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An optimal on-site calibration method in measurement system of dynamic envelope curve of high-speed vehicle
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作者 LIU Meng LIU Chang-jie WU Xiao-han 《Journal of Measurement Science and Instrumentation》 CAS CSCD 2016年第4期398-404,共7页
High-speed vehicle dynamic envelope curve is defined as the maximum limit outline affected by a variety of adverse factors while the train is running. Considering the difficulties in the current measurement system suc... High-speed vehicle dynamic envelope curve is defined as the maximum limit outline affected by a variety of adverse factors while the train is running. Considering the difficulties in the current measurement system such as complicated calibration process,cumbersome aided-instruments,strict limitation of working distance, this paper carries out an optical method in which two high-speed cameras with variable-zoom lenses are adopted as binocular stereo sensors of measurement system and a high-ac-curacy 3D target with fast reconstruction is designed. The intrinsic parameters of the sensors and the relative positions between coordinate systems are solved by the method of colinearity constrained optimization algorithm. The calibration process is easy to operate and the device is also of portability. Most importantly, the severe working distance limitation between sensors and measured body is solved, enhancing the adaptability of measurement system to environment. Experimental results show that when the sensors are in the range of 8 -16 m away from the measured body, system accuracy can reach up to ±0. 5 mm, which meets the requirements to measure the dynamic envelope curve of high-speed vehicle. 展开更多
关键词 zoom lens 3D target colinearity constrain optimization algorithm binocular stereo vision dynamic envelope curve
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Symmetry of echinoderms: From initial bilaterally-asymmetric metamerism to pentaradiality
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作者 Sergey V. Rozhnov 《Natural Science》 2014年第4期171-183,共13页
Echinoderm radial symmetry has first appeared in the ambulacral system, when the ambulacral channel assumed the shape of a closed ring or a horseshoe with approximated ends, and then spread onto other organ systems. I... Echinoderm radial symmetry has first appeared in the ambulacral system, when the ambulacral channel assumed the shape of a closed ring or a horseshoe with approximated ends, and then spread onto other organ systems. Its origin was a natural consequence of a steady increase of the original asymmetry of bilaterally-asymmetric three-segmented ancestors of echinoderms, culminated by closing of the ancestral linear metamerism into radiality. The evolutionary transformation from a simple pouchlike hydrocoel with one side channel to an elongated hydrocoel (located under the oesophagus) with two side channels, and finally to a nearly closed horseshoeshaped hydrocoel with three radial channels can be reconstructed based on the theca structure and the number of ambulacra in the row SolutaCincta-Helicoplacoidea. After the hydrocoel with three outbound ambulacral channels circled around the oesophagus as a horseshoe, it either closed into a ring, or its ends became closely approximated. This has determined the primary triradiate symmetry, which quickly transformed into pentaradial symmetry of the 2-1-2 type as a result of branching of two of the three primary radial channels. This occurred no earlier than the Late Vendian, when the first bilaterians appeared to have begun to acquire body appendages, and no later than the Early Cambrian, when the first skeletal remains of echinoderms entered the fossil record (in the Atdabanian). The 2-1-2 pentaradial symmetry evolved into the true pentaradiality as a result of shifting the timing of tentacle branching to earlier stages of ontogenesis and even spreading of the five tentacle primordia over the ambulacral ring. This occurred during the Ordovician. 展开更多
关键词 ECHINODERMATA SYMMETRY Asymmetry METAMERISM Pentaradiality Body Plan HOX Genes colinearity
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Substituting Effect of Y in La_(0.5) Ba_(0.5) CoO_3
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作者 刘宜华 张汝贞 +3 位作者 王成建 岳龙强 季刚 梅良模 《Journal of Rare Earths》 SCIE EI CAS CSCD 2003年第3期347-350,共4页
La 0.5- x Y x Ba 0.5 CoO 3 polycrystals were prepared by solid state reaction. The substituting effects of Y for La on the magnetic and transport properties of the materials were studied systematically... La 0.5- x Y x Ba 0.5 CoO 3 polycrystals were prepared by solid state reaction. The substituting effects of Y for La on the magnetic and transport properties of the materials were studied systematically. The results indicate that substitution of Y induces two effects. Firstly, the charge transfer from Y to 3d orbital of Co happens. This causes the molecular magnetic moment to decrease. Secondly, the antiferromagnetic exchange interaction of Co ions appears. When the content of Y is less than or equal to 30%, the non colinear structure of spins in materials is observed. When the content of Y is greater than 30%, the materials transit from predominant ferromagnetic state to predominant antiferromagnetic one. The conductive mechanism for the materials with different content of Y belongs to the variable range hopping conduction of polarons. The resistivity of materials increases sharply with increasing Y content. 展开更多
关键词 La 0.5- x Y x Ba 0.5 CoO 3 compound charge transfer non colinear structure of spins variable range hopping conduction rare earths
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Modelling and Simulation of an Ohmic Heating Process
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作者 Hongwei Zhang Ahmed Mohamed +1 位作者 Timofei Breikin Martin Howarth 《Open Journal of Modelling and Simulation》 2021年第1期26-42,共17页
Ohmic Heating (OH) is one of the emerging thermal technologies used in food processing which can produce rapid and uniform heating with close to 100% energy transfer efficiency. Although mathematical </span><... Ohmic Heating (OH) is one of the emerging thermal technologies used in food processing which can produce rapid and uniform heating with close to 100% energy transfer efficiency. Although mathematical </span><span style="font-family:Verdana;">modelling</span><span style="font-family:Verdana;"> for OH processes has been studied by many researchers in recent years, systematic simulations of OH have not been developed for model-based control of the processes. In this paper, </span><span style="font-family:Verdana;">mathematical</span><span style="font-family:Verdana;"> model for a Colinear Ohmic Heater is presented, analyzed, and studied based on the selected configuration. A numerical solution for the mathematical equations has been defined and proposed. MATLAB/Simulink model is hence developed and validated against the available data. Simulation results have shown that </span><span style="font-family:Verdana;">MATLAB</span><span style="font-family:Verdana;">/Simulink model can produce robust outputs at low computational costs with an accuracy of up to 99.6% in comparison to the analytical solution. This model can be used in further studies for analysis of the OH processes and development of advanced controllers. 展开更多
关键词 Ohmic Heating Colinear Ohmic Heater Mathematical Modelling Numerical Solution MATLAB/Simulink Simulations
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