甲壳素类液晶高分子的研究--用CD谱研究N-邻苯二甲酰化壳聚糖溶致胆甾相的形成临界浓度

N邻苯二甲酰化壳聚糖在多种常见有机溶剂中能形成胆甾液晶相.用圆偏光二向色性谱(CD)研究了N邻苯二甲酰化壳聚糖的DMF、DMSO、DMAC和吡啶4种溶剂体系,在形成溶致胆甾液晶相前后的手性变化信息.CD谱图上观测到两类吸收,即在400nm附近较宽的吸收和330nm附近较尖锐的吸收.前者归属于胆甾相层片的超分子螺旋构象,而后者可以归属于分子链的螺旋构象.圆偏光二向色性可以作为测量胆甾液晶临界浓度的一种手段,它能捕捉到胆甾螺旋层片出现那一瞬间的浓度,以CD谱上在波长400nm左右刚出现肩峰的浓度为临界浓度,其值均比偏光显微镜法低1%,说明其灵敏度比偏光显微镜法高,且避免了偏光显微镜法的某种主观性.分别用两种方法旋转玻片进行CD测试,结果证明线性二向色性分量和双折射分量对胆甾层片螺旋的CD信号强度没有大的影响.     

带宽可调的斜边光纤光栅滤波器的设计与制作

基于遗传算法设计了斜边三角形光纤光栅(EFBG)的折射率调制函数;提出了光纤外径沿轴向变化、在拉应力下可获得可调谐的斜边三角形光纤光栅;计算分析了该器件多个物理参量对反射光谱的影响。在实验中,采用紫外激光扫描辐照方法,制备了短波边斜边带宽为0．7nm、反射率为96％的斜边三角形光纤光栅;采用程序控制氢氟酸腐蚀方法获得外径从原始62．5μm减小到45μm、在85mm长度内按设计要求变化的光纤光栅。对该光纤光栅施加从。到1．715N变化的拉力时,其反射光谱短波边的斜边带宽从0．7nm增加到2．3nm,实现了一种带宽大范围可调的斜边光纤光栅。     

大范围光纤布拉格光栅温度传感器增敏实验研究

简要分析了光纤布拉格光栅的温度响应及增敏原理,采用特殊耐高温有机聚合物对光纤光栅进行温度增敏封装,并通过改进光纤光栅的聚合物封装固化工艺,使用某种有机硅导热胶减小有机聚合物与套管材料的粘合度,消除了封装过程中由于聚合物材料不均匀收缩引起的光纤光栅反射谱啁啾化,实现20～180℃范围内光纤光栅传感器对温度高灵敏度测量。实验结果表明．聚合物封装光纤光栅传感器温度响应灵敏度在20～130℃为0．05nm／℃,在130～180℃达到了0．22nm／℃,并在两个区域保持较好的线性与重复性。此结构传感器封装工艺简单,易于实现,可用于高温恶劣环境下的温度单参量测量。     

一种新颖的由分插复用器构成的双向WDM网络

提出了一种新颖的双向波分复用网络结构,由多个分插复用器通过单模光纤连接而成。其中,分插复用器是基于声光效应和光纤布拉格光栅的反射特性制成的。由理论分析和实验得到的结果表明,该器件可实现一定数量信道的光信号的双向分插复用。这种双向波分复用光网络可按要求进行设计,使具有某种特征波长的光信号在设定位置的分插复用器中实现分插复用,使其按所设计的光路在波分复用网络中传输。     

一种准分布式光纤光栅漏油传感器

分别对两种结构的传感头组成的分布式光纤Bragg光栅漏油传感器进行实验后得出,具有限位装置的传感头组成的传感系统综合性能好于由另一种结构传感头组成的传感系统。具有限位装置的传感头不仅有较好的漏油检测响应性能,而且能防止相邻信号间的串扰,同时能很好保护光纤光栅不被拉断,更重要的是它受温度干扰较小。     

窄线宽光纤激光器进展

详细介绍采用光纤光栅获得窄线宽光纤激光器的各种技术,并讨论获得单模激光输出以及提高功率输出的方法。介绍了目前的最新进展,尤其是镱铒共掺磷酸盐玻璃DBR光纤激光所获得的最新数据,激光功率200mW,线宽1．75kHz。对光纤掺杂、光敏性以及光栅刻写等关键技术也进行了探讨。还重点介绍了作为应用之一的高功率激光系统前端种子源。     

铝槽封装光纤光栅传感器的增敏特性研究

提出了一种光纤布喇格光栅的铝槽封装工艺,并对铝槽封装光纤光栅传感器的应变与温度传感特性进行了实验研究和理论分析.与裸光纤光栅的测试结果比较表明,铝槽封装工艺基本不改变光纤光栅应变传感的灵敏性,但是温度灵敏度系数提高了3.5倍.经过该工艺封装的光纤光栅可以探测识别0.2 με的应变与0.02℃的温度变化.     

Shaping an antenna radiation diagram with discrete weights using the PSO algorithm and periodic and nest spaces

Using traditional methods, finding the weights that allow shaping a desired radiation diagram for an antenna in order to reject unwanted signals or maximize the desired signal reception, is possible.However, neither by iterative nor closed methods, can it be done while restricting the amplitudes and phases to a set of finite values for each of them. Also, it often happens that they cannot include in its formulation other types of specifications that are necessary to be achieved.Some modifications were implemented in the method Particle Swarm Optimization (PSO), which reduced the convergence time, especially in the search space of phases where there exists a periodicity that the original method does not take into account.PSO is an evolutionary algorithm, inspired by the social behavior of flocks of birds or fish, developed by Eberhart and Kennedy in 1995, and has been intensively applied in solving numerical Engineering problems.     

No cut-off phenomenon for the “Insect Markov chain”

In this work we show that the probability measure associated with the Insect Markov chain defined on the ultrametric space of the leaves of the q-ary rooted tree of depth n ≥ 2 converges to the stationary distribution without a cut-off behavior.      

Circular choosability is rational

The circular choosability or circular list chromatic number of a graph is a list-version of the circular chromatic number, that was introduced by Mohar in 2002 and has been studied by several groups of authors since then. One of the nice properties that the circular chromatic number enjoys is that it is a rational number for all finite graphs G, and a fundamental question, posed by Zhu and reiterated by others, is whether the same holds for the circular choosability. In this paper we show that this is indeed the case.