Spatio-temporal visualization of light transport in complex photonic structures

Spatio-temporal imaging of light propagation is very important in photonics because it provides the most direct tool available to study the interaction between light and its host environment.Sub-ps time resolution is needed to investigate the fine and complex structural features that characterize disordered and heterogeneous structures,which are responsible for a rich array of transport physics that have not yet been fully explored.A newly developed wide-field imaging system enables us to present a spatiotemporal study on light transport in various disordered media,revealing properties that could not be properly assessed using standard techniques.By extending our investigation to an almost transparent membrane,a configuration that has been difficult to characterize until now,we unveil the peculiar physics exhibited by such thin scattering systems with transport features that go beyond mainstream diffusion modeling,despite the occurrence of multiple scattering.

Improved performance of organic light-emitting diodes with dual electron transporting layers

In this study the performance of organic light-emitting diodes （OLEDs） are enhanced significantly, which is based on dual electron transporting layers （13phen/CuPc）. By adjusting the thicknesses of Bphen and CuPc, the maximal luminescence, the maximal current efficiency, and the maximal power efficiency of the device reach 17570 cd/m^2 at 11 V, and 5.39 cd/A and 3.39 lm/W at 3.37 mA/cm^2 respectively, which are enhanced approximately by 33.4%, 39.3%, and 68.9%, respectively, compared with those of the device using Bphen only for an electron transporting layer. These results may provide some valuable references for improving the electron injection and the transportation of OLED.

Increased performance of an organic light-emitting diode by employing a zinc phthalocyanine based composite hole transport layer

We demonstrate that the electroluminescent performances of organic light-emitting diodes are significantly improved by employing a zinc phthalocyanine （ZnPc）-based composite hole transport layer （c-HTL）. The optimum ris-（8-hydroxyquinoline）aluminum （Alq3）-based organic light-emitting diode with a c-HTL exhibits a lower turn-on voltage of 2.8 V, a higher maximum current efficiency of 3.40 cd/A and a higher maximum power efficiency of 1.91 lm/W, which are superior to those of the conventional device （turn-on voltage of 3.8 V, maximum current efficiency of 2.60 cd/A, and maximum power efficiency of 1.21 lm/W）. We systematically studied the effects of different kinds of N’-diphenyl-N,N’-bis（1-naphthyl）（1,1’-biphenyl）-4,4’diamine （NPB）：ZnPc c-HTL. Meanwhile, we also investigate their mechanisms different from that in the case of using ZnPc as buffer layer. The specific analysis is based on the absorption spectra of the hole transporting material and current density–voltage characteristics of the corresponding hole-only devices.

Dynamic Behavior and Mass Transport in Polyacrylic Acid Gel by Dynamic Light Scattering

Dynamic behaviors on polyacrylic acid (PAA) gels and mass (small molecules) transports in the gels have been studied mainly by dynamic light scattering (DLS). The cross-linking degree (fc), monomer concentration (Cm) and temperature of the gels have significant influences on its dynamic behavior and mass transport in the gels. The increase of fc leads to decrease of the mesh sizes of the gels, thus the obstacle of the gels for mass transport is increased. As a result, small molecular diffusion Dk in the gels is decreased. So even if for small molecules, the Dk also is influenced.

Comparative evaluations of the Monte Carlo-based light propagation simulation packages for optical imaging

Monte Carlo simulation of light propagation in turbid medium has been studied for years.A number of software packages have been developed to handle with such issue.However,it is hard to compare these simulation packages,especially for tissues with complex heterogeneous structures.Here,we first designed a group of mesh datasets generated by Iso2Mesh software,and used them to cross-validate the accuracy and to evaluate the performance of four Monte Carlo-based simulation packages,including Monte Carlo model of steady-state light transport in multi-layered tissues(MCML),tetrahedron-based inhomogeneous Monte Carlo optical simulator(TIMOS),Molecular Optical Simulation Environment(MOSE),and Mesh-based Monte Carlo(MMC).The performance of each package was evaluated based on the designed mesh datasets.The merits and demerits of each package were also discussed.Comparative results showed that the TIMOS package provided the best performance,which proved to be a reliable,efficient,and stable MC simulation package for users.

ZnO sheets prepared with a light-assisted growth method for improved photodegradation performance

ZnO as a semiconductor photocatalyst is widely applied in the photodegradation of organic pollutants. Its photocatalytic activity is greatly decreased because of the recombination of photoexcited electrons and holes in the bulk. In this work, ZnO sheets are synthesized by adjusting the NaOH concentration under light irradiation at room temperature. Compared with ZnO particles, the ZnO sheets prepared with a light-assisted growth method exhibit a higher rate of photodegradation of methylene blue under UV visible light irradiation. The improved photodegradation rate is mainly attributed to the shortened transport distance of photoexcited electrons, the high surface area, and the surface atom structure modified by the light-assisted growth process. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.

Observation of oscillations in the transport for atomic layer MoS_2

In our experiment, an atomic layer MoS2structure grown on SiO2/Si substrates is used in transport test. The voltage U14,23 oscillates and the corresponding period varies with applied current. The largest period appears at 45 μA. The oscillation periods are different when samples are under laser radiation or in darkness. We discover that under the laser irradiation, the oscillation period occurs at lower current than in the darkness case. Meanwhile, the drift velocity is estimated at ~10~7 cm/s. Besides, by studying the envelope of U14,23 versus applied current, we see a beating phenomenon at a certain current value. The beating period in darkness is larger than under laser irradiation. The difference between beating periods reveals the energy difference of electrons. Similar results are obtained by using different laser power densities and different light sources. The possible mechanism behind the oscillation period is discussed.

Anisotropic transport properties in the phase-separated La_(0.67)Ca_(0.33)MnO_3/NdGaO_3 (001) films

The anisotropic transport property was investigated in a phase separation La（0.67）Ca（0.33）MnO3（LCMO） film grown on（001）-oriented Nd GaO3（NGO） substrate. It was found that the resistivity along the b-axis is much higher than that along the a-axis. Two resistivity peaks were observed in the temperature dependent measurement along the b-axis, one located at 91 K and the other centered at 165 K. Moreover, we also studied the response of the resistivities along the two axes to various electric currents, magnetic fields, and light illuminations. The resistivities along the two axes are sensitive to the magnetic field. However, the electric current and light illumination can influence the resistivity along the b-axis obviously, but have little effect on the resistivity along the a-axis. Based on these results, we believe that an anisotropicstrain-controlled MnO6 octahedra shear-mode deformation may provide a mechanism of conduction filaments paths along the a-axis, which leads to the anisotropic transport property.

Optimization of a poly (p-phenylene benzobisoxazole)-based light-emitting device with a complex cathode structure

In this work, we report the preparation of a series of electroluminescent （EL） devices based on a high-performance polymer, poly（p-phenylene benzobisoxazole） （PBO）, and their optoelectronic properties, which have been rarely explored. The device structure is optimised using a complex cathode structure of tris-（8-hydoxyquinoline） aluminium （Alq3）/LiF/Al. By tuning the thickness of the Alq3 layer, we improve the device efficiency dramatically in an optimized condition. Further analysis reveals that the Alq3 layer in the complex cathode structure acts as a hole blocker in addition to its electron-injection role. A green light emission with a maximum brightness of 8.7×103 cd/m2 and a moderate current efficiency of 4.8 cd/A is obtained. These values are the highest ever reported for PBO devices. The high operational stability demonstrated by the present device makes it a promising tool for display and lighting applications. A new material is added to the selection of polymers used in this field up to now.

Design and Analysis of Traffic Information Transmission System Based on Visible Light Communication

Visible Light Communication( VLC) based on LED is a new wireless communication technology with high response rate and good modulation characteristics in the wavelengths of 380- 780 nm. Compared with conventional methods,the waveband of VLC is harmless to human and safe to communication because of no magnetism radiation. An audio information transmission system using LED traffic lights is presented based on VLC technology. The system is consisted of transmitting terminal,receiving terminal and communication channel. Some experiments were made under real communication environment. The experimental results showed that the traffic information transmission system works steadily with good communication quality and achieves the purpose of transmitting audio information through LED traffic lights,with a data transfer rate up to 250 kbps over a distance of 5 meters.

可见光抗菌的单向导湿自泵织物

具有湿度管理和抑菌性能的功能织物可以有效提高穿着舒适度。现有方法往往通过在亲水织物表面物理浸涂抗菌剂,虽然可起到短效抑菌作用,但会导致抗菌剂大量突释,引起皮肤不适,抗菌能力快速减弱。本文利用静电纺丝方法制备了一种掺杂可见光激发抗菌光敏剂的自泵织物(Self-pumping textile,SPT),实现了汗液的单向移除同时高效抗菌。自泵织物由疏水的聚偏二氟乙烯-六氟丙烯(PVDF-HFP)纤维和亲水的碱水解醋酸纤维素(CA)纤维组成,其中亲水纤维中掺杂了具有高活性氧产生能力的聚噻吩(PT2)光敏剂。在接触角导液模型中,我们证实了导液时间随疏水层厚度增加而延长,当疏水层电纺时间为60 s时,水分可以在10 s内从疏水层单向导出到亲水层。使用功率为25 mW/cm^(2)的氙灯光模拟日常太阳光进行抗菌,结果表明,10 min可以杀灭95%以上的金黄色葡萄球菌和大肠杆菌。本工作为功能性织物的设计提供了一种新的思路。

基于物联网的交通信号灯控制系统

随着城市化进程的不断加速,交通拥堵问题成为制约城市可持续发展的一大挑战。在智能交通系统中,交通信号灯作为关键组成部分,对道路交通的管理和优化发挥着至关重要的作用。为提高交通效率、减少交通拥堵,文章探讨了基于物联网的智能交通信号灯控制系统。首先,介绍了交通信号灯的系统组成。其次,针对交通信号灯控制的优化需求,提出一种基于物联网的自适应控制算法。最后,构建了交通信号灯仿真界面,并设计了交互控制按钮。实验结果表明,所提出的自适应控制算法能够有效提升道路通行效率,降低交通拥堵程度,为智能交通系统的进一步优化与发展提供了重要参考。

光电调控的磁性WSe_(2)超晶格中的自旋和谷极化输运

基于磁性WSe_(2)超晶格系统,探讨了非共振圆偏振光与栅极电压及其对隧穿、谷极化及自旋极化的影响;发现了单层WSe_(2)的弹道输运操纵,以及基于磁性WSe_(2)的NM-FM-NM结的周期性阵列量子输运的调控.结果表明:通过增加势垒的数量,圆偏振光临界值可消除透射能隙;圆偏振光和栅极电压可视为一个透射阀,也可用于控制自旋和谷极化的敏感旋钮.发现了在WSe_(2)超晶格中的克莱因隧穿是自旋-谷相关的;自旋-谷极化可以利用栅极电压和圆偏振光来调整和转换.

轮轨摩擦系数对低地板轻轨动力响应及车轮磨耗的影响

为了确保低地板轻轨车辆安全且平稳地运行,以某轻轨线路为依托,利用多体动力学软件UM(Universal Mechanism)建立了低地板轻轨车辆-轨道耦合动力学模型。选用LM磨耗型车轮踏面以及R50标准钢轨,以美国六级不平顺轨道谱作为线路激扰。基于Hertz及Kalker简化理论、Archard模型,进行不同摩擦系数共5个工况下车辆动力响应以及车轮磨耗变化规律的仿真分析。在此基础上进一步分析了4个不同运行里程阶段对应共96组车轮磨耗型面下轻轨车辆安全性指标的变化规律。研究了4个不同运行里程阶段对应的不同车轮磨耗型面下车辆过曲线时安全性指标随摩擦系数的变化情况。结果表明:脱轨系数、轮轴横向力、轮轨横向力、车体横向加速度受摩擦系数的影响较为显著,而轮重减载率、车体垂向加速度对摩擦系数的改变并不敏感。车轮磨耗深度随里程和摩擦系数的增加而增大,且相同工况下独立旋转车轮的磨耗情况更加严重。在车辆运行40000 km后,其轮轨横向力、轮轴横向力、脱轨系数整体呈现随里程增加而增大的规律,而轮重减载率基本不受运行里程的影响。在不同摩擦系数及运行里程的叠加影响下,轮轨横向力、轮轴横向力、脱轨系数的峰值出现的位置不同,而轮重减载率却始终处于较为稳定的状态。

Rational Design of Star-shaped Molecules with Benzene Core and Naphthalimide Derivatives End Groups as Organic Light-emitting Materials

A series of star-shaped molecules with benzene core and naphthalimides derivatives end groups have been designed to explore their optical,electronic,and charge transport properties as charge transport and/or luminescent materials for organic light-emitting diodes（OLEDs）. The frontier molecular orbitals（FMOs） analysis has turned out that the vertical electronic transitions of absorption and emission are characterized as intramolecular charge transfer（ICT）. The calculated results show that the optical and electronic properties of star-shaped molecules are affected by the substituent groups in N-position of 1,8-naphthalimide ring. Our results suggest that star-shaped molecules with n-butyl（1）,benzene（2）,thiophene（3）,thiophene S？,S？-dioxide（4）,benzo[c][1,2,5]thiadiazole（5）,and 2,7a-dihydrobenzo[d]thiazole（6） fragments are expected to be promising candidates for luminescent and electron transport materials for OLEDs. This study should be helpful in further theoretical investigations on such kind of systems and also to the experimental study for charge transport and/or luminescent materials for OLEDs.

基于尾灯灯语的混行交通流车辆驾驶意图识别模型研究

针对长期存在自动驾驶车辆(autonomous vehicle,AV)与人工驾驶车辆(human-driven vehicle,HV)混行的交通现状,结合深度学习和HSV颜色特征提取方法,提出了一种在混行交通环境下基于尾灯灯语的车辆驾驶意图识别模型。以Mask R-CNN(mask region proposal convolutional neural network)车辆模型检测出的感兴趣区域RoI(region of interest)为限制,将区域内的HV作为研究对象,根据尾灯位置相关性,在HV车尾区域添加纵横向约束来定位传递灯语信号的左右尾灯;在规定的灯语组合及转向灯闪烁频率基础上,提出了一种基于时间序列的灯语识别算法,运用多目标判别相关性滤波CSRT(channel and spatial relatability tracking)跟踪HV尾灯并统计尾灯时序状态;以动态灯语作为输入,构建基于尾灯灯语的驾驶意图识别模型;使用基于真实路况信息的Cityspaces数据集和交通流视频数据对模型进行训练、验证和测试。研究结果表明:基于尾灯灯语的驾驶意图识别模型对视频流车辆尾灯检测准确率和召回率分别为96.0%、98.2%,对驾驶意图识别的平均准确率达到了95.9%,单帧识别耗时为20 ms,为高速混行环境下的AV决策规划提供了有效的理论依据。

不同光照模式对豚鼠视网膜多巴胺转运蛋白表达的影响

目的观察不同光照模式对豚鼠眼内多巴胺转运蛋白(DAT)表达的影响。方法选取36只白色3周龄普通级豚鼠,采用随机数字表法将其随机分为10000 lx组、5000 lx组和500 lx组,每组12只,分别接受相应强度的强光、中强光和正常光照射,并在各组内随机分成3个亚组,每组4只,500 lx组分别接受5、20、40 min光照;5000 lx组分别接受2、4、40 min光照;10000 lx组分别接受2、5、20 min光照。各组豚鼠接受光处理后注射99m Tc-TRODAT-1用于SPECT扫描DAT显像,通过Micro-SPECT采集图像数据。采用Micro-CT软件对豚鼠视网膜感兴趣区进行分析,感兴趣区总的计数值用Sum表示,Sum值反映DAT的相对分布量或分布密度。比较光照处理后豚鼠暴露眼和对照眼DAT密度、不同光照强度和不同光照时长下豚鼠双眼DAT密度差值,以及光照强度和光照持续时间对豚鼠DAT聚集的累积效应和交互效应。另取3只豚鼠,光处理后对豚鼠眼部进行连续6 h图像采集,每隔20 min采集1次,每只豚鼠共采集18次,分析豚鼠眼DAT密度随时间的变化趋势。结果500、5000、10000 lx光照强度下暴露眼DAT密度(Sum值)分别为5598.97±3159.38、8636.78±2503.16和7407.39±2053.41,明显高于对照眼的4388.89±2902.90、5981.92±3057.44和5091.32±2039.36,差异均有统计学意义(t=5.31、4.69、11.80,均P<0.001)。500 lx光照强度下,豚鼠暴露眼和对照眼DAT密度差值在不同光照时间组间比较差异有统计学意义(F=14.01,P<0.01),其他光照强度下不同光照时间组间比较差异均无统计学意义(均P>0.05)。光照时间为5 min时,10000 lx组豚鼠暴露眼和对照眼DAT密度差值明显大于500 lx组,差异有统计学意义(t=-13.22,P<0.001),其他光照时长下不同组间比较差异均无统计学意义(均P>0.05)。未发现光照强度、光照时间对DAT密度差值的累积效应和交互效应(均P>0.05)。光照后连续扫描显示,豚鼠视网膜DAT密度随时间延长先上升到峰值,随后逐渐恢复至正常值。结论光照可以引起视网膜DAT分泌增加,即使在中强度或正常光照水平下,也可以起到刺激DAT产生的作用。未发现光照强度和光照时间对视网膜DAT分布和密度的累积效应和交互效应。

纳米结构金属氧化物电子传输层研究进展

总结纳米结构金属氧化物在钙钛矿太阳电池中的应用进展,详细介绍纳米结构金属氧化物(包括二氧化钛、氧化锌和二氧化锡等)作为电子传输材料的实例。此外,对纳米结构金属氧化物电子传输层进行掺杂和界面修饰等方面的研究进展加4个介绍。最后,对该类电子传输层的未来发展前景进行展望。

基于缓解交通拥堵路况的信号灯配时及道路导向优化研究

随着城市化进程的不断推进,交通拥堵问题成为影响城市居民生活和企业运营的主要挑战之一。文章旨在通过优化城市交叉口红绿灯时序,改善城市交通拥堵状况,提高交通流畅性和安全性。红绿灯作为交通控制的关键因素,其时序规划的合理性直接关系到城市交通系统的运行效率。为了应对城市交通的复杂性和多样性,文章构建了一个综合考虑机动车、行人和非机动车等多种交通参与者的微观交通仿真模型,通过数学公式和遗传算法进行优化,旨在找到最佳的红绿灯时序配置,以实现交通系统的最优化。文章的仿真实验选取了城市实际交叉口为案例,通过调整红绿灯时序观察交通流的变化,验证了模型和算法的有效性。通过研究发现,优化红绿灯时序不仅能够改善交通拥堵问题,提高交通流畅性,还能保障行人及非机动车的交通安全,这为未来城市的可持续发展和居民的出行提供了有益的参考和指导。

低对称性能谷光子晶体中的拓扑光传输

能谷光子晶体是研究拓扑光子学的重要平台之一,基于能谷光子晶体的新型光波导支持抗散射传输的能谷依赖边界态,提高了波导中的急弯传输效率,为光信息高效传输提供了新思路.另一方面,对称性在拓扑学和光子晶体研究中具有重要的物理意义和研究价值.例如,能谷光子晶体在破缺空间反演对称性的情况下表现出类量子能谷霍尔效应.目前,大多数能谷光子晶体具有C3对称性,而具有更低对称性的能谷光子晶体是否能够支持拓扑光传输仍然需要研究.本文通过调整能谷光子晶体的原胞形貌,构建了低对称性能谷光子晶体,并研究了其边界态的传输特性.研究结果表明,相对于C3对称性能谷光子晶体,低对称性能谷光子晶体的光子禁带变窄,但其边界态仍然能够实现单向激发以及抗散射传输.这一发现丰富了拓扑光子结构的多样性,为在低对称性结构中寻找拓扑保护光传输行为提供了指导.