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231.
232.
John R. Rogers 《Mechatronics》2009,19(5):774-779
A low-cost robotic arm and controller system is presented. The controller is a desktop model of the robotic arm with the same degrees of freedom whose joints are equipped with sensors. Manipulating the controller by hand causes the robotic arm to mimic the movement in master–slave fashion. This is accomplished simply and at low-cost by taking advantage of widely available hobby radio control components. The system uses the trainer (“Buddy Box”) function available on common radio control transmitters as a simple interface between microcontroller and transmitter. The microcontroller produces a time-division multiplexed signal comprising three channels in proportional pulse modulated (PPM) format. The arm design could be used for various light-duty applications and this paper describes a version fitted with a video camera. The arm prototype is designed for an under-vehicle inspection robot. In this application, the video camera mounted on the robotic arm allows inspection of difficult-to-view locations under vehicles. The master–slave operator interface provides an easy-to-learn method for robotic arm manipulation. 相似文献
233.
Teeters-Kennedy SM Rodriguez KR Rogers TM Zomchek KA Williams SM Sudnitsyn A Carter L Cherezov V Caffrey M Coe JV 《The journal of physical chemistry. B》2006,110(43):21719-21727
The flow of polarized light through a metal film with an array of microchannels is controlled by the phase of an optically active, phospholipid nanocoating, even though the coating does not cover the open area of the microchannels. The molecular details of the assembly (DPPC phospholipid monolayer/bilayer on a hexadecanethiol monolayer on a copper- or nickel-coated microarray) were determined using the infrared, surface-plasmon-mediated, extraordinary transmission of the metal microarrays. Infrared absorption spectra with greatly enhanced absorptions by comparison to literature were recorded and used as a diagnostic for the phase, composition, and molecular geometry of these nanocoatings. This approach presents new tools for nanoscale construction in constricted microspaces, which may ultimately be useful with individual microchannels. 相似文献
234.
Famiano MA Liu T Lynch WG Mocko M Rogers AM Tsang MB Wallace MS Charity RJ Komarov S Sarantites DG Sobotka LG Verde G 《Physical review letters》2006,97(5):052701
Recent measurements of preequilibrium neutron and proton transverse emission from (112,124)Sn+(112,124)Sn reactions at 50 MeV/A have been completed at the National Superconducting Cyclotron Laboratory. Free nucleon transverse emission ratios are compared to those of A=3 mirror nuclei. Comparisons are made to Boltzmann-Uehling-Uhlenbeck (BUU) transport calculations and conclusions concerning the density dependence of the asymmetry term of the nuclear equation of state at subnuclear densities are made. Comparison to BUU model predictions indicate a density dependence of the asymmetry energy that is closer to a form in which the asymmetry energy increases as the square root of the density for the density region studied. A coalescent-invariant analysis is introduced as a means of reducing suggested difficulties with cluster emission in total nucleon emission. 相似文献
235.
Leo Rogers 《Research in Mathematics Education》2013,15(1):225-240
Reference to the history of mathematics has been widely used in discussions of the development of curricula, the problems students have in learning mathematics, and the development of concepts in the individual. This paper examines the background to the "Biogenetic Law" [1] which has influenced so much thinking in educational theory, and the use of the "principle of parallelism" where individual development is claimed to mirror the historical development of the subject matter. Interpretations of the history of mathematics which are used to justify these claims are examined, and the universality of the supposed concepts is challenged. Questions are raised about some of the fundamental tenets of Piagetian epistemology. 相似文献
236.
Interfacial energy is a fundamental physiochemical property of any multi-phase system. Among the most direct approaches for determining solid–liquid interfacial energy is a technique based on measuring the shape of grain boundary grooves in specimens subjected to a linear temperature gradient. This technique was adapted to crystallizing colloids in a gravitational field. Such colloids exhibit a freezing–melting phase transition and are important not only as self-assembling precursors to photonic crystals, but also as physical models of atomic and molecular systems. The grain boundary groove technique was tested using suspensions of sterically stabilized poly(methyl methacrylate) spheres, which have been shown to closely approximate the hard sphere potential. Whereas isotropic models did not fit grain boundary groove data well, the capillary vector model, which is suitable for both isotropic and anisotropic surface energies, produced γ110?=?0.58?±?0.05 k B T/σ2. This value of interfacial energy is in agreement with many of the published values for hard spheres, supporting the validity of our grain boundary groove technique adaptations to colloidal systems in a gravitational field. Finally, kinks observed in groove profiles suggest a minimum anisotropy parameter of ε?=?0.029 for hard spheres. 相似文献
237.
We prove formulas for special values of the Ramanujan tau zeta function. Our formulas show that L(Δ,k) is a period in the sense of Kontsevich and Zagier when k?12. As an illustration, we reduce L(Δ,k) to explicit integrals of hypergeometric and algebraic functions when k∈{12,13,14,15}. 相似文献
238.
239.
Three-field simulations of interchange turbulence are presented for a simple magnetized toroidal plasma with a vertical magnetic field. The simulations show the presence of two turbulent regimes characterized by low (L) and high (H) confinement properties. We evaluate analytically the properties of the L regime, obtaining expressions for the plasma gradients and for the density and heat fluxes that agree well with the simulations. By increasing the plasma source strength or reducing the vertical magnetic field, a transition to a H regime occurs, in which a strong velocity shear limits the perpendicular transport with respect to the L scaling and the plasma profiles steepen. The analytic estimate of the transition condition is in accord with the simulations. 相似文献
240.