bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessment and mapping of water erosion by the integration of the Gavrilovic “EPM” model in the Inaouene watershed, Morocco
Authors: Marouane Laaraj , Lahcen Benaabidate , Valérie Mesnage
Published: October 2021

Water erosion is one of the main causes of soil degradation around the world. In M orocco, In M orocco, the watersheds have very significant soil wastes, related to various physical and anthropic factors. The Oued Inaouene watershed is concerned because of its location in the eastern part of the Saïss basin, between the Middle Atlas and the Pre-Rif, where water erosion is more accentuated. This basin covers a total area of 3597.13 Km2 and it is marked by a semi-arid climate with relatively abundant (989.68 mm), irregular rainfall and strong anthropic pressure. This will have an impact of overexploiting natural resources in general and soils in particular. The excessive use of agricultural land has led to their fragility and aggravation of their susceptibility to erosion. These conditions, both natural and anthropic, have induced a rather intense erosive dynamic, which can be visible in its various forms, including gullying and landslides. The erosive dynamics leads progressively and certainly to impoverish the soils of the watershed and the silting of the dam Idris 1st located downstream of the Oued Inaouene, hence the interest of this study. The use of the “EPM” model for the estimation of soil losses approaches the severity of the erosive phenomenon. The average soil loss due to water erosion according to the model used is estimated at 53.34 t/ha/year. The maximum losses are about 597.642 t/ha/yr per plot. Total annual losses for the watershed are approximately 211084195 t/yr. Furthermore, the analysis of these results allowed, with the help of GIS, to determine the factors that control water erosion and which are, in order of importance: rainfall, slope, and soil sensitivity Soil protection. If anti-erosion measures aren’t adopted in the threatened parts of the watershed, this will have serious consequences for the dam and water quality .
Exploring the Relationship between LST, LULC and NDVI in Saïss Plain using Geospatial Techniques
Authors: El Garouani Manal , Amyay Mhamed , Lahrach Abderrahim , Jarar Oulidi Hassane
Published: October 2021

Land use/land cover (LULC) change has been confirmed that have a significant impact on climate through various pathways that modulate land surface temperature (LST) and precipitation. However, there are no studies illustrated this link in the Saïss plain using remote sensing data. Thus, the aim of this study is to monitor the LST relationship between LULC and vegetation index change in the Saïss plain using GIS and Remote Sensing Data. We used 18 Landsat images to study the annual and interannual variation of LST with LULC (1988, 1999, 2009 and 2019). To highlight the effect of biomass on LST distribution, the Normalized Difference Vegetation Index (NDVI) was calculated, which is a very good indicator of biomass. The mapping results showed an increase in the arboriculture and urbanized areas to detriment of arable lands and rangelands. Based on statistical analyzes, the LST varies during the phases of plant growth in all seasons and that it is diversified due to the positional influence of LULC type. The variation of land surface temperature with NDVI shows a negative correlation. This explains the increase in the surface temperature in rangelands and arable land while it decreases in irrigated crops and arboriculture.
Combining AHP with GIS for landfill site selection: Case of the Ben Ahmed circle
Authors: Benezzine Ghizlane , Zouhri Abdeljalil , Koulali Yahya
Published: October 2021

The demographic growth in the circle of Ben Ahmed leads to a large production of household waste. This waste is disposed of in uncontrolled open-air landfills. The informal discharge of this waste leads to negative impacts on the environment and on human health. To remedy these effects, this work aims to locate suitable locations for a sanitary landfill. The Analytical Hierarchy Process (AHP), a multi-criteria approach, and the Geographic Information System (GIS) were used. Following a thorough study, nine criteria were taken into account; distance to groundwater, water bodies, roads, highways, settlements, forests, land use map, elevation, and slope. Suitable sites have been identified to assist managers and officials in selecting a good location for a legal landfill.
Groundwater flow equation, overview, derivation, and solution
Authors: El Mezouary Lhoussaine , El Mansouri Bouabid
Published: October 2021

Darcy’s law is the basic law of flow, and it produces a partial differential equation is similar to the heat transfer equation when coupled with an equation of continuity that explains the conservation of fluid mass during flow through a porous media. This article, titled the groundwater flow equation, covers the derivation of the groundwater flow equations in both the steady and transient states. We look at some of the most common approaches and methods for developing analytical or numerical solutions. The flaws and limits of these solutions in reproducing the behavior of water flow on the aquifer are also discussed in the article.
Applied Latin Hypercube stochastic method to quantify the uncertainty in groundwater equation model simulations
Authors: El Mezouary Lhoussaine , El Mansouri Bouabid
Published: October 2021

It is accepted that digital models simplify the physical reality that is the object of the modeling. Hydrodynamic modeling is an approach with high uncertainties in this context. Indeed, the deterministic modeling approach assumes the existence of a functional relationship between the observed variables. The variables are observed by a series of measurements riddled with errors. Because of this, there is always a significant amount of uncertainty associated with a hydrogeological model. This uncertainty can be associated with the conceptual model or with the data and parameters associated with the different components of the model. Some model parameters such as hydraulic conductivity and recharge are particularly susceptible to uncertainty. Stochastic modeling of the hydrodynamics of a groundwater reservoir is an adequate response to allow us to take a step back on the significance of the results. The study is based on the development of a direct problem-solving model which represents the best estimate of the real hydrodynamic system. This model is used to make predictions. With a stochastic approach, a set of models is constructed where each model, as a whole, is considered to be equally likely. Each model is then used to make the prediction or simulate a given scenario. The MODFLOW-STOCHASTIC-GMS code allows us to do randomization simulations (Latin Hypercube method) and with parameter indicators.
Assessment of groundwater quality using Physico-chemical analyses of Sahel-Doukkala region
Authors: Benmhammed Ayoub , Mejjad Nezha , Laissaoui Abdelmourhit , Elyahyaoui Adil , Chakir El mahjoub , Ziad Nadia , Marah Hamid
Published: October 2021

Water quality preservation represents one of the biggest challenges the world is facing nowadays. In Morocco, water quality decline is among the significant problems facing the country’s water sector. Geographic Information System (GIS) is an effective and useful tool for interpreting, evaluating and displaying spatial data for water resources management. In order to assess the Physico-chemical characteristics of groundwater of the Sahel-Doukkala aquifers, water samples were collected from 50 points well distributed in the study area, analysed according to standard methods, and the results were interpreted using the geographic information system (GIS) technique. There was an important spatial variability in the studied parameters and element concentrations (T°, pH, EC, Cl-, Ca2+, Mg2+, Sr, B and Na+), revealing that the aquifers lithology, sea intrusion and the agriculture methods are the main factors influencing the water nature in the study area.
Study of the growth of three species:Micropterus salmoides(Lacépède, 1802),Cyprinus carpio(Linneaus, 1758) andOreochromis niloticus(Linnaeus, 1758) in Moroccan continental waters
Authors: Ferraj Loubna , Bousseba Meriem , Ouahb Sara , El Moujtahid Aziz , Hasnaoui Mustapha
Published: October 2021

The growth parameters of three species were studied for the first time in the AlMassira Dam. A total of 137 individuals were examined during this study between September 2020 and January 2021. The estimation of growth parameters was carried out by size structure analysis using FISAT II software. The growth parameters ofMicropterus salmoides, CyprinuscarpioandOreochromis niloticusare respectively:L∞= 35.11 cm, K= 0.58 year-1, t0= 0.57 year;L∞= 44.85 cm, K= 2.60 year-1, t0= 1.27 year andL∞= 45.26 cm, K= 0.32 year-1, t0= 0.33 year. Thus, the Von Bertalanffy growth equations are written respectively:L(t) = 35.11 (1-e-0.58 (t+0.57)),L(t)= 44.85 (1-e-2.60 (t+1.27)) andL(t)= 45.26 (1-e-0.32 (t+0.33)).
Comparative study of the coagulation efficacy of Moringa Oleifera seeds extracts to alum for domestic wastewater treatment of Ain Aouda City, Morocco
Authors: Al-Jadabi Naif , Laaouan Mohamed , Mabrouki Jamal , Fattah Ghizlane , El Hajjaji Souad
Published: October 2021

This research aimed to investigate the performance of seeds extract of Moringa Oleifera (MO) as an eco-friendly coagulant and an alternative practice in enhancing primary domestic wastewater effluent treatment by coagulation/flocculation, and sedimentation. The seeds of Moringa Oleifera were dried, crushed, and sieved, the content of oil was extracted with n-hexane as a solvent employing soxhlet apparatus (electro thermal) then used the residue as domestic wastewater coagulant. Jar tests were conducted for improve the primary treatment of domestic wastewater effluent from the wastewater plant of Ain Aouda city, Rabat, Morocco. For this reason, perform of coagulation tests was comparative with using aluminium sulphate (alum). Moringa Oleifera seeds extract at the optimal dose of 250 mg/L shows encouraging results, by comparison with the use of alum (150 mg/L). In reality, in terms of TSS reduction 95.5% and 96.8%, while turbidity reduction 97.5% and 98.1% were obtained for MO seeds extract and alum, respectively. But, the reduction rate of COD and BOD of Alum was somewhat higher than that of MO seeds extract 81.8% and 76.8% for COD, while were 75.5% and 72% for BOD respectively. Differently from alum, observed that increase in the extract of MO seeds dosage happened a slight change in pH value, decrease conductivity, and three times less bulky quantity of sludge than alum. For avoiding the numerous disadvantages associated with the use of chemical coagulants, the usage of Moringa Oleifera seeds extracts is recommended.
Multidimensional Model of Product Quality Formation
Authors: Tchigirinsky Julius , Gribanova Nadezhda , Gontar Alina , Chigirinskaya Nataly
Published: October 2021

Based on the analysis of the functional capabilities of modern information systems, the paper substantiates the applicability of multidimensional combined information structures for computer-assistant planning in machinery production. A multidimensional optimization model has been developed for elementary technological surface-treatment routing in the case of using complex quality indicators determined by the operational properties of products. The dimensions of its coordinate space are determined by the number of technical constraints that govern the quality of the product. The paper provides an example of an algorithm that uses logical algebra operations to reduce the coordinate space of the model and to reduce the computational complexity of the design task.
Development and Optimization of Control Programs for 2.5-Coordinate Milling of Three-Dimensional Workpieces on CNC Machines
Authors: Averchenkov Andrey , Koloshkina Inna , Sheptunov Sergey
Published: October 2021

The paper presents new methods for optimizing milling operations on CNC machines when programming in CAM-systems, in particular, a method for improving the efficiency of processing three-dimensional workpieces by 2.5-coordinate milling on CNC machines for contour machining and a method for improving the productivity of contour milling of products with a variable allowance at a constant optimal value of the chip thickness, with the provision of geometric parameters of surface quality. Mathematical dependences of the surface quality parameters on the milling conditions are determined. Algorithms of automated analysis are presented, and methods for designing such operations are developed.
Application of Multi-Contour Cutting in Algorithms for Solving the Cutting Path Problem
Authors: Tavaeva Anastasiia , Petunin Aleksandr , Polishchuk Efim
Published: October 2021

The cutting path problem for CNC sheet metal cutting equipment is considered in this article. The method of multi-contour cutting application is described for solving Cutting Path Problem (CPP). The method is to be combine contours in «blocks» (groups) and cutting of several contours is performed by using special cutting techniques (common cut, «chained» cutting) in order to reduce values of cutting tool length and number of piercings compared with standard cutting technique (where only idle path is minimized) The article presents results of solving cutting path problem computing experiments using proposed method (multi-contour cutting with common cut) and algorithm CCP-Relax (in which the standard cutting technique is used). The examples of testing are performed by using several instances from Library CPPLib.
Physical modeling low-waste technological process of the round forging hot stamp
Authors: Telegin Igor , Telegin Viktor
Published: October 2021

The paper presents the results of an experimental study highly efficient technological process manufacture of the round forging on a crank hot-stamping press. The high efficiency of this technological process is achieved by reducing its metal consumption. To this end, at the final stamping transition, the forging forging radii were reduced and, accordingly, the allowances for subsequent machining were minimized.
Researches of the Dynamics of Cutting Through of the Material by a Water-Ice Jet
Authors: Burnashov Mikhail , Tryastsin Anton , Stepanov Yuriy , Kuzin Vitaly
Published: October 2021

Hypersonic ice abrasive water jet cutting is a subject of great attention in the production industry. The paper presents some mathematical equations for determining energy parameters of ice water jet cutting. The mathematical model presented in the article can be used for developing a technology for cutting, strengthening, cleaning, or destructing various materials.
Analysis of Influence of Scale Factor and Design on Performance Characteristics and Stress Strain State of Micro Sensing Element
Authors: Kotelnikov Mikhail , Schenyatskiy Aleksey , Basharova Anna
Published: October 2021

A new type of semitoroidal type sensing element is discussed in this scientific article. In the study, possible modes of vibration were identified and a working one was selected. A dynamic analysis was carried out and it was established what force is necessary to excite the resonator in order to ensure both the vibration amplitude that is convenient for reading, and the strength of the resonator. The study of the influence of the scale factor on the performance characteristics and stress strain state of the micro SE was carried out. The SE sizes were changed proportionally. The simulation was carried out with seven options concerning sizes, the calculation was performed with the help of the finite element method, for each individual case, and the results were tabulated. Based on the results obtained, graphs were plotted and conclusions were drawn concerning the influence of the scale factor on the performance characteristics and stress strain state of the device. After that, tasks were identified for further study of micro SE, as an advanced model. Finally, the references including eight sources were given.
Investigation on Fabrication of SS316 Gear by Wire-EDM
Authors: Gupta Kapil
Published: October 2021

Manufacturing of miniature gears with good accuracy and quality, and at low cost is a challenging task for traditional manufacturing processes. Wire-cut electric discharge machining (WEDM) has the capacity to machine any conductive material to fabricate typical shaped products like gears with high level of accuracy and quality. In present research, stainless steel (SS) alloy 316 is used to fabricate miniature gears by WEDM. The experimental array is designed according to Response Surface Methodology (RSM) based central composite face centered (CCFC). Four input parameters namely servo feed (SF), duty factor (DF), servo voltage (SV) and wire feed (WF) with three levels each are used for experimental array to investigate the process performance in terms of cutting rate (CR), and product i.e. gear quality in terms of mean roughness depth (Rz) and dimensional deviation (DD). After WEDM parameter optimization, confirmation experiments are performed at the parametric setting by considering equal importance to all response variables. A very close agreement between the experimental and predicted values have been observed.
Increased Wear Resistance of High-Speed Tools Due to Diffusion Discrete Oxidation
Authors: Chekalova Elena A. , Zhuravlev Andrey V.
Published: October 2021

Comparative studies of the effect of discrete surface hardening by standard ion-plasma technology and discrete oxidation technology on wear resistance have been carried out. Metallographic studies have shown that discrete oxidation has a polycrystalline structure. It was found that the technology of discrete oxidation makes it possible to increase the hardness by 31% in relation to the uncoated material, and the wear resistance of the cutting tool with oxidation is 1.5-3 times higher than that of the tool hardened by the standard ion-plasma technology.
Method of Predicting the Polymer Composites’ Properties Using Neural Network Modeling
Authors: Vdovin D. , Abramochkin A. , Borodulin A. , Nelyub V.
Published: October 2021

A neural network modelling technique and its training to diagnose polymer composite materials based on tomography data is introduced. As an object of study, carbon fiber made by vacuum infusion technology using an epoxy binder is considered. X-ray microtomography was used to analyze its structure and the provided images were used as a database for creating a neural network. A neural network modelling technique and its training was developed, including an algorithm for converting tomograph images into data on the structure of the phase composition and the physical and mechanical properties of the object under study.
Analytical Study of the Process of Dissolution of Silicon from a Modifier Particle
Authors: Boldyrev Denis , Kharchenko Maksim , Amirov Ruslan , Bokov Anton
Published: October 2021

The process of dissolution of a particle of a ferrosilicon modifier in a cast iron melt is considered, taking into account such a physical analogy as the distribution of heat from a point source in space (an infinite body).
Electroplating of Chromium Incorporating High-Dispersion Black Carbon Particles
Authors: Vodopyanova S.V. , Mingazova G.G. , Fomina R.E. , Sayfullin R.S.
Published: October 2021

Electrochemical composite coatings allow successfully solving many practical problems of surface-hardening of structural parts and their tooling components, as well as renewing their fast-wearing components. Electrochemical chromium-matrix composite coatings are used to enhance the thermal and wear resistance of steel articles and parts operating in friction conditions and under increased temperatures, but under low shock loads.

This paper presents the results obtained from studying how fine black carbon particles affect the properties of composite coatings. Optimal conditions are found for producing high-quality coatings, such as the suspended electrolyte mixing rate and graphite concentration in electrolyte. We have also studied how heat treatment affects the microhardness and surface morphology of coatings. High-dispersed black graphite can be used to produce chromium-matrix composite coatings having increased microhardness and wear resistance.
Evaluation of the Ratio of Heat Exchanging Tube Finning on Heat Exchanger Efficiency
Authors: Khizhov Mihail , Mironova Lubov
Published: October 2021

For the purpose of thermal and hydraulic and aerodynamic testing of the heat exchanger tube bundles, various full-scale tube specimens with different finning ratio have been proposed. Formulas that allow to evaluate the effect of the ratio of heat exchanging tube finning on the heat exchanger efficiency are presented.
Leveling Out the Effect of Sample Runouts on Wear when Testing on the SMT-1 Friction Machine
Authors: Pogonyshev V.A. , Torikov V.E. , Mokshin I.A. , Pogonysheva D.A. , Boiko A.A.
Published: October 2021

The research is aimed at improving the quality of testing the tribotechnical characteristics of materials on the SMT-1 friction machine. Testing the bearing materials according to the disc-pad model may be incorrect due to sample runouts. The aim of this work was to level out the influence of sample runouts on wear and other tribotechnical characteristics of friction units.
Analysis of the Effectiveness of Quality Management Tools Aimed at Risk-Management of Organizations
Authors: Ostapenko Maria , Kholboeva Umida
Published: October 2021

Risks are often associated with negative situations that can lead to threats to the continued performance of an organization. To reduce, analyze and evaluate, various methods and systems of risk management appeared, which in recent decades have become the goals of enterprises and have formed whole systems of risk management included in the main direction of modern management. In this paper, the main methods, as well as modern models of risk management, are considered, and the method for assessing and analyzing risks of an enterprise is developed. Due to flexibility and simplicity of the applied tools for creating a theoretical method, it can be integrated and adjusted to any organization’s requirements.
On One Method for Constructing a Programmed Trajectory in Problems of Stabilizing a Spacecraft
Authors: Lamotkin Alexey , Misura Natalia , Mityushov Evgenij
Published: October 2021

A method is proposed for constructing a programmed trajectory in the problems of stabilizing a spacecraft in a fixed time. The method allows constructing a programmed motion, because of which the spacecraft is stabilized in rotational motion around the axis of dynamic symmetry, and this axis is oriented along the local vertical. The proposed algorithm is based on the possibility of representing the unit sphere of quaternions in four-dimensional space as a ball with a radius in three-dimensional space. This makes it possible to obtain a visual representation of the spacecraft rotation trajectory.
Computer-Aided Design of Intermittent Kinematics Mechanisms
Authors: Sobolev Alexander , Nekrasov Alexei , Arbuzov Michael , Rivkin Alexei
Published: October 2021

An overview of the application of intermittent kinematics mechanisms in modern technology is given. Approaches and methods of computer-aided design of intermittent kinematics mechanisms using CAD systems are considered. Based on the results of the performed automated modeling, the manufacture of intermittent kinematics mechanisms for use in the educational process of the university was carried out.
Simulation Modeling Features of Various Machine-Building Enterprise Types
Authors: Dolgov Vitaly , Nikishechkin Petr , Ivashin Sergey , Dolgov Nikita
Published: October 2021

The paper considers the simulation modeling features of various types machine-building enterprises. A tool set for building simulation models of various production types is proposed. A method of a combined approach for simulation model implementation of mixed production types is proposed and described.
The System of Automatic Control of Fuel Supply to the Boiler at the Thermal Power Plant
Authors: Dmitrieva Valeria , Sizin Pavel , Dzyuin Dmitry
Published: October 2021

The article is devoted to the analysis of the technological process of heat load control and cost-effective fuel combustion in furnaces of drum steam generators at a thermal power plant. The object of automation – boiler unit type “Е-75-3,9-440G” – is analyzed. The mathematical model of fuel and air supply system to the steam generator is developed according to installed equipment characteristics. The model’s parameters are calculated. The actuating element of the system is an electric single-turn mechanism designed to actuate shut-off and control valves in the fuel and air supply channels. Two-channel control system is synthetized for providing an optimal ratio of fuel and air consumption with oxygen content correction in the flue gases. The automatic control system model is realized in Matlab application package, Simulink programming environment. The achieved results show the right settings for cascade control system. In conclusion, an example of the necessary technical equipment complex is listed for technical implementation of the developed control system.
Parametric Optimization of Load Bearing Elements for Composite Wing of an Unmanned Aerial Vehicle
Authors: Aung Naing Lin , Tatarnikov Oleg , Aung Phyo Wai
Published: October 2021

This paper describes the optimizing results of structural elements of the composite wing of an unmanned aerial vehicle. The thickness and composite lay-up structure of load-bearing elements and wing skin are determined using the ANSYS software package. The optimal structure is presented using the Pareto set method of the “ideal center” basing on four criteria: minimum mass, deflection, normal stress, and maximum safety factor of the wing. Verification calculations were carried out to determine the safety factor of the load-bearing wing structure using a geometrically nonlinear model in FEMAP software.
Substantiation of the Absolute Velocity of the Soil Thrown by a Spherical Disc of the Roller of a Ridge Roller Planter
Authors: Zykin Evgeny , Kurdyumov Vladimir , Lazutkina Svetlana
Published: October 2021

For the finishing operation of the formation of the soil ridge of the required parameters and density simultaneously with sowing, a tillage roller has been designed, the novelty of which is confirmed by the patents of the Russian Federation No. 194330, No. 194348, No. 196712. The design of the roller assumes the regulation of the attack angles of the spherical discs and the amount of compression of the spring, because these parameters have a significant impact on the geometric dimensions of the formed ridge and the density of the soil in it. The proposed roller is mounted on the rear bead holder of a sowing gang of the ridgeroller planter. Moving along the surface of the field, the coulters of the ridge roller planter sow seeds on a wet compacted bed, the ridge formers form a loose soil ridge above the sown seeds, and the rollers compact the soil ridge. The speeds and forces acting on the spherical disc of the roller have been determined. It has been theoretically revealed that the absolute velocity of soil particles thrown by the edge of a spherical disc towards the longitudinal axis of symmetry of the soil ridge is maximum and depends on the angular speed of the spherical disc, its radius and angle of attack, as well as the frictional properties of the soil. The absolute speed of soil particles thrown from a specific point of the considered working body of the roller decreases when they approach the center of the spherical disc.
An Experimental Study of the Thermal State of a Steel Billet during Hot Rolling
Authors: Dema Roman , Koldin Alexandr , Banschicov Vasily , Murzabaev Timur , Amirov Ruslan , Suvorova Elena
Published: October 2021

The technology of hot flat rolling is a complex technological process that includes multiple shaping of a steel billet, the temperature of a bullet ranging from 1100 to 900 degrees [1-6]. To deform a workpiece, mill rolls are used. The control over a workpiece thermal state is an important task aimed at the quality of its manufacturing [7-13]. To achieve the goal, a mathematical model is developed for calculating a steel billet thermal state. The model makes it possible to determine a temperature distribution along the whole length of a workpiece. The study results are useful for researchers and developers of the hot rolling technology, and they can be applied in the organization of the rolling process with an allowance for the temperature distribution. Based on the results, the parameters of steel billet production can be adjusted or changed [14-18].
Comparative Analysis of the Selection of Lay-Up Stacking of Polymer Composite Load-Bearing Elements for the Tail Section of Fuselage Structure of the Light Aircraft
Authors: Htet Tun Lin , Prosuntsov P.V.
Published: October 2021

The problem of the selecting the optimal lay-up stacking of polymer composite materials for the load-bearing elements of the rear part of fuselage structure is considered. The comparison of two approaches to the design of the load-bearing elements is carried out. The first of them is the use of multilayered composite material for the load-bearing elements, the stacking angles of which is selected from a given discrete set, and the second is the use of composite material with a continuous range of variables in fabric lay-up angles. As a result design optimization, it is shown that using an optimization method with a continuous range of lay-angles allows reducing the weight of the load-bearing elements by 12.79%
The turbulent drag force in superfluid 3He−4He mixtures under oscillations of a quartz tuning fork
Authors: Kapuza S. S. , Chagovets V. K. , Sokolov S. S. , Vrakina V. A. , Chagovets T. V.
Published: October 2021

We have studied the resonance curves of a quartz tuning fork of the fundamental frequency 32 kHz immersed in superfluid 4He and mixtures 3He–4He with 3He concentration of 5 and 15% in the temperature range of 0.35–2.5 K at saturated vapor pressure. Two types of experiments have been carried out, with a tuning fork both not covered by a bulb and coated by a bulb, i.e., in the restricted geometry. In both cases, the velocity-force dependences for the tuning fork showed a linear damping force at low peak velocities and extra drag due to the appearance of vortex lines accompanying the transition to turbulence under increasing peak velocity. These dependencies are mainly determined by the density of the normal helium component. There is a pronounced difference between superfluid 4He and mixtures of 3He in 4He, where 3He impurity particles provide a constant temperature-independent contribution to the normal component of the mixture. The extra contribution to the damping force, so-called “turbulent drag force”, decreases with concentration increase at the same peak velocity of the tuning fork that can be explained by the extension of the range of laminar flow with an increase in the concentration of 3He. We found that the drag coefficient in superfluid 4He and mixtures 3He–4He reaches a plateau at different peak velocities and different exciting forces and explained this fact by different conditions for vortex formation, depending on the different thickness of the near-wall viscous layer. The comparison between the data obtained in restricted and unrestricted geometries shows that there is an excessive dissipation of the tuning fork motion associated with the emission of the first sound wave in unrestricted geometry.
Comparative analysis of the temperature dependences of the resistivity, pseudogap, and thermoelectric power in polycrystals YBa2Cu3O7–δ with a decrease in the density of charge carriers
Authors: Solovjov A. L. , Stepanov V. B. , Kolesnichenko Yu. A.
Published: October 2021

Comparative analysis of the temperature dependences of resistivity ρ(T), excess conductivity σ′(T), pseudogap (PG) Δ*(T), and thermoelectric power S(T), measured on textured YBa2Cu3O7–δ (YBCO) polycrystals with different charge carrier density nf, depending on the level of doping with oxygen, modified by annealing, has been carried out. It is shown that for an optimally doped (OD) sample with Tc = 90 K (sample S1), σ′(T) near Tc is well described by the Aslamazov–Larkin (AL−3D) and Maki–Thompson (MT-2D) fluctuation theories, demonstrating 3D–2D crossover with increasing temperature. The crossover temperature T0 was used to determine the coherence length along the с axis, ξс(0). With a decrease in nf (samples S2 with Tc = 84 K and S3 with Tc = 80 K), the MT contribution is suppressed, and the σ′(T) dependence obeys the Lawrence–Doniach model, which is typical for samples with defects. The dependence Δ*(T) obtained for S1 has a form typical for OD single crystals of YBCO with a maximum at Tpair ∼114 K and a linear section descending to T01 ∼94 K, which limits the region of superconducting fluctuations above Tc. As nf decreases, the shape of Δ*(T) noticeably changes and becomes typical for YBCO films with a symmetric maximum at Tpair, which is the BEC–BCS transition temperature in high-Tc superconductors. As nf decreases, the slope S(T) changes from positive to negative, demonstrating a feature at the PG opening temperature T*. Accordingly, the dependence of S(T)/T on log T changes from linear to nonlinear, which indicates a change in the nature of interactions in the YBCO electronic subsystem with decreasing nf, since S/T ∼1/nf.
Spontaneous decay of artificial atoms in a multi-qubit system
Authors: Greenberg Ya. S. , Shtygashev A. A. , Moiseev A. G.
Published: October 2021

We consider a one-dimensional chain of N equidistantly spaced noninteracting qubits embedded in an open waveguide. In the frame of single-excitation subspace, we systematically study the evolution of qubits' amplitudes if the only qubit in the chain was initially excited. We show that the temporal dynamics of qubits' amplitudes crucially depend on the value of kd, where k is the wave vector, d is a distance between neighbor qubits. If kd is equal to an integer multiple of π, then the qubits are excited to a stationary level which scales as N−1. We show that in this case, it is the dark states which prevent qubits from decaying to zero even though they do not contribute to the output spectrum of photon emission. For other values of kd the excitations of qubits have the form of damping oscillations, which represent the vacuum Rabi oscillations in a multi-qubit system. In this case, the output spectrum of photon radiation is defined by a subradiant state with the smallest width.
Magnetoresistance of graphite nanoplatelets with different structure
Authors: Ovsiienko I. , Len T. A. , Syvolozhskyy O. A. , Matzui L. Yu. , Mirzoiev I. G. , Andrievskii V. V. , Beliayev E. Yu.
Published: October 2021

The magnetoresistance of bulk specimens of graphite nanoplatelets obtained by different methods is studied in magnetic fields up to 2.2 T. It has been established that magnetoresistance is negative for graphite nanoplatelets prepared by chemical treatment of source graphite with a solution of potassium permanganate in sulfuric acid. This negative magnetoresistance can be explained in terms of the model of charge carrier's weak localization in a system with imperfect structure. It has been established that the magnetoresistance is positive and independent of temperature for graphite nanoplatelets produced by sonication method. Moreover, magnetoresistance is linear relative to a magnetic field in fields above ∼0.7 T. It is shown that linear magnetoresistance can be explained in the terms of the Abrikosov's model of quantum linear magnetoresistance.
Microsecond melting and revitrification of cryo samples
Authors: Voss Jonathan M. , Harder Oliver F. , Olshin Pavel K. , Drabbels Marcel , Lorenz Ulrich J.
Published: October 2021

The dynamics of proteins that are associated with their function typically occur on the microsecond timescale, orders of magnitude faster than the time resolution of cryo-electron microscopy. We have recently introduced a novel approach to time-resolved cryo-electron microscopy that affords microsecond time resolution. It involves melting a cryo sample with a heating laser, so as to allow dynamics of the proteins to briefly occur in the liquid phase. When the laser is turned off, the sample rapidly revitrifies, trapping the particles in their transient configurations. Precise control of the temperature evolution of the sample is crucial for such an approach to succeed. Here, we provide a detailed characterization of the heat transfer occurring under laser irradiation as well as the associated phase behavior of the cryo sample. While areas close to the laser focus undergo melting and revitrification, surrounding regions crystallize. In situ observations of these phase changes therefore provide a convenient approach for assessing the temperature reached in each melting and revitrification experiment and for adjusting the heating laser power on the fly.
Tuning of the thermal stability and ovonic threshold switching properties of GeSe with metallic and non-metallic alloying elements
Authors: Keukelier Jonas , Opsomer Karl , Devulder Wouter , Clima Sergiu , Goux Ludovic , Sankar Kar Gouri , Detavernier Christophe
Published: October 2021

In order to make 3D crossbar memory architectures viable, selector elements with highly non-linear current–voltage characteristics are required. Ovonic Threshold Switching (OTS) is a highly non-linear phenomenon observed in amorphous chalcogenides, such as GeSe, that shows promise for application in selectors. In this paper, the impact of alloying with metallic (Zr), metalloid (B, Sb), and non-metallic (C, N) elements as a function of their concentration on the thermal stability and switching properties of alloyed GeSe layers is studied. In the case of the thermal stability analysis, the key parameter that is tracked is the crystallization temperature (Tc) of the as-deposited amorphous films since OTS only occurs in amorphous materials. Using a simple metal–insulator–metal type test structure where the bottom electrode is scaled to 6 μm, the OTS properties of the alloyed layers are also compared. The pristine leakage current (Ipris), the first fire voltage (VFF), and the threshold voltage (Vth) were determined using DC and pulsed (AC) measurements. Results indicate that C alloying in combination with sufficiently high nitrogen incorporation can extend the thermal stability above 600 °C with only low dependence on the C content. Among the metallic and metalloid elements, crystallization temperature is strongly dependent on alloying concentration. In general, larger concentrations are needed to obtain a Tc above 400 °C as compared to CN alloying. Electrical characterization indicates strong dependence of the first fire voltage and the leakage current on the metallicity of the alloying element with only small to moderate concentrations required to influence electrical properties.
Single crystalline Sn2Nb2O7 films with Ti-doping fabricated by pulsed laser deposition
Authors: Ito H. , Fujita T. C. , Kawasaki M.
Published: October 2021

Sn2Nb2O7, a pyrochlore oxide, is expected to have a peculiar flat band structure that can be a source of intriguing physical properties. We have prepared Sn2Nb2O7 thin films by pulsed laser deposition on Y-stabilized ZrO2(111) substrates by finding a growth window at low growth temperature (∼450 °C) and higher laser fluence, possibly due to the rather high volatility of stannous oxide. By Ti-doping, the lattice constant shrinks due to the smaller Ti4+ ion compared with Nb5+. Optical measurements capture an absorption edge at ∼2.6 eV originating from the transition from the Sn-5s and O-2p hybridized valence band to the Nb-4d conduction band, which is not observed in LiNbO3. Opposed to the expectation from the Burstein–Moss shift, Ti-doping results in reduction of the bandgap, indicating that the doping results in the formation of in-gap states and does not contribute to injecting mobile carriers.
Modulating power delivery in a pulsed ICP discharge via the incorporation of negative feedback mechanisms
Authors: Smith Carl L. , Nam Sang Ki , Bae Kiho , Lee Jang-Yeob , Shannon Steven
Published: October 2021

Inductively coupled plasmas driven by pulsed RF power have been used by the semiconductor industry for decades as they offer numerous advantages compared to continuous mode discharges. Current state-of-the-art global models characterize the plasma under conditions where power delivery is user defined and typically constant. This work details the development of an integrated global plasma-circuit model, which couples a transient plasma model with a broader circuit model that captures the behavior of the power delivery system. The transient response of electron density ne and the magnitude of the delivered and reflected power is captured for the duration of a pulse event. The plasma model incorporates negative feedback mechanisms that enhance the magnitude of reflected power in the early ON-cycle. These feedback mechanisms include a skin depth-dependent derivation of plasma impedance and a generalized electron energy distribution function. These mechanisms decrease the rate of power delivery and dnedt in the early power on cycle. Data taken in the global plasma-circuit model was benchmarked to hairpin probe measurements that were taken on the NC state’s inductively coupled argon oxygen system. Experimental data were taken using a working gas of high purity argon at pressures ranging from 2.67 to 6.67 Pa, and center point electron densities were measured in the range of 109–1010cm−3.
Study of porous structure and gas permeation properties of micro-spalled metal driven by shock loading
Authors: Han Dongyan , Wu Haowen , Wang Yanjin , Shi Xiaofeng , Jiang Dongdong , Wu Bao , Sun Zhiyuan , He Anmin , Zhou Tingting , Wang Pei
Published: October 2021

Shock-induced micro-jets and micro-spalls on metal surfaces and the subsequent mixing with surrounding gas are of interest for a wide range of applications, such as inertial-confinement fusion and armor design. This study interprets the mixing of micro-spalled metal with gas as the permeation of gas into the evolving porous structure created by micro-spalled liquid debris. A technical route is established based on the combination of fluid mechanics in porous media and shock dynamics. The topology of the porous metal is studied through molecular dynamic simulation, which captures the major characters of a micro-spalling process driven by shock loading. Pore-network modeling is applied to convert the porous structure of the micro-spalled metal into an assembly of pores and throats. Accordingly, the main porous characteristics of the micro-spalled metal are described by five nondimensional parameters, including porosity, specific area, coordination number, ratio of pore to throat radius, and tortuosity. In addition, the permeability of the micro-spalled metal, characterizing its gas-transport capacity, is also determined by directly simulating a single-phase flow throughout the pore network. The evolution of both porous structure and permeability of the micro-spalled metal subjected to various shock conditions is systematically analyzed. Moreover, the dependence of permeability on porous structure is clarified via a sensitivity analysis, which builds a cross-scale connection between the micro-void morphology and gas permeation at continuum level. The results and conclusions of this study could serve as useful references for both the characterization and design of porous samples in future experimental studies on micro-spalled metal-gas mixing.
Assessing trap bias in the endemic Australian genus of freshwater crayfish,
Authors: Skorulis Ayden , Wong Marian Y. L. , Davis Andrew R.
Published: October 2021

Freshwater crayfish are among the most endangered animal groups in the world. Appropriate management requires an understanding of sampling bias when assessing their distribution and abundance. We evaluated the effectiveness of a variety of sampling methods for detecting freshwater crayfish (genus Euastacus) in situ and potential biases towards individual-level traits associated with these methods. We also experimentally manipulated the presence of crayfish within opera house traps to determine the effects of trap residency on capture rate and the characteristics of crayfish approaching the traps. Baited hoop nets and baited remote underwater video surveys (BRUVS) detected significantly more crayfish than did unbaited video surveys (RUVS). Crayfish captured in baited hoop nets were significantly larger than were crayfish measured in the BRUV and RUV surveys, suggesting that hoop nets were biased to capturing larger animals. The experiment demonstrated that a greater number of crayfish entered empty rather than occupied traps; however, there were no differences in their body sizes. We highlight the importance of optimising sampling for freshwater crayfish to ensure reliable and robust population estimates. This is of critical importance as many have highly restricted ranges and face numerous threats. We contend that this will assist in informing conservation strategies to protect aquatic species at risk.
A comprehensive evaluation method for plateau freshwater lakes: a case in the Erhai Lake
Authors: Wen Zhuqing , Li Xia , Liu Bing , Li Tianhong
Published: October 2021

The study first systematically assessed the ecosystem health status of the plateau freshwater lake of Erhai Lake in Yunnan Province of China, using the revised Freshwater Health Indicator methodology, which comprised three components, i.e., “Ecosystem Vitality,” “Ecosystem Services,” and “Governance and Stakeholders.” To better reflect the real health status of the basin, the cask short board effect was considered during aggregation of the indicators. In addition, analysis of the coupling coordination relationship among the three components was conducted to study the mutual influences among them as well as the comprehensive development level of the studied area. Basically, the ecosystem of the Erhai Lake basin remained healthy during the studied period according to the research due to specific measures and actions taken to manage the environmental problems caused by a former local economic development and urbanization process. However, there were still aspects to improve for more sustainable ecosystem management and utilization in the basin. The “short boards” of the Erhai Lake basin show room for improvement in local freshwater ecosystem management and underline governance problems that need to be addressed. Suggestions are provided for the local stakeholders consequently for the more sustainable development of the studied basin.
Dnmt3a-mutated clonal hematopoiesis promotes osteoporosis
Authors: Kim Peter Geon , Niroula Abhishek , Shkolnik Veronica , McConkey Marie , Lin Amy E. , Słabicki Mikołaj , Kemp John P. , Bick Alexander , Gibson Christopher J. , Griffin Gabriel , Sekar Aswin , Brooks Daniel J. , Wong Waihay J. , Cohen Drew N. , Uddin Md Mesbah , Shin Wesley J. , Pirruccello James , Tsai Jonathan M. , Agrawal Mridul , Kiel Douglas P. , Bouxsein Mary L. , Richards J. Brent , Evans David M. , Wein Marc N. , Charles Julia F. , Jaiswal Siddhartha , Natarajan Pradeep , Ebert Benjamin L.
Published: October 2021

Osteoporosis is caused by an imbalance of osteoclasts and osteoblasts, occurring in close proximity to hematopoietic cells in the bone marrow. Recurrent somatic mutations that lead to an expanded population of mutant blood cells is termed clonal hematopoiesis of indeterminate potential (CHIP). Analyzing exome sequencing data from the UK Biobank, we found CHIP to be associated with increased incident osteoporosis diagnoses and decreased bone mineral density. In murine models, hematopoietic-specific mutations in Dnmt3a, the most commonly mutated gene in CHIP, decreased bone mass via increased osteoclastogenesis. Dnmt3a−/− demethylation opened chromatin and altered activity of inflammatory transcription factors. Bone loss was driven by proinflammatory cytokines, including Irf3-NF-κB–mediated IL-20 expression from Dnmt3a mutant macrophages. Increased osteoclastogenesis due to the Dnmt3a mutations was ameliorated by alendronate or IL-20 neutralization. These results demonstrate a novel source of osteoporosis-inducing inflammation.