惯性约束聚变的中子半影成像诊断系统的优化研究

在激光驱动的惯性约束聚变实验中,中子半影成像是重要的诊断方法.基于分辨率的要求,模拟了中子源与半影孔装置间不同距离、半影孔装置不同厚度、半影孔装置不同外径以及不同孔型的系统点扩展函数,通过分析点扩展函数的尖锐性和等晕性优化诊断系统.同时还给出了系统的装配误差要求,并发现系统在线性重建时能达到15 μm分辨率,而非线性重建时能满足5 μm分辨率的诊断要求. 关键词： 中子半影成像 Monte Carlo方法 系统优化 分辨率     

Multiparty quantum secret sharing based on Bell measurement

A multiparty quantum secret sharing scheme based on Bell measurement is proposed and analyzed. In this scheme, all agents are not required to prepare entangled states or perform any local unitary operation. The security of the protocol is also analyzed. It is shown that any eavesdropper will introduce errors invariably and be detected if he tries to steal information about Trent’s secret. Moreover, because no classical bit needs to be transmitted except those for detection, the total efficiency of the scheme approaches to 100%.     

Haldane's instanton in 2D Heisenberg model revisited: Along the avenue of topology

Deconfined quantum phase transition from Néel phase to valence bond crystal state in 2D Heisenberg model is under debate nowadays. One crucial issue is the suppression of Haldane's instanton on quantum critical point which drives the spinon deconfined. In this Letter, by making use of the ?-mapping topological current theory, we reexamine the Haldane's instanton in an alternative way along the direction of topology. We find that the monopole events are space-time singularities of Néel field , the corresponding topological charges are the wrapping number of around the singularities which can be expressed in terms of the Hopf indices and Brouwer degrees of ?-mapping. The suppression of the monopole events can only be guaranteed when the ?-field possesses no zero points. Moreover, the quadrapolarity of monopole events in the Heisenberg model due to the Berry phase is also reproduced in this topological argument.     

有机半导体的物理掺杂理论

基于最低未被占据分子轨道（LUMO）和最高被占据分子轨道（HOMO）的高斯态密度分布与载流子在允许量子态中的费米-狄拉克（Fermi-Dirac）分布,提出有机半导体中物理掺杂的理论模型;研究了掺杂浓度、温度和禁带宽度对载流子浓度的影响,并与一些报道的实验结果做了比较.研究发现无论是否掺杂,温度升高时,有机半导体中的载流子浓度都会增大,并且随温度倒数的线性减小而指数增大;对于本征有机半导体,载流子浓度随禁带宽度的增大而指数下降,随高斯分布宽度的平方指数增加;对杂质和主体不同能级关系的掺杂情形下掺杂浓度对载 关键词： 有机半导体 掺杂 高斯态密度 载流子浓度     

矩形微管内摩擦阻力特性的实验研究

以极性液体蒸馏水、无水乙醇及非极性液体R113作为实验工质,流过水力直径为231.91μm、250.88μm、297.14pm和210.89 pm,相应高宽比分别为0.90、0.70、0.90和0.42的由晶体生长方法得到的矩形紫铜微管,其相对粗糙度分别为1.47%、1.59%、1.48%和1.45%,测量其进出口压降与流量,从而获得摩擦阻力系数f与雷诺数Re的关系.实验结果表明:微管内流体的极性对微管流动阻力特性没有影响;同时实验结果显示对于粗糙度小于2%的矩形紫铜微管,其内壁面粗糙度对其流动阻力特性影响较小.当Re小于1600时,所有微管内的流动阻力特性与经典层流预测值几乎一致;而对于高宽比较小的矩形紫铜微管,当Re超过1600～1700时,微管的,值明显偏离经典层流预测值.     

Electro-acupuncture promotes survival, differentiation of the bone marrow mesenchymal stem cells as well as functional recovery in the spinal cord-transected rats

Background  

Bone marrow mesenchymal stem cells (MSCs) are one of the potential tools for treatment of the spinal cord injury; however, the survival and differentiation of MSCs in an injured spinal cord still need to be improved. In the present study, we investigated whether Governor Vessel electro-acupuncture (EA) could efficiently promote bone marrow mesenchymal stem cells (MSCs) survival and differentiation, axonal regeneration and finally, functional recovery in the transected spinal cord.     

非晶/结晶共混对聚合物光伏电池性能的影响

以局域规整聚（3-己基噻吩） （P3HT）制备了TiO₂/聚合物型双层结构光伏电池.利用稳态电流-电压测试和动态强度调制光电压谱,结合差热分析、吸收光谱和荧光光谱, 研究了非晶支化聚亚乙基亚胺（BPEI）作为P3HT膜层的添加成分对TiO₂/P3HT双层电池性能的影响.由于P3HT链的高结晶性,使得TiO₂/P3HT界面接触不好,导致电池性能差.当在P3HT中共混重量比W_BPEI/P3HT=1％—5％的BPEI时,电池性能得到显著改善;尤其是当W_BPEI/P3HT= 1％时,电池表现出近0.8V的开路电压和20μA/cm²的短路电流.结果表明BPEI对电池性能的影响不是源于P3HT-BPEI共混体系光学性能的变化,而主要是由于其改变了TiO₂/P3HT界面接触性能.BPEI对TiO₂/P3HT界面接触有两个相互竞争的影响,这取决于P3HT-BPEI共混体系的组成.一方面,通过降低P3HT的结晶度和增强与TiO₂表面的相互作用,改善P3HT链在TiO₂ 表面的附着;另一方面,当BPEI含量过高时,BPEI在TiO₂表面的附着量将增加,反而会阻碍P3HT与TiO₂表面的接触.良好的TiO₂/P3HT界面接触有利于提高激子的界面分离效率、光生电子的寿命和电池效率.本文结果有望为聚合物光伏电池性能的改善提供新的认识和方法. 关键词： 聚（3-己基噻吩） 二氧化钛 共轭聚合物 光伏电池     

荧光褪色效应与拉曼光谱基线干扰消除

荧光是直接测定的拉曼光谱中背景的最主要来源,需要采用真实、准确的方法消除,以得到纯净的拉曼响应。基线拟合消除和查找荧光贡献扣除是解决背景问题的两条思路,目前多采用基线拟合方法,其优点是满足用户“视觉”要求,无需额外硬件,但并非机理或实质上的解释,因而难以保证数据的真实性与合理性;查找荧光的方法,更为真实,但是目前提出的方法,需要增加光源等额外设计和成本。另外,在实验方法上,也有采用消荧光剂和长时间照射漂白的,存在操作繁琐、效率低等不足。利用稳定体系中拉曼和荧光的时间差异解决体系中荧光问题。在微小的时间段内,例如几个毫秒,激发光不会导致体系性质发生显著变化,荧光具有寿命周期,会随激发时间延长强度下降的“褪色”,“褪色”的强度差异可以被认为是整体荧光的一个微元;与此同时,由于体系组成未发生显著变化,拉曼光对于短时间照射可以保持稳定。利用此差异可以区分出混合信号中的荧光和拉曼光。根据该原理,提出了荧光褪色差分法(FBDA),实现拉曼光谱的背景校正。方法的主要步骤：测量微小时刻内的多张直接拉曼光谱,求取系列光谱的差分,对差分值作高频滤波降噪,可获得荧光强度微元;然后,多个荧光微元平均归一化后,得到荧光强度单元。以拉曼光谱2 000～2 500 cm-1的静默区,即通常不会出现拉曼信号的频段为基准,对荧光单元作逆差分,逆差分累计值与原始光谱在此频段一致时,得到整体荧光响应;最终,从原始光谱中扣除荧光成分,完成背景扣除和基线校正。以盐酸二甲双胍片的拉曼测量为例,说明和讲解了所提出的原理和方法,验证方法的有效性。与目前效果较好的基线校正方法(不对称最小二乘和自适应迭代再加权惩罚偏最小二乘)进行了对比,表明FBDA方法更为客观真实,FBDA的另一个优势是不需要额外的设计和成本,所有数据都是在现有设备直接采集和完成。需要说明的是,微小时刻光谱差异的要求,可以确保FBDA光谱实时性,长时间的光谱差异,将会影响结果的准确性;另外,对于光化学反应体系和其他非荧光引起的复杂背景,FBDA的适用性有待改善。     

SnS Nanosheets for 105th Harmonic Soliton Molecule Generation

As a member of the 2D group IV monochalcogenides (MX; M = Sn, Ge; X = S, Se), SnS has attracted great interest due to its outstanding optical, electrical, and optoelectronic properties. Especially, SnS nanosheets material have a large absorption coefficient and high photoelectric conversion efficiency, it can be potentially used in optical modulators, saturable absorbers, solar cells, supercapacitors, and other optical devices. However, the nonlinear optical properties of SnS nanosheets and their applications in ultrafast photonics are seldom studied. In this paper, the nonlinear optical properties of SnS nanosheets have been characterized through a dual‐balance detection system, whose modulation depth is 5.8%. More importantly, 105th harmonic soliton molecule based on SnS saturable absorbers has been realized for the first time to the authors’ knowledge. A compact mode‐locked fiber laser with a pulse duration of 1.02 ps and a repetition rate of 459 MHz is realized near 1.5 µm. It is demonstrated that SnS nanosheets have outstanding nonlinear properties and play an extremely important role in the field of ultrafast photonics.     

Study of theoretical tensile strength of Fe by afirst-principles computational tensile test

This paper employs a first-principles total-energy method to investigate the theoretical tensile strengths of bcc and fcc Fe systemically. It indicates that the theoretical tensile strengths are shown to be 12.4, 32.7, 27.5~GPa for bcc Fe, and 48.1, 34.6, 51.2~GPa for fcc Fe in the [001], [110] and [111] directions, respectively. For bcc Fe, the [001] direction is shown to be the weakest direction due to the occurrence of a phase transition from ferromagnetic bcc Fe to high spin ferromagnetic fcc Fe. For fcc Fe, the [110] direction is the weakest direction due to the formation of an instable saddle-point `bct structure' in the tensile process. Furthermore, it demonstrates that a magnetic instability will occur under a tensile strain of 14%, characterized by the transition of ferromagnetic bcc Fe to paramagnetic fcc Fe. The results provide a good reference to understand the intrinsic mechanical properties of Fe as a potential structural material in the nuclear fusion Tokamak.