Ultralow-power Circuit Techniques for Applications with Microscale Energy
あらゆるモノにセンサを取り付けインターネットに 接続することにより新たな価値を創出する IoT (Internet of things)社会の実現に向けて,様々な技術レ イヤーの研究開発が盛んに行われている.IoT技術の 今後の問題の一つに,モノをインターネットに接続す るための近距離無線センサ端末の電源問題がある.電 池駆動のセンサ端末は電池交換が必要となるからで ある.端末の電源問題を解決する一つの手法として, 我々の身の回りに微小ながら常に存在する熱,光,振 動といったアンビエントエネルギー源を活用するマイ クロ環境発電技術が注目されている [1]. 発電電力がミリワット級の環境発電応用としては, 照明用スイッチに電磁誘導型の発電素子を組込み,無 線で照明の ON/OFF制御を行う無線スイッチ [2]や, 列車の車軸に振動発電素子を組込み,無線で車軸のベ アリングを監視するモニタリングシステム [3] が,既 に実用化されている.我々は,人間の尿で発電する尿
Wireless self-powered plant health-monitoring sensor system
A self-powered plant-health-monitoring sensor powered by a battery that is activated by the sap of a vascular plant has been developed as an application for wireless biosensor networks. The battery consists of a galvanized iron nail inserted into a tree trunk and a stainless-steel electrode planted in the soil nearby. It outputs on the order of 1 μW of power. An intermittent power supply circuit with a divided-power-line structure, which separates the power line of a storage capacitor while it is discharging, makes it possible to charge the capacitor with an input power of around 1 μW and to supply power to a wireless transmitter. To verify the effectiveness of the circuit scheme, a prototype sensor was fabricated and tested on a potted pachira tree. The sap-activated battery acted as a current source (3 μA) with an open voltage of 1 V, and the sensor had a 10-mF storage capacitor. This setup enabled the sensor to transmit a signal about every 40 minutes over a distance of 5 m.
Mechanics of deformable directed surfaces
Abstract The paper develops a simple, yet complete and consistent non-linear dynamic thermo-elastic shell theory based on the concepts of a two-dimensional directed continuum. The constitutive equations are postulated in a general form. Stress-strain relations are derived using the equation of energy balance and the two entropy production inequalities, which are rewritten in a special form. The linear theory is discussed in detail. The structure of the stress-strain relations is presented in the most general form and then specialized to concrete examples, in particular, to the classical shell theory, using their invariance properties with respective to certain symmetry groups. The elastic moduli are determined by demanding the coincidence of the frequency dispersion surfaces obtained using the two-dimensional theory with the lowest foils of the corresponding surfaces resulting from the three-dimensional theory of elasticity.