614 research outputs found
A Strategy for Teaching an Effective Undergraduate Mineralogy Course
An effective undergraduate mineralogy course provides students with a familiarity and understanding of minerals that is necessary for studying the Earth. This paper describes a strategy for integrating the disparate topics covered in a mineralogy course and for presenting them in a way that facilitates an understanding of mineralogy that enables students to apply it in subsequent courses and research. The course is organized into a well-integrated sequence of lectures, demonstrations and laboratory exercises that unfolds the material logically and at a pace that is responsive to the students’ needs. The course begins with six weeks on crystal chemistry, then five weeks covering analytical methods for characterizing minerals and ends with five weeks on the silicates. This order facilitates a progression of learning from the basic concepts to the more advanced and allows us to reinforce the concepts of crystal chemistry during the final section on the silicates. Optical mineralogy is almost entirely taught in the lab and is aided by use of a mineral identification chart developed to help students learn to identify minerals in thin section. Student performance is assessed through one technical paper and presentation as well as homework, essay exams and lab practicals. Educational levels: Graduate or professional
Some examples and applications of hilbert spaces with reproducing kernel
The purpose of this paper is to exhibit some examples and applications of kernal functions for Hilbert spaces and to illustrate some methods of finding reproducing kernels. This paper will also illustrate relationships between Hilbert space and function theory
Large Area Crop Inventory Experiment (LACIE). Intensive test site assessment report
There are no author-identified significant results in this report
Optimized Forest-Ruth- and Suzuki-like algorithms for integration of motion in many-body systems
An approach is proposed to improve the efficiency of fourth-order algorithms
for numerical integration of the equations of motion in molecular dynamics
simulations. The approach is based on an extension of the decomposition scheme
by introducing extra evolution subpropagators. The extended set of parameters
of the integration is then determined by reducing the norm of truncation terms
to a minimum. In such a way, we derive new explicit symplectic Forest-Ruth- and
Suzuki-like integrators and present them in time-reversible velocity and
position forms. It is proven that these optimized integrators lead to the best
accuracy in the calculations at the same computational cost among all possible
algorithms of the fourth order from a given decomposition class. It is shown
also that the Forest-Ruth-like algorithms, which are based on direct
decomposition of exponential propagators, provide better optimization than
their Suzuki-like counterparts which represent compositions of second-order
schemes. In particular, using our optimized Forest-Ruth-like algorithms allows
us to increase the efficiency of the computations more than in ten times with
respect to that of the original integrator by Forest and Ruth, and
approximately in five times with respect to Suzuki's approach. The theoretical
predictions are confirmed in molecular dynamics simulations of a Lennard-Jones
fluid. A special case of the optimization of the proposed Forest-Ruth-like
algorithms to celestial mechanics simulations is considered as well.Comment: 12 pages, 3 figures; submitted to Computer Physics Communication
Optimized Verlet-like algorithms for molecular dynamics simulations
New explicit velocity- and position-Verlet-like algorithms of the second
order are proposed to integrate the equations of motion in many-body systems.
The algorithms are derived on the basis of an extended decomposition scheme at
the presence of a free parameter. The nonzero value for this parameter is
obtained by reducing the influence of truncated terms to a minimum. As a
result, the new algorithms appear to be more efficient than the original Verlet
versions which correspond to a particular case when the introduced parameter is
equal to zero. Like the original versions, the proposed counterparts are
symplectic and time reversible, but lead to an improved accuracy in the
generated solutions at the same overall computational costs. The advantages of
the new algorithms are demonstrated in molecular dynamics simulations of a
Lennard-Jones fluid.Comment: 5 pages, 2 figures; submitted to Phys. Rev.
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Growth and alteration of uranium-rich microlite
Uranium-rich microlite, a pyrochlore-group mineral, occurs in 440 Ma old lithium pegmatites of the Mozambique Belt in East Africa. Microlite exhibits a pronounced growth zoning, with a U-free core surrounded by a U-rich rim (UO{sub 2} up to 17 wt.%). The core exhibits conjugate sets of straight cracks (cleavage planes) which provided pathways for a late-stage U-enriched pegmatitic fluid which interacted with the U-free microlite to produce a distinct U enrichment along the cracks and led to the formation of the U-rich rim. Following the stage of U incorporation into microlite, a second generation of hydrothermal fluids deposited mica along the cleavage planes. Subsequent to these two hydrothermal stages, the host rock was uplifted and subjected to intense low-temperature alteration during which Na, Ca and F were leached from the microlite crystals. This alteration also led to a hydration of microlite, but there is no evidence of U loss. These low-temperature alteration effects were only observed in the U-rich rim which is characterized by a large number of irregular cracks which are most probably the result of metamictization, as indicated by electron diffraction images and powder X-ray patterns. The pyrochlore-group minerals provide excellent natural analogues for pyrochlore-based nuclear waste forms, because samples of variable age and with high actinide contents are available
Pennsylvania Folklife Special 1960 Festival Issue
• Plain Dutch and Gay Dutch: Two Worlds in the Dutch Country • Pennsylvania Dutch • Displaced Dutchmen Crave Shoo-flies • Hex Signs: A Myth • Lebanon Valley Date Stones • Antiques in Dutchland • Antique or Folk Art: Which? • Folk Festival Program • Religious Patterns of the Dutch Country • The Costumes of the Plain Dutch • Love Feasts • Horse-and-Buggy Mennonites • The Courtship and Wedding Practices of the Old Order Amishhttps://digitalcommons.ursinus.edu/pafolklifemag/1008/thumbnail.jp
Algorithm for numerical integration of the rigid-body equations of motion
A new algorithm for numerical integration of the rigid-body equations of
motion is proposed. The algorithm uses the leapfrog scheme and the quantities
involved are angular velocities and orientational variables which can be
expressed in terms of either principal axes or quaternions. Due to specific
features of the algorithm, orthonormality and unit norms of the orientational
variables are integrals of motion, despite an approximate character of the
produced trajectories. It is shown that the method presented appears to be the
most efficient among all known algorithms of such a kind.Comment: 4 pages, 1 figur
On the construction of high-order force gradient algorithms for integration of motion in classical and quantum systems
A consequent approach is proposed to construct symplectic force-gradient
algorithms of arbitrarily high orders in the time step for precise integration
of motion in classical and quantum mechanics simulations. Within this approach
the basic algorithms are first derived up to the eighth order by direct
decompositions of exponential propagators and further collected using an
advanced composition scheme to obtain the algorithms of higher orders. Contrary
to the scheme by Chin and Kidwell [Phys. Rev. E 62, 8746 (2000)], where
high-order algorithms are introduced by standard iterations of a force-gradient
integrator of order four, the present method allows to reduce the total number
of expensive force and its gradient evaluations to a minimum. At the same time,
the precision of the integration increases significantly, especially with
increasing the order of the generated schemes. The algorithms are tested in
molecular dynamics and celestial mechanics simulations. It is shown, in
particular, that the efficiency of the new fourth-order-based algorithms is
better approximately in factors 5 to 1000 for orders 4 to 12, respectively. The
results corresponding to sixth- and eighth-order-based composition schemes are
also presented up to the sixteenth order. For orders 14 and 16, such highly
precise schemes, at considerably smaller computational costs, allow to reduce
unphysical deviations in the total energy up in 100 000 times with respect to
those of the standard fourth-order-based iteration approach.Comment: 23 pages, 2 figures; submitted to Phys. Rev.
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