A study of energy scavenging strategy in a tapping tree power

Energy harvesting has become one of the newest research attraction for both academic and industry fields. The energy is captured from external sources (thermal, wind, solar, vibration and hydrodynamic) and the energy source for energy harvesters is present as ambient background and it is free. The energy can be harvested in term of sensors or direct applying which depends on the source applied to. One of the energy harvesting topologies is from tapping tree which is new topology that can be applied direct to the tree by inserting electrode into the tree while the other is into the surrounding soil. This project introduces a method for the energy to be harvested from a tree, where the voltage obtained is conducted to three types of trees (Palm, Agrawood, and Palm Oil). Both type of electrodes and pH value of the surrounding soil are considered in order to get maximum voltage. Furthermore, the depth of the electrode inserted and the height from the surrounding soil play a role for voltage variation. The maximum voltage can be obtained is from (Al Alloy with Al) electrodes, at neutral pH, dry mositure and in Palm Oil Tree which is almost 0.8V - 1.2V. However, at such small energy from tree source, converter is required to increase the power. Boost converter contains of BQ25504 IC is applied to increase the voltage from small input to 3V - 4V. As well as, buck converter with TPS62231 IC is introduced for the output voltage of the boost converter and can be applied for small voltage as 1.8V. Simulation using Tina software simulate the converters mentioned and get better results for the energy harvested with battery charging system and energy storage. Field test is conducted with the selected converter to insure the power observed from the plant. In addition, this work has been taken to enhance the growth of energy harvesting from small sources and to go further for nature sources that has a high impact for low applications in the future

Optimal Prefix Codes with Fewer Distinct Codeword Lengths are Faster to Construct

A new method for constructing minimum-redundancy binary prefix codes is described. Our method does not explicitly build a Huffman tree; instead it uses a property of optimal prefix codes to compute the codeword lengths corresponding to the input weights. Let $n$ be the number of weights and $k$ be the number of distinct codeword lengths as produced by the algorithm for the optimum codes. The running time of our algorithm is $O(k \cdot n)$. Following our previous work in \cite{be}, no algorithm can possibly construct optimal prefix codes in $o(k \cdot n)$ time. When the given weights are presorted our algorithm performs $O(9^k \cdot \log^{2k}{n})$ comparisons.Comment: 23 pages, a preliminary version appeared in STACS 200

Sub-metre spatial resolution temperature compensated distributed strain sensor

We propose and demonstrate a scheme which utilizes the temperature dependence of spontaneous Raman scattering to provide temperature compensation for a sub-metre spatial resolution Brillouin frequency based strain sensor. Temperature compensated strain sensor measurements have been demonstrated with a strain resolution of 94µ.ε and a spatial resolution of 10cms. This paper describes the combination of Brillouin frequency based BOCDA technique [1] with an independent measurement of temperature, based on the determination of the intensity of the anti-Stokes Raman scattering (R-OTDR) with very much higher spatial resolution than previously reported [2], in order to produce a fully temperature compensated strain sensor with high spatial resolution