Graphene-based passively Q-switched Nd:KLu(WO4)2 eye-safe laser operating at 1,425 nm

With graphene as saturable absorber, an Nd:KLu(WO₄)₂ eye-safe laser operating at 1,425 nm is demonstrated. To the best of our knowledge, this is the first demonstration that an Nd:KLu(WO₄)₂ laser operates at the eye-safe 1.4-μm region. A maximum total average output power of 170 mW is obtained under the pump power of 9.6 W, corresponding to an optical–optical efficiency of 1.77 %. The minimum pulse width and the highest pulse repetition rate are 153 ns and 97 kHz, respectively. Also the characteristics of the graphene used as saturable absorber for a 1.4-μm laser were studied for the first time.     

重金属铅离子胁迫下玉米叶片光谱弱差信息的DSAT甄别模型

光谱间微弱信息测度是当今高光谱遥感研究难点之一,传统光谱测度方法难以区分光谱信息的微弱差异。研究设计了不同浓度的铅(Pb)污染实验,并测量了不同浓度铅离子(Pb2+)胁迫下玉米叶片的高光谱反射率、叶绿素含量及Pb2+含量,但是从所测结果得出,不同浓度Pb2+胁迫下的光谱相似性相关系数均达到0.999,难以区分不同浓度Pb2+胁迫引发的光谱间微弱信息差异和污染程度。针对这一情况,基于光谱微分处理、正切函数增强、光谱角量度与波谱分段检测等,提出了一种新型的相似光谱测度方法,即微分光谱角正切(derivative spectral angle tangent,DSAT)法。为了验证DSAT在区分相关系数达0.99以上相似光谱的可行性和有效性,将DSAT用于不同浓度Pb2+胁迫玉米叶片的整体波形与光谱区间子波形的信息差异性度量与检测。实验结果得到,波形差异信息与玉米叶片中叶绿素相对浓度与Pb2+含量显著相关。进而也证明DSAT法在甄别较高相似性光谱间差异上具有更好的实用性和优越性。     

PECVDSiON薄膜的工艺控制,性质及其潜在应用

研究了等离子增强化学气相淀积氮氧化硅薄膜的工艺控制、性质以及薄膜波导在超大规模集成电路光互连中的潜在应用。     

酶催化动力学光度法测定抗坏血酸

基于抗坏血酸对血红蛋白模拟酶催化体系的抑制作用,建立酶催化动力学光度法测定抗坏血酸的新方法。研究了体系的最佳条件及动力学行为,测定的线性范围为2.0×10-7—5.9×10-5mol/L,方法检出限为7.0×10-8mol/L。对6.0×10-6mol/L的抗坏血酸进行11次平行测定相对标准偏差为2.5%。此方法可用于药剂和蔬菜中抗坏血酸含量的测定。     

Comparative Study of Tribological Properties of Polyphenylene Sulfide (PPS), Polyethersulfone (PES), and Polysulfone (PSU)

The tribological properties of polyphenylene sulfide (PPS), polyethersulfone (PES) and polysulfone (PSU), which have similar molecular structures, were investigated using an end-face contact tribometer and a reciprocating tribometer. The thermomechanical behavior of the polymers was analyzed using dynamic mechanical analysis (DMA). PPS exhibited a maximum friction coefficient with increasing load and sliding speed, while the friction coefficients of PES and PSU decreased only slightly. The wear rate of PPS was much lower than that of PES and PSU under high loads and speeds. It is suggested that the main factors influencing the friction and wear properties of the neat polymers are their condensed state and heat resistance. Amorphous PES and PSU showed liquid-like behavior and very low friction when the frictional surface was in the molten-flow state. The macromolecular crystals of crystallizable PPS give it some solid-like behavior and load-carrying capacity; hence PPS exhibited lower wear than PES and PSU.     

微波消解-原子吸收光谱法测定桑叶中微量元素

用微波消解及火焰原子吸收法测定5月,6月,8月,9月及10月等5个时期的桑叶中Fe,Mn,Cu,Zn,Ca 5种元素的含量,同时做精密度和加标回收试验,并对其含量进行比较,以期为临床,药物及食用含量研究开发利用提供参考.测定结果表明,各元素总体含量Ca>Fe>Mn>Zn>Cu,不同时期桑叶中微量元素各不相同,9月的桑叶中,各元素的含量均较高.     

Thermal Performance of Laser Diode Array under Constant Convective Heat Transfer Boundary Condition

Three-dimensional heat transfer model of laser diode array under constant convective heat transfer coefficient boundary condition is established and analytical temperature profiles within its heat sink are obtained by separation of variables. The influences on thermal resistance and maximum temperature variation among emitters from heat sink structure parameters and convective heat transfer coefficient are brought forward. The derived formula enables the thermal optimization of laser diode array.     

Anisotropic phononic crystal structure with low-frequency bandgap and heat flux manipulation

This study presents a two-dimensional phononic crystal with heat flux manipulation and wide bandgaps of out-of-plane modes within the low-frequency range. The anisotropic matrix made of spiral-multilayered materials with different thermal conductivities, and the coating layer inserted with metal are designed for heat flux manipulation. Rubber-coated metal cylinders are periodically embedded in the anisotropic matrix to obtain the low-frequency bandgaps of out-of-plane modes. Numerical simulation is carried out to validate the heat and elastic characteristics of the spiral-multilayered anisotropic structure and reveal the effects of the laying angle and temperature on the bandgaps. Subsequently, a spiral-multilayered plate with periodic structures is studied, which shows an obvious vibration attenuation in the frequency ranges of the bandgaps and a deflected heat flux from the initial propagation direction. In the experimental investigation, the multi-phase spiral-multilayered anisotropic plate is simplified to a single-phase anisotropic plate made of aluminum. The characteristics of this type of anisotropic phononic crystal structure may pave the way for the design of a new kind of thermo-acoustic metamaterial serving in combined thermal and acoustic environments.     

在第23届全国中学生物理竞赛决赛颁奖大会上的发言

今年（2006年）6月我国科技界开了一次重要的会议，就是中国科学院第13次院士大会和中国工程院第8次院士大会，这次两院院士大会特别强调了创新型人才的需要和培养创新型人才的重要性．在这次大会上，胡锦涛主席发表了重要讲话，讲到三个问题，一是目前的形势和我国科技战线的任务；二是建设宏大的创新型科技人才队伍；三是两院院士要在建设创新型国家中大显身手．在第二个问题中，他讲到创新型人才的重要性，特别提到“千军易得，一将难求”，并归纳了这种领军人才的素质和特点．这些，应该是同学们的努力方向，希望同学们去认真学习．     

An Exotic Phase Change in Dynamic Electrorheological Fluids

It is well known that constant or time-varying electric fields can induce phase changes in electrorheological(ER) fluids, from a liquid to semi-solid state, provided the field strength is larger than some critical value. We describe here an experimental and theoretical study considering yet a different class of phase changes, specifically those for an ER fluid in the presence of both shear flow and a time-varying electric field. We note that as the frequency of the field is decreased, the ER fluid will go from a liquid to an intermediate transition state, and eventually to a shear banding state. Our theoretical analysis further indicates that this phase change originates from competing effects of viscous and electrical forces. Ultimately, we conclude that it is possible to achieve various states and corresponding(desired)macroscopic properties of dynamic colloidal suspensions by adjusting the frequency of the externally applied electric field.