bluuebunny/crossref_metadata_2025 huggingface dataset:
О достаточных условиях оптимальности для задач оптимального управления с бесконечным горизонтом времени
Authors: Belyakov Anton Olegovich
Published: May 2020

Рассматривается теорема Сейерстада о достаточных условиях оптимальности в сравнении с теоремами Мангасаряна и Эрроу для задач оптимального управления с бесконечным временны́м горизонтом. Допускаются как конечные, так и бесконечные значения целевого функционала, поскольку используются критерии обгоняющей и слабо обгоняющей оптимальности. Расширены условия, при которых применима теорема Сейерстада, и приведены соответствующие примеры. Показано, что условия оптимальности являются одновременно необходимыми и достаточными, когда гамильтониан линеен относительно переменных состояния и управления. Получена новая форма достаточных условий оптимальности для случая, когда гамильтониан не является ни вогнутым, ни дифференцируемым по переменной управления.
Editorial
Authors: Sousa Neto Miguel Rodrigues de , Martins Jr Carlos , Sotana Edvaldo Correa
Published: May 2020

Editorial, vol. 9, n.º 18, jul.-dez. 2017.
Configurações espaciais baseadas na intervenção estatal em territórios indígenas do Chaco
Authors: Castilla Malena Ines
Published: May 2020

O presente artigo analisará o pa­pel desses organismos da ordem governa­mental da Província do Chaco, na Argenti­na. Vamos nos concentrar principalmente na análise das políticas que implementam e constroem fronteiras que determinam as comunidades étnicas locais de forma pre­judicial. Para isso, vamos nos concentrar em explicar o contexto em que a expan­são da fronteira agrária foi consolidada em regiões do país - como no caso da região do Chaco - durante a década de 1990 e como essas organizações têm um impacto sobre ela. Portanto, o objetivo deste traba­lho será dar conta das transformações so­cioeconômicas, territoriais e até culturais que se seguiram à implementação de tais ações na área.
Locais de cidadania, experiências de cidadanização: pesquisa etnográfica em relação ao direito à moradia na cidade de Buenos Aires
Authors: Girola María Florencia , Garibotti María Belen
Published: May 2020

O objetivo do presente trabalho é analisar diferentes experiências de cidadanização registradas em duas áreas urbano-habitacionais da cidade de Buenos Aires que podem se distinguir, entre outras coisas, por seus contextos históricos de origem e formas de construção, por suas tipologias de construção e modalidades de povoamento: por uma parte, um macro conjunto resultante de um processo de produção estadual de moradia social (Conjunto Urbano Soldati, localizado no bairro de Villa Soldati); e, por outra parte, um assentamento que é produto de um proceso social ou popular de produção de hábitat (Assentamento La Carbonilla, no bairro portenho de La Paternal, em Buenos Aires). Nosso objetivo é avançar em uma análise comparativa de processos de conformação de cidadanias ligados à aquisição do direito à moradia através do estudo das práticas e experiências ‘nativas’, de materialidades e significados concretos envolvendo sujeitos localizados. Para tal fim, realizamos um trabalho de campo etnográfico construído em torno de atividades de observação / participação e entrevistas em profundidade com moradores das duas áreas citadas e a sistematização de fontes documentais secundárias.
Editorial
Authors: Sotana Edvaldo Correa , Sousa Netto Miguel Rodrigues de , Martins Junior Carlos
Published: May 2020

.
Expediente
Authors: Revista de história Albuquerque:
Published: May 2020

.
Expediente
Authors: Albuquerque: revista de história Editores de
Published: May 2020

Sobre esse número.
O clássico e o moderno
Authors: Zanatto Rafael
Published: May 2020

Trata-se de analisar dois ensaios produzidos pelo crítico e historiador Paulo Emílio Sales Gomes sobre os cineastas Serguei Eisenstein e Orson Welles. Publicados na segunda metade de 1950 no Suplemento Literário do jornal O Estado de S. Paulo, os ensaios analisam aspectos da linguagem, do estilo e da expressão social dos filmes de Eisenstein e Welles a partir de um recorte histórico-biogr´áfico delineado a partir dos estudos históricos desenvolvidos pelo cineasta em sua estada em Paris e na pesquisa sobre o cineasta francês Jean Vigo. Veremos como revisitar a fortuna artística de Eisenstein será fundamental para compreender aspectos da linguagem cinematográfica clássica, fundamentada significativamente na montagem paralela e no close-up. No caso de Welles, o foco repousa nas descobertas da profundidade de campo e do plano sequência como recursos narrativos carácterísticos do cinema moderno. Em conjunto, o comentário às obras de Eisenstein e Welles abrem caminho para reflexões histórico-biográficas bastante refinadas, que ainda hoje podem inspirar aqueles que tem o cinema como tema de suas pesquisas históricas, embasadas em uma metodologia apta a pautar questões de linguagem, estilo e expressão social que afluem do fenômeno cinematográfico.
Inter-hemispheric comparison of ionosphere variation at each latitudinal band during quiet geomagnetic condition.
Authors: Adebiyi Shola , Adimula Isaac , Oladipo Olushola
Published: May 2020

This paper compares the quiet time variation of the Total Electron Content (TEC) over four stations located at high and mid latitudes in the northern and southern hemispheres of the African-European longitudes. Five years Global Positioning System (GPS) data, from 2002 to 2006, representing the periods of high to low solar activities were used for the study. Generally, the maximum diurnal values of TEC are observed between 10:00 – 14:00 LT in all the stations during the periods investigated. The minimum values of TEC are observed during the pre-sunrise hours for the two mid latitude stations and around the pre-midnight/post-midnight for the high latitude stations. The maximum values of TEC, however vary with season, latitude and solar activity in all the stations. The values decrease with increase in latitudes and decrease in solar activity. The values range between 10 – 32 and 11 – 50 TECU respectively, for high and mid latitudes for all the years considered. Seasonally, the highest values of TEC are generally observed during the equinoxes in all the stations except at the southern mid latitude station where it can as well be observed in summer, particularly during the Moderate Solar Activity (MSA) and Low Solar Activity (LSA) periods. The lowest values of TEC are observed in winter in all the stations in the southern hemisphere and can be observed in both winter and summer for stations in the northern hemisphere depending on the latitude and solar activity period. TEC variation also exhibits (1) asymmetry in the equinoctial values in all the stations and the magnitude is most pronounced during the period of High Solar Activity (HSA); (2) winter ionosphere anomaly feature, observed only in the northern hemisphere stations; and (3) daytime minimum and nighttime maximum in the diurnal structures of TEC at high latitude in the northern hemisphere during the winter. The nighttime maximum value was observed around 21:00 LT with magnitude that decreases with decrease in solar activity. The annual maximum value of TEC decreases with solar activity at all the stations, with the highest/lowest peak observed in HSA/LSA periods.
Energy distribution of an ion cloud in a quadrupole Penning Trap
Authors: B. M. Dyavappa
Published: May 2020

Ions are confined in Penning trap by the combination of electric field and magnetic field, as the electric field confines ions in the axial direction through an electric potential minimum and the magnetic field applied along the axis of the trap confines the ions in the radial direction. In the high temperature limit Coulomb interaction of ions can be neglected and the total energy is due to the electrostatic potential energy of the charge of ions and kinetic energy due to thermal energy. However, in the low temperature limit the trapping potential created by the dc voltage applied between the end cap and ring electrodes is cancelled by Coulomb interaction of ions and the total energy is mainly kinetic energy of ions. The probability density of energy distribution of ions along axial direction, in radial plane and total probability density of energy distribution due to resulting motion of both axial and radial motion of ions under high temperature and low temperature limits in a Quadrupole Penning trap are presented here. These results reveal the energy properties of ion cloud and are useful to carry out accurate measurement experiments on single stored particle, antiparticles with energy related parameters, under high temperature and low temperature limits in a Quadrupole Penning trap.
Optimal Power Point on the I-V Curve of a Photovoltaic Solar System (Modelling and Analysis)
Authors: Alfa Baba , Yakubu Adamu  , Daniel Alberto Pena Perez
Published: May 2020

Motivated by recent interest in improving the performance of PV cells, we explored the optimal power point in Photovoltaic (PV) cells by using three different topologies to compare its function and efficacy. Firstly, we investigate the consequence of connecting a PV directly to the load. Secondly, the efficacy of an electronic device that generates a pulse width modulation (PWM) to control a boost converter connected to the PV panel and the load and finally the maximum power point tracking (MPPT) method by using the Algorithm Perturb and Observe (P\&O), with the implementation of the DC-DC converter between the PV panel and the load. In doing so, a mathematical model of the PV cell was employed and using MATLAB Simulink, the behaviour of the voltage and current signals acquired were analysed, this helps in understanding the performance of the solar cell under different meteorological circumstances, and its effect on the power generated by the PV cell. Finally, based on the performance simulations on the three methods implemented, the results were tested for the response time of the MPPT under different load conditions in order to ascertain it performance.
Peer Instruction: uma experiência no ensino de cálculo com base em metodologias ativas de aprendizagem
Authors: Rachelli Janice , Bisognin Vanilde
Published: May 2020

No presente estudo, tem-se como objetivo analisar as contribuições da utilização da metodologia ativa Peer Instruction no ensino e na aprendizagem de tópicos trabalhados na disciplina de Cálculo A, na qual se aborda, especificamente, o conteúdo de integração de taxas de variação e integrais definidas. Na pesquisa, desenvolvida com 41 estudantes do curso de Engenharia de Produção da Universidade Federal de Santa Maria, utilizou-se a estratégia de ensino inspirada na metodologia Peer Instruction, em que os alunos, após leitura prévia do assunto fora da sala de aula, responderam, em sala de aula, a 10 questões conceituais disponibilizadas no Moodle, discutindo suas respostas com os colegas. A partir dos dados obtidos por meio das discussões realizadas nos grupos, das respostas dos alunos às questões e à pesquisa de opinião, constatou-se o envolvimento e a satisfação dos alunos na realização das atividades e a eficiência do uso da metodologia na aprendizagem dos conceitos tratados.
O ensino de matemática com jovens e adultos em uma escola do campo na Amazônia
Authors: Formigosa Marcos Marques , Silva Benedita das Graçaçs Sardinha da , Oliveira Mara Rita Duarte de
Published: May 2020

A Educação de Jovens e Adultos é uma modalidade de ensino da educação básica, que atende pessoas com histórias de marginalização e as consequências dos intensos processos de exclusão de meios essenciais de vida, como a educação. Este ensaio tem por objetivo apresentar os desafios e possibilidades encontrados no ensino de Matemática com jovens e adultos, em uma escola do campo no interior da Amazônia. Fundamenta-se nos pressupostos da pesquisa qualitativa, com registros narrativos no decorrer das aulas ou nas conversas informais, gravadas em áudio e/ou vídeo. As análises foram feitas a partir dos relatórios diários construídos pelos professores, bem como das manifestações feitas de forma escrita e oral pelos alunos. A experiência revelou que as atividades de matemática desenvolvidas pelos professores, mediante as histórias de vida dos alunos, se distingue daquelas práticas comumente encontradas nas aulas de tal disciplina, e contribuiu para a superação dos desafios normalmente encontrados nas escolas do campo, tanto no ensino, que permitiu aos docentes a busca de novas possibilidades de trabalho, quanto na aprendizagem, que promoveu aos alunos um novo olhar para a disciplina de Matemática.
Semiótica e aprendizagem inclusiva: um estudo que envolve a cegueira
Authors: Anjos Daiana Zanelato dos , Moretti Méricles Thadeu
Published: May 2020

A pretensão deste estudo foi tratar da educação matemática inclusiva no que se refere à aspectos da aprendizagem de objetos de saber geométricos para o estudante cego. A educação inclusiva, no geral, deixou de ser uma questão distanciada da realidade das classes de ensino regular. Atualmente vários países, entre eles o Brasil, já adotam políticas fortes de inclusão e, com isso, é comum que em classes de ensino regular, os professores depararem-se com alunos com algum tipo de necessidade de inclusão. Utilizou-se, como aporte teórico, os estudos semio-cognitivos de Raymond Duval relacionados à aprendizagem intelectual em uma abordagem qualitativa do tipo Estudo de Caso para buscar a compreensão sobre a aprendizagem de uma estudante cega congênita na apreensão de objetos de saber em geometria. Abordou-se aqui uma parte dessas preocupações de acesso ao objeto que é o acesso às imagens e às figuras geométricas. Asseverou-se que elementos semio-cognitivos precisam ser considerados pelos professores que ensinam matemática, uma vez que os meios comuns de produção desses objetos são de acesso confuso e nada fácil ao estudante cego congênito.
Transposição didática em Chevallard: conceitos e teorização primordiais para a teoria antropológica do didático
Authors: Kluth Verilda Speridião , Almouloud Saddo Ag
Published: May 2020

Este artigo tem o intuito de explicitar a transposição didática e conceitos dela emergidos como propulsores da Teoria Antropológica do Didático (TAD) desenvolvida por Chevallard complementando de forma retroativa o estudo por nós publicado que trata especificamente do desenvolvimento primordial da TAD. Os textos analisados na pesquisa aqui apresentada são de 1981 a 1992, portanto as primeiras escritas do autor sobre uma proposta que iria ser consolidada posteriormente. A metodologia de compreensão e interpretação dos textos estudados foi inspirada na hermenêutica filosófica fenomenológica gadameriana que busca compreender do que o texto fala na perspectiva da estrutura constituída pela pergunta e sua resposta. Deste estudo, concluímos que Chevallard encontra na análise epistemologia da Matemática e na antropologia didática do conhecimento o fio condutor que articula e legitima os arranjos didáticos que tecem a transposição do saber matemático a ser ensinado em saber matemático ensinado que fundamenta o surgimento da Didática da Matemática e da TAD.
Seasonal variations in quantitative and qualitative sperm characteristics in fertile and subfertile stallions
Authors: Suliman Yara , Becker Frank , Tuchscherer Armin , Wimmers Klaus
Published: May 2020

Abstract. Horses are seasonal breeders with a natural breeding season beginning in
spring and extending through midsummer. In this study, quantitative and
qualitative parameters of chilled stallion semen were compared between
fertile and subfertile stallions and between the breeding and the
non-breeding season. Semen quality parameters compared included ejaculate
volume, sperm concentration, total sperm number, sperm morphology, and
computer-assisted semen analysis (CASA)-derived sperm movement
characteristics obtained from two groups of warmblood stallions (n=8; four fertile stallions and four subfertile stallions), which differ in the seasonal
pregnancy rate 80 %–90 % (fertile) vs. 40 %–60 % (subfertile). A total of
64 ejaculates were collected from the stallions (n=8; four in the
breeding season and four in the non-breeding season of each stallion). No
significant differences in the semen quality parameters between the fertile
and the subfertile stallions in the non-breeding season were observed.
However, in the breeding season the proportion of morphologically normal
sperm, total motility, progressive motility, average path velocity (VAP),
and curvilinear velocity (VCL) were significantly higher in the fertile
group (P<0.05) when compared with the subfertile group. In
addition, a significant seasonal variation in the proportion of
morphological normal sperm was found in the fertile group between the
breeding and the non-breeding season (P<0.05). Moreover,
significant seasonal variations (P<0.05) in CASA parameters of mean
VAP, straight line velocity (VSL), and beat-cross frequency (BCF) were
observed in the fertile and the subfertile stallions, which tended to be
lower in the non-breeding season. In conclusion, differences between the
fertile and the subfertile stallions were observed only in the breeding
season, and a few of CASA-derived parameters seemed to be significantly lower
during the non-breeding season in both the fertile and the subfertile
stallions.
Mixing characteristics of refractory black carbon aerosols at an urban site in Beijing
Authors: Liu Hang , Pan Xiaole , Liu Dantong , Liu Xiaoyong , Chen Xueshun , Tian Yu , Sun Yele , Fu Pingqing , Wang Zifa
Published: May 2020

Abstract. Black carbon aerosols play an important role in climate
change because they directly absorb solar radiation. In this study, the
mixing state of refractory black carbon (rBC) at an urban site in Beijing in
the early summer of 2018 was studied with a single-particle soot photometer
(SP2) as well as a tandem observation system with a centrifugal particle
mass analyzer (CPMA) and a differential mobility analyzer (DMA). The results
demonstrated that the mass-equivalent size distribution of rBC exhibited an
approximately lognormal distribution with a mass median diameter (MMD) of
171 nm. When the site experienced prevailing southerly winds, the MMD of rBC
increased notably, by 19 %. During the observational period, the ratio of
the diameter of rBC-containing particles (Dp) to the rBC core
(Dc) was 1.20 on average for Dc=180 nm, indicating that the
majority of rBC particles were thinly coated. The Dp∕Dc value
exhibited a clear diurnal pattern, with a maximum at 14:00 LST and a
Dp growth rate of 2.3 nm h−1; higher Ox conditions increased the
coating growth rate. The microphysical properties of rBC were also studied. Bare rBC particles
were mostly found in fractal structures with a mass fractal dimensions
(Dfm) of 2.35, with limited variation during both clean and polluted
periods. The morphology of rBC changed with coating thickness increasing.
When the mass ratio of nonrefractory matter to rBC (MR) was <1.5,
rBC-containing particles were primarily found in external fractal structures,
and they changed to a core–shell structure when MR>6, at
which point the measured scattering cross section of rBC-containing
particles was consistent with that based on the Mie-scattering simulation.
We found that only 28 % of the rBC-containing particles were in core–shell
structures with a particle mass of 10 fg in the clean period but that proportion
increased considerably, to 45 %, in the polluted period. Due to the morphology
change, the absorption enhancement (Eabs) was 12 % lower than that
predicted for core–shell structures.
Model simulations of atmospheric methane (1997–2016) and their evaluation using NOAA and AGAGE surface and IAGOS-CARIBIC aircraft observations
Authors: Zimmermann Peter H. , Brenninkmeijer Carl A. M. , Pozzer Andrea , Jöckel Patrick , Winterstein Franziska , Zahn Andreas , Houweling Sander , Lelieveld Jos
Published: May 2020

Abstract. Methane (CH4) is an important greenhouse gas, and its atmospheric
budget is determined by interacting sources and sinks in a dynamic global
environment. Methane observations indicate that after almost a decade of
stagnation, from 2006, a sudden and continuing global mixing ratio increase
took place. We applied a general circulation model to simulate the global
atmospheric budget, variability, and trends of methane for the period
1997–2016. Using interannually constant CH4 a priori emissions from
11 biogenic and fossil source categories, the model results are compared
with observations from 17 Advanced Global Atmospheric Gases Experiment (AGAGE)
and National Oceanic and Atmospheric Administration (NOAA) surface stations and
intercontinental Civil Aircraft for
the Regular observation of the atmosphere Based on an Instrumented
Container (CARIBIC) flights, with > 4800 CH4 samples,
gathered on > 320 flights in the upper troposphere and lowermost
stratosphere. Based on a simple optimization procedure, methane emission categories have
been scaled to reduce discrepancies with the observational data for the
period 1997–2006. With this approach, the all-station mean dry air mole
fraction of 1780 nmol mol−1 could be improved from an a priori root mean
square deviation (RMSD) of 1.31 % to just 0.61 %, associated with a
coefficient of determination (R2) of 0.79. The simulated a priori
interhemispheric difference of 143.12 nmol mol−1 was improved to
131.28 nmol mol−1, which matched the observations quite well (130.82 nmol mol−1). Analogously, aircraft measurements were reproduced well, with a global RMSD
of 1.1 % for the measurements before 2007, with even better results on a
regional level (e.g., over India, with an RMSD of 0.98 % and R2=0.65). With regard to emission optimization, this implied a
30.2 Tg CH4 yr−1 reduction in predominantly fossil-fuel-related
emissions and a 28.7 Tg CH4 yr−1 increase of biogenic sources. With the same methodology, the CH4 growth that started in 2007 and
continued almost linearly through 2013 was investigated, exploring the
contributions by four potential causes, namely biogenic emissions from
tropical wetlands, from agriculture including ruminant animals, and from
rice cultivation, and anthropogenic emissions (fossil fuel sources, e.g.,
shale gas fracking) in North America. The optimization procedure adopted in
this work showed that an increase in emissions from shale gas (7.67 Tg yr−1),
rice cultivation (7.15 Tg yr−1), and tropical wetlands (0.58 Tg yr−1) for the
period 2006–2013 leads to an optimal agreement (i.e., lowest RMSD) between
model results and observations.
Mind the gap – Part 1: Accurately locating warm marine boundary layer clouds and precipitation using spaceborne radars
Authors: Lamer Katia , Kollias Pavlos , Battaglia Alessandro , Preval Simon
Published: May 2020

Abstract. Ground-based radar observations show that, over the eastern North Atlantic,
50 % of warm marine boundary layer (WMBL) hydrometeors occur below 1.2 km
and have reflectivities of < −17 dBZ, thus making their detection from
space susceptible to the extent of surface clutter and radar sensitivity. Surface clutter limits the ability of the CloudSat cloud profiling radar (CPR) to
observe the true cloud base in ∼52 % of the cloudy columns it
detects and true virga base in ∼80 %, meaning the
CloudSat CPR often provides an incomplete view of even the clouds it does
detect. Using forward simulations, we determine that a 250 m resolution
radar would most accurately capture the boundaries of WMBL clouds and
precipitation; that being said, because of sensitivity limitations, such a
radar would suffer from cloud cover biases similar to those of the
CloudSat CPR. Observations and forward simulations indicate that the CloudSat CPR
fails to detect 29 %–43 % of the cloudy columns detected by ground-based
sensors. Out of all configurations tested, the 7 dB more sensitive
EarthCARE CPR performs best (only missing 9.0 % of cloudy columns)
indicating that improving radar sensitivity is more important than
decreasing the vertical extent of surface clutter for measuring cloud cover.
However, because 50 % of WMBL systems are thinner than 400 m, they tend to
be artificially stretched by long sensitive radar pulses, hence the
EarthCARE CPR overestimation of cloud top height and hydrometeor fraction. Thus, it is recommended that the next generation of space-borne radars
targeting WMBL science should operate interlaced pulse modes including both a
highly sensitive long-pulse mode and a less sensitive but clutter-limiting
short-pulse mode.
Assessing the performance of climate change simulation results from BESM-OA2.5 compared with a CMIP5 model ensemble
Authors: Capistrano Vinicius Buscioli , Nobre Paulo , Veiga Sandro F. , Tedeschi Renata , Silva Josiane , Bottino Marcus , da Silva Jr. Manoel Baptista , Menezes Neto Otacílio Leandro , Figueroa Silvio Nilo , Bonatti José Paulo , Kubota Paulo Yoshio , Fernandez Julio Pablo Reyes , Giarolla Emanuel , Vial Jessica , Nobre Carlos A.
Published: May 2020

Abstract. The main features of climate change patterns, as simulated by the coupled ocean–atmosphere version 2.5 of the Brazilian Earth System Model (BESM), are compared with those of 25 other CMIP5 models, focusing on temperature, precipitation, atmospheric circulation, and radiative feedbacks. The climate sensitivity to quadrupling the atmospheric CO2 concentration was investigated via two methods: linear regression (Gregory et al., 2004) and radiative kernels (Soden and Held, 2006; Soden et al., 2008). Radiative kernels from both the National Center for Atmospheric Research (NCAR) and the Geophysical Fluid Dynamics Laboratory (GFDL) were used to decompose the climate feedback responses of the CMIP5 models and BESM into different processes. By applying the linear regression method for equilibrium climate sensitivity (ECS) estimation, we obtained a BESM value close to the ensemble mean value. This study reveals that the BESM simulations yield zonally average feedbacks, as estimated from radiative kernels, that lie within the ensemble standard deviation. Exceptions were found in the high latitudes of the Northern Hemisphere and over the ocean near Antarctica, where BESM showed values for lapse rate, humidity feedback, and albedo that were marginally outside the standard deviation of the values from the CMIP5 multi-model ensemble. For those areas, BESM also featured a strong positive cloud feedback that appeared as an outlier compared with all analyzed models. However, BESM showed physically consistent changes in the temperature, precipitation, and atmospheric circulation patterns relative to the CMIP5 ensemble mean.
The Kinetic Energy Budget of the Atmosphere (KEBA) model 1.0: A simple yet physical approach for estimating regional wind energy resource potentials that includes the kinetic energy removal effect by wind turbines
Authors: Kleidon Axel , Miller Lee M.
Published: May 2020

Abstract. With the current expansion of wind power as a renewable energy source, wind turbines increasingly extract kinetic energy from the atmosphere, thus impacting its energy resource. Here we present a simple, physics-based model (KEBA) to estimate wind energy resource potentials that explicitly account for this removal effect. The model is based on the regional kinetic energy budget of the atmospheric boundary layer that encloses the wind farms of a region. This budget is shaped by horizontal and vertical influx of kinetic energy from upwind regions and the free atmosphere above as well as the energy removal by the turbines, dissipative losses due to surface friction and wakes, and downwind outflux. These terms can be formulated in a simple, yet physical way, yielding analytic expressions for how wind speeds and energy yields are reduced with increasing deployment of wind turbines within a region. We show that KEBA estimates compare very well to the modelling results of a previously published study in which wind farms of different sizes and in different regions were simulated interactively with the WRF atmospheric model. Compared to a reference case without the effect of reduced wind speeds, yields can drop by more than 50 % at scales greater than 100 km, depending on turbine spacing and the wind conditions of the region. KEBA is able to reproduce these reductions in energy yield compared to the simulated climatological means in WRF (n = 36 simulations; r2 = 0.822). The kinetic energy flux diagnostics of KEBA show that this reduction occurs because the total yield of the simulated wind farms approaches a similar magnitude as the influx of kinetic energy. Additionally, KEBA estimates the slowing of the region's wind speeds, the associated reduction in electricity yields, and how both are due to the depletion of the horizontal influx of kinetic energy by the wind farms. This limits typical large-scale wind energy potentials to less than 1 W m−2 of surface area for wind farms with downwind lengths of more than 100 km, although this limit may be higher in windy regions. This reduction with downwind length makes these yields consistent with GCM-based idealized simulations of large-scale wind energy resource potentials. We conclude that KEBA is a transparent and informative modelling approach to advance the scientific understanding of wind energy limits, and can be used to estimate regional wind energy resource potentials that account for the depletion of wind speeds.
Modelling the hydrological interactions between a fissured granite aquifer and a valley mire in the Massif Central, France
Authors: Duranel Arnaud , Thompson Julian R. , Burningham Helene , Durepaire Philippe , Garambois Stéphane , Wyns Robert , Cubizolle Hervé
Published: May 2020

Abstract. The contribution of groundwater to the hydrology of hard rock regions has long been assumed to be small. This is being progressively challenged and conceptual hydrological models of headwater wetlands in these regions may need to be revised. We developed a high-resolution MIKE SHE/MIKE 11 model of a 231.3 ha headwater catchment in the granitic uplands of the French Massif Central to estimate the contribution of groundwater upwelling to the water balance of the Dauges mire, an acidic valley mire of international importance for nature conservation. We estimated that groundwater upwelling from the underlying granite weathering formations – mostly an approximately 55  m deep fissured zone – provides 27.1 % of total long-term inflows to the mire. This contribution increases to 37.2 % in September when total inflows are small. Overland boundary inflow accounts for an average of 40.2 % of total inflows. However most of this originates from groundwater seepage through mineral soils along the mire margins or in small unchannelized valleys upslope of the mire. A sensitivity analysis showed that model performance in terms of the simulation of mire groundwater levels was most sensitive to parameters describing the mineral soils and granite weathered formations rather than the overlying peat layer. Variation partitioning showed that groundwater upwelling was the most important factor driving simulated monthly groundwater table depth within the mire. Sustained groundwater upwelling maintains the mire water table close to or at ground level for most of the year. As a result, precipitation and overland boundary inflows are mostly evacuated as saturation-excess runoff. There was close agreement between the observed distribution of mire habitats and areas where the simulated long-term groundwater seepage rate was larger than zero in September. Groundwater upwelling from the underlying weathered formations can be a quantitatively important and functionally critical element of the water balance of valley mires in granitic headwater catchments. These results have important legal and management implications.
Wetropolis extreme rainfall and flood demonstrator: from mathematical design to outreach
Authors: Bokhove Onno , Hicks Tiffany , Zweers Wout , Kent Thomas
Published: May 2020

Abstract. Government and consulting experts on flood mitigation generally face difficulties when trying to explain the science of extreme flooding to the general public, in particular the concept of a return period.
Too often, for example, people perceive they are safe for the next 100 years after a 1:100-year return-period flood has hit their town. UK flood practitioners therefore gave us the challenge to design an outreach tool that conceptualises the science of flooding in a way that is accessible to and directly engages the public, and in particular demonstrates what a return period is. Furthermore, we were tasked with designing a live 3-D physical model rather than a graphical or animated 2-D game on a screen. We show here how we tackled that challenge by designing, constructing, and showcasing the Wetropolis Flood Demonstrator. Wetropolis is a transportable and conceptual physical model with random rainfall, river flow, a flood plain, an upland reservoir, a porous moor, representing the upper catchment and visualising groundwater flow, and a city which can flood following extreme and random rainfall. A key novelty is the supply of rainfall every Wetropolis day. Several aspects of Wetropolis are considered.
i. We present the modular mathematical and numerical design on which Wetropolis is based. It guided the choice of parameter values of Wetropolis, which was loosely inspired by the Leeds Boxing Day floods of the River Aire in 2015. The design model further serves as the building block and inspiration for adaptations suited to particular local demands. Moreover, the model is purposely lean and therefore quick to compute, serving flexibility in the outreach-tool design, but is less suitable for any detailed scientific validation.ii. The constructed Wetropolis is described here in broad terms, but we include a link to a GitHub site with details to inspire other bespoke designs. The goal, again, is to facilitate new adaptations of Wetropolis for particular catchments different to the Leeds River Aire case.iii. Our experience in showcasing Wetropolis is summarised and discussed, with the purpose of giving an overview as well as inspiring improved and bespoke adaptations. While Wetropolis should be experienced live, with videos found on the GitHub site, here we provide a photographic overview. To date, Wetropolis has been showcased to 500 to 1000 people at public workshops and exhibitions on recent UK floods, as well as to flood practitioners and scientists at various research and stakeholder workshops.iv. We conclude with some ongoing design changes, including how people can experience natural flood management in a revised Wetropolis design. Finally, we also discuss how Wetropolis, although originally focussed solely on outreach, led to a new cost-effectiveness analysis and protocol for assessing flood-mitigation plans and inspired other physical models for use in education and water management.
Systematic comparison of five machine-learning models in classification and interpolation of soil particle size fractions using different transformed data
Authors: Zhang Mo , Shi Wenjiao , Xu Ziwei
Published: May 2020

Abstract. Soil texture and soil particle size fractions (PSFs) play
an increasing role in physical, chemical, and hydrological processes. Many
previous studies have used machine-learning and log-ratio transformation
methods for soil texture classification and soil PSF interpolation to
improve the prediction accuracy. However, few reports have systematically
compared their performance with respect to both classification and interpolation. Here,
five machine-learning models – K-nearest neighbour (KNN), multilayer
perceptron neural network (MLP), random forest (RF), support vector machines
(SVM), and extreme gradient boosting (XGB) – combined with the original data and three log-ratio transformation methods – additive log ratio (ALR), centred log ratio (CLR), and
isometric log ratio (ILR) – were applied to evaluate soil texture and
PSFs using both raw and log-ratio-transformed data from 640 soil samples in the Heihe River basin
(HRB) in China. The results demonstrated that the log-ratio transformations
decreased the skewness of soil PSF data. For soil texture
classification, RF and XGB showed better performance with a higher overall
accuracy and kappa coefficient. They were also recommended to evaluate the
classification capacity of imbalanced data according to the area under the
precision–recall curve (AUPRC). For soil PSF interpolation, RF
delivered the best performance among five machine-learning models with the
lowest root-mean-square error (RMSE; sand had a RMSE of 15.09 %, silt was 13.86 %, and
clay was 6.31 %), mean absolute error (MAE; sand had a MAD of 10.65 %, silt was 9.99 %, and clay was 5.00 %), Aitchison distance (AD; 0.84), and standardized
residual sum of squares (STRESS; 0.61), and the highest Spearman rank
correlation coefficient (RCC; sand was 0.69, silt was 0.67, and clay was 0.69). STRESS
was improved by using log-ratio methods, especially for CLR and ILR. Prediction
maps from both direct and indirect classification were similar in the middle and
upper reaches of the HRB. However, indirect classification maps using log-ratio-transformed data provided more detailed information in the lower reaches of
the HRB. There was a pronounced improvement of 21.3 % in the kappa
coefficient when using indirect methods for soil texture classification compared
with direct methods. RF was recommended as the best strategy among the five
machine-learning models, based on the accuracy evaluation of the soil PSF
interpolation and soil texture classification, and ILR was recommended for
component-wise machine-learning models without multivariate treatment,
considering the constrained nature of compositional data. In addition, XGB
was preferred over other models when the trade-off between the accuracy and runtime was
considered. Our findings provide a reference for future works with respect to the
spatial prediction of soil PSFs and texture using machine-learning models
with skewed distributions of soil PSF data over a large area.
Design and implementation of speed fluctuation reduction for a ball screw feed system at low-speed operation
Authors: Wang Zhaoguo , Feng Xianying , Du Fuxin , Li Hui , Su Zhe
Published: May 2020

Abstract. In the high-precision servo feed system, when the permanent magnet synchronous motor (PMSM) is operated at low speed in the
classical drive feed system (CDFS), the speed fluctuation caused by the
motor torque harmonics seriously affects the speed smoothness of the servo
system. In this paper, a novel double-drive differential feed system (DDFS)
is proposed to effectively suppress the effect of torque harmonics of PMSM
on speed fluctuation of the linear feed system at low-speed operation. Firstly, the effect of motor torque harmonics on motor speed for the DDFS is analyzed by the sensitivity function of the servo system, which indicates that the torque harmonics have little effect on the motor speed at high-speed operation. Then, in the DDFS, we make two motors rotate in the same direction at high speed and differentially synthesize at the ball screw to obtain low-velocity linear motion. Compared with the CDFS, the DDFS can suppress the effect of
motor torque harmonics on speed fluctuation of the table and improve speed
smoothness at low-speed operation.
Classification and susceptibility assessment of debris flow based on a semi-quantitative method combination of the fuzzy C-means algorithm, factor analysis and efficacy coefficient
Authors: Liang Zhu , Wang Changming , Han Songling , Ullah Jan Khan Kaleem , Liu Yiao
Published: May 2020

Abstract. The existence of debris flows not only destroys the facilities but also seriously threatens human lives, especially in scenic areas. Therefore, the classification and susceptibility analysis of debris flow are particularly important. In this paper, 21 debris flow catchments located in Huangsongyu Township, Pinggu District, Beijing, China, were investigated. Besides field investigation, a geographic information system, a global positioning system and remote-sensing technology were applied to determine the characteristics of debris flows. This article introduced a clustering validity index to determine the clustering number, and the fuzzy C-means
algorithm and factor analysis method were combined to classify 21 debris
flow catchments in the study area. The results were divided into four types: debris flow closely related to scale–topography–human activity, topography–human activity–matter source, scale–matter source–geology and topography–scale–matter source–human activity. Nine major factors screened from the classification result
were selected for susceptibility analysis, using both the efficacy coefficient method and the combination weighting. Susceptibility results
showed that the susceptibility levels of 2 debris flow catchments were high, 6 were moderate and 13 were low. The assessment results were consistent with the field investigation. Finally, a comprehensive assessment including
classification and susceptibility evaluation of debris flow was obtained,
which was useful for risk mitigation and land use planning in the study area and provided a reference for the research on related issues in other
areas.
Analysis of the instability conditions and failure mode of a special type of translational landslide using long-term monitoring data: a case study of the Wobaoshi landslide (in Bazhong, China)
Authors: Liu Yimin , Wang Chenghu , Gao Guiyun , Wang Pu , Hou Zhengyang , Jiao Qisong
Published: May 2020

Abstract. A translational landslide comprised of nearly horizontal sandstone and mudstone interbeds occurred in the Ba River basin of the Qinba–Longnan
mountainous area. Previous studies have succeeded to some extent in investigating the formation mechanism and failure mode of this type of
rainfall-induced landslide. However, it is very difficult to demonstrate and validate the previously established geomechanical model, owing to lack of landslide monitoring data. In this study, we considered a translational
landslide exhibiting an unusual morphology, i.e., the Wobaoshi landslide, which occurred in Bazhong, China. First, geological conditions of this landslide were determined through field surveys, and the deformation and
failure mode of the plate-shaped main bodies were analyzed. Second, long-term monitoring was performed to obtain multiparameter monitoring data (width of the crown crack, rainfall, and accumulated water pressure in cracks). Finally, an equation was developed to evaluate the critical water height of the multistage bodies, i.e., hcr, based on the geomechanical model analysis of the multistage main sliding bodies, and the reliability of this equation was verified using long-term relevant monitoring data. Subsequently, the deformation and failure mode of the plate-shaped bodies were analyzed and investigated based on numerical simulations and calculations. Thus, the monitoring data and geomechanical model proved that the accumulated water pressure in cracks makes cracks open much wider and causes the plate-shaped bodies to creep. Simultaneously, an optimized monitoring methodology was proposed for this type of landslide. Therefore, these research findings are of reference significance for the
rainfall-induced translational landslides in this area.
Dynamicity of multi-channel rip currents induced by rhythmic sandbars
Authors: Zhang Yao , Hong Xiao , Xu GuoDong , Liu Xunan , Chen Xinping , Sun Yuxi , Wang Bin , Zhang Chi
Published: May 2020

Abstract. In response to frequent fatal beach drownings, China's first operational attempt on the rip current hazard investigation was made by the National Marine Hazard Mitigation Service (NMHMS). A great number of recreational beaches were found developing rip currents interlaced with rhythmic sandbars, varying by season and location evidenced by satellite images and morphodynamic calculation. Considering insufficient understanding of the multi-channel rip system, case analysis and numerical study were conducted to explore its dynamicity and circulation characteristics under various wave climates in present work. The strength of rip currents was generally proportional to wave height and channel width under certain limits. Increasing wave height was not always a promotion and could even weaken the rip current due to the strong wave-current shear. Interesting pump and feed interactions between adjacent rip currents in the multi-channel system were observed. The rip current might be totally absent in narrow channels when the majority of water flows through neighboring broader pathways. The rip current was highly sensitive to the incident wave angle. Alongshore currents prevailed over the rip current when the wave angle reached 11 degrees to shore normal, which was not favorable to the existence of channeled sandbars. Vortices appeared around the edge of the bar owing to nonuniform wave breaking over rapid-varying bathymetry. The setup water was created shoreward by the sandbar array and substantially increased as the wave deviated from the normal incidence. The water surface depression in the rip channel was not observed as the wave angle increased, which fundamentally explained why the rip current could not persist when the incident wave became slightly oblique. In future, incident wave angle should be further incorporated into empirical formulas or probabilistic models to predict the rip current for expected improvement in accuracy.
Resolving uncertainties in the application of zircon Th / U and CL gauges to interpret U-Pb ages: a case study of eclogites in polymetamorphic terranes of NW Iberia
Authors: Castiñeiras Pedro , Gómez Barreiro Juan , Fernández Francisco J. , Aguilar Carmen , Benítez Pérez José Manuel
Published: May 2020

Abstract. Zircon crystal texture and Th / U ratio have been used as a watertight argument when interpreting U-Pb ages. The wide, and sometimes indiscriminate, use of those gauges could result into misinterpretation of the geological meaning of U-Pb data. A case study is presented here where zircons from a controversial polymetamorphic eclogite unit were analyzed with SHRIMP. Both U-Pb and trace element (TE) data were collected for each point. The combination of TE and structural arguments indicates that zircon was part of the eclogite facies mineral assemblage at 390 Ma. However, using Th / U ratio and CL textures lead to a different interpretation. Our results suggest that in complex orogenic scenarios and extreme environments well-known techniques (CL) and geochemical relationships (Th / U) must be used in combination with TE data and structural relationships as provenance/process gauges. While geochronology provides accurate isotope relationships, their temporal dimension must rely on structural and petrological evidence.
Toward a method for downscaling sea ice pressure
Authors: Lemieux Jean-Francois , Tremblay Bruno , Plante Mathieu
Published: May 2020

Abstract. Sea ice pressure poses great risk for navigation; it can lead to ship besetting and damages. Contemporary large-scale sea ice forecasting systems can predict the evolution of sea ice pressure. There is, however, a mismatch between the spatial resolution of these systems (a few km) and the typical dimensions of ships (a few tens of m) navigating in ice-covered regions. In this paper, we investigate the downscaling of sea ice pressure from the km-scale to scales relevant for ships. Results show that sub-grid scale pressure values can be significantly larger than the large-scale pressure (up to $\\sim$ 4x larger in our numerical experiments). High pressure at the sub-grid scale is associated with the presence of defects (e.g. a lead). Numerical experiments show that a ship creates its own high stress concentration by forming a lead in its wake while navigating. These results also highlight the difficulty of forecasting the small-scale distribution of pressure and especially the largest values. Indeed, this distribution strongly depends on variables that are not well constrained: the rheology parameters and the small-scale structure of sea ice thickness (more importantly the length of the lead behind the ship).