Ultra-low frequency passive vertical vibration isolation system

An ultra-low frequency passive vertical vibration isolator is constructed by mounting a couple of additional masses on the crank-arms of the torsion spring. The theoretical analysis and experimental results show that the system with additional masses can achieve better vertical vibration isolation and longer resonant period. Measured displacement response of the test mass under seismic excitation reaches 3 x 10^{-12 m/√ Hz} around 10 Hz, and the isolation ratio comes to about 60 dB attenuation at 6 Hz, which is about 30 dB lower than that of the system without additional masses. Project supported by the National Natural Science Foundation of China (Grant Nos. 19425008, 49674246 and 59678032).     

网络智能可视自动化运维的有效对策

信息技术的不断发展,对网络运维工作提出了更高的要求。利用现代技术来提升网络智能可视自动化运维水平,能有效解决故障感知难、故障定位难、故障恢复慢等问题。文中从网络智能可视自动化运维的优势出发,阐述了网络智能可视自动化运维的关键技术,从数据中心、业务系统、宽带微服务、移网微服务、网络运行管控等方面,提出了优化网络智能可视自动化运维的有效措施。     

Synthesis, nonlinear optical properties and the possible mechanism of photopolymerization of two new two-photon absorption chromophores

Efficient Witting and Pd-catalyzed Heck coupling methodologies are employed to synthesize two new two-photon free-radical photopolymerization initiators 9-ethyl-3-{2-[4-(2-pyridin-4-yl-vinyl)-phenyl]-vinyl}-9H-carbazole (abbreviated to EPVPC) and 9-octadecyl-3-{2-[4-(2-pyridin-4-yl-vinyl)-phenyl]-vinyl}-9H-carbazole (abbreviated to OPVPC). The experimental results confirm that the two compounds are good two-photon absorbing chromophores and operative two-photon photopolymerization initiators. The calculated two-photon absorption cross-sections of EPVPC and OPVPC are 56.6 and 62.0×10⁻⁵⁰ cm⁴ s photon⁻¹, respectively. A microstructure by using EPVPC as initiator has been fabricated under irradiation of 200 fs, 76 MHz Ti:sapphire femtosecond laser at 780 nm. The possible mechanism of photopolymerization is discussed.     

Jet-cooled infrared spectrum of methoxy in the CH stretching region

Observations of the jet-cooled infrared spectrum of CH(3)O in the CH stretching region have been extended, down to 2756 cm(-1) and up to 3003 cm(-1). In the lower frequency extension, a single vibronic band has been assigned. In the higher frequency region, the spectrum becomes complex above 2900 cm(-1) and remains so until near 2970 cm(-1) where it rapidly becomes sparse. Including the single vibronic band previously reported, a total of four bands have been assigned. Two bands including the original one follow a perpendicular DeltaP = +1 rotational selection rule and the other two bands follow a parallel DeltaP = 0 selection rule. In addition to these in the congested region between 2900 and 2970 cm(-1), ten isolated sub-bands (two P' = -1/2, two P' = +1/2, and six P' = +1.5) have been assigned, but it has so far not been possible to connect these together to form bands. Taken together these observations suggest that there are strong vibronic couplings between the two CH stretching vibrations and the overtone and combination levels in the region.     

Photocontrollable J-aggregation of a diarylethene-phthalocyanine hybrid and its aggregation-stabilized photochromic behavior

The photocontrollable J-aggregation of a diarylethene-phthalocyanine hybrid (T-ZnPc) and its aggregation-stabilized photochromic behavior were investigated by various techniques. T-ZnPc initially exhibited slight J-aggregation tendency in solvents such as chloroform and toluene through conformational planarization effect, but formed much stronger J-aggregates upon the illumination of 254 nm UV light. In darkness, the UV-irradiated solutions gradually returned to their initial state. These phenomena can be explained by the pronounced change in molecular planarity accompanying the reversible isomerization of the diarylethene units of T-ZnPc. Besides, we have found that the thermal stability of the closed-ring diarylethene isomers in molecularly dispersed T-ZnPc is much poorer than that in aggregates. As long as the aggregates were broken, they converted to corresponding open-ring form instantly. This study provided an example of fully photocontrollable aggregation of phthalocyanines and paved a new way for improving the stability of the photochromic systems.     

Scandium terminal imido complex induced C-H bond selenation and formation of an Sc-Se bond

The reaction between scandium terminal imido complexes and elemental selenium showed an unprecedented C-H bond selenation and the formation of an Sc-Se bond.     

Influence of the intensity gradient upon HHG from free electrons scattered by an intense laser beam

When an electron is scattered by a tightly focused laser beam in vacuum, the intensity gradient is a critical factor to influence the electron dynamics. In this paper, we have further investigated its influence upon the electron high-harmonic generation (HHG) by treating the spacial gradient of the laser intensity as a ponderomotive potential. Based upon perturbative quantum electrodynamics calculations, it has been found that the main effect of the intensity gradient is the broadening of the originally line HHG spectra. A one-to-one relationship can be built between the beam width and the corresponding line width. Hence, this finding may provide us a promising way to measure the beam width of intense lasers in experiments. In addition, for a laser pulse, we have also studied the different influences from transverse and longitudinal intensity gradients upon HHG.     

Complex‐Formation‐Enhanced Fluorescence Quenching Effect for Efficient Detection of Picric Acid

Amine‐functionalized α‐cyanostilbene derivatives (Z)‐2‐(4‐aminophenyl)‐3‐(4‐butoxyphenyl)acrylonitrile (ABA) and (Z)‐3‐(4‐butoxyphenyl)‐2‐[4‐(butylamino)phenyl]acrylonitrile (BBA) were designed for specific recognition of picric acid (PA), an environmental and biological pollutant. The 1:1 host–guest complexes formed between the chemosensors and PA enhanced fluorescence quenching, thus leading to sensitive and selective detection in aqueous media and the solid phase.     

Diradical B/N-Doped Polycyclic Hydrocarbons

Heterocyclic diradicaloids with atom-precise control over open-shell nature are promising materials for organic electronics and spintronics. Herein, we disclose quinoidal π-extension of a B/N-heterocycle for generating B/N-type organic diradicaloids. Two quinoidal π-extended B/N-doped polycyclic hydrocarbons that feature fusion of the B/N-heterocycle motif with the antiaromatic s-indacene or dicyclopenta[b,g]naphthalene core were synthesized. This quinoidal π-extension and B/N-heterocycle leads to their open-shell electronic nature, which stands in contrast to the multiple-resonance effect of conventional B/N-type emitters. These B/N-type diradicaloids have modulated (anti)aromaticity and enhanced diradical characters comparing with the all-carbon analogues, as well as intriguing properties, such as magnetic activities, narrow energy gaps and highly red-shifted absorptions. This study thus opens the new space for both of B/N-doped polycyclic π-systems and heterocyclic diradicaloids.