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Active Flux is an extension of the Finite Volume method and additionally incorporates point values located at cell boundaries. This gives rise to a globally continuous approximation of the solution. Originally, the Active Flux method emerged as a fully discrete method, and required an exact or approximate evolution operator for the point value update. For nonlinear problems such an operator is often difficult to obtain, in particular for multiple spatial dimensions. We demonstrate that a new semi-discrete Active Flux method (first described in Abgrall et al., ESAIM: Mathematical Modelling and Numerical Analysis 57:991-1027, 2023 for one space dimension) can be used to solve nonlinear hyperbolic systems in multiple dimensions without requiring evolution operators. We focus here on the compressible Euler equations of inviscid hydrodynamics and third-order accuracy. We introduce a multi-dimensional limiting strategy and demonstrate the performance of the new method on both Riemann problems and subsonic flows. [ABSTRACT FROM AUTHOR]

Permanent Magnet assisted Synchronous Reluctance Motor (PMaSynRM) is widely used in electric vehicles, aerospace and other fields with its high speed range, high cost performance and so on. To improve the rotor position estimation accuracy of active flux observer which only uses voltage model or current model in the existing sensorless control methods of PMaSynRM, this paper proposes a sensorless control method of PMaSynRM based on the hybrid of voltage model and current model. In this paper, the definition of active flux is determined according to the mathematical model of PMaSynRM, and then the active flux observer is constructed. The observer includes voltage model and current model, and the proportional integral controller is added to the observer, and the current model is used as feedback compensation to realize the stable operation of the motor without position sensor. The simulation results show that the active flux observer can realize high position observation accuracy and achieve the stable operation of the PMaSynRM in a wide speed range. The proposed method can effectively improve the system load capacity and anti-interference ability. [ABSTRACT FROM AUTHOR]

In this work we develop implicit Active Flux schemes for the scalar advection equation. At every cell interface we approximate the solution by a polynomial in time. This allows to evolve the point values using characteristics and to update the cell averages using fluxes obtained by integrating this polynomial. The resulting schemes have order of convergence up to five, but show only moderate oscillations with high frequencies for discontinuous solutions. In numerical experiments we compare the different methods and show an application to network flows. [ABSTRACT FROM AUTHOR]

Duplex Ti alloys are widely used in the petrochemical industry as well as in the biomedical, aeronautics and astronautics engineering fields. A duplex Ti alloy weldment is uniform and has superior properties in terms of welded microstructure evolution, grain refinement, and microhardness distribution. These properties are believed to be obtainable through tungsten inert gas arc welding with a combination of electrodynamic vibration and active flux. This combination changes the welded metal to phase transformation products, leading to the reappearance of numerous low-angle grain boundaries (≤5°). Vibration is presumed to disturb the heat transfer and temperature gradient in a liquid melt welding pool, enhancing the nucleation and cooling rates. The final result is the rapid formation of many basket weave-like fine parallel elongated α′ sheaths containing the β-phase in the solidified welded metal.

Active Flux is a recently developed numerical method for hyperbolic conservation laws. Its classical degrees of freedom are cell averages and point values at cell interfaces. These latter are shared between adjacent cells, leading to a globally continuous reconstruction. The update of the point values includes upwinding, but without solving a Riemann Problem. The update of the cell average requires a flux at the cell interface, which can be immediately obtained using the point values. This paper explores different extensions of Active Flux to arbitrarily high order of accuracy, while maintaining the idea of global continuity. We propose to either increase the stencil while keeping the same degrees of freedom, or to increase the number of point values, or to include higher moments as new degrees of freedom. These extensions have different properties, and reflect different views upon the relation of Active Flux to the families of Finite Volume, Finite Difference and Finite Element methods. [ABSTRACT FROM AUTHOR]

Harmonics and drifts are found in the position estimation errors of high-frequency signal injection (HFI) methods. To suppress the position estimation error, a hybrid active flux observer with disturbance rejection for both HFI method and model-based method is proposed. It fuses the position information from traditional HFI method and model-based method as the input of a disturbance observer, the estimated disturbance output can compensate measurement error for the two methods. Then a reduced-order natural speed observer is connected in a cascaded form to reject motor mechanical disturbance by estimating the load torque. Besides, a stator resistance identification algorithm is proposed, which is proved stable near zero frequency under persistent excitation condition. A tuning guideline for the whole algorithm is elaborated based on a rigorous stability analysis. Effective experiments and simulations verify the feasibility of the proposed scheme on a 0.75-kW interior permanent magnet synchronous motor drive platform. [ABSTRACT FROM AUTHOR]

In this study, we assessed the effects of K2CO3 flux on the microstructure and abrasion resistance of high-chromium alloys deposited by open arc self-shielded welding with composite powder particles (CPPs) and solid wire. A high-speed camera was used to capture the arc shape. Phase composition and microstructure of the as-prepared alloys were characterized by an x-ray diffractometer (XRD), a scanning electron microscopy (SEM) with an energy dispersive spectrometer (EDS). Abrasion resistance was investigated using wet sand rubber wheel wear tester. The results showed that the arc expanded outward and changed from a bell jar shape to a hemispherical shape with the addition of K2CO3 active fluxes. The CPP filling rate of hardfacing alloys was advanced and their microstructure changed from hypoeutectic to hypereutectic with increasing K2CO3 content. Abrasion resistance also improved significantly initially due to the appearance of primary M7C3 phases and then decreased for their grain refinement. [ABSTRACT FROM AUTHOR]

Active flux model of permanent magnet synchronous motors simplifies the model and eases sensorless control implementation. However, incorporating the current model (CM) that depends on the estimated electrical position for active flux estimation may cause performance degradation. The conventional active flux observer analysis revealed that position error influences sensorless control performance, especially during transient conditions. Thus, two improvement strategies named method-1 and method-2 are proposed in this article. Method-1 is based on an adaptive gain observer-based approach designed to discard the effect of position error. The observer gains are dependent on the estimated reference frame currents, which leads to the observer complexity. Method-2, on the other hand, uses the position error from the estimated active flux to obtain the true CM active flux without changing the conventional observer gains. Thus, the effect of position error on active flux estimation is discarded. Method-1 and method-2 fully decoupled the speed-position identification and the active flux observer. Meanwhile, a feedforward compensated phase-locked loop is adopted for speed-position identification. The proposed sensorless control strategies have been extensively validated using the Texas digital signal processor (TMS320F28335) and RT-LAB real-time simulator. The experimental results indicated that the proposed methods improved the sensorless control and active flux estimation performance. [ABSTRACT FROM AUTHOR]

This letter addresses experimental validation of the reduced-order natural speed observer design for position sensorless drive with nonsalient permanent magnet synchronous motor. The natural speed observer and the active flux estimator are connected in a cascaded fashion, which results in a simple sensorless algorithm that needs only to tune one bandwidth parameter for flux estimation and one bandwidth parameter for speed observation. Experimental results of high speed reversal test, zero speed stopping test, and slow speed reversal test are included, where the practice of applying nonzero $d$ -axis current at zero speed has shown to be effective for loaded zero speed stopping test, but it causes zero-speed locked-up at slow speed reversal with acceleration rate of $\rm \text{50}\,r/\text{min}/s$. Four remedies are compared to improve the slow speed reversal test and the proposed method gives almost ramp actual speed waveform, nondiverging $q$ -axis current and smooth transition in position waveform during slow zero speed crossing. A new dynamic expression of the active flux is proposed and with the aid of the active flux concept, the proposed sensorless algorithm is also applicable to various types of ac motors. [ABSTRACT FROM AUTHOR]

In this article, a new frequency adaptive second-order disturbance observer (FASODO) for back electromotive force (EMF) and active flux estimation is proposed using the active flux model of interior permanent magnet synchronous motors. FASODO is a frequency adaptive approach and eliminates the phase delay compensator demand of the traditional sliding mode observer-based back EMF estimator. Besides, FASODO estimates the active flux and the back EMF simultaneously. As a result, a quadrature phase-locked loop (Q-PLL) using either the back EMF or the active flux and a tan inverse approach can be used for speed–position identification. Meanwhile, an integrally compensated Q-PLL is designed to overcome the traditional Q-PLL position estimation error during ramp frequency tracking. The design guideline of FASODO and the integrally compensated Q-PLL are provided. A comparative analysis with traditional SMO shows that the proposed approach can deliver a better sensorless control performance. Furthermore, a comparison with a frequency adaptive complex coefficient filter enhanced SMO shows a comparable result, while the proposed approach additionally delivers the active flux. The approach is verified using the Texas Digital Signal Processor (TMS320F28335) and RT-LAB Real-Time Simulator, taking into account different operating conditions. [ABSTRACT FROM AUTHOR]

The active flux scheme is a finite volume scheme with additional point values distributed along the cell boundary. It is third order accurate and does not require a Riemann solver: the continuous reconstruction serves as initial data for the evolution of the points values. The intercell flux is then obtained from the evolved values along the cell boundary by quadrature. This paper focuses on the conceptual extension of active flux to include source terms, and thus for simplicity assumes the homogeneous part of the equations to be linear. To a large part, the treatment of the source terms is independent of the choice of the homogeneous part of the system. Additionally, only systems are considered which admit characteristics (instead of characteristic cones). This is the case for scalar equations in any number of spatial dimensions and systems in one spatial dimension. Here, we succeed in extending the active flux method to include (possibly nonlinear) source terms while maintaining third order accuracy of the method. This requires a novel (approximate) operator for the evolution of point values and a modified update procedure of the cell average. For linear acoustics with gravity, it is shown how to achieve a well-balanced/stationarity preserving numerical method. [ABSTRACT FROM AUTHOR]

The effects of adding five active fluxes: SiO2; TiO2; Cr2O3; NaF; and CeO2 on the fibre laser welding performance of thick 304 stainless steel plates were investigated in depth. Welding samples coated with different active fluxes were tested and analysed from the following aspects: weld formation, joint microstructure, mechanical properties and elemental composition. These were then compared with the uncoated thick 304 stainless steel samples. The results demonstrated that the application of an appropriate type and thickness active flux was conducive to improving the weld formation of laser welded thick 304 stainless steel plates, increasing their penetration depth, refining their microstructure, and enhancing their mechanical properties. Of the studied fluxes, the SiO2 flux exhibited the most distinct effect of enhancing the weld surface morphology. The Cr2O3 flux was the most effective in increasing the weld penetration depth, refining the microstructure and enhancing the joint tensile strength. Besides, the hardness value of the heat affected zone (HAZ) and the weld zone (WZ) increased to the greatest extent. The TiO2 flux easily caused defects such as pore generation, resulting in the weakened tensile strength of weld; the Cr2O3 flux decreased the Cr content at the middle and bottom of the laser welds slightly. Apart from the aforementioned oxide and Cr2O3 fluxes, no other active fluxes had any significant effect on the elemental contents at the WZ. [ABSTRACT FROM AUTHOR]

Dynamic behaviors of molten pools during active laser welding of thick 304 stainless steel plates are monitored in real time by utilizing a high-speed camera system. The effects of various active fluxes on the dynamic variations of molten pools are analyzed, and the results are compared with the uncoated specimens. The research reveals that all the molten pools present periodic variations. Among them, the specimen coated with NaF active flux exhibits the shortest cycle of molten pool change, with a single cycle duration of approximately 0.5 s. The specimen coated with TiO2 active flux exhibits the longest cycle of molten pool change, and the single cycle duration is around 1.1 s. Moreover, the molten pools also show varying widths. The maximum molten pool width is found with the specimen coated with CeO2 active flux, whose value is 3.277 mm. Meanwhile, the minimum molten pool width is found with the specimen coated with NaF active flux, whose value is 1.799 mm. In addition, the coating of active fluxes also produces certain effects on molten pool stability. The specimen coated with NaF active flux presents intense emission of metal vapor during welding, drastic oscillation of the molten pool, and severe spattering of metal particles. Contrastively, the molten pool of the specimen coated with Cr2O3 active flux is rather stable. In conclusion, by selecting an appropriate active flux, the cycle of molten pool variation can be prolonged, the pool stability can be enhanced, and the occurrence of spattering and other defects can be suppressed. [ABSTRACT FROM AUTHOR]

The Active Flux scheme is a finite volume scheme with additional point values distributed along the cell boundary. It is third order accurate and does not require a Riemann solver. Instead, given a reconstruction, the initial value problem at the location of the point value is solved. The intercell flux is then obtained from the evolved values along the cell boundary by quadrature. Whereas for linear problems an exact evolution operator is available, for nonlinear problems one needs to resort to approximate evolution operators. This paper presents such approximate operators for nonlinear hyperbolic systems in one dimension and nonlinear scalar equations in multiple spatial dimensions. They are obtained by estimating the wave speeds to sufficient order of accuracy. Additionally, an entropy fix is introduced and a new limiting strategy is proposed. The abilities of the scheme are assessed on a variety of smooth and discontinuous setups. [ABSTRACT FROM AUTHOR]

In this article, a V/f control with two stabilizing loops and maximum torque per ampere (MTPA) control for spoke-PM synchronous motor drives is proposed, and experimentally compared against a sensorless field-oriented control (FOC) strategy based on active flux observer. To improve the drive dynamics, the standard V/f control is enhanced with two stabilizing loops, which provide corrections for stator voltage vector amplitude and phase. The novel voltage amplitude correction is based on MTPA method employing the magnetic energy and active flux concepts. The voltage angle correction employs the active power variation and works only in transient operations, to preserve the synchronism. The sensorless FOC, used for comparison, is based on an active flux observer which uses a PI compensator with the active flux error correction between the voltage and current models. Extensive comparative experimental results in sensorless large speed range, minimum speed being 100 rpm (0.022 p.u.), with speed reversal and quick load torque, validate the two control systems. Good close performances are obtained, FOC being more stable and less influenced by parameter variations. [ABSTRACT FROM AUTHOR]

Owing to simple implementation and excellent performance, the conventional stator flux observer based on active flux concept is considered as a competitive scheme for direct torque control system of a permanent magnet synchronous motor. However, it is constructed by a large number of motor parameters, which may vary with the operating points. This leads to weak robustness. To improve its performance, a stator flux observer with phase self-tuning is proposed as an improved version in this article. First, relationship between the stator flux observed values obtained by current and voltage models and observed error of rotor position angle is analyzed. Then, according to the aforementioned analysis, a phase self-tuning link constructed by a proportional-integral regulator is proposed to ensure that the observed coordinate system converges to the actual one even under motor parameters vary conditions. Consequently, the robustness and accuracy of the stator flux observer can be improved. Finally, the stability of the proposed phase self-tuning link is analyzed. Experimental comparison between the conventional stator flux observer based on active flux concept and the proposed improved stator flux observer has been done, and the results verify the feasibility and effectiveness of the proposed stator flux observer. [ABSTRACT FROM AUTHOR]

This article presents a mathematical framework for the design and analysis of position observers for sensorless control of synchronous reluctance machines. The approach expresses the observer error via a generalized projection vector. Moreover, the proposed framework includes an improved inductance model to account for the position error-induced inductance variations. First, the instability regions of active flux-based position observer are analytically identified and validated. Then, a novel technique, adaptive projection vector for position error estimation, is introduced, immune to instability of active flux scheme. Furthermore, the proposed technique can be augmented with a second projection vector for independent estimation of speed error, referred to as adaptive projection vector matrix for position and speed error estimation. Sensitivity analysis to parameter errors is developed. Stability and performance of proposed technique is validated on a 1 kW synchronous reluctance motor test bench. [ABSTRACT FROM AUTHOR]

A new linear regression form is derived for a flux observer and a position observer is designed. In general, the observability of the permanent-magnet synchronous motor is lost at zero speed. In this work, the proposed regressor vector contains current derivative terms in both directions (dq-axis), and it gives the chance for the model-based flux observer to operate at zero speed. When an excitation signal is injected into d and q axes with the proposed flux observer, it helps to satisfy the persistent excitation condition in the low-speed range. Therefore, the sensorless performance of the model-based is improved greatly, even at zero speed. However, it appears with a disturbance term, which depends on the derivative of the d-axis current. Thus, the disturbance does not vanish when an excitation signal is injected. In this work, the disturbance term is also taken care of in constructing an observer. It results in an observer which allows signal injection. Thus, high frequency signal can be injected in the low speed region and turned off when it is unnecessary as the speed increases. This model-based approach utilizes the signal injection directly without recurring to a separate high frequency model. In other words, it provides a seamless transition without switching to the other algorithm. The validity is demonstrated by simulation and experimental results under various load conditions near zero speed.

Quantification of the actual amount of carbon export to the mesopelagic layer by both zooplankton and micronekton is at present a gap in the knowledge of the biological pump. These organisms perform diel vertical migrations exporting carbon through respiration, excretion, mortality, and egestion during their residence at depth. The role of zooplankton in active flux is nowadays partially assessed. However, micronekton active flux is scarcely known and only a few studies addressed this downward transport. Even less is known about the capacity of both communities to export carbon in the ocean. Here, we show the results of zooplankton and micronekton active flux across a productivity gradient in the tropical and subtropical Atlantic Ocean. Biomass vertical distribution from the surface up to 800 m depth by day and night was studied during April 2015 in a transect from 9°S to 25°N, covering from the quite oligotrophic zone off Brazil to the meso- and eutrophic areas of the equator, Guinea Dome, and the oceanic upwelling off Northwest Africa. Zooplankton and micronekton migrant biomass was estimated from day and night catches at different layers of the water column using MOCNESS-1 (1 m2 mouth area) and Mesopelagos (35 m2) nets, respectively. Respiratory flux was assessed by measuring the enzymatic activity of the electron transfer system (ETS) of organisms at depth. Results showed a close relationship between migrant biomass and respiratory flux in zooplankton and micronekton as expected. Using a rather conservative 50% of efficiency for the net used to capture micronekton, respiratory flux resulted in similar values for both communities. Gravitational (passive) flux measured using sediment traps increased from the oligotrophic toward the meso- and eutrophic zones. Total active flux (including respiration and estimated mortality, excretion, and gut flux) by zooplankton and micronekton accounted for about 25% of total flux (passive plus active) in oligotrophic zones. Total active flux also increased toward meso- and eutrophic zones, reaching about 80% of total flux and being at least twofold higher than passive flux. These results alert about an important underestimation of the ocean biological pump using only passive flux measurements.

Finite volume schemes for hyperbolic conservation laws require a numerical intercell flux. In one spatial dimension the numerical flux can be successfully obtained by solving (exactly or approximately) Riemann problems that are introduced at cell interfaces. This is more challenging in multiple spatial dimensions. The active flux scheme is a finite volume scheme that considers continuous reconstructions instead. The intercell flux is obtained using additional degrees of freedom distributed along the cell boundary. For their time evolution an exact evolution operator is employed, which naturally ensures the correct direction of information propagation and provides stability. This paper presents an implementation of active flux for the acoustic equations on two-dimensional Cartesian grids and demonstrates its ability to simulate discontinuous solutions with an explicit time stepping in a stable manner. Additionally, it is shown that the active flux scheme for linear acoustics is low Mach number compliant without the need for any fix. [ABSTRACT FROM AUTHOR]

Highlights • Zooplankton vertical distribution, migrant biomass, and respiratory flux were studied. • Migrant biomass was estimated by sampling during day and night in 0–900 m depth. • The electron transfer system enzymatic activity was measured as a proxy for respiration. • Migrant biomass and the respiratory flux showed the strongest correlation. • Active flux estimated suggests a significant transport to the mesopelagic zone. [ABSTRACT FROM AUTHOR]

This paper proposes a sensorless control scheme for synchronous reluctance (SyR) motor drives based on the direct-flux vector control (DFVC) method. The control operates in stator-flux-oriented coordinates, using constant switching frequency. A hybrid position and speed observer is proposed, based on the combination of the active flux concept and high-frequency signal injection and demodulation. The two methods are fused together to form a unique position and speed estimate signals, with seamless transition between the two models based on reference speed. The proposed observer covers a wide speed range, from standstill operation at full load to flux weakening (FW). Furthermore, it is inherently immune from position estimation error caused by cross saturation, as proven mathematically and experimentally. The motor is operated according to the maximum torque per ampere (MTPA) law. Specific issues related to MTPA around zero torque are addressed in this paper. The proposed control technique extends the range of application of the DFVC to encoderless drives, and can be usefully adopted in those applications where both zero-speed and FW speed range operations are necessary, such as home appliances, or automotive and aerospace actuators and generators. A 2.2-kW SyR motor prototype was tested to verify the feasibility of the proposed method. Key tuning aspects are addressed in this paper. [ABSTRACT FROM PUBLISHER]

The scheme based on direct torque and flux control (DTFC) as well as active flux is a good choice for the interior permanent magnet synchronous motor (IPMSM) sensorless control. The precision of the stator flux observation is essential for this scheme. However, the performance of traditional observers like pure integrator and the low-pass filter (LPF) is severely deteriorated by disturbances, especially dc offset. Recently, a sliding-mode stator flux observer (SMFO) was proposed to reduce the dc offset in the estimated stator flux. However, it cannot eliminate the dc offset totally and will cause the chattering problem. To solve these problems, a novel super-twisting sliding-mode stator flux observer (STSMFO) is proposed in this paper. Compared with SMFO, STSMFO can reduce the chattering and fully eliminate the dc offset without any amplitude and phase compensation. Then, the precision of the stator flux and rotor position can be greatly improved over a wide speed region. The detailed mathematical analysis has been given for comparing it with another three traditional observers. The numerical simulations and experimental testing with an IPMSM drive platform have been implemented to verify the capability of the proposed sensorless scheme.

Abstract: Using size‐fractionated mesozooplankton biomass data collected over 23 years (1994–2016) of increasing primary production (PP) at station ALOHA (A Long‐Term Oligotrophic Habitat Assessment), we evaluate how changing environmental conditions affect mesozooplankton size structure, trophic cycling, and export fluxes in the subtropical North Pacific. From generalized additive model analysis, size structure is significantly influenced by a nonlinear relationship with sea surface temperature that is mainly driven by the strong 1997–1998 El Niño and a positive and linear relationship with PP. Increasing PP has more strongly enhanced the biomass of smaller (0.2–0.5 mm) and larger (>5 mm) mesozooplankton, increasing evenness of the biomass spectra, while animals of 2–5 mm, the major size class for vertically migrating mesozooplankton, show no long‐term trend. Measured PP is sufficient to meet feeding requirements that satisfy mesozooplankton respiration and growth rates, as determined by commonly used empirical relationships based on animal size and temperature, consistent with a tightly coupled food web with one intermediate level for protistan consumers. Estimated fecal pellet production suggests an enhanced contribution of mesozooplankton to passive particle export relative to the material collected in 150 m sediment traps. In contrast, the biomass of vertically migrants does not vary systematically with PP due to the varying responses of the different size classes. These results illustrate some complexities in understanding how varying environmental conditions can affect carbon cycling and export processes at the community level in open‐ocean oligotrophic systems, which need to be confirmed and better understood by process‐oriented mechanistic study. [ABSTRACT FROM AUTHOR]

• arbitrarily high-order accurate numerical method for conservation laws. • based on a continuous approximation of the solution. • the degrees of freedom are point values at cell interfaces and moments of the solution inside the cell. • to lowest (3rd) order this method reduces to the Active Flux method. • the update of the moments is achieved immediately by integrating the conservation law over the cell. • two ways how the point values can be updated in time. We propose an arbitrarily high-order accurate numerical method for conservation laws that is based on a continuous approximation of the solution. The degrees of freedom are point values at cell interfaces and moments of the solution inside the cell. To lowest (3 rd) order this method reduces to the Active Flux method. The update of the moments is achieved immediately by integrating the conservation law over the cell, integrating by parts and employing the continuity across cell interfaces. We propose two ways how the point values can be updated in time: either by first deriving a semi-discrete method that uses a finite-difference-type formula to approximate the spatial derivative, and integrating this method e.g. with a Runge-Kutta scheme, or by using a characteristics-based update, which is inspired by the original (fully discrete) Active Flux method. We analyze stability and accuracy of the resulting methods. [ABSTRACT FROM AUTHOR]

In this paper, stainless steel was welded by active flux-aided laser welding method. The effects of single active flux (Cr2O3, SiO2 and TiO2) and composite active flux on laser welding were studied. In the welding process, laser plasma behavior was recorded by a high-speed imaging system. The results show that, with the addition of active flux, the absorption of laser energy and melting efficiency increase. In the laser power of 750 W, effects of active flux on weld depth to width ratio are given by the order: composite active flux SiO Cr2O TiO2. The effect of composite active flux is the most significant and it can increase the weld depth to width ratio to 85%. Active flux can restrict the laser plasma. With the addition of composite active flux, the projected area of laser plasma obtained obviously reduced, and it can be reduced by 41.39%. Active flux cannot obviously change the main components in weld zone, but can change the grains of austenite and ferrite. [ABSTRACT FROM AUTHOR]

An optimal design of internal Ferrite permanent-magnet motor with embedded key finite-element method verification is presented with the scope to increase the efficiency of the small power motors without using expensive rare earth permanent magnets. Two internal flux concentration topologies are analyzed, and the geometric dimensions and performances are presented for three cases, all at 1-kW rated power at 4500 r/min rated speed. The 6/8 poles ferrite-spoke permanent-magnet synchronous motor prototype was built and test results prove an efficiency larger than 88% for a large load range. Two sensorless control methods based on active flux observer are presented, with the key simulation results including acceleration, speed reversal, loading, and unloading speed responses. [ABSTRACT FROM PUBLISHER]

The A-TIG process (TIG welding with active flux) consists in depositing a thin layer of flux on the workpiece surface just before welding. The layer deposition can be done by brushing or spraying over the surface, and welding is performed after it dries out. It is found that with this process it is possible to increase productivity (travel speed) up to three times higher compared to the conventional TIG process. However, the physical phenomena associated with this practical gain of productivity still remains under discussion. Thus, the aim of this paper is to analyse the thermal efficiency and heat input in the welding process with the A-TIG compared with conventional TIG process using a liquid nitrogen calorimeter as a contribution to better understanding the physical associated phenomena. From the presented results, it is observed that the effects of A-TIG welding on the weld bead geometry are in agreement with previous work. In addition, it is possible to conclude that the thermal efficiency of the A-TIG welding is lower than the efficiency in conventional TIG welding. Thus, it is possible to conclude that the arc constriction is more important than the reduction of thermal efficiency. [ABSTRACT FROM PUBLISHER]

This article presents a sensorless control approach of salient PMSM with an online parameter identifier. Adaptive Integrator is proposed and utilised for the estimation of active flux and rotor position. As a result, integrator overflow caused by DC offset is avoided. Meanwhile, an online stator resistance identification algorithm using strong tracking filter is employed, and the identified stator resistance is fed back to the estimating algorithm. Thus, the estimating algorithm can calculate the rotor position correctly. Simulations and experimental results validate the feasibility of both adaptive integrator and the parameter identification method. [ABSTRACT FROM PUBLISHER]

This paper deals with a current sensor fault reconstruction algorithm for the torque closed-loop drive system of an interior PMSM. First, sensor faults are equated to actuator ones by a new introduced state variable. Then, in αβ coordinates, based on the motor model with active flux linkage, a current observer is constructed with a specific sliding mode equivalent control methodology to eliminate the effects of unknown disturbances, and the phase current sensor faults are reconstructed by means of an adaptive method. Finally, an αβ axis current fault processing module is designed based on the reconstructed value. The feasibility and effectiveness of the proposed method are verified by simulation and experimental tests on the RT-LAB platform. [ABSTRACT FROM AUTHOR]

This paper presents the results of a research related to the impact of electric arc activation onto drive welding energy and metal weld heating speed. It is confirmed that activated tungsten inert gas welding and activated metal inert gas welding methods, depending on metal thickness, single pass weldability and chemical composition of activating flux, enable the reduction of welding energy by 2-6 times when compared to conventional welding methods. Additionally, these procedures create conditions to increase metal weld heating speed up to 1,500-5,500 °Cs-1. Steel which can be rapidly heated, allows for a hardened structure to form (with carbon content up to 0.4%), together with a released martensitic structure or a mixture of bainitic-martensitic structures. Results of the research of effectiveness of activated tungsten inert gas welding and activated metal inert gas welding showed that increase in the penetration capability of electric arc, which increases welding productivity, is the visible side of activated tungsten inert gas welding and activated metal inert gas welding capabilities. [ABSTRACT FROM AUTHOR]

• Migrant biomass and respiratory flux were estimated in mesopelagic organisms. • The largest migrant biomass were mesopelagic fishes followed by decapods. • Fishes showed high values of respiratory flux at the centre-eastern coast of the gulf. • Midriff Islands region had one of the highest values of crustacean respiratory flux. • Micronekton respiratory flux was higher during June than during October. The biological carbon pump is the process that transports carbon vertically out of the mixed layer in the ocean. Besides the sinking flux of organic particles, active flux due to the daily vertical migration of zooplankton and micronekton promotes a significant carbon transport not fully accounted for or understood in the world's oceans. The diversity and abundance of epipelagic and mesopelagic species in the Gulf of California has been extensively studied, but the role of micronekton in carbon export has not yet been investigated. We studied the carbon flux promoted by juvenile and adult mesopelagic fishes and crustaceans (Decapoda and Euphausiidae) during the transition from the cold to warm period (June) and the onset of the warm season (October) in 2018. We provide the first estimation of migrant biomass and respiratory flux of the most abundant migratory species of mesopelagic fishes, decapods and euphausiids in the Gulf of California. The micronekton species collected accounted for a large biomass of mesopelagic fishes and pelagic crustaceans. The average migrant biomass estimates were 151.5 ± 101.2 mg C·m−2 during June and 90.9 ± 75.3 mg C·m−2 during October. The enzymatic activity of the electron transfer system (ETS) was measured as an estimate of their respiratory rates. Average specific ETS activity was significantly different between fishes and decapods, and between fishes and euphausiids (p < 0.05). The respiratory flux of fishes was predominant in the Gulf of California, followed by pelagic decapods and euphausiids. Seasonal changes in respiratory flux were observed for fishes (June: 6.1 ± 1.5 mg C·m−2·d−1; October: 3.2 ± 1.8 mg C·m−2·d−1) and decapods (June: 0.4 mg C·m−2·d−1; October: 0.7 ± 0.05 mg C·m−2·d−1). Respiratory flux estimation by crustaceans (decapods and euphausiids) and fishes together was 6.86 mg C·m−2·d−1 during June, and 4.21 mg C·m−2·d−1 during October 2018, suggesting a functional role of this large micronektonic fauna in the biological carbon export in this region. [ABSTRACT FROM AUTHOR]

This paper proposes two thermal monitoring methods for induction machines with direct torque control (DTC). The stator resistance Rs is used as a direct indicator of average winding temperature and is estimated via a dc current offset in the stator winding. In a DTC drive system, the major challenge is how to excite the dc current offset via the only existing flux and torque control loops. The quantitative relationship between the desired dc current offset and the corresponding changes in flux linkage and torque is derived, and this shows that the dc current offset can be achieved either by superimposing flux linkage bias command [ ΔΨsα,ref ΔΨ sβ,ref ] in the flux control loop (method 1) or torque ripple command ΔTem,ref in the torque control loop (method 2), both shown in Fig. 1. Simulation results confirm the analytical analysis of the two proposed methods; while the experimental data prove that both methods achieve accurate temperature estimation under various operating conditions. The proposed simple and efficient signal-injection-based temperature estimation technique is particularly advantageous since it eliminates the need for embedded temperature sensors, requires no hardware change to conventional DTC drive systems, and has a minimal impact on the induction machine's normal operation. [ABSTRACT FROM AUTHOR]

This paper proposes an active-flux-based motion-sensorless vector-control structure for biaxial excitation generator for automobiles (BEGA) for wide speed-range operation. BEGA is a hybrid-excited synchronous machine having permanent magnets on q-axis and a dc excitation on d-axis. Using the active-flux concept, the estimated rotor position is given by the sum of the active-flux position and torque angle. The active flux is calculated by subtracting the term Lq\overline{i}s from the estimated stator-flux vector. The experimental results validate the active-flux principle and show good performance for a speed range of 50–2000 r/min. A method for initial rotor position of BEGA is proposed based on injection of a very short voltage pulse in the machine dc excitation, the method being independent of machine parameters. Experimental results for initial rotor-position estimation proved an accuracy below ten electrical degrees in less than 2-ms test time. [ABSTRACT FROM PUBLISHER]

The main advantage of the TIG with flux process (A-TIG welding) is the possibility of obtaining greater penetration of the weld bead while employing the same welding parameters as conventional TIG welding. Various studies have shown the influence of active fluxes on the geometric characteristics of stainless steel austenitic welds. However, little is known about the influence of this process on the geometric and metallurgical characteristics of the weld beads in ferritic stainless steels. In this work, different types of flux are applied when welding ferritic stainless steel with the objective of verifying possible influences on the weld bead's profile, on its visual appearance, on the microstructure, on the hardness of the welded zone and on the impact resistance (Charpy test). The bead-on-plate welds were produced without using any addition metal. Six types of flux were used - one being an oxide produced in a laboratory (TiO2) and five commercial fluxes. The results showed that use of the flux allows an increase in penetration with significant changes in the appearance of the weld bead. It was also confirmed that the microstructure and the hardness of the weld bead for the steel studied were not affected by the type of flux used, with the microstructure analysed under an optical microscope. The steel in the study showed a high degree of fragility at ambient temperature. [ABSTRACT FROM AUTHOR]

Abstract: Seasonal change in the downward carbon transport due to respiration and mortality through diel vertical migration (DVM) of the calanoid copepods Metridia pacifica and Metridia okhotensis was estimated in the Oyashio region, western subarctic Pacific during six cruises from June 2001 to June 2002. M. pacifica (C4, C5 and adult females) was an active migratory species throughout the year though its DVM amplitude varied among seasons and stages. The mean distribution depths of adult females during the daytime were positively related with the illumination level in the water column, being shallowest in April and deepest in January. M. okhotensis generally showed less-extensive migrations than M. pacifica. Therefore, together with their lower abundance, this species is considered to be a less-important mechanism of downward transport of carbon except for April when their DVM was more active and descended deeper than M. pacifica, which remained in the upper 150m even during the daytime. The mean migrating biomass of the two Metridia species was 558mgCm−2 d−1 and was high during summer to winter (263–1676mgCm−2 d−1) and low during spring (59–63mgCm−2 d−1). Total downward flux through DVM fluctuated between 1.0 and 20.0mgCm−2 d−1 with an annual mean of 8.0mgCm−2 d−1. Contribution of the respiratory flux was greater than the mortality flux and accounted for 64–98% of total migratory flux throughout the year except for January when contribution of both fluxes was equal. Overall the annual carbon transport by DVM of Metridia spp. was estimated as 3.0gCm−2 year−1, corresponding to 15% of the annual total POC flux at 150m at the study site, suggesting that DVM is a significant process for carbon export in the subarctic region as well as that in tropical and subtropical oceanic regions. Since DVM in M. pacifica is more active during the non-bloom season when the gravitational flux of particulate matter is low, this species plays an important role in driving the biological pump in the subarctic Pacific during summer to winter. [Copyright &y& Elsevier]

Rotor and stator flux orientations are now standard concepts in vector and direct torque control of ac drives. The salient-pole rotor machines, where magnetic saturation plays a key role, still pose notable problems in flux, rotor position and speed estimations for motion-sensorless control, especially in the low-speed range (below 30 rpm in general), leading to numerous dedicated state observers. This letter introduces a rather novel (or generalization) concept - active flux or torque-producing flux - and its utilization in all ac drives by employing a unified state observer for motion-sensorless control in a wide speed range. The active-flux concept turns all salient-pole traveling field machines into nonsalient-pole ones. The active-flux vector is aligned to the rotor d axis for all synchronous machines and to the rotor-flux vector axis for induction machines. This way, the rotor position and speed observer seems more amenable to a wide speed range, with smaller dynamic errors. This observer, based on the active-flux concept, is pretty much the same for all ac drives. An example of implementation for an interior permanent-magnet synchronous motor with weak permanent magnets and large magnetic saliency that compares very favorably with respect to most signal injection methods, down to 1 rpm and up to 4000 rpm, is provided through digital simulations. Experiments are under way. [ABSTRACT FROM AUTHOR]

The use of active flux in tungsten inert gas (TIG) welding is known to increase its weld depth. The present paper involves study of active flux laser beam welding (ALBW) of austenitic stainless steel sheets with respect to its effect on plasma plume, microstructure and mechanical properties of the resultant weldments. ALBW performed with SiO2 as the flux significantly modified shape of the fusion zone (FZ) to produce narrower and deeper welds. Plasma plume associated with the process was considerably smaller and of lower intensity than that produced during bead on plate laser beam welding (LBW). Flux addition during LBW produced thin and rough weld bead associated with humping. The development of such a weld bead is cause by reversal in the direction of Marangoni flow by oxygen induced inversion of surface tension gradient, widely fluctuating plasma plume and presence of oxides on the weld pool surface preventing free flow of the melt. Active flux laser weldments exhibited lower ductility than that of bead on plate laser weldments. [ABSTRACT FROM AUTHOR]

Diel vertical migration of zooplankton profoundly impacts the transport of nutrients and carbon through the water column. Despite the acknowledged importance of this active flux to ocean biogeochemistry, these contributions remain poorly constrained, in part because daily variations in metabolic rates are not considered or are modeled as simple functions of temperature. To address this uncertainty, we sampled the subtropical copepod Pleuromamma xiphias at 4- to 7-h intervals throughout the daily migration and measured rates of oxygen consumption, ammonium excretion, fecal pellet production and metabolic enzyme activity. No significant patterns were detected in rates of oxygen consumption or ammonium excretion for freshly caught animals over the diel cycle. Fecal pellet production was highest during mid-night, consistent with several hours of feeding near the surface. Surface feeding resulted in fecal pellet production at depth in the morning, providing direct evidence that active flux of particulate organic carbon occurs in this region. Electron transport system activity was highest during the afternoon, contrary to our prediction of reduced daytime metabolism. Activity of both glutamate dehydrogenase and citrate synthase increased during early night, reflecting higher capacity for excretion and aerobic respiration, respectively. Overall, these results show that activities of metabolic enzymes vary during diel vertical migration. The surprising observation of elevated afternoon enzyme activity coupled with daytime fecal pellet and ammonium production suggests that additional characterization of the daytime activity of migratory zooplankton is warranted. • Glutamate dehydrogenase and citrate synthase were elevated during early night. • Electron transport system was elevated during afternoon. • Oxygen consumption rate and ammonium excretion showed no significant pattern. [ABSTRACT FROM AUTHOR]

A new linear regression form is derived for a flux observer and a position observer is designed. In general, the observability of the permanent-magnet synchronous motor is lost at zero speed. In this work, the proposed regressor vector contains current derivative terms in both directions ( d q -axis), and it gives the chance for the model-based flux observer to operate at zero speed. When an excitation signal is injected into d and q axes with the proposed flux observer, it helps to satisfy the persistent excitation condition in the low-speed range. Therefore, the sensorless performance of the model-based is improved greatly, even at zero speed. However, it appears with a disturbance term, which depends on the derivative of the d-axis current. Thus, the disturbance does not vanish when an excitation signal is injected. In this work, the disturbance term is also taken care of in constructing an observer. It results in an observer which allows signal injection. Thus, high frequency signal can be injected in the low speed region and turned off when it is unnecessary as the speed increases. This model-based approach utilizes the signal injection directly without recurring to a separate high frequency model. In other words, it provides a seamless transition without switching to the other algorithm. The validity is demonstrated by simulation and experimental results under various load conditions near zero speed. [ABSTRACT FROM AUTHOR]