bluuebunny/crossref_metadata_2025 huggingface dataset:
Seizure Outcome in Adult Patients with Supratentorial Cavernomas
Authors: Kemerdere Rahsan , Alizada Orkhan , Ayman Tugce , Baran Oguz , Yeni Seher Naz , Tanriverdi Taner
Published: November 2020

Background Cavernomas are usually found in the supratentorial area, and epileptic seizures are one of the presenting symptoms.

Objective This study aims to provide the seizure outcome in adult patients who underwent surgical excision of single supratentorial cavernomas.

Materials and Methods A total of 23 patients with single supratentorial cavernomas were operated between May 2011 and January 2019. Pre- and postoperative seizure semiology, clinical, and radiological findings were collected from medical records. At the last follow-up, each patient was seen during regular visits and clinical variables were noted.

Results The mean age was 37.08 ± 10.5 years, and 11 (57.8%) and 12 (52.2%) were females and males, respectively. Headache (43.5%) and seizure (43.5%) were the most common presenting symptoms. Cavernomas were located on the right side in 13 and on the left side in 10 patients. The most common locations were the frontal (43.5%) and temporal (43.5%) lobes. The mean follow-up in this series was 41.4 ± 30.8 months. Our results showed that surgery was effective in seizure outcome, as almost 70% of patients who had seizure before surgery was seizure free after surgery, and the difference between those who had seizure pre- and postoperative periods was statistically significant (p = 0.0001).

Conclusion Surgery is safe and effective for supratentorial cavernomas. The excision of cavernoma together with the surrounding hemosiderin should be performed to obtain a satisfactory seizure outcome.
Spectral analysis of the Koopman operator for partial differential equations
Authors: Nakao Hiroya , Mezić Igor
Published: November 2020

We provide an overview of the Koopman-operator analysis for a class of partial differential equations describing relaxation of the field variable to a stable stationary state. We introduce Koopman eigenfunctionals of the system and use the notion of conjugacy to develop spectral expansion of the Koopman operator. For linear systems such as the diffusion equation, the Koopman eigenfunctionals can be expressed as linear functionals of the field variable. The notion of inertial manifolds is shown to correspond to joint zero level sets of Koopman eigenfunctionals, and the notion of isostables is defined as the level sets of the slowest decaying Koopman eigenfunctional. Linear diffusion equation, nonlinear Burgers equation, and nonlinear phase-diffusion equation are analyzed as examples.
Broadband radio-frequency transmitter for fast nuclear spin control
Authors: Herb K. , Zopes J. , Cujia K. S. , Degen C. L.
Published: November 2020

The active manipulation of nuclear spins with radio-frequency (RF) coils is at the heart of nuclear magnetic resonance (NMR) spectroscopy and spin-based quantum devices. Here, we present a miniature RF transmitter designed to generate strong RF pulses over a broad bandwidth, allowing for fast spin rotations on arbitrary nuclear species. Our design incorporates (i) a planar multilayer geometry that generates a large field of 4.35 mT per unit current, (ii) a 50 Ω transmission circuit with a broad excitation bandwidth of ∼20 MHz, and (iii) an optimized thermal management leading to minimal heating at the sample location. Using individual 13C nuclear spins in the vicinity of a diamond nitrogen-vacancy center as a test system, we demonstrate Rabi frequencies exceeding 70 kHz and nuclear π/2 rotations within 3.4 μs. The extrapolated values for 1H spins are about 240 kHz and 1 μs, respectively. Beyond enabling fast nuclear spin manipulations, our transmitter system is ideally suited for the incorporation of advanced pulse sequences into micro- and nanoscale NMR detectors operating at a low (<1 T) magnetic field.
Thermal management of solar PV module by using hollow rectangular aluminum fins
Authors: Khan SheherYar , Waqas Adeel , Ahmad Naveed , Mahmood Mariam , Shahzad Nadia , Sajid Muhammad Bilal
Published: November 2020

Some of the recent challenges encountered in research and development of the solar photovoltaic (PV) industry include the decrease in electrical output efficiency of a conventional solar PV module due to the rise in its surface temperature. The main objective of this research work is to enhance and improve the electrical output efficiency of a common silicon-based solar PV module by lowering the operating temperature of the PV module, which was accomplished by attaching hollow rectangular aluminum tubes as a fin to the rear surface of the solar PV panel. The proposed geometrical configuration of tubes helped to increase the PV module heat transfer rate to the surrounding air by increasing the effective heat transfer area without increasing the overall weight of the PV module. In this experimental study, a comparative analysis has been presented for PV modules with fins and without fins. The results obtained from experiments demonstrated that the attached fins reduced the average temperature of the front and rear surfaces up to 8.97% and 8.41%, respectively. The cooling effect produced due to fins improved the open circuit voltage up to 12.97% and the electrical output efficiency up to 2.08%. Furthermore, the results are thoroughly compared with other published studies, which revealed that the proposed configuration is cost effective and structurally sound.
Polarizable and non-polarizable force fields: Protein folding, unfolding, and misfolding
Authors: Kamenik Anna S. , Handle Philip H. , Hofer Florian , Kahler Ursula , Kraml Johannes , Liedl Klaus R.
Published: November 2020

Molecular dynamics simulations are an invaluable tool to characterize the dynamic motions of proteins in atomistic detail. However, the accuracy of models derived from simulations inevitably relies on the quality of the underlying force field. Here, we present an evaluation of current non-polarizable and polarizable force fields (AMBER ff14SB, CHARMM 36m, GROMOS 54A7, and Drude 2013) based on the long-standing biophysical challenge of protein folding. We quantify the thermodynamics and kinetics of the β-hairpin formation using Markov state models of the fast-folding mini-protein CLN025. Furthermore, we study the (partial) folding dynamics of two more complex systems, a villin headpiece variant and a WW domain. Surprisingly, the polarizable force field in our set, Drude 2013, consistently leads to destabilization of the native state, regardless of the secondary structure element present. All non-polarizable force fields, on the other hand, stably characterize the native state ensembles in most cases even when starting from a partially unfolded conformation. Focusing on CLN025, we find that the conformational space captured with AMBER ff14SB and CHARMM 36m is comparable, but the ensembles from CHARMM 36m simulations are clearly shifted toward disordered conformations. While the AMBER ff14SB ensemble overstabilizes the native fold, CHARMM 36m and GROMOS 54A7 ensembles both agree remarkably well with experimental state populations. In addition, GROMOS 54A7 also reproduces experimental folding times most accurately. Our results further indicate an over-stabilization of helical structures with AMBER ff14SB. Nevertheless, the presented investigations strongly imply that reliable (un)folding dynamics of small proteins can be captured in feasible computational time with current additive force fields.
Correlated atomic dynamics in liquid seen in real space and time
Authors: Egami Takeshi , Shinohara Yuya
Published: November 2020

In liquids, the timescales for structure, diffusion, and phonon are all similar, of the order of a pico-second. This not only makes characterization of liquid dynamics difficult but also renders it highly questionable to describe liquids in these terms. In particular, the current definition of the structure of liquids by the instantaneous structure may need to be expanded because the liquid structure is inherently dynamic. Here, we advocate describing the liquid structure through the distinct-part of the Van Hove function, which can be determined by inelastic neutron and x-ray scattering measurements as well as by simulation. It depicts the dynamic correlation between atoms in space and time, starting with the instantaneous correlation function at t = 0. The observed Van Hove functions show that the atomic dynamics is strongly correlated in some liquids, such as water. The effect of atomic correlation on various transport properties of fluid, including viscosity and diffusivity, is discussed.
Perturbative renormalization of the lattice regularized ϕ44 with flow equations
Authors: Borji Majdouline , Kopper Christoph
Published: November 2020

The flow equations of the renormalization group allow one to analyze the perturbative n-point functions of renormalizable quantum field theories. Rigorous bounds implying renormalizability permit one to control large momentum behavior, infrared singularities, and large order behavior in a number of loops and a number of arguments n. In this paper, we analyze the Euclidean four-dimensional massive ϕ4 theory using lattice regularization. We present a rigorous proof that this quantum field theory is renormalizable to all orders of the loop expansion based on the flow equations. The lattice regularization is known to break Euclidean symmetry. Our main result is the proof of the restoration of rotation and translation invariance in the renormalized theory using flow equations.
Performance of an impedance-variable pulsed high-power electron-beam accelerator based on energy efficient transmission
Authors: Min Sun-Hong , Jung Hoechun , Kwon Ohjoon , Sattorov Matlabjon , Kim Seontae , Hong Dongpyo , Kim Seonmyeong , Park Chawon , Cho Ilsung , Kim Minho , Kim Kyeong Min , Hwang Won Taek , Park Seungwoo , Lee Kyo Chul , Lee Yong Jin , Lim Sang Moo , Hong Bong Hwan , Park Gun-Sik
Published: November 2020

Versatile high-power pulsed electron-beam accelerators that meet the requirements of pulsed high-power specifications are needed for appropriate applications in medical industry, defense, and other industries. The pulsed electron beam accelerator comprising a Marx generator and Blumlein pulse forming line (PFL) is designed to accelerate the electron beams at the level of 1 MeV when electrostatically discharging. The performance specifications of Marx generators consisting of a 100 kV DC power supply, R-L-C circuit, and high voltage switch are at a maximum 800 kV. At this time, by using the capacitance mismatching principle between the Marx generator and the Blumlein PFL under the law of preserving the amount of charge, it is possible to generate a high voltage in the form of a square pulse up to about 1.1 MV, as much as 1.37 times the charged voltage of the Marx generator. As a result, energy transmission from the Marx generator with a high efficiency of about 85% to the Blumlein PFL is possible. The aim of this study is that the pulsed high-power electron-beam accelerator can be used to change the diode impedance, and the energy of the accelerated electron beam reaches a level of 1 MeV with the square pulse width of about 100 ns at the flat-top in the range of relativistic electron beam generation. Performance tests were securely carried out by installing a dummy load based on CuSO4 solution varying the diode impedance to deter damage to the circuit by preventing reflected waves from being generated in the load.
Investigation of threshold voltage shift and gate leakage mechanisms in normally off AlN/Al0.05Ga0.95N HEMTs on Si substrate
Authors: Zhang Weihang , Liu Xi , Fu Liyu , Zhang Jincheng , Zhao Shenglei , Hao Yue
Published: November 2020

In this study, normally off AlN/Al0.05Ga0.95N high-electron-mobility transistors (HEMTs) on a Si substrate were fabricated by adjusting the surface states of the heterostructure. The device exhibited an extremely low reverse gate leakage current of 10−7 mA/mm due to the high Schottky-barrier height for Ni/Au on AlN/Al0.05Ga0.95N. A high ION/IOFF of 108 and a low subthreshold slope of 63 mV/decade were attained for this device. Moreover, breakdown voltages of 665 V and 1000 V were reached in these devices, with a gate-to-drain distance of 26 µm, for a grounded substrate and a floating substrate, respectively. In order to evaluate the reliability of the device, bias-induced and temperature-induced threshold-voltage-instabilities were investigated. The threshold voltage of the device shifted with gate bias stress due to electrons in the channel trapped by bulk traps. Thermally activated electrons releasing from traps decreased the threshold voltage with increasing measurement temperature. This indicates that the reliability in the threshold-voltage stability for the normally off device is dominated by the deep traps in epitaxially grown AlN/Al0.05Ga0.95N. Finally, the gate leakage mechanisms in AlN/Al0.05Ga0.95N HEMTs were investigated. The reverse and forward gate leakage was dominated by Poole–Frenkel tunneling and thermionic emission, respectively.
Exploring nanomechanics with high-pressure techniques
Authors: Chen Bin
Published: November 2020

For around three decades, high-pressure techniques have been used to study nanomaterials. In most studies, especially the early ones, x-ray diffraction and Raman and infrared spectroscopy were used to investigate the structural transition and equation of state. In recent years, the exploration has been extended to the plastic deformation of nanomaterials by using radial diamond-anvil-cell x-ray diffraction and transmission electron microscopy. Compared with the traditional techniques, high-pressure techniques are more advantageous in applying mechanical loads to nanosized samples and characterizing the structural and mechanical properties either in situ or ex situ, which could help to unveil the mysteries of mechanics at the nanoscale. With such knowledge, more-advanced materials could be fabricated for wider and specialized applications. This paper provides a brief review of recent progress.
Effect of psychiatric symptoms and male sexual function of couples on the success of treatment for vaginismus
Authors: Baser Emre , Kirmizi Demet Aydogan , Unlubilgin Eylem , Caltekin Melike Demir , Meriç Nurhan Bolat , Tekin Ozlem Moraloglu
Published: November 2020

Background
This study evaluated psychiatric factors and sexual functions of women with vaginismus and their partners during the treatment process. Methods: The study was performed on 110 women diagnosed with vaginismus and their partners. The women underwent cognitive behavioural therapy (CBT), and couples were divided into two groups: successful and unsuccessful therapy. Sexual function in couples was evaluated using the Golombok Rust Index of Sexual Satisfaction (GRISS) in men and the Female Sexual Function Index in women. The psychopathological symptoms of participants were evaluated using the Symptom Check List-90-Revised (SCL-90-R). Results: Of the 110 women in this study, 98 completed CBT and treatment was successful for 59 (60.2%). GRISS scores pertaining to the subscales of infrequency (66.7% and 39.0%), non-communication (56.4% and 22.0%), avoidance (76.9% and 52.5%), impotence (56.4% and 33.9%) and premature ejaculation (64.1% and 32.2%) before treatment were significantly lower in the successful than unsuccessful treatment group (P < 0.05). Furthermore, there was a positive correlation between complaints of impotence and premature ejaculation in men and symptoms of depression and anxiety in men. In the successful treatment group, pretreatment values were lower for the SCL-90-R subscales of anxiety and depression in men and anxiety, depression, phobic anxiety and obsessive compulsiveness in women than in the unsuccessful treatment group. Conclusions: The psychiatric symptoms and sexual functions of couples were found to affect the success of treatment for vaginismus. As such, treatments should be administered in accordance with other symptoms present in couples.
Effects of bi-dopants Ni and Fe on tin antimonide alloy anodes: physico and electrochemical studies
Authors: Lakshmi D , Nalini B , Jayapandi S , Selvin P Christopher
Published: November 2020

The high theoretical capacity of tin antimony (SnSb) alloys in lithium storage has gained a great deal of attention with respect to its application inbattery anodes. , The unstable structure of this alloy in terms of cycling is a huge limitation for this material; however, this can be effectively exterminated by doping with intermetallics. This work reports the improved electrochemical charcteristics of tin antimonide nanoparticles when nickel and iron are incorporated into the matrix. The as-prepared pristine and the Ni and Fe doped SnSb nanoparticles are analyzed in terms of their physiochemical properties via x-ray diffraction (with Rietveld refinement), Raman spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy with energy dispersive x-ray analysis. The absence of any metal oxides in the SnSb: Fe, Ni system is confirmed by the x-ray photoelectron spectroscopy. The prepared alloy is subjected as an anode to cyclic voltammetry analysis for both aqueous and non-aqueous electrolytes, and their performance is satisfactory, exhibiting reversibility and improved specific capacity. Furthermore, the SnSb: Ni, Fe matrix exhibits a high electrical conductivity of 9.27 × 10−4 S cm−1 at room temperature, indicating improved anodic properties.
A practical methodology for enhancement and detection of transient faults in a gearbox without prior fault feature information
Authors: Zhou Xiaoqin , He Xiuzhi , Peng Dikang , Hou Yixuan , Liu Qiang
Published: November 2020

Gear fault diagnosis has been the focus of research in both academia and industry in the past. Due to the complicated structures of gearboxes, the vibration signals collected from the gearbox casings are comprised of multiple sources, in which the fault-related components may be easily masked by the Gaussian and non-Gaussian noises (e.g. random external shocks and gear meshing harmonics). Moreover, fault feature frequencies of interest cannot always be obtained in advance in practical applications. Therefore, it is necessary to choose an appropriate signal processing method for gear fault diagnosis. In this study, a new practical methodology is proposed to extract the transient fault features from a gearbox vibration signal corrupted by complicated interference without prior fault feature information. In the proposed method, a modified self-adaptive noise cancellation (MSANC) algorithm is first developed for removing the interferences of gear meshing harmonics adaptively, which can overcome the shortcomings of the traditional SANC in parameter selection and convergence performance. Based on the de-noised signal, a cyclic spectral analysis tool called the fast spectral correlation and assisted by the multipoint optimal minimum entropy deconvolution adjusted algorithm is then applied to enhance and detect the certain and potential gear faults. The effectiveness of the proposed method is demonstrated by a numerical simulation and two experimental scenarios that are compared to an advanced blind optimal demodulation band selection technique. The results reveal that the proposed methodology has good capability to detect mono- and multiple gear faults under complicated interferences, and can be regarded as an efficient method for practical gear fault diagnosis, especially for applications where the fault feature frequencies are unknown in advance.
Hybrid electrostatic and gecko-inspired gripping pads for manipulating bulky, non-smooth items
Authors: Han Amy Kyungwon , Hajj-Ahmad Amar , Cutkosky Mark R
Published: November 2020

We present hybrid electrostatic and gecko-inspired gripping pads that help robots to lift and carry bulky objects. The directional, gecko-inspired adhesive provides a controllable shear force with low normal force, providing a very high effective coefficient of friction so that items like bags full of groceries and heavy cardboard boxes can be lifted using only 1–2 N of squeezing force. The addition of electrostatics helps the pads to conform to non-smooth surfaces, providing substantially higher shear forces than with gecko-inspired adhesives alone. The electrostatic effect is enhanced by doping the silicone rubber adhesive material with calcium copper titanate (CCTO), except at the contacting faces of the adhesive microstructures, where a smooth surface finish is important for adhesion. We describe the multimaterial fabrication process used to create the new hybrid adhesive and present the results of robotic lifting experiments with non-smooth bulky items.
Organic fluorescent nanoparticles with NIR-II emission for bioimaging and therapy
Authors: Dang Huiping , Yan Lifeng
Published: November 2020

Fluorescence imaging technology in the second near-infrared bio-channel (NIR-II) has the advantages of low light scattering and weak autofluorescence. It can obtain high spatial resolution imaging in deeper biological tissues and realize accurate diagnosis in the lesion. As a new cancer treatment method, photothermal therapy has the characteristics of obvious curative effect and small side effects. However, the hydrophobicity and non-selectivity of many fluorescent materials, aggregation-induced fluorescence quenching, and other problems lead to undesirable imaging results. Here, we reviewed the structure of the NIR-II fluorescent molecules and these dyes whose fluorescence tail emission is in the NIR-II bio-channel, discussed in detail how to realize the redshift of the dye wavelength, including modifying the push–pull electron system, extending the conjugated chain, and forming J-aggregates and other methods. We also summarize some strategies to improve brightness, including responsiveness, targeting, adjustment of aggregation mode, and aggregation-induced emission effect, thereby improving the imaging performance and therapeutic effect of NIR-II fluorescent dyes.
Technology for developing expert modules and DSS comprehensive platform for reliability and risks monitoring in the Oil and Gas Engeneering
Authors: Zemenkova M Yu , Zemenkov Yu D , Golik V V , Belsky S
Published: November 2020

The paper describes the proposed technology for the development of expert modules and DSS for integrated reliability and risk control systems for oil and gas industry, as part of a complex of intelligent technological management of reliability and efficiency of oil and gas systems developed at TIU. All stages of the development of system modules for controlling technical risks, the features of the structure of the decision-making model for DSS, and the components of a static and dynamic expert system for transport and storage of hydrocarbons are considered. The features of creating decision support systems are described, their main functions and decision criteria and their main provisions. As an example, one of the modules of intelligent neural network engineering control for predicting halos of thawing soil in the vicinity of the pipeline and passing communications, and buildings is shown, a model for visualizing processing results is proposed.
Justification of the choice of pump drive for pumping stations of main pipelines, taking into account the principles of energy and economic efficiency
Authors: Zakirzakov A G , Zemenkov Yu D
Published: November 2020

One of the key conditions for the dynamic development of oil trunk transportation is to reduce the cost of pumping whose important component is energy costs. Energy transportation costs can be reduced by choosing an optimal type of the drive for pumping stations during construction and reconstruction of existing oil pipelines. An alternative to the electric drive can be a gas turbine. In foreign countries, oil is transported through the gas turbine pump drive. In the conditions of changes in energy prices, it is necessary to develop a method for comparing types of drives of the pump unit, each of which has its own advantages and disadvantages, in order to compare factors such as technical characteristics of the drive, distance from power sources, and the availability of a gas supply system, etc. Development of the pump drive selection methodology that takes into account international and Russian experience is relevant and will allow us to justify the choice of aggregate drives when designing pump stations.
Directions for improving the motivational mechanics of modern oil and gas production companies
Authors: Chizhevskaya E L , Zemenkov J D , Zemenkova M J
Published: November 2020

In the modern difficult financial situation when the need for highly qualified staff is increasing, the development of effective staff motivation systems is a crucial task. For any enterprise, regardless of its size and scope, it is necessary to update the payment and labor incentive systems as part of formation of a flexible motivational mechanism that allows it to gain maximum profit at minimum costs. For oil and gas production companies, the solution to this problem is complicated by the large number of personnel and a wide range of personnel qualifications, which increases the relevance of the task
Calculation of the speed descrioptions of the upward swirling gas flow in conditions of lateral wind action
Authors: Obukhov A G
Published: November 2020

The paper presents the results of numerical simulation of lateral wind impact on three-dimensional non-stationary air flows in ascending vortex flow of artificially created tornado in the stationary operating mode. The mathematical model represents a complete system of Navier-Stokes equations taking into account the viscosity and thermal conductivity of the moving gas, as well as the effects of gravity and Coriolis. Using the explicit difference scheme and the corresponding choice of initial and boundary conditions, the solutions of the complete system of Navier-Stokes equations in the computational domain representing a rectangular parallelepiped are numerically obtained. All components of gas flow speed are calculated at fixed time points and instantaneous current lines are built taking into account the constant horizontal wind speed. The calculations showed that the result of the wind action on the ascending vortex flow is an unsymmetrical change in the circumferential velocity, its uneven deformation at opposite sections, and the total displacement of the vortex in the wind direction. Besides, the displacement and the curvature of the vertical vortex part in wind direction are established, the “separation” of some instantaneous current lines from vertical rotating part and the area in the vortex center increasing in diameter, free from current lines is fixed. In the studied time change range, the wind resistance of the air vortex and stable operation of the used computational scheme are observed.
Use of methods for water suppression in the Severo-Orekhovskoe field
Authors: Dyagilev V F , Dyagileva T V
Published: November 2020

The subject of the study is the use of methods for water suppression in the productive stratum of the Severo-Orekhovskoe field. Based on the results’ analysis of the use of water suppression methods in the Western Siberia fields, recommendations were developed for the application of these methods in the Severo-Orekhovskoe field. It is shown that only technologies based on gel-and sediment-forming compositions having selective operation in layer-by-layer inhomogeneous stratum meet the conditions of productive strata of the Severo-Orekhovskoe field for all boundary parameters of application. During the study of the specifics of the field-geologic conditions of the Severo-Orekhovskoe field, effective water-shutoff compounds and technologies based on them were proposed: for strata A2-1, A1-3 - gel-forming compounds ACC-1, TSS-1, and “Geopan”. The reagents proposed for use for water suppression operations have a selective effect in layer-by-layer inhomogeneous permeability stratum and have a good filtration in low-permeability reservoirs. The efficiency of using the water suppression technology based on the thermotropic reagent “RV-3P-1” for high-temperature strata BV, JV. It is established that relatively low temperature conditions expand, on the one hand, the range of water suppression technologies. For technologies based on acrylamide polymers (injection of cross-linked polymer compounds, visco-elastic compounds, concentrated polymer compounds, Temposkrin polymer-gel system, etc.), the only limitation is the low permeability of productive strata AB1-2, AB1-3.
Development of the non-stationary waterflooding technology
Authors: Almukhametova E M , Veliev E M , Puchkov A M
Published: November 2020

The article analyzes the non-stationary waterflooding technology. The basic physical principles of the technology are described. The reasons for its low popularity among subsoil users are revealed. The article aims to substantiate the relevance of non-stationary technologies, conduct experimental-industrial works to adapt and create new non-stationary technologies, and determine conditions for their effective application. In the 1990s, Western technologies were widely used in the oil industry. Non-stationary waterflooding was not included in the list of these technologies. Despite its relative simplicity, the practical implementation of the non-stationary waterflooding technology requires preparation works. Non-stationary waterflooding is one of the most knowledge-intensive methods of enhanced oil recovery. Non-stationary waterflooding tends to “age”, i.e. its effectiveness decreases over time, which requires constant changes in the technology and its combination with other methods.
Bottomhole zone treatment by creating pressure pulses at the wellhead of low-viscosity oil pools
Authors: Mingulov Sh G , Mingulov I Sh
Published: November 2020

It is shown that when a borehole fluid surface is impacted by a compressor and receiver, the wave propagates to the bottom hole zone, where its amplitude increases due to the addition of the reflected wave. It was found that if it is necessary to obtain high speeds, it is more expedient to pump down of the liquid using more accessible hydraulic equipment, such as a pumping unit. It is noted that the use of simple and inexpensive supporting equipment allows creating a fluid flow at the wellhead with the required speed.
Algorithms for dynamic stabilization of rear-wheel drive two-axis vehicles with a plug-in rear axle
Authors: Zhileykin M , Eranosyan A
Published: November 2020

Currently, two-axis front-wheel drive vehicles are widely used systems that provide increased stability and manageability by connecting the rear axle and redistributing torque between the driving axles and between the driving wheels of the rear axle. To a lesser extent, drive schemes for rear-wheel drive two-axis cars with a plug-in front axle are common, and, accordingly, the issues of traffic stabilization of such cars are not fully studied. The purpose of this work is to increase the stability and controllability of rear-wheel drive two-axis machines with a plug-in front axle by redistributing torques between the driving wheels. The analysis of the effectiveness of the 4x4 vehicle traffic stabilization system by redistributing torques between the driving axles and the wheels carried out by simulation methods allowed us to establish that the following stabilization methods are the most effective for cars with a plug-in front axle

• a 4x4 vehicle with a plug-in front axle that redistributes torques between the driving wheels of the rear axle (the effectiveness of these stabilization methods is approximately the same)

• a 4x4 vehicle with a plug-in front axle and an automatically locked front-wheel differential;

• 4x4 vehicle with a plug-in front axle with individual braking system for individual wheels.
Analysis of various design methods for unloading a centrifugal pump rotor from axial forces
Authors: Volodin K , Lomakin V
Published: November 2020

This article is devoted to a review of the main methods of unloading the rotor of a horizontal multistage pump from axial forces. Two methods are considered: a hydrofoam and an opposite arrangement of blocks of driving wheels. The drawings are given and a method for compensating axial force for each of them is described. Their advantages and disadvantages are described. General design guidelines are provided.
Practical usage of study results of the porous materials weldability from corrosion-resistant steels when creating stamp-welded products with desired properties
Authors: Tretyakov A
Published: November 2020

It is shown that a significant factor limiting the use of porous powder materials for the manufacture of die-welded products is low tensile plasticity and insufficient weldability. Porous meshing materials (PMM) made of steel 12Cr18Ni10Ti (X10CrNiTi18-10) have the necessary technological and operational properties for the manufacture of permeable die-welded elements. The conditions for the formation of a weld in PMM fusion welding are affected by the porosity and the ratio of the thermal conductivity coefficients along the thickness of the welded edges and in the direction perpendicular to the movement of the welding source. Technologies for argon-arc welding of a heat exchanger-evaporator sleeve, electron-beam welding of filter elements with a housing, which are implemented in the manufacture of preproduction models, have been developed.
Gradient identification method of the model parameters for electrohydraulic servo drive of FESTO learning system
Authors: Kulakov B , Kulakov D , Qi Long
Published: November 2020

Gradient identification method of the model parameters for electrohydraulic servo drive is considered. The method is adapted to be implemented by an experimental complex consists from FESTO hydraulic learning system and Matlab/Simulink. The implementation of the considered identification algorithm in the Matlab/Simulink package is shown.
Research of composition porosity based on 3d-printed frames and impregnated with epoxy resin
Authors: Lopatina Y , Filippova A
Published: November 2020

Annotation. The paper discusses a method of increasing the strength of 3D-printed structures made by the fused deposition modelling process, which consists in vacuum impregnation of printed products in a compound based on epoxy resin. Studied the number of pores in samples obtained by this method depending on the percentage of 3D printing filling and direction of layers relative to the axis of the samples. The porosity of the samples was determined by comparing the theoretical ideal density with the experimental value determined using the hydrostatic weighing method. As a result, it was found that the porosity of the samples lays in the range from 17 to 18.5%. It was also found that with increasing percentage of filling the porosity of the samples increases. It has been suggested that this dependence is associated with a complication of the processes of air release from samples during the impregnation.
Development of an algorithm for determining the main quality indicators of the transition process on the example of a LUDV hydraulic system
Authors: Godorozha S , Protopopov A , Ryabinin M
Published: November 2020

When optimizing hydraulic systems, various algorithms are used, which are based on the control quality indicators selected as target functions. This is why there is a need to automate the calculation of these indicators. The article considers the main indicators of the quality of the transition process, a mathematical model of the LUDV hydraulic system is compiled and its calculation is performed in two mathematical modeling packages in order to confirm the accuracy of the initial data. An algorithm for determining the main quality indicators of the transition process has been developed, which makes it possible to simplify and speed up the optimization process of the considered LUDV-hydraulic system.
Special Case of Destruction of the End Mill Made of HighSpeed Steel Powder
Authors: Nikolaeva E P
Published: November 2020

Comparing with cast steels high-speed steel powder S390 Böhler MICROCLEAN® has better properties, which is determined by the technology of its manufacture: this steel is high-alloyed, contains an increased amount of carbon and carbide-forming metals. In contrast to cast steels, its microstructure has no carbide inhomogeneity. Despite many advantages and long life of steel S390, explained by its balanced microstructure and chemical content, sometimes early tool failures occur. The article provides the grounds for tool failure connected with the peculiarities of heat treatment conduct. The authors establish the influence of a heat treatment mode on the number and content of carbide phases. The authors give recommendations for increasing the tool service life. This article gives the results of the steel macro- and microstructure research. In the course of research hardness was measured and the content of chemical elements was determined. The phase composition was defined with the help of the X-ray diffractometer Shimadzu XRD-6000. The amount of retained austenite was defined by means of the X-ray method of “four peaks” at the diffractometer Xstress 3000. The distribution of chemical elements was studied with the help of a microprobe X-ray analyzer Camebax SX50 while the surface topography was studied with the help of a scanning electronic microscope with the 100-3000-fold magnification.
Effect of Special Misorientations – Crystallographic Ordered Boundaries in Recrystallization in Aluminium Alloy of Al-Si-Mg System
Authors: Reznik P L , Redikultsev A A , Lobanov M L
Published: November 2020

The deformed and recrystallized states of surface regions of hot-rolled aluminium alloy plates of Al-Si-Mg system were investigated by the method of orientation microscopy (EBSD). In the deformed state mainly shear texture components were detected. In the recrystallized structure, there was a significant dispersion of deformation texture due to an increase in the proportion of components that were located at the edges of the deformation texture. It is shown that the crystallites, which are boundary a deformed matrix with the misorientation approximately corresponding to rotation axis <552> at an angle of 52.5°, become the nuclei of recrystallization.
Influence of the Thermal Deformation Treatment on the Structural State and Properties of Ti-Mo Microalloyed Steels of the Ferritic Class
Authors: Zaitsev A I , Koldaev A V , Arutyunyan N A
Published: November 2020

Investigation on influence of thermal deformation treatment on the special features of structural state, phase precipitates, strengthening mechanisms, and mechanical properties was carried out for low-carbon Ti-Mo microalloyed steel of ferritic class. The following parameters were analyzed: the finishing temperature of rolling and the cooling rate of the steel after rolling end to the coiling temperature. Methods of scanning and transmission electron microscopy, thermodynamic calculation, kinetic analysis, and testing of mechanical properties were used. It was shown that with an increase in the cooling rate from 3 to 22 °C/s, the type of carbide precipitates changes from interphase to ferritic. When fast cooling is applied, mainly mechanisms of dislocation and grain boundary strengthening are realized. When cooling is slowed down, the fraction of precipitation hardening increases. It was established that ferritic precipitates make a smaller contribution to precipitation hardening of steel than interphase ones. To create conditions favorable for the formation of interphase precipitates, the rates of γ → α phase transformation and cooling should be close.
Study of Methods for Increasing Ductility and Formability of Cold-Rolled Ti-Stabilized IF Steels
Authors: Zaitsev A I , Rodionova I G , Koldaev A V
Published: November 2020

Study of the influence of the chemical composition and parameters of the complex treatment technology on characteristics of the microstructure, phase precipitates, the solid solution state, and mechanical properties was carried out for hot-rolled and cold-rolled Ti-stabilized IF steels. Cold-rolled products were annealed according to the regime of continuous hot-dip galvanizing units. The following methods of investigation were used: light, scanning and transmission electron microscopy, mechanical properties testing, thermodynamic analysis of phase stability conditions, and determination of the interstitial impurities content in a solid solution by internal friction. The possibility and conditions of a significant increase in ductility, formability of cold-rolled steels are established. They are obtained not by the traditional way consisting in reducing the content of interstitial elements and impurities, but by giving them a favorable form of existence. This is achieved by optimizing the chemical composition, first of all, the sulfur content, and parameters of thermo-deformation treatment of steel, which ensure complete carbon binding in Ti4C2S2 as a result of TiS transformation already at the hot-rolling stage. To reduce the yield and tensile strength, it is necessary to decrease the content of interstitial elements and to increase the temperature of recrystallization annealing of cold-rolled steel.
Thermodynamic Analysis of the Deoxidation Ability of Aluminum in the Melt of the Fe-Cr-C System at 1600 °C
Authors: Mikhailov G G , Makrovets L A , Samoilova O V
Published: November 2020

In the course of the present work, we performed a thermodynamic analysis of the deoxidation ability of aluminum in the melt of the Fe-Cr-C system at 1600 °C using the technique of constructing a special type of diagram - the surface of the solubility of components in a metal (SSCM), which binds changes in the composition of the metal melt with changes in the composition of deoxidation products. The calculation of the SSCM was based on the equilibrium constants of the reactions of the elements with oxygen interaction in a metal melt, as well as on the first-order interaction parameters (according to Wagner) of elements in liquid iron. During the calculation, the parameter e
Al = 0.023 was estimated. Based on the results of the calculation of the SSCM, the concentration regions of the existence of non-metallic phases - deoxidation products in equilibrium with liquid metal were determined.
Thermal Treatment of Cemented Alloyed Steels for the Cold Plastic Deformation
Authors: Astashchenko V I , Shveyova T V , Shveyov A I
Published: November 2020

Disclosed is a method of thermal treatment of blanks from alloyed cement steels for cold volumetric stamping and extrusion. The technology ensures the formation of a ferritic-pearlitic structure in steel with a minimum microhardness of individual structural components. Examples of manufacturing of toothed parts by the method of cold wrapping and thin-walled tubular articles during cold extrusion are given. It is shown that cyclic resistance of parts made by cold plastic deformation and hardened by method of chemical-thermal treatment is increased by three or more times. According to the results of metallographic analysis, the ability of steel to cold plastic deformation and the ability to obtain high-quality machine parts are predicted.
ThermoCalc Modelling of the Effect of Chemical Composition on the Phase Transformations Temperatures of Ti-0.4Al Alloy
Authors: Illarionov A G , Ushakova A S , Vodolazsky F V
Published: November 2020

The effect of chemical composition of Ti-0.4 Al α-titanium alloy (PT-1M alloy) on the phase transformation temperatures up to melting temperature has been investigated using ThermoCalc software. The possibility of appearance of Ti2N nitride, Tix(CN)-type carbonitride, and Ti2Fe-type intermetallic in the alloy structure in equilibrium state has been proved by thermodynamic calculations. It has been proposed the so-called aluminum equivalent (Aleq) for PT-1M alloy to analyze the effect of chemical composition on the phase transformation temperatures change. The following equivalents have been suggested:

Al

eq

Tβ

for

β
↔
(
β
+
α
)
−

transformation,

Al

eq

T
l
i
q

for

L
↔
β
−

transformation, and

Al

eq

Tsol

for

(
L
+
β
)
↔
β
−

transformation. It has been shown the linear correlation between the characteristic temperatures of phase transformations in the investigated alloy and the proposed aluminum equivalents.
Features of Shear Banding in Grains with Orientation {111}<110> in the Fe – 3%Si Alloy
Authors: Lobanov M L , Reznik P L , Redikultsev A A
Published: November 2020

EBSD method were used to study the texture of BCC crystals {111}<110> Fe-3%Si. It is shown that in the state after cold rolling shear bands with habit plane at a slope of ∼ 20 – 40° to the RD were formed as a result of 70% deformation. Theoretical analysis was performed and experimental data were analyzed which showed that the matrix reorientation into orientation {110}<001> occurs when grain stripping with orientation {111}<110>. Such effects are observed either due to rotation around the <100> axis or due to rotation around the <110> axis. By means of dislocation sliding, most of the SBs blocks are reoriented to orientations close to {111}<112>.
Ablative Laser Processing of Metals and Dielectrics in an Electrostatic Field
Authors: Kochuev D A , Raznoschikov A S , Chkalov R V
Published: November 2020

The work considers the task of synthesis of highly dispersed spherical powder granules by laser ablation method. To improve the geometry of synthesized particles and increase the process productivity, an electrostatic system for collecting ablation products was used, which allows the formed particles to leave the area of laser irradiation without being subjected to excessive exposure to a heat source. Using an external field makes particle motion predetermined, ensuring their adhesion to the electrodes. The paper shows the experimental results on the removal of ablated particles, as well as an assessment of the effectiveness of electrostatic field for accelerating particle motion.
Analysis of Steel Slag Composition and Properties to Facilitate the Search for Rational Slag Recycling Methods
Authors: Tyutrin A A , Nemchinova N V , Baranov A N
Published: November 2020

This paper is devoted to the challenging problem of steel slag recycling. This study considers the composition and properties of steel slag, namely, slag of electric and pneumatic steelmaking. Slag of the pneumatic and electric steelmaking was found to be composed of calcium silicate Ca2SiO4, while phosphorus is represented by a complex calcium silicophosphate. Iron is in oxidized forms of FeO, Fe2O3 and Fe3O4 with the following ratios to the total mass of iron oxides, %: 51.51:37.16:11.33 for pneumatic steelmaking slag, and 75.92:20.90:3.18 for electric steelmaking slag, respectively. Chemical composition study showed the following content of the main elements for electric steelmaking slag, mass %: 31.6 – 33.2 Fe; 0.330 – 0.383 P; 19.15 – 19.2 Ca; 4.62 – 5.39 Si; for pneumatic steelmaking slag, mass %: 18.7 – 20.5 Fe; 0.630 – 0.710 P; 27.8 – 28.0 Ca; 4.73 – 5.04 Si. Electron microprobe analysis of slag samples showed the presence of Fe, C, O, P, Ca, Si, Mn, Ti, Cr, and Mg heterogeneously distributed over the sample crosscut surface. Samples had low content of phosphorus, however, this element was found to be accumulated in clusters together with Si and Ca.