bluuebunny/crossref_metadata_2025 huggingface dataset:
Some Conclusions of an Optimal Subdivision Problem
Authors: Zhu Yuyang
Published: April 2023

Let Habe a-gon with unit edges. DivideHa
into b parts:H

a(1), H

a(2), …, H

a(b) and let the division as Δ(a, b). Let dH

a(k) be the diameter of H

a(k),D(a,b)=max{dH

a(k)}1≤k≤b
, ρ(a, b)=infΔ(a, b){D(a,b)}. We use geometric extremum theory to estimate the range of ρ(a, b), and give the result that ρ(a, b)≥[a(b π)−1 cot(π a
−1)]1/2. For any ε >0, there is a b∈N
+, such that ρ(a, b)< [(2 π (27)−1/2+ ε)a(b π)−1cot(π a
−1)]1/2. We also prove that [6(31/2
π
−1)]1/2≤lim
b→∞
b
1/2
ρ(a, b)≤2.
Nonlinear Response of 1D Large-U Charged Bose Hubbard Model in Electric Field
Authors: Zheng Yong
Published: April 2023

The nonlinear response behavior of 1D large-U charged Bose Hubbard model with a reduced Hamiltonian in electric field has been studied. By transforming the Hamiltonian into a tensor-state space introduced via auxiliary spinless-fermions and the sequence of empty- and doubly-occupied states along the lattice, we have discussed the time-evolution behavior of the system, and found that the charge current always shows Bloch oscillations. It is also found that higher-harmonic components, though small in magnitude, can appear in the corrected charge current.
Research and Practice on the Mining Vehicle Loading Evaluation by Single-Line LIDAR Top View Scanning
Authors: Sun Jian , Chai Qingping , Sun Houguang , Peng Yuanhang
Published: April 2023

There are many challenges associated with the manual accounting of mining vehicle loading when installation of weighbridge is impeded by environmental constraints. This article proposes the method that employs the single-line LIDAR, which was fixed at a height, to obtain the top point cloud data of the passing mining vehicles by overhead scanning, and to configurate three-dimensional point cloud models of the materials for rapid accounting of loading. The single-line LIDAR meanwhile develops the management system of the cloud data to analyze and manage the related results, aiming to fulfil the various needs of data backup and query. Tests of proposed method were conducted via evaluating the loading of both unloaded and fully loaded mining vehicles, the test results show that the average absolute error of the loading evaluation is 1.71% and the average consistency error is 0.28%, both of which meet the accuracy requirements of production, and therefore verify the feasibility of the proposed method.
Inspection Route Optimization of Unmanned Aerial Vehicle in the Presence of Electrical Field around the Overhead Line
Authors: Huang Tao , Rao Donglong , Su Junlong , Zhou Miaolin , Wang Hang
Published: April 2023

Planning of unmanned aerial vehicle (UAV) route is vital for quality of the image acquisition and the safety of UAVs in the inspection of overhead lines (OHLs). However, the influence of the electrical field generated by OHLs on the UAV inspection route was not taken into consideration in previous efforts. In this paper, an optimal route planning method is proposed to avoid UAVs flying too close to OHLs. The results in simulation shows that the UAV keep safe distance with the OHLs.
An Ultra-thin, Switchable Ultra-narrow Band Absorber for High-performance Terahertz Sensing
Authors: Yu Zhisheng , Peng Zhen , Zheng Zhesong , Lan Huiting , Feng Shiping , Wang Shixing , Zhang Min , Li Ling , Liang Huawei , Su Hong
Published: April 2023

In this paper, an ultrathin terahertz metamaterial absorber consisting of Au pattern, polyimide and Au film is proposed. Based on the finite element method, the simulation consequences indicate that when its thickness is 9.4 m, there is a narrow absorption peak for the TE wave at 7.73 THz with near-perfect absorption of 99.8% and a full width at half maximum of 0.0896 THz, resulting from impedance matching and plasma resonance. And the absorption switching from a dual-band to a multi-band or a single-band to a dual-band absorption can be achieved for TM and TE waves by changing the incident angle or polarization angle. Furthermore, the absorption can also be switched from 99% to 0% by changing the polarization angles, and has a high tolerance of polarization angle down to more than 20 degrees. In addition, its application in the sensor is also studied at 7.73 THz, where its refractive index sensitivity and thickness sensitivity can achieve 1.2 THz/RIU and 0.065 THz/m, respectively. This might be utilized for monospectral imaging, biological diagnosis, and environmental monitoring.
Error Estimates of High-order Conservative Schemes for the Generalized Nonlinear Schrödinger Equation in One Dimension
Authors: Wang Xi , Hua Dongying , Li Shucun , Li Xianggui
Published: April 2023

In this paper, we use the high-order difference operator Dμ to compensate the central difference operator

δ

x

2

. Then, we discretize time by the time-midpoint method. Fully discrete schemes are obtained for the generalized nonlinear Schrödinger equation. For the high-order methods, conservation of mass and energy can be proved theoretically in the discrete sense. Then, to establish the optimal error estimates without any requirement on the grid ratio, we adopt the cut-off function technique. The error estimates of the schemes are proved to be of O(τ2 + h2(μ+1)) with time step size τ and mesh size h. Some numerical experiments are given to verify the accuracy order. In addition, the dynamics of the generalized nonlinear Schrödinger equation in one dimension are simulated.
Hollow/sponge-core β-carotene-poly-vinylpyrrolidone (PVP) Electrospun Fibers using High-pressure CO2 Electrospinning
Authors: Zhu Li , Wang Tao , Wahyudiono  , Goto Motonobu , Kanda Hideki
Published: April 2023

Polyvinylpyrrolidone (PVP) is used in various applications because of its unique chemical and physical properties, including biocompatibility and low toxicity. In this study, we successfully prepared ethanol solution-based hollow-core β-carotenoid PVP fibers using high-pressure carbon dioxide (CO2) at 5 MPa and 318 K ambient temperature, a polymer solution at 333 K, an 8-cm tip-to-collector distance, and DC voltage of 15 kV. In this study, the morphological and physical properties of the electrospun products were investigated by using scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) scanning spectroscopy, X-ray diffraction (XRD), and differential scanning calorimetry (DSC).
Research on Safety Evaluation and System Development of Tunnel Lining Based on Set Pair Analysis
Authors: Shi Fulin , Cai Shuang
Published: April 2023

Considering the importance of lining thickness in lining safety, and realizing the synchronization of safety evaluation and information development, this paper combines the methods of literature research and field investigation, focuses on six influencing factors, such as the deterioration of lining materials, the deformation of lining and the lack of tunnel clearance, et al. An evaluation index system of structural safety classification is established, and then substantiates each index and defines its quantitative or qualitative evaluation criteria. Through the normalization processing, the state of the evaluation index can be characterized by the normalized value. Analysing the characteristics, structure, relationship, trend and the mode of their mutual connection between the indexes by set pair analysis method, the calculation formula of the connection degree is obtained, and then the set pair potential vector is obtained. According to the principle of maximum set pair potential, the safety evaluation of lining structure is divided into five levels: safe, safer, less safe, unsafe and extremely unsafe. With the help of App Designer tool in MATLAB software, a program suitable for lining safety evaluation is designed and developed independently. Combined with a tunnel project in Chongqing, the above method is used to judge the lining safety of the tunnel project in order to provide a quick way for tunnel safety evaluation.
Numerical Simulations of Air Shock Wave Overpressure Propagation in Shallow-buried Explosion
Authors: Yang Feng , Xu Lixin , Zhai Hongbo , Su Jianjun
Published: April 2023

Shallow-buried explosion is a typical working condition of ammunition. Studying the overpressure propagation law of air shock wave in shallow-buried explosion is helpful to completely characterize the ammunition power in actual combat. In this paper, a numerical model of shallow-buried explosion of cylindrical charge based on Euler method is established in the framework of simulation software AUTODYN, which simulates the formation process of crater when cylindrical charge is initiated under the conditions of different charge amount and different buried depth, and analyzes the propagation law of explosion shock wave in the air. The following conclusions are drawn: compared with the mass of charge, the depth of burial has more influence on the surface air shock wave. According to the simulation data, the empirical formulas related to the peak overpressure of shock wave and the charge, buried depth and horizontal detonation center distance are fitted.
Study of Terahertz Sensing Performance Based on Graphene-DBR Asymmetric Structure
Authors: Lan Huiting , Yu Zhisheng , Zheng Zesong , Feng Shiping , Su Hong
Published: April 2023

Tamm plasmon polaritons have super strong field localization, and can be directly excited by TM or TE polarized light without dispersive devices, whose related technology has become one of the research hotspots nowadays. In view of this, in this paper, a terahertz sensor device based on double-dip detection of Tamm plasmon polaritons is designed. The device is asymmetric structure, which can excite two Tamm plasmon polaritons modes with the different intrinsic energies at the interface between two DBRs and graphene. Through the optimized simulation analysis of its terahertz sensing characteristics, the results show that the reflection spectrum under this structure has two dips at 0.9THz and 1.0THz respectively, and their full widths at half maxima of 0.0361THz and 0.0131THz are relatively narrow. Moreover, their sensitivities are 0.21THz/RIU and 0.41THz/RIU, and the figure of merit can reach up to 5.69RIU−1 and 31.33RIU−1, respectively. Therefore, this research is suitable for high sensitivity terahertz double-dip detection, and has important application prospect in terahertz devices.
Study on the Optimal Reaction Parameters of C4 Olefin Prepared by Ethanol Catalyzed Reaction Based on XGBoost Regression Prediction Algorithm
Authors: Kang Wenkai , An Yaohui , Zhang Linqing
Published: April 2023

The production of C4 olefin by ethanol coupling catalytic reaction has a broad development prospect in the field of renewable energy. In this paper, the influencing factors of C4 olefin preparation process were studied, the influence of temperature and catalyst type on the reaction was analyzed, and the multivariate nonlinear regression fitting model was established under the assumption of ignoring the small probability of experimental error. Then, based on the grey correlation analysis model, the correlation degree between each variable and ethanol conversion rate and C4 olefin selection rate was studied.

Then, using the catalyst parameter variables considered above, the relationship equations between four catalyst parameter variables, temperature and C4 olefin yield were calculated, and the overall constructor model of C4 olefin yield under the joint action of five variables was established by using the constructor method. Finally, using MPai data science platform software based on XGBoost regression prediction algorithm, the established constructor was cross-validated by 50% fold, and the optimal solution of reaction parameters was finally obtained.

Finally, five experiments were selected to improve the experimental control group data and verify the accuracy of the theoretical value of the optimal solution. By changing the catalyst parameters and temperature, a relative control group was added to the experimental group, and the conclusion of the theoretical parameter optimal solution under unrestricted and temperature restrictions was experimentally verified.
Nonlinear Optical Properties of Several π Conjugated Bridge Groups based on Diketo-Pyrrole-Pyrrole: Study on the Length and Symmetry of N-atom Position Substituted Alkyl Chains
Authors: Hong Lin , Zhou Bowen , Meng Xiangxu , Zhang Ding , Jiang Yihua , Liu Dajun , Wang Guiqiu , Hua Jianli , Wang Yaochuan
Published: April 2023

In this paper, three modified π-conjugated bridges, were selected to study the relationship between substituted alkyl chains and two photon absorption ability as well as intramolecular charge transfer property. The modification is on the N-atom position of Diketo-Pyrrole-Pyrrole bridges. Some nonlinear optical measurements as well as several spectra methods, were used. DPP-J0, DPP-J1 and DPP-J2 exhibit cross-section of 5.6 GM, 8.1 GM, and 6.4 GM. The results exhibit obvious relation on the length and symmetry of N-atom position substituted alkyl chains. A pump-probe measurement was operated at 800 nm. Ultrafast dynamics results exhibit slight difference on the intramolecular charge transfer of these conjugated bridge derivatives. The quantum chemical calculations results are well accorded with the nonlinear optical properties. The results obtained may provide some useful information on molecular design and optimization of new advanced materials.
Charge Evolution for N2
+ Ion Passing Through Ag Target
Authors: Wang Shixuan , Wang Guiqiu , Gao Xin , Yi He , Wang Jian , Li Yujiao
Published: April 2023

Charge state is a key factor for the ion stopping and energy deposition. It is helpful to understand the physics mechanics for interaction between ion and target by studying the charge state. In this paper, nitrogen molecular ion charge evolution in Ag target is studied. It is shown that the charge state of the trailing ion is oscillating, while the leading ion doesn’t show the similar behavior due to the wake effects aroused by the electronic exciting of the target electron.
Large Sets of Hamilton Cycle Decompositions of a Class of Uniform Hypergraphs
Authors: Wang Jingming
Published: April 2023

We use the Katona-Kierstead definition of a Hamilton cycle in a uniform hypergraph. We construct a polynomial to find the Hamilton cycle decomposition. Then the existence of large sets of these decompositions is given by using a complete automorphism group.
Study on Modification and Application of Functional Polyurethane in Leather Finishing
Authors: Qin Ying , Liu Yan , Kuang Guankun , Zhou Yuanyuan , Xin Binjie
Published: April 2023

Over last few years, polyurethane (PU) has been applied in many fields by virtue of its mechanical strength, wear resistance, toughness, low temperature flexibility and other characteristics recently. To be more precise, PU materials can be screened through raw materials, improved formulas and so on to obtain the corresponding “customized” products. This gives the product “customizability” and further broadens the use of functional PUs. PU is one of the important coating materials in leather manufacture. This paper explores the academic research status of functional PU and its modification and application in leather production and leather finishing.
Exploring Multiple Strategies towards Luminescent Fibers and Applications
Authors: Zhang Zhihao , Xin Binjie , Yang Xue , Gao Di , Yu Wenjie , Wang Yingwen , Jiang Yuchen , Hou Chao , Huang Peijun , Xun Wenjun
Published: April 2023

Since its invention, luminous fibers have received extensive attention from scientific researchers. Luminous fibers are mainly distinguished by their energy source and are divided into two types active and passive luminous. As an emerging fiber material, luminescent fibers have been used in the military, firefighting, marine transportation, fishing, and other fields; mainly covering the application of each luminescent fiber fabric, light display materials, luminescent fiber components, energy conversion components, intelligent textiles, anti-counterfeit labels, unique clothing, etc. This paper introduces the classification and luminescence principle of luminescent fibers around the research progress of luminescent fibers in recent years and outlines the relevant applications of luminescent fibers.
A Thermodynamically-based Modeling for the Creep and Plasticity of Al 5083 Alloy
Authors: Meng Li , Chen Wufan
Published: April 2023

To ensure a thermodynamic consistency for a constitutive model is a higher request for modeling the mechanical behaviors of materials. This paper conducts a thermodynamic analysis for a creep-plasticity model for Al 5083 alloy. The constitutive equations are derived from the fundamental thermodynamic laws, maintaining a rigorous physical basis of the proposed model. The monotonic tensile and creep tests are introduced for modeling, illustrating the rationality and accuracy of the proposed model.
Dynamics Simulation and Light-Sheet Tomography of Multispecies Ion Coulomb Crystals
Authors: Shen Yong , Zhang Hongshuo , Zhou Yongzhuang , Xie He , Cheng Hang , Zou Hongxin
Published: April 2023

Ions in coulomb crystals are sufficiently cooled and well isolated from the environment, which makes them an ideal platform for the research of high precision spectroscopy. Ion coulomb crystals (ICC) constituted by multispecies ions can provide important information about the nucleus, such as isotope shifts and hyperfine splittings. In order to extract the spectroscopic data with a high precision, the status of ICC needs to be properly evaluated. In this paper, we utilize the molecular dynamics simulation software LAMMPS and the (py) Lion package to simulate the dynamics of ICC with multispecies ions. To make a better comparison between the simulation results and experimental observations, we propose an ICC tomography scheme with the fluorescence light-sheet microscopy. This work can be applied to make better estimation on dynamic parameters of both laser cooled and sympathetically cooled ions.
Petrographic and technological aspects of improving the methodology for alternative determination of the degree of carbonification
Authors: Bezruchko Kostiantyn , Baranovskyi Volodymyr
Published: April 2023

The methodology for determining the earlier proposed indicator of the intensity of the shade of grey (Grey Intensity) as an alternative to the normative indicator of the reflectivity of vitrinite has been improved. The values of this indicator have been analyzed in the polished section specimen on the surfaces of the cut, layering, and tangential sections along the macerals of all three groups (vitrinite, liptinite, inertinite). The studies have been conducted in natural incident light as well as in the light passing through yellow, red, blue, and green filters. A large factual material has analyzed the petrographic and technological difficulties of measuring the Grey Intensity indicator. It is associated with the spatial arrangement of the observation planes of preparations relative to the natural occurrence of coal beds, the surface features of macerals, the influence of chemical (fluidization, gas generation) and tectonic (dynamic metamorphism) processes on the transformation of the gelled substance as the main object of research. Recommendations on the choice of a lens and a platform for measurements have been given, taking into consideration the optical system of incident light. The expediency of using color filters has been considered.
Application of detonation in impulse systems of energy engineering and mining industry
Authors: Vasiliv Stepan , Pryadko Nataliya , Strelnikov Hennadii , Dzuba Sergiy
Published: April 2023

Nowadays the demand for energy needs is constantly growing. Given the fact that most of this demand is provided by non-renewable energy sources, another way of development remains relevant is more efficient use of available resources. One of the areas of effective energy use is swapping deflagration combustion to the detonation process. Due to the rapidity of the detonation, the entropy of the reaction products is lower than that of deflagration combustion. In addition, there are only “fast” reactions, so the molar mass of the products is the minimum possible for a specific fuel mixture. The article considers a special case of the application of the detonation process in a new way of control the thrust vector of rocket engines, shows its effectiveness and features of use. Numerical modeling of the injection of detonation products into the supersonic part of nozzle at different angles was carried out, and the change in relative lateral force over time was determined for each case. It is shown that the control system with discrete control pulses can be used to maneuver the upper stage of the rocket and to destroy hard mineral rocks, to compact soils and materials in compressed conditions.
Assessment of radioactive contamination level of environment in case of accident at nuclear power plant
Authors: Biliaiev Mykola , Rusakova Tetiana , Dziuba Serhii , Lapshin Yevhen , Koval Natalia
Published: April 2023

The accidents at nuclear power plants pose a particular threat to the population and the environment. Accidental emissions at nuclear power plants can cause long-term radioactive pollution of the environment, and the elimination of such pollution can take years. For practice, it is very important to predict the intensity and size of radioactive contamination zones for various scenarios of extreme situations at the nuclear power plants. Such a forecast will identify the most vulnerable areas and develop a response strategy to the situation that has arisen. A numerical model has been built that allows to quickly predict the scale of radioactive contamination of the territory during an emergency release at a nuclear power plant. The model is based on the application of implicit difference schemes for the numerical integration of the equation of convective-diffusion transport of impurities in the atmosphere. The developed model is characterized by the calculation speed. The results of the computational experiment are presented.
Dynamic and mass-exchange parameters of scandium recovery by TVEX-TBP in column mode from the solution after salt chlorinator cake leaching
Authors: Korovin Vadym , Pohorielov Yurii , Shestak Yurii , Valiaiev Oleksandr
Published: April 2023

The paper deals with scandium extraction with Levextrel-type resin named TVEX contained tributyl phosphate (TVEX-TBP) in the column mode from the clarified solution formed after leaching salt chlorinator cake formed at Zaporozhye Titanium & Magnesium Combine Ltd. It was found that TVEX-TBP featured high extraction parameters. Total dynamic exchange capacity was defined. Mass-exchange parameters were calculated for scandium extraction in the column mode taking into account the impact of external diffusion kinetics: time to form the equation concentration front, front parallel transfer time, concentration and kinetic recovery factors, kinetic factor of external diffusion, linear speeds of the solution in the column and the equilibrium concentration front motion. The calculated mass-exchange parameters may be used to design the column cascade for scandium extraction from the clarified leaching solution of the salt chlorination cake in column mode. There are the following advantages of scandium extraction with TVEX-TBF in the column mode in comparison with its recovery in a reactor cascade: simpler hardware design and process control, the possibility to better wash TVEX from impurities, getting a strippant higher Sc concentration, reduced TVEX abrasion.
Prediction of atmospheric air pollution near a coal stack in adverse weather conditions
Authors: Biliaieva Viktoriia , Berlov Oleksandr , Kozachyna Vitalii , Nochvai Volodymyr , Yakubovska Zinaida , Olatoye Oladipo Mutiu
Published: April 2023

Coal piles on the territory of enterprises are long-term sources of dust pollution of atmospheric air. Forecasting the level of dust pollution of the air for such objects is carried out, as a rule, for convection conditions. But during inversion, very high concentrations of dust can occur on industrial sites. The task of assessing the level of dust pollution of atmospheric air at an industrial site during dust emission in conditions of inversion from a coal stack is considered. A three-dimensional equation of convective-diffusion dispersion of contamination in atmospheric air, compatible with the approach of Prof. Berliand M. on determining the value of the vertical diffusion coefficient in the surface layer of the atmosphere for the case of inversion, to model dispersion of dust from a coal stack under inversion conditions is used. Numerical integration of the modeling equation of convective-diffusion transport of contamination is carried out on the basis of the splitting method compatible with the use of a locally one-dimensional finite-difference scheme. The results of a computational experiment to determine dust pollution zones at the Prydniprovsk thermal power station are presented.
Numerical study of parameters of unit for supplying additional gas flow in jet mill ejector
Authors: Ihnatiev Oleksandr , Shevelova Hanna , Strelnykov Hennadii , Blyuss Borys
Published: April 2023

We have carried out numerical simulation of the flow in the jet mill ejector. The features of ejector are an annular unit for supplying an additional gas flow in the form of a confuser section at the inlet to the accelerating tube, as well as a confuser at the outlet of the accelerating tube. In the course of the study, we have varied the length of the confuser section at the inlet and the angle of an additional gas flow supply. We have established the optimal parameters of the unit for supplying an additional gas flow in the ejector, at which it has been the most uniform distribution of the flow velocity at the outlet of the accelerating tube. The use of the ejector scheme under study ensures the alignment of the vortex flow and a stable near-wall layer throughout the accelerating tube. The results of the study can be used to improve the efficiency of the grinding process in a jet mill.
Substantiating the operating parameters for an underground gas generator as a basic segment of the mining energy-chemical complex
Authors: Saik Pavlo , Falshtynskyi Volodymyr , Lozynskyi Vasyl , Dychkovskyi Roman , Berdnyk Mykhailo , Cabana Edgar
Published: April 2023

This paper presents the main aspects of changing the coal mining technology based on the introduction of underground coal gasification technology for the mining-geological conditions of the occurrence of State Enterprise “Lvivvuhillia” coal seams on the example of “Chervonohradska” mine. When conducting analytical studies using the “Material-heat balance of underground coal gasification” software, predictive quantitative-qualitative indicators of the injected blast mixture and gasification products have been determined depending on the structure and elemental composition of the coal seam, host rocks, water saturation of the seam, and water inflow into the gasification channel. The heat energy loss of an underground gas generator during the gasification of thin and ultra-thin coal seams has been revealed. The heat and energy capacity of the underground gas generator has been determined depending on the type of supply of the injected blast mixture to the combustion face “mirror” and the performance indicators of the gas generator segment within the mining energy-chemical complex taking into account the quantitative-qualitative indicators of generator gas and liquid chemical raw material of the condensate.
Water saturation of coal samples during long-term impregnation
Authors: Yelisieiev Volodymyr , Lutsenko Vasyl , Tepla Tetiana , Ruzova Tetiana , Harasek Michael
Published: April 2023

The paper investigates applicability of two mathematical models developed by the authors for calculating the process of long-term impregnation of coal samples. A distinctive feature of the studied samples is low porosity. Considered models are based on single- and three-channel representation of the internal structure of a porous medium. These models were previously used to study the process of long-term impregnation of highly porous materials. At the same time, the three-channel model in most cases showed much better agreement with experimental data. This study revealed some features of these models associated with approximation of the experimental data obtained for the low porous samples. These features consist in the presence of rather small (in some cases) errors in the processing of experimental points by means of single-channel model. At the same time, the refinements obtained by means of multi-channel model cause only slight error decrease. The results suggest that the channel distributions along the radial direction of the investigated coal samples are narrow and have a pronounced peaks close to the obtained average values.
Energy-force interactions in vibroimpact systems
Authors: Shevchenko Volodymyr , Shevchenko Heorhii
Published: April 2023

The energy-force interactions in vibroimpact systems are studied according to the developed universal mathematical model, which simulates multi-mass vibroimpact systems, the masses of which are connected to each other and to a fixed base by nonretaining one-sided and retaining two-sided elastic bonds, with the excitation of these systems by inertial debalanced vibrators driven by a limited power The results of the research indicate a higher efficiency of vibrations of vibroimpact systems in comparison with a non-vibroimpact system of similar parameters. The highest energy efficiency of oscillations of vibroimpact systems and, accordingly, their maximum efficiency takes place at the excitation parameters that precede the disruption of vibroimpact oscillations. At the same time, maximum accelerations and reactions in their elastic bonds are excited in the systems. Based on this, it is necessary to accept the maximum permissible acceleration of the elements of their constructions as criteria for choosing rational process parameters in viboimpact systems, which ensures the reliability and durability of their operation.
Rhenium recovery from highly concentrated sulfuric media using AMR anionite in column mode
Authors: Korovin Vadym , Pohorielov Yurii , Shestak Yurii , Valiaiev Oleksandr , Cortina Jose-Luis
Published: April 2023

The paper deals with the study of rhenium recovery by AMR anionite from model high-acidic sulfuric solution as well as its desorption by ammonia solution in column experiments. Total dynamic exchange capacity was calculated. Experimental data were processed using the Thomas, Yoon-Nelson and Bed Depth Service Time models, basic parameters were calculated. It was found that total dynamic exchange capacity calculated by Thomas fit was the closest to the experimental value. Rhenium desorption was examined using ammonia solution. Rhenium recovery degree and concentration factor were calculated. The elution curve featured a clear peak that allows producing eluate with high rhenium concentration. The presented results may be used when designing technologies for rhenium sorption from different process solutions and during recycling rhenium-containing alloy wastes.
Enhancement of the rock mass quality in underground iron ore mining through application of resource-saving technologies
Authors: Pysmennyi Serhii , Fedko Mykhailo , Chukharev Serhii , Sakhno Ivan , Moraru Roland , Panayotov Vladko
Published: April 2023

Annotation

In terms of mining and geological structure, ore deposits are complex-structured and composed of single, parallel-contiguous ore bodies. The reserves of barren or ore inclusions with the useful component content less than the cut-off grade of the deposit on the whole make 5-12% for natural-rich ores, and 10-15% for natural-lean ores. Application of conventional systems to mining complex-structured ore deposit areas underground reduces the iron content in the mined ore mass by 3-6% in relation to the main content of the useful component in the ore deposit or increases ore losses 1.5-2.0 times of the standard ones. This leads to a decrease in efficiency of mining the reserves, and as a result, a loss of the world sales market. Application of the resource-saving technologies reduces ore losses and dilution in underground mining, thereby reducing the cost of ore mass processing. As compared with conventional systems, the proposed options of mining systems with ore caving enable increasing the average iron content in the mined ore mass by 2.37-7.03% without increased ore production costs. These indicators are confirmed by laboratory tests on models with natural materials, considering the scale of modeling.
Study of parameters and regimes of pressureless flow in a channel with overboard overflow
Authors: Semenenko Yevhen , Medvedieva Olha , Medyanyk Volodymyr , Buketov Valentyn
Published: April 2023

There were studied the changes of pressureless flow parameters: flow rate and height of the liquid layer, within section of the overboard overflow across the side of the channel, as well as the dependence of the length of this link on the parameters of the channel and flow. It was established that when calculating with engineering accuracy the height of the overflow above the side of the channel and the flow rate along the channel from the length of existence of the overflow layer, only the effect of the effective flow coefficient should be taken into account. The dependence of the dimensionless height of the overflow above the side of the channel on the dimensionless length of the overboard overflow has a clear extreme character, and the dependence of the dimensionless flow along the channel on the dimensionless length of existence of the overboard overflow does not have a clear extreme character. The dependence of the dimensionless length of the overboard overflow on the effective flow rate is well approximated by a power function with a negative fractional exponent and it can be characterized by the absence of extrema and curvature change points, and asymptotically approaches zero at infinity.
Studying the geobarier ability of furnace slag
Authors: Frolova Liliia , Khlopytskyi Oleksii , Kashkalda Nataliia , Ivanchenko Hanna
Published: April 2023

Environmental pollution with mining waste containing dangerous metal cations necessitates the development of technologies for their disposal. This study proposes the use of blast furnace slag as a geobarrier for binding heavy metal cations. Such parameters as slag mass, temperature and time were used to determine the degree of binding of ferum and zinc cations when they are present together. A central rotatable composite experimental design was used to verify the results. According to the plan, the experiments were performed and the optimal conditions were determined with the help of statistical analysis. It was noted that a simultaneous increase in temperature and treatment time increases the degree of conversion for both ferric and zinc cations. An increase in the mass of slag leads to a decrease in the temperature and interaction time for ferum and zinc cations. However, for zinc cations, the maximum degree of conversion is 43.3% with their simultaneous presence. Experimental results showed that slag was more effective as a base for binding ferum and zinc cations with a conversion rate of 63.3% in concentrated solutions. The resulting regularities allow, by varying the process parameters, to bind metal cations in their joint presence.
Forecast of the mine workings destruction risks by the radiometric control method
Authors: Slashchov Ihor , Bielikov Anatolii , Kulbach Andrii , Slashchova Olena
Published: April 2023

The stress-strain state of the rock mass affects the content of methane gas and radon aerosols in the atmosphere of mine workings. Therefore, combined control of methane gas and radon in mine workings allows us to monitor changes in the state of the rock massif and to take measures in proper time to reduce the risks of the roadway destruction. Forecasting of rock massif and mine roadway dangerous state is based on the determined features of methane gas emission together with radon decay products into the mine roadways radon decay products. Interdependence between the dynamics of changes in the concentration of methane gas and the normalized concentration of radon is established when range of the deviations from the average value is ± 20%. Abrupt spikes at the range above 40% are explained in prone-to-destruction zones of the rock massif. One of the indicators of the rock massif readiness for dynamic manifestations of rock pressure and the destruction of mine roadways can be a decrease in the concentration of radon decay products Po218 below 5%.
Subresultants and the Shape Lemma
Authors: Cox David , D’Andrea Carlos
Published: April 2023

In nice cases, a zero-dimensional complete intersection ideal over a field has a Shape Lemma. There are also cases where the ideal is generated by the resultant and first subresultant polynomials of the generators. This paper explores the relation between these representations and studies when the resultant generates the elimination ideal. We also prove a Poisson formula for resultants arising from the hidden variable method.
Standardized Cumulative Metrics of Excess Mortality to Monitor Health System Resilience Throughout COVID-19 and Other Respiratory Virus Resurgences
Authors: Magiorkinis Gkikas
Published: April 2023

Monitoring morbidity and mortality in resurgences of respiratory infections poses significant challenges, as shown by coronavirus disease 2019 (COVID-19). For example, case fatality rates and deaths attributed to specific respiratory pathogens are known to suffer from significant biases undermining their comparability through time and space. As a result, it is difficult to evaluate the protective effect of public health interventions or quantify the impact of a resurgence on the general population through direct recording of COVID-19 related deaths. To overcome these limitations, more robust, less-biased metrics, such as all-cause deaths, have been proposed for monitoring the effect of an epidemic over a population and over time. More specifically, metrics of excess mortality over time, which have been used for influenza surveillance in the past, are increasingly considered important for COVID-19 surveillance. Here, we discuss excess mortality surveillance focusing on standardized single-point and standardized cumulative metrics that allow comparability of excess mortality through space and time. We explain why z score allows for comparison of excess mortality between countries and different periods, while cumulative z score allows assessment of excess mortality over long periods. Our commentary reiterates the importance of standardized statistics of excess mortality for COVID-19 surveillance as we move toward a coexistence with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that will allow drawing conclusions from best practices in different health systems and different periods.
Anthropogenic changes to the nighttime environment
Authors: Gaston Kevin J , Gardner Alexandra S , Cox Daniel T C
Published: April 2023

How the relative impacts of anthropogenic pressures on the natural environment vary between different taxonomic groups, habitats, and geographic regions is increasingly well established. By contrast, the times of day at which those pressures are most forcefully exerted or have greatest influence are not well understood. The impact on the nighttime environment bears particular scrutiny, given that for practical reasons (e.g., researchers themselves belong to a diurnal species), most studies on the impacts of anthropogenic pressures are conducted during the daytime on organisms that are predominantly day active or in ways that do not differentiate between daytime and nighttime. In the present article, we synthesize the current state of knowledge of impacts of anthropogenic pressures on the nighttime environment, highlighting key findings and examples. The evidence available suggests that the nighttime environment is under intense stress across increasing areas of the world, especially from nighttime pollution, climate change, and overexploitation of resources.
Intersectionality in African digital organizing: a Ghanaian perspective
Authors: Mohammed Wunpini Fatimata
Published: April 2023

Although there is growing scholarship on intersectionality in African feminist movements, there are still gaps in scholarship on intersectionality on the continent when it comes to various identity categories. I examine intersectionality within the Ghanaian context using African feminisms as a backdrop. I argue that to drive African feminisms toward emancipatory praxes, it is imperative to center identity categories that are often erased from feminist conversations and to pay attention to organizing from these margins to amplify the erased narratives about marginalization. I theorize these silenced narratives drawing on my experiences as a Muslim Dagbana woman and my work in African and Ghanaian feminist digital spaces. Here, I focus on ethnicity as an identity category that is often overlooked within feminist discourses in national contexts in Africa. I point to organizing strategies that can facilitate the centering of identities and feminist issues that have historically been pushed to the margins.
“Fight as a little girl!”: Chilean feminist cyberactivism and its outcome on the agenda
Authors: Lagos Lira Claudia , Bachmann Ingrid
Published: April 2023

While feminist activism in Chile has been historically marginalized from the public debate, a new generation of digitally native, educated, and empowered feminist activists in Chile has embraced social media, algorithms and other technologies to denounce patriarchal order and advance social change toward gender equality. In this article, we argue that such strategy has given visibility to women’s issues in the Chilean public sphere and contributed to important inroads in matters of gender justice.
Intersectionality in/through Nigeria’s feminist hashtag activism
Authors: Faniyi Ololade
Published: April 2023

This article examines Nigerian feminist hashtag activism as this reveals how activists emplace and embody intersectionality in their organizings. I explore how a politics of intersectionality is institutionalized in Nigerian feminist hashtag activism on Twitter by unpacking the narratives that led to the emergence and online production of visibility for some hashtag activism that have shaped local and national politics in Nigeria. I further discuss intersectionality as a critical praxis and analytical strategy influencing activists' hashtag naming, political demands, and self-corrections in response to Nigeria's socio-cultural-political domains. As a feminist activist who has done some groundwork in Nigerian offline and digital spaces, this article draws from my participant/observer perspective.
Incidence and outcomes of emergency intraprocedural surgical conversion during transcatheter aortic valve implantation: Insights from a large tertiary care centre
Authors: Marin-Cuartas Mateo , de Waha Suzanne , Naumann Stefanie , Deo Salil V , Kang Jagdip , Noack Thilo , Hoyer Alexandro , Holzhey David , Leontyev Sergey , Saeed Diyar , Misfeld Martin , Meineri Massimiliano , Ender Joerg , Abdel-Wahab Mohamed , Desch Steffen , Thiele Holger , Borger Michael A , Kiefer Philipp
Published: April 2023

OBJECTIVE

During a transcatheter aortic valve implant (TAVI) procedure, intraprocedural complications that are manageable only by conversion to emergency open-heart surgery (E-OHS) occasionally occur. Contemporary data on the incidence and outcome of TAVI patients undergoing E-OHS are scarce. This study aimed to evaluate early and midterm outcomes following E-OHS of patients undergoing TAVI in a large tertiary care centre with immediate surgical backup availability for all TAVI procedures over a 15-year period.

METHODS

Data from all patients undergoing transfemoral TAVI between 2006 and 2020 at the Heart Centre Leipzig were analysed. The study time was divided into 3 periods: 2006–2010 (P1), 2011–2015 (P2) and 2016–2020 (P3). Patients were grouped according to their surgical risk (high risk: EuroSCORE II ≥ 6%; low/intermediate risk: EuroSCORE II <6%). Primary outcomes were intraprocedural and in-hospital death and 1-year survival.

RESULTS

During the study period, a total of 6903 patients underwent transfemoral TAVI. Among them, 74 (1.1%) required E-OHS [high risk, n = 66 (89.2%); low/intermediate risk, n = 8 (10.8%)]. The rate of patients requiring E-OHS was 3.5% (20/577 patients), 1.8% (35/1967 patients) and 0.4% (19/4359 patients) in study periods P1 to P3, respectively (P < 0.001). The proportion of patients who had E-OHS who were low/intermediate risk increased considerably over time (P1:0%; P28.6%; P3:26.3%; P = 0.077). Intraprocedural deaths occurred in 10 patients (13.5%), all of whom were high-risk. In-hospital mortality was 62.1% in high-risk patients and 12.5% in low/intermediate risk patients (P = 0.007). One-year survival was 37.8% in all patients undergoing E-OHS, 31.8% in high-risk patients and 87.5% in low/intermediate risk patients (log-rank P = 0.002).

CONCLUSIONS

In-hospital and 1-year survival rates following E-OHS are higher in low/intermediate risk than in high-risk patients undergoing TAVI. An on-site cardiac surgical department with immediately available E-OHS capabilities is an important component of the TAVI team.
Aridification, precipitations and crop productivity: evidence from the aridity index
Authors: Malpede Maurizio , Percoco Marco
Published: April 2023

The economic effects of global warming have gained considerable attention in the recent economic literature. While the relationship between rainfall and agriculture is well known, precipitations alone do not capture the soil water availability, which depends on the evaporation of the water (potential evapotranspiration [PET]). This paper presents evidence of the relationship between aridification and agricultural productivity. We show that areas that have experienced increased precipitations have become arider due to increased PET. We then project future aridification patterns. We find that the global arid area will increase by 3.9 per cent by 2040. This implies a global loss of about 20 million tons of maize, 19 million tons of rice, 8 million tons of soybeans and 21 million tons of wheat until 2040 if no action to combat desertification is taken.