Magnetic alignment in nominally non-magnetic hexagonal metal hydrides: NMR

Powders of three hexagonal metal-hydrides or -deuterides are found to align in 4.4–8.3 T magnetic fields used for NMR. The field-alignment is unexpected, since all three systems have very small susceptibilities, as demonstrated by sharp NMR lines. The extent of alignment runs from nearly complete to barely detectable in ZrBe₂(H,D)_x, LuD₃, and YD₃, respectively. The preferred alignment direction in ZrBe₂(H,D)_x is with the crystallites’ c-axis perpendicular to B, while the c-axis and B tend to be parallel in LuD₃ and YD₃. The susceptibilities χ_|| and χ are determined from bulk magnetization measurements in aligned ZrBe₂H_1.4 powder. The alignment must be considered for proper analysis of NMR spectra in these and related materials.     

Global solutions to the damped MHD system

The global existence of solutions to a damped MHD system in Besov spaces is obtained. This research is motivated by the open question [Wu et al., J. Nonlinear Sci. 25 (2015), 157–192, Remark 5.1] on the possibility of extension to the existence of global small solutions from a potential Banach space to a Besov space. The present result positively confirms the open question. What is more, the initial data are not required to be uniformly small.     

Quantum Dialogue with Authentication Based on Bell States

We propose an authenticated quantum dialogue protocol, which is based on a shared private quantum entangled channel. In this protocol, the EPR pairs are randomly prepared in one of the four Bell states for communication. By performing four Pauli operations on the shared EPR pairs to encode their shared authentication key and secret message, two legitimate users can implement mutual identity authentication and quantum dialogue without the help from the third party authenticator. Furthermore, due to the EPR pairs which are used for secure communication are utilized to implement authentication and the whole authentication process is included in the direct secure communication process, it does not require additional particles to realize authentication in this protocol. The updated authentication key provides the counterparts with a new authentication key for the next authentication and direct communication. Compared with other secure communication with authentication protocols, this one is more secure and efficient owing to the combination of authentication and direct communication. Security analysis shows that it is secure against the eavesdropping attack, the impersonation attack and the man-in-the-middle (MITM) attack.     

动态冷原子吸收法快速测定地球化学样品中微量汞

本文介绍了动态冷原子吸收法快速测定地球化学样品中微量汞的方法。本文研究采用了新型的汞蒸气发生器，并对气泡的干扰进行了研究。线性范围为0.2-12ng/mL，标准回收率为97％－106％，相对标准偏差为3.6%，相关系数为0.9997，试验结果表明此方法简便、快速、准确。     

卫星激光通信发展现状与趋势分析(特邀)

卫星激光通信凭借其宽带宽以及无电磁频谱约束等特点,成为解决卫星微波通信带宽瓶颈和缓减卫星频谱资源紧张,实现卫星高速通信的有效手段。本文介绍了卫星激光通信的系统组成及特点,分析了国内外卫星激光通信技术领域的发展脉络、最新研究进展和未来发展规划。结合未来空间网络与深空探测需求,从高速化、深空化、集成化、网络化、全光化五个方面总结了未来发展趋势,并对未来涉及的关键技术进行了讨论,为我国卫星激光通信技术研究提供借鉴和参考。     

Nondestructive testing by ESPI and quasi phase shift gradient technique

A new nondestructive testing (NDT) technique, which is based on Electronic Speckle Pattern Interferometry (ESPI) and digital image processing with quasi phase shift and gradient technique, is presented. A simple phase reduction algorithm is developed, which replaced an accurate phase shifter. Compared with other phase shift techniques, this method is insensitive to environmental vibration and air disturbance, has visible procedures and results allows the object to move slowly during the inspection procedure, does not need phase unwrapping, and has a quick image processing speed. As an application, this NDT technique is used to detect defects in composite materials and the resulting deformation phase gradient image shows a better visual effect than normal ESPI.     

FDTD Method in the Analysis of Lithium Niobate Modulator

The Mach-Zehnder traveling-wave lithium niobate modulator is simulated by time domain finite difference (FDTD)method for different device geometry. The result is comparable to the reported value by finite element method.     

增强UV-B辐射、NaCl胁迫及其复合处理对小麦幼苗光合作用及黄酮代谢的影响

依据增强UV-B辐射、NaCl胁迫及其复合处理不同天数，分别测定各处理小麦幼苗第一片真叶的净光合速率、气孔导度、叶肉细胞间隙二氧化碳浓度、叶绿素含量、黄酮含量和苯丙氨酸裂解酶活性.发现NaCl胁迫和增强UV-B辐射均明显降低小麦幼苗的净光合速率、气孔导度和叶肉细胞间隙CO2浓度;和NaCl胁迫相较， NaCl+UV-B辐射对小麦幼苗上述指标无进一步降低效应.增强UV-B辐射、NaCl胁迫及其复合处理均促进苯丙氨酸裂解酶活性和黄酮含量提高.说明了增强UV-B辐射降低小麦幼苗净光合速率的主要原因是气孔限制，而NaCl胁迫减轻了增强UV-B辐射对小麦幼苗光合作用的降低效应.     

双脉冲高功率脉冲调制器的设计

采用螺旋线和折叠线技术相结合的方法,设计了一种基于水介质高功率脉冲调制器。该调制器采用了两个开关,通过控制两个开关的导通时刻,可以在两个负载上得到脉冲长度相等的两个脉冲。对该种折叠型传输线的波过程进行了详细分析,给出了过渡段部分阻抗等参数对负载电压的影响;用Pspice电路软件对脉冲形成线的充电电压和二极管电压、电流进行了模拟;最后利用高压同轴电缆,对该种类型调制器进行了低压情况下的验证实验,实验结果与理论分析、模拟研究一致。此种类型的调制器具有结构紧凑、可同时输出两个脉冲的优点。     

Synthesis, structure analysis and cytotoxicity studies of novel unsymmetrically n,n'-substituted ureas from dehydroabietic Acid

A series of novel unsymmetrically N,N'-substituted ureas were synthesized from dehydroabietic acid and their structures were characterized by IR, 1H-NMR, 13C-NMR spectroscopy and single crystal X-ray diffraction. Three six-membered rings of urea 4c exhibited plane, half-chair and chair configurations, respectively. Their cytotoxicity activities against SMMC7721 liver cancer cells were evaluated by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) method. The results showed that the title compounds exhibited highly effective cytotoxicity activities against SMMC7721 cells. Their IC50 values are between 8.8 and 14.2 micromol/l. The change of N' substituted groups resulted little difference to the cytotoxicity activities of ureas, which indicated that the cytotoxicity of this kind of ureas depend strongly on the tricyclic hydrophenanthrene structure.