北京谱仪III上利用神经网络方法进行粒子鉴别的研究

本文描述了一种多层感知器的神经网络系统在BESIII粒子鉴别技术中的应用。网络按照子探测器分别进行训练, 输出结果可以作为后续网络的输入或者可以为似然函数方法构建概率密度函数。蒙特卡罗模拟样本的检验结果表明, 利用神经网络方法可以在BESIII上获得较好的粒子鉴别效果。     

The influence of time delay on forward masking when spatially separated sound image reproduced with headphone

With the virtual reproduction of headphone, the influence of delay time between masker and masked signal on forward masking when sound images are virtually spatial separated in azimuth is studied. The result shows that the thresholds tend to decrease dramatically with the increase in delay time. Furthermore, in case of spatial separation, there are differences of masking thresholds with the maximum about 15 dB. However, when the masker level is 70 dB, the difference of the thresholds increases a little as the delay time increases from 20 ms to 40 ms, which can be explained by the time integration effect and basilar membrane response.     

Research of the planar optical fiber Bragg grating hydrophone probe

This paper presents the planar Fiber Bragg Grating （FBG） hydrophone probe sensing principle, and theoretically and experimentally researches the probe structure sensitivity, the receiving sensitivity frequency response characteristic and the acceleration response property. Planar sheet is made of stainless steel, its thickness is 0.15 mm, its diameter is 15mm, and the length of hollow circular shell is 20 mm. For this size of the structure, the probe structure sensitivity is up to 23 fm/Pa, which is about 7300 times of the value of the bare fiber. The resonance frequency is 6.5 kHz, and the amplitude-frequency curve of the receiving sensitivity response is relatively flat within the frequency range of 100 Hz to 5.5 kHz. The output yielded by one unit acceleration （1m/s2） is equivalent to （2.52 to 3.26 Pa） acoustic pressure acting output. This probe structure is easy to form FBG hydrophone array by multiplexing technique. The research shows that this planar structure not only can form FBG hydrophone probe, but also can constitute optical FBG laser hydrophone probe. The structure can realize different bandwidth, different range acoustic pressure measurement by adjusting the geometrical size of the sheet.     

Pt/Ti Electrodes of PZT Thin Films Patterning by Novel Lift-Off Using ZnO as a Sacrificial Layer

We achieve a successful novel lift-off of patterning Pt/Ti electrodes on SiO2/Si substrates by employing ZnO sacrificial layer deposition and patterning, successive uniform Pt/Ti deposition and final lift-off. Then we deposit PZT thin films on the electrodes. Compared with the conventional lift-off processes for the electrodes, this novel process does not need post-annealing, which must be performed after conventional lift-off process. It is demonstrated that the electrodes patterned by the novel lift-off process have stronger adhesion. The electrodes and the PZT films on the electrodes are more compact and smoother than those by the conventional lift-off process.     

A New Conserved Quantity Corresponding to Mei Symmetry of Tzenoff Equations for Nonholonomic Systems

A new conserved quantity is investigated by utilizing the definition and discriminant equation of Mei symmetry of Tzénoff equations for nonholonomic systems. In addition, the expression of this conserved quantity, and the determining condition induced new conserved quantity are also presented.     

Determination of Orientations in Deformed U--U Collisions at 0.52GeV/u

The ART model is applied to study the deformed UU collision at HIRFL-CSR energy area corresponding to the high baryon density region in the QCD phase diagram. The time evolution of central baryon (energy) densities in central collisions at E_b =0.52GeV/u shows that different orientation collisions will lead to different lifetimes of high density, especially tip--tip UU collisions which have an extend lifetime for the high density phase by almost a factor of 2 compared to the body--body orientation collisions. In order to pick out the interesting tip--tip like events from a mass of random orientation collisions, we study the relation between stopping power R and impact parameter b in different orientation collisions and find that it can enhance the purity of tip--tip like events when R increases. Therefore, the high density and long lifetime events can be effectively distinguished by R selection.     

Structural and Photoluminescence Properties of β-Ga2O3 Nanofibres Fabricated by Electrospinning Method

We have prepared the 13-Ga2 O3 nanofibres by electrospinning method followed by calcining in air at 900℃. The morphology and structure of the nanofibres are characterized by field emission scanning electron microscopy （FE-SEM）, x-ray diffraction （XRD） and Raman technique. These nanofibres have diameters ranging from 60 to 130hm and lengths up to several millimetres. Photoluminescence （PL） spectrum under excitation at 325 nm shows that theseβ-Ga2 O3 nanofibres have a blue emission peaking at 466nm, which may be attributed to defects such as the oxygen vacancies, gallium vacancies and gallium-oxygen vacancy pairs.     

Effect of Aspect Ratio Distribution on Localized Surface Plasmon Resonance Extinction Spectrum of Gold Nanorods

Gold nanorods with different aspect ratios are prepared in micells using a seeded growth method. Their extinction spectra are observed with an UV-visible spectrophotometer and analysed theoretically. It is known that there are two plasmon resonance peaks for gold nanorod corresponding to transverse and longitudinal plasmon resonance respectively. Moreover, the longitudinal plasmon resonance peak shifts to long wavelength when we increase the aspect ratio determined from TEM. Especially, we model the extinction spectrum using Gans' theory and compare it with our experimental result. Considering the aspect radios distribution of gold nanorods, it is found that longitudinal plasmon resonance peak will be wider than the nanorods with single aspect ratio, which is consistent with our experimental result. In addition, the effect of dielectric constant of surrounding medium is considered.     

Photonic Crystal Fibre SERS Sensors Based on Silver Nanoparticle Colloid

A photonic crystal fibre （PCF） surface enhanced Raman scattering （SERS） sensor is developed based on silver nanoparticle colloid. Analyte solution and silver nanoparticles are injected into the air holes of PCF by a simple modified syringe to overcome mass-transport constraints, allowing more silver nanoparticles involved in SERS activity. This sensor offers significant benefit over the conventional SERS sensor with high flexibility, easy manufacture. We demonstrate the detection of 4-mercaptobenzoic acid （4-MBA ） molecules with the injecting way and the common dipping measurement. The injecting way shows obviously better results than the dipping one. Theoretical analysis indicates that this PCF SERS substrate offers enhancement of about 7 orders of magnitude in SERS active area.     

钙原子4p_(1/2,3/2)ng(J=3)自电离Rydberg光谱的研究

利用Monte Carlo(MC)方法模拟研究了薄膜生长的初始阶段岛的形貌和岛的尺寸与基底温度和入射粒子剩余能量之间的关系.模型中考虑了粒子的沉积、吸附粒子的扩散和蒸发等过程.结果表明当基底温度从200K变化到260K时,岛的形貌经历了一个从分散生长逐渐过渡到分形生长的过程,并且在较低温度(200K)下,随入射粒子剩余能量的增加,岛的形貌也经历了同样的变化过程.进一步研究证明,随着基底温度的升高或入射粒子剩余能量的增加,沉积粒子的扩散能力显著增强,从而使岛的形貌发生了改变.