利用反射太赫兹时域强度分布定量检测沙粒中的微量原油

原油污染是海洋生物和环境安全的主要威胁之一,检测近海沙粒中的微量原油对于环境保护和原油勘探有着重要意义.本文采用反射式太赫兹时域波形对近海沙粒中的原油进行定量检测,详细地分析了延迟时间与沙粒中的原油浓度的关系.结果表明,原油浓度与延迟时间呈线性递减关系,反射式太赫兹时域波形是一种具有潜力的污染定量检测方法.     

多金核二氧化铈空心球用于硝基苯酚催化加氢

催化剂的微观结构在催化还原反应、有机物氧化反应及有机物转化反应中起着关键作用。本文利用无模板方法合成了多金核中空二氧化铈微球催化剂。将制备好的二氧化铈中空微球浸渍到一定浓度的氯金酸溶液中,然后多次洗涤除去表面吸附的氯金酸离子,最后通过硼氢化钠还原制成中空氧化铈微球包覆的多金核的核壳结构催化剂。将该核壳结构材料用于硝基苯酚加氢反应与金纳米粒子及氧化铈微球相比,多金核中空二氧化铈核壳结构表现出优越的活性和稳定性。通过这种浸渍洗涤再还原的简单方法合成的多金核二氧化铈催化剂有望应用于生物医药和能源环境等领域。     

Attosecond laser station

The attosecond laser station(ALS) at the Synergetic Extreme Condition User Facility(SECUF) is a sophisticated and user-friendly platform for the investigation of the electron dynamics in atoms, molecules, and condensed matter on timescales ranging from tens of femtoseconds to tens of attoseconds. Short and tunable coherent extreme-ultraviolet(XUV)light sources based on high-order harmonic generation in atomic gases are being developed to drive a variety of endstations for inspecting and controlling ultrafast electron dynamics in real time. The combination of such light sources and end-stations offers a route to investigate fundamental physical processes in atoms, molecules, and condensed matter. The ALS consists of four beamlines, each containing a light source designed specifically for application experiments that will be performed in its own end-station. The first beamline will produce broadband XUV light for attosecond photoelectron spectroscopy and attosecond transient absorption spectroscopy. It is also capable of performing attosecond streaking to characterize isolated attosecond pulses and will allow studies on the electron dynamics in atoms, moleculars, and condensed matter. The second XUV beamline will produce narrowband femtosecond XUV pulses for time-resolved and angle-resolved photoelectron spectroscopy, to study the electronic dynamics on the timescale of fundamental correlations and interactions in solids, especially in superconductors and topological insulators. The third beamline will produce broadband XUV pulses for attosecond coincidence spectroscopy in a cold-target recoil-ion momentum spectrometer, to study the ultrafast dynamics and reactions in atomic and molecular systems. The last beamline produces broadband attosecond XUV pulses designed for time-resolved photoemission electron microscopy, to study the ultrafast dynamics of plasmons in nanostructures and the surfaces of solid materials with high temporal and spatial resolutions simultaneously. The main object of the ALS is to provide domestic and international scientists with unique tools to study fundamental processes in physics, chemistry,biology, and material sciences with ultrafast temporal resolutions on the atomic scale.     

Consistency-dependent optical properties of lubricating grease studied by terahertz spectroscopy

The optical properties of four kinds of lubricating greases (urea, lithium, extreme pressure lithium, molybdenum disulfide lithium greases) with different NLGL (National Lubricant Grease Institute of America) numbers were investigated using terahertz time-domain spectroscopy. Greases with different NLGL grades have unique spectral features in the terahertz range. Comparison of the experimental data with predictions based on Lorentz--Lorenz theory exhibited that the refractive indices of each kind of lubricating grease were dependent on the their consistency. In addition, molybdenum disulfide (MoS₂) as a libricant additive shows strong absorption from 0.2 to 1.4 THz, leading to higher absorption of MoS₂-lithium grease than that of lithium grease.     

Diffusion interaction and quantitative analysis of zinc dialkyldithiophosphate content in lube base oils in terahertz regime

We investigate the diffusion interaction and quantitative analysis of zinc dialkyldithiophosphate (ZDDP) mixed with lube base oil (LBO) at different concentrations using terahertz time-domain spectroscopy (THzTDS).When the concentration exceeds 6.78%,the characteristic absorption peaks exhibit significantly shift,and the absorption coefficient peak value is nonlinear against concentration.Moreover,the absorption coefficients of mixed samples follow the Beer’s law at a concentration below 6.78%.The quantitative analysis enables a strategy for monitoring the formulation of lubricating oil in real time.     

用于长城等古建筑探测的NMR探测器的磁体设计

以万里长城为代表的古建筑是世界瑰宝,更是中华民族的象征和骄傲.本文提出利用便携式核磁共振(NMR)装置来探测研究这类古建筑的建筑材料,在不对其造成损伤的基础上,发掘其隐含的科学、技术和工程相关的丰富信息.为此,作为第一步,设计了适合于探测这类古建筑的便携式单边NMR探测器组合式磁体.该探测器的磁体结构以semi-Halbach为基础,通过不同磁体模块间的组合得到对应移动探测模式、长距离探测模式和均匀磁场探测模式的磁体结构.随后根据优化结果,设计加工了磁体组件,并采用该磁体进行了流体、长城城砖和现代红砖的NMR实验,实测结果与模拟一致.该组合式磁体的优点在于通过不同磁体模块组合,实现了多种探测方式,适用于探测长城等这类古建筑物需要多种探测模式的科学研究.     

半导体量子点中极化子的跃迁能量

研究了半导体量子点中极化子的激发态性质。采用Huybrechts线性组合算符和幺正变换方法,计算了量子点中极化子的振动频率、基态能量、第一激发态能量、由第一激发态向基态的跃迁能量和跃迁频率。分别讨论了电子-LO声子在强弱两种耦合情况下极化子的跃迁能量和跃迁频率。数值计算结果表明,跃迁能量ΔE和跃迁频率ω均随量子点有效受限长度l₀的增加而减少,且随电子-声子耦合强度α的增加而减少。     

Fast lateral photovoltaic effect in ferroelectric LiNbO_3 single crystals

We report the fast lateral photovoltaic effect in pure congruent LiNbO3 crystal induced by pulsed laser and continuous wave laser with wavelengths of 355, 532, and 1064 nm. A typical ultrafast photovoltage can be observed on the surface perpendicular to the c axis, With the rise time of 1.5 ns and the full-width at half-maximum of 1-2 ns, when the laser pulse inhomogeneously irradiates on the crystal. The peak open-circuit photovoltages show a linear dependence on the incident laser intensities. The mechanism of the photovoltaic characteristics is proposed.     

加权p-Laplace方程解的整体分叉问题

该文利用指标理论，谱理论以及标准分叉定理，研究了加权索伯列夫空间中的p Laplace方程初值问题的解的整体分叉现象。     

Enhancement of isolated attosecond pulse generation by using long gas medium

Isolated attosecond pulse generation in argon is theoretically investigated for different gas pressures and medium lengths. The output of attosecond pulse is effectively enhanced by using a longer gas medium with optimized pressure. The peak intensity of the attosecond pulse by using 6 mm gas medium is doubled compared with that of 1-3 mm gas cell, which is usually used in the experiment. Our simulation shows that the distortion of the driving laser waveform and the absorption are the main factors that limit the output of the attosecond pulse for the long gas medium. Optimized generation condition could be found by balancing the medium length and pressure.