Arc Motion Research Articles

The Risk of Acute Infection Following Intra-Articular Corticosteroid Injection During Total Knee Manipulation Under Anesthesia

BackgroundManipulation under anesthesia (MUA) is an established option for improving motion in patients presenting with early stiffness following total knee arthroplasty (TKA). Intra-articular corticosteroid injections (IACI) are sometimes administered adjunctively, yet literature examining their efficacy and safety remains limited. Study DesignRetrospective, Level IV. MethodsA total of 209 patients (TKA = 230) were retrospectively examined to determine the incidence of prosthetic joint infections within 3 months following manipulation with IACI. Approximately 4.9% of initial patients had inadequate follow-up where the presence of infection could not be determined. Range of motion was assessed in patients who had follow-up at or beyond one year (n = 158) and was recorded over multiple time points. ResultsNo infections (0 of 230) were identified within 90 days of receiving IACI during TKA MUA. Before receiving TKA (preindex), patients averaged 111° of total arc of motion and 113° of flexion. Following index procedures, just prior to manipulation (pre-MUA), patients averaged 83° and 86° of total arc and flexion motion, respectively. At final follow-up, patients averaged 110° of total arc of motion and 111° of flexion. At six weeks following manipulation, patients had gained a mean of 25° and 24° of their total arc and flexion motion found at 1 year. This motion was preserved through a 12-month follow-up period. ConclusionAdministering IACI during TKA MUA does not harbor an elevated risk for acute prosthetic joint infections. Additionally, its use is associated with substantial increases in short-term range of motion at six weeks following manipulation, which remain preserved through long-term follow-up.

Influence of the aerodynamic flow on the dynamic characteristics of a lightning sweeping arc

Lightning arc attachments during swept strokes are key information in the lightning protection design of fast-moving aircraft, wind turbines, rockets, etc. However, numerical modeling has not achieved success to predict the movement of lightning sweeping arcs due to the limited understanding of the complex multi-physics convolution in the arc fluid at present. This work builds a dynamic magneto-hydrodynamic (MHD) arc model based on the setup in the laboratory simulation of the lightning continuing current and couples the electric–magnetic–thermal–force processes to get insights into the lightning arc dynamics. The MHD theory and Newton’s second law of motion are also incorporated to describe the movement of arc segments in the conditions of aerodynamic flows with different intensities. Results show that, at the center region of the arc, the electromagnetic force, thermal buoyancy, and aerodynamic force are competitive, and all are determiners in predicting the arc displacement. In contrast, at the root region of the arc, the electromagnetic force dominates the arc movement with a flow speed under 10 m/s, while aerodynamic force takes the dominant role when the flow speed exceeds 50 m/s. The arc sweeping distance expands from 0.02 to 1.01 m as the aerodynamic flow increases from 5 to 200 m/s. Meanwhile, when increasing the pitch angle of the arc-connected surface, the arc root becomes more attached to the surface and the sweeping distance is predicted to get reduced. The conclusions offer references to construct a numerical model and predict the complex arc movement during lightning sweeping strokes.

Research on dynamic characteristics of arc under electrode relative motion

The relative motion of the electrodes is a typical feature of sliding electrical contact systems. The system fault caused by the arc is the key problem that restricts the service life of the sliding electrical contact system. In this paper, an arcing experimental platform that can accurately control the relative speed and distance of electrodes is built, and the influence of different electrode speeds and electrode distances on arc motion characteristics is explored. It is found that there are three different modes of arc root motion: single arc root motion mode, single and double arc roots alternating motion mode, and multiple arc roots motion mode. The physical process and influence mechanism of different arc root motion modes are further studied, and the corresponding relationship between arc root motion modes and electrode speed is revealed. In addition, to further explore the distribution characteristics of arc temperature and its influencing factors, an arc magnetohydrodynamic model under the relative motion of electrodes is established, and the variation law of arc temperature under the effect of different electrode speeds and electrode distances is summarized. Finally, the influence mechanism of electrode speed and electrode distance on arc temperature, arc root distance, and arc root speed is clarified. The research results enrich the research system of arc dynamic characteristics in the field of sliding electrical contact, and provide theoretical support for restraining arc erosion and improving the service life of the sliding electrical contact system.

Research on the underwater cutting mechanism of flux-cored arc cutting for aluminum alloy process

With the fast-growing demand of aluminum alloys in ships and deep-sea pressure structures, an accurate and efficient underwater cutting operation for aluminum alloy is significant. However, its underwater arc cutting mechanism is still not clear enough, which limits its further application. The challenges lie in poor underwater visibility and complex underwater environment. In this study, process experiments, underwater sensor, and numerical simulations were conducted during cutting process to investigate the cutting mechanism of 5,052 aluminum. Firstly, the effect of parameters were investigated on cutting current, voltage, and water depth on the underwater kerf formation. In addition, three typical kerf formations, including “V” type, “II” type and “∧” type, were found; Secondly, visual sensing system was setup to monitor the cutting arc trajectory and the combustion process during the cutting process. Specially, the underwater burning phenomenon was observed. Finally, Finite Element Analysis was performed to further analyze the underwater arc cutting kerf formation of aluminum alloy. A semi-ellipsoidal composite heat source was applied to simulate the underwater arc, and the aluminum thermal reaction-generated heat was introduced. A dynamic method named “birth and death elements” was utilized to simulate the removal of molten metal. The temperature test results show that the simulation process is feasible. All results showed that different cutting parameters led to different cutting mode and affected the kerf forming. 5,052 aluminum alloy in the deep water environment (≥50 m) kerf significantly narrowed. The kerf cross-section produces an inward concavity and the kerf surface is as wide as the cutting wire. The aluminum kerf forming process is greatly impacted by the process parameters and self-propagating high-temperature synthesis reaction during aluminum alloy cutting. The periodicity of the cutting process was computed by the numerical simulation with the arc motion trajectory monitored by the high-speed camera. The numerical results of temperature distribution and kerf shape were consistent with the experimental data, which revealed the cutting mechanism.

Simulation Analysis and Experimental Investigation of the Iron-Core Cup-Shaped Transverse Magnetic Field Contact

The transverse magnetic field (TMF) contact uses self-generated TMF to drive the arc movement and has been widely used in the field of vacuum breaking. An iron-core cup-shaped TMF contact was designed by adding an iron core and changing the parameters of the cup wall based on the structure of the traditional cup-shaped TMF contact to optimize the gap magnetic field distribution of the cup-shaped TMF contact and improve the force characteristics of the vacuum arc. From the aspects of simulation and experiment, the gap magnetic field characteristics, arc force, and vacuum arc characteristics of the iron-core cup-shaped TMF contact were studied. The simulation analysis model of the iron-core cup-shaped TMF contact was established by COMSOL Multiphysics software, and the gap magnetic field characteristics and arc force were analyzed. Compared with the traditional cup-shaped TMF contact, the tangential electromagnetic force on the arc is increased by 30%, and the radial electromagnetic force is reduced by 36%. The arcing processes of the iron-core cup-shaped TMF contact and the traditional cup-shaped TMF contact were analyzed through experiments. The results show that the iron-core cup-shaped TMF contact has a faster arc movement speed, longer movement duration, and less metal droplet splashing.

Kinematic Alignment May Reduce Opioid Consumption and Length of Stay Compared to Mechanically Aligned Total Knee Arthroplasty.

Previous studies have sought to determine the effects of total knee arthroplasty (TKA) using kinematic alignment (KA) versus mechanical alignment (MA) to reproduce the native knee alignment and soft tissue envelope for improved patient satisfaction. There are limited studies that compare acute perioperative outcomes between KA and MA patients as it pertains to pain-related opioid consumption and hospital length of stay (LOS). This study aims to compare early KA and MA in restoring function and rehabilitation after surgery to reduce hospitalization and opioid consumption. A retrospective review of 42 KA and 58 MA primary TKA patients performed by a single surgeon between 2020-2021 was conducted. Demographics were controlled between groups and radiographic measurements and functional outcomes were compared. Pain was evaluated with inpatient/outpatient morphine milligram equivalents (MME) and visual analogue scale (VAS) scores. Mobility was assessed using multiple measures by a physical therapist. Mean preoperative and 3-month postoperative flexion range of motion (ROM) were analyzed, and overall complications, LOS, and non-home discharge between groups compared. Continuous variables were compared using the Wilcoxon rank-sum test, and categorical variables were compared using the chi-square or Fisher exact test. Statistical significance was set at P < 0.05. KA patients had shorter LOS (1.8 vs 3.1 days) and less cumulative opioid requirements compared to MA patients (578 vs 1253 MME). On postoperative day 0, KA patients ambulated on average twice the distance of MA patients (20 vs 6.5 feet). KA patients had residual tibia component in varus (1.4° vs -0.3°), femoral component in valgus (-1.9° vs 0.2°), and valgus joint line obliquity compared with MA (-1.5° vs 0.2°). There were no significant differences between 3-month postoperative flexion arc motion, discharge destination, KOOS or SF-12 outcomes, and surgical complication rates between groups. By restoring the native joint line obliquity and minimizing the frequency of ligament releases, KA for TKA may improve pain relief, early mobility, and decreased length of stay compared with traditional methods of establishing neutral limb axis by MA.

Dynamic physical characteristics of DC arc on arcing horn for HVDC grounding electrode line

The dynamic physical characteristics of a DC arc on an arcing horn for a high voltage direct current (HVDC) grounding electrode line are significantly different from those of the switching device arc, secondary arc, AC fault arc and pantograph-catenary arc. In this work, an experimental platform for the DC arc on the arcing horn was built, and mechanisms of the arc column short circuit and arc root movement were studied. This work further analyzes the characteristics and mechanisms of the arc motion when wind speed and direction, magnetic field and the expansion angle of the electrode are varied. Arc root movement is more likely to occur at the upper electrode. There is a competitive relationship between arc expansion and the transferring effect. The effect of wind on the arc column is greater than the effect on the arc root. The magnetic field has a significant driving effect on both the arc column and the arc root. The research results provide a comprehensive experimental basis for further probing the method of DC arc suppression, and the improvement of the arcing horn.

Modified paratricipital approach without mobilization of the ulnar nerve prevents postoperative ulnar neuropathy in distal humerus fractures

BackgroundIn distal humerus fracture surgery, postoperative ulnar neuropathy is a common complication. The present study assessed the utility of the modified paratricipital approach for preventing ulnar neuropathy. This approach preserved the continuity of the attachment of the triceps with the ulnar nerve and allowed anterior subluxation of the ulnar nerve onto the hardware to be avoided. MethodsFrom December 2018 to March 2020, 13 patients who underwent surgery for distal humerus fracture through the modified paratricipital approach at our hospital were prospectively enrolled in the study. Ulnar neuropathy, Mayo Elbow Performance Score (MEPS), and Range of motion (ROM) were evaluated. ResultsNo postoperative ulnar neuropathy was observed. At the final follow-up, the mean Mayo Elbow Performance score was 97.7 (range, 85–100). The mean arc motion was 132.7° (range, 115°–145°) with a mean flexion contracture of 4.2° (range, 0°–10°) and mean flexion of 136.2° (range, 120°–145°). Hardware breakage leading to a loss of reduction occurred in one case, but the other fractures united. ConclusionsOur results demonstrated the effectiveness of the modified paratricipital approach for preventing postoperative ulnar neuropathy. The modified paratricipital approach is a safe and reliable method of performing distal humerus fracture surgery.

Football Offense Training Strategy Based on Fractional Differential Mathematical Modeling

Abstract This paper establishes the parameters of the ball trajectory based on the fractional differential equation model. At the same time, this paper quantifies the shooting power of direct free kicks. In this paper, the resistance effect of air on the motion of the center of mass is considered. And the dynamic equation of the football arc motion is established. In this way, we obtain the analytical solution of the differential equation of order. The research shows that the correlation between the fitting equation of the football flight trajectory and the prediction equation is 96.55%. The algorithm model in this paper can effectively predict the flight path of football. The research theory of this paper provides a theoretical basis for football offensive training strategies.

Pinching arc plasmas by high-frequency alternating longitudinal magnetic field

Arc plasmas have promising applications in many fields, and exploring their properties is of interest. This research paper presents detailed pressure-based finite volume simulations of an argon arc. Simulations of the free-burning argon arc show good agreement with experiment. We observe an interesting phenomenon that an argon arc concentrates intensively in a high-frequency alternating longitudinal magnetic field. This is different from existing constricting mechanisms, as here the arc is pinched through continuous dynamic transitions between shrinking and expansion. The underlying mechanism is that via working together with an arc's motion inertia, the applied high-frequency alternating magnetic field is able to effectively play a “plasma trap” role, which leads the arc plasma to be confined to a narrower space. This finding may provide a new approach to constrict arc plasmas.

Thermal simulation of migration mechanism of the Halmahera volcanic arc, Indonesia

• A thermal evolution model is proposed to explain the activity of the Halmahera volcanic arc. • Our results can explain why there are magmatic gaps and volcanic arc migration during subduction and rollback. • The thermal simulation results show that a smaller subduction rate or a larger convergence rate are favorable to the occurrence of island arc magmatism. The Halmahera volcanic arc has experienced intermittent volcanic activity and location migration since the Pliocene. Two factors affect the volcanic arc magmatism. One is the dehydration depth of hornblende in the oceanic crust and serpentinite in the lithospheric mantle in the subducted slab. The other is the subducted slab and mantle wedge temperature structure, controlled by the subduction rate and plate convergence rate. Thermal simulation results show that conditions are favorable to the occurrence of island arc magmatism at a lower subduction rate with the same convergence rate, or at a higher convergence rate with the same subduction rate. The Miocene–Pliocene favored the occurrence of island arc magmatism in the high temperature region, because there was a lower subduction rate beneath the Halmahera volcanic arc. After the Middle Pliocene, there was cessation of volcanic activity and a volcanic gap, with subsidence of the mantle wedge high temperature region, increase of the partial melting depth, and decrease of the melting amount, because there was an increased subduction rate beneath the Halmahera volcanic arc and a decreased westward convergence rate of the eastern microplate fragments. In the Holocene, the Halmahera arc moved to a new location and resumed volcanic activity. It is because continuous arc–arc collision blocked the westward movement of the Halmahera volcanic arc, the relative convergence rate of the eastern microplate increased, which resulted in the formation of a high temperature region favorable to island arc magmatism.

Experimental Study on the Working Characteristics of a Pre-combustion AC Plasma Jet Igniter

A new pre-combustion AC plasma jet igniter has been designed. The pre-combustion plasma jet igniter can widen the ignition envelope for the aeroengine and reduce the power consumption of the igniter. To fully exploit the ignition efficiency of the plasma jet, experimental studies concerning the operational parameters and the discharge and arc motion characteristics have been performed. The results showed that three discharge modes were formed in the new igniter, namely, the Intermittent Breakdown Mode (IBM), the Stable Breakdown Mode (SBM) and the Stable-Intermittent Breakdown mode (S-IBM), the three different discharge modes corresponding to different arc shapes and movement processes. Moreover, the addition of kerosene readily changed the discharge state from the SBM to the IBM. The discharge state and discharge power of the igniter were affected by the working parameters. The discharge power increased with increase of the output voltage of the regulator, and an increase in the air supply affected the discharge power when the output voltage of the regulator was varied. After the addition of kerosene, the discharge power of the igniter was reduced to a certain extent, the maximum reduction being up to 47.7%.

Investigation on the arc root characteristics of vacuum arc between the iron-core cup-shaped transverse magnetic field contacts

The severity of the contact surface ablation determines the breaking capacity of the vacuum circuit breaker, and the interaction between the arc root and the electrode is the main cause of the contact surface ablation. The characteristics of the arc root determine the magnitude of the electromagnetic force received by the arc during the movement stage as well as the shape and speed of the arc movement. It will eventually affect the temperature of the contact surface and the ablation situation. This paper studied the arc root characteristics of high-current constricted vacuum arcs between the iron-core cup-shaped transverse magnetic field contacts and put forward the idea of using the ratio of cathode and anode arc root areas to quantitatively analyze the concentration of vacuum arc. The research on the arc root characteristics of the vacuum arc can help to improve the arc characteristics and arcing mechanism, and the proposition of the ratio can provide a new method for the study of constricted arc. This can provide a basis for improving the arc extinction performance of the switch, reducing the ablation of the contact material, and improving the contact life.

Numerical investigations on the electric arc behavior upon contact opening in a low-voltage switch under the effect of external magnetic field

This paper is devoted to investigate the effect of a strong external magnetic field on the electric arc created by contact opening in a low-voltage switch. The low-voltage switch is powered by a DC generator with an RL charge as in photovoltaic installations. During contact opening, the arc motion is dominated by Laplace and hydrodynamic forces. An external magnetic field is added to strengthen the magnetic forces and to accelerate the arc extinction. Significant differences depending on the external magnetic field intensity can be investigated. Numerical simulations, developed using COMSOL Multiphysics, are compared to experimental measurements performed on experimental device specially designed for tests to provide a better understanding of the physical phenomena involved.

Quasi-Continuous Network Structure Greatly Improved the Anti-Arc-Erosion Capability of Ag/Y2O3 Electrical Contacts.

Ag/Y2O3 has excellent potential to replace Ag/CdO as the environmentally friendly electrical contact material. Using spherical Y2O3 as the starting material, Ag/Y2O3 contacts with a quasi-continuous network structure were successfully fabricated by a low-energy ball milling treatment. The mean size of Y2O3 used ranged from 243 to 980 nm. Due to the differences in the size of Y2O3, Ag/Y2O3 contacts had different primitive microstructures, thereby exhibiting distinctive anti-arc-erosion capabilities. Ag/Y2O3 contact prepared using 243 nm Y2O3 showed the best anti-arc-erosion capability and the most outstanding electrical performance measures, such as low contact resistance, less mass transfer, and no failure up to 105 cycle times. The quasi-continuous network structure formed in the micro-scale was responsible for the excellent electrical performance. The short distance between Y2O3 particles in the network promoted the cathode arc motion, and thus alleviated the localized erosion. The results obtained herein may inspire further attempts to design electrical contacts rationally.

Impact of a Transient and Asymmetrical Distribution of the Electric Arc on the Solidification Conditions of the Ingot in the VAR Process

Vacuum Arc Remelting is an important method of processing reactive and refractory liquid metal alloys, including titanium and zirconium alloys. Recent measurements of the electric arc dynamics under the presence of a time-varying magnetic field during an industrial melt of a Ti64 alloy provided evidence of the existence of an ensemble arc motion. Such motion is responsible for transient and non-axisymmetric inputs of electric current and energy at the top surface of the remelted ingot. The present work is an attempt to evaluate, using a simplified numerical simulation approach, to what extent the solidification conditions of the VAR ingot and, consequently, the quality of the final product, may be affected by this phenomenon. The reported results indicate that, under the worst case conditions, the relative vanadium segregation in the solidified ingot can reach values as high as 12.5%.

Investigations of Working Characteristics of Transferred Arc Plasma Torch Volume Reactor

A transferred arc plasma torch chemical rector was used to process waste formed from mixtures of dry clay powder and hydroquinone. Such reactors are best suited for the treatment of electrically conductive waste. In these types of reactors, the electric arc moves chaotically throughout the entire reactor volume, making it possible to ensure an even temperature distribution in the reaction zones. An analysis of the literature has shown that there are not many study results related to this type of reactor. The novelty of the work is that the behavior of the operating electric arc inside the reactor was recorded by using a high-speed camera. The distribution of the temperature profile at the cooled reactor wall was investigated. The electrical potential difference inside the reactor was also investigated. To better understand the behavioral properties of the electric arc when the reactor is filled with treated material, hydroquinone-contaminated clay was used. In this case, the movement of the electric arc, as well as the probability of its formation, is the greatest at the location where the thinnest layer of the material to be processed is located. In addition, it has been observed that the use of a graphite anode poses problems because, over time, the anode of such a design deforms due to interactions with the electric arc. While analyzing research results, it can be observed that these types of reactors are very suitable for the treatment of electrically conductive materials and for the treatment of small amounts of nonconductive materials when the material occupies a relatively small part of the reactor. A further development of these studies in the future is planned in order to make the reactors as versatile as possible and as suitable as possible for handling the widest range of materials possible.

Numerical simulation of external magnetic field effect on arc plasma after molten metal bridge breaking under different electrode opening velocities

In this study, a three-dimensional electromagnetic thermal fluid simulation program was developed to simulate arc movement numerically while considering metal vapor generated from a molten metal bridge along with an electrode opening under external magnetic field application. The change in the physical properties of the arc and the increment rate of the arc voltage per unit length under different electrode opening velocities were analyzed by applying an external magnetic field with different intensities. It was found that the current path of the arc became dispersed when the electrode opening velocity was high because the metal vapor generated from the molten metal bridge remained dominant and highly concentrated. Before the completion of the electrode opening process, the difference in the increment rate of the arc voltage per unit length at different electrode opening velocities became more significant when an external magnetic field was applied. This was because under high and low electrode opening velocities, the cross-sectional area of the arc became narrow and broad, respectively.

Experimental Study on the Extinction Characteristics of Secondary Arc Under Different Secondary Arc Currents Near Outdoor Insulator

On the transmission lines, the secondary arc is the arc that remains at the fault point after the short-circuit current is interrupted, which may pose a threat to the stable operation of the power system. In this article, the extinction characteristics of secondary arc near an outdoor insulator under different secondary arc currents are studied experimentally. The secondary arc has different extinction characteristics under different secondary arc currents of 10, 30, and 50 A. The arcing time, length, morphology, diameter, and breakdown voltage of secondary arc are discussed. Experimental results show that, with the increase in the secondary arc current, the arcing time also increases. The development of the secondary arc has stage characteristics. The length of the secondary arc increases steadily in the first stage and fluctuates greatly in the second stage. In addition, during the single discharge in the second stage, the morphology of the secondary arc will change significantly. The breakdown voltage of the upper electrode in the negative polarity is higher than that in the positive polarity, and it is found that this polarity effect is related to the motion of the secondary arc in space. The research results could provide some reference for investigating the physical characteristics and suppression measures of secondary arc.

Experimental investigation of discharge characteristics of alternating current rotating gliding arc discharge under high air pressure

In order to study the stability of gliding arc plasma discharge under mal-conditions, an experimental system for studying the high air pressure alternating current rotating gliding arc discharge is built. The discharge characteristics, arc motion characteristics and spectral characteristics of rotating gliding arc discharge are analyzed under high pressure experimentally. Experimental results show that the voltage, current and energy increase in the gliding arc discharge with the increase of air pressure. As the air pressure rises to 0.52 MPa, the discharge energy increases from 84.74 to 147.13 J. With the increase of gas pressure, the breakdown frequency of the arc does not change monotonically, but reaches a maximum value of 26.55 kHz at 0.2 MPa, while the emission spectral intensity increases. The “arc channel mutation” occurs in the process of arc motion under high pressure. The electron excitation temperature in the process of gliding arc discharge is calculated by the two-line method, and the electron excitation temperature of gliding arc discharge is 0.8153 eV at an atmosphere pressure. The electron excitation temperature rises with the increase of air pressure. The excitation temperature increases to 5.3165 eV at an air pressure of 0.4 MPa.