LD端面泵浦Nd:YVO4激光器热管理结构的研究

基于一种LD端面泵浦Nd:YVO<,4>激光器,设计了一种热沉结合外部风扇散热的风冷式热管理结构,并利用有限元分析方法对Nd:YVO<,4>晶体的温度场进行了数值模拟,分析了环境温度及界面热阻变化对晶体热致效应的影响.模拟结果表明,晶体泵浦区的温度梯度约为17 ℃,当环境温度升高时,所设计的冷却方案仍能满足系统的散热需...     

Charge‐Transport Behavior in Aligned Carbon Nanotubes: A Quantum‐Chemical Investigation

Correlated quantum‐chemical calculations are applied to analyze the amplitude of the electronic‐transfer integrals that describe charge transport in interacting carbon nanotubes (CNTs) by investigating the influences of: i) the relative positions of the CNTs, ii) the size of the CNTs, and iii) their chemical impurities. Our results indicate that the mobility of the charge carrier is extremely sensitive to the molecular packing and the presence of chemical impurities. The largest splitting for the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels is in the case of perfectly cofacial conformations where hexagons face hexagons in the dimer structure. We found that the diameter of the CNT determines the type of transporting carrier: for CNTs with large diameters hole transport dominates, while for thin CNTs electron transport dominates. In general, the carrier mobility for the perfect CNTs (n ≥ 3) is less pronounced than that of C₆₀ due to their relatively small strain. B‐ and N‐doped CNTs exhibit considerably larger mobilities owing to the possibility of metallic behavior. These results provide a plausible explanation for the high mobility found experimentally in a field‐effect transistor (FET) made from a large‐area, well‐aligned CNT array. In addition, these hole‐rich and electron‐rich dopants imply potential applications in nanoelectronics.     

一种应用于二次布局的有效划分方法

提出了一种基于二次布局的结合MFFC结群和hMETIS划分的算法.实验表明:这种方法能得到很好的布局结果,但是运行消耗的时间比较长.为了缩短划分在二次布局中运行的时间,提出了一种改进的结群算法IMFFC,用它在二次布局中做划分.与前者相比较,这种方法虽然布局质量稍差,但速度更快.     

Characterization and Studies on Hydro Dynamically Stable Operation of an Angular Jet SOG for COIL

Chemical oxygen-iodine Laser (COIL) is one of the fast emerging high power laser source for near Infrared (λ=1.315μm) laser generation. The heart of the system is the singlet oxygen generator (SOG) which is a pumping source for this laser. A Jet type SOG with a novel approach was designed and fabricated. Singlet oxygen was taken out of the SOG at an angle of 40° thus avoiding the carry over of droplets, which is one of the major drawbacks of horizontal system. The preliminary results have been reported in our earlier publication. The present paper discusses the performance of this generator for various operational conditions viz. diluent's gas nitrogen / helium, basic hydrogen peroxide composition, generator pressure and gas velocity. Further, conditions for the stable operation from generator as well as chlorine injection point of view have been identified.     

UV‐Triggered Polydopamine Secondary Modification: Fast Deposition and Removal of Metal Nanoparticles

Since the first report in 2007, polydopamine (PDA) coating has shown great potential as a general and versatile method to create functional nanocoatings on arbitrary substrates. Slow kinetics and poor controllability of the coating and secondary modification processes, however, have limited the further development of this attractive method. In this work, it is demonstrated that UV irradiation at 365 nm significantly accelerates the process of secondary modification of a PDA‐coated surface. The kinetics of both thiol and amine modifications of PDA are increased 12‐fold via UV irradiation, while the kinetics of metal ion reduction at the PDA interface is increased more than 550 times. Moreover, it is demonstrated that irradiating a PDA/metal nanoparticle composite surface with UV light at 254 nm leads to dissolution of the deposited metal nanoparticles (MNPs). Finally, grayscale metallic patterns, dynamic deposition, and removal of MNPs on PDA surface are realized with the proposed method.     

Quantum-Confinement Effect in Silicon Nanocrystals during Their Dissolution in Model Biological Fluids

Semiconductors - In present work, we studied the mechanisms of dissolution of porous silicon nanoparticles (PSi NPs) during their incubation in model liquids, i.e. water and phosphate buffered...     

带有多层介质衬底FSS的损耗和带宽特性分析

本文简要介绍应用模匹配方法分析带有多层介质衬底的FSS频率响应技术,在此基础上研究带有多层介质衬底的平面Y形缝隙周期阵列对平面波的频率传输特性。重点讨论介质层厚度变化对FSS传输损耗及带宽的影响。     

基于深度学习的SAR图像舰船目标检测综述

近年来,合成孔径雷达成像技术因具备全天时和全天候的目标感测能力,在海洋实时监测和管控等领域发挥着重要作用,特别是高分率SAR图像中的舰船目标检测成为当前的研究热点之一.首先分析基于深度学习的SAR图像舰船目标检测流程,并对样本训练数据集的构建、目标特征的提取和目标框选的设计等关键步骤进行归纳总结.然后对检测流程中的各部...     

Analysis of threshold conditions for generation of a closed mode in a Fabry-Perot semiconductor laser

Threshold conditions for generation of a closed mode in the crystal of the Fabry-Perot semiconductor laser with a quantum-well active region are analyzed. It is found that main parameters affecting the closed mode lasing threshold for the chosen laser heterostructure are as follows: the optical loss in the passive region, the optical confinement factor of the closed mode in the gain region, and material gain detuning. The relations defining the threshold conditions for closed mode lasing in terms of optical and geometrical characteristics of the semiconductor laser are derived. It is shown that the threshold conditions can be satisfied at a lower material gain in comparison with the Fabry-Perot cavity mode due to zero output loss for the closed mode.     

The influence of substrate temperature on the structural and optical properties of ZnS thin films

Thin films of ZnS were deposited on soda lime glass substrates by a modified close-space sublimation technique. The change in optical and structural properties of the films deposited at various substrate temperatures (150–450°C) was investigated. X-ray diffraction spectra showed that films were polycrystalline in nature having cubic structure oriented only along (111) plan. The crystallinity of films increased with the substrate temperature up to 250°C. However, crystallinity decreased with further increase of substrate temperature and films became amorphous at 450°C. The atomic force microscopy data revealed that the films become more uniform and dense with the increase of substrate temperature. Optical properties of the films were determined from the transmittance data using Swanepoel model. It was observed that the energy band gap is increased from 3.52 to 3.65 eV and refractive index of the films are decreased with the increase of substrate temperature. Moreover, considerable improvement in blue response of the films was noticed with increasing substrate temperature.