430 research outputs found
Interim report of the research committee
The Research Committee was charged to establish topics and relative priorities for sponsored and personal historical research over the short term (3 to 5 years) such that the widest benefit would accrue to the accounting discipline. Appropriate methodologies for research in accounting history were also to be identified and evaluated
Accounting for foreign currency translation: Current problems in historical perspective
The historical review of the evolution of accounting principles for foreign currency translation reveals that current practice is based on principles which have been developed during periods characterized by (1) wars and political instability, (2) major upheavals of the international monetary system, (3) run-away inflation with significant differences in the inflation rates of various countries, (4) relatively minor international operations in comparison with today\u27s multitude of significant multinational business linkages, and (5) a perception of international operations as being foreign -in the original sense of that word-to U. S. companies
Anthropomorphic Coding of Speech and Audio: A Model Inversion Approach
Auditory modeling is a well-established methodology that provides insight into human perception and that facilitates the extraction of signal features that are most relevant to the listener. The aim of this paper is to provide a tutorial on perceptual speech and audio coding using an invertible auditory model. In this approach, the audio signal is converted into an auditory representation using an invertible auditory model. The auditory representation is quantized and coded. Upon decoding, it is then transformed back into the acoustic domain. This transformation converts a complex distortion criterion into a simple one, thus facilitating quantization with low complexity. We briefly review past work on auditory models and describe in more detail the components of our invertible model and its inversion procedure, that is, the method to reconstruct the signal from the output of the auditory model. We summarize attempts to use the auditory representation for low-bit-rate coding. Our approach also allows the exploitation of the inherent redundancy of the human auditory system for the purpose of multiple description (joint source-channel) coding
Testing the assumptions of linear prediction analysis in normal vowels
This paper develops an improved surrogate data test to show experimental evidence, for all the simple vowels of US English, for both male and female speakers, that Gaussian linear prediction analysis, a ubiquitous technique in current speech technologies, cannot be used to extract all the dynamical structure of real speech time series. The test provides robust evidence undermining the validity of these linear techniques, supporting the assumptions of either dynamical nonlinearity and/or non-Gaussianity common to more recent, complex, efforts at dynamical modelling speech time series. However, an additional finding is that the classical assumptions cannot be ruled out entirely, and plausible evidence is given to explain the success of the linear Gaussian theory as a weak approximation to the true, nonlinear/non-Gaussian dynamics. This supports the use of appropriate hybrid linear/nonlinear/non-Gaussian modelling. With a calibrated calculation of statistic and particular choice of experimental protocol, some of the known systematic problems of the method of surrogate data testing are circumvented to obtain results to support the conclusions to a high level of significance
Missing physics in stick-slip dynamics of a model for peeling of an adhesive tape
It is now known that the equations of motion for the contact point during
peeling of an adhesive tape mounted on a roll introduced earlier are singular
and do not support dynamical jumps across the two stable branches of the peel
force function. By including the kinetic energy of the tape in the Lagrangian,
we derive equations of motion that support stick-slip jumps as a natural
consequence of the inherent dynamics. In the low mass limit, these equations
reproduce solutions obtained using a differential-algebraic algorithm
introduced for the earlier equations. Our analysis also shows that mass of the
ribbon has a strong influence on the nature of the dynamics.Comment: Accepted for publication in Phys. Rev. E (Rapid Communication
Relaxation oscillations and negative strain rate sensitivity in the Portevin - Le Chatelier effect
A characteristic feature of the Portevin - Le Chatelier effect or the jerky
flow is the stick-slip nature of stress-strain curves which is believed to
result from the negative strain rate dependence of the flow stress. The latter
is assumed to result from the competition of a few relevant time scales
controlling the dynamics of jerky flow. We address the issue of time scales and
its connection to the negative strain rate sensitivity of the flow stress
within the framework of a model for the jerky flow which is known to reproduce
several experimentally observed features including the negative strain rate
sensitivity of the flow stress. We attempt to understand the above issues by
analyzing the geometry of the slow manifold underlying the relaxational
oscillations in the model. We show that the nature of the relaxational
oscillations is a result of the atypical bent geometry of the slow manifold.
The analysis of the slow manifold structure helps us to understand the time
scales operating in different regions of the slow manifold. Using this
information we are able to establish connection with the strain rate
sensitivity of the flow stress. The analysis also helps us to provide a proper
dynamical interpretation for the negative branch of the strain rate
sensitivity.Comment: 7 figures, To appear in Phys. Rev.
Force-matched embedded-atom method potential for niobium
Large-scale simulations of plastic deformation and phase transformations in
alloys require reliable classical interatomic potentials. We construct an
embedded-atom method potential for niobium as the first step in alloy potential
development. Optimization of the potential parameters to a well-converged set
of density-functional theory (DFT) forces, energies, and stresses produces a
reliable and transferable potential for molecular dynamics simulations. The
potential accurately describes properties related to the fitting data, and also
produces excellent results for quantities outside the fitting range. Structural
and elastic properties, defect energetics, and thermal behavior compare well
with DFT results and experimental data, e.g., DFT surface energies are
reproduced with less than 4% error, generalized stacking-fault energies differ
from DFT values by less than 15%, and the melting temperature is within 2% of
the experimental value.Comment: 17 pages, 13 figures, 7 table
Multifractal burst in the spatio-temporal dynamics of jerky flow
The collective behavior of dislocations in jerky flow is studied in Al-Mg
polycrystalline samples subjected to constant strain rate tests. Complementary
dynamical, statistical and multifractal analyses are carried out on the
stress-time series recorded during jerky flow to characterize the distinct
spatio-temporal dynamical regimes. It is shown that the hopping type B and the
propagating type A bands correspond to chaotic and self-organized critical
states respectively. The crossover between these types of bands is identified
by a large spread in the multifractal spectrum. These results are interpreted
on the basis of competing scales and mechanisms.Comment: 4 pages, 6 figures To be published in Phys. Rev. Lett. (2001
Chaos or Noise - Difficulties of a Distinction
In experiments, the dynamical behavior of systems is reflected in time
series. Due to the finiteness of the observational data set it is not possible
to reconstruct the invariant measure up to arbitrary fine resolution and
arbitrary high embedding dimension. These restrictions limit our ability to
distinguish between signals generated by different systems, such as regular,
chaotic or stochastic ones, when analyzed from a time series point of view. We
propose to classify the signal behavior, without referring to any specific
model, as stochastic or deterministic on a certain scale of the resolution
, according to the dependence of the -entropy,
, and of the finite size Lyapunov exponent,
, on .Comment: 24 pages RevTeX, 9 eps figures included, two references added, minor
corrections, one section has been split in two (submitted to PRE
Two novel human cytomegalovirus NK cell evasion functions target MICA for lysosomal degradation
NKG2D plays a major role in controlling immune responses through the regulation of natural killer (NK) cells, αβ and γδ T-cell function. This activating receptor recognizes eight distinct ligands (the MHC Class I polypeptide-related sequences (MIC) A andB, and UL16-binding proteins (ULBP)1–6) induced by cellular stress to promote recognition cells perturbed by malignant transformation or microbial infection. Studies into human cytomegalovirus (HCMV) have aided both the identification and characterization of NKG2D ligands (NKG2DLs). HCMV immediate early (IE) gene up regulates NKGDLs, and we now describe the differential activation of ULBP2 and MICA/B by IE1 and IE2 respectively. Despite activation by IE functions, HCMV effectively suppressed cell surface expression of NKGDLs through both the early and late phases of infection. The immune evasion functions UL16, UL142, and microRNA(miR)-UL112 are known to target NKG2DLs. While infection with a UL16 deletion mutant caused the expected increase in MICB and ULBP2 cell surface expression, deletion of UL142 did not have a similar impact on its target, MICA. We therefore performed a systematic screen of the viral genome to search of addition functions that targeted MICA. US18 and US20 were identified as novel NK cell evasion functions capable of acting independently to promote MICA degradation by lysosomal degradation. The most dramatic effect on MICA expression was achieved when US18 and US20 acted in concert. US18 and US20 are the first members of the US12 gene family to have been assigned a function. The US12 family has 10 members encoded sequentially through US12–US21; a genetic arrangement, which is suggestive of an ‘accordion’ expansion of an ancestral gene in response to a selective pressure. This expansion must have be an ancient event as the whole family is conserved across simian cytomegaloviruses from old world monkeys. The evolutionary benefit bestowed by the combinatorial effect of US18 and US20 on MICA may have contributed to sustaining the US12 gene family
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