157 research outputs found
On neural networks in identification and control of dynamic systems
This paper presents a discussion of the applicability of neural networks in the identification and control of dynamic systems. Emphasis is placed on the understanding of how the neural networks handle linear systems and how the new approach is related to conventional system identification and control methods. Extensions of the approach to nonlinear systems are then made. The paper explains the fundamental concepts of neural networks in their simplest terms. Among the topics discussed are feed forward and recurrent networks in relation to the standard state-space and observer models, linear and nonlinear auto-regressive models, linear, predictors, one-step ahead control, and model reference adaptive control for linear and nonlinear systems. Numerical examples are presented to illustrate the application of these important concepts
Pair-Linking for Collective Entity Disambiguation: Two Could Be Better Than All
Collective entity disambiguation aims to jointly resolve multiple mentions by
linking them to their associated entities in a knowledge base. Previous works
are primarily based on the underlying assumption that entities within the same
document are highly related. However, the extend to which these mentioned
entities are actually connected in reality is rarely studied and therefore
raises interesting research questions. For the first time, we show that the
semantic relationships between the mentioned entities are in fact less dense
than expected. This could be attributed to several reasons such as noise, data
sparsity and knowledge base incompleteness. As a remedy, we introduce MINTREE,
a new tree-based objective for the entity disambiguation problem. The key
intuition behind MINTREE is the concept of coherence relaxation which utilizes
the weight of a minimum spanning tree to measure the coherence between
entities. Based on this new objective, we design a novel entity disambiguation
algorithms which we call Pair-Linking. Instead of considering all the given
mentions, Pair-Linking iteratively selects a pair with the highest confidence
at each step for decision making. Via extensive experiments, we show that our
approach is not only more accurate but also surprisingly faster than many
state-of-the-art collective linking algorithms
Simple and Effective Curriculum Pointer-Generator Networks for Reading Comprehension over Long Narratives
This paper tackles the problem of reading comprehension over long narratives
where documents easily span over thousands of tokens. We propose a curriculum
learning (CL) based Pointer-Generator framework for reading/sampling over large
documents, enabling diverse training of the neural model based on the notion of
alternating contextual difficulty. This can be interpreted as a form of domain
randomization and/or generative pretraining during training. To this end, the
usage of the Pointer-Generator softens the requirement of having the answer
within the context, enabling us to construct diverse training samples for
learning. Additionally, we propose a new Introspective Alignment Layer (IAL),
which reasons over decomposed alignments using block-based self-attention. We
evaluate our proposed method on the NarrativeQA reading comprehension
benchmark, achieving state-of-the-art performance, improving existing baselines
by relative improvement on BLEU-4 and relative improvement on
Rouge-L. Extensive ablations confirm the effectiveness of our proposed IAL and
CL components.Comment: Accepted to ACL 201
A tidal lung simulation to quantify lung heterogeneity with the Inspired Sinewave Test
We have created a lung simulation to quantify lung heterogeneity from the
results of the inspired sinewave test (IST). The IST is a lung function test
that is non-invasive, non-ionising and does not require patients' cooperation.
A tidal lung simulation is developed to assess this test and also a method is
proposed to calculate lung heterogeneity from IST results. A sensitivity
analysis based on the Morris method and linear regression were applied to
verify and to validate the simulation. Additionally, simulated emphysema and
pulmonary embolism conditions were created using the simulation to assess the
ability of the IST to identify these conditions. Experimental data from five
pigs (pre-injured vs injured) were used for validation. This paper contributes
to the development of the IST. Firstly, our sensitivity analysis reveals that
the IST is highly accurate with an underestimation of about 5% of the simulated
values. Sensitivity analysis suggested that both instability in tidal volume
and extreme expiratory flow coefficients during the test cause random errors in
the IST results. Secondly, the ratios of IST results obtained at two tracer gas
oscillation frequencies can identify lung heterogeneity (ELV60/ELV180 and
Qp60/Qp180). There was dissimilarity between simulated emphysema and pulmonary
embolism (p < 0:0001). In the animal model, the control group had ELV60/ELV180
= 0.58 compared with 0.39 in injured animals (p < 0.0001)
Flexural-strengthening efficiency of cfrp sheets for unbonded post-tensioned concrete T-beams
There has been a limited number of studies about the flexural behavior of unbonded post-tensioned concrete (UPC) beams strengthened with carbon fibre reinforced polymer (CFRP) and these studies have not systematically examined the effect of CFRP sheets on the tendon strain as well as the strengthening efficiency. Moreover, current design guides for the FRP strengthening techniques have not provided any design procedure for UPC structures. This study, thus, investigates the influence of CFRP sheet ratio on the flexural behavior of CFRP-strengthened UPC T-beams and quantifies its effect upon tendon behavior in this kind of UPC beams. The testing program consisted of nine large-scale UPC T-beams strengthened by different layers of CFRP sheets with or without CFRP U-wrapped anchors. The experimental results have shown that the use of CFRP sheets and CFRP U-wrapped anchors significantly affected the tendon strain. The FRP reinforcement ratio governed the flexural capacity, the crack width, the mid-span displacement, and the ductility of the beams in which the strengthening efficiency reduces with the increased number of CFRP layers. The configuration of the CFRP U-wrapped anchors affected the strain of the CFRP sheets, the failure mode and thus the beam behavior. In addition, semi-empirical equations were proposed to estimate the actual strain of unbonded tendons in which the effect of the CFRP sheets and CFRP U-wrapped anchors have been taken into consideration. The proposed equations, which are simple to use, yield reliable predictions with a small variation
L-SeqSleepNet: Whole-cycle Long Sequence Modelling for Automatic Sleep Staging
Human sleep is cyclical with a period of approximately 90 minutes, implying
long temporal dependency in the sleep data. Yet, exploring this long-term
dependency when developing sleep staging models has remained untouched. In this
work, we show that while encoding the logic of a whole sleep cycle is crucial
to improve sleep staging performance, the sequential modelling approach in
existing state-of-the-art deep learning models are inefficient for that
purpose. We thus introduce a method for efficient long sequence modelling and
propose a new deep learning model, L-SeqSleepNet, which takes into account
whole-cycle sleep information for sleep staging. Evaluating L-SeqSleepNet on
four distinct databases of various sizes, we demonstrate state-of-the-art
performance obtained by the model over three different EEG setups, including
scalp EEG in conventional Polysomnography (PSG), in-ear EEG, and around-the-ear
EEG (cEEGrid), even with a single EEG channel input. Our analyses also show
that L-SeqSleepNet is able to alleviate the predominance of N2 sleep (the major
class in terms of classification) to bring down errors in other sleep stages.
Moreover the network becomes much more robust, meaning that for all subjects
where the baseline method had exceptionally poor performance, their performance
are improved significantly. Finally, the computation time only grows at a
sub-linear rate when the sequence length increases.Comment: 9 pages, 4 figures, updated affiliation
Prognosis of neonatal tetanus in the modern management era: an observational study in 107 Vietnamese infants.
OBJECTIVES: Most data regarding the prognosis in neonatal tetanus originate from regions where limited resources have historically impeded management. It is not known whether recent improvements in critical care facilities in many low- and middle-income countries have affected indicators of a poor prognosis in neonatal tetanus. We aimed to determine the factors associated with worse outcomes in a Vietnamese hospital with neonatal intensive care facilities. METHODS: Data were collected from 107 cases of neonatal tetanus. Clinical features on admission were analyzed against mortality and a combined endpoint of 'death or prolonged hospital stay'. RESULTS: Multivariable analysis showed that only younger age (odds ratio (OR) for mortality 0.69, 95% confidence interval (CI) 0.48-0.98) and lower weight (OR for mortality 0.06, 95% CI 0.01-0.54) were significantly associated with both the combined endpoint and death. A shorter period of onset (OR 0.94, 95% CI 0.88-0.99), raised white cell count (OR 1.17, 95% CI 1.02-1.35), and time between first symptom and admission (OR 3.77, 95% CI 1.14-12.51) were also indicators of mortality. CONCLUSIONS: Risk factors for a poor outcome in neonatal tetanus in a setting with critical care facilities include younger age, lower weight, delay in admission, and leukocytosis
The Emergence of Rotavirus G12 and the Prevalence of Enteric Viruses in Hospitalized Pediatric Diarrheal Patients in Southern Vietnam
Diarrhea is a major cause of childhood morbidity and mortality in developing countries, and the majority of infections are of viral etiology. We aimed to compare the etiological prevalence of the major enteric viruses in an urban and a rural setting in southern Vietnam. We simultaneously screened fecal specimens from 362 children in Ho Chi Minh City and Dong Thap province that were hospitalized with acute diarrhea over a 1-month-long period for four viral gastrointestinal pathogens. Rotavirus was the most common pathogen identified, but there was a differential prevalence of rotavirus and norovirus between the urban and rural locations. Furthermore, rotavirus genotyping and phylogenetic analysis again differentiated the genotypes by the sampling location. Our data show a disproportional distribution of enteric viral pathogens in urban and rural locations, and we provide evidence of continual importation of new rotavirus strains into southern Vietnam and report the emergence of rotavirus genotype G12
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