Arc Position Research Articles

Core Mass Estimates in Strong Lensing Galaxy Clusters: A Comparison between Masses Obtained from Detailed Lens Models, Single-halo Lens Models, and Einstein Radii

Abstract The core mass of galaxy clusters is both an important anchor of the radial mass distribution profile and a probe of structure formation. With thousands of strong lensing galaxy clusters being discovered by current and upcoming surveys, timely, efficient, and accurate core mass estimates are needed. We assess the results of two efficient methods to estimate the core mass of strong lensing clusters: the mass enclosed by the Einstein radius (M(<θ E), where θ E is approximated from arc positions, and a single-halo lens model (M SHM), compared with measurements from publicly available detailed lens models (M DLM) of the same clusters. We use data from the Sloan Giant Arc Survey, the Reionization Lensing Cluster Survey, the Hubble Frontier Fields, and the Cluster Lensing and Supernova Survey with Hubble. We find a scatter of 18.1% (8.2%) with a bias of −7.1% (1.0%) between M corr < θ arcs (M SHM) and M DLM. Last, we compare the statistical uncertainties measured in this work to those from simulations. This work demonstrates the successful application of these methods to observational data. As the effort to efficiently model the mass distribution of strong lensing galaxy clusters continues, we need fast, reliable methods to advance the field.

Telltale signs of metal recycling in the circumgalactic medium of a z ∼ 0.77 galaxy

ABSTRACT We present gravitational-arc tomography of the cool-warm enriched circumgalactic medium (CGM) of an isolated galaxy (‘G1’) at z ≈ 0.77. Combining VLT/MUSE adaptive-optics and Magellan/MagE echelle spectroscopy, we obtain partially resolved kinematics of Mg ii in absorption and [O ii] in emission. The unique arc configuration allows us to probe 42 spatially independent arc positions transverse to G1, plus four positions in front of it. The transverse positions cover G1’s minor and major axes at impact parameters of ≈10–30 and ≈60 kpc, respectively. We observe a direct kinematic connection between the cool-warm enriched CGM (traced by Mg ii) and the interstellar medium (traced by [O ii]). This provides strong evidence for the existence of an extended disc that co-rotates with the galaxy out to tens of kiloparsecs. The Mg ii velocity dispersion (σ ≈ 30–100 km s−1, depending on position) is of the same order as the modelled galaxy rotational velocity (vrot ≈ 80 km s−1), providing evidence for the presence of a turbulent and pressure-supported CGM component. We regard the absorption to be modulated by a galactic-scale outflow, as it offers a natural scenario for the observed line-of-sight dispersion and asymmetric profiles observed against both the arcs and the galaxy. An extended enriched co-rotating disc together with the signatures of a galactic outflow, are telltale signs of metal recycling in the z ∼ 1 CGM.

Did accretion of the Caribbean oceanic plateau drive rapid crustal thickening in the northern Andes?

The onset of orogenic shortening in the northern Andes Mountains coincided with latest Cretaceous accretion of the Caribbean oceanic plateau. We present isotopic data (εHf in zircon and εNd) coupled with arc position to test whether accretion led to abrupt crustal thickening in the northern Andes of Ecuador and Colombia. A rapid isotopic excursion toward more evolved crustal compositions was synchronous with ca. 75–70 Ma collision in Ecuador and preceded a similar deviation in Colombia at ca. 70–55 Ma. The rapid but diachronous shift to more evolved isotopic signatures is attributed to progressive northward accretion of the oceanic plateau and associated thickening of continental crust. We emphasize the effects of accretion on the magmatic evolution of Cordilleran-type margins, initially provoking shortening and crustal thickening, and ultimately providing a substrate for subsequent arcs.

Simplified Calculation Method of Wharf Bank Slope Stability Considering Old Piles

Based on the requirements of durability, a simplified calculation method of wharf slope stability considering the anti-sliding effect of old piles is derived according to the allowable cracks of old piles. Firstly, the acting force between the sliding soil and the pile is assumed to be distributed in a triangle, and the position of the resultant force of each pile is determined. According to the maximum crack width limit of the old pile, the maximum bending moment that the old pile can bear is calculated. According to the maximum bending moment, the maximum horizontal force at the mud surface, where is the slip arc position, can be inversely calculated, then the maximum anti-sliding force provided by the old piles can be obtained, and the stability of wharf bank slope considering the anti-sliding effect of the old piles is checked. In the slope stability calculation of Beira fishing wharf reconstruction project in Mozambique, the simplified calculation method considering the anti-sliding effect of old piles is adopted. The stability coefficient of wharf bank slope meets the requirements, and the extra treatment of bank slope is cancelled, which saves the project investment and construction period.

The 2 Ga eclogites of Central Tanzania: Directly linking age and metamorphism

The ca. 2 Ga retrogressed eclogites in the Usagaran Belt in central Tanzania are among the oldest documented eclogites in the world. As such, they have been used to pinpoint the thermal conditions of the onset of modern style subduction on Earth. Two samples of retrogressed mafic eclogite have been interrogated to reconstruct the metamorphic history of the subducted crust. The samples are several kilometres apart, separated by a mylonitic upper amphibolite-transitional granulite foliation. Lu--Hf garnet geochronology pinpoints eclogite metamorphism at 1994 ± 9 Ma, supported by rutile U--Pb geochronology. Zircon U--Pb geochronology supports subduction metamorphism at ca. 2000 Ma. Mineral equilibria modelling and Zr in rutile thermometry suggests the retrogressed eclogites reached a minimum pressure of 18 kbar at approximately 800 °C, consistent with a warm subduction thermal gradient. These conditions were followed by amphibolite-granulite-facies overprinting. Proposed tectonic models for the formation of the eclogites involve either east-dipping subduction of the Tanzanian Craton margin, or west-dipping subduction of oceanic crust under the Tanzanian Craton. The retrogressed eclogites were likely exhumed via slab breakoff driven buoyancy of the oceanic crust and transferred to shallow crustal levels in a back arc position. This data, combined with data from eclogites from the Eburnian-Transamazonian and Ubende orogens, demonstrate the possible existence of a large subduction system on the margin of west Africa from ca. 2.1–1.9 Ga. This system has led to the preservation of several eclogitic rocks, which suggests that modern style subduction was operating on significant geographic and temporal scales at this time.

Metal Transfer Mechanisms in Hot-Wire Gas Metal Arc Welding

The hot-wire gas metal arc welding (HW-GMAW) process is widely used to increase the melting rate of a secondary wire through Joule heating without significantly increasing the total heat input to the substrate. Because there is limit-ed knowledge regarding the associated arc dynamics and its influence on bead geometry, the present study considers how these are affected by the hot-wire polarity (negative or positive), hot-wire feed rate, and hot-wire orientation using a two-factor full factorial experiment with three replicates. During welding, high-speed imaging synchronized with current and voltage acquisition to study the arc dynamics. After this, each replicated weld was cut into three cross sections, which were examined by standard metallography. The preliminary results suggest that the arc was stable within the range of process parameters studied. The arc polarity played a role on arc position relative to the hot wire, with a decrease in penetration depth observed when the arc was attracted to the hot wire.

Evaluation of airflow pattern and thermal behavior of the arched greenhouses with designed roof ventilation scenarios using CFD simulation.

Natural ventilation is an effective energy-saving strategy conducive to promoting sustainable agricultural production. A comprehensive numerical simulation is performed to predict the airflow pattern and thermal behavior in different arched greenhouses. The defined arc chord angle and position angle are employed to examine the natural ventilation process and corresponding roof vent scenarios. The numerical simulation is compared with the experimental data and good agreements are observed. Various configurations of ventilated structures, wind conditions and ventilation layouts are simulated on a high-resolution polyhedral grid based on a grid sensitivity analysis, which is beneficial to the optimization of greenhouse cooling combined with the water circulation heat collection system. The cooling effect in summer is analyzed by estimating the ventilation flow rate and microclimate inhomogeneity. The results demonstrate that the position angle of 85° of the arched greenhouses is an optimum ventilation direction and its impact on the microclimate is marginally affected by the change of the ventilation structure. The designed ventilation scheme has perfect air exchange capacity and cooling effect because the average air temperature can be reduced by 1.5°C more than the existing greenhouse in 10 minutes of ventilation. Likewise, the results show that the temperature and velocity inhomogeneities are approximately decreased by 33.3% and 11.89%, respectively. The practical value of the research is expected to provide basic quantitative conclusions for evaluating the natural ventilation performance.

Feedback-Based Control Over the Spatio-Temporal Distribution of Arcs During Vacuum Arc Remelting via Externally Applied Magnetic Fields

Ampere Scientific’s VARmetric TM measurement system for Vacuum Arc Remelting (VAR) furnaces passively monitors the distribution of arcs over time during VAR in real time. The arc behavior is known to impact both product yield and quality and can pose potentially catastrophic operating conditions. Arc position sensing with VARmetric TM enables a new approach to control the heat input to the melt pool. Transverse external magnetic fields were applied to push the arcs via the Lorentz force while measuring the arc location to control the arc distribution over time. This has been tested on Ampere Scientific’s small-scale laboratory arc furnace with electromagnets used for control for up to 60 seconds while monitoring the arc location with VARmetric TM. The arc distributions were shown to be significantly different from the uncontrolled distributions with distinct thermal profiles at the melt pool. Alternatively, this type of control can be periodically applied to react to undesirable arc conditions.

Diagnosing an ancient shallow-angle subduction event from Cenozoic depositional and deformational records in the central Andes of southern Peru

The spectrum of responses exhibited by upper plates to changes in the subduction zone geometry remains poorly constrained. In the Paleogene, the central Andes in southern Peru potentially experienced an episode of flat or shallow-angle subduction. Presented here are new geochronologic, thermochronologic, basin subsidence backstripping analysis, and 2D flexural modeling results. These are synthesized with existing records on the temporal variation of the volcanic arc position, basin fill chronostratigraphy, deformation style and location, and geophysical constraints on lithospheric architecture to investigate how this segment of the Andes developed during a proposed ancient modification to the subduction zone dip. Basin chronostratigraphy confirms persistent contribution from volcanic arc products during the Eocene–Miocene, arguing against complete cessation of arc magmatism. Sediment accumulation was pulsed and generally more rapid during the late Eocene–Oligocene event. The subsidence curve is generally concave-up, atypical for a foreland basin situated within the compressional central Andes. The tectonic subsidence magnitude observed from backstripping analysis is at least 1 km less than the magnitude of subsidence predicted by 2D flexural model results. This suggests a component of basin uplift, potentially as a dynamic response to subduction shallowing, may have opposed flexural subsidence that was driven by crustal thickening and topographic loading. New geo- and thermochronologic results constrain the timing of Late Triassic pluton emplacement, and initial unroofing that predates the proposed timing of flat or shallow-angle subduction. This new timing suggests initial deformation, with mixed thin- and thick-skinned deformation style, in the Eastern Cordillera may be linked to reactivation of inherited structures rather than inboard deformation advance as a response to subduction flattening. The lack of basement-cored uplifts, preservation of mantle lithosphere beneath this segment of the central Andes, and volcanic arc patterns argue against the occurrence of a flat slab event. Instead, these results point to a shallow-angle subduction event and highlight the diverse behaviors of Cordilleran margins affected by variable subduction zone geometry and upper plates with inherited crustal heterogeneities.

Overriding Plate Velocity Control on Surface Topography in 2‐D Models of Subduction Zones

AbstractWe study the dynamically induced flexural topography in subduction numerical mechanical models. We focus on the topographic changes at the overriding plate (OP) surface induced by variations in OP kinematics, particularly when the subducting plate (SP) has a stationary motion after having reached the rigid base of the upper mantle. Our models consist of two viscoelastic plates with free surfaces and an isoviscous mantle. Friction is imposed along the planar subduction interface. We first characterize the main topographic features at a constant OP velocity, using spatial definitions based on geometrical estimations of the volcanic arc position. The models exhibit the formation of a bulge in the forearc area followed landwards by a depression and a smaller second bulge, both bracketing the arc region. The steady‐state distance to the trench of these features increases with OP velocity. Their amplitude is affected by the far‐field OP tectonic regime that depends on kinematics, and plates and subduction interface strength. We next test the effect of sudden changes in OP velocity. An OP acceleration yields a transient topographic tilt, during which the outer forearc quickly subsides whereas the arc region uplifts, and that is followed by reverse slower motions. An OP slowdown induces opposite motions. The rates of elevation change during the tilt are approximately proportional to velocity variations and mainly sensitive to the SP strength. The rates are higher than 0.1 mm/yr for velocity changes higher than 1 cm/yr. We suggest that topographic accommodations of OP velocity changes should be considered when quantifying nonisostatic topography.

Development of a highly productive GMAW hot wire process using a two-dimensional arc deflection

Gas metal arc welding (GMAW) processes are used in a wide range of applications due to their high productivity and flexibility. Nevertheless, the supplied melting wire electrode leads to a coupling of material and heat input. Therefore, an increase of the melting rate correlates with an increase of the heat input by the arc at the same time. A possibility to separate material and heat input is to use an additional wire, which reduces penetration and worsens the wetting behaviour. Consequently, bead irregularities such as bonding defects or insufficient root weldings can occur. In the context of this article, a controlling system for a two-dimensional magnetic arc deflection is presented, which allows to influence arc position as well as material transfer. The analysed GMAW hot wire process is characterised by high melting rates while also realising a sufficient penetration depth and wetting behaviour.

Relationship between the Thickness of the Coracoid Process and Latarjet Graft Positioning-An Anatomical Study on 70 Embalmed Scapulae.

Background: The Latarjet procedure is a popular technique with the aim of the reconstruction of glenoid cavity bone defects in patients with chronic anterior shoulder instability. Studies have shown that the Congruent arc Latarjet procedure is better able to reconstruct larger defects than the Classic Latarjet, but there is a lack of information on the limitations of both methods. Methods: The dimensions of the glenoid width and the native coracoid process of two groups with 35 Formol-Carbol embalmed scapulae each were measured using a digital caliper. The relationship between the coracoid graft and the anterior-posterior diameter of the glenoid cavity was calculated to determine the maximum defect size of the glenoid cavity width, which can be treated by both Latarjet techniques. Results: The average restorable defect size of the anterior segment of the glenoid cavity was 28.4% ± 4.6% (range 19.2%–38.8%) in the Classic Latarjet group, and 45.6% ± 5.2% (range 35.7%–57.1%) in the Congruent arc Latarjet group. Based on our results, the feasibility of the Classic Latarjet procedure to reconstitute the anatomical width of the glenoid cavity was 86% in a 25% bone loss scenario, and only 40% in a 30% bone loss scenario. Conclusion: Based on our results we are unable to define a clear threshold for the optimal Latarjet graft position. In glenoid cavity defects <20%, the Classic Latarjet technique usually provides enough bone stock for anatomical reconstruction. Defects ≥35% of the glenoid cavity width should only be treated with a coracoid graft in the Congruent arc position. In the critical area between 20% and 35% of bone loss, we suggest the preoperative assessment of coracoid dimensions, based on which the graft position can be planned to restore the anatomical anterior-posterior diameter of the glenoid cavity.

Calculation and Analysis of the Relationship Between the Efficiency and Position of Electric Arcs and Power Consumption in Electric Arc Furnaces (EAF) of Smaller and Larger Capacity. Part 2. Calculation and Analysis of the Relationship Between Position of Arcs, Walls and Power Consumption

The arc efficiency and specific power consumption were calculated and analyzed for the small (1.5 to 20 tons) and large (100 to 120 tons) capacity electric arc furnaces. In the small-capacity furnaces, the increased specific power consumption for melting the furnace charge (475 to 500 kW · h/t) is associated with low arc efficiency (0.55 to 0.57). In the large-capacity furnaces, the arc efficiency is 0.78 to 0.8 and specific power consumption is 360 to 375 kW · h/t.

The effect of arc position on laser-arc hybrid welding of 12-mm-thick high strength bainitic steel

More attentions have been paid on humping characteristic in single pass high energy density welding of medium or thick plate in recent years. In this paper, the hump phenomenon of the weld root is observed by laser-leading laser-arc hybrid welding of 12 mm-thick steel plate. Combining with the surface molten pool flow behavior, force mechanism of force analyzed, the hump formation process can be divided into pool pooling stage, pool sagging growth stage, and the solidification stage. It is proved that the balance between gravity and surface tension of the molten pool is the main reason for the formation of hump. Furthermore, the arc-leading laser-arc hybrid welding process was realized to obtain single-pass welding joint without hump defects. In view of comparing and discussing the droplet transition feature, electrical parameters, and exerted force under the optimal process of arc-leading and laser-leading, we had a better understanding of reasons why the arc-leading inhibits the formation of hump, and proved that the arc-leading electrical parameters are more stable.

Comparison of Arc Motion in Different Lifetime Sealed Vacuum Interrupters With RMF Contacts

Vacuum circuit breakers are well established in the distribution levels of the electrical power grids. To maximize the short-circuit interruption performance, an radial magnetic field (RMF)-contact design forces the arc from a fault current to rotate. The performance of the RMF-contact designs is usually evaluated in a model vacuum chamber with viewing ports that allows observing arc rotation with the help of high-speed cameras. These setups differ significantly from lifetime sealed vacuum bottles in geometry (and thus volume) and due to the fact that the main metallic vapor shield cannot be present. This, in turn, can affect the arc rotation behavior. In order to overcome these shortcomings, a new diagnostic tool has been developed to analyze the arcing behavior in standard lifetime sealed vacuum interrupters. Optical methods are not possible here, since the view is blocked by the opaque ceramics and the metallic vapor shield. For this reason, a Hall-sensor-based measuring system is applied, in which the variation in the magnetic field from the arc position is observed by multiple sensors. This paper presents the comparison of arc motion in lifetime sealed vacuum interrupters with different bottle geometries. For this purpose, investigations with identical spiral-shaped RMF contacts inside different vacuum bottle designs with differing vacuum volumes are performed. Also, for comparison, an interrupter with contrate cup contacts was investigated. Similarities and differences between the corresponding arc motion behaviors are discussed.

3D Analysis of Low-Voltage Gas-Filled DC Switch Using Simplified Arc Model

Electro-magnetic simulations have been used for the visualization of distribution of Lorentz force acting on a DC switching arc in low-voltage contactor. A simplified plasma model (black-box model) was applied for the description of arc conductivity. Arc geometry was gained from the high-speed camera images. Influence of arc position, arc current and of external magnetic field has been studied. Results have been compared with optical observations of the arc dynamics.

Calculation and Analysis of the Relationship Between the Efficiency and Position of Electric Arcs and Power Consumption in Electric Arc Furnaces (EAF) of Smaller and Larger Capacity. Part I. Calculation and Analysis of the Relationship Between Arc Efficiency and Power Consumption

Calculation and Analysis of the Relationship Between the Efficiency and Position of Electric Arcs and Power Consumption in Electric Arc Furnaces (EAF) of Smaller and Larger Capacity. Part I. Calculation and Analysis of the Relationship Between Arc Efficiency and Power Consumption

Switching arc inversion based on analysis of electromagnetic characteristics

Abstract It is difficult to describe the characteristics of an arc in low-voltage switching equipment in terms of its most essential features using conventional arc models. In this paper, arc inversion is introduced to explore a new research approach to examine the nature of low-voltage switching arcs. Based on electromagnetic analysis, the arc is equivalent to a group of threadlike current segments. Then, the arc parameters are obtained by inverting the magnetic data calculated at the sampling point array. The multi-population genetic algorithm (MPGA) is adopted to solve the Biot-Savart operator equations to search the arc position, with the current density inverted by the truncated generalized singular value decomposition (TGSVD), in which the regularization parameter is chosen by the generalized cross-validation (GCV) criterion. The result shows that, by combining the MPGA with TGSVD, both the position and current distribution of an arc can be reconstructed accurately, which can help realize arc control and guide the design of low-voltage switches with improved performance parameters.

Microstructure and properties of laser-arc hybrid welding thick bainitic steel joints with different arc position

The realization of 12mm thick laser-arc hybrid welding technology is the prerequisite for efficient production of new high-speed train bogies. In this work, for the laser-leading hybrid welding, the problem of hump defects in the root of the weld is easy to occur. The arc-leading mode is chosen to obtain the welded joint of high-strength bainitic steel with no hump, no unfilled and no porosity defects. Then the microstructure distribution of the welds of the high-strength bainitic steel is analyzed, which the weld metal is mainly composed of acicular ferrite and lath bainite and the heat affected zone mainly concludes coarse-grained bainite and granular bainite. Then, under the optimal process, the hardness distribution, arc action area size and weld impact performance of the laser-leading and arc-leading welds were compared. It was found that the arc-leading weld hardness distribution was more uniform and stable, and the hardness peaks both appear in the HAZ (coarse lath bainite), and the valleys both appear in partial phase-change zones (Bulk ferrite). Meanwhile, the arc-leading weld impact performance is 21.49% higher than that of laser-leading.

A comparison of TIG-MIG hybrid welding with conventional MIG welding in the behaviors of arc, droplet and weld pool

The influence of electrode relative position and TIG current variation on arc stability and weld formation of TIG-MIG hybrid welding were studied comparing with that of conventional MIG welding. The welding current-voltage waveform was analyzed to characterize the arc stability. When TIG arc was leading, the hybrid arc was more stable than conventional MIG welding even when the TIG current was as low as 50 A, while the TIG current should be higher than 100 A to avoid spatters when TIG arc was trailing. The arc shape and droplet transfer were investigated to describe the heat and force distribution in weld pool. When TIG arc was leading, the backward arc force and droplet impingement could not decrease the backward flow of molten metal. The increment of MIG arc length dispersed MIG arc heat and resulted in narrower weld width, compared with conventional MIG welding, which was the main factor to suppress undercut defect. When TIG arc was trailing, the forward arc force and droplet impingement significantly decreased the backward flow velocity and gave molten metal more time to spread transversely to suppress undercut defect. Regardless the relative position of TIG and MIG arcs, the hybrid welding speed could reach up to at least 1.5 m/min.