http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Graphene-Based Composite Protective Coating for Twisted Strings and Its Experimental Evaluation
Sarkar, Sourav,Ishfaque, Asif,Usman, Muhammad,Gaponov, Igor,Kim, Byungki IEEE 2018 IEEE TRANSACTIONS ON NANOTECHNOLOGY Vol. No.
<P>Twisted string actuators (TSAs) have found extensive use in various areas of engineering and in consumer products due to their mechanical simplicity and flexibility. Despite huge future potential of TSAs, reliability of the strings operating in stringent conditions has remained a significant concern. The increased string wear due to friction between the fibers and strands is the main reason of comparatively short lifetime of the strings in TSAs. However, very limited research has been done in this area, thus methods to extend the string lifetime remains an open question. Similarly, despite intensive research efforts on graphene over the past decade, its potential as reinforcement in coating material remains comparatively unexplored. In this paper, we report the preparation and implementation of a unique graphene-based composite coating for TSAs. The graphene sample was analyzed by both structural and chemical characterization procedures before the preparation of the coating material. The coated strings were also analyzed thoroughly using both spectroscopic and microscopic techniques. The experimental studies demonstrated that we could increase lifetime of the newly coated strings by approximately 100 <TEX>$\%$</TEX> in comparison with the coated strings procured commercially. The development of this new graphene-based coating material may usher a favorable outlook in the application of TSAs in future.</P>
Bio-Inspired Rectangular Shaped Piezoelectric MEMS Directional Microphone
Rahaman, Ashiqur,Ishfaque, Asif,Jung, Haeil,Kim, Byungki IEEE 2019 IEEE Sensors Journal Vol. No.
<P>The noise floor of a piezoelectric MEMS directional microphone largely depends on piezoelectric materials and transducer modes. A careful choice of these parameters (piezoelectric materials and transducer modes) can help to significantly improve the difficulties of noise floor. Here, we present a unique diaphragm-based biomimetic MEMS directional microphone having multiple-port sensing schemes. The diaphragm is separated into two wings and supported by two torsional beams, which are hinged to a fixed support as to imitate the unique inter-tympanal feature of the fly <I>Ormia ochracea</I>. In this microphone, the thermal-mechanical noise (Johnson noise) is minimized by adopting aluminium nitride-based piezoelectric sensing. The d<SUB>33</SUB> mode is incorporated with a prime focus on sensitivity enhancement which leads to signal-to-noise ratio improvement. Measured directivity patterns of both wings show a strong agreement with the direction of applied acoustic pressure as expected for an ideal bi-directional microphone. The measured noise floor at 1-kHz frequency and overall A-weighted noise floor across the audio frequency are 31.35 dB SPL and 32.5 dBA, respectively, which are quite less than some notable works on directional microphones. The experimental results verify the uniqueness of this work.</P>