959 research outputs found
Multiperiod portfolio optimization with multiple risky assets and general transaction costs
We analyze the optimal portfolio policy for a multiperiod mean-variance investor facing multiple risky assets in the presence of general transaction costs. For proportional transaction costs, we give a closed-form expression for a no-trade region, shaped as a multi-dimensional parallelogram, and show how the optimal portfolio policy can be efficiently computed for many risky assets by solving a single quadratic program. For market impact costs, we show that at each period it is optimal to trade to the boundary of a state-dependent rebalancing region. Finally, we show empirically that the losses associated with ignoring transaction costs and behaving myopically may be large
Development of a Web System-based Geographic Information System Technologies to Mapping Electromagnetic Fields: First Developments
The purpose of this research work is to make decisions about the exposure levels of people to radiation, for which, the Web System based on GIS technology (DECOMAPS) was developed for mapping electromagnetic fields in the city of Riobamba. This system executes analysis, search, creation, automation of processes, and mapping activities of electromagnetic fields. The system was developed on an agile development methodology called SCRUM, which allows to create an optimal and interactive work environment between the product owner and the developers in order to create a quality system. Many technological tools were applied by the developer of this system. Once successfully completed, the system was subjected to tests of functionality and usability of the final product through quality metrics established by ISO 9126-3, where it was determined that the system is 93.64% functional, in addition to a 94.40% in usability. Concluding that the system is functional and can be implemented as a contribution in research to be developed in the future on the effects of electromagnetic fields on the human body.
Keywords: OpenGeo Suite, Java, SCRUM, ISO 9126-3, DECOMAP
Response of mycorrhizal Touriga Nacional variety grapevines to high temperatures measured by calorespirometry and near-infrared spectroscopy
Heat stress negatively affects several physiological and biochemical processes in grapevine
plants. In this work, two new methods, calorespirometry, which has been used to determine
temperature adaptation in plants, and near-infrared (NIR) spectroscopy, which has been used to
determine several grapevine-related traits and to discriminate among varieties, were tested to evaluate
grapevine response to high temperatures. ‘Touriga Nacional’ variety grapevines, inoculated or not
with Rhizoglomus irregulare or Funneliformis mosseae, were used in this study. Calorespirometric
parameters and NIR spectra, as well as other parameters commonly used to assess heat injury in
plants, were measured before and after high temperature exposure. Growth rate and substrate carbon
conversion effciency, calculated from calorespirometric measurements, and stomatal conductance,
were the most sensitive parameters for discriminating among high temperature responses of control
and inoculated grapevines. The results revealed that, although this vine variety can adapt its
physiology to temperatures up to 40 ºC, inoculation with R. irregulare could additionally help to
sustain its growth, especially after heat shocks. Therefore, the combination of calorespirometry
together with gas exchange measurements is a promising strategy for screening grapevine heat
tolerance under controlled conditions and has high potential to be implemented in initial phases of
plant breeding programsinfo:eu-repo/semantics/publishedVersio
A Hybrid model for the origin of photoluminescence from Ge nanocrystals in SiO matrix
In spite of several articles, the origin of visible luminescence from
germanium nanocrystals in SiO matrix is controversial even today. Some
authors attribute the luminescence to quantum confinement of charge carriers in
these nanocrystals. On the other hand, surface or defect states formed during
the growth process, have also been proposed as the source of luminescence in
this system. We have addressed this long standing query by simultaneous
photoluminescence and Raman measurements on germanium nanocrystals embedded in
SiO matrix, grown by two different techniques: (i) low energy
ion-implantation and (ii) atom beam sputtering. Along with our own experimental
observations, we have summarized relevant information available in the
literature and proposed a \emph{Hybrid Model} to explain the visible
photoluminescence from nanocrystalline germanium in SiO matrix.Comment: 23 pages, 8 figure
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