Optimal Trajectories For Orbital Transfers Using Low And Medium Thrust Propulsion Systems

For many problems it is reasonable to expect that the minimum time solution is also the minimum fuel solution. However, if one allows the propulsion system to be turned off and back on, it is clear that these two solutions may differ. In general, high thrust transfers resemble the well-known impulsive transfers where the burn arcs are of very short duration. The low and medium thrust transfers differ in that their thrust acceleration levels yield longer burn arcs which will require more revolutions, thus making the low thrust transfer computational intensive. Here, we consider optimal low and medium thrust orbital transfers

Two-dimensional frustrated spin systems in high magnetic fields

We discuss our numerical results on the properties of the S = 1/2 frustrated J1-J2 Heisenberg model on a square lattice as a function of temperature and frustration angle phi = atan(J2/J1) in an applied magnetic field. We cover the full phase diagram of the model in the range -pi <= phi <= pi. The discussion includes the parameter dependence of the saturation field itself, and addresses the instabilities associated with it. We also discuss the magnetocaloric effect of the model and show how it can be used to uniquely determine the effective interaction constants of the compounds which were investigated experimentally.Comment: 4 pages, 5 figures, proceedings of RHMF 200

AFES Miscellaneous Publication 2010-02

Research has been conducted since 2001 to assist growers in identifying components of peony field cut flower production and distribution from field selection and planting to post harvest handling and packaging for export. This experiment addressed three components of the production cycle: field planting dates, root quality and plant productivity, and post harvest handling of cut stems. In a comparison of planting times (autumn, spring or as containerized plants in mid summer), ‘Sarah Bernhardt’ and ‘Felix Crouse’ showed no difference in shoot number and growth one full year after planting. ‘Duchess de Nemours’ and ‘Alexander Fleming’ showed significant reductions in growth compared to the other cultivars, and we suspect disease rather than planting time as the problem. All treatments where bud break had occurred in storage with ‘Duchess de Nemours’ and ‘Alexander Fleming,’ new shoots rotted, and recovery was slow. A treatment of elemental sulfur was not sufficient to protect roots from storage rot. ‘Sarah Bernhardt’ roots and crown buds were weighed, counted and measured prior to planting in order to learn if a correlation exists between root quality and subsequent growth and flowering. Three root attributes were correlated with the total number of stems produced: total number of eyes per plant, total number of roots per plant, and root fresh weight. Characteristics such as root length and maximum diameter were not correlated with subsequent growth. We found no relationship between any root characteristics and the number of flowering stems and foliage height in the first year. The attributes that showed correlation could not be fitted to a linear or curvilinear model explaining the nature of the correlation. Larger sample sizes will be necessary to clarify these relationships. The best method for handling peony cut flowers for greatest vase life is to cut peonies dry and store them dry in a cooler (34°F) at 80+% relative humidity until shipping. Use of water in buckets in the field or pulsing flowers with water in the cooler does not improve vase life of peonies. Under optimum conditions, ‘Sarah Bernhardt’ peonies lasted up to 15 days in a vase, 8-9 days from bud break to full bloom, and an additional 5-6 days in full bloom. Chilling in a cooler is the most important attribute to long vase life

Entanglement can completely defeat quantum noise

We describe two quantum channels that individually cannot send any information, even classical, without some chance of decoding error. But together a single use of each channel can send quantum information perfectly reliably. This proves that the zero-error classical capacity exhibits superactivation, the extreme form of the superadditivity phenomenon in which entangled inputs allow communication over zero capacity channels. But our result is stronger still, as it even allows zero-error quantum communication when the two channels are combined. Thus our result shows a new remarkable way in which entanglement across two systems can be used to resist noise, in this case perfectly. We also show a new form of superactivation by entanglement shared between sender and receiver.Comment: 4 pages, 1 figur

Improving zero-error classical communication with entanglement

Given one or more uses of a classical channel, only a certain number of messages can be transmitted with zero probability of error. The study of this number and its asymptotic behaviour constitutes the field of classical zero-error information theory, the quantum generalisation of which has started to develop recently. We show that, given a single use of certain classical channels, entangled states of a system shared by the sender and receiver can be used to increase the number of (classical) messages which can be sent with no chance of error. In particular, we show how to construct such a channel based on any proof of the Bell-Kochen-Specker theorem. This is a new example of the use of quantum effects to improve the performance of a classical task. We investigate the connection between this phenomenon and that of ``pseudo-telepathy'' games. The use of generalised non-signalling correlations to assist in this task is also considered. In this case, a particularly elegant theory results and, remarkably, it is sometimes possible to transmit information with zero-error using a channel with no unassisted zero-error capacity.Comment: 6 pages, 2 figures. Version 2 is the same as the journal version plus figure 1 and the non-signalling box exampl

Full-Day Kindergarten in California: Lessons From Los Angeles

Analyzes the impact of full-day kindergarten on academic, grade retention, and English fluency outcomes through second grade by school and student characteristics, with a focus on the economically disadvantaged and English learners. Outlines implications

Why don't students attend lectures and what can be done about it through using iPod nanos?

Copyright © 2006 Shannon, S. J.How can teachers encourage students to listen in lectures – and indeed to attend them? What about international students and those who have language difficulties? These were the questions which triggered a study of the beliefs of first year students about learning from lectures, and a desire to improve students’ ability to learn from lectures through providing MP3 uploads and a classroom set of iPod nanos. Students completed a pre- and post-course evaluation which revealed their beliefs about lecture attendance and supplementing that attendance by listening to lectures on iPods for revision and re-listening

Half-magnetization plateau stabilized by structural distortion in the antiferromagnetic Heisenberg model on a pyrochlore lattice

Magnetization plateaus, visible as anomalies in magnetic susceptibility at low temperatures, are one of the hallmarks of frustrated magnetism. We show how an extremely robust half-magnetization plateau can arise from coupling between spin and lattice degrees of freedom in a pyrochlore antiferromagnet, and develop a detailed symmetry of analysis of the simplest possible scenario for such a plateau state. The application of this theory to the spinel oxides CdCr2O4 and HgCr2O4, where a robust half magnetization plateau has been observed, is discussed.Comment: 4 pages, 4 figure

Quantum data compression, quantum information generation, and the density-matrix renormalization group method

We have studied quantum data compression for finite quantum systems where the site density matrices are not independent, i.e., the density matrix cannot be given as direct product of site density matrices and the von Neumann entropy is not equal to the sum of site entropies. Using the density-matrix renormalization group (DMRG) method for the 1-d Hubbard model, we have shown that a simple relationship exists between the entropy of the left or right block and dimension of the Hilbert space of that block as well as of the superblock for any fixed accuracy. The information loss during the RG procedure has been investigated and a more rigorous control of the relative error has been proposed based on Kholevo's theory. Our results are also supported by the quantum chemistry version of DMRG applied to various molecules with system lengths up to 60 lattice sites. A sum rule which relates site entropies and the total information generated by the renormalization procedure has also been given which serves as an alternative test of convergence of the DMRG method.Comment: 8 pages, 7 figure