Power scaling of printed-circuit-board preionized TEA CO2 laser up to 3.6 kW

A high average power, high-repetition-rate TEA CO₂ laser employing printed-circuit-board preionizer is described. The power scaling of this preionization configuration has been demonstrated. The average output power reaches 3.6 kW at pulse repetition rate of 180 pps. Furthermore, the scaling-up ability of the rotating spark gap as high-voltage switch for high-average-power gas laser has been validated.     

Electrochemical performance of modified artificial graphite as anode material for lithium ion batteries

Artificial graphite anode material was modified by coating an amorphous carbon layer on the particle surface via a sol-gel and pyrolysis route. The electrochemical measurements demonstrate that appropriate carbon coating can increase the specific capacity and the initial coulombic efficiency of the graphite material, while excessive carbon coating leads to the decrease in specific capacity. Thick coating layer is obviously unfavorable for the lithium ion diffusion due to the increased diffusion distance, but the decreased specific surface area caused by carbon coating is beneficial to the decrease of initial irreversible capacity loss. The sample coated with 5 wt.% glucose exhibits a stable specific capacity of 340 mAhg^?1. Carbon coating can remarkably enhance the rate capability of the graphite anode material, which is mainly attributed to the increased diffusion coefficient of lithium ion.     

Optimization of direct modulation rate for circular microlasers by adjusting mode Q factor

Semiconductor microcircular lasers have been investigated as potential light sources for photonic integrated circuits and optical interconnections for more than two decades. However, the direct modulation bandwidths of the circular microlasers remain a challenge, especially when being compared with other microlasers, such as photonic crystal lasers. In this paper, microcircular lasers connected to an output waveguide are investigated for high‐speed direct modulation with optimized mode Q factors. Small signal modulation with a resonance frequency of f_R = 12.5 GHz is realized for a AlGaInAs/InP circular microlaser with a radius of 10 µm at 290 K. Furthermore, clear eye diagrams are observed at 12.5 Gbit/s for a 15‐µm radius circular microlaser with f_R = 6.9 GHz.     

基于RFID及3G网络的物流跟踪系统研究

为实现物流货物自动跟踪,通过RFID电子标签自动记录货物的收货、入库、卸货、送货全过程,在运输途中,通过传感器实时采集运输环境参数并通过3G上传到服务器,在地图上实现货物位置、运输环境、货物名称的精确对比,运输环境不合适时及时报警;详细介绍了系统的整体设计,并对系统的软硬件设计进行了分析,测试结果表明,系统整体稳定,环境测量误差率低,能够实现物流货物的全程跟踪,该系统可广泛应用于物流业。     

DNS study of swirling intensity effect on flow pattern of a circular jet

Abstract  

The figures show the 3D flow pattern of a circular jet with different swirling intensity. Reynolds number is approximately 4300 computed based on the nozzle diameter (d), jet velocity (U), and air fluid property at 1 atm and 300 K. The overall computational domain is set to be 4 × 4 × 12 d in spanwise, height, and streamwise direction. The governing equations are the fully compressible Navier–Stokes equations, firstly differenced by eighth-order explicit scheme and then advanced temporarily by using the fourth-order explicit Runge–Kutta method. 3D characteristics non-reflecting boundary condition including transverse source contribution is imposed on all other boundaries except the inflow boundary handled by assigning fixed profiles of temperature and velocity. To ensure the simulation resolution, here over 16 million grids are employed in sum, combined with a handful of grids located at buffer zones of outflow boundaries. To correctly represent the vortex in the flow field, velocity gradient tensor invariant Q is used here. And ψ refers to the swirling intensity defined as the ratio of tangential momentum to axis momentum. As shown in velocity profile, the flow pattern of the jet changes from a close mode to a totally open mode as ψ increases from 0.4 to 1.5. Accordingly, the recirculation zone gradually moves upstream and backflow velocity is enlarged as well. It is inteseting to found that the obvious drops of the momentums in two shown directions always occur at the same position downstream, no matter how large the ψ value is. Therefore, a momentum compensatory mechanism is expected to exist in the vortex-abundant zone. With the increase of ψ value, the increased strain rate in tangential direction can induce vortex more quickly, intensifying the entrainment and velocity-attenuation, which can be observed in Q value profile.     

Cold atom space clock with counter-propagating atoms

<正>We discuss the feasibility of realizing a cold atom space clock with counter-propagating cold atoms in microgravity.The design of the space clock is based on an atomic beam clock with Ramsey cavity,except that magneto-optical trap(MOT) is placed at each side.Cold atoms are launched simultaneously from the MOTs at both sides of the clock and they move at the counter-direction towards each other.The velocity of the launched atoms is precisely controlled to Ramsauer-Townsend resonance so that no additional collision frequency shift takes place.Such configuration can efficiently cancel the frequency shift resulting from cavity phase shift and increase the signal-to-noise ratio(SNR).     

NO在Ir(111)表面吸附与解离的第一性原理研究

本文系统研究了NO在Ir(111)表面的吸附,解离,以及可能的N_2生成机理.结果表明,顶位吸附的NO,其解离能垒较高(3.17 eV),不会发生解离,而三重Hcp和Fcc空位吸附的NO发生解离,能垒分别为1.23和1.28 eV.N_2是唯一的生成物,不会有副产物N_2O的产生.其最可能的反应路径为N和NO经过N_2O中间体而生成N_2,而不是直接N提取和N-N聚合产生N_2的机理.     

Design,synthesis and biological activity of some novel benzimidazole derivatives against Coxsackie virus B_3

A series of novel benzimidazole derivatives was synthesized and their anti-Coxsackie virus B_3(CVB_3) activity was evaluated in VERO cells.Compounds 9 and 10 exhibited better inhibitory activity than those of ribavirin(RBV) with IC_(50) values of 5.30 and 1.06μg/mL,respectively.     

面向客户群的服务方案配置规则挖掘方法

产品/服务配置规则获取的主要方式是用数据挖掘技术从设计实例数据库中提取.客户化服务方案配置规则为服务功能需求和方案特征间的关联规则.考虑到常用关联规则挖掘算法Apriori具有运算复杂的缺点,提出基于PIETM(Principle of Inclusion—Exclusion and Transaction Mapping)算法的配置规则挖掘方法,考虑置信度和有趣度指标,提取强关联规则.针对配置实例数据库数据量较大时,配置规则挖掘的效率会降低且会产生大量冗余规则的问题,采用二元语义模型表达定性的服务功能需求,将同类客户群的功能需求进行合并,替换多样化的功能需求,减少规则的冗余.最后以一工程机械制造企业服务方案配置规则挖掘为例,验证了所提方法的有效性.     

Effects of carbon contents on morphology and electrical properties of Li2MnSiO4/C prepared by a vacuum solid-state method

To improve the electrochemical performance of Li₂MnSiO₄ with low electric conductivity, the Li₂MnSiO₄/C composite are synthesized by a vacuum solid-state reaction of a mixture of SiO₂, LiCH₃COO, Mn(CH₃COO)₂ and designed mass of C₆H₁₂O₆ · H₂O as carbon sources. The crystalline structure and morphology of products are analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and laser scattering technology (LS) respectively. The tested results show that carbon doping decrease the crystallite sizes of products, but keep the aggregation of the particles and made the impurity increased instead. The results of constant current charge-discharge prove that the mixed carbon improve Li⁺ transmission performance and decrease inner polatization resistance of Li₂MnSiO₄ materials, but can not prevent the collapse of Li₂MnSiO₄ crystal structure. While the galvanostatic intermittent titration technique (GITT) results demonstrate that the primary reason for the improved electrochemical performance can be attributed to increased Li-ion diffusion coefficient $(D_{Li^ + } )$ as a result from carbon doping.