3,056 research outputs found
Hybrid perturbation/Bubnov-Galerkin technique for nonlinear thermal analysis
A two step hybrid analysis technique to predict the nonlinear steady state temperature distribution in structures and solids is presented. The technique is based on the regular perturbation expansion and the classical Bubnov-Galerkin approximation. The functions are obtained by using the regular perturbation method. These functions are selected as coordinate functions and the classical Bubnov-Galerkin technique is used to compute their amplitudes. The potential of the proposed hybrid technique for the solution of nonlinear thermal problems is discussed. The effectiveness of this technique is demonstrated by the effects of conduction, convection, and radiation modes of heat transfer. It is indicated that the hybrid technique overcomes the two major drawbacks of the classical techniques: (1) the requirement of using a small parameter in the regular perturbation method; and (2) the arbitrariness in the choice of the coordinate functions in the Bubnov-Galerkin technique. The proposed technique extends the range of applicability of the regular perturbation method and enhances the effectiveness of the Bubnov-Galerkin technique
Confocal microscopic image sequence compression using vector quantization and 3D pyramids
The 3D pyramid compressor project at the University of Glasgow has developed a compressor for images obtained from CLSM device. The proposed method using a combination of image pyramid coder and vector quantization techniques has good performance at compressing confocal volume image data. An experiment was conducted on several kinds of CLSM data using the presented compressor compared to other well-known volume data compressors, such as MPEG-1. The results showed that the 3D pyramid compressor gave higher subjective and objective image quality of reconstructed images at the same compression ratio and presented more acceptable results when applying image processing filters on reconstructed images
The significance of subsurface chlorophyll, nitrite and ammonium maxima in relation to nitrogen for phytoplankton growth in stratified waters of the Gulf of Maine
Data on the distributions in summer of phytoplankton and inorganic nutrients in the Gulf of Maine and across Georges Bank are presented. The chlorophyll maximum represents a phytoplankton biomass maximum and occurs at a depth where both light and nitrate availability allow net growth of the population. The dominant species were generally flagellates and included the toxic dinoflagellate, Gonyaulax tamarensis var. excavata, at some stations. The ammonium and nitrite profiles suggest that nitrification is occurring at the base of the pycnocline below the chlorophyll maximum, and this may be an important source of nitrate during the summer months. The highest levels of nitrite and ammonium were found over the slopes of Georges Bank
‘‘There’s so much more to it than what I initially thought’’: Stepping into researchers’ shoes with a class activity in a first year psychology survey course
In psychology, it is widely agreed that research methods, although central to the discipline, are particularly challenging to learn and teach, particularly at introductory level. This pilot study explored the potential of embedding a student-conducted research activity in a one-semester undergraduate Introduction to Psychology survey course, with the aims of (a) engaging students with the topic of research methods; (b) developing students’ comprehension and application of research methods concepts; and (c) building students’ ability to link research with theory. The research activity explored shoe ownership, examining gender differences and relationships with age, and linking to theories of gender difference and of consumer identity. The process of carrying out the research and reflecting on it created a contextualized, active learning environment in which students themselves raised many issues that research methods lectures seek to cover. Students also wrote richer assignments than standard first year mid-term essay
A gray-box model for a probabilistic estimate of regional ground magnetic perturbations: Enhancing the NOAA operational Geospace model with machine learning
We present a novel algorithm that predicts the probability that the time
derivative of the horizontal component of the ground magnetic field
exceeds a specified threshold at a given location. This quantity provides
important information that is physically relevant to Geomagnetically Induced
Currents (GIC), which are electric currents { associated to} sudden changes in
the Earth's magnetic field due to Space Weather events. The model follows a
'gray-box' approach by combining the output of a physics-based model with
machine learning. Specifically, we combine the University of Michigan's
Geospace model that is operational at the NOAA Space Weather Prediction Center,
with a boosted ensemble of classification trees. We discuss the problem of
re-calibrating the output of the decision tree to obtain reliable
probabilities. The performance of the model is assessed by typical metrics for
probabilistic forecasts: Probability of Detection and False Detection, True
Skill Statistic, Heidke Skill Score, and Receiver Operating Characteristic
curve. We show that the ML enhanced algorithm consistently improves all the
metrics considered.Comment: under revie
Low-energy elastic electron scattering by acetylene
We report measurements and first-principles calculations of the differential cross sections for elastic scattering of low-energy electrons by acetylene, C_2H_2, at collision energies from 1 to 100 eV, with an emphasis on energies near and below that of the π* shape resonance. The measurements cover angles from 5° to 130°. We compare our results to previous experimental and theoretical values
C60 1,1,2,2-tetrachloroethylene tetrasolvate
In the title complex, C60·4C2Cl4, the C60 molecule is located on an inversion centre and there are two tetrachloroethylene (TCE) molecules in the asymmetric unit. Both TCE molecules show positional disorder, with occupancy ratios of 0.75:0.25 and 0.56:0.44. Four fullerene C atoms form short contacts [3.208 (17) and 3.223 (17) Å] with the centres of the TCE double bonds, indicating that C60–solvent interactions are largely π–π in nature
Simulation Approach for Timing Analysis of Genetic Logic Circuits
Constructing
genetic logic circuits is an application of synthetic
biology in which parts of the DNA of a living cell are engineered
to perform a dedicated Boolean function triggered by an appropriate
concentration of certain proteins or by different genetic components.
These logic circuits work in a manner similar to electronic logic
circuits, but they are much more stochastic and hence much harder
to characterize. In this article, we introduce an approach to analyze
the threshold value and timing of genetic logic circuits. We show
how this approach can be used to analyze the timing behavior of single
and cascaded genetic logic circuits. We further analyze the timing
sensitivity of circuits by varying the degradation rates and concentrations.
Our approach can be used not only to characterize the timing behavior
but also to analyze the timing constraints of cascaded genetic logic
circuits, a capability that we believe will be important for design
automation in synthetic biology
- …