Estimating Annual CO2 Flux for Lutjewad Station Using Three Different Gap-Filling Techniques

Long-term measurements of CO2 flux can be obtained using the eddy covariance technique, but these datasets are affected by gaps which hinder the estimation of robust long-term means and annual ecosystem exchanges. We compare results obtained using three gap-fill techniques: multiple regression (MR), multiple imputation (MI), and artificial neural networks (ANNs), applied to a one-year dataset of hourly CO2 flux measurements collected in Lutjewad, over a flat agriculture area near the Wadden Sea dike in the north of the Netherlands. The dataset was separated in two subsets: a learning and a validation set. The performances of gap-filling techniques were analysed by calculating statistical criteria: coefficient of determination (R2), root mean square error (RMSE), mean absolute error (MAE), maximum absolute error (MaxAE), and mean square bias (MSB). The gap-fill accuracy is seasonally dependent, with better results in cold seasons. The highest accuracy is obtained using ANN technique which is also less sensitive to environmental/seasonal conditions. We argue that filling gaps directly on measured CO2 fluxes is more advantageous than the common method of filling gaps on calculated net ecosystem change, because ANN is an empirical method and smaller scatter is expected when gap filling is applied directly to measurements

Sic transit...: South Eastern Europe-Japan University Cooperation Network Student Forum

"Sic transit..." documents the proceedings of ‘South Eastern Europe-Japan University Cooperation Network Student Forum’ held at the University of Tsukuba in 2010. The proceedings comprise individual research papers as well as reports of the two discussion sessions and overall Forum evaluation. While the individual papers discuss issues from each researcher’s specific field of expertise under the Forum umbrella theme, the discussion sessions address a wide range of issues and problems concerning language and society from an essentially trans-disciplinary perspective. 要旨 "Sic transit..."（かくして...は過ぎ去る）は、2010年に筑波大学において開催された「南東欧・日本学生知的交流会議」の報告書です。本報告書は、個々の論文ならびに２つのディスカッション・セッション報告と学生会議に対する総評を収めています。各論文においては、統一テーマの枠内で、研究者が各自の専門領域から問題を論じているのに対して、２つのディスカッション・セッションにおいては、本質的に領域横断的な視点から、言語と社会に関する広範な論点と課題を取り上げています

Paradigms and paradoxes in the metamorphosis of ecotourism

In 2020 and 2021, the entire evolution of human society is under the sign of a paradox, of the adversity of events, coming in avalanche. The tourist evolutions themselves suffer the imprint of the paradox. These paradoxes urgently require new paradigms, the famous ‘paradigm shifts’, mentality, optics, action. The purpose of this research is to outline the main aspects of the research problem and diagnose the situation, with focus on identifying hypotheses for future descriptive or causal research as well as to explore the reasons, attitudes and values of the paradigm and paradox, which differentiate the two notions approached: testing new concepts of forecasting, a product specific to the destination under analysis and in identifying other viable, sustainable alternatives and their analysis in parallel with modelling and promoting new ideas of tourism products or services, respectively improving the existing ones. This article aims to capitalise on the paradox, already successfully applied in economics by the author of the method and in shaping and delimiting ecotourism (in particular the ecotourism from the destination Țara Hațegului – Retezat), emphasising the role of self-contradiction of the field, through a specific type of economic reasoning, in which the rapid evolution of tourism risks are becoming its own cause of its disappearance, knowing that too much tourism kills tourism. Responsibility and the mesological spirit are the only ways to counteract the paradox phenomenon, even a paradigm in the metamorphosis of ecotourism

Clouds and the Near-Earth Environment: Possible Links

Climate variability is a hot topic not only for scientists and policy-makers, but also for each and every one of us. The anthropogenic activities are considered to be responsible for most climate change, however there are large uncertainties about the magnitude of effects of solar variability and other extraterrestrial influences, such as galactic cosmic rays on terrestrial climate. Clouds play an important role due to feedbacks of the radiation budget: variation of cloud cover/composition affects climate, which, in turn, affects cloud cover via atmospheric dynamics and sea temperature variations. Cloud formation and evolution are still under scientific scrutiny, since their microphysics is still not understood. Besides atmospheric dynamics and other internal climatic parameters, extraterrestrial sources of cloud cover variation are considered. One of these is the solar wind, whose effect on cloud cover might be modulated by the global atmospheric electrical circuit. Clouds height and composition, their seasonal variation and latitudinal distribution should be considered when trying to identify possible mechanisms by which solar energy is transferred to clouds. The influence of the solar wind on cloud formation can be assessed also through the ap index - the geomagnetic storm index, which can be readily connected with interplanetary magnetic field, IMF structure. This paper proposes to assess the possible relationship between both cloud cover and solar wind proxies, as the ap index, function of cloud height and composition and also through seasonal studies. The data covers almost three solar cycles (1984-2009). Mechanisms are looked for by investigating observed trends or correlation at local/seasonal scal

Structure and Dynamics of Ferroelectric Domains in Polycrystalline Pb(Fe_1/2Nb_1/2)O₃

A complex domain structure with variations in the morphology is observed at ambient temperature in monoclinic Pb(Fe1/2Nb1/2)O3. Using electron microscopy and piezoresponse force microscopy, it is possible to reveal micrometre-sized wedge, lamellar-like, and irregularly shaped domains. By increasing the temperature, the domain structure persists up to 80 °C, and then starts to disappear at around 100 °C due to the proximity of the ferroelectric–paraelectric phase transition, in agreement with macroscopic dielectric measurements. In order to understand to what degree domain switching can occur in the ceramic, the mobility of the domain walls was studied at ambient temperature. The in situ poling experiment performed using piezoresponse force microscopy resulted in an almost perfectly poled area, providing evidence that all types of domains can be easily switched. By poling half an area with 20 V and the other half with −20 V, two domains separated by a straight domain wall were created, indicating that Pb(Fe1/2Nb1/2)O3 is a promising material for domain-wall engineering