一类具有四条分界射线的近哈密顿系统的极限环分支（英文）

应用分片光滑近哈密顿系统一阶Melnikov函数方法,研究一类由四个角形区域合成的全局中心的极限环扰动分支.当扰动项为n次多项式时,给出由中心分支出来的极限环的个数的上下界.     

关于X射线同轴位相衬度成像的研究

利用模糊函数对部分相干源相X射线衬成像进行了详细的理论分析.列举了不同条件下的实验结果.通过与吸收成像相比较,相衬成像无疑对生物样品的内部结构有更高的对比度和可见度.     

Waveguides Induced by Screening-Photovoltaic Solitons in Biased Photorefractive-Photovoltaic Crystals

We investigate theoretically waveguides induced by screening-photovoltaic solitons in biased photorefractive-photovoltaic crystals. We show that the number of guided modes in a waveguide induced by a bright screening photovoltaic soliton increases monotonically with the increasing intensity ratio of the soliton, which is the ratio between the peak intensity of the soliton and the dark irradiance. On the other hand, waveguides induced by dark screening-photovoltaic solitons are always single mode for all intensity ratios and the confined energy near the centre of a dark screening-photovoltaic soliton increases monotonically with the increasing intensity ratio. When the bulk photovoltaic effect is neglectable, these waveguides are those induced by screening solitons. When the external field is absent, these waveguides predict those induced by photovoltaic solitons.     

缺陷增强铜/金刚石界面热导的分子动力学研究

铜和金刚石热载流子不同且声子态密度差异大,限制了其界面热输运。本文采用分子动力学模拟对铜和金刚石的界面热输运机理进行探究,提出通过对界面附近纳米尺度的金刚石层添加缺陷来改善其与铜的界面声子耦合。计算结果表明,在缺陷浓度为0.08时,铜和金刚石的界面热导比未添加缺陷时提高了89.2%。并进一步发现,虽然有缺陷的金刚石薄层自身热导率有所下降但仍远高于一般的热界面材料,因此界面处的集总热阻仍然得到了大幅降低。     

High resolution spectroscopy of Rb in magnetic field by far-detuning electromagnetically induced transparency

We have presented a high resolution spectroscopy of Rb in magnetic field by far-detuning electromagnetically induced transparency (EIT). The EIT spectrum in the $Xi$-type configuration is usually companied by a double resonance optical pumping (DROP) due to the strong optical coupling between the two upper states, leading to the spectral lines seriously deformed and widely broadened for complex relaxation processes in DROP. Here we demonstrate a high resolution spectroscopy by far-detuning EIT for $^{87}rm{Rb}$ $rm{5S_{1/2}rightarrow5P_{3/2}rightarrow5D_{5/2}}$ in magnetic fields. The method of far-detuning eliminates the relaxation in DROP to the most extent and decreases the spectral linewidth from more than 20 MHz down to its natural linewidth limit (6 MHz). The deformation of the spectral lines also disappears and the observed spectra are well in accordance with the theoretical calculation. Our work shows that far-detuning EIT is a reliable high resolution spectroscopic method when the relaxation in DROP cannot be neglected, especially for the case of transition to low excited states.     

Two Optical Feedback Schemes for Cavity Ring-down Technique for High Reflectivity Measurements

An optical feedback cavity ring-down （OF-CRD） technique employing a continuous wave Fabry—Perot （F-P） diode laser is investigated for high reflectivity measurement. Two optical feedback （OF） schemes （linear and V-shaped cavity schemes） for the OF-CRD technique are compared in both wavelength and time domains. Due to the OF effect caused by retro-reflection of ring-down cavity back into the laser cavity, large resonance peaks appear in CRD signals in both the schemes. However, due to the differences in the strengths and spectra of the OF, the appearance frequencies and amplitudes of the peaks in the CRD signals in both schemes differ significantly. Simple and low-cost high reflectivity measurement apparatuses are established based on these two OF-CRD schemes and high-accuracy measurements of high reflectivity are experimentally achieved.     

用Judd-Ofelt理论计算TmP5O14晶体中Tm3+的光谱参数

根据Judd-Ofelt理论,测得了Tm3+ 在TmP5O14晶体中的强度参数分别为Q2=:1.50×10-20cm2,Q4=1.51×10-20cm2,Q6=0.916×10-20cm2,计算的振子强度Pcal.与实验值Pexp.符合较好,平均根方误差为2.60×10-7。求得Qλ后,计算了J多重激发态之间的振子强度,自发辐射跃迁速率,辐射寿命和荧光分支出,与YAlO3:Tm3+,YAG:Tm3+、Y2O3:Tm3+等晶体和掺Tm3+玻璃的光谱参数进行了比较,并就3H4→3H6,3F4→3H5,1D2→3H4和1G4→3H4的跃迁进行了对比和讨论。观察到Tm3+在不同介质中的Pexp.与强度参数的总和∑τλ=τ2+τ4+τ6存在Pexp=α∑τλ+b的关系。     

石墨烯对Ni（OH）2超级电容器材料电化学行为的影响

研究了氧化缺陷石墨烯对Ni(OH)2电化学性能的增强作用.实验上,由恒电位沉积法在石墨烯基底上制备Ni(OH)2纳米粒子/石墨烯复合材料.TEM观察和电化学测试表明,Ni(OH)2纳米粒子均匀地分散在石墨烯基底上,其粒径为5.0±0.5 nm,体系的质量比电容值为1928 F.g-1.量化计算表明,上述复合材料乃是通过Ni(OH)2与石墨烯表面功能基团的强化学作用相结合而导电的,电子则是自石墨烯基底经氧化缺陷向Ni(OH)2传递,导致Ni(OH)2带负电,从而形成Ni(OH)2纳米粒子的单向导电行为.     

基于FPGA和蓝牙的远程图像采集同步系统

针对核物理实验中高精度时间同步触发图像采集系统的要求,设计了一套基于FPGA和蓝牙的远程图像采集同步系统。该系统以FPGA作为主控制器,负责USB 接口通信、命令解析、蓝牙通信和同步控制等,触发信号延时精度可达10 ns;使用RS485 或TTL 标准以适应长距离触发和短距离触发,通过GigE 千兆网口实现远程图像数据采集。采用LabVIEW 开发了上位机图形化软件界面,基于蓝牙BLE4.0 协议,实现了基于手机APP的无线终端控制,完成了对相机延时时间、同步触发脉冲宽度、图像采集等命令的同步控制。A image acquisition and synchronization control system based on FPGA (Field Programmable Gate Array) and bluetooth is studied in this paper. FPGA as the main controller is responsible for USB (Universal Serial BUS) interface, command analyze, delay control, and trigger signal generation. Trigger signal can be RS485 or TTL. RS485 signals can be used for long-distance transmission without distortion while TTL is suitable for near field. The system's delay accuracy is reached to 10ns. It can be obtain images from GigE Ethernet port. Meanwhile,a PC graphical control software is developed by LabView. And based on the Bluetooth BLE4.0 protocol, a Android mobile phone APP is developed for wireless control.     

高能闪光照相密度测量的LEPM方法

研究了利用高能闪光照相方法实现密度分布测量的技术.根据闪光照相投影成像原理,将成像过程中的非线性成像因素看成一个综合性的非线性算子,利用先验测量的方法该非线性算子的响应曲线,利用该曲线校正成像图像得到待测客体的光程分布图像.采用以最小误差为重建准则的代数重建法,从光程分布图像中重建出照相客体的线吸收系数分布.最后利用相对等效质量吸收系数以及客体总质量不变的约束条件,获得照相客体的空间密度分布.在高能闪光照相实验平台上进行了静态客体的密度测量实验,测量的均方根误差约为10％.