MRTD算法在集成平面光波导组件分析中的应用

将基于Daubechies紧支集尺度函数的时域多分辨分析（MRTD）算法用于集成平面光波导组件的时域分析中,实现了MRTD算法的各向异性理想匹配层（APML）吸收边界条件,并对平行介质带定向耦合器进行了数值模拟和验证,所得结果与解析解非常一致.与传统的FDTD算法相比,MRTD算法在不牺牲计算精度的前提下能够大大节省计算资源.     

BEPC-LINAC试验束上1GeV/c多粒子磁谱仪的设计和性能测量

试验束上2Q2D结构的磁谱仪系统由2块二极磁铁和2块四极磁铁以及位置灵敏探测器组成.该磁谱仪的接收立体角5×10^–4sr,动量范围0.2—1.3GeV/c.测量了聚焦面上的束流截面和动量谱.介绍了一种测量电子与质子飞行时间差的动量测量方法.     

一种三环并联Rayleigh后向散射式光纤转动传感器

以单环后向Rayleigh散射式光纤转动传感器原理为基础,提出了一种三环形腔并联Rayleigh后向散射式光纤转动传感器新结构.利用三个2×2单模光纤耦合器,建立了并联三环形腔Rayleigh后向散射式光纤转动传感器的理论模型,给出了用光时域反射计（OTDR）探测到的信号强度表达式.通过计算机仿真优化了参量,选择三环的长度分别为1 500 m、1 078 m和680 m.三个2×2光纤耦合器的耦合系数分别为95.23%、94.88%和95.26%构建了测试系统,对不同转速所探测到的后向Rayleigh散射信号进行测量,得到与理论相一致的实验结果.三环的采用,增加了测试的有效数据,使其更有利于识别,提高了测量转速的准确度.     

Performance of a four‐element Si drift detector for X‐ray absorption fine‐structure spectroscopy: resolution, maximum count rate,and dead‐time correction with incorporation into the ATHENA data analysis software

The performance of a four‐element Si drift detector for energy‐dispersive fluorescence‐yield X‐ray absorption fine‐structure measurements is reported, operating at the National Institute of Standards and Technology beamline X23A2 at the National Synchrotron Light Source. The detector can acquire X‐ray absorption fine‐structure spectra with a throughput exceeding 4 × 10⁵ counts per second per detector element (>1.6 × 10⁶ total counts per second summed over all four channels). At this count rate the resolution at 6 keV is approximately 220 eV, which adequately resolves the Mn Kα and Kβ fluorescence lines. Accurate dead‐time correction is demonstrated, and it has been incorporated into the ATHENA data analysis program. To maintain counting efficiency and high signal to background, it is suggested that the incoming count rate should not exceed ～70% of the maximum throughput.     

聚合物微环电光开关的模拟和优化

利用耦合模理论、电光调制理论和微环谐振理论,提出一个完善合理的聚合物微环电光开关的器件模型,并给出了可用以分析微环谐振过程的光强传递函数,据此在谐振波长1 550 nm下对该器件进行了模拟和优化.结果表明：微环波导芯截面尺寸为1.8×1.8 μm2,波导芯与电极间的限制层厚度为1.1 μm,电极厚度为0.15 μm,微环半径为15.2 μm,微环与信道间的耦合间距为0.16 μm,光绕微环转300 圈即可形成稳定的谐振状态,此时的谐振时间约为147.4 ps.不加电压时,下信道的插入损耗约为0.8 dB,上信道的串扰约为－26 dB;当取工作电压等于19.7 V为开关电压时,上信道的插入损耗约为0.34 dB,下信道的串扰约为－20 dB.     

A study of time over threshold (TOT) technique for plastic scintillator counter

A new charge measurement method, time over threshold (TOT), has been used in some gas detectors lately. Here TOT is studied for TOF system, made of plastic scintillator counter, which can simplify the electronics of the system. The signal characteristics are measured and analyzed with a high quality oscilloscope, including noise, pedestal, signal amplitude, total charge, rise time and the correlation between them. The TOT and charge are related and can be fitted by some empirical formula. The charge measurement resolution by TOT is given and this will help the design of TOF electronics.     

Performance analysis of an integrated scheme in optical burst switching high-speed networks

A new integrated scheme based on resource-reservation and adaptive network flow routing to alleviate contention in optical burst switching networks is proposed. The objective of the proposed scheme is to reduce the overall burst loss in the network and at the same time to avoid the packet out-of-sequence arrival problem. Simulations are carried out to assess the feasibility of the proposed scheme. Its performance is compared with that of contention resolution schemes based on conventional routing. Through extensive simulations, it is shown that the proposed scheme not only provides significantly better burst loss performance than the basic equal proportion and hop-length based traffic routing algorithms, but also is void of any packet re-orderings.     

Preparing of coherent superposition state in serial multi-A-type system by stimulated Raman adiabatic passage

A scheme for creating an arbitrary coherent superposition of two atomic states in serial multi-A-type system is proposed.This technique with the application of a control field is based on the existence of two degenerate dark states and their interaction.The mixing of the dark states can be controlled by changing the relative delay time of the control pulse.One can get any desired superposition by changing the delay time of the control pulse.     

飞秒时间分辨光抽运探测技术及进展

文章简要介绍了飞秒时间分辨光抽运探测技术以及作者所在实验室的最新研究进展．灵敏度和信噪比是实验中的重要参数，文章着重介绍了作者在这两方面的改进，从而可检测到更微弱信号，并降低了使用的激光功率．配合具有光学窗口的液氦低温系统，还可对更多领域的材料进行研究，其中包括高温超导、生物化学样品和纳米材料等，并可给出物质内部结构等方面的重要信息．     

Dielectric studies in dilute solutions

Dielectric studies in dilute solutions of cyclohexane and benzene have been carried out in the temperature range 294–318°K. The observed data have been utilized to evaluate the relaxation times and thermodynamic parameters of these molecules. The high values ofα for 2-acetyl pyridine indicate the occurrence of more than one relaxation time. In the remaining systems, the observed lowα values indicate their rigid behaviour. The variation in the dielectric relaxation time is mostly correlated with the change in the heterocyclic configuration of the system.