Nonlinear logistic discrimination via regularized radial basis functions for classifying high-dimensional data

A flexible nonparametric method is proposed for classifying high- dimensional data with a complex structure. The proposed method can be regarded as an extended version of linear logistic discriminant procedures, in which the linear predictor is replaced by a radial-basis-expansion predictor. Radial basis functions with a hyperparameter are used to take the information on covariates and class labels into account; this was nearly impossible within the previously proposed hybrid learning framework. The penalized maximum likelihood estimation procedure is employed to obtain stable parameter estimates. A crucial issue in the model-construction process is the choice of a suitable model from candidates. This issue is examined from information-theoretic and Bayesian viewpoints and we employed Ando et al. (Japanese Journal of Applied Statistics, 31, 123–139, 2002)’s model evaluation criteria. The proposed method is available not only for the high-dimensional data but also for the variable selection problem. Real data analysis and Monte Carlo experiments show that our proposed method performs well in classifying future observations in practical situations. The simulation results also show that the use of the hyperparameter in the basis functions improves the prediction performance.     

Dynamics of photo-induced terahertz optical activity in metal chiral gratings

We investigated the dynamics of photo-induced optical activity of metal chiral gratings on an Si substrate for terahertz (THz) waves. We employed a new technique that enables optical-pump and THz-probe measurements via broadband THz spectroscopy at the microsecond time scale using a low-repetition-rate pump and a high-repetition-rate probe. We revealed that the THz optical activity decays as a result of the carrier diffusion effect because this optical activity is because of the presence of three-dimensional chiral structures of photo-carriers in the Si substrate.     

Stabilization of a steady state in oscillators coupled by a digital delayed connection

We propose the mapping of polynomial of degree 2S constructed as a linear combination of powers of spin-S (for simplicity, we called as spin-S polynomial) onto spin-crossover state. The spin-S polynomial in general can be projected onto non-symmetric degenerated spin up (high-spin) and spin down (low-spin) momenta. The total number of mapping for each general spin-S is given by 2(2^2S ? 1). As an application of this mapping, we consider a general non-bilinear spin-S Ising model which can be transformed onto spin-crossover described by Wajnflasz model. Using a further transformation we obtain the partition function of the effective spin-1/2 Ising model, making a suitable mapping the non-symmetric contribution leads us to a spin-1/2 Ising model with a fixed external magnetic field, which in general cannot be solved exactly. However, for a particular case of non-bilinear spin-S Ising model could become equivalent to an exactly solvable Ising model. The transformed Ising model exhibits a residual entropy, then it should be understood also as a frustrated spin model, due to competing parameters coupling of the non-bilinear spin-S Ising model.     

末端化聚酰胺和交联剂及光酸产生剂所组成的三元负型光敏支化聚酰胺

研究了由未端化支化聚酰胺、交联剂(MBHP)和光酸产生剂(PTMA)所组成的三元负型光敏聚合物体系.其中,不对称ABB′型单体4-(2,4-二氨基苯氧基)苯甲酸3在亚磷酸三苯酯(TPP)和吡啶(Py)的存在下,通过缩合聚合得到支化聚酰胺a,由其1H-NMR数据计算得支化度(DB)为0.36.接着用肉桂酰氯对支化聚酰胺进行末端化.采用IR,1H-NMR,GPC,TG/DTA对支化聚酰胺和末端化支化聚酰胺b的结构和性能进行了表征.由85wt%末端化支化聚酰胺b、10wt%交联剂(MBHP)和5wt%光酸产生剂(PTMA)所组成的光敏聚合物体系,在100℃预烘10min,采用436nm(g-line)紫外光曝光,随后在25℃于二甲基甲酰胺中显影10s,用水漂洗,110℃后烘3min后,得到负型图案,边界清晰且分辨率达40μm.     

Hyperbranched polyimides prepared by ideal A2+B3 polymerization,non-ideal A2+B3 polymerization and AB2 self-polymerization

In this paper, hyperbranched polyimides having the same repeating unit were synthesized by employing ideal A₂+B₃ polymerization, non-ideal A₂+B₃ polymerization and AB₂ self-polymerization methods. The polymerization behavior, polymer properties were compared for three methods. Hyperbranched polyimides by ideal A₂+B₃ polymerization, non-ideal A₂+B₃ polymerization and AB₂ self-polymerization methods show apparent difference in many physical properties, such as inherent viscosity, glass transition temperature, and film formation behavior etc. The hyperbranched polymers by the non-ideal A₂+B₃ polymerization are suitable for smooth, flexible and self-standing film preparation, which provides useful information for hyperbranched polymers toward self-standing materials.