455 research outputs found
Development of an analytical technique for the optimization of jet engine and duct acoustic liners
A special integral representation of the external solutions of the Helmholtz equation is described. The analytical technique developed for the generation of the optimum acoustic admittance for an arbitrary axisymmetric body is also presented along with some numerical procedures and some preliminary results for a straight duct
Development of an analytical technique for the optimization of jet engine and duct acoustic liners
A new method was developed for the calculation of optimum constant admittance solutions for the minimization of the sound radiated from an arbitrary axisymmetric body. This method utilizes both the integral equation technique used in the calculation of the optimum non-constant admittance liners and the independent solution generated as a by product of these calculations. The results generated by both these methods are presented for three duct geometries: (1) a straight duct; (2) the QCSEE inlet; and (3) the QCSEE inlet less its centerbody
Hopping Parameter Series Construction for Models with Nontrivial Vacuum
Hopping parameter expansions are convergent power series. Under general
conditions they allow for the quantitative investigation of phase transition
and critical behaviour. The critical information is encoded in the high order
coefficients. Recently, 20th order computations have become feasible and used
for a large class of lattice field models both in finite and infinite volume.
They have been applied to quantum spin models and field theories at finite
temperature. The models considered are subject to a global symmetry
or to an even larger symmetry group such as O(N) with . In this paper
we are concerned with the technical details of series computations to allow for
a nontrivial vacuum expectation value , which is typical for
models that break a global symmetry. Examples are scalar fields
coupled to an external field, or manifestly gauge invariant effective models of
Higgs field condensates in the electroweak theory, even in the high temperature
phase. A nonvanishing tadpole implies an enormous proliferation of graphs and
limits the graphical series computation to the 10th order. To achieve the
hopping parameter series to comparable order as in the symmetric
case, the graphical expansion is replaced by an expansion into new algebraic
objects called vertex structures. In this way the 18th order becomes feasible.Comment: 19 pages, latex2
Dynamical Linked Cluster Expansions: A Novel Expansion Scheme for Point-Link-Point-Interactions
Dynamical linked cluster expansions are linked cluster expansions with
hopping parameter terms endowed with their own dynamics. This amounts to a
generalization from 2-point to point-link-point interactions. We develop an
associated graph theory with a generalized notion of connectivity and describe
an algorithmic generation of the new multiple-line graphs. We indicate physical
applications to spin glasses, partially annealed neural networks and SU(N)
gauge Higgs systems. In particular the new expansion technique provides the
possibility of avoiding the replica-trick in spin glasses. We consider
variational estimates for the SU(2) Higgs model of the electroweak phase
transition. The results for the transition line, obtained by dynamical linked
cluster expansions, agree quite well with corresponding high precision Monte
Carlo results.Comment: 41 pages, latex2e, 10 postscript figure
Prediction of sound radiation from different practical jet engine inlets
Computer codes which were based upon a special integral representation of the external solutions of the Helmholtz equation were upgraded so that they would yield accurate results for the acoustic radiation patterns in the field surrounding an axisymmetric body for nondimensional wave numbers, based on duct radius, of up to twenty. The accuracy of these computer programs was checked by the use of the point source method for the generation of exact solutions and then by comparison with the results of other experimental and theoretical studies. These computer codes were used in a parametric study of the dependence of the radiated sound field on input modal distribution, wave number, and inlet lip shape. The results of this study show that: (1) as the wave number (i.e., cut off ratio) is increased for a given input modal distribution that the acoustic radiation peak moves towards the inlet centerline and becomes more compact (i.e., narrows); (2) as the input mode number is increased for a given cut off ratio the acoustic radiation peak moves away from the inlet centerline and becomes more compact
Prediction of sound radiation from different practical jet engine inlets
Computer codes, capable of producing accurate results for nondimensional wave numbers (based on duct radius) of up to 20, were developed and used to generate results for various other inlet configurations. Both reflection coefficients and radiation patterns were calculated by the integral solution procedure for the following five inlet configurations: the NASA Langley Bellmouth, the NASA Lewis JT-15D-1 ground test nacelle, and three hyperbolic inlets of 50, 70, and 90 degrees. Results obtained are compared with results from other experimental and theoretical studies
Deep Learning Development Environment in Virtual Reality
Virtual reality (VR) offers immersive visualization and intuitive
interaction. We leverage VR to enable any biomedical professional to deploy a
deep learning (DL) model for image classification. While DL models can be
powerful tools for data analysis, they are also challenging to understand and
develop. To make deep learning more accessible and intuitive, we have built a
virtual reality-based DL development environment. Within our environment, the
user can move tangible objects to construct a neural network only using their
hands. Our software automatically translates these configurations into a
trainable model and then reports its resulting accuracy on a test dataset in
real-time. Furthermore, we have enriched the virtual objects with
visualizations of the model's components such that users can achieve insight
about the DL models that they are developing. With this approach, we bridge the
gap between professionals in different fields of expertise while offering a
novel perspective for model analysis and data interaction. We further suggest
that techniques of development and visualization in deep learning can benefit
by integrating virtual reality
Enatiomerically pure hydroxycarboxylic acids: current approaches and future perspectives
The growing awareness of the importance of chirality in conjunction with biological activity has led to an increasing demand for efficient methods for the industrial synthesis of enantiomerically pure compounds. Polyhydroxyalkanotes (PHAs) are a family of polyesters consisting of over 140 chiral R-hydroxycarboxylic acids (R-HAs), representing a promising source for obtaining chiral chemicals from renewable carbon sources. Although some R-HAs have been produced for some time and certain knowledge of the production processes has been gained, large-scale production has not yet been possible. In this article, through analysis of the current advances in production of these acids, we present guidelines for future developments in biotechnological processes for R-HA productio
Application of Activated Charcoal in the Downstream Processing of Bacterial Olefinic Poly(3-hydroxyalkanoates)
Medium chain length poly(hydroxyalkanoates) (mcl-PHAs) are bacterial thermoplastic elastomers with a large potential in medical applications. The present study provides a novel process to isolate and purify poly([ R]3-hydroxy-w-undecenoate-co-3-hydroxy-w-nonenoate-co-3-hydroxy-w-heptenoate)
(PHUE) and poly([R]-3hydroxy-w-undecenoate-co-3-hydroxy-w-nonenoate-co-3-hydroxyoctanoate- co-3-hydroxy-w-heptenoate-co 3-hydroxyhexanoate) (PHOUE) from Pseudomonas putida species. Three different types of activated charcoal were compared with regard
to their capability to selectively remove impurities. The product 'Charcoal activated, powder, pure' from Merck was found to be most suitable. Using ethyl acetate as solvent, the polyesters were extracted from freeze-dried biomass at room temperature and simultaneously purified by addition
of activated charcoal at the beginning of the extraction. The period of extraction was one hour and the ratio solvent to biomass was 15:1 (vol/wt). After extraction, the solids were separated by pressure filtration through a metallic lace tissue. The filtrate was again passed through the previously
accumulated filter cake, followed by a second filtration through a 0.45 mm membrane to remove finest coal particles. The resulting filtrate was concentrated, thus yielding polyesters whose quality and yield depended on the quantity of activated charcoal applied. For highly pure PHUE and PHOUE
with low endotoxin levels, the optimum ratio of activated charcoal to solvent for extraction (V/V) was found to be 0.5 for PHUE and 0.25 for PHOUE. The yields with regard to the raw polymers amounted to 55 wt% for PHUE and 75 wt% for PHOUE, which are acceptable for polymers that can be used
for medical applications
Renormalization Group Flow in large N_c
We calculate renormalization group flow equations for the linear sigma-model
in large N_c approximation. The flow equations decouple and can be solved
analytically. The solution is equal to a self consistent solution of the NJL
model in the same approximation, which shows that flow equations are a
promising method to extend the calculation to higher order in 1/N_c. Including
explicit chiral symmetry breaking, the large N_c approximation describes
physics reasonably well. We further compare the analytic solution to the
usually used polynomial truncation and find consistency.Comment: 15 pages, 4 figures, submitted to Phys. Lett. B, added reference
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