Proportionality Coefficient Research Articles

Study of cutting temperature during turningof high-hard cast irons

Purpose. To study the forces and temperature in the cutting zone during machining of high-hard cast iron with special prefabricated cutters with brazed niborite and ciborite inserts. To determine the influence of geometric characteristics of the cutting tool, cutting modes and hardness of the material being machined on the temperature. The methods. The research methods were based on the basics of cutting theory and cutting tools, material science properties of the tool and the material being processed. The research stand with special equipment was used. Findings. The nature of the change in cutting forces temperature with depth t, feed rate S and cutting speed v was experimentally investigated. A non-contact method of measuring the temperature in the cutting zone during turning high-hard cast irons of different chemical composition with cutting inserts made of niborite and ciborite PSM has been substantiated. It is shown that different measurement conditions (turning modes, cutting geometry and the degree of blunting of the cutters, hardness and grade of the machined steel) do not allow determining the average proportionality coefficient CQ. The hardness of the material being machined affects the cutting forces and temperature. Under identical turning conditions for cast irons with a hardness of 220 to 610 HB, the temperature increases by 1,9 times. It has been experimentally established that with the growth of normal and tangential forces on the back surface of the cutter as its wear develops, an additional increase in the total cutting force and heat source power is observed –the temperature increases by 1,3 times. The originality. It was found that the increase in cutting temperature is associated with an outstripping increase in heat generation power over the heat removal rate (with a deterioration in the conditions of heat removal from the top of the blade). The influence of the geometric parameters of the tool and the hardness of the material being machined on the temperature during turning of high-hard cast irons has been proved. Practical implementation. The experimental data obtained will make it possible to develop a mathematical model taking into account the geometric parameters of the tool, the hardness of the material being processed, and the power and energy parameters of the cutting process.

Kinematic analysis of a finger-mimicking pneumatic network actuator consisting of parallelogram-shaped chambers

Fast pneumatic network (fast Pneu-Net, fPN) actuators made of silicone materials have aroused increasing attention these years for their promising applications in soft robotics. To enrich current research, we present a novel fPN actuator that consists of parallelogram-shaped chambers and aluminum endoskeleton that takes the shape of human finger. The proposed actuator can bend at multi-positions when inflated, bringing about more degrees of freedom controllability. Additionally, the performed finite element analysis indicates that the parallelogram-shaped chamber that tilts 30° towards the distal end exhibits an increase in deformation for about 11 % compared to the rectangle-shaped counterpart, offering an improved bending performance. An analytical model that based on the pressurized hyperelastic membrane theory is developed to estimate the actuator’s bending angles/profiles at varied pressures. Geometric relation of the chamber interactions upon deformation is discussed depending on whether the lateral walls are contact or not. The stress-strain relation of the elastomer is described using 3-term Yeoh constitutive model. Experimental validations on the theoretical calculations are carried out, from which the coefficient of proportionality that takes into account the effect on deformation caused by the embedded endoskeleton is determined. Furthermore, the Modified Denavit-Hartenberg (MDH) notation is employed to establish the forward kinematics of the actuator, and the numerical calculations are compared with the physical actuator.

Способ экспериментального нахождения коэффициента склоновой эрозии

The article deals with the theory of slope erosion, developed on the basis of the phenomenological law, according to which the intensity vector of soil erosion from the slope is proportional to the absolute value of its height gradient vector and inverse in direction. Since the erosion model includes a phenomenological coefficient of proportionality between the intensity of soil weathering and the elevation gradient, it is necessary to provide a way to find such a coefficient experimentally. Comparison of changes in elevation data obtained during field monitoring with the results of theoretical calculations enables identifying it

Using statistical linearization to optimize a class of semi-active on-off control in a general state space system

This paper uses statistical linearization to analyze a state space system controlled by a class of semi-active on-off control. The control input is proportional to a feedback state, while the coefficient of proportionality is switched based on the sign of the product of feedback state and a control state. The explicit simultaneous equations are derived to obtain the system's statistics. The usefulness of the approach is demonstrated through 4 examples. In the example of vibration isolation system, the analytical best performance of skyhook control is found. In the example of mass damper system, the analytical best performance of groundhook control is presented. In the example of quarter-car suspension system, the skyhook-groundhook control is optimized. At last, in the example of 4-mass system, the clipped-linear-quadratic-regulator control is demonstrated.

Kink Waves in Twisted and Expanding Magnetic Tubes

We study kink and fluting waves in expanding and twisted magnetic flux tubes. We use the thin-tube and zero-beta plasma approximations. The equilibrium magnetic field is force free with a constant proportionality coefficient between the electrical current and the magnetic field. We derive the equation governing the kink and fluting waves in a tube. Using this equation we study the propagation of kink waves in a particular case of a magnetic tube homogeneous in the axial direction. We show that while there is only one propagating kink wave with the phase speed equal to the kink speed in an untwisted tube, in a twisted tube there are two wave modes, accelerated and decelerated. The phase speed of the accelerated wave exceeds the kink speed, while the phase speed of the decelerated wave is less than the kink speed. We also show that the standing modes are defined by the same eigenvalue problem as that in the case of an untwisted tube. Hence, the frequencies of the standing-wave modes are not affected by the twist. This implies that the seismological results based on the observation of the standing-wave mode frequencies remain valid when the twist is taken into account. The only effect of twist is the variation of the direction of polarisation of the coronal magnetic-loop displacement along the loop. As a result, an apparent node can be detected near the loop apex if only one component of the loop displacement is observed. This can lead to an incorrect conclusion that the observed coronal loop kink oscillation was the first overtone, while in fact it was the fundamental mode.

Electronic Kapitza conductance and related kinetic coefficients at an interface between n-type semiconductors

We calculate the Kapitza conductance, which is the proportionality coefficient between heat flux and temperature jump at the interface, for the case of two conducting solids separated by the interface. We show that for conducting solids in a non-equilibrium state, there should also arise the electrochemical potential jump at the interface. Hence to describe linear transport at the interface we need three kinetic coefficients: interfacial analogs of electric and heat conductances and interfacial analog of the Seebeck coefficient. We calculate these coefficients for the case of an interface between n-type semiconductors. We perform calculations in the framework of Boltzmann transport theory. We have found out that the interfacial analog of the Seebeck coefficient for some range of parameters of the considered semiconductors, has a high value of about 10−3 V K−1. Thus this effect has the potential to be used for the synthesis of effective thermoelectric materials.

Cluster‐associate viscosity model of tin chloride in comparison with the Frenkel model

AbstractDetermining the viscosity of inorganic molten compounds like tin chloride is critically important for material processing, chemical synthesis, and energy applications. However, experimental limitations have restricted the development of accurate viscosity models. This study tests a new cluster‐associate model for predicting the viscosity of molten tin chloride across a wide temperature range. The model links viscosity to the structure and dynamics of molecular clusters in the melt. The aim of this study is to establish a correlation between viscosity and cluster formation within a liquid, using tin chloride as an example. The data were calculated using a newly developed equation based on the concept of randomized particles. The temperature range studied was from the melting point to the boiling point. To verify the accuracy of the cluster‐associate model, it was compared with the Frenkel equation using logarithmic coordinates. Simulations were performed on tin chloride, which yielded results showing a linear relationship between the degree of cluster association and the activation energy of fluidity. The proportionality coefficient reflects the activation energy associated with a single cluster. The Frenkel equation in the logarithmic coordinate scale was compared with the cluster‐associate model. The functional dependence and correspondence of these models are indicated by their high coefficient mutual correlation. The proposed viscosity model underwent testing for the entire liquid state range of the substance, and calculations confirmed its validity. This enables reliable use of the suggested model for both high‐ and low‐temperature extrapolation, including the critical point region.

A Ground-Risk-Map-Based Path-Planning Algorithm for UAVs in an Urban Environment with Beetle Swarm Optimization

This paper presents a path-planning strategy for unmanned aerial vehicles (UAVs) in urban environments with a ground risk map. The aim is to generate a UAV path that minimizes the ground risk as well as the flying cost, enforcing safety and efficiency over inhabited areas. A quantitative model is proposed to evaluate the ground risk, which is then used as a risk constraint for UAV path optimization. Subsequently, beetle swarm optimization (BSO) is proposed based on a beetle antennae search (BAS) that considers turning angles and path length. In this proposed BSO, an adaptive step size for every beetle and a random proportionality coefficient mechanism are designed to improve the deficiencies of the local optimum and slow convergence. Furthermore, a global optimum attraction operator is established to share the social information in a swarm to lead to the global best position in the search space. Experiments were performed and compared with particle swarm optimization (PSO), genetic algorithm (GA), firefly algorithm (FA), and BAS. This case study shows that the proposed BSO works well with different swarm sizes, beetle dimensions, and iterations. It outperforms the aforementioned methods not only in terms of efficiency but also in terms of accuracy. The simulation results confirm the suitability of the proposed BSO approach.

Calibrating mid-infrared emission as a tracer of obscured star formation on H II-region scales in the era of JWST

Measurements of the star formation activity on cloud scales are fundamental to uncovering the physics of the molecular cloud, star formation, and stellar feedback cycle in galaxies. Infrared (IR) emission from small dust grains and polycyclic aromatic hydrocarbons (PAHs) is widely used to trace the obscured component of star formation. However, the relation between these emission features and dust attenuation is complicated by the combined effects of dust heating from old stellar populations and an uncertain dust geometry with respect to heating sources. We used images obtained with NIRCam and MIRI as part of the PHANGS–JWST survey to calibrate the IR emission at 21 μm, and the emission in the PAH-tracing bands at 3.3, 7.7, 10, and 11.3 μm as tracers of obscured star formation. We analysed ∼20 000 optically selected H II regions across 19 nearby star-forming galaxies, and benchmarked their IR emission against dust attenuation measured from the Balmer decrement. We modelled the extinction-corrected Hα flux as the sum of the observed Hα emission and a term proportional to the IR emission, with aIR as the proportionality coefficient. A constant aIR leads to an extinction-corrected Hα estimate that agrees with those obtained with the Balmer decrement with a scatter of ∼0.1 dex for all bands considered. Among these bands, 21 μm emission is demonstrated to be the best tracer of dust attenuation. The PAH-tracing bands underestimate the correction for bright H II regions, since in these environments the ratio of PAH-tracing bands to 21 μm decreases, signalling destruction of the PAH molecules. For fainter H II regions, all bands suffer from an increasing contamination from the diffuse IR background. We present calibrations that take this effect into account by adding an explicit dependence on 2 μm emission or stellar mass surface density.

Determination of the critical cyclic fracture toughness for the mode II in mixed fracture of structural steels

The developed method of processing experimental data from tests performed according to the four-point asymmetric bending scheme made it possible to establish the coefficient of proportionality between the modes of failure I and II, which for structural steels is in the range of 2,5÷3. The established longevity before the appearance of the critical speed according to the developed models is within the limits of the natural dispersion inherent in fatigue failure, which indicates the effectiveness of the developed algorithm and the correctness of the determined indicators of resistance to failure. The problem of the appearance of an oblique crack during tests on four-point asymmetric bending has been solved. It can be assumed that about 90% of the growth of an oblique crack is caused by the contribution of the mode of failure II.

Three-Dimensional Unsteady Axisymmetric Viscous Beltrami Vortex Solutions to the Navier–Stokes Equations

This paper is aimed at eliciting consistency conditions for the existence of unsteady incompressible axisymmetric swirling viscous Beltrami vortices and explicitly constructing solutions that obey the conditions as well as the Navier–Stokes equations. By Beltrami flow, it is meant that vorticity, i.e., the curl of velocity, is proportional to velocity at any local point in space and time. The consistency conditions are derived for the proportionality coefficient, the velocity field and external force. The coefficient, whose dimension is of [length−1], is either constant or nonconstant. In the former case, the well-known exact nondivergent three-dimensional unsteady vortex solutions are obtained by solving the evolution equations for the stream function directly. In the latter case, the consistency conditions are given by nonlinear equations of the stream function, one of which corresponds to the Bragg–Hawthorne equation for steady inviscid flow. Solutions of a novel type are found by numerically solving the nonlinear constraint equation at a fixed time. Time dependence is recovered by taking advantage of the linearity of the evolution equation of the stream function. The proportionality coefficient is found to depend on space and time. A phenomenon of partial restoration of the broken scaling invariance is observed at short distances.

Permeability model of fracture network based on branch length distribution and topological connectivity

Fracture networks are of significance in the production of coalbed methane from unconventional reservoirs. However, the complex distribution and geometry of fracture networks make effective predictions of their permeability difficult. This study obtains the shape of a natural fracture network in coal based on a stereomicroscopy experiment and analyzes the structural characteristics of the fracture network using graph theory. The fractal scaling law for the branch length distribution of the fractures and the relationships among the fractal dimensions of the branch length distribution, fracture area, porosity, connectivity, and ratio of maximum to minimum branch length are established. A new permeability model for a complex fracture network is developed based on fractal theory, and two important fracture characteristics, namely, tortuosity and connectivity, are considered. The model is verified using the results of previous studies and seepage tests, and the influence of the fracture network characteristic parameters on the permeability is analyzed. The results show that the permeability increases with increasing porosity, fractal dimension, proportionality coefficient, maximum fracture branch length, and connectivity and decreases with increasing tortuosity fractal dimension and dip angle.

Experimental Calibration of a Homogeneous Substitute Material Model for Reinforced High-Performance Concrete Modeling.

The purpose of this work was to develop a substitute material model for the analysis of reinforced concrete structures. This paper presents proposals to solve the problem of limited calculation time, both to perform simulation models and to perform effective numerical or analytical analyses of structural elements in order to achieve results consistent with experimental results. Achieving this aim is conditional upon the determination of the material model parameters, taking into account the type of structure, the system of reinforcement, and the static strength-deformation parameters of the component materials. A universal procedure is proposed for determining the parameters of the substitute material model on the basis of the homogenization function, in which the homogenization coefficient is assumed as being equal to the effective reinforcement ratio of real reinforced concrete structural elements. In addition, the introduction of a new concrete constraint coefficient to this procedure, which corresponds to the proportionality coefficient of biaxial to uniaxial compressive strength, is proposed. On the basis of the conducted comparative analyses, the possibility of using the hypothetical substitute material model for the design of building elements and structures was confirmed. The average values of the obtained results for individual research series did not differ from the experimental results by more than 8.5%, for both the numerical and analytical models.

A Theory without Space & Time

Einstein would have like a theory with no space and no time; he added that he didn’t know how to do it (Klein & Spiro,1996). I guess that Einstein was not excited by the job, all the more that getting rid of space and time requires having accurate definitions beforehand. This is the case today, but, if it’s quite easy to proceed, we can’t ensure that the replacement leads to significant progress in the theory. It’s no doubt paradoxical that Einstein never defined time and space, neither did contemporary researchers like Stephen Hawking. The lack of definitions about space and time is a real disadvantage, insofar as defining something is saying what it is; otherwise, we don’t know what we’re talking about. For example, what is the physical nature of space as such? What are the physical properties of time? Is time a phenomenon or a concept? In addition, a good definition is supposed to bring some theoretical extensions. For this purpose, the definitions of the second and the meter will be clarified; the signification of the covariance of the parameters in a relativistic situation will be reminded. Our target, getting rid of time and space, is based on two ideas:• Given that the international unit of time is defined in relation to the frequency of the cesium, the term which is related to time will be replaced by a term related to the frequency.• The cesium wavelength is a fundamental constant; it’s of course covariant. It turns out that any length is proportional to the cesium wavelength; the proportionality coefficient, which is a multiple of the cesium wavelength, is invariant. The splitting in two parts is not only an arithmetical trick, it allows circumscribing the covariance.

Analysis of the energy laws of material destruction

The number of parameters that determine the process of destruction of materials in the crushing chamber is significant and difficult to describe by known mathematical laws. Most of the theories that describe the energy consumption of the destruction process are based on empirical indicators and are not supported by the theoretical foundations of the process. The paper provides an analysis of the latest research in the field of material destruction processes, on the basis of which it was established that modern methods of determining the energy of material destruction differ significantly from each other, are based on different energy hypotheses, both according to accepted assumptions and according to the obtained results. Thus, the lack of a generally accepted model of the grinding process and a single method of determining the energy consumption of the process of destruction of materials by crushing machines is the problem that needs to be solved. For this purpose, an analysis of the main classical laws of destruction of materials in the crushing chamber was carried out. Almost all classical laws are described by the use of proportionality coefficients, which take into account the physical properties of the material, friction costs in the machine nodes, heat losses, the amount of material in the crushing chamber and other parameters that affect the destruction process. This leads to the difficulty of determining the influence of individual parameters on the destruction process, in addition, the coefficients themselves do not have a calculation method and in most cases are determined experimentally. Bond's law has the largest number of variations. In which the work index parameter is used as a proportionality factor. However, the parameter of the Bond work index has a wide range of changes, as well as a large number of methods for its calculation. In general, the dependence itself describes well the processes between the zones of fine crushing and coarse grinding. In the work, the limits of the change of the proportionality coefficients for various energy laws were established for the corresponding destruction conditions. The wide limits of the change of the coefficients testify to the significant stochasticity of the process itself, and do not allow a true description of the picture of destruction. One of the options for the intensification of the destruction process is the application of a shock load. The paper considers the dependence for determining the energy consumption during the dynamic destruction of rocks, which makes it possible to assess the advantages and disadvantages of static destruction. The main parameters that have an impact on dynamic destruction are the speed of load application and the geometry of the surface of the working tool. Based on the analysis, it was established that a large number of parameters that influence the crushing process of machines for the production of building materials greatly complicate the creation of a single theory of destruction at this stage of human development. The further development of research on destruction processes in crushing machines is seen in the creation of a stochastic model for describing the kinetics of the destruction process, which will take into account the peculiarities of the destruction process at the micro and macro levels.

Валідація MCNP-моделі формування струму фонової жили детектора прямого заряду у ВВЕР-1000

The article presents the results of the numerical simulation of the signal formation process of the background wires of self-powered neutron detectors (SPND) under the action of gamma radiation in the VVER-1000 core using MCNP code. The validation of the MCNP model was carried out on the results of experimental determination of the current of the background wires of the SPND, obtained at three different power units with VVER-1000 during the fuel campaign. The article also proposes a new gamma-ray method for determining the thermal power of the VVER-1000 reactor (TPR) based on the signals from the background wires of the SPND. TPR is an important safety parameter of VVER-1000, therefore, increasing the accuracy of determining TPR with the introduction of an additional gamma method for its determination is an urgent task, given the plans to increase the TPR of VVER-1000. The results of the experimental determination of the VVER-1000 TPR by the traditional neutron method based on the SPND signals are presented, and problematic issues regarding the error in determining the TPR by the neutron method are pointed out. The article presents the results of modeling to study the influence of the main factors affecting the change in the proportionality coefficient Kgm between the actual TPR and the TPR determined by the gamma method. To improve the accuracy of determining the TPR by the gamma method, a correction model for Kgm is proposed, which takes into account the effect of nuclear fuel burnup on the change in the signal of the background wires of the SPND. Taking into account that the signal of the background wires of the SPND is inertialess with respect to the change in the neutron power of the reactor, the introduction of the method for determining the TPR by the gamma method is promising for the implementation of an additional alternative channel for generating an emergency protection signal in terms of both power and the period of the reactor.

Diagnostics of Transmission Bearing Units Based on Thermal Load Study

Abstract. The operating temperature of the transmission unit is noted to affect its reliability and can serve as a diagnostic criterion. It is proposed to diagnose the transmission unit technical condition by the temperature in the friction zone in order to take into account the influence of air temperature, solar radiation heating and adjacent heat-producing objects. (Research purpose) To ensure the bearing unit controllability based on the thermal load study. (Materials and methods) The study uses the results of calculating the nominal and operational load of the rear power take-off shaft of the Belarus-82.1 tractor. The study uses the three-dimensional modeling and finite element analysis of the temperature distribution under steady-state thermal conductivity conditions. To establish the functional relationship between the temperature in the friction zone and the diagnostic temperature, the method of finite element analysis is used under steady-state thermal conductivity conditions. (Results and discussion) The maximum load modes and temperatures in the friction zone were determined for the 60310A bearing of the power take-off shaft gearbox during aggregation with different agricultural machines such as 4300 Newtons and 2.4 degrees Celsius for FS-2.0U garden cutter (540 revolutions per minute); 4126 Newtons and 40.7 degrees Celsius for Rovatti T3K80/90/2 (540 revolutions per minute) irrigation pump; 956 Newtons and 13.0 degrees Celsius for ROU-6 (1000) manure spreader; 2615 Newtons and 36.6 degrees Celsius for KPRN-3.0A (1000) mower-conditioner. The maximum temperatures as a diagnostic criterion are established in the friction zone, which equal to 41.7 degrees Celsius at 540 revolutions per minute engine speed and 31 degrees Celsius at 1000 revolutions per minute. (Conclusions) Since the direct measurement of the temperature in the friction zone is hardly possible without changing the bearings design, it is proposed to measure the diagnostic temperature on the unit used for mounting the temperature sensor. The coefficient of proportionality k=0.53 of the finite element model is determined. In order to implement diagnostics in an automatic mode, an algorithm is developed for a digital transmission malfunction recorder. Its design is based on the ATmega328 programmable microcontroller and TMP36 temperature sensors. It is found that the digital transmission malfunction recorder provides automatic control of up to seven different transmission units simultaneously, taking into account the ambient temperature.

Geoinformation model of river meandering for predictive mapping

An algorithm for predictive monitoring of the development of "tortuosity" of riverbed, called the process of meandering, is proposed. The algorithm is based on the statement that the riverbed is displaced from its current position along the normal to the dynamic axis of the flow in the direction from the center of curvature in a given alignment, and the displacement is proportional to the curvature, but the proportionality coefficient is not known in advance and must be determined in the process of cartographic monitoring. When using the proposed algorithm, such a well-known phenomenon in hydrology as the emergence, formation and development of meanders, which give the rivebed bizarre shapes, naturally turns out. The numerical implementation of the proposed algorithm, supplemented by predictive mapping of the riverbed deformation in previous years, is able to predict the channel displacement for future periods of time.

Approaches to rational development of analytical methods for mineral raw materials and products of their processing

Background. Russia occupies a leading position in the global extraction of minerals, meeting all the demands of Russian economy. The efficiency of resources development determines the efficiency of both the oil and gas industry, as well as related economic sectors. At any stage, geological prospecting and exploration works are carried out sequentially and assume identification of the quantity, quality, shape and size of the valuable component contained in the deposit. In Russia, the recent trend in the development of laboratory research methods consists in creating and implementing hardware approaches capable of identifying the content of valuable components rapidly and accurately.Aim. To compare the existing approaches for obtaining the proportionality coefficient depending on the specifics of the ore deposit under exploration and to analyze the dependence of the amount of laser sampling of microprobes on the relative standard error of sampling the main general sample.Materials and methods. The Richards–Chechott equation and Demond and Halferdahl works were studied. An analysis of error classes was carried out.Results. The relative standard error of sampling the main general sample was found to decrease with an increase in the number of microsamples (pulses). The number of microprobes of an analytical sample depends on the heterogeneity of the valuable component distribution.Conclusion. An increase in the number of laser sampling of microsamples (pulses) leads to a decrease in the relative standard error of sampling the main general sample. The number of microprobes of an analytical sample depends on the heterogeneity of the valuable component distribution (K, α).

Estimation of rough fracture network permeability using fractal and topology theories

Accurate characterization of the rough fracture network in real rocks is an essential prerequisite for precise estimation of fracture network permeability. The characterization of a fracture network in previous theoretical models is usually based on statistical theory, ignoring the topological characteristics of the real fracture network. In this paper, based on fractal and topological theories, the rough characteristics of real rock fractures are considered, and fracture network branch lengths and connectivity are introduced. A new theoretical prediction equation of fractal permeability for rough fracture networks is derived. Subsequently, the reliability of the proposed theoretical model is verified based on discrete fracture network (DFN) modeling and numerical simulation, and the main influencing factors of the rough fracture network permeability are analyzed. The results show that the rough fracture network permeability theoretical model proposed in this paper can effectively evaluate fractured rock permeability. Connectivity is linearly related to permeability. The better the connectivity of the rough fracture network, the denser the streamlines within the fractured rock and the higher the flow rate. The rough fracture network permeability increases with the increase of connectivity, minimum branch length, maximum branch length, tortuosity, and aperture proportionality coefficient, and decreases with the increase of tortuosity fractal dimension and fracture dip angle. When the branch length ratio lbmin/lbmax is less than 0.2, the larger the fractal dimension of the rough fracture network, the lower the permeability. When the ratio is greater than 0.2, the opposite is true. The sensitivity of the rough fracture network permeability to the fracture dip angle θ and the aperture proportionality coefficient β is higher, while the sensitivity to the fractal dimension Df of the rough fracture network is lower.