This paper proposes a low-order geometrically exact flexible beam formulation based on the utilization of generic beam shape functions to approximate distributed kinematic properties of the deformed ...structure. The proposed nonlinear beam shapes approach is in contrast to the majority of geometrically nonlinear treatments in the literature in which element-based—and hence high-order—discretizations are adopted. The kinematic quantities approximated specifically pertain to shear and extensional gradients as well as local orientation parameters based on an arbitrary set of globally referenced attitude parameters. In developing the dynamic equations of motion, an Euler angle parametrization is selected as it is found to yield fast computational performance. The resulting dynamic formulation is closed using an example shape function set satisfying the single generic kinematic constraint. The formulation is demonstrated via its application to the modelling of a series of static and dynamic test cases of both simple and non-prismatic structures; the simulated results are verified using MSC Nastran and an element-based intrinsic beam formulation. Through these examples, it is shown that the nonlinear beam shapes approach is able to accurately capture the beam behaviour with a very minimal number of system states.
This paper considers the selection of structural shape bases for the modelling of flexible beams using the nonlinear beam shapes formulation. The approach provides a low order geometrically nonlinear ...representation of a flexible beam using a kinematic description that is geometrically exact; a minimal state representation is achieved by projecting the problem onto a set of shape functions spanning the beam. Motivated by the requirements for the low-order modelling of aeroelastic systems, this study examines the practical requirements of applying these shape sets to a flexible wing problem. A number of candidate shape sets are presented: orthogonal and non-orthogonal, with and without load dependent boundary conditions. The efficiency with which this problem is solved is used to assess the performance of each candidate shape set and infer the common properties between the most efficient bases. For a system with a moderate number of states a fairly consistent performance is observed across all of the sets. For larger sized problems, orthogonality of the shape basis is required to ensure robustness and scalability. It is shown that for a generic basis set the necessary boundary conditions of the problem can be easily satisfied, furthermore any orthogonal properties of a chosen basis can be retained. This concept is extended to allow for the treatment of more complex configurations starting from a simple shape basis.
•Satisfaction of natural boundary conditions not required in constructing an efficient representation.•Orthogonality of base sets ensures robustness of formulation for problems over larger state sets.•Set scaling may be used to satisfy the kinematic boundary conditions for generic starting bases.•Orthogonality of the chosen base sets may be retained throughout the scaling process.•More complex non-smooth configurations may be treated starting from a simple initial shape basis.
Enchytraeids are important organisms of the soil biocenosis. They improve the soil pore structure and the degradation of organic matter. These organisms are used in standardized testing, using ...survival and reproduction (6 weeks) as endpoints. The use of biomarkers, linked to ecologically relevant alterations at higher levels of biological organization, is a promising tool for Environmental Risk Assessment. Here, enchytraeids were exposed for different time periods (two days and three weeks) to different soils (OECD artificial soil, different compositions in its organic matter, clay or pH value, and LUFA 2.2 natural soil) and different chemicals (Phenmedipham and copper). The main question addressed in the present study was if the effects of chemicals and different soil properties are preceded by alterations at the sub-cellular level, and if these endpoints may be used reliantly as faster screening tools for the assessment of different stress conditions in soils. The parameters measured in
E. albidus whole body were: lipid peroxidation (LPO), total glutathione (TG), as well as the enzymatic activities of superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), glutathione peroxidase (GPx) and glutathione
S-transferase (GST). The results showed that biomarker responses in
E. albidus were significantly affected by the soil type (GST, CAT, GPx, GR and LPO) and the duration of exposure in OECD artificial soil (GST, GPx, GR, CAT and LPO) but not in LUFA 2.2 natural soil. For the abiotic factors studied, after 2 days, low pH decreased significantly the TG levels and the activities of CAT and GR,and low OM also significantly decreased CAT and GR activities. After 3 weeks, differences in soil properties caused a decrease in GR and GPx activities, whereas increased GST activity was observed due to low organic matter and pH. Copper significantly increased the activities of CAT, GPx and GR, and decreased the activity of GST after 2 days as well as inscreasing LPO levels after 3 weeks. Phenmedipham increased LPO levels, associated with increased levels of TG as well as increased activities of CAT and GPx and decreased GST activity after 3 weeks exposure. This study shows that both abiotic and chemical stresses could be followed through biomarker analysis and that some of these determinations are potential endpoints in a quick soil contamination assessment procedure.
Enchytraeus albidus are important organisms of the soil biocenosis, used as standard test species in environmental risk assessment. The inhibition of cholinesterases (ChE) activity of several species ...has been widely used to assess the exposure and effects of anti-cholinesterase environmental contaminants. Several studies have shown the association between ChE activity inhibition and adverse effects on behaviour and survival. Extensive studies addressing survival and behavioural endpoints, as well as other biomarkers, have been done in E. albidus with different types of soil contaminants. The main objectives of this study were: (1) to characterize biochemically the ChE present in the soluble post-mitochondrial fraction of E. albidus whole body homogenates, using different substrates and selective inhibitors; (2) to assess the in vivo effects of copper, phenmedipham and different soil properties (pH, organic matter, clay) on the ChE activity; (3) to assess the in vitro effects of copper and phenmedipham on the ChE activity. The results suggest the presence of one ChE in the soluble post-mitochondrial fraction of E. albidus whole body homogenates, which displays properties of both acetylcholinesterase and pseudocholinesterase considering the typical mammalian enzymes. It is also shown that ChE activity is not inhibited by exposure to different soil properties and that copper and phenmedipham inhibited ChE activity both in in vivo and in in vitro conditions and therefore ChE inhibition seems to be a robust biomarker for this herbicide and this heavy metal. This study showed that ChE activity in E. albidus might be correlated to previously determined higher level effects like survival and reproduction, as well as avoidance behaviour.
This paper reports the first measurement using the NOvA detectors of nu sub(mu) disappearance in a nu sub(mu) beam. The analysis uses a 14 kton-equivalent exposure of 2.74x10 super(20) ...protons-on-target from the Fermilab NuMI beam. Assuming the normal neutrino mass hierarchy, we measure (ProQuest: Formulae and/or non-USASCII text omitted) and sin super(2)theta sub(23) in the range 0.38-0.65, both at the 68% confidence level, with two statistically degenerate best-fit points at sin super(2)theta sub(23)=0.4 3 and 0.60. Results for the inverted mass hierarchy are also presented.
This paper proposes a low-order geometrically exact flexible beam formulation based on the utilization of generic beam shape functions to approximate distributed kinematic properties of the deformed ...structure. The proposed nonlinear beam shapes approach is in contrast to the majority of geometrically nonlinear treatments in the literature in which element-based—and hence high-order—discretizations are adopted. The kinematic quantities approximated specifically pertain to shear and extensional gradients as well as local orientation parameters based on an arbitrary set of globally referenced attitude parameters. In developing the dynamic equations of motion, an Euler angle parametrization is selected as it is found to yield fast computational performance. The resulting dynamic formulation is closed using an example shape function set satisfying the single generic kinematic constraint. The formulation is demonstrated via its application to the modelling of a series of static and dynamic test cases of both simple and non-prismatic structures; the simulated results are verified using MSC Nastran and an element-based intrinsic beam formulation. Through these examples, it is shown that the nonlinear beam shapes approach is able to accurately capture the beam behaviour with a very minimal number of system states.
The MINOS data acquisition system Belias, A.; Crone, G.J.; Harris, E.F. ...
IEEE transactions on nuclear science,
06/2004, Letnik:
51, Številka:
3
Journal Article
Recenzirano
Odprti dostop
The MINOS long-baseline neutrino experiment consists of two detectors separated by 730 km. Both are equipped with identical data acquisition (DAQ) systems, based on continuous, dead time free ...readout. Data are read from the untriggered front-end electronics by VME single board computers and transferred across high-speed PCI data links for consolidation by data routing processors. An array of Linux computers selects events of interest using software-based trigger algorithms. We present the design of the DAQ system and report on experience gathered during early operation of the experiment.
On the linearity of the MINOS light-injection calibration system Adamson, P; Barrett, L; Belias, A ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2004, Letnik:
521, Številka:
2
Journal Article
Recenzirano
The MINOS light-injection calibration system has been fully documented in a previous article (Nucl. Instr. and Meth. A 492 (2002) 353). Upon commissioning in the MINOS detectors, the system was found ...to give a non-linear response to variations in the intensity of injected light. The source of this non-linearity has been traced to a small change in the spectrum of the injected light as a function of the current applied to the original blue LEDs, in combination with a rapidly varying spectral response function of the wavelength-shifting fibre used in the detector. Both aspects of the problem have been addressed successfully by use of LEDs with different spectral characteristics, and the system now has a linear response.
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