Search results for "spread"
showing 10 items of 292 documents
Enhanced islanding detection in smart interface protection systems of distributed generation
2021
The widespread presence of distributed generators (DGs) and storage systems (DSSs) in electricity grids has increased the risk of islanding occurrence. This phenomenon must be suitably managed by Distribution System Operators (DSO), in order to avoid adverse situations, in terms of grid-protection problems, equipment damage, safety hazards, power quality problems and so on. Currently anti-islanding protection functions are handled by interface protection systems (IPSs), which are built in accordance with relevant standards for DGs and DSSs connection to power systems. However, some problems may occur in case of operation within the so-called non detection zone (NDZ). This paper presents an …
Contingent convertible bonds for sovereign debt risk management
2015
We consider convertible bonds that contractually stipulate payment standstill, contingent on a market indicator of a sovereign's creditworthiness breaching a distress threshold. This financial innovation limits ex-ante the likelihood of debt crises and imposes ex-post risk sharing between creditors and the debtor. Drawing from literature on contingent contracts, neglected risks, and bank CoCo, we extend prevailing arguments in favor of sovereign CoCo (S-CoCo). We discuss issues relating to their design: which market trigger, market discipline and sovereign incentives, and errors of false alarms or missed crises, and provide supporting evidence with eurozone data and a simple simulation on t…
Problems of the Constitutionalism of the Legal Norms related to the Restrictions of the Spread of Covid-19 infection
2022
Plašās diskusijas Latvijas sabiedrībā par Covid-19 infekcijas slimības ietekmē pieņemtajiem ierobežojumiem, to nozīmi un izpratni, kā arī Satversmes tiesā iesniegto pieteikumu skaits un ierosinātās lietas par iespējamo ar Covid-19 infekcijas slimības izplatības ierobežojumiem saistīto tiesību normu neatbilstību Satversmei norāda uz šī temata nozīmīgumu, kā arī uz to, ka par tiesību normās ietvertajiem ierobežojumiem nolūkā mazināt vīrusa slimības izplatību nav vienprātīgas nostājas. Pētījuma mērķis ir noskaidrot ar Covid-19 infekcijas slimības izplatības ierobežojumiem saistīto tiesību normu satversmības problēmas. Dažādu tiesību institūtu izpratne normatīvajos aktos un tiesību realitātē va…
Portfolio diversification in the sovereign credit swap markets
2018
We develop models for portfolio diversification in the sovereign credit default swaps (CDS) markets and show that, despite literature findings that sovereign CDS spreads are affected by global factors, there is sufficient idiosyncratic risk to be diversified. However, we identify regime switching in the times series of CDS spreads and spread returns, and the optimal diversified strategies can be regime dependent. The developed models trade off the CVaR risk measure against expected return, consistently with the statistical properties of spreads. We consider three investment strategies suited for different CDS market participants: for investors with long positions, speculators that hold unco…
Multispectral integral imaging acquisition and processing using a monochrome camera and a liquid crystal tunable filter
2012
This paper presents an acquisition system and a procedure to capture 3D scenes in different spectral bands. The acquisition system is formed by a monochrome camera, and a Liquid Crystal Tunable Filter (LCTF) that allows to acquire images at different spectral bands in the [480, 680]nm wavelength interval. The Synthetic Aperture Integral Imaging acquisition technique is used to obtain the elemental images for each wavelength. These elemental images are used to computationally obtain the reconstruction planes of the 3D scene at different depth planes. The 3D profile of the acquired scene is also obtained using a minimization of the variance of the contribution of the elemental images at each …
Fractal-structured multifocal intraocular lens
2017
[EN] In this work, we present a new concept of IOL design inspired by the demonstrated properties of reduced chromatic aberration and extended depth of focus of Fractal zone plates. A detailed description of a proof of concept IOL is provided. The result was numerically characterized, and fabricated by lathe turning. The prototype was tested in vitro using dedicated optical system and software. The theoretical Point Spread Function along the optical axis, computed for several wavelengths, showed that for each wavelength, the IOL produces two main foci surrounded by numerous secondary foci that partially overlap each other for different wavelengths. The result is that both, the near focus an…
Super resolved optical system for objects with finite sizes using circular gratings
2015
We present a real time all optical super resolution method for exceeding the diffraction limit of an imaging system which has a circular aperture. The resolution improvement is obtained using two fixed circular gratings which are placed in predetermined positions. The circular gratings generate synthetic circular duplications of the aperture, thus they are the proper choice for a circular aperture optical system. The method is applicable for both spatially coherent and incoherent illuminations, as well as for white light illumination. The resolution improvement is achieved by limiting the object field of view. The proposed method is presented analytically, demonstrated via numerical simulat…
Broadband focused waves with compensated spatial dispersion: transverse versus axial balance.
2007
We determine the constraints an ABCD optical system must verify to achieve, at the focal region, broadband waves with compensated spatial dispersion either along the optical axis, called on-axis isodiffracting fields, or in the lateral direction, here named in-plane isodiffracting beams. An optical configuration is identified for generating both types of achromatic broadband focused wave fields. An experimental verification is also provided.
3D printed diffractive terahertz lenses
2016
[EN] A 3D printer was used to realize custom-made diffractive THz lenses. After testing several materials, phase binary lenses with periodic and aperiodic radial profiles were designed and constructed in polyamide material to work at 0.625 THz. The nonconventional focusing properties of such lenses were assessed by computing and measuring their axial point spread function (PSF). Our results demonstrate that inexpensive 3D printed THz diffractive lenses can be reliably used in focusing and imaging THz systems. Diffractive THz lenses with unprecedented features, such as extended depth of focus or bifocalization, have been demonstrated.
Hydrothermal fluid venting in the offshore sector of Campi Flegrei caldera: A geochemical, geophysical, and volcanological study
2016
The ongoing unrest at the Campi Flegrei caldera (CFc) in southern Italy is prompting exploration of its poorly studied offshore sector. We report on a multidisciplinary investigation of the Secca delle Fumose (SdF), a submarine relief known since antiquity as the largest degassing structure of the offshore sector of CFc. We combined high-resolution morpho-bathymetric and seismo-stratigraphic data with onshore geological information to propose that the present-day SdF morphology and structure developed during the initial stages of the last CFc eruption at Monte Nuovo in AD 1538. We suggest that the SdF relief stands on the eastern uplifted border of a N-S-trending graben-like structure forme…