This paper presents a systematic evaluation approach of three-phase pulsewidth-modulated (PWM) AC-AC converter topologies for high-density applications. All major components and subsystems in a ...converter are considered and the interdependence of all the constraints and design parameters is systematically studied. The key design parameters, including switching frequency, modulation scheme, and passive values, are selected by considering their impacts on loss, harmonics, electromagnetic interference (EMI), control dynamics and stability, and protection. The component selection criteria as well as the physical design procedures are developed from the high-density standpoint. The concept of using the same inductor for harmonic suppression and EMI filtering is introduced in the design. With the proposed methodology, four converter topologies, a back-to-back voltage source converter (BTB-VSC), a nonregenerative three-level boost (Vienna-type) rectifier plus voltage source inverter (NTR-VSI), a back-to-back current source converter (BTB-CSC), and a 12-switch matrix converter, are analyzed and compared for high specific power using SiC devices. The evaluation results show that with the conditions specified in this paper, BTB-VSC and NTR-VSI have considerably lower loss, resulting in higher specific power than BTB-CSC and the matrix converter. The proposed methodology can be applied to other topologies with different comparison metrics and can be a useful tool for high-density topology selection.
In order to take full advantage of SiC, a high-temperature wirebond package for multichip phase-leg power module using SiC devices was designed, developed, fabricated, and tested. The details of the ...material comparison and selection are described, thus culminating a feasible solution for high-temperature operation. A thermal cycling test with large temperature excursion (from -55°C to 250°C) was carried out to evaluate the thermomechanical reliability of the package. During the test, the substrate failed before other parts in 20 cycles. A sealing edge approach was proposed to improve the thermal reliability of the substrate. With the strengthening of the sealing material, the substrate, die-attachment, and wirebond assemblies exhibited satisfactoriness in the thermomechanical reliability tests. In order to evaluate the high-temperature operation ability of designed package, one prototype module was designed and fabricated. The high-temperature continuous power test shows that the package presented in this paper can perform well at 250°C junction temperature.
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► LaCr0.5M0.5O3 (M=Cr3+, Cu2+ and Fe3+) was synthesized by simple sol–gel technique with subsequent heat treatment. ► The compound formation temperature was optimized through XRD ...analysis. ► The effects of Cu2+ and Fe3+ on the electrical properties of LaCrO3 were studied using impedance spectroscopy. ► The temperature dependence of electrical conductivity was discussed for LaCr0.5Cu0.5O3. ► The magnetization was found to be enhanced in the LaCr0.5Fe0.5O3.
The structural, electrical and magnetic properties of LaCr0.5M0.5O3 (M=Cr3+, Cu2+ and Fe3+) synthesized by a sol–gel technique were studied. The X-ray diffraction pattern shows the structure to be orthorhombic and the size of the particles is around 100nm as seen from the TEM images. The effects of Cu2+ and Fe3+ on the electrical properties of LaCrO3 were studied using impedance spectroscopy at room temperature (RT). The properties of LaCr0.5Cu0.5O3 were studied over a wide range of temperature from RT to 533K. A maximum conductivity of 1.7×10−3Scm−1 was observed for LaCr0.5Cu0.5O3 at a measured temperature of 533K. The impedance spectra indicate a negative temperature coefficient of resistance (NTCR) and also imply the conduction is through bulk of the material. The magnetic studies performed using a SQUID magnetometer interpret the antiferromagnetically ordered LaCrO3 to behave ferromagnetically on the addition of Cu2+ and Fe3+, and the magnetization was found to be enhanced in the LaCr0.5Fe0.5O3.
In this report the fabrication and characterization of different amorphous and nanocrystalline films with special respect to a possible integration into standard semiconductor processes is described. ...The prepared amorphous FeCoBSi films exhibit excellent high frequencies properties. However, their implementation in established fabrication processes is restricted, since the films start to crystallize at higher annealing temperatures. Soft nanocrystalline films, like FeTaN, are able to overcome this temperature limitation because of their better thermal stability.
Introduction
Enhanced recovery after surgery (ERAS) programs provide a format for multidisciplinary care and has been shown to predictably improve short term outcomes associated with surgical ...procedures. Esophagectomy has historically been associated with significant levels of morbidity and mortality and as a result routine application and audit of ERAS guidelines specifically designed for esophageal resection has significant potential to improve outcomes associated with this complex procedure.
Methods
A team of international experts in the surgical management of esophageal cancer was assembled and the existing literature was identified and reviewed prior to the production of the guidelines. Well established procedure specific components of ERAS were reviewed and updated with changes relevant to esophagectomy. Procedure specific, operative and technical sections were produced utilizing the best current level of evidence. All sections were rated regarding the level of evidence and overall recommendation according to the evaluation (GRADE) system.
Results
Thirty-nine sections were ultimately produced and assessed for quality of evidence and recommendations. Some sections were completely new to ERAS programs due to the fact that esophagectomy is the first guideline with a thoracic component to the procedure.
Conclusions
The current ERAS society guidelines should be reviewed and applied in all centers looking to improve outcomes and quality associated with esophageal resection.
We have developed integrated circuits in rapid single flux quantum (RSFQ) impulse logic based on intrinsically shunted tunnel junctions as the active circuit elements. The circuits have been ...fabricated using superconductor-insulator-normalconductor-insulator-superconductor (SINIS) multilayer technology. The paper presents experimental results of the operation of various RSFQ circuits realized in different designs and layouts. The circuits comprise dc/SFQ and SFQ/dc converters, Josephson transmission lines (JTLs), T-flipflops, and analog key components. Functionality has been proved; the circuits have been found to operate correctly in switching. The circuits investigated have a critical current density of j/sub C/=400 A/cm/sup 2/ and a characteristic voltage of V/sub C/=165 /spl mu/V, the area of the smallest junction is A=24 /spl mu/m/sup 2/. The junctions exhibit nearly hysteresis-free current-voltage characteristics (hysteresis: less than 7%), the intra-wafer parameter spread for j/sub C/ is below /spl plusmn/8%. The margins of the bias current I/sub b/ of the circuits have been experimentally determined and found to be larger than /spl plusmn/24%. At preset, constant values of I/sub b/, the range of a separate bias current I/sub bsw/ fed to a switching stage integrated between two segments of JTL's is fully covered by the operation margins which are larger than /spl plusmn/56%.
Abstract
Type III radio bursts are not only the most intense but also the most frequently observed solar radio bursts. However, a number of their defining features remain poorly understood. ...Observational limitations, such as a lack of sufficient spectral and temporal resolution, have hindered a full comprehension of the emission process, especially in the hectokilometric wavelengths. Of particular difficulty is the ability to detect the harmonics of type III radio bursts. Here we report the first detailed observations of type III fundamental–harmonic pairs in the hectokilometric wavelengths, observed by the Parker Solar Probe. We present a statistical analysis of the spectral characteristics and polarization measurements of the fundamental–harmonic pairs. Additionally, we quantify various characteristics of the fundamental–harmonic pairs, such as the time delay and time profile asymmetry. Our report concludes that fundamental–harmonic pairs constitute a majority of all type III radio bursts observed during close encounters when the probe is in close proximity to the source region and propagation effects are less pronounced.
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