Observation of a diverse deviation from macropore-formation theory in silicon electrochemistry

Via anodizing patterned and unpatterned samples with a high HF concentration （[HF]）, the degree of deviation from pore-formation theory was found to be markedly different. Based on the analysis of scanning electron microscope （SEM） micrographs and current-voltage （I - V） curves, the variation of physical and chemical parameters of patterned and unpatterned substrates was found to be crucial to the understanding of the observations. Our results indicate that the initial surface morphology of samples can have a considerable influence upon pore formation. The electric-field effect as well as current-burst-model was employed to interpret the underlying mechanism.     

宽光谱平像场全息凹面光栅的优化研究

基于凹面光栅的几何理论,推导了子午、弧矢聚焦曲线的数学表达式和全息平像场凹面光栅制作参数的计算关系式.提出了一种新的在整个使用波长范围内同时消除子午和弧矢像差的最佳优化设计方法.这种方法不同于以光线追迹技术为基础的标准光学设计软件如CODEV或ZEMAX的优化设计方法,而是从数学表达式出发,采用光栅优化因子,对凹面光栅的子午聚焦曲线和弧矢聚焦曲线进行拟合,从理论上找到最佳的能够使子午和弧矢像差同时趋于零的像平面,然后再根据拟合参数设计制作光栅.用Matlab软件解决了子午聚焦曲线超越方程无法解的困难;讨论了不同光栅常数和入射角度时对两聚焦曲线拟合程度的影响.提出了在宽光谱使用条件下,可以通过减小入射角度和光栅刻线数来提高光谱像质.     

考虑塑性和刚度不匹配的焊接残余应力估算

现有残余应力计算方法未能考虑材料塑性变形和焊接接头刚度不匹配的影响,使得焊接残余应力计算结果和实际残余应力存在较大偏差.在2219-T87铝合金钨极氩弧焊焊接头残余应力测试基础上,提出一种基于非线性有限元和材料弹性模量分区的残余应力—释放应变曲线的残余应力计算方法,研究了材料塑性变形和接头刚度不匹配对焊接残余应力计算的影响.结果表明,焊接接头中非均质材料塑性不匹配可以引起对于残余应力计算的较大误差;材料塑性变形对残余应力的影响大于接头刚度不匹配对残余应力的影响.所提出方法修正了传统方法在焊接接头的残余应力计算中由于未考虑接头非均质材料塑性不匹配而引起的误差.     

水滑石层间阴离子为还原剂原位负载贵金属纳米颗粒

研究了以水滑石为载体原位负载贵金属纳米颗粒(Pd、Ag、Ru、Au)的方法,通过共沉淀合成甲酸根水滑石,以层间甲酸根为还原剂原位还原贵金属前驱体制得高分散水滑石(LDH)负载纳米颗粒。本方法无需载体预处理,操作方便、适用性强,阴离子前驱体(Au)和阳离子前驱体(Pd、Ag、Ru)均可顺利得到纳米颗粒。所得水滑石负载纳米颗粒系一种潜在的纳米催化剂,作为示例,Pd/LDH在Suzuki偶联反应中显示出较高催化活性。     

多组态二级微扰理论计算CH3O2激发光谱以及CH3O2→CH3＋O2解离反应

在C_s对称性和aug-cc-pVTZ基组水平下, 采用全活化空间自洽场方法(CASSCF)研究了CH₃O₂自由基基态及其阴阳离子的12个低激发态. 为了进一步考虑动态电子相关效应, 采用二级多组态微扰理论(CASPT2)获得更加精确的能量值. 所有计算得到的电子态都是价电子态, 而且所得绝热激发能和电子亲和势与实验值非常接近.在CASPT2//CASSCF理论水平下计算了CH₃O₂从²A"和²A'电子态的CH₃O₂→CH₃＋O₂的解离反应的势能曲线(PECs). 优化得到的裂解产物的几何结构和能量与分别优化CH₃和O₂得到的结果进行比较, 从而确定裂解产物的电子态. 结果表明, 从²A"和²A'电子态的解离反应分别对应产物CH₃(²A")＋O₂(³A")和CH₃(²A")＋O₂(¹A").     

Analysis of lettuce evapotranspiration across soil water

In this study, we evaluated the lettuce accumulated evapotranspiration (ET) across four levels of irrigation, using a nonlinear mixed‐effects model. The plants were grown in protected environments and monitored over 23 consecutive days. When the moisture of the substrate in the vessels reached 50% of their maximum retention capacity, the water levels were elevated according to four treatments: , , , and . The model appeared to provide a good fit to the data and showed that the estimates of the maximum amount of accumulated ET were similar for the three treatments with soil water deficit and lower for . The results of the study supported the idea that optimization of the ET of lettuce plants could be achieved through irrigation with deficit, also indicating that the economical use of water was the most efficient way to boost agricultural production. Recommendations for resource managers

• The continued growth of the world population will result in a decrease of quality and availability of water and also an increase in demand for food. Therefore, sustainability will depend on high agricultural productivity with rational use of water.
• Considered the most efficient technology for boosting agricultural productivity, irrigation is also the largest water consumer in the world. With any kind of irrigation in the vegetable production area, the water intake for the plants must be treated with great caution.
• Both a lack or excess in water can decrease plant productivity. The amount of water available in the soil should be enough to maximize production. It is shown that high levels of irrigation are not necessary for this.
• It is important to balance the amount of irrigated water for an optimal level, in order that the production has its the production is maximized and valuable water resources are not wasted.

     

对高能碰撞末态粒子的阶乘矩拟合修正曲线的方法

高能碰撞末态粒子在相空间的动力学分布存在着非均匀因素的影响,通过对这种非均匀因素影响的仔细研究,引入了修正系数,得到了拟合修正曲线的判据,给出了计算修正系数的方法.     

Poly[2,7‐(9,9‐dihexylfluorene)‐alt‐pyridine] with donor‐acceptor architectures: A new series of blue‐light‐emitting alternating copolymers

A novel series of well‐defined alternating poly[2,7‐(9,9‐dihexylfluorenyl)‐alt‐pyridinyl] (PDHFP) with donor‐acceptor repeat units were synthesized using palladium (0)‐catalyzed Suzuki cross‐coupling reactions in good to high yields. In this series of alternating polymers, 2, 7‐(9,9‐dihexylfluorenyl) was used as the light emitting unit, and the electron deficient pyridinyl unit was employed to provide improved electron transportation. These polymers were characterized by ¹H‐NMR and ¹³C‐NMR, gel permeation chromatography (GPC), thermal analyses, and UV‐vis and fluorescence spectroscopy. The glass transition temperature of copolymers in nitrogen ranged from 110 to 148 °C, and the copolymers showed high thermal stabilities with high decomposition temperatures in the range of 350 to 390 °C in air. The difference in linkage position of pyridinyl unit in the polymer backbone has significant effects on the electronic and optical properties of polymers in solution and in film phases. Meta‐linkage (3,5‐ and 2,6‐linkage) of pyridinyl units in the polymer backbone is more favorable to polymer for pure blue emission and prevention of aggregation of polymer chain than para‐linkage (2,5‐linkage) of the pyridinyl units. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4792–4801, 2004     

Thermokinetic Research Method for Simple-order Reactions. Double-thermoanalytical curve method

A novel thermokinetic research method for determination of the rate constant of a reaction taking place in a batch conduction calorimeter under isothermal conditions is proposed: the double-thermoanalytical curve method. The method needs only the characteristic time parameter t _m, the peak height Δ_m at time t _m and the peak area a*_m after time t _m for two thermoanalytical curves measured with different initial concentrations of the reactants: it conveniently calculates the rate constants. The thermokinetics of four reaction systems were studied with this method, and its validity was verified by the experimental results. This revised version was published online in July 2006 with corrections to the Cover Date.