Plastic optical fibers with fluoroalkyl methacrylate copolymer as their core

Novel plastic optical fibers having a core made of a crosslinking copolymer containing mainly fluoroalkyl methacrylate (FMA–POFs) were fabricated and their optical properties were analyzed. In the visible wavelength region, attenuation losses of as-manufactured FMA–POFs were low and their loss spectra were similar to that of the plastic optical fiber whose core was made of methyl methacrylate copolymer (MMA–POF). But after heating at 160°C in air, increases in attenuation losses of FMA–POFs were about 10 times smaller than that of the MMA–POF. FMA–POFs had an optical window at 780 nm. There was hardly any change in loss at 780 nm compared with the loss increase at 660 nm. This indicated that FMA–POFs would be applicable to optical communications at 780 nm in the near-IR region.     

Analysis of thermal degradation for plastic optical fibers

Attenuation loss of plastic optical fibers (POFs) gradually increases with long use at high temperatures. We separated attenuation loss of the POFs before and after heating at 150°C in air into four loss factors, and identified the main factor for attenuation loss increase as electronic transition absorption loss (α_e). The increase of α_e was caused by a thermal oxidation reaction of the core polymer in the POF. But, according to NMR and FT-IR spectra, elementary analysis, etc., hardly any reaction products were detected. We assume that the reaction products were only a small amount of the conjugated carbonyl groups. So we fabricated POFs containing model compounds with conjugated carbonyl groups, and measured their attenuation loss. The attenuation loss spectra of these POFs were similar to those of thermally degraded POFs. Consequently, a very small amount of conjugated carbonyl groups were formed by the thermal oxidation reaction of core polymer so that α_e increased to an unacceptable level.     

Centrality in sociocognitive networks and social influence: An illustration in a group decision-making context.

Social influence in consensus formation was examined using a notion of sociocognitive network. Given the robustness of shared information in determining group decisions, the authors propose the concept of a sociocognitive network that captures the degree of members' knowledge-sharing prior to group interaction. A link connecting a given pair of members represents the amount of information that the pair shares before interaction. As in a regular social network, a member's status can be defined by the centrality in the network; the more information a member shares with others, the more cognitively central the member is in the group. The authors hypothesized that a cognitively central member would acquire pivotal power in a group and exert more influence on consensus than would peripheral members, independently of the member's preference majority or minority status. The results of two studies supported these predictions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Empirical prediction method of intrinsic light scattering loss of transparent amorphous polymers

We studied simple empirical equations to estimate the values of intrinsic light scattering loss α_R of various polymers applicable for plastic optical fibers, especially for aromatic amorphous polymers. The α_R is divided into two losses, that is, α^iso and α^aniso. Here, α^iso means the isotropic scattering loss; α^aniso, the anisotropic scattering loss. The α^iso is mainly a function of refractive index, and the α^aniso is a function of refractive index, density, and the number of benzene rings in the polymer repeating unit. Therefore, when the polymer density and the structure of its repeating unit are known, the values of α_R can be estimated. We derived new empirical equations for predicting the values of each intrinsic light scattering loss, α^iso and α^aniso. The estimated values were approximately equal to the experimental ones. The values of α_R of aromatic amorphous polymers were not so large inherently, and they were a few hundred decibels per kilometer at the highest. © 1992 John Wiley & Sons, Inc.     

The effect of tensile stress upon the resistivity of a polymeric carbon

The room temperature resistivity of a polymeric carbon made from a phenolic resin was measured as functions of heat treatment temperature and tensile stress. The elastic modulus (at room temperature) was also measured as a function of heat treatment temperature. Analysis of the results indicates a positive piezoresistance effect which decreases to zero at high heat treatment temperatures. The effect is related to the models for the physical and electronic structures of polymeric carbons proposed previously, and is found to be consistent with these models.     

Topology optimization of piezoelectric smart structures for minimum energy consumption under active control

This paper investigates topology optimization of the electrode coverage over piezoelectric patches attached to a thin-shell structure to reduce the energy consumption of active vibration control under harmonic excitations. The constant gain velocity feedback control method is employed, and the structural frequency response under control is analyzed with the finite element method. In the mathematical formulation of the proposed topology optimization model, the total energy consumption of the control system is taken as the objective function, and a constraint of the maximum allowable dynamic compliance is considered. The pseudo-densities indicating the distribution of surface electrode coverage over the piezoelectric layers are chosen as the design variables, and a penalized model is employed to relate the active damping effect and these design variables. The sensitivity analysis scheme of the control energy consumption with respect to the design variables is derived with the adjoint-variable method. Numerical examples demonstrate that the proposed optimization model is able to generate optimal topologies of electrode coverage over the piezoelectric layers, which can effectively reduce the energy consumption of the control system. Also, numerical comparisons with a minimum-volume optimization model show the advantage of the proposed method with respect to energy consumption. The proposed method may provide useful guidance to the layout optimization of piezoelectric smart structures where the energy supply is limited, such as miniature vibration control systems.     

Reconstruction of renal glomerular tissue using collagen vitrigel scaffold

The construction of renal glomerular tissue has provided an important tool not only for the understanding of renal physiology and pathology in blood ultrafiltration and cell dysfunction, but also in the application of tissue engineering to glomeruli regeneration and nephritic therapy. In this study, a novel method to reconstruct glomerular tissue combining cultured cells on a collagen vitrigel scaffold is described. The method consists of two newly developed techniques, one to isolate glomerular epithelial and mesangial cells rapidly from kidney, which facilitates the prolongation of cell population doublings and allows a long-term cell culture without losing cellular features, and another to prepare a stable and thin transparent collagen gel membrane termed collagen vitrigel that can facilitate three-dimensional cultures for reconstructing an epithelial-mesenchymal model. By combining the two methods, we cocultured glomerular epithelial and mesangial cells on both surfaces of the collagen vitrigel by the manipulation of two-dimensional cultures, resulting in the successful reconstruction of a three-dimensional glomerular organoid. The coculture results showed that the collagen vitrigel maintains cell growth and cell viability for more than 1 month, and surprisingly, the epithelial layer demonstrated polarity formation, which usually appears in in vivo normal epithelial cells existing at the glomerular basement membrane, but seldom appears in epithelial cells cultured in vitro. Moreover, the coculture results showed that fibronectin, an extracellular matrix component, and integrin beta1, a receptor of fibronectin, were detected in high amounts on both cells, suggesting our collagen vitrigel can provide a suitable environment for cell-cell interactions that stabilize the cell structure and may contribute to the polarity formation of epithelial cells.     

Highly selective supported Pd catalysts for steam reforming of methanol

Steam reforming of methanol, CH₃OH + H₂O 3H₂ + CO₂, was carried out over various Pd catalysts (Pd/SiO₂, Pd/Al₂O₃, Pd/La₂O₃, Pd/Nb₂O₅, Pd/Nd₂O₃, Pd/ZrO₂, Pd/ZnO and unsupported Pd). The reaction was greatly affected by the kind of support. The selectivity for the steam reforming was anomalously high over Pd/ZnO catalysts.     

New Supported Pd and Pt Alloy Catalysts for Steam Reforming and Dehydrogenation of Methanol

The catalytic performances of supported Group 810 metal (Co, Ni, Ru, Pd, Ir and Pt) catalysts for steam reforming of methanol, CH₃OH + H₂O CO₂ + 3H₂, and dehydrogenation of methanol to methyl formate, 2CH₃ OH HCOOCH₃ + 2H₂, are markedly affected by the kinds of supports as well as the metals used. The selectivity for steam reforming and the formation of methyl formate was markedly improved when Pd or Pt were supported on ZnO, In₂O₃ and Ga₂O₃. The combined results of temperature-programmed reduction, XRD, XPS and AES revealed that Pd-Zn, Pd-In, Pd-Ga, Pt-Zn, Pt-In and Pt-Ga alloys were formed upon reduction. Over the catalysts having an alloy phase, the reactions proceeded selectively, whereas over the catalysts having a metallic phase, methanol was decomposed to carbon monoxide and hydrogen predominantly. It was shown that the reactivity of formaldehyde intermediate over the Pd and Pt alloys was markedly different from that over metallic Pd and Pt. Over Pd and Pt alloys, aldehyde species were stabilized and transformed into carbon dioxide and hydrogen or methyl formate by nucleophilic addition of water or methanol, respectively. By contrast, over metallic Pd and Pt, aldehyde species were rapidly decarbonylated to carbon monoxide and hydrogen.     

Cycle analysis using exhaust heat of SOFC and turbine combined cycle by absorption chiller

The power generating efficiency of solid oxide fuel cell (SOFC) and gas turbine combined cycle is fairly high. However, the exhaust gas temperature of the combined cycle is still high, about 300^°C. Thus, it should be recovered for energy saving, for example, by absorption chiller. The energy demand for refrigeration cooling is recently increasing year by year in Japan. We propose here a cogeneration system by series connection of SOFC, gas turbine and LiBr absorption chiller to convert the exhaust heat to the cooling heat. As a result of cycle analysis of the combined system with 500‐kW‐class SOFC, the bottoming single‐effect absorption chiller can produce a refrigerating capacity of about 120 kW, and the double‐effect absorption chiller can produce a little higher refrigerating capacity of about 130 kW without any additional fuel. But the double‐effect absorption chiller became more expensive and complex than the single‐effect chiller. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(1): 49– 55, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20578