6,061 research outputs found
Bypass rod transfers heat developed in thermionic diode
In a thermionic diode, a cesium tube joining the emitter-collector area and the cesium reservoir is fitted with a copper bypass rod held in place by two standoff brackets. The rod transfers heat from the emitter-collector to the reservoir without going through the ceramic seal structure which surrounds the cesium tube and cannot sustain large temperature gradients
IWO-based Synthesis of Log-Periodic Dipole Array
The Invasive Weed Optimization (IWO) is an
effective evolutionary and recently developed method. Due to its
better performance in comparison to other well-known
optimization methods, IWO has been chosen to solve many
complex non-linear problems in telecommunications and
electromagnetics. In the present study, the IWO is applied to
optimize the geometry of a realistic log-periodic dipole array
(LPDA) that operates in the frequency range 800-3300 MHz and
therefore is suitable for signal reception from several RF services.
The optimization is applied under specific requirements,
concerning the standing wave ratio, the forward gain, the gain
flatness and the side lobe level, over a wide frequency range. The
optimization variables are the lengths and the radii of the dipoles,
the distances between them, and the characteristic impedance of
the transmission line that connects the dipoles. The optimized
LPDA seems to be superior compared to the antenna derived
from the practical design procedure
Speech vocoding for laboratory phonology
Using phonological speech vocoding, we propose a platform for exploring
relations between phonology and speech processing, and in broader terms, for
exploring relations between the abstract and physical structures of a speech
signal. Our goal is to make a step towards bridging phonology and speech
processing and to contribute to the program of Laboratory Phonology. We show
three application examples for laboratory phonology: compositional phonological
speech modelling, a comparison of phonological systems and an experimental
phonological parametric text-to-speech (TTS) system. The featural
representations of the following three phonological systems are considered in
this work: (i) Government Phonology (GP), (ii) the Sound Pattern of English
(SPE), and (iii) the extended SPE (eSPE). Comparing GP- and eSPE-based vocoded
speech, we conclude that the latter achieves slightly better results than the
former. However, GP - the most compact phonological speech representation -
performs comparably to the systems with a higher number of phonological
features. The parametric TTS based on phonological speech representation, and
trained from an unlabelled audiobook in an unsupervised manner, achieves
intelligibility of 85% of the state-of-the-art parametric speech synthesis. We
envision that the presented approach paves the way for researchers in both
fields to form meaningful hypotheses that are explicitly testable using the
concepts developed and exemplified in this paper. On the one hand, laboratory
phonologists might test the applied concepts of their theoretical models, and
on the other hand, the speech processing community may utilize the concepts
developed for the theoretical phonological models for improvements of the
current state-of-the-art applications
Distribution Dynamics of Dietary Energy Supply in the World
This paper investigates the law of motion for the cross-section distribution of dietary energy supply (DES) in the world. This has been pursued using the distribution approach and a panel of 152 countries for the period 1961-2001. According to the empirical results, persistence in caloric intakes dominates in the short-run. With time, however, upwards mobility gains momentum and the world is moving towards a long-run distribution, which is strongly skewed to the left. The estimated expected first passage times from extreme under-supply to higher intake levels are consistent with speculations that most of the developing countries will attain the 3000 kcal per person per day level by the year 2030.caloric intakes, mobility, World, Food Consumption/Nutrition/Food Safety, C10, D12,
A model of nutrition information search with an application to food labels
Due to the dramatic rise of several diet-related chronic diseases, nutrition information search behaviours have received significant interest from both the scientific and non-scientific literature. No other known paper in economics, however, has examined from a theoretical perspective the acquisition of nutrition information as a health enhancing activity. We modify the standard health capital model (Grossman, 1972) to allow the time spent on nutrition information search to be considered within the context of a time allocation decision. We then collected extensive primary data based on the theoretical model and used these to test the model.nutrition information, food labels, health production
Static and dynamic behavior of multiplex networks under interlink strength variation
It has recently been suggested \cite{Radicchi2013} that in a two-level
multiplex network, a gradual change in the value of the "interlayer" strength
can provoke an abrupt structural transition. The critical point at
which this happens is system-dependent. In this article, we show in a similar
way as in \cite{Garrahan2014} that this is a consequence of the graph Laplacian
formalism used in \cite{Radicchi2013}. We calculate the evolution of as
a function of system size for ER and RR networks. We investigate the behavior
of structural measures and dynamical processes of a two-level system as a
function of , by Monte-Carlo simulations, for simple particle diffusion and
for reaction-diffusion systems. We find that as increases there is a smooth
transition from two separate networks to a single one. We cannot find any
abrupt change in static or dynamic behavior of the underlying system.Comment: 8 pages, 5 figure
Six-converter solar thermionic generator Final report, 10 Jan. 1967 - 31 Mar. 1968
Six converter solar thermionic generato
Design of a Novel Antenna Array Beamformer Using Neural Networks Trained by Modified Adaptive Dispersion Invasive Weed Optimization Based Data
A new antenna array beamformer based on neural networks (NNs) is presented. The NN training is performed by using optimized data sets extracted by a novel Invasive Weed Optimization (IWO) variant called Modified Adaptive Dispersion IWO (MADIWO). The trained NN is utilized as an adaptive beamformer that makes a uniform linear antenna array steer the main lobe towards a desired signal, place respective nulls towards several interference signals and suppress the side lobe level (SLL). Initially, the NN structure is selected by training several NNs of various structures using MADIWO based data and by making a comparison among the NNs in terms of training performance. The selected NN structure is then used to construct an adaptive beamformer, which is compared to MADIWO based and ADIWO based beamformers, regarding the SLL as well as the ability to properly steer the main lobe and the nulls. The comparison is made considering several sets of random cases with different numbers of interference signals and different power levels of additive zero-mean Gaussian noise. The comparative results exhibit the advantages of the proposed beamformer
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