Cellulose nanofiber/nanodiamond composite films: Thermal conductivity enhancement achieved by a tuned nanostructure

Thermally conductive and electrically insulating composite materials are required for thermal management in advanced electronic industry. The present work aimed at creating a composite film of cellulose nanofiber (CNF) and nanodiamond (ND) with superior thermal conductivity. The thermal conductivity of the prepared nanocomposite film was ～2.7?Wm^?1?K^?1, which corresponds to triple of usual CNF/ND composites with similar composition. The distinct thermal conductivity is attributed to a unique nanostructure we made out in the nanocomposite film. The nanostructure can be characterized by CNF fibrils which are densely covered with ND particles.     

Distributed Hybrid Controllers for Multi‐Agent Mass Games By A Variable Number of Player Agents

This paper considers a problem of finding distributed controllers for the multi‐agent mass games, that is, to let agents organize themselves into a formation displaying a given grayscale image. As a solution to this problem, we propose distributed hybrid controllers. The key idea is to combine a coverage control method and halftone image processing, i.e., to combine techniques from the control theory and the image processing. The performance of the proposed controllers is demonstrated by numerical experiments with standard images.© 2014 Chinese Automatic Control Society and Wiley Publishing Asia Pty Ltd     

Stabilization of Hamiltonian systems with nonholonomic constraints based on time-varying generalized canonical transformations

This paper is concerned with the stabilization of nonholonomic systems in port-controlled Hamiltonian formulae based on time-varying generalized canonical transformations. A special class of time-varying generalized canonical transformations are introduced which modify the kinetic energy of the original system without changing the generalized Hamiltonian structure with passivity. Utilizing these transformations, time-varying asymptotically stabilizing controllers for the nonholonomic Hamiltonian systems are derived. Since the proposed method is a natural generalization of passivity based control for conventional holonomic systems, it is expected that the tools developed for conventional systems will be applicable to nonholonomic systems based on the proposed method.     

Preparation and characterization of silylated graphite oxide

Graphite oxide was silylated by various alkylchlorosilanes in the presence of butylamine and toluene, and new intercalation compounds were obtained. The silylating reagents with two or three chlorine atoms at silicon in them reacted with graphite oxide, while no reaction occurred when silylating reagents with only one chlorine atom was used. The silylating reagent mainly reacted with hydroxyl group of graphite oxide, forming Si-O bonding. The role of butylamine was not only exfoliating graphite oxide layer but also scavenging HCl molecule which caused the decomposition of silylated graphite oxide. The silicon content was almost constant ≈0.6 mol/graphite oxide for the samples silylated by alkyltrichlorosilane with shorter alkyl chain lengths. It increased with the increase of alkyl chain length and reached 1.7 mol/graphite oxide. The higher silicon content could be ascribed to further silylation on hydroxyl groups formed at silicon atoms of silylating reagent bonded to graphite oxide, bridging two silylating reagents.     

The effect of alkyl chain length on the structure of pillared carbons prepared by the silylation of graphite oxide with alkyltrichlorosilanes

Pillared carbon was obtained from graphite oxide silylated with alkyltrichlorosilanes with various alkyl chain lengths. The interlayer spacings of silylated graphite oxides became maximal when 1.1-1.5 molecules of bound silyl groups were attached per C₈ graphite oxide unit. Pillared carbon with an interlayer spacing of 1.27 nm was obtained only when graphite oxide silylated with methyltrichlorosilane was heated under vacuum above 300 °C. Infrared absorption measurements indicated that the pillars possessed the ladder type silsesquioxane structure. The adjacent graphite oxide layers were connected to each other even before pyrolysis, judging from the observation that n-hexadecylamine was not intercalated. The formation of a ladder type pillar was completed after the oxygen-containing groups were removed from the graphite oxide layers. When the alkyl chain length was longer, the connection of adjacent layers became difficult and pillared carbons were not formed. The surface area of the pillared carbon was very small because the distance between pillars was too small for nitrogen molecules to pass, but it was estimated based on the composition of the pillared carbon.     

Optimal dynamic quantizers for discrete-valued input control

This paper discusses an optimal design problem of dynamic quantizers for a class of discrete-valued input systems, i.e., linear time-invariant systems actuated by discrete-valued input signals. The quantizers considered here are in the form of a linear difference equation, for which we find a quantizer such that the system composed of a given linear plant and the quantizer is an optimal approximation of the given linear plant in the sense of the input-output relation. First, we derive a closed form expression for the performance of a class of dynamic quantizers. Next, based on the performance analysis, an optimal dynamic quantizer and its performance are provided. This result further shows that even for such discrete-valued input systems, a controller can be easily designed by the existing tools for the linear system design such as robust control theory. Finally, the relation among the optimal dynamic quantizer and two other quantizers, i.e., the receding horizon quantizer and the ΔΣ modulator, is discussed.     

Renewable resource based biocomposites from natural fiber and polyhydroxybutyrate-co-valerate (PHBV) bioplastic

Renewable resource based green biocomposites were prepared using a bacterial polyester i.e., poly(hydroxybutyrate-co-valerate) (PHBV) and natural bamboo fiber. Fabrication of the biocomposites was carried out by injection molding following extrusion compounding of PHBV and bamboo fiber with 30 or 40 wt.% fiber. The mechanical, thermo-mechanical and morphological properties of the biocomposites were evaluated. Little variation in the thermo-mechanical and impact properties was observed when the fiber content was varied. The tensile modulus of biocomposites at 40 wt.% fiber improved by 175% as compared to that of neat PHBV. The theoretical tensile modulus of the biocomposites was calculated using Christensen’s equations and compared with the experimental results. It was found to be in near approximation to the experimental data. The storage modulus was affected slightly by the variation of fiber content from 30 to 40 wt.% in biocomposites. The heat deflection temperature of PHBV increased by 9 °C at 40 wt.% of fiber reinforcement. Morphological aspects and thermal stability were studied using scanning electron microscopy and thermo-gravimetric analysis, respectively. In addition, a comparative analysis of bamboo fiber–PHBV with wood fiber–PHBV biocomposites was performed. Statistical analysis of both biocomposites was carried out by performing a two-way ANOVA on their tensile and flexural moduli in order to evaluate the effect of fiber type and content in the PHBV matrix.     

Industrial agglomeration and the regional scientific explanation of perceived environmental injustice

This article evaluates the impact on an environmental justice analysis of explicitly controlling for forces of agglomeration. Many environmental justice studies have examined whether polluting facilities are disproportionately concentrated near certain types of people, such as minorities. No studies so far have explicitly included a proxy for agglomeration, and relatively few use appropriate spatial analytic techniques. Our analysis does both, and in doing so demonstrates that agglomeration is an important factor explaining locations of certain environmentally regulated facilities. Not using fundamental regional science concepts and appropriate spatial analytic techniques can lead to flawed analyses and conclusions.     

Wavelength channel data rewrite using saturated SOA modulator for WDM networks with centralized light sources

This paper describes a method for realizing the efficient utilization of wavelength resources in wavelength-division multiplexing networks with centralized light sources. Using a deeply saturated semiconductor optical amplifier (SOA) modulator located in a remote node (RN), we erase the data on a downstream signal with a low extinction ratio and modulate it with new data to generate an upstream signal. Thus, we use only one wavelength for bidirectional transmission between a center node and an RN, without placing lasers at the RN. In this paper, we analyze the data suppression characteristic of the SOA using a large signal model. We also estimate the bit error rate degradation in the presence of an unsuppressed downstream bit pattern in an upstream signal. We then report experimental results that confirm the basic characteristics of the wavelength channel data rewriter, which we constructed using a linear amplifier and an SOA. Finally, we provide the results of a data transmission experiment that we undertook using the data rewriter.