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Performance improvement of manipulator actuated by pneumatic artificial muscles based on synergetic control and social spider optimisation algorithm
Full text linkThe manipulator actuated by pneumatic artificial muscles (PAM) is a widely used type of robotic arm in industrial automation. However, its performance can be limited by non-linear dynamics and uncertainties in the system. To overcome these limitations, this paper proposes a synergetic control strategy (SACT) to improve the performance of the SACT, a social spider optimisation algorithm (SSO) has been suggested for adjusting its parameters. To verify the performance of a PAM-actuated manipulator based on an optimal SACT controller, a computer simulation study was conducted using MATLAB software. Moreover, a comparison study between the optimal synergetic algorithm control theory and the optimal sliding mode controller (SMC) has been made in terms of robustness and transient behaviour characteristics. The provided simulation results have shown that the SACT controller exhibited quicker convergence towards the desired trajectory and maintained a lower steadystate error as compared to the SMC controller. Additionally, the SACT controller demonstrated more resilience to variations in parameters and showed more robust characteristics
Correlation between X-ray and gamma data of Swift measurements
Full text linkSeveral studies over the last two decades have used canonical correlation analysis (CCA) to study the relationships between main γ-ray (e.g. fluence, peak flux, and duration) and main X-ray (flux, decay and spectral index, and hydrogen column density) data from gamma-ray bursts (GRBs). In this paper, we revisit this approach using a much larger dataset to identify potential new insights into these relationships. We used CCA to investigate the interrelationship of the aforementioned gamma-ray and X-ray parameters. Using the derived canonical variables, we calculated their correlations (canonical loadings) with the original data. Consistently with previous research, the analysis revealed that gamma-ray fluence and X-ray flux have the strongest correlation, while the X-ray decay index and spectral index have a lower contribution. Interestingly, our analysis of a much larger dataset reveals that the HI column density makes a significant contribution to the overall correlation. This finding, in the context of the collapsar model for long GRBs, could be interpreted as an indication that the progenitor star ejected an HI envelope during the GRB
A study of X-ray point sources in Heiles Clouds 1 and 2
Full text linkStar formation takes place in the coldest parts of molecular clouds, beginning in the densest, collapsing regions of filaments. As pre-main sequence stars are luminous X-ray emitters, X-ray point sources can serve as effective tracers of YSOs. In our study, we examined the distribution of X-ray point sources in two nearby molecular clouds: Heiles Cloud 2 (HCL 2), a ring-like molecular cloud complex in the Taurus region, and Heiles Cloud 1 (LDN 1251), a cometary-shaped dark molecular cloud. By incorporating the latest YSO catalogue from Gaia DR3, we analysed how YSO positions compare to the structure of the interstellar medium (ISM) and found that the sources are primarily aligned just outside the densest regions. Additionally, we compared the positions with the magnetic field structure and found no clear correlation at the given resolution
Modification of properties of fresh mixture for 3D printing using cement-based mortar
Full text linkPortland cement is traditional binding material which is applicable for various modern technologies in these days – the 3D printing is one of them. The development of 3D printers using cement-based materials for the manufacturing of structural elements and moreover entire building is novel concept of structural engineering, which combines advanced material solution and high level ofautomation. This paper is focused on the study of properties of fresh mixture in order to control its consistency and regime of setting time to achieve continual process of 3D printing. The properties of fresh mortar were modified by the admixture accelerating the process of hardening and stabilizing agent. The performed experimental program showed that both applied admixtures could be used for the control of the consistency of fresh mortar to achieve optimal shape of mortar layer after its extrusion
Design of bond strength testing method of concrete layers for creating a material model
Full text linkThe need to determine the bond strength of concrete layers in structural modeling is quite frequent and often encounters a lack of relevant experimental data due to the large number of variables which affect the bond strength. This article describes an experimental method that makes it possible to obtain the experimental data necessary for subsequent modeling of multi-layered concrete composite structures. The experiment is designed to be applicable both to laboratory specimens with defined properties and to samples taken from existing structures. The advantage of this method is its simplicity, minimal equipment requirements, and repeatability. The three-layer specimens, representing a sandwich wall, allow the study of the influence of the age and quality of the concrete on the bond strength, and through image analysis, provide valuable information on deformation, interlayer slip, and crack formation. The results of the experiment may contribute to the determination of a bond strength diagram for multi-layered walls, which can be integrated into software tools for comprehensive structural analyses
Numerical studies of plasma emission in a mega joule plasma focus using Lee code
Full text linkIn this paper, plasma emissions (radiative recombination, bremsstrahlung, and line radiation) from a mega-joule plasma focus (PF1000) device is studied using the Lee code for nitrogen (N2), oxygen (O2) and argon (Ar) gases with pressure variation in the range of (0.05–2.5) Torr. Ion density, plasma velocity, pinch temperature, Joule heating, peak current, and minimum pinch radius are also obtained with pressure change for each of the gases. It is found that the line radiation is predominant compared to bremsstrahlung radiation and radiative recombination for each gas. At the optimum pressure, the maximum line radiations are found as: 3.9 kJ (91 % of total emissions) at 0.945 Torr N2, 6.2 kJ (85 % of total emissions) at 0.6 Torr O2 and 30 kJ (97 % of total emissions) at 0.23 Torr Ar, respectively. The minimum pinch radius (rmin) and consequent ion densitiy (Ni) of these gases are computed at their corresponding optimum pressures. It is found that the rmin (0.13 cm) of Ar is 10-fold smaller than N2 (1.25 cm) while it is 6-fold smaller in O2 (0.82 cm). This smallest minimum pinch radius of Ar produces the dominating ion density (71 × 1023 m−3) compared to N2 (3 × 1023 m−3) and O2 (5 × 1023 m−3) gases resulting the highest line radiation is found for Ar. The sharp dropping of the pinch radius of Ar plasma followed by the greatest plasma emission (line) shows the strong evidence of radiatively-enhanced compressions
Peculiarities of spectroscopy of thermal plasma with copper and molybdenum vapour admixtures
Full text linkThis study presents an investigation of arc discharge plasma generated between asymmetric pair of single-component copper and molybdenum electrodes. Optical emission spectra were registered in absolute intensity units with spatial resolution from the midsection of the arc column. Simultaneously laser absorption spectroscopy was carried out as well in order to determine radial distribution of optical thickness at the center of Cu I 510.5 nm spectral line. Particular attention was paid to assessing the influence of self-absorption effects, which can significantly distort the intensity of strong spectral transitions and lead to an underestimation of the spectral line intensity and, consequently, to a significant error in determining the temperature and number densities of metal atoms
Modelling the heating and erosion of a non-refractory cathode in a plasma torch
Full text linkIn this work, we study the heating of a hollow cylindrical copper electrode subjected to a rotating arc root modeled by a moving heat flux profile. The problem is solved analytically using a two time scale analysis. In accordance with previous literature works, it is shown that, whenever using reasonable values for the heat flux below the arc root, the fusion temperature of the material is not reached. We explain the experimentally evidenced erosion by the existence within the arc root, at smaller length scales, of cathode microspots. The cathode spot model presented in this paper gives orders of magnitude for the erosion rate in agreement with experiments
A novel approach to feature extraction from gear condition monitoring signals
Full text linkExtracting features from condition monitoring signals of rotating machines is challenging, primarily due to the many potential sources of noise and interference that can corrupt the signals. Additionally, these signals can vary significantly depending on the operating conditions of the machine, making it difficult to develop consistent diagnostic methods. However, an effective feature extraction remains crucial for proper maintenance scheduling and for preventing unexpected machine breakdowns, which can result in costly repairs and operational disruptions. Gear faults, if left unchecked, can be extremely dangerous, particularly in critical applications such as wind turbines, where a failure can lead to significant operational losses. Vibration signals from machinery are often complex, consisting of many different components, making it challenging to isolate the fault-related features from the noise. In this paper, an Envelope-Derivative Operator (EDO) is proposed to overcome these challenges by achieving a balance between the signal amplitude and frequency. The EDO measures the rate of change of the envelope, which is useful in detecting shifts in both the amplitude and the frequency of the signal. To identify the impulsive-like behaviour often associated with gear faults, the EDO analyses the energy content of the signal in both the time and frequency domains. By isolating the fault-related components and filtering out irrelevant noise, the proposed operator shows high efficiency in diagnosing gear faults under various experimental conditions, with no data fitting required and minimal computational resources. In addition, the non-destructive nature of this method can significantly reduce downtime and associated maintenance costs, making it an ideal tool for real-time fault detection in rotating machinery
Statistical analysis of accident data on D1 motorway
Full text linkThis study analyses incidents on the D1 motorway over the period 2015–2023, with a focus on improving towing operations processes. The analysis includes a breakdown of incidents by type (accidents, technical failures), injuries and deaths, and considers seasonal variations and traffic conditions. The data show that traffic accidents account for most incidents, especially in sections with heavy traffic and difficult weather conditions. At the same time, there is an increase in the number of incidents in 2018 and 2019, while 2020 brings a temporary decrease due to the COVID-19 pandemic. This research is part of a long-term project aimed at optimizing and standardizing the processes of extrication and towing activities, with the aim of streamlining interventions, minimizing traffic complications and ensuring rapid traffic recovery on key roads. Subsequent steps will focus on designing new standards for towing interventions and improving current protocols