非对称阻力元件抑制直流的实验研究

简要分析了双向进气型脉冲管制冷机中存在的直流现象及其抑制措施;使用所研制的两台非金属同轴脉冲管制冷机,通过测量其蓄冷器外壁温度分布的方法,实验验证了基于闭合回路的固有直流的方向;通过分析其降温曲线及对冷头最低无负荷温度的影响,验证了可以利用非对称阻力元件产生相反方向的附加直流以消除系统中的固有直流,从而取得较好的制冷效果。实验对其效果进行了量化分析。     

任意两态叠加多模泛函叠加态光场的等幂次差压缩

构造了任意两态叠加多模泛函叠加态光场|ψ(2)f>q,利用多模辐射场广义非线性等幂次高次差压缩的一般理论,研究了态|ψ(2)f>q的广义磁场分量的非线性等幂次N次方差压缩特性.得到了一般理论结果,讨论了两种特殊两态叠加多模泛函叠加态光场的差压缩特性.结果表明:1)当qN为偶数时,第一类两态叠加多模泛函叠加态光场和虚相干两态叠加多模泛函叠加态光场都不出现广义磁场分量的非线性差压缩效应,也不处于N-j最小测不准态;2)当qN为奇数时,在一定条件下,任意两态叠加多模泛函叠加态光场中,广义磁场分量呈现出周期性变化的广义非线性N次方差压缩效应.     

基于独立成分分析的高光谱图像异常检测

针对高光谱图像中背景及目标先验知识未知条件下的异常目标检测问题,提出了一种基于独立成分分析(ICA)的异常探测算法.首先估计原始数据的虚拟维(VD)以确定要分离的独立成分个数,在此基础上进行快速独立成分分析(FastICA),然后基于平均局部奇异度选择含异常信息较多的独立成分,最后使用丰度量化算法得到异常目标的丰度图像...     

Fixed-point algorithms for constrained ICA and their applications in fMRI data analysis

Constrained independent component analysis (CICA) eliminates the order ambiguity of standard ICA by incorporating prior information into the learning process to sort the components intrinsically. However, the original CICA (OCICA) and its variants depend on a learning rate, which is not easy to be tuned for various applications. To solve this problem, two learning-rate-free CICA algorithms were derived in this paper using the fixed-point learning concept. A complete stability analysis was provided for the proposed methods, which also made a correction to the stability analysis given to OCICA. Variations for adding constraints either to the components or to the associated time courses were derived too. Using synthetic data, the proposed methods yielded a better stability and a better source separation quality in terms of higher signal-to-noise-ratio and smaller performance index than OCICA. For the artificially generated brain activations, the new CICAs demonstrated a better sensitivity/specificity performance than standard univariate general linear model (GLM) and standard ICA. Original CICA showed a similar sensitivity/specificity gain but failed to converge for several times. Using functional magnetic resonance imaging (fMRI) data acquired with a well-characterized sensorimotor task, the proposed CICAs yielded better sensitivity than OCICA, standard ICA and GLM in all the target functional regions in terms of either higher t values or larger suprathreshold cluster extensions using the same significance threshold. In addition, they were more stable than OCICA and standard ICA for analyzing the sensorimotor fMRI data.     

Color Zone Map in Peripheral Vision at Various Illuminance Levels

We measured the entire region of mesopic and photopic vision to determine the color zone covering the visual field with unique red, yellow, green, and blue hue components. Eight kinds of test stimuli in the natural color system (NCS) color notation system were used. These stimuli were presented at horizontal and vertical meridians, and at meridians inclined at 45° angles. The illuminance level was set at six levels: 0.01 lx-1000 lx. The evaluation method measured chromatic, white, and black components as well as the hue component of the stimuli. Results show that the color zone of the retina extended further into the periphery with increasing illuminance; the response of opponent colors y-b was shown to be greater than that of the opponent colors r-g.     

在高氯酸铕-二苯亚砜-邻菲罗啉三元配合物中Pr3+对Eu3+发光的影响

合成了一系列异核配合物[(Eu1-xPrx)(DPSO)(phen)3(ClO4)2]ClO4*nH2O(x=0.000～0.200, DPSO为二苯亚砜, phen为邻菲罗啉, n=1, 2, 3, 4, 5, 6). 对配合物进行了组成分析, 摩尔电导, IR光谱及荧光激发和发射光谱的测定. 荧光光谱测定结果表明 本身不发光的Pr3+对Eu3+的发光产生较大影响, 当Pr3+的掺入量为0.001 mol时, 可使Eu3+的发光强度提高到200%以上,随着Pr3+浓度的增大,对Eu3+的发光先敏化后猝灭.Eu3+在配合物中所处的格位对称性低,无对称中心.     

大口径平面光学元件超精密加工技术的研究

为了解决激光核聚变装置中大口径平面光学元件的批量制造难题,将先进制造技术和传统抛光技术相结合,提出了一种新的工艺方法,即使用ELID(在线电解)磨削代替传统的铣磨和初抛工序,以提高生产效率。利用数控抛光将工件抛光至最终的面形精度,以提高生产效率和减少边缘效应。将连续抛光作为最终加工工序,使加工工件的表面粗糙度和波纹度达到工程要求。实验证明这一新的工艺方法是可行的。     

贫金属星的中子俘获元素

利用分量系数公式并结合太阳系元素丰度的最新数据,计算了6?4颗贫金属星的中子俘获元素丰度.结果显示,快中子俘获过程(r过程)是贫金属星中子俘获元素的主要来源,且金属丰度小于–2.5的贫金属星的重中子俘获元素产量可能来自于纯r过程;重中子俘获元素与轻中子俘获元素来自于不同的天体物理场所     

近红外光谱结合ELM快速检测固态发酵过程参数pH值

pH值是固态发酵过程关键参数之一,为此提出基于近红外光谱技术的秸秆蛋白饲料固态发酵过程参数pH值检测方法。利用近红外光谱系统获取140个固态发酵过程产物样本在10 000～4 000cm-1范围内的近红外光谱数据,通过酸度计测得近红外光谱预测模型的参考测量值;运用ELM算法建立pH值的预测模型,在模型建立过程中由交互验证法确定最佳主成分因子数和ELM网络隐含层节点数。试验结果显示:最佳ELM网络模型的拓扑结构为10-40-1,模型预测集相关系数(Rp)和预测均方根误差(RMSEP)分别为0.961 8和0.104 4。研究结果可为固态发酵过程参数的在线检测提供技术基础。     

Classical Molecular Dynamics Model for Coupled Two‐Component Plasmas – Ionization Balance and Time Considerations

The dynamic properties of ion‐electron two‐component plasmas (TCP) are studied by using classical molecular dynamics (MD) simulations. There is a variety of time dependent and structural results that MD is able to provide in complement to other methods, e.g., useful micro‐field sequences can be generated. The method deals with some specific difficulties: the mass ratio between ions and electrons enforces very small time‐steps appropriate to follow electrons motion while, ions must move significantly in order to build, self consistently, their spatial structure. This results in expensive simulations. Electron trajectories are trapped and de‐trapped with multiple electron collisions around ions resulting in the occurrence of quasi metastable bound electron states. An analysis of micro‐fields at neutral in a hydrogen plasma reveals the need to consider a complete hierarchy of time scales extended typically over 7 order of magnitude, i.e., from a time‐step: ～10^‐19s, to a time required to obtain statistical averages, ～10^‐11s. In order to extend the MD capabilities in representing real coupled plasmas a classical ionization/recombination process has been implemented allowing to follow the evolution of plasmas involving several ion stages and model the ionization balance. Here again TCP simulations deal with extended time‐scale providing information about relaxation of non equilibrium plasma states (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)