Time-Resolved Femtosecond Degenerate Four-Wave Mixing in LiNbO3：Fe,Mg Crystal

Forward degenerate four-wave mixing （DFWM） processes are investigated with a femtosecond pulsed laser in lithium niobate crystal doubly-doped with magnesium and iron （LiNbO3：Fe, Mg）. The pulse energy dependence reveals a pure third-order nonlinear response, and the third-order nonlinear susceptibility x^（3） in the material is evaluated to be 4.96 × 10^-13 esu. The time-resolved DFWM process shows a response time of x^（3） shorter than 100fs, which is due to the nonresonant electronic nonlinearities. Our results indicate that LiNbO3 crystals have potentials for ultrafast real-time optical processing systems, which require a large and fast x^（3） optical nonlinearity.     

反铁磁铜氧化合物中的磁致形状记忆

La2-xSrxCuO4(以下称LSCO)是最早发现的高温超导体之一.当x≈0.15时,它具有最高的超导转变温度,Tc=33K.对于x<0.02的轻度掺杂,材料的低温相是反铁磁绝缘体.在室温以上时,层状化合物LSCO晶格具有四方对称性;当冷却样品通过特征温度To,将发生从四方到正交的结构相变.此时,晶体发展出一种被称为孪晶的畴结构,被畴壁分开的相邻区域具有不同的晶轴取向.正交结构的晶格常数a=05339nm,b=0.5422nm,两者相差约1%.为了探求高温超导机理,LSCO曾被广泛深入地研究.由于在超导LSCO中根本不存在41meV反铁磁自…     

金属铀各相电子结构与原子力

锕系元素不仅存在σ，π，δ对称，还出现了φ轨道，而且相对论效应十分明显，作用机理比较复杂，而全电子计算由于对计算机硬件的要求十分苛刻，因而尚难以开展。因而国际上除了做了一些铀、钚化合物的物性研究外，几乎难以找到关于铀钚腐蚀机理的第一原理研究的报道。而用第一原理研究对于一些非镧、锕系元素，如硅、铜、钯等这种研究工作已经开展得很普遍，而且已经用于指导催化和腐蚀研究的实践工作。在LLUL钚科学在挑战专辑中，对于钚的基态性质，采用局域密度近似（简称LDA）和综合梯度近似方法简称GGA）进行了研究，     

Experimental and Theoretical Evidence for the Existence of Broad Forbidden Gaps in the Three—Component Composite

The influence of localized resonance on the properties of band-gaps of the two-dimensional periodic composite are analysed numerically and experimentally by comparing the two-component phononic crystal with the three-component one. The three-component composite which exhibits localized resonance in the elastically soft coating ring is composed of a square array of coated cylinders embedded in an epoxy resin. The coated cylinders consist of a steel inner core and a rubber coating, which has much smaller wave velocity and mass density than the matrixand tile inner material. Tile measured transmission power of tile three-component composite drops to the noise level in a broad ultrasonic frequency interval in contrast to the binary composite, which is in good agreement with the calculation using the finite element method.     

Y（Fe，Si）12化合物结构与磁性的第一原理计算

R（Fe，Si）12（R=Y，Nd）型稀土永磁材料具用重要的实际应用价值，然而对于V（Fe，Si）12化合物微观机理的理论计算工作至今尚未开展。采用新近发展的全势能线性缀加平面波（（L）APW）＋局域轨道（10）和广义梯度近似（GGA）密度泛函方法对其结构与磁性进行了研究。     

Time—Resolved Photoluminescence Studies of AlInGaN Alloys

We study the two samples of AlInGaN,i.e.,1-μm Gan grown at 1030℃ on the buffer and followed by a 0.6μm-thick epilayer of AlInGaN under the low pressure of 76 Torr and the AlInGaN layer deposited diectly on the buffer layer without the high-temperature GaN layer,by temperature-dependent photoluminescence(PL) spectroscopy and picosecond time-resolved photoluminescence(TRPL) spectroscopy.The TRPL signals of both the samples were fitted well as a stretched exponential decay at all temperatures,indicating significant disorder in the material.We attribute the disorder to nanoscale quantum dots or discs of high indium concentration.Temperature dependence of dispersive exponent β shows that the stretched exponential decay of the two samples comes from dfferent mechanisms.The different depths of the localization potential account for the difference,which is illustrated by the results of temperature dependence of radiative recombination lifetime and PL peak energy.     

二代树状碳硅烷液晶研究Ⅰ.端基含36个丁氧基偶氮苯介晶基元

用发散法合成周边含36个丁氧基偶氮苯介晶基元(M5)端基新的二代树状碳硅烷液晶(D2),并用元素分析,氢谱,激光质谱,红外,紫外,偏光显微镜,DSC和WAXD法表征.D2为向列相,与M5相同,二代树状物相态由介晶基元相态决定.D2液晶态相行为是K85N107I103N69K,其熔点比M5降低27～41℃,清亮点比M5降低17～18℃,液晶态温区比M5加宽10～23℃.二代碳硅烷(D2)与一代碳硅烷(D1)相比熔点增加2～3℃,清亮点降低26～29℃,液晶态温区减少29～31℃.在二代树状物中观察到S=+3/2的高强向错.     

固定化单宁对酒类营养成分的吸附性能研究

采用固定化单宁对酒中可能存在的营养成分蛋白质、氨基酸、糖类、有机酸、乙醇和铁离子等进行吸咐试验。结果表明：固定化单宁对不同营养成分的吸附率差别明显，它通过氢键和疏水作用对蛋白质有较大的吸附率，通过多个酚羟基与中心铁离子形成螯合物而对其有较大的吸附率，对氨基酸、糖、有机酸和乙醇等营养成分或风味物质吸附率不大，固定化单宁可以作为一种较为理想的酒类处理剂。     

3-(1-氢多氟烯基)-1-氧代-2，4，1-苯并噁嗪与双亲核试剂反应合成含氟杂环化合物

本文研究了3-(1-氢多氟烯基)-1-氧代-2，4，1-苯并噁嗪1与几种双亲核试剂的反应。化合物1与乙二胺反应生成7-氟烷基-1，4-二氮杂卓[1，2-d]喹唑啉-11-酮；在吡啶溶剂中与盐酸羟胺反应得到了2-氟烷基异噁唑[3,2-b]并喹唑啉-9-酮；与邻苯二胺反应得到2-氟烷基苯并咪唑类化合物。