Robotic Systems and Applications
Not a member yet
20223 research outputs found
Sort by
Correlation between ST-elevation myocardial infarction, non-ST-elevation myocardial infarction and the local Earth’s magnetic field changes
Get PDFStronger oscillations in the local Earth magnetic field may have an impact on the course of ischemic heart disease. This effect is individual for every person and depends on the sex, age, living territory, season, capability to adjust to magnetic field fluctuations and health status. Individuals who already have cardiovascular disease are more sensitive to magnetic field fluctuations, therefore further research is needed to make conclusions. Aim: To identify correlations between changes in local Earth magnetic field frequencies and patients with ST segment elevation myocardial infarction (STEMI) and non-ST segment elevation myocardial infarction (NSTEMI) cases per week, cases by sex per week and patients’ blood laboratory parameters (low-density lipoprotein cholesterol and Troponin I level). Methods: A retrospective study of 1667 patients, who were admitted to the Hospital of Lithuanian University of Health Sciences Kaunas Clinics between 1st January and 31st December 2019 due to acute coronary syndrome (STEMI and NSTEMI), were included in the study. Local Earth's time varying magnetic field (TVMF) was measured by a magnetometer located in Baisogala, Lithuania. Data from the magnetometer was collected daily, and weekly averaged. We assessed the correlations between average weekly geomagnetic field strength in six different frequency ranges (Hz) and average number of STEMI and NSTEMI cases per week, cases by sex per week and patients’ blood laboratory parameters (low-density lipoprotein cholesterol and Troponin I level). Results: The presence of a stronger magnetic field in the frequency range of 32-65 Hz was significantly related to the number of cases in the STEMI group during the winter season (r= 0.583, p= 0.036). Tendency towards a positive correlation was found during the winter in the men's group with STEMI in the high frequency range of 32-65 Hz. Low-density lipoprotein cholesterol level correlated positively in the winter STEMI group with the magnetic field in the 32-65 Hz range, and in the autumn STEMI group with the magnetic field in the frequency range of 0-7 Hz. Conclusion: Increased geomagnetic field strength in the high frequency range of 32-65 Hz is associated with a higher number of cases in the STEMI group
The discriminant statistic based on MPE-MWPE relationship and non-uniform embedding
Get PDFThe slope fitting line between MPE (multi-scale permutation entropy) and MWPE (multi-scale weighted permutation entropy) is recently proposed as a discriminant statistic for testing the nonlinearity of a time series. The main objective of this paper is to demonstrate that the selection of the optimal parameters of the non-uniform embedding is essential for the proposed discriminant statistic. In particular, the presented case studies indicate that the modified discriminant statistic based on non-uniform embedding can detect differences between such time series which remain indistinguishable if the original approach is used
Analysis of electromagnetic vibration and noise of permanent magnet synchronous motor based on field-circuit coupling
Get PDFIn order to study the influence of harmonics on the vibration and noise of permanent magnet synchronous motor, this paper introduces an analysis method based on field-circuit coupling, and establishes a complete analysis process from the control strategy to the vibration and noise response of the motor. Firstly, the coupling model including control strategy, main circuit model and electromagnetic field model is established. Secondly, the finite element model of the permanent magnet synchronous motor under the influence of coupling is established to analyze and compare the electromagnetic force wave characteristics of the coupling excitation and the sinusoidal excitation. Then, the coupled electromagnetic force is loaded into the structural field to simulate and calculate the vibration and noise. Finally, the effectiveness of the model is verified through experimental sound pressure level comparison under steady-state and speed-up conditions, and it provides a reference for vibration and noise prediction of the motor system
Study on the extraction method of the friction-induced vibration signal of rotary compressors
Get PDFThe operation noise level of air conditioners has been a main concern to consumers. The friction-induced vibration and noise have a contribution to the overall operation noise level of air conditioners. In this paper, two rotary compressors were tested to measure the vibration and noise of the compressors. The friction-induced vibration signals were extracted using a combination of the harmonic wavelet transform and the envelope spectrum analysis. The two rotary compressors were disassembled to check whether the compressor parts have been worn after testing. Results show that when the crankshaft was worn, the friction-induced vibration of compressors is strong. At low rotational speeds of the rotary compressor, the friction-induced vibration is easily excited, which is probably attributed to the boundary lubrication at the interface between the crankshaft and bearing. At high rotational speeds of the rotary compressor, the friction-induced vibration is not easy to be excited, which is probably attributed to the aerodynamic lubrication at the interface between the crankshaft and bearing
Study on vibration characteristics of ship mining system under composite load
Get PDFThe load that borne by ship mining system is very complex. The vibration of lifting pipe can be significantly affected by ocean current and wind load, which has a key impact on material lifting, ore bin storage and ship towing. Considering the composite load condition, the vibration control equation of mining ship is established based on the transverse swing mechanism of ship hull, and the variation law of transverse disturbance is obtained. The dynamic equation is constructed according to the bearing characteristics of the lifting system and the D’Alembert principle. The Wilson method is used to analyze and obtain the transverse vibration spectrum response of the lifting pipe under different wind loads, hull disturbance velocity and water depth. Based on the analogy method and hammering method, the vibration feedback test-bed of the lifting system is built, and the time-domain and frequency-domain vibration characteristics of the lifting pipe model under different water depths are obtained. The results show that in shallow water, the disturbance of mining ship and the composite load of ocean current are the key factors affecting the vibration amplitude of lifting pipe respectively. With the increase of water depth, the characteristic frequency and amplitude of the system decrease, and the amplitude gradually presents a discontinuous phenomenon
Recycling technology of old cement concrete pavement in highways
Get PDFThrough the practice of a highway pavement overhaul project, the feasibility of the old concrete pavement recycling scheme in terms of technology, economy and sustainable development is analyzed. The dynamic characteristics of concrete pavement were tested. The results show that crushing the old concrete panels into recycled aggregates and then re-use them not only eliminates the negative impact on the ecological environment caused by the land occupation of waste aggregates and needs to be disposed of, but also promotes the recycling of engineering waste and reduces the project cost. The pavement paved with recycled cement concrete can basically achieve the same dynamic performance as the pavement paved with conventional concrete
Skull base flexion and its influence on chewing
Get PDFSkull base asymmetries can occur in the intrauterine period, manifesting from birth as craniofacial asymmetries and should be investigated both in the maxilla and mandible and in the craniofacial region, as they are related to the base of the skull. The objective of this study was to explain that treatment using Craniofacial Biodynamics (CFBD) enables symmetrical craniofacial growth, being recommended from three to six years of age, when the processes of skull base remodeling cease. This study was based on exploratory bibliographic research, aiming at a better understanding of the concepts presented in this therapeutic approach, to verify the influence that such concepts exert on treatment through CFBD. It was evidenced in this research that these asymmetries may be corrected, or even minimized through the CFBD, which relates the ontogenetic development of the skull base with orofacial development
Simulation and experimental analysis of tip response of tapping mode atomic force microscope
Get PDFIn this study, the vertical deflection responses of tapping mode atomic force microscope (TM-AFM) micro-cantilever tip are obtained by simulation and experiment. The results show that, under the blocking of the sample on one side, the steady-state response of the tip is still a sinusoidal form almost symmetrical about the equilibrium position. Furthermore, from the perspective of energy dissipation of the micro-cantilever system, the phases of two surfaces with different properties are simulated under different background dissipation. The result shows that eliminating partial background dissipation can increase the phase contrast between the two surfaces. These results are of significance for understanding the tip response and phase optimization in TM-AFM
Helicopter rotor blade vibration reduction with optimizing the structural distribution of composite layers
Get PDFIn helicopter rotorcraft design, two main approaches as passive and active control methods widely used to decline vibration. In this study passive control methods are used to reduce vibration in the helicopter rotor blade. The most common passive control devices are dynamic vibration dampers, isolators and structural distribution of the composite blades. A surrogate optimization formula is used as the objective function of vibration reduction which includes vibratory hub loads and bending moments. In optimization model, composite ply angles are design variables and spar frequency-placement, autorotation and stress conditions are constraints. As the optimization method, a hybrid solution is chosen. The gradient-based algorithms generate accurate results in trust region and heuristic methods scan very large area of solution space. Due to the aforementioned advantages, these algorithms are hybridized. As a result of the comparison of the optimization outcomes with the baseline UH-60 rotor blades, approximately 38 % vibration reduction is observed in the new design
Impact of outgassing and its corrective methods to improve the vacuum stability in the Coriolis Vibratory Gyroscope
Get PDFCoriolis Vibratory Gyroscope (CVG) is an inertial angular rate measurement sensor. CVG sensor comprises of metal coated hemispherical quartz vibrating structure as the rotation sensing element. It is forced to vibrate at one of its resonant modes by electrostatic excitation. Because of the limited flexibility of the quartz sensing element, the amplitude is limited to the submicron level. An ultra-high vacuum environment is required for the sensing element to sustain vibration for a long time. The criticality in the sensor development is to maintaining an ultra-high vacuum environment for the sensing element. Sensor suffers a problem of vacuum instability during the operation due to the outgassing from its components. This paper presents a novel approach in the identification of various outgassing sources that exist in the sensor, mitigation plan to minimize outgassing rate by selection of suitable raw material, suitable fabrication process of the components, and the surface characterization etc. The research work also presents the cost-effective experimental methodology to measure the outgassing rate from the sensor components to assess the CVG vacuum life, the requirement of the getter to maintain the ultra-high vacuum level throughout the CVG operation