Chih-Hsuan Chen

A study of the structure of G-P zones in Ti-rich TiNi shape memory melt-spun ribbons

A hybrid structure composed of ordered C11b Ti2Ni and Ti5Ni3 substructures for the G-P zones precipitated in Ti-rich Ti–Ni shape memory ribbons is proposed to explain the appearance of extra diffuse scattering streaks in transmission electron microscopy observations. The point defects of Ni vacancies and Ti antisites, resulting in the lattice fluctuant displacement, also cause the incommensurate extra diffuse scattering streaks.

Design and Implementation of a Wireless Sensor Network for Smart Living Spaces

After the evolution over the last decade, the wireless sensor network (WSN) technology is successfully adopted into applications such as remote medical care, health monitoring, smart houses and vehicle electron fields. Rapid advancement of many technologies such as IC design, sensor technology, circuits/firmware development, communication protocol design, and network programming was incorporated into modern WSN technology and was recognized as one of the most important emerging technology. In order to further expand the application arena of WSN technology, a team of researchers from different fields, funded by Nation Science Council (NSC), Taiwan are now working together to push the technology forward and focus on a low cost WSN platform which may enable the application of WSN technology in general households or say smart living space. The first objective of the group was to establish a new wireless sensor network development platform with very low cost sensor nodes and also free software. With the new platform, the deployment cost of WSN technology will be minimized, and thus the application of the technology on different new areas can be explored especially the application of smart living space. This paper will detail the Super Node and Simple Node low-cost sensor code designed in this project, and also the software development platform, packet routing, data collection will be further introduced. The modulus design concept of both a Simple Node and Super Node for further integration with other application circuits in order to facilitate the prototype design for different applications will also be detailed.

Switching characteristics of (Bi1/2Na1/2)TiO3-BaTiO3-(Bi1/2K1/2)TiO3 lead-free ferroelectric ceramics

The polarization switching characteristics of lead-free a(Bi1/2Na1/2)TiO3−bBaTiO3−c(Bi1/2K1/2)TiO3 (abbreviated as BNBK 100a/100b/100c) ferroelectric ceramics are investigated. This is achieved through examining their polarization and strain hystereses inside and outside the morphotropic phase boundary (MPB). The total induced electrostrain (&egr;33,total) and apparent piezoelectric charge coefficient (d33) first increase dramatically and then decrease gradually as the BNBK composition moves from the tetragonal phase to the MPB and then to the rhombohedral phase. The measured polarization hystereses indicate that the BNBK compositions situated near the rhombohedral side of the MPB typically possess higher coercive field (Ec) and remanent polarization (Pr), while the compositions situated near the tetragonal side of the MPB possess higher apparent permittivity. Adverse effects on the ferroelectric properties are observed when BNBK is doped with donor dopants such as La and Nb. On the contrary, intricate hysteresis behaviors are observed when acceptor dopant Mn is introduced into BNBK. Under an alternating electric field of ±5.0 MVm-1, BNBK 85.4/2.6/12, a composition well within the MPB, exhibits an &egr;33,total of ~0.14%, an apparent d33 of 295 pCN-1, an Ec of 2.5 MVm-1 and a Pr of 22.5 &mgr;Ccm-2. These notable ferroelectric property values suggest a candidate material for lead-free actuator applications. The present study provides a systematic set of hysteresis measurements which can be used to characterize the switching behaviors of BNBK-based lead-free ferroelectrics.