Изменения высоты поверхности и баланс массы ледникового купола Академии Наук на Северной Земле

We have determined the surface-elevation change rates of the Academy of Sciences Ice Cap, Severnaya Zemlya, Russian Arctic, for two different periods: 2004–2016 and 2012/2013–2016. The former was calculated from differencing of ICESat and ArcticDEM digital elevation models, while the latter was obtained by differencing two sets of ArcticDEM digital elevation models. From these surface-elevation change rates we obtained the geodetic mass balance, which was nearly identical for both periods, at −1,72±0,67 Gt a−1, equivalent to −0,31±0,12 m w.e. a−1 over the whole ice cap area. Using an independent estimate of frontal ablation for 2016−2017 of −1,93±0,12 Gt a−1 (−0,31±0,12 m w.e. a−1), we get an estimate of the climatic mass balance not significantly different from zero, at 0,21±0,68 Gt a−1 (0,04±0,13 m w.e. a−1), which agrees with the near-zero average balance at a decadal scale observed during the last four decades. Making an observationally-based assumption on accumulation rate, we estimate the current total ablation from the ice cap, and its partitioning between frontal ablation, dominated by calving (~54%) and climatic mass balance, mostly surface ablation (~46%).На основе разновременных ЦМР установлены скорости изменения высоты поверхности ледникового купола Академии Наук на Северной Земле за два периода: 2004−2016 и 2012/2013−2016 гг. и определён геодезический баланс его массы (−1,72±0,67 Гт/год). Сделан расчёт климатического баланса массы (0,21±0,68 Гт/год) и полной абляции (−3,18 Гт/год) ледника, где на отёл приходится ≈54%, а на поверхностную абляцию – ≈46%

On the use of JMAK theory to describe mechanical amorphization: a comparison between experiments, numerical solutions and simulations

The kinetics of amorphization during ball milling is generally analyzed using two different approaches: the classical Johnson-Mehl-Avrami-Kolmogorov (JMAK) theory and Delogu and Cocco’s model for which a region deterministically transforms after it reaches a certain number of collisions. The application of JMAK analysis to the latter model predicts Avrami exponents to be higher than the experimental ones (typically close to one). We develop simulations based on the probabilistic character of the nucleation phenomenon and concave growth of the amorphous phase in the core of a nanocrystal. The predictions of our simulations are in good agreement with the low Avrami exponents and with the size evolution of the remaining crystallites found experimentally. From these values, the parameters involved in the simulated model (growth rate and probability of nucleation) can be estimated.AEI/FEDER-UE (Project MAT-2016-77265-R)Junta de Andalucía (Grupo PAI

Influence of Milling Time on the Homogeneity and Magnetism of a Fe70Zr30 Partially Amorphous Alloy: Distribution of Curie Temperatures

In this work, the mechanically alloyed Fe70Zr30 (at. %) composition has been used to study the influence of milling time on its homogeneity and magnetic properties. The microstructure and Fe environment results show the formation of an almost fully amorphous alloy after 50 h of milling in a mixture of pure 70 at. % Fe and 30 at. % Zr. The soft magnetic behavior of the samples enhances with the increase of the milling time, which is ascribed to the averaging out of the magnetocrystalline anisotropy as the crystal size decreases and the amorphous fraction increases. The formation of a non-perfectly homogenous system leads to a certain compositional heterogeneity, motivating the existence of a distribution of Curie temperatures. The parameters of the distribution (the average Curie temperature, T C ¯ , and the broadening of the distribution, ∆ T C ) have been obtained using a recently reported procedure, based on the analysis of the approach towards the saturation curves and the magnetocaloric effect. The decrease of ∆ T C and the increase of T C ¯ with the milling time are in agreement with the microstructural results. As the remaining α-Fe phase decreases, the amorphous matrix is enriched in Fe atoms, enhancing its magnetic response.AEI/FEDER-UE Project MAT 2016-77265-

Поверхностные скорости и айсберговый сток ледникового купола Академии Наук на Северной Земле

We have determined the ice-surface velocities of the Academy of Sciences Ice Cap, Severnaya Zemlya, Russian Arctic, during the period November 2016 – November 2017, using intensity offset-tracking of Sentinel-1 synthetic-aperture radar images. We used the average of 54 pairs of weekly velocities (with both images in each pair separated by a12-day period) to estimate the mean annual ice discharge from the ice cap. We got an average ice discharge for 2016–2017 of 1,93±0,12 Gt a−1, which is equivalent to −0,35±0,02 m w.e. a−1 over the whole area of the ice cap. The difference from an estimate of ~1,4 Gt a−1 for 2003–2009 can be attributed to the initiation of ice-stream flow in Basin BC sometime between 2002 and 2016. Since the front position changes between both periods have been negligible, ice discharge is equivalent to calving flux. We compare our results for calving flux with those of previous studies and analyse the possible drivers of the changes observed along the last three decades. Since these changes do not appear to have responded to environmental changes, we conclude that the observed changes are likely driven by the intrinsic characteristics of the ice cap governing tidewater glacier dynamics.По 54 парам космических снимков Sentinel‐1, сделанных с ноября 2016 г. по ноябрь 2017 г., определены скорости движения ледникового купола Академии Наук на Северной Земле. На этой основе оценён среднегодовой расход льда в море этого купола (1,93±0,12 Гт/год), установлены основные пути стока льда, проведено сравнение с прежними оценками

How are consensual, non-consensual, and pressured sexting linked to depression and self-harm? The moderating effects of demographic variables

Sexting among adolescents has triggered controversial debates among scholars and the general public. However, questions regarding the associations between different types of sexting, namely consensual, non-consensual, and pressured sexting, depressive symptoms, and non-suicidal self-harm remain. In addition, little attention has been given to whether demographic variables (i.e., gender, ethnicity, disability, sexual minority) might influence these associations. To fill these gaps in the literature, the present study was conducted. Participants were 2506 adolescents (ages 13–16 years old; Mage = 15.17; SDage = 0.89) from eight high schools located in the suburbs of a large Midwestern city in the United States. Adolescents self-identified as female (50%), Caucasian (57%), approximately 15% reported that they had a disability they received school accommodation for, and 18% self-identified as a sexual minority. They completed self-report questionnaires on their sexting behaviors, depressive symptoms, and non-suicidal self-harm. Findings revealed that non-consensual and pressured sexting were positively related to depressive symptoms and non-suicidal self-harm, whereas consensual sexting was unrelated to these outcomes. Boys engaged in more non-consensual sexting compared with girls, girls were more pressured to send sexts compared with boys, and sexual minority adolescents reported greater consensual sexting compared with non-sexual minority adolescents. Moderating effects revealed that girls, non-minority adolescents, and non-sexual minority adolescents experienced greater depressive symptoms and non-suicidal self-harm when they experienced pressured sexting. These findings underscore the importance of considering various types of sexting and adolescents’ demographic variables when examining the negative outcomes of sexting. Disentangling the relationships among different types of sexting, depressive symptoms, and self-harm aids in the development of evidence-based recommendations for sexting harm prevention and sexual education programs

Análisis numérico del ensayo de fragmentación de fibra única, empleando elementos cohesivos

COMATCOMP 09 : Donostia - San Sebastian, 7, 8 y 9 de octubre de 2009Se ha llevado a cabo un análisis numérico, mediante el Método de los Elementos Finitos (MEF), del ensayo de fragmentación de fibra única empleando elementos cohesivos para modelar la aparición y crecimiento de las grietas de despegue. Dado que durante todo el proceso del ensayo la matriz tiende a contraerse más que la fibra en dirección radial, ha sido preciso tener en cuenta el contacto entre las caras de la grieta de despegue. Como resultado se ha observado que las caras de la grieta se encuentran cerradas a lo largo de toda su longitud. Por tanto, el crecimiento de la misma es en puro modo II de fractura. Los resultados obtenidos para diferentes valores del coeficiente de fricción se han comparado con resultados de análisis numéricos previos, obtenidos con el enfoque de la Mecánica de la Fractura Elástica Lineal (MFEL), empleando el Método de los Elementos de Contorno (MEC). En ausencia de fricción se ha observado un acuerdo excelente en los resultados de ambos enfoques. Sin embargo, si se tiene en cuenta el efecto de la fricción, los resultados obtenidos con elementos cohesivos y con la MFEL muestran comportamientos análogos pero con discrepancias cuantitativas

Control de la Congestión en el IEEE 802.17

Este trabajo de investigación experimental aborda una solución al problema presentado en el núcleo de las redes Metropolitanas (MAN) por el algoritmo de equidad en modo Agresivo del protocolo 802.17, que sufre de una lenta convergencia para alcanzar el estado estable, lo que genera periodos de oscilaciones dentro de un dominio de congestión. Palabras Clave: MAN, RPR, Equidad, Congestión. DOI: http://dx.doi.org/10.5377/nexo.v23i2.237 Nexo: Revista Científica Vol. 23, No. 02, pp.47-52/Nov 201

Control de la Congestión en el IEEE 802.17

This experimental research addresses a solution to the problem presented in the core of metropolitan area network (MAN) by an algorithm of equality in an aggressive state of protocol 802.17, which suffers from a slow convergence in order to reach a stable state, generating periods of oscillation within the congested area.Keywords: MAN; RPR; Equality; Congestion.DOI: 10.5377/nexo.v23i2.237Nexo: Revista Científica Vol. 23, No. 02, pp.47-52/Nov 2010Este trabajo de investigación experimental aborda una solución al problema presentado en el núcleo de las redes Metropolitanas (MAN) por el algoritmo de equidad en modo Agresivo del protocolo 802.17, que sufre de una lenta convergencia para alcanzar el estado estable, lo que genera periodos de oscilaciones dentro de un dominio de congestión.Palabras Clave: MAN, RPR, Equidad, Congestión.DOI: http://dx.doi.org/10.5377/nexo.v23i2.237Nexo: Revista Científica Vol. 23, No. 02, pp.47-52/Nov 201