NIR光谱的LLE-PLS非线性建模方法及应用

传统的偏最小二乘(PLS)建模方法不能有效反映近红外(NIR)光谱与分析样本的物理化学性质之间存在的非线性关系。局部线性嵌入(LLE)是一种新的非线性降维方法,属于流形学习方法,它能有效地发现高维数据中的本真低维结构。结合LLE和PLS,提出一种近红外光谱非线性建模的新方法,并用于建立丹参多酚酸盐柱层析过程中丹酚酸B含量的回归校正模型。该方法首先用LLE对NIR光谱数据降维,再用PLS建立校正模型。结果表明,与多元散射校正、一阶导等预处理方法结合PLS建模比较,参数优化后的LLE-PLS方法能更准确地预测丹酚酸B的含量,其交叉验证均方根误差为0.128 mg·mL-1、决定系数为0.998 8。基于NIR光谱及LLE-PLS建模,可实现丹参多酚酸盐柱层析过程的在线检测。     

Contrast Adaptation Decreases Complexity in Retinal Ganglion Cell Spike Train

The difference in temporal structures of retinal ganglion cell spike trains between spontaneous activity and firing activity after contrast adaptation is investigated. The Lempel-Ziv complexity analysis reveals that the complexity of the neural spike train decreases after contrast adaptation. This implies that the behaviour of the neuron becomes ordered, which may carry relevant information about the external stimulus. Thus, during the neuron activity after contrast adaptation, external information could be encoded in forms of some certain patterns in the temporal structure of spike train that is significantly different, compared to that of the spike train during spontaneous activity, although the firing rates in spontaneous activity and firing activity after contrast adaptation are sometime similar.     

Phase Transition and High Piezoactivity of Sb Doped （Na0.53K0.435Li0.035）Nb0.94Ta0.06 O3 Lead-Free Ceramics

Lead-free piezoelectric ceramics with the composition of （Na0.53K0.435Li0.035）Nb0.94Ta0.06 O3 （NKLNST） axe synthesized by a conventional solid-state sintering process. An MPB-like region between orthorhombic and pseudocubic phases is found in this system. The density, piezoelectric and dielectric properties axe enhanced greatly in this region. A composition （Na0.53K0.435Li0.035）（Nb0.94Ta0.06）O3 is found to have excellent electrical properties： d33 = 320pC/N, kp= 49% and kt =43%, as well as relatively low loss, tan δ=4.2%, and high relative density higher than 96%, which indicate that this ceramics is a promising lead-free piezoceramics replacing for lead zirconate titanate.     

脉管制冷用于低温超导磁体冷却的可行性分析

采用制冷机直接冷却的低温超导磁体系统与传统液氮冷却方式相比，具有轻便紧凑、运行简单、维护方便、可长时间连续运行等优点；而脉管制冷由于冷端无运动部件，与传统的G-M制冷机相比，具有结构简单、运行可靠、振动小等优点．本文结合我们在液氮温区脉管制冷方面的技术，从漏热和经济性两方面探讨了将脉管制冷直接用于冷却一个5特斯拉NbTi低温超导磁体的可行性，为后期系统的搭建奠定基础．     

尘埃粒子计数器中光源对传感器光通量的影响分析

在Mie散射理论基础上，由单分散射的光强表达式导出在偏振光的入射条件下一定立体角内的散射光通量的表达式，并与自然光入射作比较。计算了在相同强度不同光源入射下，尘埃粒子计数器的两种常用散射光收集系统收集的散射光通量。结果表明：采用近前向散射光收集系统得到的光通量相等；而采用直角方向散射光收集系统时两者并不相等，且在平面偏振光入射时，收集的散射光通量还跟探测器中心与入射光偏振方向夹角有关。用MATLAB编程计算，得出了在探测器中心与偏振方向的夹角成90°或270°位置时，收集的散射光通量有极值的结论，为激光尘埃计数器传感器光学设计提供了依据。     

低温大试样热胀系数测试

本介绍了用熔融石英引伸法测量硬质材料热胀系数的简便装置,并给出了试样在液氦温区到室温的测量结果,数据的一致性以及与已有献数据比较取得了不错的结果．     

Y系超导螺管储能磁体的优化设计

磁体结构的好坏将直接关系到磁体的制造成本以及磁体能否正常运行.在磁体结构的优化设计中,选定磁体的体积为目标函数,在满足磁体储能,符合超导材料的B～J特性,尽量减小漏磁等条件下,使目标函数达到最小.文章选定新一带超导涂层导体YBCO为SMES线圈的制造材料,分析了Y系带材的材料特性,并采用大型有限元仿真软件ANSYS和磁体优化中常用的算法-模拟退火算法(simulated annealing)对SMES线圈进行优化仿真分析,得出最优的磁体结构.     

基于分时原理的多相流体比例分配方法

提出了从“时间”上对多相流进行分配的新思路,分析了分时分配的基本原理,并设计了具体的实现方式。在空气-水实验回路上对分时分配装置进行了实验研究和验证。分时分配的基本原理就是通过“分时”的方法,使整个分配器“空间”内的多相流都能按照给定的时间份额周期性地交替流向对应的支路,从而保证各支路内的多相流具有高度一致的相含量和确定的流量比例。实验研究证明,分时分配法具有切实的可行性,分流比等于分时比且与流量和流体的物性无关,仅取决于分配器的几何参数。     

3 ω线法测量液体热参数影响因素分析

首先给出基于谐波探测技术测量液体导热系数和热扩散系数的3ω线法的基本原理.采用实验和理论分析相结合的方法,分析了加热丝结构参数和自身热参数对温度波动和测量结果的影响.给出了加热丝直径和长度的合理范围.液体导热系数比较小时可以利用三次谐波的实部和虚部的交点测量液体的比热容.     

Irradiation Test of FPGA for BES-Ⅲ

The irradiation effect of FPGA, applied in Front-end Electronics for experiments of High-Energy Physics, is a serious problem. The performance of FPGA, used in the front-end card of Muon Counters of BES-III project, needs to be evaluated under irradiation. SEUs on Altera ACEX 1K FPGA, observed in the experiment under the irradiation of γ ray, 14 and 2.5MeV neutrons, was investigated. We calculated involved cross-section and provided reasonable analysis and evaluation for the result of the experiment. The conclusion about feasibility of applying ACEX 1K FPGA in the front-end card of the readout system of Muon Counters for BES-III was given.