Detection of periodicity in functional time series

We derive several tests for the presence of a periodic component in a time series of functions. We consider both the traditional setting in which the periodic functional signal is contaminated by functional white noise, and a more general setting of a contaminating process which is weakly dependent. Several forms of the periodic component are considered. Our tests are motivated by the likelihood principle and fall into two broad categories, which we term multivariate and fully functional. Overall, for the functional series that motivate this research, the fully functional tests exhibit a superior balance of size and power. Asymptotic null distributions of all tests are derived and their consistency is established. Their finite sample performance is examined and compared by numerical studies and application to pollution data

Beyond promotion-based store switching: Antecedents and patterns of systematic multiple-store shopping.

In this paper, we demonstrate that single-purpose multiple store shopping is not only driven by opportunistic, promotion-based motivations, but may also be part of a longer term shopping planning process based on stable store characteristics. We find that consumers may systematically visit multiple stores to take advantage of two types of store complementarity. In the case of 'fixed cost complementarity', consumers alternate visits to high and low fixed cost stores to balance transaction and holding costs against acquisition costs. 'Category preference complementarity' occurs when different stores offer the best value for different product categories. Tying these multiple store shopping motivations to characteristics of grocery stores leads to interesting new insights into the nature of spatial retail competition.Category; Characteristics; Choice; Competition; Cost; Costs; Multiple store shopping; Patterns; Planning; Preference; Processes; Product; Spatial competition; Store choice; Value;

Beyond promotion-based store switching: Antecedents and patterns of systematic multiple-store shopping (revised version).

In this paper, we demonstrate both theoretically and empirically that single-purpose multiple store shopping is not only driven by opportunistic, promotion-based motivations, but may also result from a longer term planning process based on stable store characteristics. We find that consumers may systematically visit multiple stores to take advantage of two types of store complementarity. In the case of 'fixed cost complementarity', consumers alternate visits to high and low fixed cost stores to balance transportation and holding costs against acquisition costs. 'Category preference complementarity' occurs when different stores offer the best value for different product categories, and may induce consumers to visit these stores together on combined shopping trips. In both cases, multiple store shopping leads to a shift from share-of-customers to share-of-wallet retail competition.Multiple store shopping; Spatial competition; Store choice; Planning; Processes; Characteristics; Complementarity; Cost; Costs; Category; Preference; Value; Product; Shopping trip; Competition; Choice; Patterns;

Beyond Promotion-Based Store Switching:Antecedents and Consequences of Systematic Multiple-Store Shopping

In this paper, we demonstrate that single-purpose multiple store shopping is not only driven by opportunistic, promotion-based motivations, but may also be part of a longer term shopping planning process based on stable store characteristics.Starting from a utility-maximizing shopping behavior model, we find that consumers systematically visit multiple stores to take advantage of two types of store complementarity.With 'fixed cost complementarity', consumers alternate visits to highly preferred but high fixed cost-stores, with in-between trips to less appealing, low fixed cost- stores.This compromise strategy allows them to balance transaction and holding costs against acquisition costs. 'Category preference complementarity' occurs when different stores offer the 'best value' for different product categories.It is found to be an important driver of multiple store shopping, and a necessary condition for combined (chained) shopping trips.Tying these multiple store shopping motivations to characteristics of different grocery store formats leads to interesting new insights into the nature of retail competition and the strategic role of more quality-oriented retail marketing mix instruments.

Caractérisations chimiques des ustensiles de cuisine artisanale en aluminium fabriqués au Burkina Faso : cas de Ouagadougou

Dans le cadre de la valorisation des matériaux d’origine artisanale du Burkina Faso, deux (02) types d’échantillons d’ustensiles de cuisine (marmites artisanales) en aluminium prélevés dans les différentes zones de la ville de Ouagadougou, ont subi une série d’analyses chimiques. L'artisanat pose le problème de la qualité des produits finis du pays surtout quand on sait qu'ils sont utilisés pour la cuisine de tous les jours. Ainsi, aucun de ces alliages ne devrait être utilisé pour la fabrication d'ustensiles de cuisine, si nous nous référons à la norme française EN 601 en juillet 2004. Ce travail est une contribution à la caractérisation physique et chimique des marmites artisanales au centre du Burkina Faso. L’analyse à la fluorescence X (XRF) indique que la majeure partie des échantillons étudiés, contiennent environ 87,3% d’aluminium. La diffraction aux rayons X (DRX), la spectrométrie de photoélectrons (XPS), la microscopie optique (MO) montrent que les éléments constitutifs essentiels des échantillons d’ustensiles de cuisine sont : Aluminium, Silicium, cuivre, Magnésium et de Zinc. Enfin, une mesure par colorimétrie permet de mettre en évidence la présence de l’aluminium en solution.Mots clés : Alliages d’aluminium, analyses chimiques, DRX, MO, XPS, colorimétrie

Organic coatings from acetylene at atmospheric pressure: UV light versus plasma

ABSTRACT: A versatile pilot-scale reactor has been designed in such a way that it can be readily converted from a dielectric barrier discharge “PECVD” operating mode into a photoinitiated “PICVD” one; in the latter, low-pressure mercury (Hg) lamps replace the high-voltage glow discharge plasma. Both processes operate at ambient temperature and atmospheric pressure, 100 kPa, using acetylene (C2H2) monomer. In both sets of experiments, it was found that efficient gas-to-solid conversion can occur in the form of a nanoparticulate amorphous hydrocarbon polymer-like material. It was found that in the PICVD case, great care was required to exclude even traces of O2 contamination, because it not only reduced the growth rate of solid, but the latter then became highly oxidized ([O] ~50 at.%) and water-soluble

Cylindrospermopsin is effectively degraded in water by pulsed corona-like and dielectric barrier discharges

Cylindrospermopsin (CYN) is an important cyanobacterial toxin posing a major threat to surface waters during cyanobacterial blooms. Hence, methods for cyanotoxin removal are required to confront seasonal or local incidences to sustain the safety of potable water reservoirs. Non-thermal plasmas provide the possibility for an environmentally benign treatment which can be adapted to specific concentrations and environmental conditions without the need of additional chemicals. We therefore investigated the potential of two different non-thermal plasma approaches for CYN degradation, operated either in a water mist, i.e. in air, or submerged in water. A degradation efficacy of 0.03 +/- 0.00 g kWh(-1) L-1 was found for a dielectric barrier discharge (DBD) operated in air, while a submerged pulsed corona-like discharge resulted in an efficacy of 0.24 +/- 0.02 g kWh(-1) L-1. CYN degradation followed a pseudo zeroth order or pseudo first order reaction kinetic, respectively. Treatment efficacy of the corona-like discharge submerged in water increased with pH values of the initial solution changing from 5.0 to 7.5. Notably, a pH-depending residual oxidative effect was observed for the submerged discharge, resulting in ongoing CYN degradation, even without further plasma treatment. In this case hydroxyl radicals were identified as the dominant oxidants of CYN at acidic pH values. In comparison, degradation by the DBD could be related primarily to the generation of ozone

Nanoporous sponges as carbon-based sorbents for atmospheric water generation

Water scarcity threatens more and more people in the world. Moisture adsorption from the atmosphere represents a promising avenue to provide fresh water. Nanoporous sponges (“NPSs” ), new carbon-based sorbents synthesized from the pyrolysis of resorcinol-formaldehyde resin, can achieve comparable performance to metal organic framework-based systems, but at a significantly lower cost. Oxygen and nitrogen functionalities can be added to the NPS surface, through oxidation and addition of phenanthroline to the initial reagent mixture, respectively. The resulting NPS sorbents have high specific surface areas of 347 to 527 m2·g–1 and an average capillary-condensation-compatible pore size of 1.5 nm. When oxidized, the NPS can capture up to 0.28 g of water per gram of adsorbent at a relative pressure of 0.90 (0.14 g·g–1 at P/Psat = 0.40) and maintain this adsorption capacity over multiple adsorption/desorption cycles. Scaled-up synthesis of the NPS was performed and tested in an experimental water capture setup, showing good agreement between small- and larger-scale adsorption properties. Water adsorption isotherms fitted with the theoretical model proposed by Do and Do demonstrate that hydroxyl functionalities are of key importance to NPS behavior