Disruptive innovation for social change: how technology innovation can be best managed in social context

This paper describes a research approach based on the Actor-Network Theory (ANT) to interpret and understand the Korea’s strategy for the development of the ubiquitous city (u-city). Analyzing empirical materials from u-city development, this study traces and unpacks the interaction occurring around the u-city innovation and also identifies patterns of innovation, concentrating on negotiation and translation implementation. The findings imply that Korean approach has marginalized key issues relating to the development potential inherent in the combination of knowledge and technology and thus conflicts with broader development suggestions of participative design. Korean case reveals the essential role of participatory design in u-city development. U-city as a public utility should draw users’ perspectives, its design should be heavily grounded in users’ needs, and its design decisions should be based on a community consensus.     

Wear behavior of self-lubricating Fe-Cr-C-Mn-Cu alloys: Smearing effect of second phase particles

Newly developed self-lubricating Fe-Cr-C-Mn-Cu cast composite alloys were investigated to study the role of Cu-rich second phase particles which smear on the wear surface during sliding. The wear resistance of the material was improved with an increasing copper concentration. The improved wear resistance was probably obtained by forming a protective tribofilm, which prevented metal-to-metal contact through smearing of the embedded Cu-rich second phase particles. This formation of protective oxide films during sliding is likely to improve the wear resistance of austenitic Fe-Cr-C-Mn-Cu cast composite alloys.     

Tuning the electronic band structure of PCBM by electron irradiation

Tuning the electronic band structures such as band-edge position and bandgap of organic semiconductors is crucial to maximize the performance of organic photovoltaic devices. We present a simple yet effective electron irradiation approach to tune the band structure of [6, 6]-phenyl-C61-butyric acid methyl ester (PCBM) that is the most widely used organic acceptor material. We have found that the lowest unoccupied molecular orbital (LUMO) level of PCBM up-shifts toward the vacuum energy level, while the highest occupied molecular orbital (HOMO) level down-shifts when PCBM is electron-irradiated. The shift of the HOMO and the LUMO levels increases as the irradiated electron fluence increases. Accordingly, the band-edge position and the bandgap of PCBM can be controlled by adjusting the electron fluence. Characterization of electron-irradiated PCBM reveals that the variation of the band structure is attributed to the molecular structural change of PCBM by electron irradiation.     

Discrete derivative method for adaptive notch filter-based frequency estimators

International Journal of Control, Automation and Systems - This paper presents a new discrete derivative method for adaptive notch filter (ANF)-based frequency estimators. ANF-based frequency...     

Investigation on the valence state of Te ions in the Bi6Ti5TeO22 thin film using X-ray photoelectron spectroscopy

Bi₆Ti₅TeO₂₂ (BTT) thin films were grown on a Pt/Ti/SiO₂/Si(1 0 0) substrate under various conditions and the valence state of the Te ion was investigated. For the BTT films grown at 300 °C, most of the Te ions existed as Te⁴⁺ ions. However, for the 10 mol% Mn-added BTT films grown at 300 °C, Te⁶⁺ ions were found even in the film grown under low oxygen partial pressure (OPP) and their number increased with increasing OPP. This increase was attributed to the presence of Mn²⁺ ions, which assisted the transition of Te⁴⁺ ions to Te⁶⁺ ions in order to maintain the charge balance of the Ti⁴⁺ sites. Furthermore, in the films grown at 300 °C under a high OPP of 80.0 Pa and subsequently annealed at 600 °C under a high oxygen pressure of 101 kPa, most of the Te ions existed as Te⁶⁺ ions. However, for the film grown at 300 °C under low OPP, even though the film was annealed under a high oxygen pressure of 101 kPa, only a few of Te⁶⁺ ions were formed, whereas most of Te ions remained as the Te⁴⁺ ions.     

Application of electro-mechanical impedance sensing technique for online monitoring of strength development in concrete using smart PZT patches

Electro-mechanical impedance (EMI) sensing technique utilizing smart piezoelectric materials has emerged as a potential tool for the implementation of an online monitoring system for structural health monitoring. Many nondestructive methods for strength gain monitoring seem to have limited capabilities in monitoring of the strength gain in a continuous manner. In this study, the feasibility of the EMI sensing technique for the online strength gain monitoring of early-age concrete is investigated. The experimental study is conducted on the piezoelectric patch instrumented concrete specimen. It is found that the EMI signature is very sensitive to the strength gain in early age concrete.     

Upper bound on the capacity of cognitive radio without cooperation

We derive an upper bound on the capacity of cognitive radio using the interference temperature concept. We do not assume any cooperation between the primary and the secondary user. First, assuming all four links associated with the primary/secondary transmitter/receiver experience Rayleigh fading, the capacity is achieved via the water-filling power allocation strategy, subject to an average secondary to primary interference to signal ratio (ISR) constraint and a peak ISR constraint. Second, we extend our result to the case with path loss as well as channel fading to reflect the geometric relations between link pairs and network size. Finally, we numerically show that for K_P primary receivers which are opportunistically scheduled, the capacity of cognitive radio asymptotically grows as logloglogK_P.     

Design and modeling of a novel 3-DOF precision micro-stage

Based on the well-known tripod parallel configuration, this paper presents a novel 3-DOF micro-stage for active micro-vibration control, which ensures compactness, lightness and simplicity of its structure. A novel strut utilizing the piezoelectric transducer and flexure hinge mechanism is proposed as an actuation unit not only to reduce the overall size but also to increase the horizontal stiffness of the micro-stage. Equipped with the novel actuation unit, a symmetric micro-stage is constructed in order to minimize the dynamic couplings among three axes. Through the physics-based modeling based on the first principles, a parametric model for the proposed micro-stage is established, which precisely predicts the experimentally determined empirical model over the frequency range of interest. The scalability of the developed model is subsequently examined and validated through the extensive experiments while varying the mass of payload.     

Electrospinning of poly(dimethyl siloxane) by sol–gel method

Crosslinked poly(dimethyl siloxane) (PDMS) fibers were fabricated by electrospinning in combination with a sol–gel process followed by heat treatment. Before and after heat treatment, the changes in the chemical and thermal properties of the electrospun PDMS fibers were examined by differential scanning calorimetry (DSC), equilibrium swelling tests, and contact angle measurements. There was no significant change in morphology and average diameter of the as‐spun PDMS fibers after heat treatment. The tensile properties of the as‐spun PDMS fibers mat increased with increasing heat treatment temperature. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009