1,133 research outputs found
Some finite solvable groups with non-trivial lattice endomorphisms
The main purpose of this paper is to exhibit a doubly-infinite family of examples which are extensions of a p-group by a pâČ-group, with the action satisfying some conditions of Zappa (1951), arising from his study of dual-standard (meet-distributive) subgroups. The examples show that Zappa's conditions do not bound the nilpotency class (or even the derived length) of the p-group. The key to this work is found in closely related conditions of Hartley (published here for the first time). The examples use some exceptional relationships between primes
Sections of Coxeter Orbihedra
We study sections of high dimensional polytopes whose vertices form the orbit of a Coxeter group, and create âscansâof such polytopes in order to graphically visualise them for educational and public engagement purposes
Failure analysis of thin metal foils
The mechanical response and the failure mode of thin metal foils
under tensile load has been analyzed supplementing the usual test records
with full-field measurements performed by three-dimensional digital image
correlation (3D DIC) techniques. The experiments have been simulated by
finite element models formulated within a non-linear continuum framework.
The study presented in this contribution concerns symmetrically pre-cracked
aluminum samples. The wrinkling of the specimens during the test and the
possible and alternative failure mechanisms are evidenced and discussed
Nested Polytopes with Non-crystallographic Symmetry Induced by Projection
Inspired by the structures of viruses and fullerenes in biology and chemistry, we have recently developed a method to construct nested polyhedra and, more generally, nested polytopes in multi-dimensional geometry with non-crystallographic symmetry. In this paper we review these results, presenting them from a geometrical point of view. Examples and applications in science and design are discussed
Expandohedra: Modeling Structural Transitions of a Viral Capsid
Inspired by natural phenomena and mathematical theory this paper presents the development of a model, based on the dodecahedron, that visualizes the structural transition and expansion of a capsid (viral protein shell)
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Microscale wave breaking and air-water gas transfer
Laboratory results showing that the air-water gas transfer velocity k is correlated with mean square wave slope have been cited as evidence that a wave-related mechanism regulates k at low to moderate wind speeds [JĂ€hne et al., 1987; Bock et al., 1999]. Csanady [1990] has modeled the effect of microscale wave breaking on air-water gas transfer with the result that k is proportional to the fractional surface area covered by surface renewal generated during the breaking process. In this report we investigate the role of microscale wave breaking in gas transfer by determining the correlation between k and AB, the fractional area coverage of microscale breaking waves. Simultaneous, colocated infrared (IR) and wave slope imagery is used to verify that AB detected using IR techniques corresponds to the fraction of surface area covered by surface renewal in the wakes of microscale breaking waves. Using measurements of k and AB made at the University of Washington wind-wave tank at wind speeds from 4.6 to 10.7 m sâ1, we show that k is linearly correlated with AB, regardless of the presence of surfactants. This result is consistent with Csanady's [1990] model and implies that microscale wave breaking is likely a fundamental physical mechanism contributing to gas transfer
Detection of liquid xenon scintillation light with a Silicon Photomultiplier
We have studied the feasibility of a silicon photomultiplier (SiPM) to detect
liquid xenon (LXe) scintillation light. The SiPM was operated inside a small
volume of pure LXe, at -95 degree Celsius, irradiated with an internal Am-241
alpha source. The gain of the SiPM at this temperature was estimated to be 1.8
x 10^6 with bias voltage at 52 V. Based on the geometry of the setup, the
quantum efficiency of the SiPM was estimated to be 22% at the Xe wavelength of
178 nm. The low excess noise factor, high single photoelectron detection
efficiency, and low bias voltage of SiPMs make them attractive alternative UV
photon detection devices to photomultiplier tubes (PMTs) for liquid xenon
detectors, especially for experiments requiring a very low energy detection
threshold, such as neutralino dark matter searches
Development, Validation and Preliminary Experiments of a Measuring Technique for Eggs Aging Estimation Based on Pulse Phase Thermography
Assessment of the freshness of hen eggs destinated to human consumption is an extremely important goal for the modern food industry and sale chains, as eggs show a rapid natural aging which also depends on the storage conditions. Traditional techniques, such as candling and visual observation, have some practical limitations related to the subjective and qualitative nature of the analysis. The main objective of this paper is to propose a robust and automated approach, based on the use of pulsed phase thermography (PPT) and image processing, that can be used as an effective quality control tool to evaluate the freshness of eggs. As many studies show that the air chamber size is proportional to the egg freshness, the technique relies on the monitoring of the air chamber parameters to infer egg aging over time. The raw and phase infrared images are acquired and then post-processed by a dedicated algorithm which has been designed to automatically measure the size of the air chamber, in terms of normalized area and volume. The robustness of the method is firstly assessed through repeatability and reproducibility tests, which demonstrate that the uncertainty in the measure of the air chamber size never exceeds 5%. Then, an experimental campaign on a larger sample of 30 eggs, equally divided into three size categories (M, L, XL), is conducted. For each egg, the main sizes of the air chamber are measured with the proposed method and their evolution over time is investigated. Results have revealed, for all the egg categories, the existence of an analytic relationship and a high degree of correlation (R-2 > 0.95) between the geometric data of the air chamber and the weight loss, which is a well-known marker of egg aging
Towards "green" smart materials for force and strain sensors: The case of polyaniline
Stress/strain sensors constitute a class of devices with a global ever-growing market
thanks to their use in many fields of modern life. They are typically constituted by thin metal foils
deposited on flexible supports. However, the low inherent resistivity and limited flexibility of their
constituents make them inadequate for several applications, such as measuring large movements in
robotic systems and biological tissues. As an alternative to the traditional compounds, in the present
work we will show the advantages to employ a smart material, polyaniline (PANI), prepared by an
innovative environmentally friendly route, for force/strain sensor applications wherein simple
processing, environmental friendliness and sensitivity are particularly required.This work was supported by FEDER through the COMPETE Program and by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Project PESTC/FIS/UI607/2011 and the project Matepro âOptimizing Materials and Processesâ, ref. NORTE-070124-FEDER-000037â, co-funded by the âPrograma Operacional Regional do Norteâ (ON.2 â O Novo Norte), under the âQuadro de ReferĂȘncia EstratĂ©gico Nacionalâ (QREN), through the âFundo Europeu de Desenvolvimento Regionalâ (FEDER). The authors also thank FCT for financial support under project PTDC/CTM-NAN/112574/2009. The authors also thank the COST Actions MP1003 (European Scientific Network for Artificial Muscles, ESNAM) and MP0902 (Composites of Inorganic Nanotubes and Polymers, COINAPO)
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