Calculation features of compressed-bent build-up timber columns with nonlinear-deformable shear bracings

Object of research is build-up compressed–bent and eccentrically compressed columns on yielding nonlinear – deformable shear bracings. Purpose of the research is development of a numerical method for calculation of columns, allowing to take in account the influence of deflection of elastic axis of bar on the increment of the bending moment from the action of longitudinal compressive force and the nonlinear dependence between the forces and deformations in the shear bracings. Problem-solving method consists in dividing the column into separate sections, a system of equations is compiled from the condition of equality of the increment of concentrated shears. The loading process is divided into a set number of stages, at each forces in the shear bracings, the stresses in the branches, and the buckling function of the elastic axis of the element are determined. The obtained values of forces in the shear bracings and buckling are used to specify stiffness of the bracings and component of the bending moment arising due to eccentric application of the longitudinal compressive force when longitudinal axis of the element is deflecting. To obtain the resulting values, the obtained forces, deflections and stresses in the branches at each calculation stage are summed up.

Static analysis of multi-support spindle shafts with nonlinear elastic bearings

In this paper a mathematical model and computational tool are developed for the static analysis of multi-bearing spindle shafts with nonlinear elastic supports. Based on the Timoshenko beam theory a resolving system of equations is obtained that takes into account the nonlinear dependence of the bearing stiffness on the reaction forces acting upon them. A solution method is proposed and appropriate software is developed that implements the static analysis of multi-support spindle shafts with non-linearly elastic bearings in MATLAB environment. Key words: spindle, shaft, nonlinear elastic support, multi-bearing, nonlinear elastic stiffness, Timoshenko beam.

Spatial Mixture Copula Model For Multiple Correlated Responses With An Environmental Application

In environmental monitoring, multiple measurements are often collected at many locations and these measurements depend on each other in complex ways, such as nonlinear dependence. In this research, a novel copula-based geostatistical modelling approach was developed to model multivariate continuous spatial random fields using mixture copulas that captures both spatial and joint dependence of multiple responses over two-dimensional locations. In a bivariate context, the mixture copulas were used to capture the joint spatial dependence of a bivariate random field and the spatial copula of the bivariate random field was constructed as the convex combination of mixture copulas. The proposed model was applied to real forest data and simulated nonlinear data. The performance of the novel method was compared with existing spatial methods, which included a univariate spatial pair-copula model, a multivariate spatial pair-copula model that utilises nonlinear principal component analysis (NLPCA), and conventional kriging. The results show that the proposed model outperforms the existing methods in the interpolation of individual responses and reproduction of their bivariate dependence.

Informeasure: an R/Bioconductor package to quantify nonlinear dependence between variables in biological networks from an information theory perspective

Using information measures to infer biological regulatory networks can observe nonlinear relationship between variables, but it is computationally challenging and there is currently no convenient tool available. We here describe an information theory R package named Informeasure that devotes to quantifying nonlinear dependence between variables in biological regulatory networks from an information theory perspective. This package compiles most of the information measures currently available: mutual information, conditional mutual information, interaction information, partial information decomposition and part mutual information. The first estimator is used to infer bivariate networks while the last four estimators are dedicated to analysis of trivariate networks. The base installation of this turn-key package allows users to approach these information measures out of the box. Informeasure is implemented in R program and is available as an R/Bioconductor package at https://bioconductor.org/packages/Informeasure.

Results of experimental studies of the mutual influence of tenometric sensors on the plane elements of the road machine design

Analysis of the use of road vehicles in recent years shows an increasing trend continuous mode of their operation. In these circumstances, it is important to know the current technical status condition of the road machine. To a large extent, this is determined by the reliability of the measurement information about dynamic loads on the structural elements of a road machine. In order to increase the accuracy and reliability of dynamic measurements of loads, the authors conducted a number of experimental studies. Experimental studies of the mutual influence of strain gauges on the errors of dynamic load measurements on the structure of the road machine were carried out using a model of the planar element of the structure of the road machine. A computerized four-channel spatially distributed measurement information system was used in the experimental studies. Research results are presented mutual influence of strain gauges under various static and dynamic loads. It is established that due to the action of inertia forces and acceleration, the interaction between the sensors is manifested to a greater extent. Using the methods of comparison, comparison and complex analysis of the results of experimental studies, the dependences of the errors of dynamic load measurements on the angle of action and load removal were established. According to the results of research, the functions of dependence of dynamic loads on the direction and force of action on each of the 4 strain gauges, taking into account their mutual location, are obtained. It is shown that the experimentally obtained coefficient of the interconnection of strain gauges depends on both the mutual location of the sensors and the spatial direction of the force and has a nonlinear dependence. The experimentally determined error function between the four strain gauges was 3%. The reason for the increase in measurement errors of dynamic planar loads is the displacement of the operating point upwards by the transformation function at positive load, or downwards at negative load. The magnitude of the displacement depends on both the magnitude of the load and its removal.The results obtained will allow optimizing the placement and number of strain gauges on board Measuring Information System on the structure of of the road machine. As a result, the accuracy and reliability of measuring the parameters of the dynamic loads of the road machine will significantly increase.

Contact Engineering Approach to Improve the Linearity of Multilevel Memristive Devices

Physical mechanisms underlying the multilevel resistive tuning over seven orders of magnitude in structures based on TiO2/Al2O3 bilayers, sandwiched between platinum electrodes, are responsible for the nonlinear dependence of the conductivity of intermediate resistance states on the writing voltage. To improve the linearity of the electric-field resistance tuning, we apply a contact engineering approach. For this purpose, platinum top electrodes were replaced with aluminum and copper ones to induce the oxygen-related electrochemical reactions at the interface with the Al2O3 switching layer of the structures. Based on experimental results, it was found that electrode material substitution provokes modification of the physical mechanism behind the resistive switching in TiO2/Al2O3 bilayers. In the case of aluminum electrodes, a memory window has been narrowed down to three orders of magnitude, while the linearity of resistance tuning was improved. For copper electrodes, a combination of effects related to metal ion diffusion with oxygen vacancies driven resistive switching was responsible for a rapid relaxation of intermediate resistance states in TiO2/Al2O3 bilayers.

OPTIMIZATION OF STATIONARY AND TRANSITIONAL OPERATING MODES OF THE ELECTRICAL COMPLEX IN METAL PROCESSING LINE

In the electrical complex “induction heater - deforming equipment”, the limiting performance of the complex is the induction heating unit. In this regard, an important task of increasing the effi ciency of the processing complex is to optimize both the design and operating parameters of the induction heating unit. It is shown that the main design parameter infl uencing the energy characteristics of the complex is the length of the heating system. When optimizing the total length of the heater, an iterative model of the process of induction heating of ferromagnetic billets is used. The power distribution algorithm along the length of a two-section heater is a piecewise continuous function. Optimization of the heater length according to the proposed method made it possible to reduce the heater length from 2.8 m to 2.1 m, i.e. by 25%. To search for eff ective control algorithms for non-stationary modes, a refi ned electrothermal model is proposed in the work. It takes into account the nonlinear dependence of the distribution of the power of the sources of internal heat release on the temperature distribution in the metal of the workpieces along the radial and axial coordinates. The problem of fi nding the optimal control of transient modes of a two-section induction heater of methodical action is formulated and solved. The results obtained provide a minimum of energy consumption for heating billets in transient modes under conditions of technological and energy constraints. Variants of starting the heater at various initial temperature states of the load are considered. The results of a comparative analysis of the eff ectiveness of the obtained control algorithms are presented. The structure of the power supply and control system of the induction heating complex is proposed.

Managing and Utilizing Big Data in Atmospheric Monitoring Systems for Underground Coal Mines

Underground coal mining Atmospheric Monitoring Systems (AMS) have been implemented for real-time or near real-time monitoring and evaluation of the mine atmosphere and related parameters such as gas concentration (e.g., CH4, CO, O2), fan performance (e.g., power, speed), barometric pressure, ambient temperature, humidity, etc. Depending on the sampling frequency, AMS can collect and manage a tremendous amount of data, which mine operators typically consult for everyday operations as well as long-term planning and more effective management of ventilation systems. The raw data collected by AMS need considerable pre-processing and filtering before they can be used for analysis. This paper discusses different challenges related to filtering raw AMS data in order to identify and remove values due to sensor breakdowns, sensor calibration periods, transient values due to operational considerations, etc., as well as to homogenize time series for different variables. The statistical challenges involve the removal of faulty values and outliers (due to systematic problems) and transient effects, gap-filling (by means of interpolation methods), and homogenization (setting a common time reference and time step) of the respective time series. The objective is to derive representative and synchronous time series values that can subsequently be used to estimate summary statistics of AMS and to infer correlations or nonlinear dependence between different data streams. Identification and modeling of statistical dependencies can be further exploited to develop predictive equations based on time series models.

Experimental investigation of the generator mode for a brushless dc motor at an increased rotational speed

This article deals with a commercially available direct drive brushless DC motor that was investigated in the generator mode at an increased speed above the rated one. During the conducted experiments the increase of the generator rotational speed was carried out due to a three-phase asynchronous motor with 5.5 kW rated power and 2920 rpm rated speed, which was further increased by a two-stage belt gearbox with a reduction ratio from 0.16 to 1.6. However, with an increase in the rotational speed, the magnetic losses also increase, which in turn increase the required value of the input mechanical power and lead to thermal overload of the brushless DC machine. An increase the generator rotational speed leads to an increase of the EMF value and, at the same value, of the stator current, leads to an increase the generated power. Throughout the experiment, the voltage was rectified using a diode bridge and bulk capacitor, after that it was connected to a load resistance. The presented calculations of the magnetic power losses for different electrical steel grades clearly demonstrate the nonlinear dependence between the magnetic field frequency and its magnitude. Experimental studies were carried out at different speeds of rotation of a brushless DC machine in a very wide range from 140 rpm to 5228 rpm, moreover, the values of the output power were obtained depending on the rotational speed. It is concluded, that in the generator mode of the brushless DC machine, it is necessary to take into account the feature of the operation at wind power plants, autonomous power supply such as hybrid power plants. In the first case, it is worth limiting the rotational speed from the driven mechanism, and in the second case, this mode of operation may be necessary for partial boosting of output power for short-term use.

Evolution of Temperature Field around Underground Power Cable for Static and Cyclic Heating

Power transmission covering long-distances has shifted from overhead high voltage cables to underground power cable systems due to numerous failures under severe weather conditions and electromagnetic pollution. The underground power cable systems are limited by the melting point of the insulator around the conductor, which depends on the surrounding soils’ heat transfer capacity or the thermal conductivity. In the past, numerical and theoretical studies have been conducted based on the mechanistic heat and mass transfer model. However, limited experimental evidence has been provided. Therefore, in this study, we performed a series of experiments for static and cyclic thermal loads with a cylindrical heater embedded in the sand. The results suggest thermal charging of the surrounding dry sand and natural convection within the wet sand. A comparison of heat transfer for dry, unsaturated and fully saturated sand is presented with graphs and colour maps which provide valuable information and insight of heat and mass transfer around an underground power cable. Furthermore, the measurements of thermal conductivity against density, moisture and temperature are presented showing positive nonlinear dependence.