A high efficient integrated planar transformer for primary-parallel isolated boost converters

A high efficient planar integrated magnetics (PIM) design approach for primary parallel isolated boost converters is presented. All magnetic components in the converter including two input inductors and two transformers with primary-parallel and secondary-series windings are integrated into an E-I-E core geometry. Due to a low reluctance path provided by the shared I-core, the two transformers as well as the two input inductors can be integrated independently, reducing the total ferrite volume and core loss. AC losses in the windings and the leakage inductance of the transformer are kept low by interleaving the primary and secondary turns of the transformers. To verify the validity of the design approach, a 1-kW prototype converter with two primary power stages is implemented for a fuel cell fed battery charger application with 20-40 V input and 170-230 V output. An efficiency of 96% can be achieved during nominal operating conditions. Also experimental comparisons between the PIM module and two separate cases have been done in order to illustrate the advantages of the proposed method.

Novel one step transformation method for Escherichia coli and Staphylococcus aureus using arginine-glucose functionalized hydroxyapatite nanoparticles

ABSTRACTDNA cloning requires two steps: the assembly of recombinant DNA molecules and the transformation of the product into a host organism for replication. High efficiencies in both processes can increase the success rate. Recently, we developed an Escherichia coli BW3KD strain with higher transformation efficiency than commonly used cloning strains. Here, we further developed a simple method named TSS-HI (transformation storage solution optimized by Hannahan and Inoue method) for competent cell preparation, which combined the advantages of three common methods for operational simplicity and high transformation efficiency. When competent BW3KD cells were prepared using this developed method, the transformation efficiency reached up to (7.21 ± 1.85) × 109 CFU/μg DNA, which exceeded the levels of commercial chemically competent cells and homemade electrocompetent cells. BW3KD cells formed colonies within 7 h on lysogeny broth agar plates, quicker than the well-known fast-growing E. coli cloning strain Mach1. The competent cells worked effectively for the transformation of assembled DNA of 1 to 7 fragments in one step and promoted efficiencies of transformation or cloning with large plasmids. The cloning efficiency of BW3KD cells prepared by this method increased up to 828-fold over that of E. coli XL1-Blue MRF′ cells prepared by a common method. Thus, competent cells are suitable for different cloning jobs and should help with the increased demand for DNA assembly in biological studies and biotechnology.IMPORTANCE DNA transformation is commonly used in cloning; however, high transformation efficiency becomes a limiting factor in many applications, such as the construction of CRISPR and DNA libraries, the assembly of multiple fragments, and the transformation of large plasmids. We developed a new competent cell preparation method with unmatched transformation efficiency. When the BW3KD strain, derived from Escherichia coli BW25113 cells, was prepared by this method, its transformation efficiency reached up to (7.21 ± 1.85) × 109 CFU/μg DNA, which broke the record for chemically prepared competent cells. Routine cloning could be completed in 1 day due to the high growth rate of this strain. The competent cells were shown to be highly efficient for transformation or cloning with large plasmids and for the assembly of multiple fragments. The results highlight the effectiveness of the new protocol and the usefulness of the BW3KD strain as the host.

The paper proposes a soft-switch back-to-back bi-directional DC/DC converter. There is no input inductor in this topology in both the step-down and step-up mode, as a result, there is no RHP zero in the system model and hence the converter always functions as a minimum phase system. This makes the converter a first-order system, and the close loop control design becomes easy. The removal of the inductor reduces power loss during the operation. Moreover, soft switching using zero-voltage-switching (ZVS) reduces switching power losses. The proposed topology achieves high efficiency and high power density. The paper describes the analysis and design for the converter system under non-ideal conditions. The possible ZVS range of the load variation is also given. A large signal average model and a small signal model for the bi-directional converter are derived. Based on the system model, a digital PI controller is designed and is implemented by using an FPGA. Closed loop control and variable load operating performance are experimentally validated on a 100 W prototype converter. A maximum efficiency of 92.3% is achieved.

Molecular validation of genetically transformed Catharanthus roseus plants via different strains of Agrobacterium tumefaciens

This article presents a simple model for the calculation of core losses in permanent magnet machines based on the total flux linkage of the stator winding. In reality, the total core losses will vary as a function of permanent magnet field and the combination of $d-q$ current components even in the case when different $d-q$ currents produce the same amount of stator winding flux linkage at a given speed. The classical model with constant equivalent core loss resistance predicts constant core losses for constant flux linkage which leads to incorrect results. The model presented in this paper expands the classical core loss resistance based model with a novel additional term which corrects the classical model and calculates an additional core loss component as a function of $d$ axis current, total flux linkage of the stator winding, and two constant parameters. The accuracy of the model is confirmed by finite element simulations and core loss measurements for the cases of an interior permanent magnet traction motor and an industrial surface permanent magnet motor (only simulations).

The effects of thickness t and resistivity ρ on the ac and dc core loss and permeability of six laboratory heats of nonoriented, semiprocessed, low-silicon (Si+Al<1.1%) steel were investigated at 10, 15, and 17 kG. The total ac core losses increased nearly linearly with t2/ρ at all three inductions, but none of the proportionality constants were predicted by classic theory. Hysteresis losses tend to increase with increasing oxygen (i.e., inclusions) and decreasing grain size in the steel, but they were not dependent on thickness or resistivity. ac permeability was a complex function of thickness, resistivity, and induction. dc permeability at 15 and 17 kG increased with thickness.

A study on permanent magnet (PM) eddy current and core losses of dual-stator PM machines is investigated in this paper. The analyzed core losses include: the rotor core loss, stator core loss and the total core loss of the machines. Further, the effect of their different rotor pole number is also presented with quantitative comparison. Due to the relatively high electrical frequency of the analyzed 14-rotor pole machine, it gives the largest amount of PM eddy current loss. Similarly, the 13-pole machine exhibits the largest amount of total core loss amongst the compared machines. Although, the investigated machine having 4-rotor pole has a low core loss value, likely due to its low electrical frequency. However, it has the poorest efficiency amongst all, due to its very low output torque. Overall, largest torque density is obtained in the 13-pole machine at rated current condition. http://dx.doi.org/10.4314/njt.v36i4.21

Application analysis of self-bonded electrical steel sheet in high power density PMSM for all-electric aircraft

Genetic transformation Agrobacterium-mediated genetic transformation is a key technology in plant biotechnology to integrably incorporate genes stably and as a platform in functional genomics research. Transformation efficiency still stands out as an important factor in determining the success of experiments as well as on a large-scale basis, especially when dealing with a wide range of plant species with a variation in biological functions. This paper provides a systematic literature research paper on the efficiency of transformation in model plants and the chosen crop systems, with emphasis on the biological processes, optimization and strategies, genomic implications, and new technological improvements. It has been shown that model plants like Arabidopsis thaliana show always high efficiency of transformation, especially when optimized conditions are used like the floral dip protocol in combination with physiological pre-treatments including control drought stress. In production crops like soybean and wheat, genotype dependency and tissue regeneration issues limit the efficiency of transformation, but the use of auxiliary chemical treatments, optimised conditions of co-cultivation, and to a great extent, the selection of improved explants boosts the success of gene delivery. Host immune responses are a primary biological impediment to successful transformation, and engineered attenuated bacterial strains that can counter immune body detection are more efficient. The genomic analysis shows that random T-DNA insertion may bring structural variation and unwanted genomic alterations, thus the use of molecular characterization to assure biosafety. Novel technology, such as nanovector-based delivery platforms, artificial intelligence-based platform of design of gene-editing applications, and high-throughput technologies in phenotyping, further reinforce transformation evaluation and scalability. All in all, the results suggest that biological optimization in combination with technical progress and genomic validation are necessary to enhance the validity and practicability of the Agrobacterium-mediated transformation in the research on plants and crop enhancement programs.

Introducing air gaps into the magnetic core of high-temperature superconducting (HTS) transformers can help mitigate magnetic saturation to some extent and influence both electromagnetic performance and losses. To investigate this effect in detail, this paper develops a three-dimensional finite element model of a 9 kVA three-phase HTS transformer. The study examines how variations in air-gap length and position affect the main magnetic flux path, leakage field distribution, and associated losses. The results show that increasing the air-gap length effectively alleviates local magnetic saturation in the core, resulting in a significant reduction in core loss. However, this also leads to a notable increase in leakage field intensity near the gap edges. When the air-gap percentage increases from 0% to below 6%, the AC loss remains under 100 W; beyond 8%, the AC loss rises sharply. Furthermore, placing the air gap at the center of the core limb minimizes both AC loss and core loss. These findings offer theoretical support for optimizing core air-gap design in HTS transformers to improve electromagnetic performance and suppress energy loss.

Chicken embryos kept in culture medium were bombarded using a high helium gas pressure biolistic device. To optimize the factors that affect transformation efficiency, the lacZ gene under control of the human cytomegalovirus immediate early enhancer/promoter was used as a reporter gene. There was an inverse relationship between survival rate and transformation efficiency. The best conditions obtained for high embryo survival and high transformation efficiency were achieved with 800 psi helium gas pressure, 500 mmHg vacuum, gold particles, an 8 cm DNA-coated microparticle flying distance to the embryo and embryo placement 0.5 cm from the center of the particle dispersion cone. Under these conditions, transformation efficiency was 100%, survival rate 25% and the number of expression units in the embryo body cells ranged from 100 to 1,000. Expression of green fluorescent protein was also detected in embryos bombarded under optimal conditions. Based on the results obtained, the biolistic process can be considered an efficient method for the transformation of chicken embryos and therefore can be used as a model system to study transient gene expression and tissue-specific promoters.

Streptomyces griseus does not readily take up foreign DNA isolated from other Streptomyces species or Escherichia coli, presumably due to its unique restriction-modification systems that function as a barrier for interspecific DNA transfer. To efficiently transform S. griseus by avoiding the restriction barriers, we methylated incoming DNA in vivo and in vitro and treated protoplasts with heat prior to transformation. Whereas heat treatment of protoplasts or methylation of the E. coli-Streptomyces shuttle vectors (pXE4 and pKK1443) did not prominently improve the transformation efficiency, HpaII methylation of the vectors from any E. coli strains tested in this study highly increased the transformation efficiency. The highest transformation efficiency was observed when the shuttle vectors were isolated from the dam, hsd strain of E. coli (GM161) and methylated by AluI and HpaII methyltransferases, and the efficiency was approximately the same as that of the vectors from S. griseus. We identified several restriction-modification systems that decrease the transformation efficiency. This research also led us to understand methylation profiles and restriction-modification systems in S. griseus.

With increasing demand for flat displays, slim telecom/IT power supplies, and portable devices, the use of Planar Transformers (PTs) is becoming mandatory to achieve slim and compact converter designs. In particular, PTs present a significant opportunity to replace tall and bulky wire-wound transformers in industry standard LLC converters. However, the Common-Mode (CM) noise generated by PTs remains a significant obstacle to making LLCs effective. This paper develops a paired-layers interleaving method to overcome CM noise in LLC PTs. By reducing noise, the paired-layers interleaving prevents the use of bulky CM chokes, helping to keep a slim/flat form factor for LLC converters with high power density. As well, the paired-layers interleaving maintains low AC resistance and leakage inductance, two desirable features in high efficiency transformers. The paired-layers interleaving successfully shields problematic turns with high dv/dt and overlaps the turns with the same dv/dt. As a result, circulating currents between primary and secondary (which are known as CM noise) are prevented, which leads to significant reduction of the converter's noise. The proposed PTs for LLC converters are validated using a 1kW prototype. Experimental results show that the proposed PT with 1.1nF parasitic capacitance generates 15-25dB less noise than a wire-wound transformer that has only 18pF parasitic capacitance, which is the result of using the paired-layers interleaving method.

Additively manufactured soft magnetic Fe-3.7%w.t.Si toroidal samples with solid and novel partitioned cross-sectional geometries are characterized through magnetic measurements. This study focuses on the effect of air gaps and annealing temperature on AC core losses at the 50 Hz frequency. In addition, DC electromagnetic material properties are presented, showing comparable results to conventional and other 3D-printed, high-grade, soft magnetic materials. The magnetization of 1.5 T was achieved at 1800 A/m, exhibiting a maximum relative permeability of 28,900 and hysteresis losses of 0.61 (1 T) and 1.7 (1.5 T) W/kg. A clear trend of total core loss reduction at 50 Hz was observed in relation to the segregation of the specimen cross-sectional topology. The lowest 50 Hz total core losses were measured for the toroidal specimen with four internal air gaps annealed at 1200 °C, exhibiting a total core loss of 1.2 (1 T) and 5.5 (1.5 T) W/kg. This is equal to an 860% total core loss reduction at 1 T and a 510% loss reduction at 1.5 T magnetization compared to solid bulk-printed material. Based on the findings, the advantages and disadvantages of printed air-gapped material internal structures are discussed in detail.