bluuebunny/crossref_metadata_2025 huggingface dataset:
Wideband and polarisation‐independent antireflection coating using metamaterials
Authors: Sepehripour Fahimeh , Karimi Parisa , Khavasi Amin
Published: April 2020

Here, the authors propose a new approach for realising wideband and polarisation‐independent antireflection coating, based on a metamaterial composed of a subwavelength array of metallic pillars with a square cross‐section. The effective impedance of the array can be duly adjusted by the size and distance of the pillars. As such, the authors design the effective impedance of the antireflection coating to be the geometrical mean of the impedance of upper and lower media and choose its height to be quarter of operating wavelength. Doing so, the reflection vanishes at the desired frequency and fractional bandwidth of 56% is achieved with a criterion of 10% reflectance (the refractive index of the substrate is assumed to be 4). Importantly, the proposed structure is symmetric in both directions. Thus, in contrast to prior arts, it is not sensitive to the polarisation of the incident wave at normal incidence. In addition to that, it is designed based on a multilayer Chebyshev matching transformer of transmission line theory, which potentially increases the bandwidth of the antireflection up to 107%, albeit at the expense of pass‐band ripples. This structure can be used from very low frequencies up to the infrared regime by appropriate scaling.
Battery swapping station for electric vehicles: opportunities and challenges
Authors: Ahmad Furkan , Saad Alam Mohammad , Saad Alsaidan Ibrahim , Shariff Samir M.
Published: April 2020

In contemporary days, the research and development enterprises have been focusing to design intelligently the battery swap station (BSS) architecture having the prospects of providing a consistent platform for the successful installation of the large‐scale fleet of hybrid and electric vehicles (i.e. xEVs). The BSS may calibrate its subsystem for the electric vehicle (EV) deployment by accomplishing similar idea as in existing gasoline refuelling stations, in which the discharged batteries are being replaced or swapped by partially or fully charged ones by spending a few minutes. The BSS approach has arisen as a promising technology to the traditional EV recharging station approach as it provides a broader experience of business prospects for the specific stakeholders. This work deals with the introduction to BSS including infrastructure, techniques, benefits over charging station and key challenges associated with BSS. Furthermore, an S34X‐smart swapping station for xEVs is proposed and finally, the key thrust is research for BSS is discussed. To the authors’ knowledge, this is the first kind of review work on BSS.
Distributed demand response market model for facilitating wind power integration
Authors: Saebi Javad , Thanh Nguyen Duy
Published: April 2020

To cope with wind power uncertainty, balancing authorities are required to procure adequate ancillary services (ASs) with the aim of maintaining the security of the power system operation. The transmission system operator (TSO) is responsible for maintaining the balance between supply and demand in delivery hours. Besides the generating units, demand response (DR) has the potential capabilities to be considered as a source of AS. The demand‐side AS can be used both locally (by the local entities in distribution networks) and system‐wide (by the TSO). However, the optimal coordination between the local and global beneficiaries is a challenging task. This study proposes a distributed DR market model, in which the DR is traded as a public good among the providers and beneficiaries through the local DR markets. The local DR markets can be run in each load bus to trade the DR provided by retail customers connected to that bus with the buyers. To include the interactions between the energy/reserve market and the local DR markets, a bi‐level programming model is proposed. The bi‐level problem is translated into a single‐level mixed‐integer linear programming problem using the duality theorem. The proposed model is verified by simple and realistic case studies.
Smoothed particle magnetohydrodynamics with the geometric density average force expression
Authors: Wissing Robert , Shen Sijing
Published: April 2020

We present a novel method of magnetohydrodynamics (MHD) within the smoothed particle hydrodynamics scheme (SPMHD) using the geometric density average force expression. Geometric density average within smoothed particle hydrodynamics (GDSPH) has recently been shown to reduce the leading order errors and greatly improve the accuracy near density discontinuities, eliminating surface tension effects. Here, we extend the study to investigate how SPMHD benefits from this method. We implement ideal MHD in the GASOLINE2 and CHANGA codes with both GDSPH and traditional smoothed particle hydrodynamics (TSPH) schemes. A constrained hyperbolic divergence cleaning scheme was employed to control the divergence error and a switch for artificial resistivity with minimized dissipation was also used. We tested the codes with a large suite of MHD tests and showed that in all problems, the results are comparable or improved over previous SPMHD implementations. While both GDSPH and TSPH perform well with relatively smooth or highly supersonic flows, GDSPH shows significant improvements in the presence of strong discontinuities and large dynamic scales. In particular, when applied to the astrophysical problem of the collapse of a magnetized cloud, GDSPH realistically captures the development of a magnetic tower and jet launching in the weak-field regime, while exhibiting fast convergence with resolution, whereas TSPH failed to do so. Our new method shows qualitatively similar results to those of the meshless finite mass/volume schemes within the GIZMO code, while remaining computationally less expensive.
Mergers trigger active galactic nuclei out to z ∼ 0.6
Authors: Gao F. , Wang L. , Pearson W. J. , Gordon Y. A. , Holwerda B. W. , Hopkins A. M. , Brown M. J. I. , Bland-Hawthorn J. , Owers M. S.
Published: April 2020

Aims. The fueling and feedback of active galactic nuclei (AGNs) are important for understanding the co-evolution between black holes and host galaxies. Mergers are thought to have the capability to bring gas inward and ignite nuclear activity, especially for more powerful AGNs. However, there is still significant ongoing debate on whether mergers can trigger AGNs and, if they do, whether mergers are a significant triggering mechanism.

Methods. We selected a low-redshift (0.005 <  z <  0.1) sample from the Sloan Digital Sky Survey and a high-redshift (0 <  z <  0.6) sample from the Galaxy And Mass Assembly survey. We took advantage of the convolutional neural network technique to identify mergers. We used mid-infrared (MIR) color cut and optical emission line diagnostics to classify AGNs. We also included low excitation radio galaxies (LERGs) to investigate the connection between mergers and low accretion rate AGNs.

Results. We find that AGNs are more likely to be found in mergers than non-mergers, with an AGN excess up to 1.81 ± 0.16, suggesting that mergers can trigger AGNs. We also find that the fraction of mergers in AGNs is higher than that in non-AGN controls, for both MIR and optically selected AGNs, as well as LERGs, with values between 16.40 ± 0.5% and 39.23 ± 2.10%, implying a non-negligible to potentially significant role of mergers in triggering AGNs. This merger fraction in AGNs increases as stellar mass increases, which supports the idea that mergers are more important for triggering AGNs in more massive galaxies. In terms of merger fraction as a function of AGN power we find a positive trend for MIR selected AGNs and a complex trend for optically selected AGNs, which we interpret under an evolutionary scenario proposed by previous studies. In addition, obscured MIR selected AGNs are more likely to be hosted in mergers than unobscured MIR selected AGNs.
How galaxies populate haloes in very low-density environments
Authors: Alfaro Ignacio G. , Rodriguez Facundo , Ruiz Andrés N. , Lambas Diego Garcia
Published: April 2020

Context. Evidence shows that properties of dark matter haloes may vary with large-scale environment. Studying the halo occupation distribution in cosmic voids makes it possible to obtain useful information that can shed light on the subject. The history of the formation of the haloes and galaxies residing in these regions is likely to differ from the global behaviour given their extreme environment.

Aims. Our goal is to characterise the halo occupation distribution in the interior of cosmic voids and compare with the general results to unveil the way galaxies populate haloes in simulated galaxy catalogues.

Methods. We used two publicly accessible simulated galaxy catalogues constructed with different methods: a semi-analytical model and a hydrodynamic simulation. In both cases, we identified cosmic voids, and we measured the halo occupation distribution inside these regions for different absolute magnitude thresholds. We compared these determinations with the overall results, and we studied the dependence of different characteristics of the voids. We also analysed the stellar content and the formation time of the haloes inside voids and confronted the general halo population results.

Results. Inside the voids, we find a significantly different halo occupation distribution with respect to the general results. This is present in all absolute magnitude ranges explored. We obtain no signs of variation related to void characteristics, indicating that the effects depend only on the density of the large-scale environment. Additionally, we find that the stellar-mass content also differs within voids that host haloes with less massive central galaxies (∼10%), as well as satellites with significantly lower stellar-mass content (∼30%). Finally, we find a slight difference between the formation times of the younger haloes in voids than the average population. These characteristics indicate that haloes populating voids have had a different formation history, inducing significant changes on the halo occupation distribution.
Exomoon indicators in high-precision transit light curves
Authors: Rodenbeck Kai , Heller René , Gizon Laurent
Published: April 2020

Context. While the Solar System contains about 20 times more moons than planets, no moon has been confirmed around any of the thousands of extrasolar planets discovered so far. Considering the large computational load required for the statistical vetting of exomoon candidates in a star–planet–moon framework, tools for an uncomplicated identification of the most promising exomoon candidates could be beneficial to streamline follow-up studies.

Aims. Here we study three exomoon indicators that emerge if well-established planet-only models are fitted to a planet–moon transit light curve: transit timing variations (TTVs), transit duration variations (TDVs), and apparent planetary transit radius variations (TRVs). We re-evaluate under realistic conditions the previously proposed exomoon signatures in the TTV and TDV series.

Methods. We simulated light curves of a transiting exoplanet with a single moon, taking into account stellar limb darkening, orbital inclinations, planet–moon occultations, and noise from both stellar granulation and instrumental effects. These model light curves were then fitted with a planet-only transit model whilst pretending there were no moon, and we explored the resulting TTV, TDV, and TRV series for evidence of the moon.

Results. The previously described ellipse in the TTV-TDV diagram of an exoplanet with a moon emerges only for high-density moons. However, low-density moons distort the sinusoidal shapes of the TTV and the TDV series due to their photometric contribution to the combined planet–moon transit. Sufficiently large moons can nevertheless produce periodic apparent TRVs of their host planets that could be observable. We find that Kepler and PLATO have similar performances in detecting the exomoon-induced TRV effect around simulated bright (mV = 8) stars. Although these stars are rare in the Kepler sample, they will be abundant in the PLATO sample. Moreover, PLATO’s higher cadence yields a stronger TTV signal. We detect substantial TRVs of the Saturn-sized planet Kepler-856 b although an exomoon could only ensure Hill stability in a very narrow orbital range.

Conclusions. The periodogram of the sequence of transit radius measurements can indicate the presence of a moon. The TTV and TDV series of exoplanets with moons could be more complex than previously assumed. We propose that TRVs could be a more promising means to identify exomoons in large exoplanet surveys.
Effect of the 3D distribution on water observations made with the SWI
Authors: Wirström E. S. , Bjerkeli P. , Rezac L. , Brinch C. , Hartogh P.
Published: April 2020

Context. Characterising and understanding the atmospheres of Jovian icy moons is one of the key exploration goals of the Submillimetre Wave Instrument (SWI), which is to be flown on ESA’s Jupiter Icy Moons Explorer (JUICE) mission.

Aims. The aim of this paper is to investigate how and under which conditions a 3D asymmetric distribution of the atmosphere may affect the SWI observations. In this work we target the role of phase angle for both nadir and limb geometries for unresolved and partially resolved disc observations from large distances.

Methods. We adapted the LIME software package, a 3D non-local thermodynamical equilibrium radiative transfer model, to evaluate ortho-H2O populations and synthesise the simulated SWI beam spectra for different study cases of Ganymede’s atmosphere. The temperature and density vertical distributions were adopted from a previous work. The study cases presented here were selected according to the distance and operational scenarios of moon monitoring anticipated for SWI during the Jupiter phase of the JUICE mission.

Results. We demonstrate that nadir and limb observations at different phase angles will modify the line amplitude and width. Unresolved observations where both absorption against surface continuum and limb emission contributes within the beam will lead to characteristic line wing emission, which may also appear in pure nadir geometry for specific phase angles. We also find that for Ganymede, the 3D non-local thermodynamical equilibrium populations are more highly excited in the upper atmosphere near the sub-solar region than they are in 1D spherically symmetric models. Finally, the 3D radiative transfer is better suited to properly simulate spectral lines for cases where density or population gradients exist along the line of sight.
Mode conversion of two-fluid shocks in a partially-ionised, isothermal, stratified atmosphere
Authors: Snow B. , Hillier A.
Published: April 2020

Context. The plasma of the lower solar atmosphere consists of mostly neutral particles, whereas the upper solar atmosphere is mostly made up of ionised particles and electrons. A shock that propagates upwards in the solar atmosphere therefore undergoes a transition where the dominant fluid is either neutral or ionised. An upwards propagating shock also passes a point where the sound and Alfvén speed are equal. At this point the energy of the acoustic shock can separated into fast and slow components. The way the energy is distributed between the two modes depends on the angle of magnetic field.

Aims. We aim to investigate the separation of neutral and ionised species in a gravitationally stratified atmosphere. The role of two-fluid effects on the structure of the shocks post-mode-conversion and the frictional heating is quantified for different levels of collisional coupling.

Methods. Two-fluid numerical simulations were performed using the (PIP) code of a wave steepening into a shock in an isothermal, partially-ionised atmosphere. The collisional coefficient was varied to investigate the regimes where the plasma and neutral species are weakly, strongly, and finitely coupled.

Results. The propagation speeds of the compressional waves hosted by neutral and ionised species vary and, therefore, velocity drift between the two species is produced as the plasma attempts to propagate faster than the neutrals. This is most extreme for a fast-mode shock. We find that the collisional coefficient drastically impacts the features present in the system, specifically the mode conversion height, type of shocks present, and the finite shock widths created by the two-fluid effects. In the finitely-coupled regime, fast-mode shock widths can exceed the pressure scale height, which may lead to a new potential observable of two-fluid effects in the lower solar atmosphere.
Polynomial relations for cylindrical wheel stiffness characterization for use in a rolling noise prediction model
Authors: Edwards Matthew , Chevillotte Fabien , Bécot François-Xavier , Jaouen Luc , Totaro Nicolas
Published: April 2020

In vehicle tire/road contact modeling, dynamic models are typically used which incorporate the vehicle’s suspension in their estimation: thus relying on a known stiffness to determine the movement of the wheel in response to roughness excitation. For the case of a wheeled device rolling on a floor (such as a delivery trolley moving merchandise around inside a commercial building), there is often no suspension, yet the wheel is still too soft to able to be considered mechanically rigid (as is the case in train/rail contact). A model which is aimed at incorporating the dynamic effects of the trolley in predicting the sound generated by rolling needs to provide a robust way of estimating the wheel’s effective stiffness. This work presents an original technique for estimating the stiffness of a solid cylindrical wheel. A parametric study was conducted in order to identify the dependence of the wheel stiffness on each of the relevant variables: including the wheel’s radius, axle size, width, applied load, and material properties. The methodology may be used to estimate the stiffness of new wheel types (i.e. different geometries and materials) without needing to solve a finite element model each time. Such a methodology has application beyond the field of acoustics, as the characterization of shapes with non-constant cross sections may be useful in the wider field of materials science.
Modelling maximum discharge of the catastrophic flood at the Iya River (Irkutsk region, Russia) in 2019
Authors: Fedorova Alexandra , Makarieva Olga , Nesterova Nataliia , Shikhov Andrey , Vinogradova Tatyana
Published: April 2020

The aim of the study is to estimate the maximum discharge of the catastrophic flood in June 2019 at the Iya River (Irkutsk Region, Russia). The main cause of this flood was extreme precipitation (170 mm for 3 days). The distributed deterministic hydrological model Hydrograph was applied. The schematization of the Iya river basin, parametrization and verification of the Hydrograph model were performed. The median value of the Nash-Sutcliff criteria was 0.69 for the period 1970-1996 for three catchments of the Iya River basin. Based on the data of weather stations and global weather forecast model ICON, maximum daily discharge values of the flood were estimated as 6570 and 4780 m3s-1respectively with the possible value range assessed by the dependence of Q(H) 6250-7500 m3s-1. The flood hydrograph estimated from weather station data coincides in magnitude of flood peak, but its formation is delayed by 1 day. ICON data underestimates maximum value but provides proper timing of the flood peak. The ensemble of input meteorological data from various sources could potentially be used to satisfactorily predict the magnitude and duration of the catastrophic flood and minimize the consequences of the flood.
Runoff generation at the small permafrost river basin in Eastern Siberia: data analysis and hydrological modeling
Authors: Kalugin Andrey , Lebedeva Liudmila
Published: April 2020

The study aims at the analysis of the long-term hydrometeorological data and hydrological modelling at the small permafrost Shestakovka river basin. The basin has postponed reaction to precipitation on different time scales from days to years. Annual, seasonal and monthly streamflow has higher correlation with precipitation sum for corresponding and antecedent time intervals than for the corresponding period only. It suggests importance of water storage and slow water release in the runoff generation that could be related to the suprapermafrost talik aquifers found in the river basin. A spatially distributed physically-based ECOMAG model was applied to the Shestakovka River basin. Evaluation of the simulated river runoff, soil moisture and snow water equivalent was carried out over a period 1990-2014. Obtained NSE 0.59 and BIAS 3% could be considered as satisfactory modelling results taking into account high inter annual and seasonal observed streamflow variability under much less variable meteorological conditions. Better understanding and modelling of the complex interactions between permafrost and hydrological processes is important for development of reliable flood forecasts and long-term future projections under changing climate and growing economical interests to cold regions.
Reconstruction of the hazardous flood of 2014 in Magadan city based on coupled hydrometeorological modelling
Authors: Kurovskaia Viktoriia , Makarieva Olga , Nesterova Nataliia , Shikhov Andrey , Vinogradova Tatyana
Published: April 2020

The study assessed the possibility of using a deterministic distributed hydrological model Hydrograph to calculate the maximum discharge of catastrophic flood at the Magadanka River (48.5 km2, city of Magadan, North-East of Russia) in 2014. The model parameters were not calibrated but borrowed from previously performed regional modelling studies. To verify the Hydrograph model streamflow simulations with daily time step were carried out for the period 1971-2015. The median value of Nash-Sutcliffe efficiency was 0.42 for a period of 44 years, which, given the lack of a meteorological station within the catchment, made it possible to evaluate the results as satisfactory. For the catastrophic flood calculation, two types of precipitation data were used: hourly data on precipitation from the nearest weather station and distribution of precipitation for the watershed from the meteorological model WRF. The flood hydrographs were estimated for the initial and corrected sets of the model parameters. The initial set of the model parameters allowed for proper timing of the flood peak but underestimated “observed” maximum value. We introduced the decreasing correction coefficient to the infiltration parameter of the model to “stretch out” the peak and volume of hydrographs. The results have shown that combining the meteorological input from weather station and regional meteorological model may allow for successful flood simulations in ensemble mode.
Hydrodynamic modelling of the Onega River tidal estuary
Authors: Panchenko Evgenia , Leummens Max , Lebedeva Serafima
Published: April 2020

Hydrodynamic conditions in a tidal estuary are very complex and depend on a wide range of factors. This was also demonstrated in the previous studies for the estuary of the Onega River, which were primarily based on the analysis of field measurements. In this paper, the results of numerical modelling performed using 1D and 2DH/3D «shallow water» approaches are presented, for summer and winter hydrological conditions in the Onega River estuary. The models were built and calibrated using extensive field data, which allowed assessing the opportunities to model the temporal and spatial variability of water levels, discharges, and velocities in a dynamic environment of a tidal estuary.
Modeling water level using downstream river water level observations and machine learning methods
Authors: Sarafanov Mikhail , Kazakov Eduard , Borisova Yulia
Published: April 2020

The article presents the results of the development of a model for calculating levels at one gauging station using the levels at another. To link the levels at two gauging stations, the data on levels, temperature and precipitation were used. The use of machine learning methods to solve the problem of predicting water levels made it possible to achieve an accuracy of about 6 cm. At the same time, traditional statistical models (linear regression, polynomial regression) have 14-16 cm error.
Comparison of snow water equivalent estimates calculated by SnoWE and ICON models on the example of the Kama river basin
Authors: Shikhov Andrey , Churiulin Evgenii
Published: April 2020

More recently, snow accumulation and snowmelt models for their calculations are forced to apply data from numerical weather prediction (NWP) models. This approach allows improvement the accuracy of calculating snow water equivalent (SWE) values especially in remote and mountain regions. In this study, we compared the numerical results of SWE calculations performed by two independent models. The first one is the SnoWE model and the second one is the ICON NWP model. During the period from November 2018 to May 2019, the simulation results of SWE compared with in-situ data from 64 snow surveys, which are located in the Kama river basin. We found that both models (SnoWE and ICON) allow getting satisfactory estimates of the maximum values of SWE (the accuracy of data is sufficient for their practical using). The root mean square error was equal 14-18% from the average measured SWE. Moreover, we got reliable maximum values of SWE for forested areas. At the same time, both models underestimate SWE values during spring snowmelt season. Probably, this underestimation is due to the shortcomings of the models and a sparse snow course-measuring network.
Geoecological research of water bodies of the Central Federal District of different recreational availability
Authors: Chekmareva Ekaterina
Published: April 2020

The results of geoecological research on water bodies of the Central Federal District of Russia are presented. Recreational availability of water bodies determines the level of access to water bodies and the coastal zone and their use for recreational activities by several geoecological characteristics and indicators. The studies included water sampling for chemical, microbiological analysis, and water quality assessment of water bodies and watercourses in the Central Federal District. Databases of morphometric and hydrological characteristics of water bodies have been compiled, access to the coastal zone and water area of reservoirs has been assessed. The recreational potential of water bodies is calculated based on the load on the generally accessible coastal zone, it is specified by natural and cartographic data. It was found that most water bodies have a ban on recreational water use. This is due to poor water quality in chemical and microbiological terms. Most water bodies are insufficiently surveyed and do not have equipped areas for recreational use. Recreation areas are located locally, the water bodies banks are heavily loaded in the summer. This leads to the degradation of the vegetation cover, contamination and re-compaction of the soil, the emergence of unauthorized dumps, increased pressure on the water body areas, the risk of spreading infectious and skin diseases. Access to the coastal zone of water bodies and watercourses in the Moscow Region and adjacent regions is also a problem. This is due to the high level of construction of building near large reservoirs, rivers, and lakes.
Distribution of heavy metals in small streams of the south-west of the Altai territory (Russia) under the influence of anthropogenic impact
Authors: Korovina Oksana , Somin Vladimir , Komarova Larisa
Published: April 2020

Based on the environmental monitoring materials of Joint-stock company “Sibir-Polimetally”, as well as Altai State Technical University scientific research, an analysis was made of the ecological state of the surface waters of small streams in the south-west of the Altai territory: the Nikitikha, Krutishka and Korbolikha rivers. The main pollutants in these water bodies are identified. The research results are relevant for the Altai territory, where small watercourses in the area where industrial enterprises are located can be a source of pollution of large waterways, which are of great economic importance for the Siberian region.
Modern problems of state regulation of operation of a large hydroelectric plants dams area
Authors: Mitina Natalia , Vashchenko Maxim , Shumakova Elena
Published: April 2020

The article is devoted to the problem of increasing the risk of accidents at the dam areas of a large power plant (HPP) and the surrounding area over time, and the need to take these risks into account during their operation. The purpose of the research is to introduce the concept of a dam area as an object of state regulation, to reveal the ways of development and legislative solution of the problem of safe operation of hydroelectric power plants and dam territories at the Federal level, and to develop recommendations for their state regulation. The paper shows the necessity and expediency of zoning the dam territory according to the degree of dynamic impact of the HPP on it in order to optimize the administrative and economic consequences of the operation of these objects.
Catalogue and Atlas of giant aufeis of the North-East of Russia
Authors: Alexeev Vladimir , Makarieva Olga , Shikhov Andrey , Nesterova Nataliia , Ostashov Andrey , Semakina Anastasiya
Published: April 2020

This study presents the results of development of the Catalogue and Atlas of giant aufeis-taryns in the North-East of Russia. The characteristics of aufeis in the North-East of Russia for the last 70 years have been generalized and systematized into the Catalogue database using data from the Cadastre of aufeis (1958) and Landsat images for the period 2013-2017 for the Yana, Indigirka, Kolyma River basins and Chukotka area. In total the territory more than 1.9 million km2 is covered by the study. The Catalogue contains the information about the location and characteristics of more than 4600 aufeis fields. The release of the Atlas of aufeis-taryns in the North-East of Russia has been announced. It reveals the history of study, origin, distribution, and specific features of aufeis and is supplemented with medium- and large-scale maps of aufeis with their seasonal and long-term dynamics.
Hydrographic and erosional dissection pattern as an indicator of landform type of the Malozemelskaya and Bolshezemelskaya Tundra
Authors: Kharchenko Sergey , Belyaev Yury
Published: April 2020

The paper describes the methodology and presents the results of the calculation of the spectral characteristics of the terrain for the territory of the Bolshezemelskaya and Malozemelskaya Tundra (the north of the European part of Russia). There are nine terrain clusters, differing in the topographic dissection pattern. Their geomorphological interpretation is given. Three clusters characterize mountainous and coarsely hilly terrain with the depth of dissection from 150 m and more. The others are low and elevated terrains with much lower depths of dissection (up to 50 m) and different patterns of interposition of landforms.
Relief formation of the Selenga River delta in different periods of water content during the technogenic stage of development
Authors: Ilicheva Elena , Pavlov Maksim , Shchipanova Eseniya , Gavrilova Anastasia
Published: April 2020

The technogenic stage of relief formation of the river mouth systems of the Lake Baikal coast occurred during the rise of the basic level in the 50-70 years of the last century and continues to the present time. In the considered stage, there were at least 6 anomalies of river flow, which caused the onset of low-water and high-water periods in the Baikal basin. Changes in the basic conditions of formation of the Baikal coast were significantly reflected in the morphology of the largest river mouth system of the Selenga River, representing the protruding delta. The fluvial process is leading in delta-forming and is controlled by the level of the receiving reservoir, hydro-climatic events in the basin and seismotectonic manifestations in the coastal zone. During the mentioned period at the top of the Delta, there was a change of the type of channel process, the restructuring of the channel network, the formation of flood-plain terrace, channel meso – and microforms was noted. Morphometric analysis of cartographic data allowed building a hydrological and geomorphological model development of the relief of the Delta, as well as for the time sections corresponding to the periods of low water and high water.
Landscape-permafrost conditions and factors of summer runoff formation of small coastal lowland rivers
Authors: Tregubov Oleg , Gartsman Boris , Lebedeva Liudmila , Nuteveket Marina , Tarbeeva Anna , Uyagansky Konstantin , Shekman Evgeniy , Shepelev Viktor
Published: April 2020

River feed and flow regime in the Anadyr lowland remain stable with significant interannual fluctuations in the amount of summer precipitation (70-180 mm). The lack of summer precipitation is compensated by the suprapermafrost groundwater of the active layer, which is formed by meltwater from seasonal underground ice. In July 2019, complex permafrost-hydrological studies were conducted in the Ugolnaya-Dionisia river basin (Chukotka, Russia) to determine the patterns of formation and dynamics of underground and surface runoff. Seasonal active layer groundwater storage that formed as a result of the melting of seasonal ice was estimated. The territory was classified according to the unite discharge, potential and established water sources. Patterns and factors of seasonal and daily dynamics of the river regime are revealed.
Stochastic Hydrology: Is Scientific Understanding Growing?
Authors: Bolgov Mikhail
Published: April 2020

Among many problems of stochastic hydrology, several major problems may be singled out. (1) The methodology problem – may fluctuation of hydro-meteorological values be considered within the framework of probabilities and random processes? Was this topic discussed after 1953? (2) One-dimensional probability distributions – is there progress? Are there new models? (3) Random Processes: Is Markovian property sufficient or more complex models with memory are needed? (4) Lack of stability resulting from climate changes: Is there progress in understanding the approaches to probabilistic forecasts?
The structure of the Karay river basin by the longitudinal slopes of the river beds and the average gradients of water catchments slopes
Authors: Bukovskiy Mikhail , Kuzmin Kirill , Chernova Maria , Vishniakova Elena
Published: April 2020

The problems of water lag time during flood forecasting, the rate of pollution spreading over the basin area in the event of industrial accidents, the transport of suspended and dissolved substances by rivers, and planning of erosion control measures are very relevant today. Within the framework of the basin approach, an elementary water catchment can be adopted as an elementary unit for the analysis of a particular territory. At the same time, river bed slopes determine the power of the water flow, and the average slopes of water catchments significantly affect the formation of river flow, the nature of the hydrological regime and determine the erosion potential of the territory. The object of the study is the basin of the Karay river, located in the southeastern part of the OkaDon plain. The Karay river is a right tributary of the Khoper river (the Don river basin). For the Karay river basin the river bed slopes and average gradients of catchment slopes are calculated and analyzed. The calculations were based on the digital elevation model created in GIS MapInfo. It is shown that the average slopes of the territories within the Karay river basin range from 0.4° to 1.4°.
Numerical experiments in calculating snow water equivalent and estimating their impact on the formation of spring floods
Authors: Churiulin Evgenii , Kopeykin Vladimir , Frolova Natalia , Krylenko Inna
Published: April 2020

Seasonal snow cover has a significant impact on forming spring floods. Sparse snow course-measuring network does not meet the requirements of modern tasks related to the technologies of numerical weather prediction (NWP) systems and runoff formation models. Moreover, insufficient volume of hydrometeorological data creates a need to improve spring floods forecasting methods by means of available modern hydrometeorological information related to snow cover. To work out an efficient solution to the issue of initial snow data preparation we need a complex approach including the use of data from satellite, atmospheric models, physical-mathematical models of snow cover and insitu information. This approach will provide modern NWP and hydrological models with reliable initial data on snow cover (snow water equivalent – SWE, snow density – SD). The main purpose of our investigation is related to approbation of satellite data and development of snow cover calculation methods for NWP and hydrological models. Numerous SWE and SD experiments have been performed in order to achieve this aim. A regional snow data assimilation system for COSMORu was implemented during the research. Moreover, a new method of hydrological modelling of spring floods based on ECOMAG model with initial information from COSMO-Ru, SnoWE and in-situ data has been proposed and tested.
Machine learning approach for simulation of heavy metal concentration in river water: the Crimean peninsula case study
Authors: Malygin Evgeniy , Lychagin Mikhail
Published: April 2020

This study proposes an approach for simulation of heavy metal concentration in river waters using machine learning techniques. A regression model was built and it captured the relationship between the concentration of heavy metal and metalloids (HMM) and several characteristics of studied catchment. Machine learning techniques allowed to simulate the annual concentration variability of HMM. This approach allows exploring the impact of different factors on studied processes.
Study of moisture transfer through unsaturated zone and groundwater recharge at the emergency site of the Solikamsk-2 Mine (Verkhnekamskoye salt deposit, Russia)
Authors: Vladimirov Konstantin , Nikulenkov Anton , Shvartc Aleksey
Published: April 2020

The article provides the results of assessing groundwater recharge at the emergency site of the Solikamsk-2 Mine (Solikamsk, Russia). The assessment was performed using two separate approaches, including the study of the results of groundwater level observations and numerical modeling of soil moisture transfer through the unsaturated zone. The analysis of the groundwater level fluctuations in observation wells made it possible to estimate the recharge rate in natural and anthropogenic (after the accident) conditions. To study the soil moisture transfer in the upper part of the unsaturated zone two moisture sensors were installed at a depth of 0.4 and 0.65 m. To interpret sensors data the numerical model was developed using the HYDRUS 1D software. The modeling results allowed estimating the recharge rate at a depth of 0.65 m and the main water balance components (evaporation, transpiration, surface runoff). A comparison of the two methods showed similar results, allowing them to use for estimating and predicting groundwater recharge in the annual cycle.
Sensitivity of germanium content on growth conditions of silicon-germanium nanoparticles prepared in nonthermal capacitively-coupled plasmas
Authors: Uddin Md. Seraj , Vijayan C. , Rath Jatindra Kumar
Published: April 2020

We report on the synthesis of Si1−x
Ge
x
alloy nanocrystals by very-high-frequency plasma-enhanced chemical vapor deposition (VHF PECVD) technique at different silane to germane gas flow ratio (R) in a mixture of (H2+Ar) dilution gas and H2 dilution gas alone. TEM, SAED, EDS studies and HAADF-STEM mapping of the samples were done to investigate the NCs' size, crystallinity and distribution of Si and Ge in the Si1−x
Ge
x
alloy NCs. The average estimated size of the NCs in all the samples are in the order of exciton Bohr radius of Ge (24.3 nm), thereby indicating the probability of good quantum confinement. The alloy nature of NCs was confirmed in Raman study. The content of Ge in SiGe NCs was evaluated from Raman spectra which show a direct correlation with the fraction of hydrogen flow in the dilution gas mixture.
Quantum effects in electrical transport properties of Bismuth chalcogenides Topological Insulators
Authors: Paixão José A. , Henriques Marta S.C. , Micale Carlotta , Lopes Elsa B. , Pereira Vanda M. , Gonçalves António P.
Published: April 2020

Quantum effects such as weak-antilocalisation (WAL) behavior and Shubnikov-de Haas (SdH) oscillations in the electrical transport properties of topological insulators, measured on nanostructured polycrystalline samples and single-crystals of a series of bismuth chalcogenide compounds (Bi2(SexTe1-x)3, 0 ≤ x ≤ 1 and BiSbTe3), are presented and discussed.
Investigating the anisotropic compression and high-pressure phase symmetry of orthorhombic RFeO3 vs RMnO3
Authors: Vilarinho R. , Almeida A. , Agostinho Moreira J.
Published: April 2020

Rare-earth orthoferrites and orthomanganites present strong couplings between their structural distortions and physical properties, namely magnetoelectricity, generating interest in predicting and realizing new phases under external parameters, such as hydrostatic pressure. In this regard, we discuss the differences and the similarities of the high-pressure behaviour of the structural distortions arising from anisotropic volume compression. This allows a better understanding of the role played by the octahedra tilt and Jahn-Teller effect as pressure accommodation mechanisms on the stabilization of different crystallographic phases after the insulator to metal structural transition occurring at the critical pressures (Pc) between 35 and 50 GPa.
Electrical response of La2/3-xLi3xTiO3 ceramics obtained by spark plasma sintering
Authors: Silva-Pereira J. , Guerrero F. , Romaguera-Barcelay Y. , Aguilera L. , Silva R.S. , Anglada- Rivera J. , Pillajo N.C. , Almeida A. , Agostinho Moreira J. , Leyet Y.
Published: April 2020

The ceramic system La2/3-xLi3xTiO3 presents as an interesting candidate to be used as an electrolyte in solid-state Li-ion batteries. In this paper the electrical response of the ceramic, La2/3-xLi3xTiO3 with x = 0.11 is reported. La2/3-xLi3xTiO3 nanoparticles were synthesized by high energy milling and sintered by Spark Plasma Sintering from an amorphous phase. After sintering, the samples were structurally characterized by XRD and Raman techniques. Measurements of complex impedance varying frequency from 1 Hz to 10 MHz and temperature from 25 °C to 270 °C were performed. The study of DC conductivity allowed us to find the contributions to the total conductivity, grain, and grain boundary of the samples. From the activation energy values, it was possible to determine the conductive mechanism corresponding to the mobility of Li+ ions.
CdS versus ZnSnO buffer layers for a CIGS solar cell: a depth-resolved analysis using the muon probe
Authors: Ribeiro Eduardo , Alberto Helena V. , Vilão Rui C. , Gil João M. , Weidinger Alois , Salomé Pedro M.P. , Prokscha Thomas , Suter Andreas , Salman Zaher
Published: April 2020

The influence of a buffer layer in the surface of a Cu(In,Ga)Se2 (CIGS) solar cell material is studied using implanted positive muons as a probe. A depth resolved analysis of the muon data suggests that both CdS and ZnSnO reduce the width of a defect layer present at the CIGS surface to about half its original value. Additionaly, CdS is able to reduce the intensity of the distur¬bance in the defected region, possibly due to a surface reconstrution in CIGS.
The diversity of annelids in subterranean waters: a case study from Poland
Authors: Dumnicka Elzbieta , Galas Joanna , Krodkiewska Mariola , Pociecha Agnieszka
Published: April 2020

Not all invertebrate groups commonly occur in subterranean waters but annelids live in surface and underground habitats. The annelid species' richness in various underground waters (wells and interstitial and cave waters) and surface streams of Poland was compared, and the habitat preferences for the most frequent species were determined. Until now, 111 annelid taxa (mainly oligochaetes) had been identified in underground waters in Poland, with higher numbers (71) in the interstitial habitat than in stream bottoms (62). The number of species identified in the caves and wells was distinctly lower (54 and 29, respectively). The Correspondence Analysis did not separate the samples from various underground water types into distinct groups, and the distribution of well fauna was especially scattered (in the ordination diagram) because abiotic parameters differ strongly in studied wells. Only three stygobiontic species (Cernosvitoviella parviseta,Enchytraeus dominicaeandTrichodrilus moravicus) were related to some caves. The analysis of the available data indicate that to obtain a comprehensive picture of the aquatic fauna in a given country all types of subterranean aquatic habitats should be sampled and taken into account. Moreover, to ascertain the composition of benthic invertebrates in running waters, investigation of the interstitial habitat should also be performed.
Estimation of natural frequencies of the laboratory truss structure with output only subspace and frequency-domain techniques
Authors: Kortiš Ján , Maliar Lukáš , Daniel Ľuboš
Published: April 2020

Non-destructive methods of structural testing are preferred to identify their current state because they do not damage the structure. Modal analysis is one of these methods that can be used for a comprehensive assessment of structural measurements. Its main advantage is that it can be used for variety applications. The paper presents an application of operational modal analysis to determine modal parameters of a laboratory steel truss structure. Its goal is to make contribution to the still unfinished development of modal analysis in the area of comprehensive application. There is important to try to use it and especially try to derive some basic generally applicable rules. It is an important step for experimental modal analysis before it can be widely used and accepted in engineering applications.
Concrete slab on elastic foundation under one axle load
Authors: Kuchárová Daniela , Lajčáková Gabriela
Published: April 2020

The paper is dedicated to the dynamical analysis of an isolated concrete slab on an elastic foundation to moving load effect of one axle load. The computational models of one axle load and a slab are mathematically described by the system of ordinary differential equations. The equations of motion are solved numerically in the environment of program system MATLAB. The plate response and dynamic load are monitored at a certain speed and certain initial conditions, depending on the properties of the elastic subgrade.
Comparison of pavement surface roughness characteristics of different wearing courses evaluated using 3D scanning and pendulum
Authors: Brna Matej , Cingel Michal
Published: April 2020

Road pavement roughness, in terms of skid resistance, can be described from a geometrical point of view as a texture or from a physical point of view as friction between a tire and a road surface. The paper deals with the comparison of asphalt and concrete pavement surface on selected newly built sections of the D1 motorway near the Ovčiarsko tunnel. Texture measurements were performed with a Static Road Scanner (SRS) capable of recording surface irregularities up to the microtexture level (2.49 µm resolution). A pendulum was used to determine the friction. Subsequently, the texture was evaluated using individual amplitude and wavelength characteristics and the friction was evaluated using the PTV parameter. Finally, correlations were searched between the roughness characteristics of asphalt concrete and cement concrete pavements, but also between texture and friction characteristics.