印楝素微波萃取技术研究

印楝素(Azadirachtin)是从印楝(Azadirachta indica A.Juss)种仁中分离得到的柠檬素类(limonoids)化合物,属四环三萜类化合物[1].生物活性试验证明低浓度的印楝素即对沙漠蝗(Schistocera gregaria)产生强烈的拒食活性,进一步的研究证明印楝素对多种农林业害虫具有较高的拒食、趋避及抑制生长发育等作用[2],且具有害虫不易产生抗性、对温血动物无害、对昆虫的天敌较安全、在自然界易降解等特点,其广泛应用有利于生态平衡及农林业的可持续发展,是一种有广阔应用前景的植物源生物农药.     

Knockout reaction induced by ~6 He at 61.2 MeV/u

A knockout reaction induced by ⁶He at 61.2 MeV/u was carried out at the HIRFL-RIBLL radioactive beam line. The α core fragments at forward angles were detected in coincidence with the recoiled protons at large angles. From this coincident measurement the valence nucleon knockout mechanism and the core knockout mechanism can be separated according to the polar angle correlation between the core fragments and the recoiled protons. It is demonstrated that, when reconstructing the resonant state of a weakly bound nucleus, the contamination resulting from the core knockout mechanism should be eliminated in order to obtain the correct structure information.     

手性咪唑酯类离子液体的合成及其物理性能

以咪唑,溴代烷烃及(-)-薄荷醇为原料合成了12个手性咪唑酯类离子液体,其结构经NMR和IR表征.物理性能研究结果表明,该类离子液体具有较好的热稳定性,且比旋光度存在一定的改变规律.     

(-)-龙脑手性离子液体的合成

以(-)-龙脑为手性源,与溴乙酰溴通过酯化反应合成溴代乙酸龙脑酯(2);2与4,4'-联吡啶发生取代反应引入两个手性中心制得新型手性离子液体——N,N'-双(龙脑氧甲酰亚甲基)联吡啶.二溴(3.2Br-);3.2Br-与四氟硼酸钾或六氟磷酸钾盐进行阴离子交换制得相应的手性离子液体3.2BF4-或3.PF6-.3.2Br...     

双端输出外腔谐振倍频的运转特性研究

准相位匹配晶体外腔谐振倍频是获得高效率短波长激光稳定输出的技术之一.为消除高功率激光抽运时非线性级联过程的影响、提高倍频激光的输出功率,本文设计了一种双端输出倍频谐振腔.首先在实验上比较了双端和单端输出谐振倍频过程的倍频效率和输出功率;并在理论上分析了双端腔型下基频光与倍频光相对相位的变化对于倍频输出光功率的影响,通过控制相对相位可以获得高的倍频光输出功率.实验结果与理论分析基本吻合.     

基于光学参量振荡器的可调谐红外激光的强度噪声特性

红外激光光源在微量气体、高分辨率光谱分析和量子光学研究等领域具有重要的应用.本文利用锁定单共振光学参量振荡器内腔标准具的方案获得了无跳模连续调谐的红外激光输出,理论和实验研究了红外激光的强度噪声特性,分析了影响强度噪声的因素.通过控制非线性晶体的温度和标准具调制信号实现了对红外激光强度噪声的抑制.当控制非线性晶体工作温度为60℃,内腔标准具调制信号为8 kHz时,单共振光学参量振荡器输出信号光和闲置光的强度噪声分别降低了11和8 dB.     

高取向度石墨基复合材料力学性能及微观结构研究

以ZrB2和SiC为烧结助剂,采用流延-叠层-热压工艺制备高取向石墨基复合材料,并对其抗弯强度、断裂韧性、断裂行为以及微观结构进行了研究.结果表明:该石墨基复合材料结构完整,其中片状石墨颗粒平行热压面高度定向排列.弯曲强度和断裂性能及致密度都得到大幅度提高,垂直片层和平行片层方向测试的抗弯强度和断裂韧性分别为104 MPa、2.07 MPa·m1/2和84 MPa、1.97 MPa·m”2.高取向石墨基复合材料受到不同方向力冲击时的断裂行为显著不同,垂直层面加压时断裂由脆性破坏变为非脆性破坏行为,断裂功达到145 J/m2为平行层面测试的2倍.非脆性破坏行为主要归因于层界和高度定向的片状石墨颗粒诱导裂纹偏转分叉以及片状石墨颗粒桥联拔出.     

Low noise, continuous-wave single-frequency 1.5-μm laser generated by a singly resonant optical parametric oscillator

We report a low noise continuous-wave (CW) single-frequency 1.5-μm laser source obtained by a singly resonant optical parametric oscillator (SRO) based on periodically poled lithium niobate (PPLN). The SRO was pumped by a CW single-frequency Nd:YVO₄ laser at 1.06 μm. The 1.02 W of CW single-frequency signal laser at 1.5 μm was obtained at pump power of 6 W. At the output power of around 0.75 W, the power stability was better than ±1.5% and no mode-hopping was observed in 30 min and frequency stability was better than 8.5 MHz in 1 min. The signal wavelength could be tuned from 1.57 to 1.59 μm by varying the PPLN temperature. The 1.5-μm laser exhibits low noise characteristics, the intensity noise of the laser reaches the shot noise limit (SNL) at an analysis frequency of 4 MHz and the phase noise is less than 1 dB above the SNL at analysis frequencies above 10 MHz.     

Continuous-wave, single-frequency intracavity singly resonant optical parametric oscillator at 1.5-μm wavelength

We present a 1.5μm continuous-wave （CW） single-frequency intracavity singly resonant optical parametric oscillator （SRO） based on periodically poled lithium niobate （PPLN）. The SRO is placed inside the ring cavity of a single-frequency 1.06μm Nd：YVO4 laser pumped by a laser diode. The device delivers a maximum single-frequency output power of 310 mW at a resonant signal wavelength of 1.57 μm. The signal wave could be tuned from 1.57 to 1.59 μm by temperature tuning of PPLN crystal over the range of 130 - 170℃.     

变分迭代法在抛物型方程反问题中的应用

本文将改进的变分迭代法的应用范围加以推广,使其应用于多维抛物型方程反问题中。它通过Lagrange乘子进行简便计算求得未知参量的精确值,再应用于多维抛物型方程反问题可以快速得到收敛于反问题精确解的收敛序列,从而得到精确解。同时,通过与Adomian’s分裂法结果比较可知前者比分裂法好。