Synthesis and magnetic properties of multilayer Ni/Cu and NiFe/Cu nanowires

Highly ordered composite nanowires with multilayer Ni/Cu and NiFe/Cu have been fabricated by pulsed electrodeposition into nanoporous alumina membrane. The diameter of wires can be easily varied by pore size of alumina, ranging from 30 to 100 nm. The applied potential and the duration of each potential square pulse determine the thickness of the metal layers. The nanowires have been characterized by transmission electron microscopy (TEM), magnetic force microscopy (MFM), and vibrating sample magnetometer (VSM) measurements. The MFM images indicate that every ferromagnetic layer separated by Cu layer was present as single isolated domain-like magnet. This technique has potential use in the measurement and application of magnetic nanodevices.     

Gamma rays from dark matter annihilation in the Draco and observability at ARGO

The CACTUS experiment recently observed a gamma ray excess above 50 GeV from the direction of the Draco dwarf spheroidal galaxy. Considering that Draco is dark matter dominated, the gamma rays may be generated through dark matter annihilation in the Draco halo. In the framework of the minimal supersymmetric extension of the standard model we explore the parameter space to account for the gamma ray signals at CACTUS. We find that the neutralino mass is constrained to be approximately in the range between 100 GeV∼400 GeV and a sharp central cuspy of the dark halo profile in Draco is necessary to explain the CACTUS results. We then discuss further constraints on the supersymmetric parameter space by observations at the ground-based ARGO detector. It is found that the parameter space can be strongly constrained by ARGO if no excess from Draco is observed above 100 GeV.     

Two-pump fiber optical parametric amplifiers using optimized photonic crystal fiber by genetic algorithm

In this paper, we investigate the gain spectra of fiber optical parametric amplifiers (FOPAs) consisting of dispersion-flattened fibers (DFFs) with different dispersion curves comparatively by means of the dispersion curve model of the DFFs. It is demonstrated that the broader gain spectrum of FOPAs can be achieved if the dispersion curve is lower and more flattened. Based on the preceding analyses, we propose to constitute FOPAs by using index-guiding photonic crystal fiber (PCF) with an anticipated ultra-flattened dispersion and ultra-low dispersion slope. The as-proposed PCF had different air-holes in the cladding rings. In total, four parameters of the PCF are optimized by using genetic algorithm. PACS 42.81.-i; 42.65.Hw; 42.65.Yj     

热加工对花生过敏原Ara h 2抗原性及构象的影响

从花生种子中分离纯化花生过敏原Ara h 2,采用酶联免疫吸附试验(ELISA)、圆二色谱(CD)、ANS荧光探针及紫外可见(UV-Vis)光谱等方法,系统研究热加工对Ara h 2抗原性和结构的影响.结果表明:Ara h 2蛋白经55或70℃处理后其抗原性略有升高,经85,100或115℃处理后,其抗原性显著降低,且随着温度和时间的增加其抗原性均不断降低.CD色谱分析表明,Ara h 2经热处理后其二级结构发生变化;ANS荧光探针光谱显示,不同的热处理均导致Ara h 2表面疏水性增加.紫外光谱显示,不同温度对Ara h 2处理30 min后(除55℃外),其紫外吸收值均升高.Ara h 2经100℃处理不同时间后,其紫外吸收值均有增加.由此推断,花生过敏原Ara h 2的构象改变导致了其抗原性的降低.     

基于光谱法舌诊的脂肪肝快速诊断

提出了一种基于光谱技术的脂肪肝无创、快速诊断新方法。由于舌体能较客观的反映人体生理、病理变化,因此采集志愿者舌体舌尖部位的反射光谱,然后对数据进行分析,计算反射光谱的归一化反射率。建立3层BP网络模型,从采集来的115例样本中抽取32例健康人和44例脂肪肝患者的光谱归一化反射率作为神经网络的输入,再对未知的14例健康人样本和25例脂肪肝患者样本进行分类预测,分类正确率达到89.7%,实验结果表明了光谱法运用于脂肪肝快速无创诊断的可行性。同时,实验结果说明光谱法能更客观全面地反映人舌所携带的组织细胞、微循环等方面的信息,有可能为临床提供一种快速、简便的诊断手段,也为今后的中医证侯的度量提供借鉴。     

X波段重复频率GW级超辐射相对论返波管

运用超辐射机理,通过粒子模拟设计了X波段超辐射相对论返波管,并在小型Tesla脉冲源平台上开展了实验研究。通过空间功率积分和直接对辐射微波时域波形的分析得到实验结果:在束压350 kV、束流4.8 kA、脉宽3.1 ns、引导磁场2.2 T条件下,产生的微波辐射功率1.4 GW,中心频率9.36 GHz,脉宽500~700 ps,辐射模式为TE11,能在重复频率100 Hz下稳定运行。功率转换效率超过80%。实验结果与粒子模拟结果比较吻合,成功实现了在短脉冲条件下产生重复频率、亚纳秒脉宽、GW级微波辐射。     

X波段相对论返波管谐振反射器

基于TPG2000强流电子束加速器和带谐振反射器的相对论返波管振荡器,开展了X波段高功率微波产生实验研究,获得了功率约2.5 GW,脉宽约20 ns的微波输出。理论分析及模拟了不同倒角大小对谐振反射器的表面电场及截止性能的影响,并对不同倒角开展了实验研究。结果表明,对谐振反射器倒角可增加输出微波脉冲宽度,且随着倒角增加,微波脉宽增加,效率略有降低。在谐振反射器倒角5 mm情况下,利用电压900 kV,电流9 kA的强流电子束,实验获得了功率约2.5 GW、脉宽大于25 ns的微波输出。     

A new model for electromigration grain boundary noise based on free volume

Grain boundary plays a key role in electromigration process of polycrystal interconnection. We take a free volume to represent a 'vacancy--ion complex' as a function of grain boundary specific resistivity, and develop a new characterisation model for grain boundary noise. This model reveals the internal relation between the boundary scattering section and electromigration noise. Comparing the simulation result with our experimental result, we find the source as well as the form of noise change in the electromigration process. In order to describe the noise enhancement at grain boundary quantitatively, we propose a new parameter-grain boundary noise enhancement factor, which reflects that the grain boundary noise can characterise the electromigration damage sensitively.     

基于无记忆状态观测器的多时滞不确定非线性系统的自适应控制

针对一类多时滞不确定非线性系统,研究了基于无记忆状态观测器的自适应控制问题.时滞状态扰动的上界未知,在控制中通过自适应律估计未知参数,并利用估计值设计了不依赖于时滞的无记忆状态观测器和控制器,基于Lyapunov-Krasovskii函数证明了观测误差渐近收敛到零.最后仿真结果说明了该方法的有效性.     

掺铒的纳米相氟氧化物玻璃陶瓷的多光子红外量子剪裁

研究了掺铒的纳米相氟氧化物玻璃陶瓷(Er(3):FOV)的红外量子剪裁现象,测量了红外和可见的Er(3):FOV的荧光光谱.结果发现光激发²H_11/2能级的⁴ I_13/2→⁴I_15/2荧光跃迁的近似量子剪裁效率已达约186.28%.计算了有关的无辐射弛豫速率、自发辐射速率和能量传递速率,分析了有关的能量传递动力学过程,发现