Ionic polymers with expanded π‐conjugation systems derived from through‐space interaction in piperazinium and homopiperazinium rings

Reactions of N‐(2,4‐dinitrophenyl)‐4‐arylpyridinium chlorides (aryl (Ar) = phenyl and 4‐biphenyl) with piperazine or homopiperazine caused opening of the pyridinium ring and yielded polymers that consisted of 5‐piperazinium‐3‐arylpenta‐2,4‐dienylideneammonium chloride (? N(CH₂CH₂)₂N⁺ (Cl^?)?CH? CH?C(Ar)? CH?CH? ) or 5‐homopiperazinium‐3‐arylpenta‐2,4‐dienylideneammonium chloride (? N(CH₂CH₂CH₂)(CH₂CH₂)N⁺ (Cl^?)?CH? CH?C(Ar)? CH?CH? ) units. ¹H NMR spectral analysis suggested that the π‐electrons of the penta‐2,4‐dienylideneammonium group of the polymers were delocalized. UV‐visible spectral measurements revealed that the π‐conjugation system expanded along the polymer chains because of the orbital interaction between electrons of the two nitrogen atoms of the piperazinium and homopiperazinium rings. However, the π‐conjugation length depended on the distance between the two nitrogen atoms; that is, the polymers containing the piperazinium ring had a longer π‐conjugation length than those containing the homopiperazinium ring. Conversion of the piperazinium and homopiperazinium rings from the boat to the chair form led to a decrease in the π‐conjugation length. The surface of pellets that were molded from the polymers exhibited metallic luster, and these polymers underwent electrochemical oxidation in solution. Copyright © 2010 Society of Chemical Industry     

High Field Magnetoresistance and Magnetic Torque in One-Dimensional Organic Conductor TPP[Fe(Pc)(CN)2]2

Magnetoresistance (MR) and magnetic torque measurements are performed for a magnetic organic conductor TPP[Fe(Pc)(CN)₂]₂. The results suggest that the large negative MR is associated with a magnetic transition. This magnetic transition is considered as a metamagnetic transition of the localized Fe moments, and the MR effect is qualitatively explained by an analogy with the double exchange interaction system.     

Robust and Efficient Pattern Classification using Large Geometric Margin Minimum Classification Error Training

Recently, one of the standard discriminative training methods for pattern classifier design, i.e., Minimum Classification Error (MCE) training, has been revised, and its new version is called Large Geometric Margin Minimum Classification Error (LGM-MCE) training. It is formulated by replacing a conventional misclassification measure, which is equivalent to the so-called functional margin, with a geometric margin that represents the geometric distance between an estimated class boundary and its closest training pattern sample. It seeks the status of the trainable classifier parameters that simultaneously correspond to the minimum of the empirical average classification error count loss and the maximum of the geometric margin. Experimental evaluations showed the fundamental utility of LGM-MCE training. However, to increase its effectiveness, this new training required careful setting for hyperparameters, especially the smoothness degree of the smooth classification error count loss. Exploring the smoothness degree usually requires many trial-and-error repetitions of training and testing, and such burdensome repetition does not necessarily lead to an optimal smoothness setting. To alleviate this problem and further increase the effect of geometric margin employment, we apply in this paper a new idea that automatically determines the loss smoothness of LGM-MCE training. We first introduce a new formalization of it using the Parzen estimation of error count risk and formalize LGM-MCE training that incorporates a mechanism of automatic loss smoothness determination. Importantly, the geometric-margin-based misclassification measure adopted in LGM-MCE training is directly linked with the geometric margin in a pattern sample space. Based on this relation, we also prove that loss smoothness affects the production of virtual samples along the estimated class boundaries in pattern sample space. Finally, through experimental evaluations and in comparisons with other training methods, we elaborate the characteristics of LGM-MCE training and its new function that automatically determines an appropriate loss smoothness degree.     

Analysis of free-carrier optical absorption used for characterization of microcrystalline silicon films

The analysis of free-carrier optical absorption was applied to investigation of electrical properties for doped microcrystalline silicon films formed at 100–180°C by the RF-plasma-enhanced chemical vapor deposition method. The analysis gave in-depth characteristics of the carrier mobility and the carrier density. The electron mobility was 8 cm²/Vs (phosphorous doped) and 6 cm²/Vs (boron doped) at the surface region and it decreased to 1 cm²/Vs at bottom film/substrate interfaces. The carrier mobility and density were much higher than those obtained by Hall effect current measurements. It shows the existence of substantial non-activated and disordered regions among crystalline grains.     

Microcrystalline Si films deposited from dichlorosilane using RF-PECVD

Microcrystalline silicon has been fabricated using a conventional RF-PECVD method with a dichlorosilane/hydrogen mixture. Better crystallinity, lower hydrogen content and different preferential orientation have been obtained in comparison to those from a silane–hydrogen mixture. It was also found that a small addition of silane to dichlorosilane markedly deteriorates the crystallinity. These differences are discussed in terms of the surface reaction during the growth.     

Equivalent-circuit model for electrostatic micro-torsion mirror

Equivalent circuit model for micro-torsion mirror using open-source circuit simulator is reported, which gives a convenient technique for the design of circuits with electrostatic actuators. In the simulation, linear equations for electrical system, mechanical system, and transducer between both systems are considered. Mathematical operations of these equations are interrupted as appropriate circuits, so that a seamless multi-physics mixed simulation becomes possible.     

A thin‐film silicon solar cell and module

We have developed a new light‐trapping scheme for a thin‐film Si stacked module (Si HYBRID PULS module), where a (a‐Si:H/transparent interlayer/microcrystalline Si) thin‐film was integrated into a large‐area solar cell module. An initial aperture efficiency of 13·1% has been achieved for a 910 × 455 mm Si HYBRID PLUS module, which was independently confirmed by AIST. This is the first report of the independently confirmed efficiency of a large‐area thin‐film Si module with an interlayer. The 19% increase of short‐circuit current of this module was obtained by the introduction of a transparent interlayer that caused internal light‐trapping. A mini‐module was shown to exhibit a stabilized efficiency of 12%. Outdoor performance of a Si HYBRID (a‐Si:H / micro‐crystalline Si stacked) solar cell module has been investigated for over 4 years with two different kinds of module (top and bottom cell limited, respectively). The HYBRID modules limited by the top cell have exhibited a more efficient performance than the modules limited by the bottom cell, in natural sunlight at noon. Copyright © 2005 John Wiley & Sons, Ltd.