired waveform is then selected by a time window. Both the optical amplitude and phase distributions of the output waveform can be controlled. Theoretical analysis is presented. An example showing the generation of a rectangular pulse is provided.  相似文献   
55.
曹斓  阎晓娜  戴晔  杨希华 《光学学报》2012,32(6):609001-53
在Mazurenko提出的时域超短脉冲光谱全息结构的基础上,提出了改进型的飞秒脉冲光谱全息结构,并推导了当输入脉冲光场中包含时、空分布时光谱全息的记录和再现.结果发现当在光谱全息记录和再现时,如果频谱面上添加空间滤波器,可以实现飞秒脉冲包含的空域信息向时域信息的转换.结论可以应用到超短脉冲整形,超高速光通信和光信息处理等领域.  相似文献   
56.
    
We propose randomized inference(RI), a new statistical inference approach. RI may be realized through a randomized estimate(RE) of a parameter vector, which is a random vector that takes values in the parameter space with a probability density function(PDF) that depends on the sample or sufficient statistics,such as the posterior distributions in Bayesian inference. Based on the PDF of an RE of an unknown parameter,we propose a framework for both the vertical density representation(VDR) test and the construction of a confidence region. This approach is explained with the aid of examples. For the equality hypothesis of multiple normal means without the condition of variance homogeneity, we present an exact VDR test, which is shown as an extension of one-way analysis of variance(ANOVA). In the case of two populations, the PDF of the Welch statistics is given by using the RE. Furthermore, through simulations, we show that the empirical distribution function, the approximated t, and the RE distribution function of Welch statistics are almost equal. The VDR test of the homogeneity of variance is shown to be more efficient than both the Bartlett test and the revised Bartlett test. Finally, we discuss the prospects of RI.  相似文献   
57.
本文对食饵种群具有常数放养率、捕食者种群具有常数收获率且具有Holling第一类功能性反应的捕-食系统进行了定性分析,得到了存在分界线环和六个单侧极限环的条件。  相似文献   
58.
戴宗武 《大学物理》1998,17(10):21-22
利用磁壳与线形闭合电流等效的证明方法,可避开使用矢量分析工具,一般地证明恒磁场安培环路定理。  相似文献   
59.
Guanine radicals are important reactive intermediates in DNA damage. Hydroxyl radical (HO.) has long been believed to react with 2′-deoxyguanosine (dG) generating 2′-deoxyguanosin-N1-yl radical (dG(N1-H).) via addition to the nucleobase π-system and subsequent dehydration. This basic tenet was challenged by an alternative mechanism, in which the major reaction of HO. with dG was proposed to involve hydrogen atom abstraction from the N2-amine. The 2′-deoxyguanosin-N2-yl radical (dG(N2-H).) formed was proposed to rapidly tautomerize to dG(N1-H).. We report the first independent generation of dG(N2-H). in high yield via photolysis of 1 . dG(N2-H). is directly observed upon nanosecond laser flash photolysis (LFP) of 1 . The absorption spectrum of dG(N2-H). is corroborated by DFT studies, and anti- and syn-dG(N2-H). are resolved for the first time. The LFP experiments showed no evidence for tautomerization of dG(N2-H). to dG(N1-H). within hundreds of microseconds. This observation suggests that the generation of dG(N1-H). via dG(N2-H). following hydrogen atom abstraction from dG is unlikely to be a major pathway when HO. reacts with dG.  相似文献   
60.
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