Mortgage refinancing and the concentration of mortgage coupons

Because of the concentrated distribution of interest rates on outstanding mortgages, modest interest rate declines in 1997 and 1998 made refinancing a smart choice for a record number of homeowners. In addition, the strong economy and the age of mortgage loans likely contributed to the surge in refinancing activity.Mortgages ; Housing - Finance ; Interest rates

Energy utilisation in South Africa.

Bibliography: leaves 167-188.The purpose of this study is to provide the Department of Planning and the Environment with the following information: 1) The quantities and forms of input and useful energy used by different sectors of the South African economy. (The terms input energy and useful energy are defined in section 1.2 of this chapter). 2) The efficiency of conversion of input energy to useful energy. 3) Current and expected trends in energy utilization within individual sectors of the economy.The two year contract to carry out this study was awarded to the Energy Research Institute at the University of Cape Town. The work was undertaken by one engineer assisted by a graduate engineer, supported by secretarial staff and supervised by a professor of the Department of Mechanical Engineering

The Great Sea Race

The large swift cruiser was given the name Columbia, and her remarkable speed and beautiful appearance have combined to make her the pride of the new navy and have won for her the popular appellation, The Gem of the Ocean.\u27\u27 The name bestowed upon her is in accordance with a law requiring vessels of her size to be named after states of the Union, the District of Columbia being regarded as a state for this purpose

A Matter for Congratulations

The Madawaska was accepted by the Navy Department after her trial trip and was promptly laid up in ordinary. In 1869 her name was changed to Tennessee at the same time that many other names peculiar to the Civil War period were changed to others that in most cases were certainly not more appropriate

Time and Space Bounds for Reversible Simulation

We prove a general upper bound on the tradeoff between time and space that suffices for the reversible simulation of irreversible computation. Previously, only simulations using exponential time or quadratic space were known. The tradeoff shows for the first time that we can simultaneously achieve subexponential time and subquadratic space. The boundary values are the exponential time with hardly any extra space required by the Lange-McKenzie-Tapp method and the ($\log 3$)th power time with square space required by the Bennett method. We also give the first general lower bound on the extra storage space required by general reversible simulation. This lower bound is optimal in that it is achieved by some reversible simulations.Comment: 11 pages LaTeX, Proc ICALP 2001, Lecture Notes in Computer Science, Vol xxx Springer-Verlag, Berlin, 200

Reversible Simulation of Irreversible Computation by Pebble Games

Reversible simulation of irreversible algorithms is analyzed in the stylized form of a `reversible' pebble game. While such simulations incur little overhead in additional computation time, they use a large amount of additional memory space during the computation. The reacheable reversible simulation instantaneous descriptions (pebble configurations) are characterized completely. As a corollary we obtain the reversible simulation by Bennett and that among all simulations that can be modelled by the pebble game, Bennett's simulation is optimal in that it uses the least auxiliary space for the greatest number of simulated steps. One can reduce the auxiliary storage overhead incurred by the reversible simulation at the cost of allowing limited erasing leading to an irreversibility-space tradeoff. We show that in this resource-bounded setting the limited erasing needs to be performed at precise instants during the simulation. We show that the reversible simulation can be modified so that it is applicable also when the simulated computation time is unknown.Comment: 11 pages, Latex, Submitted to Physica

Schröder quasigroups with a specified number of idempotents

AbstractSchröder quasigroups have been studied quite extensively over the years. Most of the attention has been given to idempotent models, which exist for all the feasible orders v, where v≡0,1(mod4) except for v=5,9. There is no Schröder quasigroup of order 5 and the known Schröder quasigroup of order 9 contains 6 non-idempotent elements. It is known that the number of non-idempotent elements in a Schröder quasigroup must be even and at least four. In this paper, we investigate the existence of Schröder quasigroups of order v with a specified number k of idempotent elements, briefly denoted by SQ(v,k). The necessary conditions for the existence of SQ(v,k) are v≡0,1(mod4), 0≤k≤v, k≠v−2, and v−k is even. We show that these conditions are also sufficient for all the feasible values of v and k with few definite exceptions and a handful of possible exceptions. Our investigation relies on the construction of holey Schröder designs (HSDs) of certain types. Specifically, we have established that there exists an HSD of type 4nu1 for u=1,9, and 12 and n≥max{(u+2)/2,4}. In the process, we are able to provide constructions for a very large variety of non-idempotent Schröder quasigroups of order v, all of which correspond to v2×4 orthogonal arrays that have the Klein 4-group as conjugate invariant subgroup

Local permutations of products of Bell states and entanglement distillation

We present new algorithms for mixed-state multi-copy entanglement distillation for pairs of qubits. Our algorithms perform significantly better than the best known algorithms. Better algorithms can be derived that are tuned for specific initial states. The new algorithms are based on a characterization of the group of all locally realizable permutations of the 4^n possible tensor products of n Bell states.Comment: 6 pages, 1 figur