35MeV/u 40Ar+197Au反应中热核的碎裂密度

许多提取核反应过程中熵产生的方法只适用于高能核反应过程,而约化d的产额方法可以用于较低能量的重离子核反应中.对于35MeV/u ⁴⁰Ar+¹⁹⁷Au的核反应过程,利用这种方法所得的熵和约化带电粒子多重性提取的熵结果一致.对于后角热核发射体系,实验提取的核温度为(4.7±1.2)MeV,熵为S/A=2.5±0.5,根据实验提取的熵和核温度可以确定其碎裂密度小于0.1ρ₀.     

35MeV/u~(40)Ar ~(197)Au中的熵产生

根据量子统计模型 (QSM )的计算分析 ,找到了一个提取核反应过程中熵产生的新的可观测量 .核反应过程中约化d的产额d/ (d t 3 He 4 He)和熵有单调的函数关系 ,并且和体系的碎裂密度 (ρ/ ρ0 )及体系的N/Z都无关 ,可以作为提取核反应过程中熵产生的一个观测量 .和目前已经有的其他方法相比 ,约化d产额这一提取熵方法可以用于较低能量的重离子核反应中 ,并且数据处理分析简单 .对于 35MeV/u4 0 Ar 197Au的核反应过程所提取的熵和利用约化带电粒子多重性提取的熵结果一致 .结合后角类靶热核发射体系实验提取的同位素核温度为 4 7±1 2MeV及S/A =2 5± 0 5 ,根据熵和核温度的关联关系 ,可以确定其Breakup密度接近但小于 0 1(ρ/ ρ0 )     

35MeV/u40Ar+197Au中的熵产生

根据量子统计模型(QSM)的计算分析,找到了一个提取核反应过程中熵产生的新的可观测量.核反应过程中约化d的产额d/(d+t+³He+⁴He)和熵有单调的函数关系,并且和体系的碎裂密度(ρ/ρ₀)及体系的N/Z都无关,可以作为提取核反应过程中熵产生的一个观测量.和目前已经有的其他方法相比,约化d产额这一提取熵方法可以用于较低能量的重离子核反应中,并且数据处理分析简单.对于35MeV/u⁴⁰Ar+¹⁹⁷Au的核反应过程所提取的熵和利用约化带电粒子多重性提取的熵结果一致.结合后角类靶热核发射体系实验提取的同位素核温度为4.7±1.2MeV及S/A=2.5±0.5,根据熵和核温度的关联关系,可以确定其Break up密度接近但小于0.1(ρ/ρ₀) 关键词： 熵 约化d产额 核温度 统计发射     

46.7MeV/u 12C引起的核反应中碎裂与转移的竞争

本文讨论了46.7MeV/u ¹²C引起的核反应中弹核碎裂与转移反应的共存及相互竞争,实验中提取的转移部分的约化平行动量分布宽度为44±10MeV/c,这比弹核碎裂部分的σ₀=80±10MeV/c要窄.弹核碎裂及转移反应发生的几率都与被转移结团的结构有关.     

46.7MeV/u~(12)C引起的核反应中碎裂与转移的竞争

本文讨论了46.7MeV/u~(12)C引起的核反应中弹核碎裂与转移反应的共存及相互竞争,实验中提取的转移部分的约化平行动量分布宽度为44±10MeV/c,这比弹核碎裂部分的σ_0=80±10MeV/c要窄。弹核碎裂及转移反应发生的几率都与被转移结团的结构有关。     

46.7MeV/u 12C引起的弹核碎裂反应

测量了46.7MeV/u ¹²C束流轰击不同靶核的核反应中前方向出射的类弹碎片,发现弹核碎裂产物的最可几能量可用Abrasion图象来解释.它们的平行动量分布宽度满足Goldhaber关系式,实验中提取的约化平行动量分布宽度σ₀=80±10MeV/c,接近于相对论情形下的值,并且σ₀对于不同的反应系统有相近的值.     

248 Cm和252Cf自发裂变瞬发中子谱测量

在飞行时间方法测量 2 0 0keV— 1 2MeV能区内2 48Cm和2 5 2 Cf自发裂变瞬发中子谱 ,以国际原子能机构推荐的2 5 2 Cf自发裂变瞬发中子谱为标准 ,可以免去探测器效率刻度的问题并消除系统误差 ,提高测量精度 .实验用一个微型电离室作为裂变碎片探测器 ,两个芪晶体中子探测器测量中子及一套基于微机的距离分别为 3 2 ,50和 1 0 0cm ,经过对数据的处理和分析给出了 2 0 0keV— 1 2MeV的中子能区内的实验数据 .用Maxwell分布对实验数据进行拟合 ,得到的核温度为 (1 4 0 1± 0 0 0 6)MeV .     

46.7MeV/u 12C诱发核反应中非稳态产物的布居及核温度的提取

本文报道了在46.7MeV/u ¹²C诱发的核反应实验中,利用测量轻带电粒子关联函数,来研究非稳定核及低激发核的粒子衰变方式的实验结果.在假定统计平衡的条件下提取了有关核温度参量,并研究了不同反应机制及靶核对提取的核温度的影响.     

中重核14.5MeV (n,2n),(n,3n)反应截面的系统学计算

本文从中子核反应机制出发,讨论(n,2n),(n,3n)反应过程,给出约化截面的计算公式.按照系统学方法计算z=58—83的53个中重核的14.5MeV (n,2n),(n,3n)反应截面,计算结果与实验值符合较好.     

14MeV中子引起的185Re(n,2n)184g,mRe和191Ir(n,2n)190Ir的核反应截面测量

利用活化方法测量了1?4MeV中子引起的¹⁸⁵Re(n,2n)^184gRe,¹⁸⁵Re(n,2n)^184mRe和¹⁹¹Ir(n,2n)¹⁹⁰Ir核反应的截面.中子能量E_n=(14.7±0.2)MeV时的实验结果分别为:(1817±85)mb,(390±18)mb和(2038±82)mb.并利用HFTT程序计算了中子能量在7—18MeV范围内的截面值,给出了其中两个核反应的激发函数曲线.     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Research on beamforming method for dual-line array with space mismatch between the two line arrays

The performance of port/starboard discrimination of dual-line array will be seriously degraded when the space between the two line arrays of the dual-line array is mismatched. The directivity function of the delay-sum and delay-subtract beamforming is deduced and the port/starboard discrimination of the delay-sum and delay-subtract beamforming is also studied both under the ideal status and the status under which the space between the two line arrays of the dual-line array is mismatched. Analysis results show the delay-subtract beamforming has better performance of port/starboard discrimination. At last, the sea trial results demonstrate the theoretical results.     

Retrieval of ultraviolet skylight radiances and O3 slant column densities from balloon-borne limb spectrometer

With a novel light-weight and absolutely calibrated ultraviolet （UV） spectrometer, UV skylight radiances and O3 slant column densities are measured by balloon-borne limb measurements in Xinjiang area, China. UV skylight radiances measured at the height of 31 km are compared with the results from Modtran in the wavelength range from 290 to 420 nm. O3 slant column densities are derived from radiance spectra in the Huggins bands （320 - 335 nm） using differential optical absorption spectroscopy method. And the parameter exhibits a good correlation with the same value simulated by radiative transfer model （Tracy）. The O3 profile simultaneously measured by an O3 sonde is used as input in Tracy calculations. The O3 sonde is launched on the same balloon.     

Design optimization of highly sensitive LSPR enhanced surface plasmon resonance biosensors with nanoholes

For breaking through the sensitivity limitation of conventional surface plasmon resonance (SPR) biosensors, novel highly sensitive SPR biosensors with Au nanoparticles and nanogratings enhancement have been proposed recently.But in practice, these structures have obvious disadvantages.In this study, a nanohole based sensitivity enhancement SPR biosensor is proposed and the influence of different structural parameters on the performance is investigated by using rigorous coupled wave analysis (RCWA).Electromagnetic field distributions around the nanohole are also given out to directly explain the performance difference for various structural parameters.The results indicate that significant sensitivity increase is associated with localized surface plasmons (LSPs) excitation mediated by nanoholes.Except to outcome the weakness of other LSP based biosensors, larger resonance angle shift, reflectance amplitude, and sharper SPR curves' width are obtained simultaneously under optimized structural parameters.     

Polymer gratings based on photopolymerization for low-order distributed feedback polymer lasers

Novel polymer distributed feedback(DFB)gratings are fabricated based on photopolymerization to reduce lasing threshold of polymer lasers.A photopolymer formulation sensitive to 355-nm ultraviolet(UV)light is proposed for the fabrication of polymer gratings and it can be used to form polymer films by spin-coating process.A very low surface-relief depth ranging from 12.5 to about 1.0 nm has been demonstrated with a refractive-index modulation of about 0.012.The experimental results indicate that such polymer gratings have promising potentials for the fabrication of low-order DFB organic semiconductor lasers.     

A novel methodology for photometric compensation of projection display on patterned screen

We propose a novel methodology based on the projector-camera (ProCam) system to address the photometric compensation issue for the projection display on the patterned screen.The patterned screen is treated as the combination of a perfect white screen and a color modulator.The perfect white screen is used to automatically and accurately characterize the ProCam system offline using the polynomial model,and the parameters of the color modulator can be efficiently recovered by employing only two gray images based on the linear reflectance model.The experimental results show that the color artifacts of the display image can be greatly improved with this methodology,which demonstrates its feasibility and validity in the photometric compensation.     

Direction-of-arrival estimation using matrix spatial prefiltering approach

An approach to direction-of-arrival （DOA） estimation for multiple narrowband farfield signals is proposed. The technique uses a novel matrix spatial prefiltering approach. Specifically, a matrix filter is designed to spatially filter the incoming data snapshots. The un-wanted components arriving from the stopband angular sectors are attenuated and the desired components from the angular sector of interest pass with minimal distortion. The matrix filter spatially filters the element-space data and the output reserves the element-space data property, which makes it very useful by passing sensor data through a spatial prefilter prior to applying many other array processors to attenuate interferences and improve system performance. Several examples of DOA estimation problem are presented to illustrate the performance of the proposed spatial prefiltering approach. Results of simulation and real data show that the pre-filter can efficiently attenuate the spatial interferences and significantly improve the estimation and resolution capability of DOA estimators at low signal-to-noise ratios for the sources located inside the passband sector. In addition, the use of spatial prefilter makes it possible to estimate DOAs for multiple sources more than the number of the elements of an array.     

Quantum efficiency calibration of opto-electronic detector by means of correlated photons method

A new calibration method of detectors can be realized by using correlated photons generated in spontaneous parametric down-conversion (SPDC) effect of nonlinear crystal.An absolute calibration system of detector quantum efficiency is performed.And its principle and experimental setup are introduced.A continuouswave (CW) ultraviolet (351 nm),diode-pumped,frequency-doubled,and solid-state laser is used to pump BBO crystal.The quantum efficiencies of the photomultiplier at 633,702,and 789 nm are measured respectively.The coincidence peaks are observed using coincidence circuit.Some measurement factors including the filter bandwidth of trigger channel,the detector position alignment and polarization of the pump light are analyzed.The uncertainties of this calibration method are also analyzed,and the relative uncertainties of total calibration are less than 5.8%.The accuracy of this method could be improved in the future.