452 research outputs found

    Potential time-cost benefits from use of orbital-height photographic data in cartographic programs

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    Cost effectiveness of mapping using satellite- borne photograph

    Anharmonic force field and vibrational frequencies of tetrafluoromethane (CF4_4) and tetrafluorosilane (SiF4_4)

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    Accurate quartic anharmonic force fields for CF4_4 and SiF4_4 have been calculated using the CCSD(T) method and basis sets of spdfspdf quality. Based on the {\it ab initio} force field with a minor empirical adjustment, the vibrational energy levels of these two molecules and their isotopomers are calculated by means of high order Canonical Van Vleck Perturbation Theory(CVPT) based on curvilinear coordinates. The calculated energies agree very well with the experimental data. The full quadratic force field of CF4_4 is further refined to the experimental data. The symmetrization of the Cartesian basis for any combination bands of TdT_d group molecules is discussed using the circular promotion operator for the doubly degenerate modes, together with tabulated vector coupling coefficients. The extraction of the spectroscopic constants from our second order transformed Hamiltonian in curvilinear coordinates is discussed, and compared to a similar procedure in rectilinear coordinates.Comment: (submitted to J. Chem. Phys.

    A Local Mode Study of Ring Puckering Effects in the Infrared Spectra of Cyclopentane

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    We report and interpret recently recorded high-resolution infrared spectra for the fundamentals of the CH2 scissors and CH stretches of gas phase cyclopentane at −26.1 and −50 ○C, respectively. We extend previous theoretical studies of this molecule, which is known to undergo barrierless pseudorotation due to ring puckering, by constructing local mode Hamiltonians of the stretching and scissor vibrations for which the frequencies, couplings, and linear dipoles are calculated as functions of the pseudorotation angle using B3LYP/6-311++(d,p) and MP2/cc-pVTZ levels of theory. Symmetrization (D5h) of the vibrational basis sets leads to simple vibration/pseudorotation Hamiltonians whose solutions lead to good agreement with the experiment at medium resolution, but which miss interesting line fractionation when compared to the high-resolution spectra. In contrast to the scissor motion, pseudorotation leads to significant state mixing of the CH stretches, which themselves are Fermi coupled to the scissor overtones

    A study of navigation in virtual space

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    In the physical world, man has developed efficient methods for navigation and orientation. These methods are dependent on the high-fidelity stimuli presented by the environment. When placed in a virtual world which cannot offer stimuli of the same quality due to computing constraints and immature technology, tasks requiring the maintenance of position and orientation knowledge become laborious. In this paper, we present a representative set of techniques based on principles of navigation derived from real world analogs including human and avian navigation behavior and cartography. A preliminary classification of virtual worlds is presented based on the size of the world, the density of objects in the world, and the level of activity taking place in the world. We also summarize an informal study we performed to determine how the tools influenced the subjects' navigation strategies and behavior. We conclude that principles extracted from real world navigation aids such as maps can be seen to apply in virtual environments

    The Effect of Online Quizzing on Understanding of Key Concepts in an Introduction to Psychology Course

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    Students enrolled in Introduction to Psychology were required to complete online chapter-review quizzes as part of their course. Using a within-subjects experimental design, we compared the students’ understanding of key concepts during a week when they were required to take an online review quiz to their understanding of key concepts during a week when an online review quiz was not offered. Results suggest that online quizzing improves understanding of key chapter concepts

    High energy vibrational excitations of nitromethane in liquid water

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    The pathways and timescales of vibrational energy flow in nitromethane are investigated in both gas and condensed phases using classical molecular mechanics, with a particular focus on relaxation in liquid water. We monitor the flow of excess energy deposited in vibrational modes of nitromethane into the surrounding solvent. A marked energy flux anisotropy is found when nitromethane is immersed in liquid water, with a preferential flow to those water molecules in contact to the nitro group. The factors that permit such anisotropic energy relaxation are discussed, along with the potential implications on the molecule's non-equilibrium dynamics. In addition, the energy flux analysis allows us to identify the solvent motions responsible for the uptake of solute energy, confirming the crucial role of water librations. Finally, we also show that no anisotropic vibrational energy relaxation occurs when nitromethane is surrounded by argon gas.A.J.R. acknowledges the financial support from the Departament de Recerca i Universitats de la Generalitat de Catalunya. C.C. acknowledges support from Spanish Grant No. PID2021-124297NB-C31, funded by MCIN/AEI/10.13039/501100011033 and “ERDF A way of making Europe.” E.L.S. gratefully acknowledges support from the NSF via Grant No. CHE-1900095. A.J.R. and R.R. acknowledge support from Grant No. PID2021-124297NB-C32, funded by MCIN/AEI/10.13039/501100011033 and FEDER, and from the Generalitat de Catalunya (Grant No. 2021 SGR 01411).Peer ReviewedPostprint (published version
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