开放式复杂航空网络系统的动力学演化

本文首先实证研究了中国航空网(CAN)与外部经济环境,即国民生产总值(GDP)的相关性,进而揭示CAN的演化方式及其拓扑特征的起源.发现自1998年起网络节点的度与其GDP成线性关系,表明了网络拓扑与经济因素有密切的联系,且CAN的度演化服从类似于多重过程(multiplicative process)的模式,而该模式又强烈依赖于GDP的增长率.这种独特的模式暗示了CAN具有类似适应度模型的微观机理.通过对演化方程的研究发现:1)CAN在增长过程中,节点加入的时刻具有经济上的偏好性,即节点加入的时刻与该节 关键词： 国民生产总值(GDP) 中国航空网(CAN) 双段幂率分布 多重过程     

Passively Q-switched GdVO<Subscript>4</Subscript>/Nd:GdVO<Subscript>4</Subscript> laser with Cr<Superscript>4+</Superscript>:YAG saturable absorber under direct 879 nm diode pumping to the emitting level

A passively Q-switched 1.06 μm laser with Cr⁴⁺:YAG saturable absorber by direct 879 nm diode pumping grown-together composite GdVO₄/Nd:GdVO₄ crystal to the emitting level was demonstrated in this paper. The characteristics of pulsed laser were investigated by using two kinds of Cr⁴⁺:YAG crystal with the initial transmissivity of 80 and 90%, respectively. When the T ₀ = 90% Cr⁴⁺:YAG was used, an average output power of 1.59 W was achieved at an incident pump power of 10 W. The pulse width and repetition rate were 64.5 ns and 170 kHz, respectively. The thermal lens effect of laser crystal was analyzed.     

Q-switched Ho:YAlO<Subscript>3</Subscript> laser pumped by Tm:YLF laser at room temperature

A Q-switched high efficient Ho:YAlO₃ (Ho:YAP) laser pumped by a diode-pumped Tm:YLF laser at room-temperature is realized. The maximum output energy reaches 1.58 mJ under the repetition frequency of 5 kHz, when the incident pump power is 15.6 W. The pulse width is 22 ns. The wavelength is 2118 nm when the transmission of output coupler is 30%. The beam quality factor is M ² ∼ 1.39 measured by the traveling knife-edge method.     

Microjoule level femtosecond optical pulses with double-cladding fiber-based nonlinear chirped-pulse amplification

An all-fiber high-energy nonlinear chirped-pulse amplification system with two-stage double-cladding fiber amplifiers is presented in this paper. It generates pulses with the energy up to 10 μJ at 20 kHz repetition rate and total accumulated nonlinear phase shift as large as 12.8π. The pulses can be compressed to 137 fs with the compensation of mismatched third-order dispersion by self-phase modulation in the fiber amplifiers.     

Diode-pumped Nd:YVO4 laser emitting at 1074 nm based on the 4F3/2-4I11/2 transition

We report a diode-pumped Nd:YVO₄ laser emitting at 1074 nm, based on the ⁴ F _3/2-⁴ I _11/2 transition, generally used for a 1064 nm emission. A power of 323 mW at 1074 nm has been achieved in continuouswave (CW) operation with a fiber-coupled laser diode emitting 18.2 W at 808 nm. Intracavity second-harmonic generation in CW mode has also been demonstrated with a power of 18 mW at 537 nm by using a LiB₃O₅ (LBO) nonlinear crystal.     

Measurements of radiation vibrations of turbomachine blades using an optical-fiber displacement-sensing system

Turbomachine blades are critical equipment in the energy, chemical, aviation, and shipbuilding industries. Turbomachine-blade vibrations can cause high cycle fatigue, which reduces the blade lifetime. Their stable operation is a determining factor of safe and efficient production. In order to monitor and detect the turbomachine-blade vibrations and check whether whole or partial performance is normally operating, we design a reflective intensity-modulated optical-fiber sensing system for radial vibration detection of turbomachine blades and introduce the basic principles of the detection system in detail. We study some key technologies such as the control system of the laser-diode (LD) constant power and an optical-fiber coupling system with the optical-fiber-bundle structure. We analyze the sensor output characteristics and present some numerical simulations. In view of our experimental results, we show that the system elaborated can eliminate the effects caused by light-intensity fluctuations, optical-fiber flexural losses, and changes in the surface reflection coefficient, and can detect the radial vibrations of turbomachine blades in the presence of strong electromagnetic interference and under high temperatures.     

Performance of a satellite-to-ground downlink coherent lasercom system with random tracking error of receiver

We analyze the performance of a satellite-to-ground downlink coherent lasercom system taking into account the combined effects of atmospheric wavefront aberration and tracking error of the receiver. We revise the wavefront phase variance in the case where the tracking error of the receiver terminal is present. We consider the example of the BPSK modulation scheme and show that the tracking error of the receiver terminal greatly increases the bit error probability of the coherent system. We show the optimum aperture diameter of the receiver. This study can benefit the satellite-to-ground downlink coherent lasercom system design.     

Influence of TiO2 impregnated with a novel copper(II) carboxylic porphyrin and its application in photocatalytic degradation of 4-Nitrophenol

A novel 5,15-di-[4-carboxylatomethoxy]phenyl-10,20-diphenylporphyrin, its copper complex and the corresponding metalloporphyrin-TiO₂ photocatalyst were synthesized and characterized by DRS, SEM, XRD, and FT–IR. The photocatalytic effects of anataseTiO₂ impregnated with this copper(II) porphyrin was investigated by photodegradation of 4-nitrophenol(4-NP) in aqueous solution under Xenon lamp irradiation. The results indicated that the photoactivity of copper(II) porphyrin-TiO₂ composite was evidently enhanced by the interaction between carboxyl of the porphyrin molecule and hydroxyls anchored on the TiO₂. Futhermore, the copper(II) carboxylic porphyrin displayed good adsorption behavior and activity of the dye-sensized TiO₂ system.     

Magnolol and honokiol included green emissive terbium sol–gel materials and their recognition behaviors

Magnolol and honokiol as pharmaceutical ligands have been introduced into terbium complex systems for the first time and two hybrid organic–inorganic materials were successfully prepared. Both of them can sensitize terbium characteristic green emission effectively based on intra-molecular energy transfer channel. Moreover, they selectively recognized Cu²⁺ and Fe³⁺ through luminescence quenching effects. The photophysical properties and morphological structures were extensively investigated.     

Oligosiloxane Functionalized with Pendant (1,3‐Bis(9‐carbazolyl)benzene) (mCP) for Solution‐Processed Organic Electronics

A new oligosiloxane derivative (ODCzMSi) functionalized with the well‐known 1,3‐bis(9‐carbazolyl)benzene (mCP) pendant moiety, directly linked to the silicon atom of the oligosiloxane backbone, has been synthesized and characterized. Compared to mCP, the attachment of the oligosiloxane chain significantly improves the thermal and morphological stabilities with a high decomposition temperature (T_d=540 °C) and glass transition temperature (T_g=142 °C). The silicon–oxygen linkage of ODCzMSi disrupts the backbone conjugation and maintains a high triplet energy level (E_T=3.0 eV). A phosphorescent organic light‐emitting diode (PhOLED) using iridium bis(4,6‐difluorophenyl)pyridinato‐N,C² picolinate (FIrpic) as the emitter and ODCzMSi as the host shows a relatively low turn‐on voltage of 5.0 V for solution‐processed PhOLEDs, maximum external quantum efficiency of 9.2 %, and maximum current efficiency of 17.7 cd A^?1. The overall performance of this device is competitive with the best reported solution‐processed blue PhOLEDs. Memory devices using ODCzMSi as an active layer exhibit non‐volatile write‐once read‐many‐times (WORM) characteristics with high stability in retention time up to 10⁴ s and a low switch on voltage. This switching behaviour is explained by different stable conformations of ODCzMSi with high or low conductivity states which are obtained under the action of electric field through a π–π stacking alignment of the pendant aromatic groups. These results with both PhOLEDs and memory devices demonstrate that this oligosiloxane–mCP hybrid structure is promising and versatile for high performance solution‐processed optoelectronic applications.