An ideal host-guest system to accomplish high-performance greenish yellow and hybrid white organic light-emitting diodes

Greenish yellow organic light-emitting diodes (GYOLEDs) have steadily attracted researcher's attention since they are important to our life. However, their performance significantly lags behind compared with the three primary colors based OLEDs. Herein, for the first time, an ideal host-guest system has been demonstrated to accomplish high-performance phosphorescent GYOLEDs, where the guest concentration is as low as 2%. The GYOLED exhibits a forward-viewing power efficiency of 57.0 lm/W at 1000 cd/m², which is the highest among GYOLEDs. Besides, extremely low efficiency roll-off and voltages are achieved. The origin of the high performance is unveiled and it is found that the combined mechanisms of host-guest energy transfer and direct exciton formation on the guest are effective to furnish the greenish yellow emission. Then, by dint of this ideal host-guest system, a simplified but high-performance hybrid white OLED (WOLED) has been developed. The WOLED can exhibit an ultrahigh color rendering index (CRI) of 92, a maximum total efficiency of 27.5 lm/W and a low turn-on voltage of 2.5 V (1 cd/m²), unlocking a novel avenue to simultaneously achieve simplified structure, ultrahigh CRI (>90), high efficiency and low voltage.     

光子晶体光纤的原理、应用和研究进展

光子晶体光纤（POF）与普通光纤在光纤结构、单模特性、色散特性和非线性特性等方面有着显著的差别。本文将简要分析PCF的管理，并探讨其重要特性以及应用价值 ，最后回顾了近来PCF的研究进展。     

中国光纤光缆产业的历史、现状与前景

近年来国产光纤的市场份额正逐步上升,但国内光纤生产企业在原材料上受国外制约较大,光纤预制棒严重依赖进口,而且国内光纤光缆产业联系松散,在5家光纤光缆一体化企业中,仅有两家拥有完整产业链。中国正式加入WTO后,国内光纤光缆企业的整合在所难免,他们应积极进行产业升级,形成多个具有完整产业链的大集团。     

基于光纤Bragg光栅的滤波技术

介绍了国际上最新的基于光纤Bragg光栅的光纤滤波技术发展情况，详细阐述了分布反馈式光纤Bragg光栅滤波器、多波长选择光纤Bragg光栅滤波器、应用光纤Bragg光栅的Michelson干涉型（MI）滤波器以及光纤Bragg光栅滤波耦合器的理论难点、基本原理及其应用。     

光纤陀螺零偏和标度因数补偿算法

研究了光纤陀螺的输出特性,对光纤陀螺的各种输出模型、零偏和标度因数温度模型、开环光纤陀螺(OFOG)标度因数非线性模型进行了探讨,并通过仿真和实验,比较说明了各种温度模型、非线性模型的补偿效果,对工程应用具有指导作用.     

Mode-locked fiber lasers with significant variability of generation regimes

We demonstrate a great variability of single-pulse (with only one pulse/wave-packet traveling along the cavity) generation regimes in fiber lasers passively mode-locked by non-linear polarization evolution (NPE) effect. Combining extensive numerical modeling and experimental studies, we identify multiple very distinct lasing regimes with a rich variety of dynamic behavior and a remarkably broad spread of key parameters (by an order of magnitude and more) of the generated pulses. Such a broad range of variability of possible lasing regimes necessitates developing techniques for control/adjustment of such key pulse parameters as duration, radiation spectrum, and the shape of the auto-correlation function. From a practical view point, availability of pulses/wave-packets with such different characteristics from the same laser makes it imperative to develop variability-aware designs with control techniques and methods to select appropriate application-oriented regimes.     

A novel hybrid model for inversion problem of atmospheric refractivity estimation

Atmospheric refractivity estimation is an important issue for performance evaluation of communication systems and air surveillance radars. A novel hybrid model based on artificial neural networks (ANNs) and genetic algorithms (GAs) for inversion problem of atmospheric refractivity estimation is introduced. In this paper, inversion problem and clutter model problem of refractivity from clutter (RFC) method are separated and only inversion problem is studied. A problem specific ANN structure is designed and an original GA is developed to fulfill atmospheric refractivity estimations. In hybrid method, ANNs make pre-estimation and GAs use these results as a starting population for post-estimation. When the results obtained from the single solutions of ANNs and GAs are compared to the results obtained from hybrid model, a significant improvement in the accuracy of estimated results is observed.     

Wavelength‐Dependent Photosensitivity in a Germanium‐Doped Sol–Gel Hybrid Material for Direct Photopatterning

Photosensitivity, as evident in permanent changes in refractive index and volume upon light exposure, is observed in a germanium‐doped methacrylate hybrid material (hybrimer) and found to depend on the wavelength of the UV light. Exposure to short‐wavelength UV illumination (220–260 nm) results in very high photosensitivity with changes in refractive index (Δn ≈ 0.0164) and film thickness (Δt ≈ –40 %) that are mainly a result of photopolymerization and Ge‐related densification. In contrast, the hybrimer is hardly photosensitive to light in the long UV‐wavelength range (350–390 nm). Direct photopatterning of a single circle on the hybrimer film creates a concave lens‐like topography upon illumination with UV light of short wavelength and a convex lens‐like one upon illumination with UV light of long wavelength.     

Resource planning and bandwidth allocation in hybrid fiber–coax residential networks

The introduction of new high bandwidth services such as video-on-demand by cable operators will put a strain on existing resources. It is important for cable operators to know how many resources to commit to the network to satisfy customer demands. In this paper, we develop models of voice and video traffic to determine the effect of demand growth on hybrid fiber–coax networks. We obtain a set of guidelines that network operators can use to build out their networks in response to increased demand. We begin with one type of traffic and generalize to an arbitrary number of high-bandwidth constant bit rate (CBR) like services to obtain service blocking probabilities. We consider the effect of supporting variable bit rate (VBR) packet-switched traffic in addition to CBR services. These computations help us to determine how cable networks would function under various conditions (i.e., low, medium, and heavy loads). We also consider how the growth rate of the popularity of such services would change over time, and how this impacts network planning. Our findings will help cable operators estimate how much bandwidth they need to provision for a given traffic growth model and connection blocking requirement.