450 research outputs found
Comparison of three-dimensional facial morphology between upright and supine positions employing three-dimensional scanner from live subjects
Facial soft tissue thicknesses (FSTT) measurements collected from Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) imaging techniques are most commonly taken in the supine position for forensic craniofacial reconstruction. FSTT have been shown to be different in comparison to the upright position due to gravity. The variation of facial morphology between the upright and supine position of laser-scanned images taken from 44 individuals was investigated using volumetric analysis with deviation maps. Between 82.4% and 86.7% of the facial surface area were within the error range of ±2 mm between the supine and the upright position. This indicates that most anatomical landmarks taken from the MRI and CT data can be an accurate representative of the FSTT in the upright position. Seven landmarks located around the buccal region, masseteric region and the nasolabial region of the face showed the greatest FSTT deviation between the upright and supine position, thus these landmarks may affect the accuracy of facial reconstructions when using a CT or MRI database
Coupling of winding models and roll quality instruments
Winding models have been under development for roughly 50 years. These models have become mature in their ability to predict the internal residual stresses within a wound roll as a function of winder type, winder operating parameters, web and core material parameters and non-uniformity inherent in the web. The internal stresses are useful when predicting winding defects. The majority of the instruments that have been developed to infer the quality of rolls wound in production environments are dynamic hardness testers that provide output in unique units. These devices are very useful in the production environment for studying cross machine direction (CMD) variation of hardness in wound rolls. This variation could have resulted independently from web tension, nip load, web thickness, modulus or length non-uniformity in the CMD. It could also have resulted from combined non-uniformity from all of these sources but hardness testers have no means to determine the source of hardness variation. The coupling of winding models and dynamic roll hardness testers will move roll quality improvement to an advanced diagnostic level. We will demonstrate that it has become possible for winding models which have been extended with dynamic impact models to provide estimates of hardness in the unique units of any test instrument. Our goal is to promote improvement in roll quality by the combined use of winding models and dynamic hardness testers to minimize wound roll defects.Mechanical and Aerospace Engineerin
Wavelet Methods in the Relativistic Three-Body Problem
In this paper we discuss the use of wavelet bases to solve the relativistic
three-body problem. Wavelet bases can be used to transform momentum-space
scattering integral equations into an approximate system of linear equations
with a sparse matrix. This has the potential to reduce the size of realistic
three-body calculations with minimal loss of accuracy. The wavelet method leads
to a clean, interaction independent treatment of the scattering singularities
which does not require any subtractions.Comment: 14 pages, 3 figures, corrected referenc
Prediction of nasal morphology in facial reconstruction: Validation and recalibration of the Rynn method
Background
Prediction of the nose from the skull remains an important issue in forensic facial approximation. In 2010, Rynn et al. published a method of predicting nose projection from the skull. With this method, three craniometric measurements (x, y, z) are taken, and these are then used in regression formulae to estimate the nasal dimensions.
Aim
The purpose of this study was to examine and test the accuracy of the Rynn et al. method and if necessary to adapt the formulae for this population.
Subjects and methods
A sample of 90 CT scans of Turkish adults was used in the study. The actual and predicted dimensions were compared using t-test. The age of the individuals ranged from 20 to 40 years by sex.
Results
The descriptive statistics and correlations were calculated, and the actual and predicted measurements were compared. The differences between the actual and predicted values were statistically significant (p < 0.01), with −1 mm for males and −1.5 mm for females. Validation accuracies ranged from 76 to 92% in females and 72 to 82% in males. Recalibration equation accuracies ranged from 88 to 100% in females and 90 to 100% in males.
Conclusion
The results showed that the recalibration of the Rynn et al. method and its formulae gave satisfactory results with less error and can be employed in facial approximation cases
Hole-hole superconducting pairing in the t-J model induced by spin-wave exchange
We study numerically the hole pairing induced by spin-wave exchange. The
contact hole-hole interaction is taken into account as well. It is assumed that
antiferromagnetic order is preserved at all scales relevant to pairing. The
strongest pairing is obtained for the d-wave symmetry of the gap. Dependence of
the value of the gap on hole concentration and temperature is presented. For
the critical temperature we obtain Tc about 100 K at the hole concentration
delta = 0.2-0.3.Comment: replaced with a revised version to appear in PRB, 6 pages, REVTeX
3.0, figures not change
Magnetic impurities coupled to quantum antiferromagnets in one dimension
Magnetic impurities coupled antiferromagnetically to a one-dimensional
Heisenberg model are studied by numerical diagonalization of chains of finite
clusters. By calculating the binding energy and the correlation function, it is
shown that a local singlet develops around each impurity. This holds true for
systems with a single impurity, with two impurities, and for impurities forming
a lattice. The local character of the singlet is found to be little affected by
the presence of other impurity spins. A small effective interaction is found
between a pair of impurity spins, which oscillates depending on impurity
distances. For impurity lattices, the energy spectrum shows a gap which is
found to be much smaller than the binding energy per impurity if the coupling
constants are small. For larger coupling constants, it increases to the same
order of magnitude as the binding energy, indicating that a local singlet is
broken to create excited states. Impurity lattices with ferromagnetic couplings
are also studied and their connection to the Haldane problem is discussed.Comment: 25 pages, plain TeX, 17 figures available on request, to be publised
in Phys. Rev.
New times of minima of some eclipsing binary stars
We present several CCD minima observations of eclipsing binaries
Superconductivity and spin triplet collective mode in the t-J model close to antiferromagnetic instability
To investigate relations between long-range antiferromagnetic (AF) order,
superconductivity and two particle triplet collective excitations we consider a
modified two dimensional t-J model at doping close to half filling. The model
includes additional hopping t'' and nearest sites Coulomb repulsion V. The
additional parameters allow us to control closeness of the system to the AF
instability. We demonstrate the possibility of co-existence of long-range AF
order and d-g-wave superconductivity. In the phase with long-range AF order we
find, analytically, superconducting gaps and spin wave renormalization. We
demonstrate that at approaching the point of the AF instability the spin
triplet collective excitation arises with energy below the superconducting gap.Comment: 9 page
Fermi Liquid Damping and NMR Relaxation in Superconductors
Electron collisions for a two dimensional Fermi liquid (FL) are shown to give
a quasiparticle damping with interesting frequency and temperature variations
in the BCS superconducting state. The spin susceptibility which determines the
structure of the damping is analyzed in the normal state for a Hubbard model
with a constant on--site Coulomb repulsion. This is then generalized to the
superconducting state by including coherence factors and self energy and vertex
corrections. Calculations of the NMR relaxation rate reveal that the FL damping
structure can reduce the Hebel--Slichter peak, in agreement with data on the
organic superconductor (MDT-TTF)AuI. However, the strongly suppressed
FL damping in the superconducting state does not eliminate the Hebel-Slichter
peak, and thus suggests that other mechanisms are needed to explain the NMR
data on (TMTSF)ClO, the BEDT organic compounds, and cuprate
superconductors. Predictions of the temperature variation of the damping and
the spin response are given over a wide frequency range as a guide to
experimental probes of the symmetry of the superconducting pairs.Comment: 10 pages, RevTeX 3.0, 9 figures in uuencoded postscrip
Control of Superconducting Correlations in High-Tc Cuprates
A strategy to enhance d-wave superconducting correlations is proposed based
on our numerical study for correlated electron models for high-Tc cuprates. We
observe that the pairing is enhanced when the single-electron level around
(pi,0) is close to the Fermi level E_F, while the d-wave pairing interaction
itself contains elements to disfavor the pairing due to shift of the
(pi,0)-level. Angle-resolved photoemission results in the cuprates are
consistently explained in the presence of the d-wave pairing interaction. Our
proposal is the tuning of the (pi,0)-level under the many-body effects to E_F
by optimal design of band structure.Comment: 4 pages, 6 eps figure
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