Dense wavelength division demultiplexing using photonic crystal waveguides based on cavity resonance

We demonstrated a photonic crystal waveguide based dense wavelength division multiplexing device using the resonances in the cavities. The demultiplexing is achieved through filtering. This filtering is achieved by varying the radii of the surrounding holes of the cavity, which in turn changes the resonant wavelength of the cavity. The four wavelengths demultiplexed in the design are 0.8 nm apart in the optical region centered on 1.55 and 1.56 μm. The device designed and simulated has easy to realize structure as well as high quality factor. Two-dimensional Finite Difference Time Domain (FDTD) is chosen to do the simulation of this work.     

多光束非定域干涉反射光强分布

研究了多光束非定域干涉现象,得到了多光束非定域干涉的反射光强分布函数.数值计算结果表明:随着镜面反射系数的增加,多光束非定域干涉条纹半值宽度降低,条纹变得更加锐细,光谱分辨率提高;当镜面反射率较高时,除了暗条纹外,在低干涉级次处紧邻暗条纹还有很窄的亮条纹存在;亮条纹振幅逐渐衰减至背景光强度,干涉级次越低亮条纹振荡越明显;第一束反射光提供了一个均匀的背景,第二束反射光的加入产生了双光束干涉,干涉条纹较粗,对比度较低,更多光束的加入使干涉暗条纹变得锐细,在相邻暗条纹间出现了明暗相间的低强度明暗条纹;足够多光束的加入使相邻暗条纹间低强度变化的明暗条纹消失,同时在紧邻暗条纹处出现了振幅振荡衰减的亮条纹.最后,将多光束非定域干涉理论应用于光学滤波器的研究,结果表明:提高镜面反射率,可以显著降低多光束非定域干涉的滤波带宽;改变镜面间距,可以灵活调整多光束干涉仪滤波波长和相消波长间距.     

EFFECT OF Z-PINS'' DIAMETER, SPACING AND OVERLAP LENGTH ON CONNECTING PERFORMANCE OF CMC SINGLE LAP JOINT

The effect of through-thickness reinforcement by composite pins (Z-pins) on the static tensile strength and failure mechanisms of the joints made from ceramic matrix composite (CMC) is investigated.Overlap length of the single lap joint is 15 mm,20 mm,23 mm,37 mm,and 60 mm,respectively.The experimcntal results indicate that the final failure modes of the joints can be divided into twó groups,(a) the bond-line stops debonding until crack encounters Z-pins;and then the adherends break at the location of Z-pins,when overlap length is more than 20 mm;(b) the bond-line detaches entirely and Z-pins are drawn from adherends,when overlap length is equal to 15 mm.A simple efficient computational approach is presented for analyzing the benefit of through-thickness pins for restricting failure in the single lap joints.Here,the mechanics problem is simplified by representing the effect of the pins by tractions acting on the fracture surfaces of the cracked bond-line.The tractions are prescribed as functions of the crack displacement,which are available in simple forms that summarize the complex deformations to a reasonable accuracy.The resulting model can be used to track the evolution of complete failure mechanisms,for example,bond-line initial delamination and ultimate failure associated with Z-pin pullout,ultimate failure of the adherends.The paper simulates connecting performance of the single lap joints with different Z-pins' diameter,spacing and overlap length;the numerical results agree with the experimental results;the numerical results indicate enlarging diameter and decreasing spacing of Z-pins are in favor of improving the connecting performance of the joints.By numerical analysis method,the critical overlap length that lies between two final failure modes is between 18 mm and 19 mm,when Z-pins' diameter and spacing are 0.4 ram,5 ram,respectively.     

用ZnS做诱导金属滤光片的间隔层

从制备工艺稳定性出发,设计的诱导金属滤光片的膜系结构与以往设计的膜系结构有所不同,即将n_L低折射率冰晶石间隔层改用n_H高折射率ZnS做间隔层。如果金属与间隔层结合良好,本文中给出的设计计算公式适合于做间隔层的任意膜层。通常膜系的透光率T是膜层厚度nd的函数T=f(nd)。高折射率n_H的膜层函数T_H=f(n_Hd)变化较快,低折射率n_L的膜层函数T_L=f(n_Ld)变化较慢,尤其是在膜层厚度接近λ_0/2的区域更为明显。实践证明选用高折射率ZnS做诱导金属银滤光片的间隔层比选用低折射率冰晶石做间隔层制备工艺稳定,产品合格率高。     

辛烷基苯酚聚氧乙烯醚与正癸醇层状液晶的有序性及层状结构

研究了层状液晶的层状结构及有序性,用偏振光显微镜法确定了辛烷基苯酚聚氧乙烯醚(TritonX 100)与正癸醇体系25℃时层状液晶的区域,绘制了部分相图,并用核磁共振氢谱法(2H NMR)进一步验证;用自旋标记电子自旋共振法测定了层状液晶分子排列的有序参数,研究结果显示,不同组分TritonX 100 /n C10H21OH/H2O体系层状液晶的超精细偶合常数基本相同,表明层状液晶中的微极性是一致的.而有序参数随着TritonX 100含量的增加而增加,随着层状液晶中水含量的增加而减少;用小角度X射线衍射方法测定了层状液晶的层间距离,并计算了水分子在层状液晶中的渗透率,其渗透率约为50%.     

Adjustment and evaluation of an LDA probe for accurate flow measurement

An LDA probe with optimized measuring volume was obtained based on repeated adjustments of a preconfigured LDA system with a calibrated spinning disc. A retriggerable pulse-width-and-time-delay module was used to trigger and freeze favorable Doppler bursts. After a repeated beam-steering procedure and a fringe-pattern analysis, we found that the variation of fringe spacing throughout the measuring volume was reduced from 3% to 0.28%, such that the adjusted probe gave more accurate measurements. To verify this applicability in velocity calibration, the fringe spacing of the adjusted LDA measuring volume was treated as a velocity coefficient, and its mean and measurement uncertainty was experimentally estimated. Analysis shows that the expanded uncertainty of the coefficient was 0.10% at the 95% level of confidence for both the components of the LDA. The results demonstrated that the adjusted LDA system was qualified to perform accurate flow measurement.     

大碳层间距的沥青基多级孔碳材料的制备及其在超级电容器中的应用

基于KOH活化法,以纳米级片层多孔MgO为模板剂,制备大碳层间距的沥青基超级电容器用多级孔碳材料。考察了模板剂添加量对多孔碳材料孔分布、碳层间距等理化性能及电化学性能的影响。结果表明模板剂添加量为沥青质量的25%时,多孔碳材料比表面积、孔体积分别为2 634 m~2·g~(-1)、1.12 cm~3·g~(-1),碳层间距高达0.374 nm,用于超级电容器电极材料时,1和20A·g~(-1)电流密度下的比电容分别为338和277 F·g~(-1),经过10 000次循环恒电流充放电,1 A·g~(-1)下容量保持率为93.5%,展现了优异的电化学性能。     

磷钨酸插层MgAl水滑石层间距的调变及催化酯化脱酸性能

通过改变离子交换温度和时间合成了具有不同层间距的磷钨酸(H_3PW_(12)O_(40),HPW)插层MgAl水滑石(LDHs),采用XRD、FT-IR、Raman、~(31)P MAS NMR、ICP-AES和Hammett指示剂-正丁胺滴定法等表征其性质,并研究其对模型原油的催化酯化脱酸性能。高的离子交换温度有利于形成较大的层间距(d_(003)约1.46 nm),较长的交换时间有利于形成较小的层间距(d_(003)约1.05 nm)。不同的层间距源自HPW在层间不同的存在形式,P_2W_(18)O_(62)~(6-)以C_2轴倾斜于层板和PW_(11)O_(39)~(7-)以C_2轴垂直于层板的方式排列于层间时,形成d_(003)约1.46 nm的层间距;PW_(12)O_(40)~(3-)与层板发生嫁接,并以C_2轴垂直于层板的方向排列于层间时,形成d_(003)约1.05 nm的层间距。层间P_2W_(18)O_(62)~(6-)和PW_(11)O_(39)~(7-)能产生更高比例的中强酸中心,同时大的层间距有利于反应物扩散进入层间与酸中心接触,能够提高LDHs的催化酯化脱酸性能。     

Phase behaviour and structural properties of two members of biphenylyl benzoate chiral mesogenic series

ABSTRACT

Phase behaviour and structural properties of two members of biphenylyl benzoate chiral mesogenic series (2F3R and 3F3R) have been investigated. While both the compounds exhibit SmC* phase over a wide temperature range, 2F3R forms orthogonal SmA* from tilted SmC* on heating but 3F3R melts directly to the isotropic phase. The SmA* phase of 2F3R is found to have de vries characteristics with small effective layer contraction. Both the samples on cooling form hexagonal SmF* phase below SmC* phase. On further cooling soft crystal like hexagonal SmJ* phase is formed in 2F3R, undergoing a change in the tilt direction, but in 3F3R, SmG* phase is formed without any change in the tilt direction. A coexistence phase of (SmC*+SmF*) is also observed in a certain temperature range. Slight differences in the dipole moment and molecular conformation of the two molecules give rise to a subtle change in the intermolecular interaction and play an important role in the appearance of different phases in the two compounds. Cell parameters of SmF*, SmG*, SmJ* phases have also been determined. Layer spacings, tilt angles, average intermolecular spacings and correlation lengths have been measured. How some of these properties compare with other members of the series has been discussed.