37,434 research outputs found
Material Characterization and Real-Time Wear Evaluation of Pistons and Cylinder Liners of the Tiger 131 Military Tank
Material characterisation and wear evaluation of the original and replacement pistons and cylinder-liners of Tiger 131 is reported. Original piston and cylinder-liner were operative in the Tigers’ engine during WWII. The replacement piston and cylinder-liner were used as substitutes and were obtained after failure in two hours of operation in the actual engine. Material characterisation revealed that the original piston was aluminium silicon hypereutectic alloy whereas the replacement piston was aluminium copper alloy with very low silicon content. Both original and replacement cylinder-liners consisted of mostly iron which is indicative of cast iron, a common material for this application. The replacement piston average surface roughness was found to be 9.09 μm while for replacement cylinder-liner it was 5.78 μm
A Conversation with Ulf Grenander
Ulf Grenander was born in Vastervik, Sweden, on July 23, 1923. He started his
undergraduate education at Uppsala University, and earned his B.A. degree in
1946, the Fil. Lic. degree in 1948 and the Fil. Dr. degree in 1950, all from
the University of Stockholm. His Ph.D. thesis advisor was Harald Cram\'{e}r.
Professor Grenander is well known for pathbreaking research in a number of
areas including pattern theory, computer vision, inference in stochastic
processes, probabilities on algebraic structures and actuarial mathematics. He
has published more than one dozen influential books, of which Statistical
Analysis of Stationary Time Series (1957, coauthored with M. Rosenblatt),
Probabilities on Algebraic Structures (1963; also in Russian) and Abstract
Inference (1981b) are regarded as classics. His three-volume lecture notes,
namely, Pattern Synthesis (vol. I, 1976), Pattern Analysis (vol. II, 1978) and
Regular Structures (vol. III, 1981a; also in Russian) created and nurtured a
brand new area of research. During 1951--1966, Professor Grenander's career
path took him to the University of Chicago (1951--1952), the University of
California--Berkeley (1952--1953), the University of Stockholm (1953--1957),
Brown University (1957--1958) and the Institute for Insurance Mathematics and
Mathematical Statistics (1958--1966) as its Professor and Director. From 1966
until his retirement he was L. Herbert Ballou University Professor at Brown
University. Professor Grenander also held the position of Scientific Director
(1971--1973) of the Swedish Institute of Applied Mathematics. He has earned
many honors and awards, including Arhennius Fellow (1948), Fellow of the
Institute of Mathematical Statistics (1953), Prize of the Nordic Actuaries
(1961), Arnberger Prize of the Royal Swedish Academy of Science (1962), Member
of the Royal Swedish Academy of Science (1965), Guggenheim Fellowship (1979)
and Honorary Fellow of the Royal Statistical Society, London (1989). He has
delivered numerous prestigious lectures, including the Rietz Lecture (1985),
the Wald Lectures (1995) and the Mahalanobis Lecture (2004). Professor
Grenander received an Honorary D.Sc. degree (1993) from the University of
Chicago and is a Fellow of both the American Academy of Arts and Sciences
(1995) and the National Academy of Sciences, U.S.A. (1998). Professor
Grenander's career, life, passion and hobbies can all be summarized by one
simple word: Mathematics.Comment: Published at http://dx.doi.org/10.1214/088342305000000313 in the
Statistical Science (http://www.imstat.org/sts/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Automatic Spatial Calibration of Ultra-Low-Field MRI for High-Accuracy Hybrid MEG--MRI
With a hybrid MEG--MRI device that uses the same sensors for both modalities,
the co-registration of MRI and MEG data can be replaced by an automatic
calibration step. Based on the highly accurate signal model of ultra-low-field
(ULF) MRI, we introduce a calibration method that eliminates the error sources
of traditional co-registration. The signal model includes complex sensitivity
profiles of the superconducting pickup coils. In ULF MRI, the profiles are
independent of the sample and therefore well-defined. In the most basic form,
the spatial information of the profiles, captured in parallel ULF-MR
acquisitions, is used to find the exact coordinate transformation required. We
assessed our calibration method by simulations assuming a helmet-shaped
pickup-coil-array geometry. Using a carefully constructed objective function
and sufficient approximations, even with low-SNR images, sub-voxel and
sub-millimeter calibration accuracy was achieved. After the calibration,
distortion-free MRI and high spatial accuracy for MEG source localization can
be achieved. For an accurate sensor-array geometry, the co-registration and
associated errors are eliminated, and the positional error can be reduced to a
negligible level.Comment: 11 pages, 8 figures. This work is part of the BREAKBEN project and
has received funding from the European Union's Horizon 2020 research and
innovation programme under grant agreement No 68686
Quark mass dependence of baryon properties
I discuss the quark mass dependence of various baryon properties derived from
chiral perturbation theory. Such representations can eventually be used as
chiral extrapolation functions when lattice data at sufficiently small quark
masses become available. The quark mass dependence is encoded in loop and
contact term contributions, the latter given in terms of low-energy constants.
I stress the importance of utilizing phenomenological input to constrain a
certain class of low-energy constants and discuss the ensuing theoretical
uncertainty for various baryon observables, like the nucleon and the baryon
octet masses, the nucleon isovector anomalous magnetic moment and the
axial-vector coupling of the nucleon. I stress the role of resonance decoupling
and present first results for the delta mass based on an effective field theory
in which the nucleon-delta mass splitting is counted as a small parameter. I
also discuss briefly the pion mass dependence of the nuclear force as derived
from chiral nuclear effective field theory.Comment: 21 pp, PoS style, plenary talk at Lattice 2005, Trinity College,
Dublin, Irland, 25th-30th July 200
Double neutral pion photoproduction at threshold
We consider the chiral expansion of the threshold amplitude for the reaction
to order . We substantiate a
claim that this photoproduction channel is significantly enhanced close to
threshold due to pion loops. A precise measurement of the corresponding cross
sections is called for which allows to test chiral perturbation theory.Comment: 8 pp, LaTe
Chiral Extrapolations and the Covariant Small Scale Expansion
We calculate the nucleon and the delta mass to fourth order in a covariant
formulation of the small scale expansion. We analyze lattice data from the MILC
collaboration and demonstrate that the available lattice data combined with our
knowledge of the physical values for the nucleon and delta masses lead to
consistent chiral extrapolation functions for both observables up to fairly
large pion masses. This holds in particular for very recent data on the delta
mass from the QCDSF collaboration. The resulting pion-nucleon sigma term is
sigma_{piN} = 48.9 MeV. This first quantitative analysis of the quark-mass
dependence of the structure of the Delta(1232) in full QCD within chiral
effective field theory suggests that (the real part of) the nucleon-delta
mass-splitting in the chiral limit, Delta_0 = 0.33 GeV, is slightly larger than
at the physical point. Further analysis of simultaneous fits to nucleon and
delta lattice data are needed for a precision determination of the properties
of the first excited state of the nucleon.Comment: 11 pp, 2 figs, version accepted for publication in Phys. Lett.
Large time wellposdness to the 3-D Capillary-Gravity Waves in the long wave regime
In the regime of weakly transverse long waves, given long-wave initial data,
we prove that the nondimensionalized water wave system in an infinite strip
under influence of gravity and surface tension on the upper free interface has
a unique solution on [0,{T}/\eps] for some \eps independent of constant
We shall prove in the subsequent paper \cite{MZZ2} that on the same time
interval, these solutions can be accurately approximated by sums of solutions
of two decoupled Kadomtsev-Petviashvili (KP) equations.Comment: Split the original paper(The long wave approximation to the 3-D
capillary-gravity waves) into two parts, this is the first on
The chiral effective pion-nucleon Lagrangian of order p^4
We construct the minimal effective chiral pion-nucleon SU(2) Lagrangian at
fourth order in the chiral expansion. The Lagrangian contains 118 in principle
measurable terms. We develop both the relativistic as well as the heavy baryon
formulation of the effective field theory. For the latter, we also work out
explicitly all 1/m corrections at fourth order. We display all relevant
relations needed to find the linearly independent terms.Comment: 30 pp, LaTeX2e, coefficients of three third order 1/m^2 corrections
proportional to F_{\mu\nu}^+ corrected in eq.(3.8) and table
Octet Baryon Charge Radii, Chiral Symmetry and Decuplet Intermediate States
We compute the octet baryon charge radii to O(1/Heavy^3) in heavy baryon
chiral perturbation theory. We examine the effect of including the decuplet of
spin-3/2 baryons explicitly. We find that it does no t improve the level of
agreement between the HBchiPT and experimental values for the Sigma^- charge
radius.Comment: 9 pages, 2 figures. Uses axodraw.sty, include
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