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Cold metal transfer arc additive manufacturing technique was used to produce 5356 aluminum alloy by adding refining agents to solve the problems of coarse grains and poor performance. Metallic powd...

Additive manufacturing (AM) technologies in metallic materials have experienced significant growth over recent decades. Concepts such as design for additive manufacturing have gained great relevanc...

Additive manufacturing (AM) of Mg alloys has become a promising strategy for producing complex structures, but the corrosion performance of AM Mg components remains unexploited. In this study, wire and arc additive manufacturing (WAAM) was employed to produce single AZ31 layer. The results revealed that the WAAM AZ31 was characterized by significant grain refinement with non-textured crystallographic orientation, similar phase composition and stabilized corrosion performance comparing to the cast AZ31. These varied corrosion behaviors were principally ascribed to the size of grain, where cast AZ31 and WAAM AZ31 were featured by micro galvanic corrosion and intergranular corrosion, respectively.

In this work, the kinetics of the growth of austenite grains upon heating, the features of the processes of dynamic and static recrystallization occurring at various temperature-deformation modes of plastic deformation are investigated. Phase transformations have been studied during continuous cooling of hotdeformed austenite in low-alloy “Arc”-steel with a yield point of at least 420 MPa. The studies carried out made it possible to determine the thermal deformation parameters that ensure the formation of a finely dispersed homogeneous ferrite-bainitic structure, on the basis of which technological recommendations for industrial production were developed and sheet products were manufactured. Presented are the structure and properties of sheet metal from shipbuilding “Arc”-strength category 420 MPa.

Thin films were deposited using a vacuum arc with a refractory anode. The arc was sustained between a water cooled Zr cathode and a graphite anode. Both electrodes with diameter 32 mm and 30 mm length, with a gap of 10 mm between them. The distance from the arc axis to the substrate was 110 mm. The arc was operated either 40 or 60 s before a glass substrate was exposed to the plasma for 15 s. The film thickness was measured by profilometry. The deposition rate was obtained from the film thickness and exposition time. The visual radiation emitted by the plasma plume was photographed with a digital camera. The highest measured deposition rate was 0.71 μm/min, for an arc current of 225 A and time before exposure of 60 s.

Al-6.0Mg-0.3Sc alloy deposits are prepared by means of a double-wire arc additive manufacturing process. The formation, porosity, metallographic structure, type of precipitated phase, and mechanica...

This paper has proposed a novel design of dual PM vernier machine with T-shape consequent pole rotor. The analytical model of T-shape magnet rotor based on differential magnetic network method are firstly derived. Given the additional optimizing parameter, edge arc difference, T-shape consequent pole (TCP) rotor has the potential to produce 6% higher fundamental airgap flux density or 30% higher PM utilization ratio than regular fan-shape consequent pole rotor. The influence of magnet size parameters including magnet thickness, pole pitch ratio and arc difference angle on airgap flux density of TCP rotor is then analyzed. The torque performance of TCP in regular consequent pole and dual PM consequent pole vernier machines are also studied. The comparison shows that T-shape consequent pole can produce higher torque than fan-shape magnet in vernier machines. At last, a prototype of dual-PM vernier machine with TCP rotor is built and tested, which has achieved 28 Nm/L measured torque density.

Series Arc Faults (SAFs) are the most common faults in photovoltaic systems. If a SAF is not detected in time, it may lead to some catastrophic damages to the system. This paper presents a new method for detecting SAFs in photovoltaic systems based on determinism in the voltage signal. The determinism of the signal is derived using the recurrence plots method. The recurrence plots provide a two-dimensional plot of the signal, from which the degree of determinism in the signal is derived as a criterion for detection of SAFs. The performance of the method is evaluated using plenty of experiments carried out in different SAF and normal conditions. The results confirm the high accuracy, high speed, and low computational burden of the proposed method.

The paper presents the results of experimental registrations and numerical simulations of the transient overvoltages caused by single phase intermittent arc earth fault in 35 kV network with isolated neutral. Experimental laboratory investigation is performed in order to implement appropriate arc fault model for arcs with low and discontinuous current. Single phase to earth arc fault is created in field in 35 kV network. Numerical model of the system is created in EMTP-ATP software. Overvoltage waveshapes and overvoltage factors are calculated and compared to measured values. Good agreement between the measured and calculated results is achieved.

Wire + arc additive manufacturing (WAAM) is an arc welding process that uses non-consumable tungsten electrodes to produce the weld. The material used in this study is a titanium, carbon, zirconium, and molybdenum (TZM) alloy that is physically and chemically stable and has good performance for use as a welding and high-temperature heating element. However, the price is higher than that of other materials. Because welding cannot be modified after manufacturing, economic losses are high in the case of a defective product. Therefore, it is important to find the best welding settings for the target bead geometry during welding. In this study, welding experiments are designed based on a central composite design, and single-layer WAAM is performed using a TZM material. Consequently, we obtain 17 beads and measure the height, width, as well as left and right toe angles, which represent the geometry of the beads. Based on the measured geometry, we obtain the optimal settings for the WAAM parameters whereat the mean of each geometry is close to its target value and its variance is minimized by using a desirability function method. Furthermore, we conduct additional experiments to validate the optimal settings that we obtain. We compare the predicted and actual geometry values and find that they are quite close. This result indicates that valid optimal settings for the process parameters can be obtained via the proposed method.

With the increase of urban power grid scale, the requirement of power supply reliability has been improved, and the active intervention type arc extinguishing device (AIT-AED) has been paid more and more attention to. As one of the effective means of grounding fault arc extinguishing, the AIT-AED has a high demand on the operation reliability, but the operation experience of AIT-AED is insufficient. Hence, the pilot application of this device was carried out and its operation situations were investigated in this paper. It is found that the setting value, control logic, accessories quality and artificial operation are the main influencing factors of operation reliability and the corresponding improved measures were proposed, which could provide references for the operation and maintenance of AIT-AED.

Emission spectroscopy was conducted in a miniature arc heater in China Aerodynamics Research and Development Center to study the erosion of water-cooled copper electrode due to the high-temperature...

One important aspect in capacitor switching concerns the high inrush current during the energizing of the capacitor. One peculiarity of capacitor switching is the high rate of switching operations easily achieving 1000 operations. Two vacuum breakers were operated up to 1000 times in a simple test circuit simulating the making of high inrush currents. According to standards, peak and frequency of inrush currents are 20 kA and 4200 Hz for back-to-back switching. The range of inrush currents was extended here to peak currents up to 60 kA and frequencies up to 24 kHz. Peak current and frequency have an important impact on radius and current density of the associated arc, and thus on the energy deposited under the arc roots. Under the conditions prevailing here, the whole surface of the contacts appear uniformly melted to a depth of less than 1 mm after 1000 operations. It is obvious that the arc moves across the contact surface driven by the radial magnetic forces generated by this kind of contact. It seems that high peak inrush currents in combination with high inrush frequencies melt the contact surfaces more severe than inrush currents with lower frequencies.

In electrified railways, pantograph-catenary (PC) arc frequently occurs in the process of train passing through split-zone insulator, which threatens the current collection of PC and operation of electric multiple units (EMUs). So far, there has been few studies on the analysis and modeling of the PC arc on split-zone insulator. It is noting that this research is different from that of split-phase region. This paper firstly analyzes the dynamic variation process of PC distance as EMUs pass the insulator, and deduces the formula which can reflect the PC arc length variation according to the specific mechanical structure of insulator. Then, a black-box arc model of split-zone insulator is proposed. Next, a vehicle-grid model of the EMUs which contains the arc model of split-zone insulator is established to simulate and analyze the characteristics of the PC arc on split-zone insulator. Further, the proposed arc model in this paper is verified by comparing the simulated arc characteristic waveforms with the measured results. Finally, a sensitivity analysis of the arc model under different lifting angles of the contact wire is carried out in order to analyze the suppression of PC arc on split-zone insulator.

The aim of the present paper is to make conclusions about behaviour of the water-vortex stabilized plasma torch under different regimes of operation and radiation models involved. For this purpose we calculated steady states of such arc for the currents 300-600 A assuming two different radiation models, and several radial positions of the phase transition between water and vapour in the discharge chamber which cannot be measured in experiments. Deviations from local thermodynamic equilibrium (LTE) within the arc column are estimated due to the criteria for kinetic equilibrium and space temperature gradients. key words: arc, discharge, mass flow rate, equation, term.

This paper deals with driving effective DC series arc models from the original Nottingham arc model. The original Nottingham arc model has three constant parameters and suffers significant inaccuracy for modeling the series arc faults. To avoid the inaccuracy in the modeling, at first, a Nottingham model is developed that is relevant to voltage and current of the fault with three parameters including one constant model order for exponents of the current and two time-series coefficients. Also, to further improvement in the model's accuracy, a two-fold Nottingham model is proposed that is relevant to voltage and current of the fault with five parameters including two constant model orders for exponents of the current and three time-series coefficients. Finally, a full-time-variant Nottingham model is proposed that mathematically contains three time-series parameters including one time-variant model order of the current exponent. In the full-time-variant Nottingham model, the optimal parameters corresponding to each sliding window of data are utilized. In all the proposed models the arc coefficients are estimated using a new formulation using the least-squares error (LSE) technique. Verifying the effectiveness of the proposed models through actual data, the accuracy of the proposed models is compared with the original Nottingham model.

We study a shortest-path interdiction problem in which the interdictor acts first to lengthen a subset of arcs, and an evader acts second to select a shortest path across the network. In this problem, the cost for an evader’s arc consists of a base cost if the arc is not interdicted, plus an additional cost that is incurred if the arc is interdicted. The interdictor is not aware of the base costs when the interdiction action is taken, but does know that the base cost values are uniformly distributed within given (arc-specific) intervals. The evader, on the other hand, observes the exact value of the base costs, plus the additional costs due to interdiction actions. The interdictor’s problem is thus to maximize the expected minimum cost attainable by the evader. We provide a partitioning algorithm for computing an exact optimal solution to this problem, leveraging bounds gleaned from Jensen’s inequality as proposed in an earlier study on a maximum-flow interdiction problem. We also provide several algorithmic strategies for accelerating the convergence of the algorithm and demonstrate their effectiveness on randomly generated instances.

The effect of splitter plates (SP) on current interruption at medium voltage (MV) level is theoretically investigated in the framework of Mayr's arc model, which is generalized to take into account the electrode fall voltage, V_0, of the SP. The model is analytically solved in the current zero (CZ) region where the current (before CZ) and the voltage (after CZ) can be linearized with respect to time. The current turns out to be successfully interrupted if the total electrode fall voltage, N V_0, for N-1 SP plus contact electrodes, is larger than twice the transient recovery voltage, U(dU/dt) t, at the characteristic arc decay time, t=\tau, after CZ: N V_0>2(dU/dt) \tau. For N V_0

Fifty-five new Nd isotope analyses are presented for plutonic orthogneisses from the Grimsthorpe domain in the marble-rich segment of the Grenvillian Central Metasedimentary Belt (CMB) to test the back-arc aulacogen model for its origin. Nd isotope analyses from the Weslemkoon batholith, Elzevir batholith, Lingham Lake complex, and Canniff tonalite are used to probe the crustal formation age of their source rocks. Despite its concentric foliation, the Weslemkoon batholith displays a complex geochemical pattern consisting of several northeast-trending domains with older TDM ages, surrounded by juvenile crustal material. The new Nd isotope results, coupled with geochemistry for the Weslemkoon and Elzevir batholiths, depict the fragmentation of a block of old crust that formed a screen between en echelon segments of a mid-Mesoproterozoic back-arc rift zone. The isotope boundaries identified within the Weslemkoon batholith delineate magma pulses sampling two distinct sources, interpreted as Laurentian basement and juvenile basaltic underplate. Underplating could be attributed to slab rollback under the pre-Grenvillian continental margin arc. The intensification of rift-related magmatism in the CMB is demonstrated by its bimodal petrological character. A modern analogue for the tectonic context of the CMB is the Gulf of California, where subduction-related magmatism has transitioned to rift-related magmatism. However, the Gulf of California exhibits more transcurrent motion than is evidenced by the geometry of the CMB rift. A geometrical analogue for the break-up of the Elzevir block between two rift segments is provided by the Danakil block of the Red Sea, which is currently undergoing similar tectonic fragmentation.

In this paper, novel neutral reactor structures are proposed to mitigate the secondary arc current (SAC) in non-conventional Multi-circuit Multi-voltage Transmission lines (MCMVTLs). The parameters of the reactors in the structure are optimized using the Non-dominated Sorting Genetic Algorithm II (NSGA-II). The optimization algorithm, coded in Python, regulates the multiple runs of an Electromagnetic Transients (EMT) simulation program to minimize the secondary arc current. The optimization trials are run in parallel on a 64 core computer to minimize the solution time. A detailed arc model was tested on the EMT program (PSCAD). Using this model and optimized parameters in the proposed neutral reactor schemes, the SAC is indeed extinguished in acceptable times. The SAC and TRV for neutral reactors with optimized parameters are up-to 68 and 77%, respectively, lower than the ones with parameters calculated by the conventional approach which ignores inter-circuit coupling. Meanwhile, the extinction times are up-to 46% faster. As a result, single-phase auto-reclosing in MCMVTLs is viable.

In this paper, a passive muzzle arc control device (PMACD) of the augmented railguns is studied. By discussing its performance at different numbers of extra rails, a parameter optimization model is proposed. Through the calculation model, it is found that the PMACD works well in the simple railgun, which refers to the gun that there is only one pair of rails in the inner bore. The PMACD may decrease the simple railgun’s armature peak current and muzzle arc, but affect its muzzle velocity not much. However, in the augmented railguns it has different characteristics. If the parameters of the PMACD are not selected suitable. It may increase the armature peak current and muzzle arc, but greatly decrease the velocity. The reason for this problem is that the extra rails generate a strong magnetic field in front of the armature, which induces a large current to change the armature current. It is also found that when the resistance and inductance parameters of the PMACD satisfy with the optimization formula, the PMACD can also play a good role in arc suppression in the augmented railguns. Experiments of an augmented railgun with a stainless steel PMACD are carried out to verify this optimization method. Results show that the muzzle arc is obviously controlled. This work may provide a reference for the design of the muzzle arc control device.

This paper studies the temperature field, dynamic strain and forming accuracy of the Oscillate-WAAM conical shell in the forming process and manufactures the WAAM conical shell part. The results show that compared with the offset filling WAAM, the oscillate-WAAM conical shell shows the following characteristics：the temperature difference value between the inner and outer walls of the shell is significantly reduced, the cooling rate doubled decreased, the interlayer temperature is above 300°C, as well as the average temperature gradient, the dynamic strain stability value and deformation are reduced by about 50%. Under the same process parameters, the travel speed of Oscillate-WAAM is low, which increased the heat input large and the interlayer temperature high. Meanwhile, the molten pool of Oscillate-WAAM is in consistent with the width of the shell. The molten pool simultaneous solidifying changes the stress state of printed shell form three-dimensional to two-dimensional. All above are conductive to stress release, and reduce the strain and deformation of components. The bimetallic rocket motor shell composed of HS600 and HS950 is manufactured by oscillate-WAAM. The section roundness of the shell is 0.31mm and the overall forming accuracy is ±0.625mm. The deposited metal in HS600 part of conical shell is composed of pearlite and pro-eutectoid ferrite. While the deposited metal of HS950 is composed of pearlite, acicular ferrite and bainite. The forming accuracy and mechanical properties of conical shell formed by Oscillate-WAAM meet the requirements.

The dynamic characteristics of droplet transfer is extremely complicated with the combined effects of gravity force and weaving motion during the weaving vertical-up welding on thick plate. In this paper, we firstly observed the droplet transfer behavior under various weaving parameters with high-speed photography and electrical signals during pulsed gas metal arc welding (P-GMAW). Then we investigated the influences of different weaving parameters on the arc shape and molten pool as well as droplet characteristics. By establishing a novel weaving-force model based on static-force balance theory (SFBT), we further revealed the drop transfer mechanism in weaving P-GMAW process. Extensive experimental results demonstrated that the suitable weaving parameters could effectively improve the droplet transfer stability and suppress welding defects including incomplete root penetration and lack of sidewall fusion. The findings of this paper will provide a basis for enhancing the welding process stability and obtaining a high-quality weld joint.

Industrial development continues to present challenges for manufacturers. One of them is additive manufacturing (AM) with metallic materials. One promising solution is wire arc additive manufacturing (WAAM). Currently, WAAM is a more promising tool for developers, firstly due to the simplicity of its realization and secondly for its cost-effectiveness. Building materials are represented by welding wires, so the deposition rate is favorable. A pulse power source is commonly used in this scheme of realization. Much less attention has been paid to the optimization of the power source working regime, i.e., welding mode. Indeed, the power determines the whole process of WAAM. Therefore, in the present work, an attempt has been made to perform a scientifically based design for the optimal welding mode. The austenitic welding wire was chosen to eliminate phase-transition effects in the solid state of the deposited metal. As a result of the investigation, the advantages of the designed welding mode for WAAM application are made clear. Successful efforts have been made to optimize welding modes for WAAM applications. This study is important for manufacturers as well as engineers and scientists.

Network flow formulations are among the most successful tools to solve optimization problems. Such formulations correspond to determining an optimal flow in a network. One particular class of network flow formulations is the arc flow, where variables represent flows on individual arcs of the network. For N P -hard problems, polynomial-sized arc flow models typically provide weak linear relaxations and may have too much symmetry to be efficient in practice. Instead, arc flow models with a pseudo-polynomial size usually provide strong relaxations and are efficient in practice. The interest in pseudo-polynomial arc flow formulations has grown considerably in the last twenty years, in which they have been used to solve many open instances of hard problems. A remarkable advantage of pseudo-polynomial arc flow models is the possibility to solve practical-sized instances directly by a Mixed Integer Linear Programming solver, avoiding the implementation of complex methods based on column generation. In this survey, we present theoretical foundations of pseudo-polynomial arc flow formulations, by showing a relation between their network and Dynamic Programming (DP). This relation allows a better understanding of the strength of these formulations, through a link with models obtained by Dantzig-Wolfe decomposition. The relation with DP also allows a new perspective to relate state-space relaxation methods for DP with arc flow models. We also present a dual point of view to contrast the linear relaxation of arc flow models with that of models based on paths and cycles. To conclude, we review the main solution methods and applications of arc flow models based on DP in several domains such as cutting, packing, scheduling, and routing.

The aim of this study was to compare the quality of dynamic wave arc (DWA) and coplanar volumetric modulated arc therapy (co-VMAT) plans for the treatment of localized prostate cancer. The planning target volume (PTV)-rectum, a section of the PTV comprising the PTV minus that of the rectum, received 78 Gy in 39 fractions as the mean dose to the PTV-rectum. The DWA and co-VMAT plans were generated for each patient using the RayStation treatment planning system for the Vero4DRT system. The PTV-rectum dose (D95%: the percent dose irradiating 95% of the volume), homogeneity index (HI), conformity index (CI), as well as doses to the bladder wall, rectum wall (V10–70 Gy: the percent volume receiving 10–70 Gy), and bilateral femoral heads of the DWA and co-VMAT plans were compared. The output monitor unit (MU) and delivery time obtained for each set of plans were also investigated. In terms of target coverage, the DWA plans provided an average D95% of 75.5 Gy, which was comparable to the co-VMAT-plan D95% of 75.2 Gy (p

A remarkable elastic anisotropy in plates of austenitic stainless steel produced by the Wire and Arc Additive Manufacturing process is recently reported. The Young’s modulus depends on the angle of orientation with respect to the material deposition direction. Here, for the first time, this anisotropy is exploited to maximize structural stiffness by simultaneously optimizing the structural design layout and the local deposition path direction for WAAM. The results obtained indicate deposition that is commonly preferred along the load-path directions for WAAM is sub-optimal and stiffness can be increased at least 53 % upon optimizing the deposition directions.

Plasma Arc Drilling (PAD) is well known non-conventional process extensively used to assemble the complex part profiles for different materials. The dimensional accuracy and surface quality like roundness, kerf tape, and heat-affected zone of PAD are precarious factors for specific applications, especially in aerospace and manufacturing industries. In present investigation has studied the influence of plasma arc drilling parameters for evaluating the quality characteristics of roundness on Ti–6Al–4 V alloy. The experimental runs were designed by the Taguchi method. The optimal PAD parameters such as arc current of 160 amp, speed of 1500 m/min, and stand-off distance of 1 mm are determined. The confirm test exhibits better agreement with the predicted values.

Subduction of oceanic lithosphere is a diagnostic characteristic of plate tectonics. However, the geodynamic processes from initiation to termination of subduction zones remain enigmatic mainly due to the scarcity of appropriate rock records. We report the first discovery of early Paleozoic boninitic blueschists and associated greenschists from the eastern Proto-Tethyan North Qilian orogenic belt, northeastern Tibet, which have geochemical affinities that are typical of forearc boninites and island arc basalts, respectively. The boninitic protoliths of the blueschists record intra-oceanic subduction initiation at ca. 492–488 Ma in the eastern North Qilian arc/forearc–backarc system, whereas peak blueschist facies metamorphism reflects subsequent subduction of the arc/forearc complex to high pressure at ca. 455 Ma. These relations therefore record the life circle of an intra-oceanic subduction zone within the northeastern Proto-Tethys Ocean. The geodynamic evolution provides an early Paleozoic analogue of the early development of the Izu–Bonin–Mariana arc and its later subduction beneath the extant Japanese arc margin. This finding highlights the important role of subduction of former upper plate island arc/forearcs in reducing the likelihood of preservation of initial subduction-related rock records in ancient orogenic belts.

Submerge arc welding is one of the most important, high-quality, and reliable joining techniques for heavy industries. In the present study, bead-on-plate welding was done via Submerge Arc process on AISI 1015 mild steel in different welding conditions, including electrode angle as well as weld direction. The weldment produced from the different parametric conditions is tested to measure the bead geometry and quality of the weldment. An optical microscope image of the weld zone reveals that the backhand with a 45° electrode angle can produce high penetration at the weld zone. Whereas, welding performed with a 90° electrode angle results in a defect-free weld zone.

AC series arc is dangerous and can cause serious electric fire hazards and property damage. This article proposed a convolutional neural network -based arc detection model named ArcNet. The database of this research is collected from eight different types of loads according to IEC62606 standard. The two most common types of arcs, including arcs from a loose connection of cables and those caused by the failure of the insulation, are generated in testing and included in the database. Using the database of raw current, experimental results indicate ArcNet can achieve a maximum of 99.47% arc detection accuracy at 10 kHz sampling rate. The model is also implemented in Raspberry Pi 3B for classification accuracy. A tradeoff study between the arc detection accuracy and model runtime has been conducted. The proposed ArcNet obtained an average runtime of 31 ms/sample of 1 cycle at 10 kHz sampling rate, which proves the feasibility of practical hardware deployment for real-time processing.

For decades it has been known that spacecraft charging-induced electrostatic arc discharge on solar arrays can cause cell degradation and damaging secondary arcs. While discharging on large-area so...

Fires caused by DC series arcs are one of the primary threats to the safety of photovoltaic (PV) systems. Accurate fault location is extremely helpful in protecting PV plants, but existing research on locating DC series arc faults is limited. This paper proposes a novel DC series arc spatial location method. The proposed method estimates the distance based on the received signal strength indicator (RSSI) of electromagnetic radiation (EMR) emitted by the arc. The experimental system uses four antennas that form a tetrahedral topology to receive arc EMR signals. Some pretests are implemented before an arc occurs to obtain some known-location arc EMR signals, which are processed to be the candidate data of the arc EMR model. When the arc fault occurs, the candidate data are selected through comparison with the unknown-location signals. The arc EMR model is set up by the Bayesian regularized neural network (BRNN) algorithm. Then, the distances between the arc and antennas are estimated by the BRNN. The spatial coordinates are calculated with the antenna array topology and estimated distances. Finally, the verification results show that the algorithm has a 0.5 m average spatial location error, which is proven to be active and feasible.

Low processing efficiency and environmental pollution hinder the development of electrical discharge machining (EDM). To address this issue, a sustainable and efficient EDM method under compound field, namely rotating short arc milling, is proposed in this study. The magnetic field and high-pressure flow field of dielectric facilitate the removal of debris from discharge gap. Tap water is used as the dielectric to reduce pollutants generated during processing. Under the compound field, a portion of debris adheres to the machining end of the tool electrode to form a protective layer and participates in the discharge machining as a part of the tool electrode, which can reduce the tool electrode wear. This study describes the principles of this method to achieve high material removal rate (MRR), low tool electrode wear rate (TEWR), and environmentally friendly dielectric. Besides, a series of experiments are conducted to study the motion characteristics and resistance characteristics of rotating short arc, the influence of processing parameters on the machining performance of GH4169 superalloy. The results show that the machining voltage, machining depth, and magnetic field strength are the three most important factors that affect the efficiency and sustainability of rotating short arc milling. Furthermore, the optimal processing parameter combination is obtained by using gray relational analysis method to optimize the machining process in terms of high efficiency and environmental protection.

This paper investigates the effect of slits within the arc-plug insert of the solar parabolic trough receiver (PTR). In order to predict the performance of the parabolic trough collector (PTC) with arc-plug slits within the absorber tube; two different variants of slits of 2 mm and 1 mm thicknesses are considered. Then, each of the variants of slits with different thicknesses are varied in terms of numbers of their occurrence in the arc-plug. The 2 mm thickness slits are varied in 5, 7, and 9 numbers with uniform space of separation between them in the arc-plug. While 1 mm thickness slits are varied from 11 to 13 in numbers and also maintaining uniform space of separation between them like in 2 mm thickness slits. The objective is to determine the effects of viscous dissipation within the slits of the arc-plug of PTR; and also, the optimized version of the slit with its numbers. It is found that 2 mm slits with 9 in numbers showed the highest value of thermal efficiency as compared to all other cases. The thermal efficiency (η) of the PTC with arc-plug slits are seen to be about 1.642 times of conventional PTC; whereas, 1.309 times of arc-plug without slits. Therefore, it is always beneficial to use slits within inserts of PTCs for its performance enhancement; but, the selection of slit’s thickness and its numbers plays a vital role in its application.

In order to effectively suppress the muzzle arc, an augmented electromagnetic launcher (EML) model with arc suppression has been established. Then, the model was validated by experiments with and without arc suppression. Finally, the matching between the arc suppression parameters (charging voltage, trigger delay, and installation position) and the main circuit was investigated. The results show that the electromagnetic force formed by the arc suppression circuit is the braking force before the armature passes the arc suppression installation position, and then becomes the driving force after the armature passes the arc suppression installation position. In general, the arc suppression trigger delay and the charging voltage should be reasonably matched to achieve that most of the current in the muzzle is removed by the arc suppression circuit when the armature is released. Besides, in the design of EML, the installation position of arc suppression should be fully considered in combination with its influence on arc suppression effect and muzzle velocity.

BACKGROUND: Stereotactic body radiation therapy (SBRT) for liver cancer has shown promising therapeutic effects. Effective treatment relies not only on the precise delivery provided by image-guided radiation therapy (IGRT) but also high dose gradient formed around the treatment volume to spare functional liver tissue, which is highly dependent on the beam/arc angle selection. In this study, we aim to develop a decision support model to learn human planner’s beam navigation approach for beam angle/arc angle selection for liver SBRT. METHODS: A total of 27 liver SBRT/HIGRT patients (10 IMRT, 17 VMAT/DCA) were included in this study. A dosimetric budget index was defined for each beam angle/control point considering dose penetration through the patient body and liver tissue. Optimal beam angle setting (beam angles for IMRT and start/terminal angle for VMAT/DCA) was determined by minimizing the loss function defined as the sum of total dosimetric budget index and beam span penalty function. Leave-one-out validation was exercised on all 27 cases while weighting coefficients in the loss function was tuned in nested cross validation. To compare the efficacy of the model, a model plan was generated using automatically generated beam setting while retaining the original optimization constraints in the clinical plan. Model plan was normalized to the same planning target volume (PTV) V100% as the clinical plans. Dosimetric endpoints including PTV D98%, D2%, liver V20Gy and total MU were compared between two plan groups. Wilcoxon Signed-Rank test was performed with the null hypothesis being that no difference exists between two plan groups. RESULTS: Beam setting prediction was instantaneous. Mean PTV D98% was 91.3% and 91.3% (P=0.566), while mean PTV D2% was 107.9% and 108.1% (P=0.164) for clinical plan and model plan respectively. Liver V20Gy showed no significant difference (P=0.590) with 23.3% for clinical plan and 23.4% for the model plan. Total MU is comparable (P=0.256) between the clinical plan (avg. 2,389.6) and model plan (avg. 2,319.6). CONCLUSIONS: The evidence driven beam setting model yielded similar plan quality as hand-crafted clinical plan. It is capable of capturing human’s knowledge in beam selection decision making. This model could facilitate decision making for beam angle selection while eliminating lengthy trial-and-error process of adjusting beam setting during liver SBRT treatment planning.

Electrode current plays a significant role in control of submerged arc furnaces. However, it is difficult to measure the values directly. Recent studies have expanded the available information on current distribution of submerged arc furnaces, thus enabling the soft-sensing model for submerged arc furnace electrode current to be constructed. The present study aimed to establish a soft-sensing model for submerged arc furnace electrode current. The study consisted of the establishment of the mechanism model, identification of the mechanism model parameters, compensation of the mechanism model errors, and update of the soft-sensing model. The main conditions considered in the mechanism model include operating resistance, short network resistance and inductance, and electrode depth. The innovation of this study is that a dual particle swarm optimization algorithm with information exchange is proposed to ensure the speed and accuracy of mechanism model parameter identification. The experimental results demonstrate that the soft-sensing model can predict the electrode current with high accuracy. Compared with the traditional method using the transformation ratio of the transformer and the primary current, the prediction accuracy of the electrode current is improved by about 12 pct. The model update strategy can improve the adaptability of the model.

The rare-earth metal Gd plays an important role in the energy, information, and national defence fields due to its special optical, electrical, magnetic, and catalytic properties. In this study, Gd was purified by direct current (DC) arc plasma, and Gd2O3 nanoparticles were prepared via an integration method using purified Gd. The effects of arc current, melting time, gas pressure, and atmosphere on the purification of Gd by DC arc plasma were investigated. With an increase in the arc current and melting time, the rate of removal of impurities from Gd enhances. Moreover, Gd melting was conducted by H2–Ar arc plasma, which improves the impurity removal rate by increasing the H2 content. High thermal conductivity and chemical activity of the activated H atoms generated by the dissociation of H2 are the main reasons for the significant improvement in the impurity removal rate. The mechanism of Gd purification was analysed based on the above-mentioned experimental results. The as-synthesised Gd2O3 nanoparticles have a uniform spherical structure (average diameter of 32.7 nm), appropriate dispersibility, and high purity. This study provides a new strategy for the integrated purification of metals and preparation of metal/metal-based nanomaterials by DC arc plasma.

Based on our novel dc vacuum interruption technology under composite transverse magnetic fields (TMFs), the arc voltage of dc vacuum arc can be effectively improved to interrupt the dc current. The objective of this work is to experimentally investigate the vacuum arc characteristics and their evolution in dc current interruption under composite TMFs. The composite TMFs were generated by both multipole permanent magnets and cup-type TMF contacts. The vacuum arc photos were recorded by a high-speed camera. The experimental results indicate that under these composite TMFs, the dc current could be successfully interrupted, which was closely related to the dc vacuum arc characteristics and their evolution. The experimental dc current and voltage were less than 500 A and 500 V. First, the evolution of the dc vacuum arc could be divided into Stable and Unstable stages, according to the characteristics of the arc voltage waveform. In the Stable stage, the dc vacuum arc might be stagnated, constricted, and rotated with a stable arc voltage of 20 V. In the Unstable stage, the dc vacuum arc was transferred to the outer periphery of the contact in the form of a ``C''-shape, and the arc voltage significantly increased higher than the supply dc voltage. Second, there was an Extinction Area in the middle of Area 4 under the composite TMFs, which made the dc vacuum arc always extinguish at this position. Third, repeated fluctuations of the arc voltage are caused by the formation and extinction of the ``C''-shaped arc. Finally, when the distance between the igniting area and Extinction Area increased, the duration of the Stable stage increased, while the duration of the Unstable stage decreased.

Residual stresses are inherent stresses that exist in engineering components even though no external load is applied. They are caused by the non-uniform volumetric shift of the metallic component during manufacturing processes. Welding is a key manufacturing technique that has a substantial impact on the economy since it is required for the production of a diverse variety of products used in the engineering sector. The residual stress primarily affects the stability, durability and performance of the welded joints. Hence its determination is of utmost importance. X-ray diffraction (XRD) is the most commonly used method for residual stress analysis. There are mainly two approaches for measuring residual stress using XRD; one is the sin2ψ method and the other is the cosα method. The residual stress measurements using the cosα method are handy, quick and convenient compared to the sin2ψ method. This method is well suited for welded joints, as it provides flexibility for testing immediately after the welding operation. Apart from residual stress measurements, the cosα method also gives valuable insights in the form of Debye-Scherrer (DS) rings and full width at half maximum. The present study focuses on the development of a novel technique that not only enables residual stress measurement but also provides a quantitative estimation of hardness and qualitative estimation of grain size without performing metallurgical or mechanical characterization. The material used for the present study is an arc-welded joint of MDN 250 grade maraging steel. The residual stress results show a compressive profile throughout the weldment, with a maximum value of compressive residual stress of 428 MPa at the fusion zone.