Rotational Components Research Articles

Two-dimensional kinematics and dynamical modelling of the ‘Jackpot’ gravitational lens from deep MUSE observations

ABSTRACT We present results from the first spatially resolved kinematic and dynamical modelling analysis of the unique SDSSJ0946+1006 (‘Jackpot’) triple-source lens system, where a single massive foreground $z\, =\, 0.222$ galaxy multiple-images three background sources at different redshifts. Deep integral field unit spectroscopic data were obtained using the MUSE instrument on the VLT, which, compared to previous single-slit observations, provides full azimuthal area coverage, high sensitivity (5 h integration) and high angular resolution (0.5 arcsec full width at half-maximum). To account for the strong continuum contributions from the $z\, =\, 0.609$ source, a multiple-component stellar template fitting technique is adopted to fit to the spectra of both the lens galaxy and the bright lensed background arc simultaneously. Through this, we robustly measure the first and second moments of the 2D stellar kinematics out to about 10 kpc from the centre of the lens, as well as resolving the inner profile inwards to ∼1 kpc. The 2D kinematic maps show a steep velocity dispersion gradient and a clear rotational component. We constrain the characteristic properties of the stellar and dark matter (DM) mass components with a sufficiently flexible parametrised dynamical model and an imposed lensing mass and find a DM density slope of $\gamma \, =\, 1.73\substack{+0.17 \\ -0.26}$, i.e. significantly steeper than an unmodified NFW profile ($\gamma \, =\, 1$) and consistent with a contracted DM halo. Our fitted models have a lensing-equivalent density slope of $\eta \, =\, 0.96\pm 0.02$, and thus we confirm most pure lensing results in finding a near isothermal profile for this galaxy.

[Translated article] Study of femoral component malrotation as a cause of pain after total knee arthroplasty

IntroductionThe total knee arthroplasty (TKA) has been shown to be a successful and cost-benefit procedure in terms of pain improvement in patient with symptomatic knee osteoarthritis. However, almost a 20% of the patients are not satisfied with the result of the surgery. Material and methodWe have carried out a transversal unicentric cases controls study with clinical cases of the own hospital, obtained by a clinical records revision. A total of 160 patients with a TKA with at least 1 year of follow-up were selected. Demographic variables, functional scales (WOMAC and VAS) and rotation of the femoral component through the analysis of the images obtained by CT scan were collected. ResultsThe total was 133 patients that was divided in two groups. A control group and pain group. The Control group was made up of 70 patients with a mean age of 69.59 years (23 men and 47 women) and the pain group was made up of 63 patients with a mean age of 69.48 years (13 men and 50 women). We didn’t find difference regarding the analysis of the rotation of the femoral component. In addition, we were not found significant differences when applying a stratification by sex. And, the analysis of the malrotation of the femoral component, previously defining limits of value rotation considered as extreme, in any of the case did not show significant differences. ConclusionThe results of the study confirm that malrotation of the femoral component had no influence on the presence of pain at a minimum of one year of follow-up after TKA implantation.

Discussion on “Seismic responses of near-fault building clusters including in-plane rotational component in investigated lump model of earth medium” by Wei Zhong, Tielin Liu, Yingchun Jiang, and Bo Qian [Soil Dyn Earthq Eng 167 (2023) 107796

Discussion on “Seismic responses of near-fault building clusters including in-plane rotational component in investigated lump model of earth medium” by Wei Zhong, Tielin Liu, Yingchun Jiang, and Bo Qian [Soil Dyn Earthq Eng 167 (2023) 107796

Reply to the discussion by Z.Zembaty on “seismic responses of near-fault building clusters including in-plane rotational component in investigated lump model of earth medium” [Soil Dyn Earthq Eng 167 (2023) 107796

Reply to the discussion by Z.Zembaty on “seismic responses of near-fault building clusters including in-plane rotational component in investigated lump model of earth medium” [Soil Dyn Earthq Eng 167 (2023) 107796

Frequency-chirprate synchrosqueezing-based scaling chirplet transform for wind turbine nonstationary fault feature time–frequency representation

As key rotational components of wind turbines, planetary gearboxes, and bearings need special health monitoring and fault diagnosis for reducing downtime and maintenance costs. However, it is still a challenging issue for time–frequency analysis (TFA) techniques to analyze nonstationary and close-spaced fault frequencies of wind turbines. Hence, a high- concentration TFA technique, termed frequency-chirprate synchrosqueezing-based scaling chirplet transform (FCSSCT) is developed. In the FCSSCT, the novel dimension of chirprate is introduced to map the signal into the three-dimensional space of time–frequency-chirprate in contrast to the time–frequency domain in the synchrosqueezing transform (SST), herein, the three-dimensional space of time, frequency and chirprate is calculated based on the scaling-basis chirplet transform (SBCT); then, a frequency-chirprate synchrosqueezing operator (FCSO) is defined in the frequency-chirprate domain to reassign the amplitude coefficients of the SBCT results and a three-dimensional representation of time–frequency-chirprate is obtained; finally, the time–frequency representation (TFR) with concentrated energy is obtained by transforming the three-dimensional representation of the time–frequency-chirprate space into the time–frequency domain. The effectiveness of the developed FCSSCT is verified by the simulated multi-component signals with close-spaced frequencies or crossover frequencies. Experimental analysis results on wind turbine planetary gearbox and bearing show that the developed technique is effective in characterizing nonstationary fault frequencies. Rényi entropies demonstrate that the FCSSCT has much better energy concentration compared with several advanced TFA methods.

Self-interstitial atom properties in Nb–Mo–Ta–W alloys

Self-interstitial atoms (SIA) are generated in collision cascades during high-energy particle irradiation of crystalline materials. In pure metals, SIA generally adopt split configurations and display fast mobilities along one-dimensional trajectories. This differentiates them from vacancies, which move in confined three-dimensional paths. This asymmetry is one of the pillars of irradiation damage theories that have been successful in explaining a number features of the irradiation response of pure metals and dilute alloys. However, in complex concentrated alloys consisting of several metallic elements in equal or near equal proportions, lattice distortions associated with compositional fluctuations change the potential energy landscape on atomic scales, leading to SIA structures not seen in their pure metal counterparts. In this paper, we use atomistic simulations to study the properties of self-interstitial atoms in the quaternary equiatomic Nb–Mo–Ta–W refractory alloy. Chemically, these SIA defects adopt a variety of structures involving all pairs of atoms. We find the 〈111〉 orientation to be the most common among all split configurations, but we also observe – surprisingly – a relatively high occurrence of octahedral SIA. In terms of their diffusivities, we find two clearly distinguished regimes below and above 600 K, where the SIA diffusion changes dimensionality from 1D to 3D. We calculate the migration energies and diffusion pre-factors in both regions, from which we extract the translational and rotational components of the defect migration. We find values of 0.25 eV and pre-factors of ∼10−11 m2 s−1 in the low temperature regime, and 0.57 eV and ∼10−8 m2 s−1 in the high temperature one. From this, we estimate a rotational energy barrier of 0.37 eV.

Comparison of Obliques Muscles Strength Between Left and Right Side in Normal Young Adults Using Handheld Dynamometer - A Pilot Study

Background: Asymmetry of abdominal muscles is a potential cause for lowback pain. Most studies assume therotational strength towards non dominant side to be more but no studies have been conducted to objectivelymeasure the asymmetry. In subjects with spinal deformity like scoliosis which has a rotational component to it,it can be presumed that there could be asymmetry between the oblique force couplehowever this study aims tofind out whether this asymmetry exists in normal healthy individuals. By using manual muscle testing for assessingoblique muscle strength only gross asymmetry can be detected. Therefore there is a need for more objectivemeasure to detect subtle discrepancies within strength of both sides.Objective: The objective of this study is to measure the strength of external and internal oblique on both sideusing handheld dynamometer and to compare the strength on both sides.Methodology:30 healthy young individuals in the age group of 18-30 years were selected to participate in thestudy. All subjects were right hand dominant.External oblique and internal oblique muscle strength was measuredin KGs using a Jamar type of hydraulichand held dynamometer.Results: There was a significant difference between the strength of external obliques on right and left side withstrength on right side being more whereas there was no significant difference between strength of internaloblique between right and left side.

Factor analysis for construct validity of a trunk impairment scale in Parkinson's disease: a cross-sectional study.

To investigate the construct validity of the Trunk Impairment Scale (TIS), which was developed to assess trunk impairment in patients with stroke, in patients with Parkinson's disease (PD). This retrospective, cross-sectional study enrolled consecutive PD inpatients. Correlation analysis was performed to clarify whether the TIS assessment was related to other balance functions, lower extremity muscle strength, or walking ability. Factor analysis was performed to see how the background factors of TIS differ from balance function, lower limb muscle strength, and walking ability. Examining the data of 471 patients with PD, there were relationships between TIS and the Mini-Balance Evaluation Systems Test (r = 0.67), Barthel Index (r = 0.57), general lower limb extension torque (r = 0.51), two-minute walk test (r = 0.54), Hoehn and Yahr stage (r = -0.61), and Movement Disorder Society Unified Parkinson's Disease Rating Scale part III total points (r = -0.59). Factor analysis showed that TIS items were divided into three factors (an abdominal muscles and righting reflex component; a perception and verticality component; and a rotational component), differing from other scales that included clinical assessment items. The TIS can be useful for assessing the underlying trunk impairment as a basis for activities of daily living, gait function, and balance ability in patients with PD.

Relevance of the Foundation Input Motion in the assessment of the seismic response of pile-supported bridge piers

The seismic response of pile-supported bridge piers is commonly studied avoiding the assessment of the Foundation Input Motion (FIM) (i.e., the motion at the foundation level, which is different compared to that in the free-field, due to the filtering effect exerted by the piles) and assuming fixed-base conditions. A better approach is represented by the substructure method which consists of 3 steps: 1) the assessment of the FIM; 2) the computation of the impedance functions of the soil-foundation system, 3) the analysis of the superstructure response resting on a compliant-base at which is applied the FIM. In many cases this method is not used in a rigorous way (as the assessment of the FIM is not commonly considered an easy task by the structural engineers) and the seismic motion at the base of the model is assumed to be the same as in the free-field. Thus, the effect of Soil-Structure Interaction (SSI) is neglected. Nevertheless, this effect might be beneficial, as piles can filter out some high-frequency components of the free-field motion, especially in the case of large-diameter piles and soft soil conditions (i.e., in those cases in which piles are generally necessary). On the other hand, special attention should be given to those foundations composed by very small pile groups, since the FIM will consist of both a horizontal and a rotational component (which would play a detrimental role). Moreover, it should be remembered that considering SSI would lengthening the fundamental period of the system compared to that under fixed-base hypothesis. This aspect would lead to both positive and negative effects based on the seismic motion properties. This contribution will attempt to show the relevance of a proper assessment of the FIM while studying the seismic response of pile-supported bridge piers. To this end a specific software has been developed to properly compute the FIM considering the filtering effect exerted by the piles.

The translation and validation of the MES for an Austrian sample.

Empathy plays an important role in midwifery care, not only for the women but also for midwives. The Midwifery Empathy Scale (MES) was developed to assess the empathy levels of midwives and midwifery students. The purpose of this study was the translation and validation of the MES for an Austrian sample. A total of 277 midwives working in Austria completed the questionnaire of the MES. The psychometric measurements that were performed included explanatory factor analysis using a varimax rotation and principal components analysis. Moreover, the internal consistency of the MES was assessed with reliability coefficients. The Kaiser-Meyer-Olkin (KMO) measure of sampling adequacy and a Bartlett's test of sphericity were carried out. Principal components analysis showed seven orthogonal factors. KMO measure of sample adequacy = 0.724 and Bartlett's test of sphericity = 1058.904 (df=231, p<0.0001). The MES showed an acceptable overall internal consistency: Cronbach's alpha was found to be 0.721 and the Guttman split-half coefficient was 0.611. The findings of our study confirm the multidimensionality of MES, demonstrating a seven-factor structure which contained subscales reflecting empathy and emotional connection. The mean total score of Austrian midwives' responses to the MES was 44.80 with scores ranging from 24 to 81. This study shows that the German version of the Midwifery Empathy Scale is a reliable instrument for evaluating the empathy levels of midwives and midwifery students in Austria. The German MES could be used in the selection and education of future midwives as well as in connection with empathy trainings of midwives.

Application of Principal Component Analysis in Establishing the Dominant Pollutants in the New Calabar River.

The New Calabar River, an essential water source in Nigeria’s Niger Delta region, is facing significant water quality issues due to human activities. This research adopts a comprehensive strategy, integrating field data gathering, statistical analyses, and modeling methods to evaluate and simulate the impact of these activities on water quality. Analysis of Variance (ANOVA) outcomes revealed notable seasonal fluctuations in certain water quality parameters like Water Temperature (F=116.009, p&lt;0.001) and pH levels (F=12.782, p&lt;0.001), indicating clear distinctions between the specified months. Conversely, Total Dissolved Solids (TDS) and Electrical Conductivity (EC) showed insignificant variations (F=0.050, p=0.95 and F=0.036, p=0.96, respectively). Principal Component Analysis (PCA) identified crucial factors influencing water quality variations. The rotated component matrix displayed substantial loadings for parameters such as Turbidity (0.932), Dissolved Oxygen (0.919), and Biological Oxygen Demand (0.912), suggesting their significant impact on water quality dynamics. Employing GIS techniques for spatial mapping of WQI values uncovered pollution hotspots near Points 5 and 6, aligning with the PCA findings. These regions exhibited “Very Bad” water quality status, indicating severe pollution levels. Conversely, Point 3 demonstrated a “Medium” water quality status, implying better water quality conditions. Overall, the study highlights the intricate connection between human activities and water quality in the New Calabar River. The insights gained offer valuable guidance for informed decision-making in water resource management, pollution mitigation strategies, and policy development. Future research endeavors should prioritize continuous monitoring, adaptive management approaches, and community involvement to foster sustainable water quality management practices in the area.

Misalignment between the propagation direction of the bora wind and its pulsations

AbstractThe bora is a well‐known downslope windstorm that blows at the eastern coast of the Adriatic Sea from inland towards the sea, mainly from the northeasterly direction. One of the notable bora characteristics is the quasi‐periodic gust pulsations. We address their characteristics during strong to severe bora events by applying rotational spectral analysis on 9 months of continuous high‐frequency sonic anemometer measurements in the town of Senj, Croatia. The analysis shows that the orientation of the pulsations' plane of oscillation does not correspond to the measured near‐ground wind direction. In particular, these two directions seem to be negatively correlated. Although the structure of the pulsations is mostly rectilinear, the positive rotational component was larger than the negative one in all except one bora event. The coincidence of the wind shear direction within the lee‐side jet with the orientation of the plane of oscillation leads to a tentative conclusion that its orientation was governed by the Kelvin–Helmholtz instability, at least in the cases presented.

Rotational energy as a measure of flow swirl intensity

The paper proposes a criterion for estimating the intensity of swirling flow using Mach number for the rotational component of velocity. The drop in the maximum value of the criterion in the case of jet propagation in a pipe and in the case of mixing in a confined swirling flow is analyzed. The approximating dependences of the decrease of the swirling intensity according to the experimental works of different authors have been obtained.

External Rotation Strength After TSA in Osteoarthritic Shoulders with Eccentric Deformity Is Not Impacted by Posterior Rotator Cuff Deficiency.

Patients with persistent glenohumeral osteoarthritis symptoms despite nonoperative management may pursue anatomic total shoulder arthroplasty (TSA). TSA revision rates are higher in patients with preoperative eccentric (asymmetric posterior erosion) compared with concentric (symmetric) glenoid deformity. If posterior rotator cuff deficiency demonstrated preoperatively in patients with eccentric deformity persists after TSA, it may manifest as relative weakness in external compared with internal rotation secondary to deficient activity of the shoulder external rotator muscles. Persistent posterior rotator cuff deficiency is hypothesized to contribute to TSA failures. However, it remains unknown whether rotational strength is impaired after TSA in patients with eccentric deformity. Our goal was to determine if patients with eccentric deformity exhibit relative external rotation weakness that may be explained by posterior rotator cuff deficiency after TSA. Patients who were >1 year after TSA for primary glenohumeral osteoarthritis and had had preoperative eccentric or concentric deformity were prospectively recruited. Torque was measured and electromyography was performed during maximal isometric contractions in 26 three-dimensional direction combinations. Relative strength in opposing directions (strength balance) and muscle activity of 6 shoulder rotators were compared between groups. The internal (+) and external (-) rotation component of strength balance did not differ in patients with eccentric (mean internal-external rotation component of strength balance: -7.6% ± 7.4%) compared with concentric deformity (-10.3% ± 6.8%) (mean difference: 2.7% [95% confidence interval (CI), -1.3% to 6.7%]; p = 0.59), suggesting no relative external rotation weakness. Infraspinatus activity was reduced in patients with eccentric (43.9% ± 10.4% of maximum voluntary contraction [MVC]) compared with concentric (51.3% ± 10.4% of MVC) deformity (mean difference: -7.4% [95% CI, -13.4% to -1.4%] of MVC; p = 0.04). A relative external rotation strength deficit following TSA was not found, despite evidence of reduced infraspinatus activity, in the eccentric-deformity group. Reduced infraspinatus activity suggests that posterior rotator cuff deficiencies may persist following TSA in patients with eccentric deformities. Longitudinal study is necessary to evaluate muscle imbalance as a contributor to higher TSA failure rates. Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Residents’ Attitude Towards Pilgrims: Development And Validation Of Sustainable Religious Tourism Scale

The research aims to develop a sustainable religious tourism (SRT) scale that can assess the attitude of the local residents towards the pilgrims. The development of the scale starts with the literature review wherein the identification of dimensions of sustainable tourism and generation of attributes have been accomplished. This is followed by refinement of the items through the content validation procedure where both domain and industry experts are consulted and made their recommendations. The refinement of items through the exploratory factor analysis (EFA) followed the content validation process with a rotated component matrix yielding 5 factors with a total of 30 items for the SRT scale. The psychometric properties of the SRT scale are then tested with the help of confirmatory factor analysis (CFA) which establishes both the reliability and validity of the SRT scale. The SRT scale thus developed by the study consists of a total of 30 items under the 5 different dimensions of SRT.

Precise Calibration of Femoral Component Rotation Using the Posterior Condylar Axis as a Reference during Image-free Robot-assisted Total Knee Arthroplasty: A Technical Note.

The use of image-free robotic systems for total knee arthroplasty (TKA) is gaining popularity. Although the surgical transepicondylar axis (sTEA) is considered the optimal femoral rotational reference during TKA, it is difficult to define intra-operatively. Conventional and image-free robot-assisted TKA (RA-TKA) therefore rely on the use of Whiteside's axis (WSA) or the posterior condylar axis (PCA) as surrogate references. The PCA is considered to be associated with less variability than the WSA. The authors present a simple technique to permit calibration of femoral component rotation (FCR) using the PCA as a reference for image-free robotic systems that do not permit this option. The image-free robotic systems used by the authors (Navio and CORI, Smith and Nephew, Memphis, TN, USA) permit calibration of FCR only when the perpendicular to WSA is used as a reference. When the PCA is selected as a reference, a fixed 3° of external rotation is set by the robot. The technique proposed by the authors involves the use of the former setting, followed by internal rotation of the perpendicular to the WSA to co-align it with the PCA. The planning menu subsequently permits virtual surgical planning using the PCA as the femoral rotational reference and permits adjustments in rotational positioning of the femoral component while displaying the effect of rotation on bony resection and vice versa in real time. In addition, coaligning the perpendicular to the anatomic trans-epicondylar axis (aTEA) displays the internal rotation of the PCA with respect to the aTEA. This information can be used for setting rotational boundaries with respect to the PCA while using various alternate alignment strategies, like functional alignment, since the relation between the aTEA and sTEA is less likely to be affected by dyplasia and wear when compared with the PCA or WSA. This simple technique permits optimally calibrated rotational positioning of the femoral component during image-free RA-TKA, using the PCA as a reference. It can be applied for optimizing surgery in knees with altered or outlier anatomy, as well as routinely, especially when alternate alignment strategies are used.

Utilizing Machine Learning to Examine the Spatiotemporal Changes in Africa’s Partial Atmospheric Layer Thickness

As a crucial aspect of the climate system, changes in Africa’s atmospheric layer thickness, i.e., the vertical distance spanning a specific layer of the Earth’s atmosphere, could impact its weather, air quality, and ecosystem. This study did not only examine the trends but also applied a deep autoencoder artificial neural network to detect years with significant anomalies in the thickness of Africa’s atmosphere over a given homogeneous region (derived with the rotated principal component analysis) and examine the fingerprint of global warming on the thickness changes. The broader implication of this study is to further categorize regions in Africa that have experienced significant changes in their climate system. The study reveals an upward trend in thickness between 1000 and 850 hPa across substantial parts of Africa since 1950. Notably, the spatial breadth of this rise peaks during the boreal summer. Correlation analysis, further supported by the deep autoencoder neural network, suggests the fingerprint of global warming signals on the increasing vertical extent of Africa’s atmosphere and is more pronounced (since the 2000s) in the south-central regions of Africa (specifically the Congo Basin). Additionally, the thickness over the Sahel and Sahara Desert sees no significant increase during the austral summer, resulting from the counteracting effect of the positive North Atlantic Oscillation, which prompts colder conditions over the northern parts of Africa. As the atmospheric layer thickness impacts the temperature and moisture distribution of the layer, our study contributes to its historical assessment for a sustainable ecosystem.

Intricate dynamics of rotational buoyancy, magnetic field, Hall current, and infrared radiation in a Casson fluid medium

AbstractRotational buoyancy assumes a substantial role in a multitude of natural and engineering systems, with particular emphasis on astrophysical and geophysical scenarios. The primary objective of this study is to delve into the intricate dynamics of a rotational flow subjected to forces from rotational buoyancy, magnetic field, Hall effects, and infrared radiation in a Casson fluid medium adjacent to a thermal plate. The LT technique is harnessed to yield the closed‐form solutions for the dimensionless governing flow system. Through graphical analyzes, the physical implications of key contextual parameters are elucidated. Our findings demonstrate that Hall currents and rotational buoyancy forces jointly act to restrict primary fluid motion while amplifying secondary motion. An upswing in the Casson parameter leads to a marked reduction in the magnitude of the velocity components. Furthermore, intensified infrared radiation results in a more flattened thermal distribution. The primary directional shear stress attenuates, while an inverse bias is observed for the shear stress along the secondary direction, particularly with higher values of the Hall and rotation parameters. The insights gained from this study have practical implications for the design and operation of various systems involving rotational components, such as rotary machinery, automotive systems, and industrial automation, and contribute to weather forecasting and climate modelling.

Clustering of Floating Tracers in a Random Velocity Field Modulated by an Ellipsoidal Vortex Flow

The influence of a background vortex flow on the clustering of floating tracers is addressed. The vortex flow considered is induced by an ellipsoidal vortex evolving in a deformation. The system exhibits various vortex motion regimes: (1) a steady state, (2) oscillation and (3) rotation of the ellipsoidal vortex core. The latter two induce an unsteady velocity field for the tracer, thus leading to irregular (chaotic) tracer motion. Superimposing a stochastic divergent velocity field onto the deterministic vortex flow allows us to observe significantly different tracer evolution. An ellipsoidal vortex has ellipsoidal symmetry, and the tracer’s trajectories exhibit the same symmetry inside the vortex. Outside the vortex, the external deformation flow symmetry dominates. Diffusion scattering and chaotic advection give tracers the opportunity to leave the region of ellipsoidal symmetry and form a picture of shear flow symmetry. We use the method of characteristics to integrate the floating tracer density evolution equation and the Euler Ito scheme for obtaining the floating tracer trajectories with a random velocity field. The cluster area and cluster mass from the statistical topography are used as the quantitative diagnostics of a floating tracer’s clustering. For the case of a steady ellipsoidal vortex embedded into the deformation flow with a random velocity field component, we found that the clustering characteristics were weakened by the steady vortex. For the cases of an unsteady ellipsoidal vortex, we observed clustering in the floating tracer density field if the contribution of the divergent component was greater than or equal to that of the rotational (nondivergent) component. Even when the initial floating tracer patch was set on the boundary of the oscillating ellipsoidal vortex, we observed the formation of clusters. In the case of a rotating ellipsoidal vortex, we also observed pronounced clustering. Thus, we argue that unsteady ellipsoidal vortex regimes (oscillation and rotation), which induce chaotic motion of the nearby passive tracer’s trajectories, are still conducive to clustering of floating tracers observed in the density field, despite the intense deformation introduced by strain and shear.

Comparative numerical analysis of electromagnetic forces in DC and HFPC TIG welding

The paper presents a detailed theoretical analysis of the electromagnetic forces in the arc plasma and the weld pool metal in Tungsten Inert Gas (TIG) welding at direct current (DC) and high-frequency pulse current (HFPC) modulation with a frequency of 10 kHz. The electromagnetic (Lorentz) force, acting on arc plasma and metal is presented via potential (magnetic pressure) and rotational (equivalent electromagnetic force) force components. This approach allows us to substantially simplify the analysis of the Lorentz force effect on the arc plasma and weld pool metal under different arc burning modes. It was shown that in HFPC TIG welding with a given frequency, the effect of modulated current on the arc plasma is inherently non-stationary, whereas the effect on the weld pool metal is determined by the time-averaged magnitude of electromagnetic force throughout the period of current modulation. The proposed approach serves as a basis for numerical analysis of the electromagnetic forces in arc plasma and weld pool metal during DC and HFPC modes of the welding process. We established that the application of HFPC modulation promotes a greater intensity of both the gas-dynamic processes in the welding arc, thereby significantly increasing the pressure on the weld pool surface, and convective heat transfer from the most heated central region near the weld pool surface towards the weld pool bottom. Both these factors lead to an increase of the arc penetrability in the case of the HFPC mode compared with the DC mode, all other conditions being equal.