Thermal Excitation and Piezoresistive Detection of Cantilever In-Plane Resonance Modes for Sensing Applications

Thermally excited and piezoresistively detected bulk-micromachined cantilevers vibrating in their in-plane flexural resonance mode are presented. By shearing the surrounding fluid rather than exerting normal stress on it, the in-plane mode cantilevers exhibit reduced added fluid mass effects and improved quality factors in a fluid environment. In this letter, different cantilever geometries with in-plane resonance frequencies from 50 kHz to 2.2 MHz have been tested, with quality factors as high as 4200 in air and 67 in water

Collaborative interactions among preschool children in a computer environment

This paper reports on a study which investigated the collaborative interaction patterns exhibited by five-year-old pre-primary children in an educational computer environment. A case study method was used in one pre-primary centre in a metropolitan city, to examine the patterns of collaborative interaction among young children whilst engaged, in dyads, with the computer within a naturalistic classroom environment. A total of 243 interactions were identified and classified into 16 interaction patterns. Factors facilitating and inhibiting collaborative interaction were identified as: developmental appropriateness of the software; preexisting computer competency and attitude towards computer; mutual friendship between collaborators; children's social goals; appropriate structure of enjoyable learning environment; mutual understanding of the turn-taking system; and non-isolated physical settings. In effect, this study shows that early childhood educators will be in a better position to integrate the computer into their classroom and to promote positive prosocial interaction among children whilst engaged at the computer, if it were to be afforded the same status as other traditional early childhood learning materials and activities

Chemical composition of Cinnamomum species collected in Sarawak

Cinnamomum species (Lauraceae) are well known for their fragrance and medicinal value. The essential oils of three Cinnamomum species (C. macrophyllum, C. crassinervium and C. griffithii) collected in Sarawak were obtained by hydrodistillation and analyzed by gas chromatograpy mass spectrometry (GC-MS). The analysis of the oils showed that most of the essential oils were mainly phenylpropanoids and monoterpenes with a small amount of sesquiterpenes present. Both C. griffithii and C. crassinervium contained similar major chemical composition such as β-linalool, methyl cinnamate and eugenol methyl ether. No presence of methyl cinnamate and β-linalool were found in the oil of C. macrophyllum. m-Eugenol was prominent in the leaf oil of C. macrophyllum, while cinnamaldehyde was found mainly in the bark oil of C. macrophyllum. High percentage of camphor was identified in the bark and root oil of C. macrophyllum, compared to small amount of camphor found in the both root oil of C. griffithii and C. crassinervium

Geometrical Optimization of Resonant Cantilevers Vibrating in In-Plane Bending Modes

The influence of the beam geometry on the quality factor and resonance frequency of resonant silicon cantilever beams vibrating in their fundamental in-plane flexural mode has been investigated in air and water. Compared to cantilevers vibrating in their out-of-plane flexural mode, utilizing the in plane mode results in reduced damping and reduced mass loading by the surrounding fluid. Quality factors as high as 4,300 in air and 67 in water have been measured for cantilevers with a 12 μm thick silicon layer. This is in comparison to Q factors up to 1,500 in air and up to 20 in water for cantilevers vibrating in their fundamental out-of-plane bending mode. Based on the experimental data, design guidelines are established for beam dimensions that ensure maximal Q-factors and minimal mass loading by the surrounding fluid