4,076 research outputs found
Flow and chemical characteristics of the St. Johns River at Jacksonville, Florida
This report will be of substantial value to water managers in developing the
St. Johns River as a multiple resource. Evaluation of the capacity of the river to
accept pollutants without adversely affecting other uses requires detailed data of
flow and chemical characteristics and an understanding of how they interact. (66 page document
Some z<sub>n-1</sub> terraces from z<sub>n</sub> power-sequences, n being an odd prime power
A terrace for Zm is a particular type of sequence formed from the m elements of Zm. For m
odd, many procedures are available for constructing power-sequence terraces for Zm; each terrace of this
sort may be partitioned into segments, of which one contains merely the zero element of Zm, whereas
every other segment is either a sequence of successive powers of an element of Zm or such a sequence
multiplied throughout by a constant. We now refine this idea to show that, for m=n−1, where n is an odd prime power, there are many ways in which power-sequences in Zn can be used to arrange the elements of Zn \ {0} in a sequence of distinct entries i, 1 ≤ i ≤ m, usually in two or more segments, which becomes a terrace for Zm when interpreted modulo m instead of modulo n. Our constructions provide terraces for Zn-1 for all prime powers n satisfying 0 < n < 300 except for n = 125, 127 and 257
Narcissistic half-and-half power-sequence terraces for Zn with n=pqt
AbstractA power-sequence terrace for Zn is a Zn terrace that can be partitioned into segments one of which contains merely the zero element of Zn whilst each other segment is either (a) a sequence of successive powers of an element of Zn, or (b) such a sequence multiplied throughout by a constant. If n is odd, a Zn terrace (a1,a2,…,an) is a narcissistic half-and-half terrace if ai−ai−1=an+2−i−an+1−i for i=2,3,…,(n+1)/2. Constructions are provided for narcissistic half-and-half power-sequence terraces for Zn with n=pqt where p and q are distinct odd primes and t is a positive integer. All the constructions are for terraces with as few segments as possible. Attention is restricted to constructions covering values of n with n=pqt and n<300; terraces are provided for all such values except n=189. Particularly elegant constructions are available for n=275
Time-weighted multi-touch attribution and channel relevance in the customer journey to online purchase
We address statistical issues in attributing revenue to marketing channels and inferring the importance of individual channels in customer journeys towards an online purchase. We describe the relevant data structures and introduce an example. We suggest an asymmetric bathtub shape as appropriate for time-weighted revenue attribution to the customer journey, provide an algorithm, and illustrate the method. We suggest a modification to this method when there is independent information available on the relative values of the channels. To infer channel importance, we employ sequential data analysis ideas and restrict to data which ends in a purchase. We propose metrics for source, intermediary, and destination channels based on twoand three-step transitions in fragments of the customer journey. We comment on the practicalities of formal hypothesis testing. We illustrate the ideas and computations using data from a major UK online retailer. Finally, we compare the revenue attributions suggested by the methods in this paper with several common attribution methods
Localization and diffusion in Ising-type quantum networks
We investigate the effect of phase randomness in Ising-type quantum networks.
These networks model a large class of physical systems. They describe micro-
and nanostructures or arrays of optical elements such as beam splitters
(interferometers) or parameteric amplifiers. Most of these stuctures are
promising candidates for quantum information processing networks. We
demonstrate that such systems exhibit two very distinct types of behaviour. For
certain network configurations (parameters), they show quantum localization
similar to Anderson localization whereas classical stochastic behaviour is
observed in other cases. We relate these findings to the standard theory of
quantum localization.Comment: 12 page
Effect of Interband Transitions on the c axis Penetration Depth of Layered Superconductors
The electromagnetic response of a system with two planes per unit cell
involves, in addition to the usual intraband contribution, an added interband
term. These transitions affect the temperature dependence and the magnitude of
the zero temperature c-axis penetration depth. When the interplane hopping is
sufficiently small, the interband transitions dominate the low temperature
behaviour of the penetration depth which then does not reflect the linear
temperature dependence of the intraband term and in comparison becomes quite
flat even for a d-wave gap. It is in this regime that the pseudogap was found
in our previous normal state calculations of the c-axis conductivity, and the
effects are connected.Comment: 8 pages, 5 figure
Recommended from our members
Standardization, calibration and innovation: a special issue on lithic microwear method
YesThis paper introduces a special issue of the Journal of Archaeological Science that considers the current state and future directions in lithic microwear analysis. There is considerable potential for lithic microwear analysis to reconstruct past human behaviour as it can provide direct insight into past activities. Consequently, it is a technique worthy of significant additional investment and continued development. To further the cause of methodological maturation within microwear analysis and to promote standardization, calibration, and innovation, the following collection of papers present various approaches and perspectives on how greater methodological refinement and increased reliability of results can and should be achieved. Many of these papers were part of a session held at the 2011 Society for American Archaeology Meeting (SAA) in Sacramento, California, while others were selected from the 2012 International Conference on Use-Wear Analysis in Faro, Portugal. The purpose of the SAA session and this special themed issue is essentially two-fold. The first is to promote awareness of the need for methodological standardization, calibration, and continuing innovation. The second is to open a serious dialogue about how these aims could be pursued and achieved.AAE was supported by the AHRC (AH/J007935/1). HJL was supported by L’Équipe Archéometrie at the Laboratoires d’ Archéologie, a part of the Centre Interuniversitaire d’Études sur les Lettres, les Arts et les Traditions (CELAT) at Université Laval. DAM was supported by Fondation Fyssen and the University of Toronto. WJS was supported by Faculty Development Grant from Keene State College
Probing e-e interactions in a periodic array of GaAs quantum wires
We present the results of non-linear tunnelling spectroscopy between an array
of independent quantum wires and an adjacent two-dimensional electron gas
(2DEG) in a double-quantum-well structure. The two layers are separately
contacted using a surface-gate scheme, and the wires are all very regular, with
dimensions chosen carefully so that there is minimal modulation of the 2DEG by
the gates defining the wires. We have mapped the dispersion spectrum of the 1D
wires down to the depletion of the last 1D subband by measuring the conductance
\emph{G} as a function of the in-plane magnetic field \emph{B}, the interlayer
bias and the wire gate voltage. There is a strong suppression of
tunnelling at zero bias, with temperature and dc-bias dependences consistent
with power laws, as expected for a Tomonaga-Luttinger Liquid caused by
electron-electron interactions in the wires. In addition, the current peaks fit
the free-electron model quite well, but with just one 1D subband there is extra
structure that may indicate interactions.Comment: 3 pages, 3 figures; formatting correcte
Study of Neutron-Induced Ionization in Helium and Argon Chamber Gases
Ion chambers used to monitor the secondary hadron and tertiary muon beam in
the NuMI neutrino beamline will be exposed to background particles, including
low energy neutrons produced in the beam dump. To understand these backgrounds,
we have studied Helium- and Argon-filled ionization chambers exposed to intense
neutron fluxes from PuBe neutron sources ( MeV). The sources emit
about 10 neutrons per second. The number of ion pairs in the chamber gas
volume per incident neutron is derived. While limited in precision because of a
large gamma ray background from the PuBe sources, our results are consistent
with the expectation that the neutrons interact purely elastically in the
chamber gas.Comment: accepted for publication in NIM
Modelling the future of the Hawaiian honeycreeper : an ecological and epidemiological problem
The Hawaiian honeycreeper (Drepanididae) faces the threat of extinction; this is believed to be due primarily to predation from alien animals, endemic avian malaria (Plasmodium relictum) and climate change. A deterministic SI modelling approach is developed, incorporating these three factors and a metapopulation approach in conjunction with a quasi-equilibrium assumption to simplify the vector populations. This enables the qualitative study of the behaviour of the system. Numerical results suggest that although (partial) resistance to avian malaria may be advantageous for individual birds, allowing them to survive infection, this allows them to become carriers of infection and hence greatly increases the spread of this disease. Predation obviously reduces the life-expectancy of honeycreepers, but in turn this reduces the spread of infection from resistant carriers; therefore the population-level impact of predation is reduced. Various control strategies proposed in the literature are also considered and it is shown that predation control could either help or hinter, depending upon resistance of the honeycreeper species. Captive propagation or habitat restoration may be the best feasible solution to the loss of both heterogeneity within the population and the loss of the species as a whole
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