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This work presents the control strategies for the configuration involving an open-end winding induction motor (OW-IM) fed by dual two-level inverters, which can realize the controllable power sharing between two isolated power sources without using the DC/DC converter. Based on the mathematical model of the OW-IM and the principles of the voltage vector distribution, two rotor flux calculation algorithms, namely the motor loss minimization (MLM) algorithm and the maximum power sharing capability (MPSC) algorithm are proposed and compared, with their selection strategy to select the suitable algorithm depending on the operating condition. The MLM algorithm has the optimal efficiency performance, while the MPSC algorithm can maximize the power sharing capability of the dual inverter while holding the widest operation range of the motor. Based on the dual space vector pulse-width modulation (SVPWM) control scheme, the golden section (GS) search method is introduced to allocate the stator voltage vector to the dual inverter for the power sharing demand, with a flexible iteration number to obtain a stable and efficient computational performance, which fully utilizes the power sharing capability via the voltage vector distribution. Simulation results prove the validity and the advantages of the proposed strategy. This system also lays a foundation for energy management function of the dual-power electric vehicles.

A dual inverter feeding an open-end winding permanent magnet synchronous motor drive system can realize controllable power sharing or power flow between two independent power sources without a dc/dc converter. The two power sources can be selected among many options, such as fuel cells, engine generators, batteries, and supercapacitors. In this paper, the dual inverter's voltage vector distribution and power flow principles are discussed. Based on the analyses of the overlapping area of the two inverters' modulation ranges, the dual inverter's modulation capability is exploited sufficiently. A novel voltage vector distribution strategy is proposed based on a dual space vector pulse-width modulation control scheme, which is composed of four patterns using basic voltage vectors, single-saturated vectors, double-saturated vectors, and linear-saturated vectors, respectively. By selecting the most suitable pattern, the power-sharing demand can be met in its maximum range while the switching frequencies of the two inverters are lowered and well-balanced. Simulation results confirm the validity and the advantages of the proposed strategy and clarify the power-sharing range in the entire operating range of the motor. This system also provides a scheme for energy management in electric vehicle applications.

For the inelastic electron scattering of atoms and molecules, a consensus has been reached that the first Born approximation is easily approached by decreasing the momentum transfer at the same impact electron energy or increasing the impact electron energy at the same momentum transfer. Although this consensus is applicable for the elastic electron scattering of most atoms and molecules, it is violated for helium where the experimental differential cross sections deviate from the first Born approximation prediction gradually with the decrease of squared momentum transfer at the same impact electron energy. Since this anomalous phenomenon was observed more than 40 years ago, the intrinsic mechanism is not explicit. In the present work, using the high-resolution x-ray scattering, we isolate the scattering contribution from the nucleus and directly obtain the pure electronic structure of helium. Then, the anomalous asymptotic behavior of the elastic electron scattering of helium has been elucidated, i.e., in the small squared momentum transfer region, the scattering contribution from the target's electrons is counteracted by the one from the atomic nucleus, which results in the residual contribution beyond the first Born approximation being drastically enlarged. [ABSTRACT FROM AUTHOR]

A drive system with an open-end winding permanent magnet synchronous motor (OW-PMSM) fed by a dual inverter and powered by two independent power sources is suitable for electric vehicles. By using an energy conversion device as primary power source and an energy storage element as secondary power source, this configuration can not only lower the DC-bus voltage and extend the driving range, but also handle the power sharing between two power sources without a DC/DC (direct current to direct current) converter. Based on a drive system model with voltage vector distribution, this paper proposes a desired power sharing calculation method and three different voltage vector distribution methods. By their selection strategy the optimal voltage vector distribution method can be selected according to the operating conditions. On the basis of the integral synthesizing of the desired voltage vector, the proposed voltage vector distribution method can reduce the inverter switching frequency while making the primary power source follow its desired output power. Simulation results confirm the validity of the proposed methods, which improve the primary power source’s energy efficiency by regulating its output power and lessen inverter switching loss by reducing the switching frequency. This system also provides an approach to the energy management function of electric vehicles.

The magnetic coupling between two permalloy layers with a Cr separating layer was studied using LMOKE, polarized neutron reflectivity and XRD. The coupling between two permalloy layers is antiferromagnetic-like when the Cr thickness is near 2.0 nm along the easy axis. A strong biquadratic coupling term has been found from the polarized neutron reflectivity study. The strong biquadratic coupling may be caused by the rough interface between the permalloy and Cr layers. The missing GMR effect of this system might be due to this strong biquadratic coupling of permalloy layers. [Copyright &y& Elsevier]

Explores the capability of energy dispersive small angle x-ray scattering with synchrotron radiation. Use of a detector mask with three acceptance rings of different ring radius; Signal to background ratio for a standard cross-linked polyethylene sample; Limitation of the application at low energy by sample transmission and detector response.

Studies a segmented cascade ion chamber for measuring the intensities and energies of synchrotron radiation x-rays. Cathode cells comprising the chamber; Measurement of ionized current collected in each cell; Schematic view of the chamber.

We report a systematic investigation on the structural and electronic effects of carbon-supported Pt(x)Pd(1-x) bimetallic nanoparticles on the oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) in acid electrolyte. Pt(x)Pd(1-x)/C nanocatalysts with various Pt/Pd atomic ratios (x=0.25, 0.5, and 0.75) were synthesized by using a borohydride-reduction method. Rotating-disk electrode measurements revealed that the Pt(3)Pd(1)/C nanocatalyst has a synergistic effect on the ORR, showing 50% enhancement, and an antagonistic effect on the MOR, showing 90% reduction, relative to JM 20 Pt/C on a mass basis. The extent of alloying and Pt d-band vacancies of the Pt(x)Pd(1-x)/C nanocatalysts were explored by extended X-ray absorption fine-structure spectroscopy (EXAFS) and X-ray absorption near-edge structure spectroscopy (XANES). The structure-activity relationship indicates that ORR activity and methanol tolerance of the nanocatalysts strongly depend on their extent of alloying and d-band vacancies. The optimal composition for enhanced ORR activity is Pt(3)Pd(1)/C, with high extent of alloying and low Pt d-band vacancies, owing to favorable O-O scission and inhibited formation of oxygenated intermediates. MOR activity also shows structure dependence. For example, Pt(1)Pd(3)/C with Pt(rich-core)Pd(rich-shell) structure possesses lower MOR activity than the Pt(3)Pd(1)/C nanocatalyst with random alloy structure. Herein, extent of alloying and d-band vacancies reveal new insights into the synergistic and antagonistic effects of the Pt(x)Pd(1-x)/C nanocatalysts on surface reactivity.

At the National Synchrotron Radiation Research Center (NSRRC), which operates a 1.5 GeV storage ring, a dedicated small-angle X-ray scattering (SAXS) beamline has been installed with an in-achromat superconducting wiggler insertion device of peak magnetic field 3.1 T. The vertical beam divergence from the X-ray source is reduced significantly by a collimating mirror. Subsequently the beam is selectively monochromated by a double Si(111) crystal monochromator with high energy resolution (DeltaE/E approximately 2 x 10(-4)) in the energy range 5-23 keV, or by a double Mo/B4C multilayer monochromator for 10-30 times higher flux ( approximately 10(11) photons s(-1)) in the 6-15 keV range. These two monochromators are incorporated into one rotating cradle for fast exchange. The monochromated beam is focused by a toroidal mirror with 1:1 focusing for a small beam divergence and a beam size of approximately 0.9 mm x 0.3 mm (horizontal x vertical) at the focus point located 26.5 m from the radiation source. A plane mirror installed after the toroidal mirror is selectively used to deflect the beam downwards for grazing-incidence SAXS (GISAXS) from liquid surfaces. Two online beam-position monitors separated by 8 m provide an efficient feedback control for an overall beam-position stability in the 10 microm range. The beam features measured, including the flux density, energy resolution, size and divergence, are consistent with those calculated using the ray-tracing program SHADOW. With the deflectable beam of relatively high energy resolution and high flux, the new beamline meets the requirements for a wide range of SAXS applications, including anomalous SAXS for multiphase nanoparticles (e.g. semiconductor core-shell quantum dots) and GISAXS from liquid surfaces.

The chemical state and formation mechanism of Pt-Ru nanoparticles (NPs) synthesized by using ethylene glycol (EG) as a reducing agent and their stability have been examined by in situ X-ray absorption spectroscopy (XAS) at the Pt LIII and Ru K edges. It appears that the reduction of Pt(IV) and Ru(III) precursor salts by EG is not a straightforward reaction but involves different intermediate steps. The pH control of the reaction mixture containing Pt(IV) and Ru(III) precursor salts in EG to 11 led to the reduction of Pt(IV) to Pt(II) corresponding to [PtCl4](2-) whereas Ru(III)Cl3 is changed to the [Ru(OH)6](3-) species. Refluxing the mixture containing [PtCl4](2-) and [Ru(OH)6](3-) species at 160 degrees C for 0.5 h produces Pt-Ru NPs as indicated by the presence of Pt and Ru in the first coordination shell of the respective metals. No change in XAS structural parameters is found when the reaction time is further increased, indicating that the Pt-Ru NPs formed are extremely stable and less prone to aggregation. XAS structural parameters suggest a Pt-rich core and a Ru-rich shell structure for the final Pt-Ru NPs. Due to the inherent advantages of the EG reduction method, the atomic distribution and alloying extent of Pt and Ru in the Pt-Ru NPs synthesized by the EG method are higher than those of the Pt-Ru/C NPs synthesized by a modified Watanabe method.