孕震断层锁固段累积损伤导致失稳的自组织-临界行为特征

弄清锁固段（岩石）破裂过程中自组织临界性的物理涵义,对正确认识地震可预测性问题等具有重要意义.本文指出锁固段破裂过程存在两个临界点,第一临界点为体积膨胀点,是自组织过程起点,在该点锁固段发生可判识的高能级破裂事件,这可视为锁固段宏观破裂前的惟一可识别前兆;第二临界点为峰值强度点,即失稳点,在该点通常发生有明显地表破裂带的大地震.基于以前研究给出的两者之间应变比理论关系以及地震震级与能量约束关系,可预测锁固段在第一和第二临界点处发生的某些标志性地震,并已得到诸多震例分析的支持.本文研究结果表明：由于锁固段是非均匀介质,失稳前必须出现自组织过程,自组织是“因”,临界失稳是“果”,正是因为自组织过程的存在,才使得对某些大地震（如标志性地震）的预测成为可能;两个临界点之间的破裂演化过程并不是瞬态行为,通常是一个长期过程,该过程中标志性地震的发生遵循确定性规律,并不存在小地震直接导致大地震（如标志性地震）的级联效应.     

Mid-infrared carbon dioxide sensor with wireless and anti-condensation capability for use in greenhouses

A mid-infrared carbon dioxide sensor with wireless and anti-condensation capability was experimentally demonstrated for greenhouse application. The sensor included an optical module integrated in a multi-pass gas chamber using the dual-channel detection method to suppress environmental noise. Considering the condensation phenomenon in the greenhouse, the optical chamber was protected with a breathable waterproof coverage. The field test demonstrated that the internal optical framework was kept in stable relative humidity, ensuring the sensor’s applicability in the greenhouse. For wireless communication, received signal strength indication was used to ensure the reliability of link quality and enable smart power regulation. In related experiments, there was a satisfying performance in terms of stability and error detection within the measurement range of 30???5000?ppm. Without increasing the integral time, the limit of detection of the sensor was at least 30?ppm, which was acceptable for greenhouse application. A field test was carried out in Town Shelin of Jilin Province, China and the test showed the proposed sensor had relatively good prospect for application in fine agriculture.     

铒镱共掺磷酸镧纳晶的合成和近红外荧光性质

以磷酸三丁酯作为配体,使用高温溶液法合成了掺铒磷酸镧纳米晶体,高分辨电镜和XRD结果表明产物尺寸均一,直径4nm左右,具有高度的结晶性,在甲苯等有机溶剂中分散性良好.近红外发光光谱表明,产物在1535 nm处有发光峰,半高全宽为50 nm,高于目前掺铒光纤放大器(EDFA)的增益带宽.通过IR、元素分析研究发现,使用真空干燥等方法不能有效去除纳晶表面的羟基.为了进一步消除表面缺陷和猝灭基团对纳晶发光性质的影响,我们尝试在其外围生长一层LaPO₄壳做成核壳粒子以消除表面缺陷和隔离猝灭基团,结果表明,新的纳晶的发光强度得到了显著提高.     

有机红外半导体酞菁铒的掺杂及电学性质研究

对固相合成法制备的有机红外半导体ErPc₂进行了碘掺杂,有效地将ErPc₂的电阻率降低了约3个数量级.研究了本征和碘掺杂有机红外半导体ErPc₂电阻的温度依赖关系,碘的掺杂除显著地降低了ErPc₂材料的电阻外,其电阻的温度特性没有本质的变化,本征和碘掺杂ErPc₂都表现出指数型的电阻温度依赖关系.碘掺杂有效地降低了载流子的热激活能,使更多的载流子得以参与导电,掺杂后指前因子的减小也为降低材料的电阻 关键词： 有机红外半导体 酞菁铒 掺杂 电学性质     

NMR Relaxivities of Paramagnetic Lanthanide-Containing Polyoxometalates

The current trend for ultra-high-field magnetic resonance imaging (MRI) technologies opens up new routes in clinical diagnostic imaging as well as in material imaging applications. MRI selectivity is further improved by using contrast agents (CAs), which enhance the image contrast and improve specificity by the paramagnetic relaxation enhancement (PRE) mechanism. Generally, the efficacy of a CA at a given magnetic field is measured by its longitudinal and transverse relaxivities r₁ and r₂, i.e., the longitudinal and transverse relaxation rates T₁⁻¹ and T₂⁻¹ normalized to CA concentration. However, even though basic NMR sensitivity and resolution become better in stronger fields, r₁ of classic CA generally decreases, which often causes a reduction of the image contrast. In this regard, there is a growing interest in the development of new contrast agents that would be suitable to work at higher magnetic fields. One of the strategies to increase imaging contrast at high magnetic field is to inspect other paramagnetic ions than the commonly used Gd(III)-based CAs. For lanthanides, the magnetic moment can be higher than that of the isotropic Gd(III) ion. In addition, the symmetry of electronic ground state influences the PRE properties of a compound apart from diverse correlation times. In this work, PRE of water ¹H has been investigated over a wide range of magnetic fields for aqueous solutions of the lanthanide containing polyoxometalates [Dy^III(H₂O)₄GeW₁₁O₃₉]^5– (Dy-W₁₁), [Er^III(H₂O)₃GeW₁₁O₃₉]^5– (Er-W₁₁) and [{Er^III(H₂O)(CH₃COO)(P₂W₁₇O₆₁)}₂]¹⁶⁻ (Er₂-W₃₄) over a wide range of frequencies from 20 MHz to 1.4 GHz. Their relaxivities r₁ and r₂ increase with increasing applied fields. These results indicate that the three chosen POM systems are potential candidates for contrast agents, especially at high magnetic fields.     

光阴极注入器的驱动激光器

 光阴极注入器要求驱动激光器的激光时间抖动小、脉冲宽度窄、激光波长短和脉冲功率高。从原理和实验上介绍光阴极注入器的驱动激光器,包括连续波锁模振荡腔、时间同步,激光脉冲功率放大等;该激光器输出激光微脉冲宽度10ps,微脉冲时间抖动小于2ps,宏脉冲宽度2.5 μs, 峰值功率100kW, 已用于光阴极RF腔注入器实验,并获得了很好的结果。     

二(2,4,4-三甲基戊基)膦酸在中空纤维膜器中萃取镱、铒及传质研究

中空纤维膜萃取技术是将液液萃取过程与膜过程相结合的新型分离技术．二（２,４,４三甲基戊基）膦酸（ＨＢＴＭＰＰ,ＨＬ）萃取稀土及其它高价金属离子时所需水相酸度低,反萃容易,加之空间位阻等因素,很可能成为优于２乙基己基膦酸单２乙基己基酯（ＨＥＨ／...     

Cr,Ca：YAG晶体中四价Cr^4＋中心的晶场特性

综合分析了铬钙离子共掺钇铝石榴石晶体可见光－近红外区的室温吸收光谱,其中四配位和六配位的四价Ｃｒ＾２＋离子光谱成分是共存的,拟合得到的晶场参数符合光谱学的理论和实验规律,并且这两类Ｃｒ＾４＋中心的晶声性质均受到晶体中二价补偿离子Ｃａ＾２＋的影响。     

Phase variation experiments in non-contact dynamic force microscopy using phase locked loop techniques

This work presents constant amplitude Dynamic Force Microscopy (DFM) measurements under ultra-high vacuum conditions performed with home-built digital electronics based on the principle of phase locked loop (PLL) techniques. In DFM so-called topography is often measured in constant frequency shift (Δf) mode. This study describes the influence of phase shifts on constant Δf imaging. Therefore, phase variation experiments were acquired, leading to information about the cantilever resonance behaviour close to the surface. As sample, an evaporated thin film of NaCl on a Cu(111) substrate was chosen in order to obtain a heterogeneous system with clean Cu and NaCl areas. The atomic structure of both materials was resolved, which is the first time true atomic resolution was obtained on a metal. Large apparent topography variations are observed on this heterogeneous sample when changing the phase between the excitation and oscillation of the cantilever end. Such artefacts can be explained by comparison with phase variation experiments.     

Optical Signal Inversion Phenomenon for 1.5 μm Derived from the Negative Nonlinear Absorption Effect in an Erbium Nitrate Solution

The modulation characteristics of the negative nonlinear absorption effect were investigated in an erbium nitrate solution using a 1510 nm laser diode. The reversed-phase waveform was obtained in the transmitted laser for a sample length of 3.0 mm. With decrease in the modulation degree, the reversed-phase waveforms were observed at modulation degrees smaller than 72%. With increase in the modulation frequency, the transmitted waveforms were asymmetrical. The optical signal inversion phenomenon for 1.5μm can be explained by considering an excited state absorption in which energy transfer occurs in a system with high concentrations of the Er3+ ion.