Helimote [6] is an energy harvesting system with a single storage for buffering solar energy Built on a Mica2 mote, Helimote recharges two AA Ni-MH batteries, and it can learn its energy availability and usage via an energy-monitoring component. Jiang et al. [7] designed Prometheus, a hybrid energy storage system for solar energy. Based on Telos mote, Prometheus can be powered by the supercapacitors, called the primary energy buffer, or by the rechargeable Li-ion battery, called the secondary energy buffer. If the primary buffer energy is less than some threshold, the mote falls back to the secondary buffer until the primary one recharges fully again. Similar to Prometheus, AmbiMax [8] uses the hybrid energy storage. However, AmbiMax tracks the maximum power point automatically, without the control of MCU.
Like our system, EverLast [9] is a supercapacitor-driven sensor mote and does not use any battery. EverLast uses a PFM (Pulse Frequency Modulation) controller and a PFM regulator to harvest the solar energy. To track the maximum power point, EverLast integrates a complex charging circuit. Besides outdoor solar energy, vibration, indoor light, thermal and wind energy sources have been studied to drive sensor motes [10,11]. The work in [12] gives a survey abo
Visual inspection has traditionally played a critical role in quality management of the construction process and damage detection in structures subjected to various loadings [1,2]. However, because structures have become increasingly complex (e.g.
, high-rise and irregular designs), visual inspections are becoming increasingly time consuming and labor intensive and suffer from expensive and subjective evaluations; these aspects represent critical problems in the application of this method to real structures. Because visual inspection is restricted to post-event assessments, immediate damage detection and safety evaluations of structures are nearly impossible.For AV-951 these reasons, structural health monitoring (SHM) based on sensor technology has received considerable attention and has successfully replaced traditional visual inspection [3�C6]. The SHM of buildings, which is based on a wired sensor network, was initially conducted for simple civil structures. The development of monitoring systems enabled a real-time response evaluation of a structure.
However, the high installation cost of the cable that connects the sensor to the server and maintenance and management challenges remain unresolved issues.For these reasons, Straser [7] attempted to solve the problems of existing wire-based monitoring systems by proving the effectiveness of the wireless sensor network (WSN) in an actual building. The WSN system (WSNS) significantly decreased the installation cost of a wired sensor network, and thus, the high-nodal density of sensor networsks was realized, which enabled local damage detection.