Bidirectional colorless wired and wireless WDM-PON with improved dispersion tolerance for radio over fiber

We propose and demonstrate a bidirectional transmission, hybrid wired and wireless access network based on subcarrier modulation (SCM) techniques. The scheme simultaneously enables the dispersion-tolerant transmission of millimeter (mm)-wave signals for use in wireless access networks, downstream baseband signals for optical wired access networks, and optical continuous-wave (CW) carriers for use in upstream data remodulations. Error-free transmissions through a 25-km length of single mode fiber (SMF) for both the downstream baseband and the remodulated upstream signals are confirmed by bit-error-rate (BER) measurements. The dispersion tolerance of the radio-over-fiber (RoF) signal is assessed using numerical simulations.     

Passive sampling techniques for sensing freely dissolved hydrophobic organic chemicals in sediment porewater

With compiled and analyzed information about recent advances in passive sampling techniques for sediment porewater, we discuss common quantitation methods (equilibrium and kinetic diffusion-controlled sampling), effects of temperature and salinity on passive sampling, and benefits and drawbacks of currently available passive samplers based on the principles of solid-phase microextraction.The results show that the in-fiber standardization technique, which is kinetic diffusion-controlled, could shorten sampling time and obtain accurate results using isotopically-labeled reference compounds. Another quantitative method, time-weighted average sampling, may be viable for simultaneously measuring all analytes in sediment porewater, as it is more effective with respect to cost and time. In addition, the effects of temperature and salinity on passive sampling should be quantified in field applications.Currently available passive samplers (e.g., employing polymer-coated fibers and low-density polyethylene sheets) can sense hydrophobic organic chemicals (HOCs) in sediment porewater, but the small capacity and the inflexibility of polymer-coated fibers need to be further improved, while better physical protection of polyethylene devices, particularly when they are deployed under rough conditions, should be carefully considered.In conclusion, passive samplers for in-situ measurement of dissolved HOCs in sediment porewater should be combined with a suitable quantitative method and calibration for the effects of temperature and salinity.     

利用被动差分吸收光谱技术反演南极中山站地区夏季臭氧柱浓度

采用被动差分吸收光谱技术(differential optical absorption spectroscopy,DOAS)对南极中山站地区(69°22′24′′S,76°22′14′′E)的臭氧柱含量进行了72天(2008年12月10日-2009年2月19日)观测,通过被动差分吸收光谱处理方法对系统采集的天顶太阳散...     

基于特征匹配和校验的鲁棒实时电子稳像

提出了一种基于特征点匹配和校验的鲁棒实时电子稳像算法.首先利用Kanade-LucasTomasi角点检测器提取参考帧和当前帧的特征点,并用绝对误差和准则进行特征点匹配;在校验阶段,提出一种能够有效剔除前景运动物体特征点和错误匹配点的空间位置不变准则;最后,在相似运动模型下,利用最小二乘法求解全局运动矢量进行运动补偿....     

“中粒度噪声地图”概念及其构建思路

根据我国国情,提出用较少的优化监测点位形成中粒度噪声地图的构建方法.中粒度噪声地图的形成分为2个环节.一是噪声地图构建系统(平台)的形成,通过离线过程实现;二是噪声地图在线生成,包括贝济埃定义点z值测量、贝济埃曲面(线)调出、地面等效声源反演计算、等效声源的空间声场叠加.     

分光计的分步调节法

利用＂镜外法＂和＂最高最低位置法＂相结合的调节方法,使分光仪的调整更为简便、较适合初学者。     

舰艇抗冲击试验中爆距定位理论分析与计算简

在舰艇抗冲击试验中,爆距直接影响到对目标的毁伤效果,爆距的误差范围也直接影响到试验数据的处理,因此,依据爆距的要求,需要对爆源布放沉底后进行准确的定位. 准确计算出爆源布放至海底的位置尤为重要. 本文对试验中爆源布放后布放索及浮漂在水中的受力情况进行了分析,建立了爆源布放索-浮漂系统受力的数学模型,采用Runge-Kutta 方法和Newton 迭代法计算出浮漂的漂移量,并给出了具体的算例.     

Direct numerical simulation of quasi-three-level passive Q-switched laser

The Runge-Kutta method is used to solve numerically the rate equations of quasi-three-level passive Q-switched laser directly without any approximate treatment of these differential equations. The 946 nm self-Q-switched Cr,Nd:YAG laser is chosen for example to describe the details. The time-dependence of intra-cavity photon density is obtained and its detailed real-time changing process is reproduced in numerical solution. The curves of laser output parameters such as average output power, pulse width, repetition rate, pulse energy and peak power changing with different cavity conditions such as pump power, output coupler reflectivity, Cr,Nd:YAG crystal length, Nd³⁺ ion and Cr⁴⁺ ion concentrations are simulated according to direct numerical solution rather than analytical expressions. This direct numerical simulation method can be widely used to describe and optimize the quasi-three-level passive Q-switched laser theoretically.     

考虑三级货损成本的冷链物流配送中心选址优化

为解决冷链物流配送中心的选址优化问题,依据易腐品完好率线性递减理论,提出了易腐品完好率与运输距离之间的分段递减函数关系,通过分析从供应点到配送中心运输过程,配送中心内部操作过程和从配送中心到需求点配送过程中所产生的三级货损实际情况,探究了本级货损对下级货损的叠加影响,以货物完好量作为客户的最终需求,构建了考虑三级货损成本的冷链物流配送中心选址优化模型,算例验证了所建模型的适用性和可行性.     

带覆盖需求约束的设施选址问题

带覆盖需求约束的设施选址问题(FLPWCDL)研究:客户必须在规定的响应半径内被服务,并要求服务站能够覆盖规定的需求数量,如何选择合适的服务站,使总成本(建站成本+路线成本)最小.FLPWCDL广泛应用于应急服务、物流、便利店等服务站的选址.建立了问题的混合整数规划模型,并构造了求解FLPWCDL的Benders分解算法,计算实验显示Benders分解算法具有非常高的求解效率与求解质量.