Channel Regime Research Articles

Influence of the Southern area of the Ust-Luga commercial sea port on the channel regime of the Khabolovka river

The problem investigated in the framework of this work is devoted to the study of changes in the hydrological and channel regimes of the estuary region after the construction of the Southern Port area. The object of the study is the Khabolovka River, which flows into the Luga Bay. Based on the materials of channel surveys, the article gives a modern assessment of the general condition of the channel, presents data on manmade changes in the hydromorphological structure. After the conducted research, it was determined which consequences affecting the hydromorphological appearance of the considered section of the river have now occurred from the influence of various factors. Taking into account the performed and studied in detail analysis of riverbed transformations on the river section, it is possible to formulate the main conclusions and recommendations. As a result, a forecast of the further course and changes of the estuary area of the river is given if the necessary measures to protect against wind-wave influence are not carried out.

MBN explorer atomistic simulations of 855 MeV electron propagation and radiation emission in oriented silicon bent crystal: theory versus experiment

The method of relativistic molecular dynamics is applied for accurate computational modeling and numerical analysis of the channelling phenomena for 855 MeV electrons in bent oriented silicon (111) crystal. Special attention is devoted to the transition from the axial channelling regime to the planar one in the course of the crystal rotation with respect to the incident beam. Distribution in the deflection angle of electrons and spectral distribution of the radiation emitted are analyzed in detail. The results of calculations are compared with the experimental data collected at the MAinzer MIctrotron facility.

Assessment of the position of the project water flow in the lower reaches of hydroelectric facilities, using the example of the novosibirsk hydroelectric power station

Construction of large hydroelectric complexes on the plain rivers of Western Siberia, such as the Ob, as well as other types of anthropogenic impact (infill development, quarrying of nonmetallic building materials, carrying out track works, laying communications, wastewater discharges, etc.) lead to a change in water and channel regimes, hydrological characteristics, channel deformation in the downstream. One of these changes is the landing of water level in the section of the lower pond of the Ob from the Novosibirsk hydroelectric complex to the mouth of the Tom River, which adversely affects navigable conditions of this stretch, operation of water intakes, port and sluice, and also damages the fish industry. The landing of the water level continues to this day, and in order to maintain the design water level, it becomes necessary to increase navigation releases. The design level was changed several times after the commissioning of the Novosibirsk hydroelectric complex due to its low availability, a further change in the availability will lead to a change in the design level mark, or rather its lowering. Therefore, the purpose of the study is to assess the position of the design flow rate at the established design level and make a forecast of changes in water flow depending on the time that has passed since the start of operation of the Novosibirsk hydroelectric complex, taking into account the impact on the channel, carried out dredging works, as well as other types of anthropogenic impacts.

Possibilities of Water Storage in Drainage Channel System of the Upper Rye Island

Consequently, to the construction and operation at water power plant Gabcíkovo came to changes in water regime in adjacent area. The power canal of the Gabcíkovo power plant cut the upper parts of the drainage system in Danube Lowlands. Groundwater level changes have occurred in the vicinity of the Hrušov reservoir what caused changes in discharge and water level regime of the drainage channels. Presented contribution deals with theoretical and practical background of the water management in agriculturally exploited regions, especially with the possibility to create and store enough water for irrigation in the channels of one part of the Rye Island. It was therefore necessary to measure and calculate the capacity of given channels as well as the volume of water stored by means of improved operation on hydraulic structures or by construction of new structures. Rye Island belongs to an area where agriculture in the growing season, especially due to the irregular distribution of precipitation, very often suffers from drought. The probability of ensuring at least 10 mm of precipitation in one decade of the growing season is only 50% and the probability of 30 mm of precipitation is only 20%. It follows that without irrigation the moisture for vegetation cover is not ensured. But there can be years with heavy rainfall and then there is no need to irrigate. Rye Island is the warmest area of the Slovakia where the vegetation period is also the longest. Most of it belongs to the area of corn production type. The irrigation economy is therefore profitable. However, the technology of implementation and the effort to introduce large-scale irrigation as soon as possible led to the conclusion that this issue should be considered from several points of view.

Enhanced transport of ions by tuning surface properties of the nanochannel.

Motivated by recent observations of anomalously large deviations of the conductivity currents in confined systems from the bulk behavior, we revisit the theory of ion transport in parallel-plate channels and also discuss how the wettability of a solid and the mobility of adsorbed surface charges impact the transport of ions. It is shown that depending on the ratio of the electrostatic disjoining pressure to the excess osmotic pressure at the walls two different regimes occur. In the thick channel regime this ratio is small and the channel effectively behaves as thick, even when the diffuse layers strongly overlap. The latter is possible for highly charged channels only. In the thin channel regime the disjoining pressure is comparable to the excess osmotic pressure at the wall, which implies relatively weakly charged walls. We derive simple expressions for the mean conductivity of the channel in these two regimes, highlighting the role of electrostatic and electrohydrodynamic boundary conditions. Our theory provides a simple explanation of the high conductivity observed experimentally in hydrophilic channels, and allows one to obtain rigorous bounds on its attainable value and scaling with salt concentration. Our results also show that further dramatic amplification of conductivity is possible if hydrophobic slip is involved, but only in the thick channel regime provided the walls are sufficiently highly charged and most of the adsorbed charges are immobile. However, for weakly charged surfaces the massive conductivity amplification due to hydrodynamic slip is impossible in both regimes. Interestingly, in this case the moderate slip-driven contribution to conductivity can monotonously decrease with the fraction of immobile adsorbed charges. These results provide a framework for tuning the conductivity of nanochannels by adjusting their surface properties and bulk electrolyte concentrations.

Localization and delocalization in one-dimensional systems with translation-invariant hopping

We present a theory of Anderson localization on a one-dimensional lattice with translation-invariant hopping. We find by analytical calculation, the localization length for arbitrary finite-range hopping in the single propagating channel regime. Then by examining the convergence of the localization length, in the limit of infinite hopping range, we revisit the problem of localization criteria in this model and investigate the conditions under which it can be violated. Our results reveal possibilities of having delocalized states by tuning the long-range hopping.

Количественная оценка плановых переформирований РЕКИ Камчатки

A quantitative assessment of channel planform changes on the 600-km channel of the Kamchatka River was carried out. Possibilities of semi-automatic GIS-interpretation of satellite images were used for retrospective analysis of such an extended section of a large river. It was estimated that 37% of the left bank length and 44% of the right bank length are eroded. The amount of material coming into the channel due to riverbanks erosion significantly exceeds the sediment runoff, which determines channel type and regime of channel changes. Processes of bank erosion vary on the scale of the longitudinal profile and different channel types. Downstream according to decrease of channel slope, a decrease of bank erosion intensity is observed. The most important factor of bank erosion on the river local section is the volume of material coming from the upstream sections. A quantitative analysis and forecast of planform changes of a river section requires a differential assessment for different morphodynamic channel types, taking into account characteristics of channel processes in the upstream river sections. The bank erosion prognostic equations obtained for the meandering channel and the floodplain-channel multiple branches of the Kamchatka River are discussed.

О ТЕРМИНОЛОГИИ И КЛАССИФИКАЦИИ РАЗВЕТВЛЕНИЙ РУСЕЛ РАВНИННЫХ РЕК

Braided river channels are very diverse both morphologically (in terms of the number and water content of channel branches, size and shape of islands, their position, ratios, evolution, etc.), and in the mode of channel changes. Nevertheless, both in Russian and foreign literature, when describing them, there are different points of view on terms and classifications that define them, which make it difficult to analyze types of braided channels and regimes of channel changes, possible reactions of channels to changes in factors due to too much generalization. The classification of Moscow State University is considered to be an exception. It is constantly being improved as new data are obtained based on scientific research. Braided channel reaches are formed at several structural levels – point, midchannel bars, channel (island), floodplain-channel and floodplain (split channels). Each higher level of braided channels includes channel types of the previous levels. The main channel patterns that determine channel regime of braided rivers are island-braided channels, along which there are distinguished morphological homogeneous reaches or single patterns of channels or certain channel branches. In turn, in island-braided channels each of their types has several varieties depending on the number and morphology of islands, channel stability, water content of channel branches and peculiarities of water and sediment runoff dispersion along them. Braided channel types and their varieties are characterized by certain values of the flow quasi-uniformity indicator of I.F. Karasev and special coefficients in hydrological and morphological relationships linking morphological parameters of channels with characteristics of determining factors. The article provides a detailed, most complete classification of braided channels and substantiates the use of terms and concepts that characterize each type or braided channel reaches and their elements.

Features of Nondissipative Channeling of Moving Particles Near a Conductor with Current

The specific features of free (outside a conductor) motion of charged particles in the field of a vector potential produced by a direct current flowing in a cylindrical or a flat conductor are considered. It is shown that when particles with negative charge move along the current direction (as well as when positively charged particles move in the opposite direction), the process of interaction of charges with the vector potential of the current corresponds to the presence of a very deep potential well whose minimum lies outside the conductor. This position of the minimum of the potential well corresponds to the flow of a current whose strength does not exceed several kiloamperes for electrons and positrons and several tens of kiloamperes for protons. When these values are exceeded, the minimum shifts into the bulk of the conductor. When the current decreases or the longitudinal energy of a particle increases, the position of the minimum varies in the range from near the surface of the conductor to values that are many tens of times greater than the thickness (diameter) of the conductor. The depth of the potential well increases with increasing energy of a particle and may reach tens and hundreds of kiloelectronvolts even for nonrelativistic particles. The structure of the potential well near the surface of a flat conductor with current corresponds to a harmonic oscillator whose frequency depends on the current strength, the thickness of the flat conductor, and the particle energy. The presence of such features makes it possible to implement a nondissipative channeling regime outside the conductor and the transportation of particles over a long distance.

Hidrodinamika dan produk sedimen terhadap Bendung Irigasi Keumala, Sungai Krueng Baro, Provinsi Aceh

Bendung Kumala dibangun di Sungai Krueng Baro yang merupakan salah satu sungai strategis di Provinsi Aceh untuk mengairi lahan irigasi dan air minum bagi masyarakat di hilirnya, namun sungai ini memiliki permasalahan yang cukup besar sehubungan dengan jalurnya yang panjang dan melewati berbagai formasi geologis. Kondisi ini menyebabkan konsentrasi sedimen yang tinggi pada sungai. Oleh karena itu, penelitian ini bertujuan untuk menganalisisis hidrodinamika sungai dengan menggunakan aplikasi HEC-RAS 5.0. Hasil penelitian memberikan informasi bahwa kapasitas aliran sedimen transport sepanjang dasar sungai bervariasi secara langsung dengan adanya perbedaan antara tegangan geser pada sedimen dasar dan tegangan geser kritis yang diizinkan untuk partikel yang bergerak. Semua sampel sedimen pada hulu dan hilir Bendung Keumala terjadi angkutan sedimen. Pengurangan aliran akibat adanya pembendungan menyebabkan perubahan pada saluran dan rezim alirannya, dan pengurangan pelepasan air telah menyebabkan terjadinya pengurangan angkutan sedimen melayang dan sedimen dasar ke arah hilir. Total sedimen yang terdapat di sekitar areal bendung pada saat debit normal sebesar 6.325.698,93 ton/tahun. Sedimentasi di sekitar bendung menjadi masalah yang serius karena dapat mempengaruhi fungsi dan kinerja bendung dan saluran irigasi. Selain itu pendangkalan akibat sedimentasi menyebabkan tertutupnya intake PDAM Keumala. Untuk mengatasi masalah ini, perlu dilakukan pengerukan dan pengangkutan sedimen dari dasar bendung secara berkala. Pengerukan dan pengangkutan sedimen akan meningkatkan kinerja Bendung Keumala untuk mengairi Daerah Irigasi Krueng Baro. Kapasitas pengaliran intake bendung dapat tetap terjaga untuk mengairi lahan irigasi sesuai dengan areal rencana.

Radiation reaction near the classical limit in aligned crystals

An accelerated charged particle emits electromagnetic radiation. If the driving force is sufficiently strong, the radiated energy becomes comparable to the kinetic energy of the particle and the back-action of the emitted radiation (radiation reaction) significantly alters the dynamics of the particle. The Landau-Lifshitz (LL) equation has been proposed as the classical equation to describe the dynamics of a charged particle in a strong electromagnetic field when the effects of radiation reaction are taken into account. Hitherto, the experimental problem in validating the LL equation has been to achieve sufficiently strong fields for radiation reaction to be important without quantum effects being prominent. Notwithstanding, here we provide a quantitative experimental test of the LL equation by measuring the emission spectrum for a wide range of settings for 50 GeV positrons crossing aligned silicon single crystals near the $(110)$ planar channeling regime as well as 40 GeV and 80 GeV electrons traversing aligned diamond single crystals near the $\langle100\rangle$ axial channeling regime. The experimental spectra are in remarkable agreement with predictions based on the LL equation of motion with small quantum corrections for recoil and, in case of electrons, spin and reduced radiation emission, as well as with a more elaborate quantum mechanical model. Our experiment clearly shows the inadequacy of the Lorentz force as the sole agent of force on the particles in the classical limit, due to its absence of radiative energy loss in describing the dynamics of high-energy charged particles in strong electromagnetic fields like those in aligned single crystals.

Conductance peak density in disordered graphene topological insulators

We investigate the universal properties of quantum transport in graphene nanowires that engender subtle universal conductance fluctuations. We present results for three of the main microscopic models that describe the sublattice of graphene and generate, as we shall show, all the chiral universal symmetries. The results are robust and demonstrate the widely sought sign of chirality even in the regime of many open channels. The fingerprints pave the way to distinguish systems with sublattice symmetry such as topological insulators from ordinary ones by an order of magnitude. The experimental realization requires a single measurement of the chaotic fluctuations of the associated valleytronics conductant. Through the phase coherence length, our theoretical predictions are confirmed with the data from traditional measurements in the literature concerning quantum magnetotransport.

Josephson current mediated by ballistic topological states in Bi2Te2.3Se0.7 single nanocrystals

Superconducting proximity devices using low-dimensional semiconducting elements enable a ballistic regime in the proximity transport. The use of topological insulators in such devices is considered promising owing to the peculiar transport properties these materials offer, as well the hope of inducing topological superconductivity and Majorana phenomena via proximity effects. Here we demonstrate the fabrication and superconducting properties of proximity Josephson devices integrating nanocrystals single of Bi2Te2.3Se0.7 with a thickness of a few unit cells. Single junctions display typical characteristics of planar Josephson devices; junctions integrating two nanocrystals behave as nanodimensional superconducting quantum interference devices. A peculiar temperature and magnetic field evolution of the Josephson current along with the observed excess current effect point towards the ballistic proximity regime of topological channels. This suggests the proposed devices are promising for testing topological superconducting phenomena in two-dimensions.

Assessing the Status of Changing Channel Regimes of Balason and Mahananda River in the Sub-Himalayan West Bengal, India

Rapid infrastructural development, triggered by the economic policies implemented in 1991, subsequently modified the river channel planform of the Terai region of northern West Bengal, India, through perceptible channel fragmentation, excessive in-channel sediment mining and rampant landuse alterations of the floodplains. In this context, this study has attempted to assess the impacts of anthropogenic interventions on fluvial regime of the lower reaches of Balason and Mahananda River of the sub-Himalayan region over the last 30 years by adopting a combined methodological framework of remote sensing and field survey. Results showed that initially the naturally vegetated areas had converted into crop land and grass land, tea plantation or bare land, and afterwards, the majority of it had been converted into built-ups. Besides, a noticeable amount of channel narrowing was directly proportionate to unrestricted sediment mining and embanking of the river channels, evidenced between 1987 and 2017. Comparison of measured multi-temporal channel width along with cross-profiles showed remarkable channel narrowing (18.8 m/year) as well as significant bed lowering (3.15 m). Studies reveal that the rivers have started showing signs of losing their existing equilibrium condition and if that happens then that will lead to the sinking of the ground water table, decreasing flood occurrence interval, destabilization of existing infrastructures associated with rivers, and destruction of river ecology. In order to restore the state of socio-hydrological as well as eco-hydrological amenities of these rivers, certain recommendations have also been made towards promoting the wise use of riverine resources by the local communities and policy makers.

The Rate of Fast Particles Leaving a Planar Channeled Regime in a Quasiclassical Approach

The rate of particles leaving a planar channeling regime is studied in the framework of nonequilibrium statistical theory. In the quasiclassical case, an analytical expression for the corresponding kinetic coefficient $$R_{N}^{{({\text{dec)}}}}$$ is obtained for high-energy particles interacting with valence electrons. At high temperatures, the expression for particle transition is found to agree reasonably well with the probability of thermal (nonradiating) transition of particles from channeling. The rate coefficient $$R_{N}^{{({\text{dec)}}}}$$ including terms of the lowest order with respect to the particle–electron interaction is inversely proportional to vibrational energy relaxation time τν, while the anharmonicity of particle vibration in a planar channel has an effect on the relaxation process only because of its interference with the electron scattering.

Structural Levels and Morphodynamic Classification of Channel Braiding

Channel braiding (separation of river flow into branches) is shown to take place at several structural levels: point, middle-bar, insular (channel), floodplain–channel, and floodplain. Full classification of channel braiding cases is given. The types of braiding are determined that form morphologically homogeneous segments and govern the channel regime of rivers and those that have been formed by single or secondary forms and forms of the 2nd–3rd order, which hamper channel distribution and complicate its morphology. The results obtained in the study include relationships between the types and the structural levels of braiding; the morphological diversity of each type of braiding; their possible combinations; the occurrence in the mountain, semimountain, and lowland rivers; large, medium, and small rivers; under free and limited conditions of channel deformation development (in wide-floodplain and incised channels), in rivers with other morphodynamic types of channel (meandering or relatively linear).

Assessment of the Dnieper Alluvial Riverbed Stability Affected by Intervention Discharge Downstream of Kaniv Dam

Along the middle reaches of the Dnieper River in central Ukraine, braided riverbeds with many islands have developed in alluvial valleys. In the 1970s, six dams were commissioned, and respective monitoring infrastructure was installed. Riverbanks and valley floors composed of unconsolidated material have much lower bank strengths and are susceptible to fluvial erosion and bank collapse, particularly during the release of high flow volumes from hydropower dams. The regulation of the Dnieper River along a cascade of storage reservoirs caused significant changes in its active river channel and hydrological regime. In order to estimate channel stability downstream of the Kaniv reservoir, we conducted an analysis of the hydraulic conditions in terms of changes in flow velocity and propagation of waves caused by intervention water discharges from the Kaniv Hydroelectric Power Plant (HPP). In this paper, we assess the hydromorphological parameters of the studied river reach as well as the characteristics of the related erosion and deposition zones. Therefore, a monitoring framework for channel processes (MCP) downstream of the Kaniv HPP was installed. The analysis of the intervention discharge parameters was conducted based on measurements from July 2015. Channel stability was expressed by the following factors: Lohtin’s number (L), Makkaveev’s (Kc) factor of stability, and a complex index of stability (Mx) by Grishanin. This study shows that the velocity of artificial wave propagation may reach a speed of up to 74.4 km·h−1. The wave propagates for a distance of approx. 45 km within 65 min at a mean velocity of 37.4 km·h−1. The L, Kc, and Mx indicators used in this work showed that when water discharge increased (e.g., during typical peak-capacity operation), the channel becomes unstable and sediments are subject to erosion processes. The riverbed stability indicators clearly illustrate that an increase in parameter values is not dependent on the distance to the dam. The results are valuable for sustainable sediment management at catchment scale and hence, directly applicable in water management.

A Cusp Catastrophe Model for Alluvial Channel Pattern and Stability

The self-adjustment of an alluvial channel is a complicated process with various factors influencing the stability and transformation of channel patterns. A cusp catastrophe model for the alluvial channel regime is established by selecting suitable parameters to quantify the channel pattern and stability. The channel patterns can be identified by such a model in a direct way with a quantified index, which is a 2D projection of the cusp catastrophe surface, and the discriminant function is obtained from the model to distinguish the river state. Predictions based on this model are consistent with the field observations involving about 150 natural rivers of small or medium sizes. This new approach enables us to classify the channel pattern and determine a river stability state, and it paves the way toward a better understanding of the regime of natural rivers to assist decision-making in river management.

A Compact Short-Channel Analytical Drain Current Model of Asymmetric Dual-Gate TMD FET in Subthreshold Region Including Fringing Field Effects

A compact drain current model is developed for an asymmetric, dual gate, monolayer 2 - D Transition metal dichalcogenide (TMD) field effect transistor (FET) in the subthreshold region. The work includes the effect of source to drain tunneling and gate dielectric fringing effects. The model is systematically derived for an asymmetric, dual gate structure. The model developed is also extended into a dual-gate symmetric structure. The characteristic length expression has only physical and dimensional parameters including the contribution of fringing field effects from both front and back gate dielectric. The model is validated with simulation results obtained using NEGF based nanodevice simulators and experimental data of WSe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> p-channel FET. Also, transfer characteristics, output characteristics, subthreshold swing and output resistance are compared with reported data in literatures. A close agreement is observed with some disparity arising because of the non-inclusion of back gate fringing effects and source to drain tunneling in their models. The proposed model captures the effects of different high-κ gate dielectric materials and its thicknesses. Impact of temperature is also studied on transfer characteristics. The model is also scalable from ultrashort channel regime to long channel regime. Finally, the model can be applicable not only for TMD materials but other 2 - D materials also.

Regular and chaotic motion domains in the channeling electron's phase space and mean level density for its transverse motion energy

The motion of charged particles in a crystal in the axial channeling regime can be both regular and chaotic. The chaos in quantum case manifests itself in the statistical properties of the energy levels set. These properties have been studied previously for the electrons channeling along [110] direction of the silicon crystal, in the case when the classical motion was completely chaotic. The case of channeling along [100] direction is of special interest because the classical motion here can be both regular and chaotic for the same energy depending on the initial conditions. The semiclassical energy level density (as well as its part that corresponds to the regular motion domains in the phase space) is computed for the 10 GeV channeling electrons and positrons. It is demonstrated that the level spacing distribution for both electrons and positrons can be better described by Berry-Robnik distribution than by both Wigner (completely chaotic case) or Poisson (completely regular case) distributions.