48,491 research outputs found
Alternative conformal quantum mechanics
We investigate a one dimensional quantum mechanical model, which is invariant
under translations and dilations but does not respect the conventional
conformal invariance. We describe the possibility of modifying the conventional
conformal transformation such that a scale invariant theory is also invariant
under this new conformal transformation
Expert system development for probabilistic load simulation
A knowledge based system LDEXPT using the intelligent data base paradigm was developed for the Composite Load Spectra (CLS) project to simulate the probabilistic loads of a space propulsion system. The knowledge base approach provides a systematic framework of organizing the load information and facilitates the coupling of the numerical processing and symbolic (information) processing. It provides an incremental development environment for building generic probabilistic load models and book keeping the associated load information. A large volume of load data is stored in the data base and can be retrieved and updated by a built-in data base management system. The data base system standardizes the data storage and retrieval procedures. It helps maintain data integrity and avoid data redundancy. The intelligent data base paradigm provides ways to build expert system rules for shallow and deep reasoning and thus provides expert knowledge to help users to obtain the required probabilistic load spectra
Probabilistic load simulation: Code development status
The objective of the Composite Load Spectra (CLS) project is to develop generic load models to simulate the composite load spectra that are included in space propulsion system components. The probabilistic loads thus generated are part of the probabilistic design analysis (PDA) of a space propulsion system that also includes probabilistic structural analyses, reliability, and risk evaluations. Probabilistic load simulation for space propulsion systems demands sophisticated probabilistic methodology and requires large amounts of load information and engineering data. The CLS approach is to implement a knowledge based system coupled with a probabilistic load simulation module. The knowledge base manages and furnishes load information and expertise and sets up the simulation runs. The load simulation module performs the numerical computation to generate the probabilistic loads with load information supplied from the CLS knowledge base
Semimetalic graphene in a modulated electric potential
The -electronic structure of graphene in the presence of a modulated
electric potential is investigated by the tight-binding model. The low-energy
electronic properties are strongly affected by the period and field strength.
Such a field could modify the energy dispersions, destroy state degeneracy, and
induce band-edge states. It should be noted that a modulated electric potential
could make semiconducting graphene semimetallic, and that the onset period of
such a transition relies on the field strength. There exist infinite
Fermi-momentum states in sharply contrast with two crossing points (Dirac
points) for graphene without external fields. The finite density of states
(DOS) at the Fermi level means that there are free carriers, and, at the same
time, the low DOS spectrum exhibits many prominent peaks, mainly owing to the
band-edge states.Comment: 12pages, 5 figure
Universal scale factors relating mesonic fields and quark operators
Scale factor matrices relating mesonic fields in chiral Lagrangians and
quark-level operators of QCD sum-rules are shown to be constrained by chiral
symmetry, resulting in universal scale factors for each chiral nonet. Built
upon this interplay between chiral Lagrangians and QCD sum-rules, the scale
factors relating the isotriplet scalar mesons to their underlying quark
composite field were recently determined. It is shown that the same technique
when applied to isodoublet scalars reproduces the same scale factors,
confirming the universality property and further validating this connection
between chiral Lagrangians and QCD sum-rules which can have nontrivial impacts
on our understanding of the low-energy QCD, in general, and the physics of
scalar mesons in particular.Comment: 5 pages, 1 figure. arXiv admin note: text overlap with
arXiv:1909.0724
Biodegradable Polylactic Acid (PLA) Microstructures for Scaffold Applications
In this research, we present a simple and cost effective soft lithographic
process to fabricate PLA scaffolds for tissue engineering. In which, the
negative photoresist JSR THB-120N was spun on a glass subtract followed by
conventional UV lithographic processes to fabricate the master to cast the PDMS
elastomeric mold. A thin poly(vinyl alcohol) (PVA) layer was used as a mode
release such that the PLA scaffold can be easily peeled off. The PLA precursor
solution was then cast onto the PDMS mold to form the PLA microstructures.
After evaporating the solvent, the PLA microstructures can be easily peeled off
from the PDMS mold. Experimental results show that the desired microvessels
scaffold can be successfully transferred to the biodegradable polymer PLA.Comment: Submitted on behalf of EDA Publishing Association
(http://irevues.inist.fr/EDA-Publishing
In-plane Theory of Non-Sequential Triple Ionization
We describe first-principles in-plane calculations of non-sequential triple
ionization (NSTI) of atoms in a linearly polarized intense laser pulse. In a
fully classically correlated description, all three electrons respond
dynamically to the nuclear attraction, the pairwise e-e repulsions and the
laser force throughout the duration of a 780nm laser pulse. Nonsequential
ejection is shown to occur in a multi-electron, possibly multi-cycle and
multi-dimensional, rescattering sequence that is coordinated by a number of
sharp transverse recollimation impacts.Comment: 4 pages, 4 figure
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