Design of linear phase FIR filters using fractional derivative constraints

In this paper, the designs of linear phase FIR filters using fractional derivative constraints are investigated. First, the definition of fractional derivative is reviewed briefly. Then, the linear phase FIR filters are designed by minimizing integral squares error under the constraint that the ideal response and actual response have several same fractional derivatives at the prescribed frequency point. Next, the fractional maximally flat FIR filters are designed by letting the number of fractional derivative constraints be equal to the number of filter coefficients. Finally, numerical examples are demonstrated to show that the proposed method has larger design flexibility than the conventional integer derivative constrained methods.     

用于气体浓度检测的VCSELs温度控制电路设计

在利用可调谐半导体激光器吸收光谱（TDLAS）技术对气体浓度进行检测时,检测系统对激光器的温度稳定性要求较高。提出了一种基于max1978的VCSEL激光器自动温度控制（ATC）方案,建立了热电制冷器（TEC）的数学模型,对TEC的热惯性进行了测试,以热惯性测试结果为基础对比例积分微分控制（PID）电路参数进行了整定,设计出了具有较高控制性能的温度控制电路。电路采用闭环负反馈自动控制方案,采用PID电路产生控制信号,驱动TEC,实现了对VCSEL激光器工作温度的有效控制。实验测试结果表明,电路的温度控制精度达到+0.03℃,较好地实现了激光器工作温度稳定性的控制。     

对称型席夫碱类二茂铁衍生物的合成与性能研究

以二茂铁甲醇为原料,经Wittig反应后与2,6-(双胺基)-苯并[1,2-d-4,5-d′]双三唑-4,8(2H,6H)-二酮缩合,合成了一个D-π-A-π-D结构的二茂铁席夫碱类金属有机三阶非线性光学材料。化合物结构经1H NMR,MS表征确认。测定了该化合物的紫外-可见吸收光谱,用简并四波混频(DFWM)检测了其三阶非线性参数,检测波长为800 nm;脉冲宽度为80 fs。该化合物的三阶非线性极化率χ(3)值为3.67×10-13esu(静电单位),分子二阶超极化率γ值为3.49×10-31esu,表明该化合物具有良好的三阶非线性光学性能,优于现有的二茂铁类金属有机材料。探讨了分子结构对三阶非线性光学性能的影响,长共轭链、强电子离域能可提高分子三阶非线性光学性能。     

可生物降解润滑油添加剂哌嗪衍生物的合成及性能评定

选用六水合哌嗪为母体,二氯甲烷为溶剂,三乙胺为缚酸剂,正己胺、十二胺、氯乙酰氯为原料,合成新型可生物降解润滑油添加剂1,4-双（二硫代甲酸乙酰正己胺）哌嗪和1,4-双（二硫代甲酸乙酰十二胺）哌嗪;采用FT-IR,1HNMR,TG手段对合成产物进行结构表征及对产品热稳定性进行测试。以菜籽油为基础油,采用四球摩擦磨损试验机考察合成添加剂的抗磨性能,并对其进行可生物降解性测定。结果表明：合成产品与预测结构相同,热分解温度最低为305 ℃,与菜籽油的溶解度高达2.58%（质量分数）,1,4-双（二硫代甲酸乙酰十二胺）哌嗪具有较好的抗磨性能,1,4-双（二硫代甲酸乙酰正己胺）哌嗪具有较好的减摩性能,两者均具有优异的可生物降解性能（BDI大于80%）。     

光动力疗法对S180荷瘤小鼠肿瘤细胞损伤的红外光谱研究

测定了光动力疗法对S180荷瘤小鼠肿瘤细胞损伤的红外光谱。结果表明,肿瘤细胞损伤后核酸、蛋白质、脂质的特征峰都有不同程度的改变,表现为峰值降低,频率发生蓝移或红移。结论：光动力作用肿瘤组织,可使肿瘤细胞的核酸、蛋白质、脂质的构型和构象发生变化。DNA单、双链发生断裂,蛋白质失去活性,细胞膜功能丧失。细胞的结构和功能被破坏,表现为细胞的凋亡和坏死。     

Fractional Order Digital Differentiator Design Based on Power Function and Least squares

In this article, we propose the use of power function and least squares method for designing of a fractional order digital differentiator. The input signal is transformed into a power function by using Taylor series expansion, and its fractional derivative is computed using the Grunwald–Letnikov (G–L) definition. Next, the fractional order digital differentiator is modelled as a finite impulse response (FIR) system that yields fractional order derivative of the G–L type for a power function. The FIR system coefficients are obtained by using the least squares method. Two examples are used to demonstrate that the fractional derivative of the digital signals is computed by using the proposed technique. The results of the third and fourth examples reveal that the proposed technique gives superior performance in comparison with the existing techniques.     

Accuracy of the zero crossings of the second directional derivative as an edge detector

In this paper the accuracy of the second directional derivative edge detector is analyzed, based on a number of idealized edge models. The results are compared with those for the Laplacian edge detector. Errors are shown to be small under a number of conditions. These conditions are less severe for the second directional derivative than for the Laplacian edge detector. Spurious or phantom edges can be removed by checking the sign of the third directional derivative, though this is not enough to remove all large errors. Indeed, it is also shown that large errors will be obtained if no threshold is set on the magnitude of a third order derivative.This work was supported by the Belgian National Fund for Scientific Research (NFWO).     

分数算子描述的粘弹性材料的本构关系研究

从分数导数的定义出发,提出了在经典粘弹性模型理论中采用Abel粘壶取代传统牛顿粘壶的新观点.将有机硅高分子材料在MTS831.10材料试验机上进行动态力学行为试验,对试验结果分别用经典粘弹性模型和分数导数模型进行拟合.结果表明,分数导数Kelvin模型可以同时精确地拟合高分子材料的存储模量和损耗模量随频率变化的曲线,而且其形式简单、统一,在计算过程中需要调整的参数很少.