This paper summarizes the activity of the chosen Polish geodetic research teams in 2015–2018 in the fields of Earth: rotation, dynamics as well as magnetic field. It has been prepared for the needs of the presentation on the 27th International Union of Geodesy and Geodynamics General Assembly, Montreal, Canada. The part concerning Earth rotation is mostly focused on the use of modelling of diurnal and subdiurnal components of Earth rotation by including low frequency components of polar motion and UT1 in the analysis, study of free oscillations in Earth rotation derived from both space-geodetic observations of polar motion and the time variation of the second degree gravitational field coefficients derived from Satellite Laser Ranging (SLR) and Gravity Recovery and Climate Experiment (GRACE) observations, new methods of monitoring of Earth rotation, as well as studies on applications of the Ring Laser Gyroscope (RLG) for direct and continuous measurements of changes in Earth rotation and investigations of the hydrological excitation of polar motion. Much attention was devoted to the GRACE-derived gravity for explaining the influence of surface mass redistributions on polar motion. Monitoring of the geodynamical phenomena is divided into study on local and regional dynamics using permanent observations, investigation on tidal phenomena, as well as research on hydrological processes and sea level variation parts. Finally, the recent research conducted by Polish scientists on the Earth’s magnetic field is described.
This paper deals with an issue of a rotational motion impact on a construction and presents civil engineering applications of a fiber optic rotational seismograph named Fiber-Optic System for Rotational Events & Phenomena Monitoring. It has been designed for a long- term building monitoring and structural rotations’ recording. It is based on the Sagnac effect which enables to detect one-axis rotational motion in a direct way and without any reference system. It enables to detect a rotation component in the wide range of a signal amplitude from 10-8 rad/s to 10 rad/s, as well as a frequency from DC to 1000 Hz. Data presented in this paper show the behavior of a reinforced concrete frame construction on different floors. Several measurements were carried out by placing the applied sensor on different floor levels of a building. The laboratory and in-situ measurements confirmed that Fiber-Optic System for Rotational Events & Phenomena Monitoring is an accurate and suitable device for applications in civil engineering.
The paper presents a method of measuring the angle of rotation and twist using a tilted fibre Bragg grating
(TFBG) periodic structure with a tilt angle of 6◦, written into a single-mode optical fibre. It has been shown
that the rotation of the sensor by 180◦ causes a change in the transmission coefficient from 0.5 to 0.84 at
a wavelength of 1541.2 nm. As a result of measurements it was determined that the highest sensitivity can
be obtained for angles from 30◦ to 70◦ in relation to the basic orientation. The change in the transmission
spectrum occurs for cladding modes that change their intensity with the change in the polarization of light
propagating through the grating. The same structure can also be used to measure the twist angle. The
possibility of obtaining a TFBG twist by 200◦ over a length of 10 mm has been proved. This makes it
possible to monitor both the angle of rotation and the twist of an optical fibre with the fabricated TFBG.
In the present article, we introduced a new model of the equations of general ized thermoelasticity for unbounded orthotropic body containing a cylindrical cavity. We applied this model in the context of generalized thermoelasticity with phase-lags under the effect of rotation. In this case, the thermal conductivity of the material is considered to be variable. In addition, the cylinder surface is traction free and subjected to a uniform unit step temperature. Using the Laplace transform technique, the distributions of the temperature, displacement, radial stress and hoop stress are determined. A detailed analysis of the effects of rotation, phase-lags and the variability thermal conductivity parameters on the studied fields is discussed. Numerical results for the studied fields are illustrated graphically in the presence and absence of rotation.
The model of the equations of generalized thermoelasticity in a semi-conducting medium with two-temperature is established. The entire elastic medium is rotated with a uniform angular velocity. The formulation is applied under Lord-Schulman theory with one relaxation time. The normal mode analysis is used to obtain the expressions for the considered variables. Also some particular cases are discussed in the context of the problem. Numerical results for the considered variables are obtained and illustrated graphically. Comparisons are also made with the results predicted in the absence and presence of rotation as well as two-temperature parameter.
A proper description of ground motions generated by seismic and paraseismic events requires gathering data of six components of seismic waves. T hree of them, the so called translational waves, are well researched and identified. Unfortunately, until recently, the remaining three components named as rotational waves were generally estimated with the use of indirect methods based on theoretical calculations. T his was related mostly with the lack of proper instruments for the recording of rotational seismic waves. T hus, rotational waves were not fully recognized thus far. Recently, several types of advanced instruments for direct measurements of rotation were invented. Based on the measurements of strong ground motions it was indicated that the amplitude of the rotational components in close distances from the seismic source can be significantly larger than expected. Apart from this, there is still a lack of analyses considering the characteristic of rotational seismic waves generated by induced seismic events. In this paper, the results of preliminary measurements of rotational motions generated by induced seismic waves were presented. Ground movements related with mining tremors were analyzed in terms of amplitude, frequency and duration.
The contradiction between the restriction of grating manufacturing technology and high-resolution measurement requirements has been the focus of attention. The precision requirement of angle calculation during the digital subdivision processing of a Moiré signal is focused on, the causes of errors in the solution of arcsine function are analysed, and an improved coordinate rotation digital computer (CORDIC)with double-rotation iteration is proposed by discussing the principle of the conventional CORDIC in detail herein. Because the iterative number and data width of the improved CORDIC are limited by the finite digital circuit resources and thus determine the calculation accuracy directly, subsequently the overall quantization error (OQE) of the improved CORDIC is analysed. The approximate error and rounding error of the algorithm are deduced, and the error models of iterative number and data width are established. The validity and application value of the improved CORDIC are proved through simulations and experiments involving a subdividing circuit. The corresponding relation between the approximate error, rounding error and iteration number, as well as the bit width are proved by quantization. The error of subdivision with the improved CORDIC, obtained through a calibration experiment, is within ±0.5′′ and the mean variance is 0.2′′. The results of the research can be applied directly to a digital subdivision system to guide the parameter setting in the iterative process, which is of crucial importance in the quantitative analysis of error separation and error synthesis.
The aim of performed research was to evaluate weed seedbank in soil under the influence of four different winter wheat tillage systems. Winter wheat was grown in the following cultivation systems: A – monoculture with direct drilling into white clover mulch; B – monoculture with direct drilling into wheat stubble; C – monoculture with conventional tillage; D – crop rotation with conventional tillage. It was shown that pre-sowing wheat tillage had a more considerable effect on weed species and weed seedbank in soil than type of crop rotation. The least seedbank was observed when plough system was replaced by direct drilling. In the soil layer of 0–20 cm, under wheat no-plough tillage, 20.3% less weed diaspores wasfound compared to monoculture with plough tillage and by 40.1% lessthan in crop rotation. The plough tillage increased amount of weed diaspores in the whole plough layer, while direct drilling increased it only in 0–1 cm of soil layer. After direct drilling of wheat into stubble (B) the number of weed diaspores in 1 dcm3 of soil in 0–1 cm layer was over twofold higher than in direct sowing in mulch (A), and threefold higher than in crop rotation (D) and almost six times higher than in wheat monoculture with conventional tillage (C). Dominating weed species in the soil over the types of wheat cultivation systems were: Chenopodium album L., Amaranthus retroflexus L., Apera spica-venti L., Lamium purpureum L., and Viola arvensis Murr.
In this paper, the problem of concentric pervious spheres carrying a fluid sink at their centre and rotating slowly with different uniform angular velocities Ω1. Ω2 about a diameter has been studied. The analysis reveals that only azimuthal component of velocity exists and the torque, rate of dissipated energy is found analytically in the present situation. The expression of torque on inner sphere rotating slowly with uniform angular velocity Ω1, while outer sphere also rotates slowly with uniform angular velocity Ω2, is evaluated. The special cases like, (i) inner sphere is fixed (i.e. Ω1 = 0), while outer sphere rotates with uniform angular velocity Ω2, (ii) outer sphere is fixed (i.e. Ω2 = 0), while inner sphere rotates with uniform angular velocity Ω1, (iii.) inner sphere rotates with uniform angular velocity Ω1, while outer rotates at infinity with angular velocity Ω2; have been deduced. The corresponding variation of torque with respect to sink parameter has been shown via figures. AMS subject classification – 76 D07.
Analytical and numerical nonlinear solutions for rotating variable-thickness functionally graded solid and annular disks with viscoelastic orthotropic material properties are presented by using the method of successive approximations. Variable material properties such as Young’s moduli, density and thickness of the disk, are first introduced to obtain the governing equation. As a second step, the method of successive approximations is proposed to get the nonlinear solution of the problem. In the third step, the method of effective moduli is deduced to reduce the problem to the corresponding one of a homogeneous but anisotropic material. The results of viscoelastic stresses and radial displacement are obtained for annular and solid disks of different profiles and graphically illustrated. The calculated results are compared and the effects due to many parameters are discussed.
In automatic and accurate reading recognition of analog meters based on machine vision, one of important issues is the detection of pointer features, which includes the meter center and pointer image processing. The current automatic-recognition approaches to reading analog meters often consist in locating the meter center based on the dial region or its border. The located center is not coincident with the rotation center of pointer which leads to inevitable reading errors. In the paper, the centripetalism of annular scale lines is used to calculate the position of the pointer rotation center. First, it uses the region growing method to locate the dial region and uses the eccentricity measure to extract annular scale lines. Second, the parameters of these scale lines are estimated with the Hough transform method. Then, the common intersection of a group of lines, i.e., the meter rotation center, is determined with the maximum probability criterion. Finally, the pointer centerline and direction are detected through the calculated center and the Hough transform results. The simulated and experimental results demonstrate that the proposed method can accurately locate the pointer rotation center and obtain pointer centerline. Moreover, it is applicable to the meter image captured under a slant camera view or with uneven light illumination.
Based on the rolling bearing vibration measurement principle in ISO standard, a nonlinear dynamic model of ball bearing is built and motion equations of the inner ring, outer ring, and rolling elements are derived by using Lagrange’s equation. The ball bearing model includes the influence of waviness, rotational speed, external load, arbor supporting stiffness and arbor eccentricity. Ball bearing high-speed vibration tests are performed and used to verify the theoretical results. Simulated results showed that specific waviness orders produced the principal frequencies that were proportional to rotational speed. Rotational speed mainly affected the value of the natural frequency of the bearing system, and RMS (Root Mean Square) of the full band had a great fluctuation with the increase of rotational speed. In the experiment, spectrum and RMS of 2fs-30 kHz (fs: the rotational frequency of inner ring/arbor) under high speed could include not only the influence of rotational speed but also principal frequencies produced by waviness, which could cover the part of requirements of the standard bearing vibration measurement.