1,929 research outputs found
The Coupled Cluster Method in Hamiltonian Lattice Field Theory
The coupled cluster or exp S form of the eigenvalue problem for lattice
Hamiltonian QCD (without quarks) is investigated. A new construction
prescription is given for the calculation of the relevant coupled cluster
matrix elements with respect to an orthogonal and independent loop space basis.
The method avoids the explicit introduction of gauge group coupling
coefficients by mapping the eigenvalue problem onto a suitable set of character
functions, which allows a simplified procedure. Using appropriate group
theoretical methods, we show that it is possible to set up the eigenvalue
problem for eigenstates having arbitrary lattice momentum and lattice angular
momentum.Comment: LaTeX, no figur
Image-based 3D Scene Reconstruction and Rescue Simulation Framework for Railway Accidents
Although the railway transport is regarded as a relatively safe transportation tool, many railway accidents have still happened worldwide. In this research, an image-based 3D scene reconstruction framework was proposed to help railway accident emergency rescues. Based on the improved constrained non-linear least square optimization, the framework can automatically model the accident scene with only one panorama in a short time. We embedded the self-developed global terrain module into the commercial visualization and physics engine, which makes the commercial engine can be used to render the static scene at anywhere and simulate the dynamic rescue process respectively. In addition, a Head Mounted Device (HMD) was integrated into this framework to allow users to verify their rescue plan and review previous railway accidents in an immersive environment
Improved Lattice Gauge Field Hamiltonian
Lepage's improvement scheme is a recent major progress in lattice ,
allowing to obtain continuum physics on very coarse lattices. Here we discuss
improvement in the Hamiltonian formulation, and we derive an improved
Hamiltonian from a lattice Lagrangian free of errors. We do this by
the transfer matrix method, but we also show that the alternative via Legendre
transformation gives identical results. We consider classical improvement,
tadpole improvement and also the structure of L{\"u}scher-Weisz improvement.
The resulting color-electric energy is an infinite series, which is expected to
be rapidly convergent. For the purpose of practical calculations, we construct
a simpler improved Hamiltonian, which includes only nearest-neighbor
interactions.Comment: 30 pages, LaTe
Nonlinear Dynamical Stability of Newtonian Rotating White Dwarfs and Supermassive Stars
We prove general nonlinear stability and existence theorems for rotating star
solutions which are axi-symmetric steady-state solutions of the compressible
isentropic Euler-Poisson equations in 3 spatial dimensions. We apply our
results to rotating and non-rotating white dwarf, and rotating high density
supermassive (extreme relativistic) stars, stars which are in convective
equilibrium and have uniform chemical composition. This paper is a continuation
of our earlier work ([28])
Synthesis of a novel monomer “DDTU-IDI” for the development of low-shrinkage dental resin composites
ObjectiveThe current dental resin composites often suffer from polymerization shrinkage, which can lead to microleakage and potentially result in recurring tooth decay. This study presents the synthesis of a novel monomer, (3,9-diethyl-1,5,7,11-tetraoxaspiro[5,5]undecane-3,9-diyl)bis(methylene) bis((2-(3-(prop-1-en-2-yl)phenyl)propan-2-yl)carbamate) (DDTU-IDI), and evaluates its effect in the formulation of low-shrinkage dental resin composites.MethodsDDTU-IDI was synthesized through a two-step reaction route, with the initial synthesis of the required raw material monomer 3,9-diethyl-3,9-dihydroxymethyl-1,5,7,11-tetraoxaspiro-[5,5] undecane (DDTU). The structures were confirmed using Fourier-transform infrared (FT-IR) spectroscopy and hydrogen nuclear magnetic resonance (1HNMR) spectroscopy. Subsequently, DDTU-IDI was incorporated into Bis-GMA-based composites at varying weight percentages (5, 10, 15, and 20 wt%). The polymerization reaction, degree of conversion, polymerization shrinkage, mechanical properties, physicochemical properties and biocompatibility of the low-shrinkage composites were thoroughly evaluated. Furthermore, the mechanical properties were assessed after a thermal cycling test with 10,000 cycles to determine the stability.ResultsThe addition of DDTU-IDI at 10, 15, and 20 wt% significantly reduced the polymerization volumetric shrinkage of the experimental resin composites, without compromising the degree of conversion, mechanical and physicochemical properties. Remarkably, at a monomer content of 20 wt%, the polymerization shrinkage was reduced to 1.83 ± 0.53%. Composites containing 10, 15, and 20 wt% DDTU-IDI exhibited lower water sorption and higher contact angle. Following thermal cycling, the composites exhibited no significant decrease in mechanical properties, except for the flexural properties.Significance. DDTU-IDI has favorable potential as a component which could produce volume expansion and increase rigidity in the development of low-shrinkage dental resin composites. The development of low-shrinkage composites containing DDTU-IDI appears to be a promising strategy for reducing polymerization shrinkage, thereby potentially enhancing the longevity of dental restorations
Deletion of murine choline dehydrogenase results in diminished sperm motility
Choline dehydrogenase (CHDH) catalyzes the conversion of choline to betaine, an important methyl donor and organic osmolyte. We have previously identified single nucleotide polymorphisms (SNPs) in the human CHDH gene that, when present, seem to alter the activity of the CHDH enzyme. These SNPs occur frequently in humans. We created a Chdh-/- mouse to determine the functional effects of mutations that result in decreased CHDH activity. Chdh deletion did not affect fetal viability or alter growth or survival of these mice. Only one of eleven Chdh-/- males was able to reproduce. Loss of CHDH activity resulted in decreased testicular betaine and increased choline and PCho concentrations. Chdh+/+ and Chdh-/- mice produced comparable amounts of sperm; the impaired fertility was due to diminished sperm motility in the Chdh-/- males. Transmission electron microscopy revealed abnormal mitochondrial morphology in Chdh-/- sperm. ATP content, total mitochondrial dehydrogenase activity and inner mitochondrial membrane polarization were all significantly reduced in sperm from Chdh -/- animals. Mitochondrial changes were also detected in liver, kidney, heart, and testis tissues. We suggest that men who have SNPs in CHDH that decrease the activity of the CHDH enzyme could have decreased sperm motility and fertility
The Trispectrum in the Multi-brid Inflation
The trispectrum is at least as important as the bispectrum and its size can
be characterized by two parameters and . In this short
paper, we focus on the Multi-brid inflation, in particular the two-brid
inflation model in arXiv.0805.0974, and find that is always
positive and roughly equals to for the low scale
inflation, but can be negative or positive and its order of magnitude
can be the same as that of or even largerComment: 12 pages; minor correction, refs added; further refs added, version
for publication in JCA
Solidification of Al alloys under electromagnetic pulses and characterization of the 3D microstructures under synchrotron x-ray tomography
A novel programmable electromagnetic pulse device was developed and used to study the solidification of Al-15 pct Cu and Al-35 pct Cu alloys. The pulsed magnetic fluxes and Lorentz forces generated inside the solidifying melts were simulated using finite element methods, and their effects on the solidification microstructures were characterized using electron microscopy and synchrotron X-ray tomography. Using a discharging voltage of 120 V, a pulsed magnetic field with the peak Lorentz force of ~1.6 N was generated inside the solidifying Al-Cu melts which were showed sufficiently enough to disrupt the growth of the primary Al dendrites and the Al2Cu intermetallic phases. The microstructures exhibit a strong correlation to the characteristics of the applied pulse, forming a periodical pattern that resonates the frequency of the applied electromagnetic field
Modeling of Thermodynamic Properties and Phase Equilibria for the Al-Sm Binary System
The thermodynamic properties and associated phase equilibria for the Al-Sm binary system are examined, and experimental results regarding the stability of the Al3Sm, Al11Sm3, and Al4Sm intermetallics are incorporated. In the analysis presented, the liquid phase is described using a three-species association model, the intermediate phases are treated as stoichiometric compounds, and the terminal phases are treated as solid solutions with a single sublattice model. In addition to the stable phases, thermodynamic descriptions of the metastable Al11Sm3-α and Al4Sm-γ phases are employed, and both stable and metastable phase equilibria are presented over the full composition range, providing a general model, which is consistent with available experimental data. Metastable liquidus curves are examined with respect to the observed crystallization behavior of amorphous Al-Sm alloys
Diagnostic for Dilaton Dark Energy
diagnostic can differentiate between different models of dark energy
without the accurate current value of matter density. We apply this geometric
diagnostic to dilaton dark energy(DDE) model and differentiate DDE model from
LCDM. We also investigate the influence of coupled parameter on the
evolutive behavior of with respect to redshift . According to the
numerical result of , we get the current value of equation of state
=-0.952 which fits the WMAP5+BAO+SN very well.Comment: 6 pages and 6 figures
- …