A Consistent Test for the Martingale Difference Hypothesis

This paper considers testing that an economic time series follows a martingale difference process. The martingale difference hypothesis has been typically tested using information contained in the second moments of a process, that is, using test statistics based on the sample autocovariances or in the periodograms. Tests based on these statistics are inconsistent since they just test necessary conditions of the null hypothesis. In this paper we consider tests that are consistent against all fixed alternatives and against Pitman's local alternatives. Since the asymptotic distributions of the tests statistics depend on the data generating process, the tests are implemented using a modification of the wild bootstrap procedure. The paper justifies theoretically the proposed tests and examines their finite sample behavior by means of Monte Carlo experiments. In addition we include an application to exchange rate data.nonlinear dependence,nonparametric, correlation, bootstrap

Simulation of a solar assisted counterflow tunnel dehydrator

A widely used class of vegetable dehydration systems are the “tunnel-and-truck” dehydrators, where the prepared material lies over horizontal trays stored in trucks which move discontinuously in opposite direction of the air flow. This way the driest product is facing the inlet hot and dry air blowed to the system. When product of one truck is ready, is removed from the tunnel leaving space for advance the remaining truck one place forward. This way, a new truck full of wet product can be inserted at the end of the tunnel. The hermal energy required for the process can be supplied by several sources including gas, biomass, solar energy or a combination of them. Solar energy is for free but reaches the Earth with quite a low flux and a strongly fluctuating rate. This imposes the need of special designs and control strategies. This paper presents a study based on simulation models of the dehydrator and the solar thermal system. The dehydrator simulation model is tuned to match experimental data from a particular prototype based on fossil fuel. A solar system simulation model is then applied to the analysis of different design options.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Mutual Coupling Reduction Techniques in Electronic Steering Antennas in X Band

This work provides the development of an antenna for satellite communications onboard systems based on the recommendations ITU-R S.580-6 [1] and ITU-R S.465-5 [2]. The antenna consists of printed elements grouped in an array, working in a frequency band from 7.25 up to 8.4 GHz (15% of bandwidth). In this working band, transmission and reception are included simultaneously. The antenna reaches a gain about 31 dBi, has a radiation pattern with a beam width smaller than 10oand dual circular polarization. It has the capability to steer in elevation through a Butler matrix to 4

El Mercado Bio-combustible : Escenarios hipotéticos

This paper employs the Ivaldi-Vibes algorithm to model the U.S. gasoline market under the hypothetical scenario in which the ethanol production subsidies were phased out from 1995- 2005. Under this hypothetical situation, the individuals were not only willing to switch their consumption decision, but they were also willing to consider alternative modes of transportation including public transportation, biking or walking. As a result, the outside alternative market share increased about 4% and 6% and the conventional gasoline market shares increased while the ethanol blends experienced decreases across all petroleum districts. This methodology also permitted simulating the impact of this elimination on the gasoline prices. The conventional gasoline prices increased in a range between 0.12 and 1.34 percent. Finally, since different types of oxygenates are blended with the regular gasoline to compliance the EPA regulations, the reduction in the reformulated gasoline market shares implied a trade off in the demand for these oxygenates whose variation rates averaged 55.14% for the ethanol-MTBE ratio.En este trabajo se emplea el algoritmo de Ivaldi-Vibes para modelar el mercado de combustibles de EE.UU. bajo el escenario hipotético en el que los subsidios a la producción de etanol fueron eliminados desde 1995 hasta 2005. En esta situación hipotética, los individuos no sólo estaban dispuestos a cambiar su decisión de consumo, sino también a considerar modos alternativos de transporte, incluyendo el transporte público, en bicicleta o caminar. Como resultado, la cuota de mercado exterior alternativa aumentó un 4% y 6% y las cuotas del mercado de combustibles convencionales aumentó, mientras que el etanol combinado experimentó disminuciones en todos los distritos petroleros. Esta metodología también permite simular el impacto de esta eliminación en los precios de los combustibles. Los precios de los combustibles convencionales aumentaron en un rango entre 0,12 y 1,34 por ciento. Por último, ya que los diferentes tipos de compuestos oxigenados son combinados con la gasolina regular para el cumplimiento de las regulaciones de la EPA, la reducción de las cuotas de mercado de combustibles reformulados implica un trade-off de la demanda de estos productos oxigenados, cuya tasa de variación promedio es de 55,14% para la razón etanol- MTBE

Promotion of a market for hourly energy certificates

GHG emissions play a key role in the escalating extreme weather crisis. Commercial and industrial sectors consume almost two-thirds of global end-use electricity; therefore, they have played and will continue to play an important role in driving clean energy in the near term, particularly renewables. Electricity lies at the heart of these global challenges. It is both a significant source of global carbon emissions and is also key to decarbonizing large sectors of the economy, including buildings, transport, and industry. Access to affordable and clean electricity is also essential for economic growth, quality healthcare and education, and many other development goals. To achieve net-zero emissions across the global economy by 2050, electricity must decarbonize even faster, while becoming the core of a just and accessible energy system. Carbon Neutral is where organizations offset their emissions by purchasing carbon offsets intended to reduce or prevent global emissions. 100% Renewable Energy is where organizations purchase renewable energy to match their annual electricity use. 24/7 RE (Renewable Energy) means that rather than emitting and compensating, organizations don’t emit in the first place. Every kilowatt-hour of electricity consumption is met with renewable energy electricity sources. It means reneweble energy for all. The thesis evaluates two main needs for reaching 24/7 for all: metering production and consumption data access and a granular certificate scheme. In addition, a business case for a granular certificate issuer is presented in order to show the opportunities and challenges that these entities will have with the coming 24/7 renewable energy approach. For metering data access, the thesis shows that although Europe is at the forefront of the process, only 3 countries out of the 18 analysed meet all the criteria required to allow consumers and their partners easy and cost-efficient access to relevant, granular metering data. 8 of these countries present some kind of obstacle, 7 do not have a system in place, although data is available in some way, and 1 has no smart rollout plan in place at all. Guarantees of origin schemes analysed shows that systems are not customer centred, in most of the countries it is not possible to assign the GO certificate to a specific consumption point and the process of getting information about cancelled GOs for corporate consumers is tedious and time-consuming. With the identified barriers, in both, metering data exchange infrastructures and guarantees of origin systems, a proposed system have been developed, which links metering data exchange infrastructures with the certification scheme, by providing metering consumption and production data with hourly granularity to support the 24/7 matching of renewable energy. Finally, in the business case proposed, it can be observed that being a granular certificate issuer, a 1.3 M revenue can be obtained in the first year, only with the Spanish market. Then, after 5 years, by also targeting Netherlands and Denmark, a 3.24 M revenue can be obtained. Several business opportunities appear, in addition to the business of being a granular certificate issue

The growth of second homes and time sharing in small islands

This paper stems from the observation that a growing number of visitors to the island of Tenerife fly without the traditional package, even though they arrive on charter flights. In 1990, 22.5% of foreign visitors flew to the island on a seat only basis. This percentage of tourists represented about half a million people who either have their own house (secondary home or time sharing) or they had contracted the accommodation separately from transportation.: It seems that about 200,000 visitors came with a time sharing arrangement and about 100,000 used a private house, while the rest stay at a hotel or an apartment of the traditional sector (Cabildo Insular de Tenerife, 1992, II: 255 -263).peer-reviewe

Structural and numerical identifiability of thermal resistances in plate fin-and-tube heat exchangers using manufacturer catalog data

Plate fin-and-tube heat exchangers, commonly known as heating/cooling coils, are widely used in HVAC systems to transfer heat to or from air. A problem of practical interest in coil simulation is to identify the thermal resistances on the air and liquid sides using manufacturer catalog data. Manufacturers rarely provide detailed information (geometry and circuitry) of the coils they sell or install in factory-made equipment such as air handling units or fan-coils; they just report the performance of the coil at a few typical operating conditions. This paper examines whether it is mathematically possible to back-calculate the thermal resistances on the air and liquid sides using a set of performance data that is disturbed by noise (e.g. measurement errors) and consists of operating cases in which none of the two thermal resistances can be neglected. The first part of the paper discusses the structural identifiability problem, that is, the mathematical possibility of fitting Nusselt-type correlations for air and liquid, as well as a constant resistance for the wall. The second part of the paper discusses the possibility of calculating the numerical value of the parameters of the Nusselt correlations (constant or constant and exponent) using noisy data. The analysis is applied to a typical coil, which is simulated by means of a mathematical modelUniversidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

With a little help from my peers: professional development of higher education teachers to teach critical thinking

Critical Thinking (CT) has become a fundamental competence of the 21st century. However, university teachers still face several difficulties in promoting it through their teaching practice, mainly due to the lack of pedagogical training aimed at this purpose. In the scope of the CRITHINKEDU Erasmus+ project, a 5-day European training course for university teachers was held in Rome (Italy) aiming to engage participants with CT teaching practices and to prepare them with the required tools suitable for its development. Some teachers from the University of Trás-os-Montes e Alto Douro (UTAD) attended the course as trainees, and later, along with other colleagues, assumed the role of trainers during its replication in Vila Real (Portugal). Through the analysis of a focus group of eight teachers from UTAD, the current exploratory case study aims to understand teachers’ conceptions on CT and characterize how those are integrated in the teaching practices. It also tries to evaluate the impact that both training courses (as trainees and/or trainers) had on their professional development. Preliminary reflections on the implementation of CT teaching practices and the design of teacher's training courses in this field are discussed. Keywords: critical thinking; teaching practice; teacher training; professional development; higher educatio

Probing the EBL evolution at high redshift using GRBs detected with the Fermi-LAT

The extragalactic background light (EBL), from ultraviolet to infrared wavelengths, is predominantly due to emission from stars, accreting black holes and reprocessed light due to Galactic dust. The EBL can be studied through the imprint it leaves, via $\gamma$-$\gamma$ absorption of high-energy photons, in the spectra of distant $\gamma$-ray sources. The EBL has been probed through the search for the attenuation it produces in the spectra of BL Lacertae (BL Lac) objects and individual $\gamma$-ray bursts (GRBs). GRBs have significant advantages over blazars for the study of the EBL especially at high redshifts. Here we analyze a combined sample of twenty-two GRBs, detected by the Fermi Large Area Telescope between 65 MeV and 500 GeV. We report a marginal detection (at the ~2.8 $\sigma$ level) of the EBL attenuation in the stacked spectra of the source sample. This measurement represents a first constraint of the EBL at an effective redshift of ~1.8. We combine our results with prior EBL constraints and conclude that Fermi-LAT is instrumental to constrain the UV component of the EBL. We discuss the implications on existing empirical models of EBL evolution.Comment: on behalf of the Fermi-LAT collaboration, accepted for publication on Ap