643 research outputs found
Spectral-spatial classification of hyperspectral images: three tricks and a new supervised learning setting
Spectral-spatial classification of hyperspectral images has been the subject
of many studies in recent years. In the presence of only very few labeled
pixels, this task becomes challenging. In this paper we address the following
two research questions: 1) Can a simple neural network with just a single
hidden layer achieve state of the art performance in the presence of few
labeled pixels? 2) How is the performance of hyperspectral image classification
methods affected when using disjoint train and test sets? We give a positive
answer to the first question by using three tricks within a very basic shallow
Convolutional Neural Network (CNN) architecture: a tailored loss function, and
smooth- and label-based data augmentation. The tailored loss function enforces
that neighborhood wavelengths have similar contributions to the features
generated during training. A new label-based technique here proposed favors
selection of pixels in smaller classes, which is beneficial in the presence of
very few labeled pixels and skewed class distributions. To address the second
question, we introduce a new sampling procedure to generate disjoint train and
test set. Then the train set is used to obtain the CNN model, which is then
applied to pixels in the test set to estimate their labels. We assess the
efficacy of the simple neural network method on five publicly available
hyperspectral images. On these images our method significantly outperforms
considered baselines. Notably, with just 1% of labeled pixels per class, on
these datasets our method achieves an accuracy that goes from 86.42%
(challenging dataset) to 99.52% (easy dataset). Furthermore we show that the
simple neural network method improves over other baselines in the new
challenging supervised setting. Our analysis substantiates the highly
beneficial effect of using the entire image (so train and test data) for
constructing a model.Comment: Remote Sensing 201
Descreening of Color Halftone Images in the Frequency Domain
Scanning a halftone image introduces halftone artifacts, known as Moiré patterns, which significantly degrade the image quality. Printers that use amplitude modulation (AM) screening for halftone printing position dots in a periodic pattern. Therefore, frequencies relating halftoning are easily identifiable in the frequency domain. This paper proposes a method for descreening scanned color halftone images using a custom band reject filter designed to isolate and remove only the frequencies related to halftoning while leaving image edges sharp without image segmentation or edge detection. To enable hardware acceleration, the image is processed in small overlapped windows. The windows are filtered individually in the frequency domain, then pieced back together in a method that does not show blocking artifacts
Barriers to the adoption of renewable and energy-efficient technologies in the Vietnamese power sector
This paper examines the major barriers to the deployment of geothermal, small hydro and advanced coal power generation technologies in Vietnam. It ranks their severity by applying the analytical hierarchy process to data from a survey of 37 domestic experts and stakeholders. Key barriers to a wider penetration of small hydro generation technologies are insufficient capital, a lack of domestic suppliers and unsatisfactory government policies. Barriers to geothermal power are related to information and awareness problems, a lack of R&D and industrial capability, a weak policy framework and the remoteness of geothermal sites. For advanced coal power technologies, the barriers are weak industrial capability, high cost and a lack of technical knowledge. The experts consulted in this study view changes in government actions as the key to overcoming the abovementioned barriers. They recommend investing more in R&D activities, improving R&D capacity through joint-venture schemes and reforming investment policy/legislation for the electric power industry as the most appropriate solutions.analytical hierarchy process; renewables; energy efficient technologies.
Fostering Cooperation in Structured Populations Through Local and Global Interference Strategies
We study the situation of an exogenous decision-maker aiming to encourage a population of autonomous, self-regarding agents to follow a desired behaviour at a minimal cost. The primary goal is therefore to reach an efficient trade-off between pushing the agents to achieve the desired configuration while minimising the total investment. To this end, we test several interference paradigms resorting to simulations of agents facing a cooperative dilemma in a spatial arrangement. We systematically analyse and compare interference strategies rewarding local or global behavioural patterns. Our results show that taking into account the neighbourhood's local properties, such as its level of cooperativeness, can lead to a significant improvement regarding cost efficiency while guaranteeing high levels of cooperation. As such, we argue that local interference strategies are more efficient than global ones in fostering cooperation in a population of autonomous agents.</p
Structure Functions of Nuclei at Small x and Diffraction at HERA
Gribov theory is applied to investigate the shadowing effects in the
structure functions of nuclei. In this approach these effects are related to
the process of diffractive dissociation of a virtual photon. A model for this
diffractive process, which describes well the HERA data, is used to calculate
the shadowing in nuclear structure functions. A reasonable description of the
x, Q^2 and A-dependence of nuclear shadowing is achieved.Comment: TeX, 10 pages, 7 figures in 6 ps-file
Hard Diffraction at HERA and the Gluonic Content of the Pomeron
We show that the previously introduced CKMT model, based on conventional
Regge theory, gives a good description of the HERA data on the structure
function F_2^D for large rapidity gap (diffractive) events. These data allow,
not only to determine the valence and sea quark content of the Pomeron, but
also, through their Q^2 dependence, give information on its gluonic content.
Using DGLAP evolution, we find that the gluon distribution in the Pomeron is
very hard and the gluons carry more momentum than the quarks. This indicates
that the Pomeron, unlike ordinary hadrons, is a mostly gluonic object. With our
definition of the Pomeron flux factor the total momentum carried by quarks and
gluons turns out to be 0.3-0.4 - strongly violating the momentum sum rule.Comment: C-Shell archive of a PostScript file containing a 20 page paper with
text and 12 figures in i
Strange Baryon Production in Heavy Ion Collisions
The rapidity distribution of and produced in
nucleus-nucleus collisions at CERN energies is studied in the framework of an
independent string model - with quark-antiquark as well as diquark-antidiquark
pairs in the nucleon sea. It is shown that, besides the
- pair production resulting from the fragmentation of
sea diquarks, final state interactions of co-moving secondaries and are needed in order to
reproduce the data. Predictions for - collisions are presented.Comment: Plain TeX + epsf, 40 pages; 1 Postscript-table and 7 Postscript
figures (uuencoded
SnO2 based glasses : A viable photonic system
The present work focuses on sol-gel derived SnO2-based thin glass-ceramic films doped with Er3+ ions, fabricated by dipcoating technique. Our goal is to find a viable fabrication protocol to obtain them. Thin films with a variety of composition were synthesized and their structural, optical and spectroscopic properties were investigated. The FTIR spectra and X-ray diffraction patterns were used to characterize the structure of the thin films. The transparency of the thin film was tested by UV-Vis transmittance measurements. The energy transfer dynamic was investigated by time-resolved spectroscopy and photoluminescence measurements
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