24 research outputs found
A Laterally Vibrating Lithium Niobate MEMS Resonator Array Operating at 500{\deg}C in Air
This paper is the first report of the high-temperature characteristics of a
laterally vibrating piezoelectric lithium niobate (LiNbO) MEMS resonator
array up to 500{\deg}C in air. After a high-temperature burn-in treatment,
device quality factor (Q) is enhanced to 508 and the resonance shifts to a
lower frequency and remains stable up to 500{\deg}C. During subsequent in situ
high-temperature testing, the resonant frequencies of two coupled shear
horizontal (SH0) modes in the array are 87.36 MHz and 87.21 MHz at 25{\deg}C
and 84.56 MHz and 84.39 MHz at 500{\deg}C, correspondingly, representing a -3%
shift in frequency over the temperature range. Upon cooling to room
temperature, the resonant frequency returns to 87.36 MHz, demonstrating
recoverability of device performance. The first- and second-order temperature
coefficient of frequency (TCF) are found to be -95.27 ppm/{\deg}C and 57.5
ppb/{\deg}C for resonant mode A, and -95.43 ppm/{\deg}C and 55.8
ppb/{\deg}C for resonant mode B, respectively. The temperature-dependent
quality factor (Q) and electromechanical coupling coefficient () are
extracted and reported. Device Q decreases to 334 after high-temperature
exposure, while increases to 12.40%. This work supports the use of
piezoelectric LiNbO as a material platform for harsh environment
radio-frequency (RF) resonant sensors (e.g. temperature and infrared)
Self organising maps for visualising and modelling
The paper describes the motivation of SOMs (Self Organising Maps) and how they are generally more accessible due to the wider available modern, more powerful, cost-effective computers. Their advantages compared to Principal Components Analysis and Partial Least Squares are discussed. These allow application to non-linear data, are not so dependent on least squares solutions, normality of errors and less influenced by outliers. In addition there are a wide variety of intuitive methods for visualisation that allow full use of the map space. Modern problems in analytical chemistry include applications to cultural heritage studies, environmental, metabolomic and biological problems result in complex datasets. Methods for visualising maps are described including best matching units, hit histograms, unified distance matrices and component planes. Supervised SOMs for classification including multifactor data and variable selection are discussed as is their use in Quality Control. The paper is illustrated using four case studies, namely the Near Infrared of food, the thermal analysis of polymers, metabolomic analysis of saliva using NMR, and on-line HPLC for pharmaceutical process monitoring
Whole-Community Facilitation Regulates Biodiversity on Patagonian Rocky Shores
Understanding the factors that generate and maintain biodiversity is a central goal in ecology. While positive species interactions (i.e., facilitation) have historically been underemphasized in ecological research, they are increasingly recognized as playing important roles in the evolution and maintenance of biodiversity. Dominant habitat-forming species (foundation species) buffer environmental conditions and can therefore facilitate myriad associated species. Theory predicts that facilitation will be the dominant community-structuring force under harsh environmental conditions, where organisms depend on shelter for survival and predation is diminished. Wind-swept, arid Patagonian rocky shores are one of the most desiccating intertidal rocky shores ever studied, providing an opportunity to test this theory and elucidate the context-dependency of facilitation.Surveys across 2100 km of southern Argentinean coastline and experimental manipulations both supported theoretical predictions, with 43 out of 46 species in the animal assemblage obligated to living within the matrices of mussels for protection from potentially lethal desiccation stress and predators having no detectable impact on diversity.These results provide the first experimental support of long-standing theoretical predictions and reveal that in extreme climates, maintenance of whole-community diversity can be maintained by positive interactions that ameliorate physical stress. These findings have important conservation implications and emphasize that preserving foundation species should be a priority in remediating the biodiversity consequences of global climate change
Epistemological Pluralism: Reorganizing Interdisciplinary Research
Despite progress in interdisciplinary research, difficulties remain. In this paper, we argue that scholars, educators, and practitioners need to critically rethink the ways in which interdisciplinary research and training are conducted. We present epistemological pluralism as an approach for conducting innovative, collaborative research and study. Epistemological pluralism recognizes that, in any given research context, there may be several valuable ways of knowing, and that accommodating this plurality can lead to more successful integrated study. This approach is particularly useful in the study and management of social–ecological systems. Through resilience theory\u27s adaptive cycle, we demonstrate how a focus on epistemological pluralism can facilitate the reorganization of interdisciplinary research and avoid the build-up of significant, but insufficiently integrative, disciplinary-dominated research. Finally, using two case studies—urban ecology and social–ecological research in Alaska—we highlight how interdisciplinary work is impeded when divergent epistemologies are not recognized and valued, and that by incorporating a pluralistic framework, these issues can be better explored, resulting in more integrated understanding