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Piezoresistive Effect in Plasma-Doping of Graphene Sheet for High-Performance Flexible Pressure Sensing Application

150 150 MIMOS Berhad

Authors:

Huang Nay Ming, Saadah Abdul Rahman, Khairul Anuar and Ishal Abdul Aziz

 

Abstract

This paper presents a straightforward plasma treatment modification of graphene with an enhanced piezoresistive effect for the realization of a high-performance pressure sensor. The changes in the graphene in terms of its morphology, structure, chemical composition, and electrical properties after the NH3/Ar plasma treatment were investigated in detail. Through a sufficient plasma treatment condition, our studies demonstrated that plasma-treated graphene sheet exhibits a significant increase in sensitivity by one order of magnitude compared to that of the unmodified graphene sheet. The plasma-doping introduced nitrogen (N) atoms inside the graphene structure and was found to play a significant role in enhancing the pressure sensing performance due to the tunneling behavior from the localized defects. The high sensitivity and good robustness demonstrated by the plasma-treated graphene sensor suggest a promising route for simple, low-cost, and ultrahigh resolution flexible sensors.

 

Source:

ACS Applied Materials & Interfaces

Energy-Efficient Power Allocation for Distributed Antenna Systems with Proportional Fairness

150 150 MIMOS Berhad

Authors:

Mau-Luen Tham, Member, IEEE, Su Fong Chien, Derek William Holtby and Shavkat Alimov

 

Abstract:

In this paper, we propose an energy-efficient power allocation scheme for the downlink multiuser distributed antenna systems (DAS). The objective is to maximize the energy efficiency (EE) under the constraints on per-antenna transmitpower and proportional data rates among users. Since EE function is typically defined in fractional form, it is computationally complex to optimize the EE directly. We first convert the nonlinear fractional problem into an equivalent but better tractable problem, based on which we derive an iterative algorithm to obtain the global optimum of the considered problem. On top of being optimal, the solution is also lightweight since only a single-variable nonlinear equation needs to be solved. Furthermore, we can flexibly switch toanother mode of operation which delivers relatively higher spectral efficiency (SE) at the expense of losing EE. Numerical simulations and complexity analysis validate that the proposed scheme achieves much higher SE and EE performance with strictersatisfaction of the proportional rate constraints and lower complexity, compared to the state-of-the-art schemein literature.

 

Source:

IEEE Transactions on Green Communications and Networking

A Textual Feedback Tool for Empowering Participants in Usability and UX Evaluations

150 150 MIMOS Berhad

Authors:

Ashok Sivaji, Søren Feodor Nielsen and Torkil Clemmensen

 

Abstract:

The usability movement has historically always sought to empower end-users of computers so that theyunderstand what is happening and can control the outcome. In this article, we develop and evaluate a “TextualFeedback” tool for usability and user experience (UX) evaluation that can be used to empower well-educatedbut low-status users in UX evaluations in countries and contexts with high power distances. The proposed toolcontributes to the Human–Computer Interaction (HCI) community’s pool of localized UX evaluation tools. Weevaluate the tool with 40 users from two socio-economic groups in real-life UX usability evaluations settings inMalaysia. The results indicate that the Textual Feedback tool may help participants to give their thoughts in UXevaluation in high power distance contexts. In particular, the Textual Feedback tool helps high status femalesand low status males express more UX problems than they can with traditional concurrent think aloud (CTA)alone. We found that classic concurrent think aloud UX evaluation works fine in high power contexts, but onlywith the addition of Textual Feedback to mitigate the effects of socio-economic status in certain user groups. We suggest that future research on UX evaluation look more into how to empower certain user groups, such aslow status female users, in UX evaluations done in high power distance contexts.

 

Source:

International Journal of Human-Computer Interaction 2017