Transformer Coupling Research Articles

Efficiency Characteristics of Loosely Coupled Transformer With Laminated Nanocrystalline Core Considering Nonlinear Factors Caused by Crushing and Compressing Process

Efficiency Characteristics of Loosely Coupled Transformer With Laminated Nanocrystalline Core Considering Nonlinear Factors Caused by Crushing and Compressing Process

Mechanisms and models of interface trap annealing in positively-biased MOS devices

Abstract We propose a hydrogen anion (H$^-$) passivation mechanism of the interface trap annealing (ITA) in positively-biased metal-oxide-semiconductor (MOS) devices. It is demonstrated that, the protons (H$^+$) released in SiO$_2$ due to H$_2$ cracking on oxide traps can migrate into Si at relatively high temperature, therefore passivating the interfacial $P_b$ centers by capturing two electrons provided by the positive bias. This new mechanism explains the elimination temperature of about 100$^\circ$C in experiments, which is much lower than temperature above 220$^\circ$C predicted by the traditional H$_2$ passivation mechanism. We also derive analytic models of the ITA, based on the coupling transformation dynamics of oxide and interface traps, as well as the concept of hierarchically constrained dynamics in glassy materials. These models can universally describe a generation-to-elimination transition of $P_b$, and predict the enhanced elimination of $E'_\gamma$ as the annealing temperature is elevated. Moreover, we demonstrate that, the defect annealing models can be applied to analysis the nonmonotonic temperature dependence of the annealing of threshold voltage shift in nMOS devices. Our findings provide a theoretical basis for achieving the low temperature elimination of interface traps, and for setting the high temperature stages of accelerated aging and damage evaluations of MOS devices.

Coupling SWAT and Transformer Models for Enhanced Monthly Streamflow Prediction

The establishment of an accurate and reliable predictive model is essential for water resources planning and management. Standalone models, such as physics-based hydrological models or data-driven hydrological models, have their specific applications, strengths, and limitations. In this study, a hybrid model (namely SWAT-Transformer) was developed by coupling the physics-based Soil and Water Assessment Tool (SWAT) with the data-driven Transformer to enhance monthly streamflow prediction accuracy. SWAT is first constructed and calibrated, and then its outputs are used as part of the inputs to Transformer. By correcting the prediction errors of SWAT using Transformer, the two models are effectively coupled. Monthly runoff data at Yan’an and Ganguyi stations on Yan River, a first-order tributary of the Yellow River Basin, were used to evaluate the proposed model’s performance. The results indicated that SWAT performed well in predicting high flows but poorly in low flows. In contrast, Transformer was able to capture low-flow period information more accurately and outperformed SWAT overall. SWAT-Transformer could correct the errors of SWAT predictions and overcome the limitations of a single model. By integrating SWAT’s detailed physical process portrayal with Transformer’s powerful time-series analysis, the coupled model significantly improved streamflow prediction accuracy. The proposed models offer more accurate and reliable predictions for optimal water resource management, which is crucial for sustainable economic and societal development.

NHC-Catalyzed Umpolung Driven Intramolecular Cyclizations for the Generation of 3,4-Cycloheptanone Annulated Tetracyclic Indole Derivatives.

In this Letter, we disclose the development and exploitation of umpolung reactivity of N-heterocyclic carbene (NHC) organocatalysts in generating tetracyclic indole derivatives with the introduction of a cycloheptane ring forming event. The NHC-catalyzed intramolecular vinylogous Stetter, Stetter, benzoin, and formal cross-dehydrogenative coupling transformations have been executed, enabling the construction of 3,4-cycloheptannulated indole derivatives in good to excellent yields. The developed protocols utilize an inexpensive catalyst and feature operational simplicity, atom economy, gram-scale syntheses, and postsynthetic availability.

Coupled transformation pathways of iron minerals and natural organic matter related to iodine mobilization in alluvial-lacustrine aquifer

The complex of natural organic matter (NOM) and iron minerals in sediment is the main host and source of groundwater iodine. However, the transformation pathways of the complex remain unclear. The groundwater and sediment from the Hetao Basin were collected in this study to analyze multi-isotopes, NOM molecular characteristics, and iron mineral phases. The results showed that high-iodine groundwater was mainly observed in the discharge area, where biodegradation of NOM, sulfate reduction and methanogenesis occurred. Compared to the shallow clayey sediments, the confined sandy sediments had lower iodine content, a lower fraction of crystalline iron oxides, and a higher fraction of carbonate associated Fe(II) minerals, suggesting that the release of sediment iodine in the aquifer is related to the transformation of sediment Fe(III) hydroxides/oxides. Moreover, the molecular features of high-iodine groundwater NOM and sandy sediment NOM were characterized by a higher proportion of refractory compounds, suggesting that the reductive transformation of sediment Fe(III) hydroxides/oxides is fueled by degradable organic compounds. The microbial Fe-reducing and/or sulfate-reducing processes cause the enrichment of groundwater iodine in the form of iodide via the transformation of iodine species. These findings provide new insights into the genesis of high-iodine groundwater.

Visible-Light-Antenna Ligand-Enabled Samarium-Catalyzed Reductive Transformations.

Although divalent Sm reagents are some of the most important single-electron transfer reagents for reductive transformations, their catalytic applications are challenging. In this study, a bidentate phosphine oxide ligand substituted with 9,10-diphenylanthracene as a visible-light antenna was designed for Sm-catalyzed reduction reactions under mild reaction conditions. Pinacol coupling of aryl ketones and aldehydes was developed with 1 mol % of Sm catalyst and organic amine (DIPEA) as a sacrificial mild reductant. Mechanistic studies suggest that the visible-light-antenna ligand coordinates to Sm(III) and reduces Sm(III) to Sm(II) under visible-light irradiation. The catalytic system is also applicable for cross-pinacol coupling and other single-electron reductive transformations, including aza-pinacol coupling, flavone dimerization, C-O bond cleavage, C-C ring-opening of cyclopropane, ketyl-olefin coupling, and cross-coupling of the ketyl radical with the α-amino radical.

Piezoelectric Transducers: Complete Electromechanical Model with Parameter Extraction.

This paper presents a complete electromechanical (EM) model of piezoelectric transducers (PTs) independent of high or low coupling assumptions, vibration conditions, and geometry. The PT's spring stiffness is modeled as part of the domain coupling transformer, and the piezoelectric EM coupling coefficient is modeled explicitly as a split inductor transformer. This separates the coupling coefficient from the coefficient used for conversion between mechanical and electrical domains, providing a more insightful understanding of the energy transfers occurring within a PT and allowing for analysis not previously possible. This also illustrates the role the PT's spring plays in EM energy conversion. The model is analyzed and discussed from a circuits and energy harvesting perspective. Coupling between domains and how loading affects coupled energy are examined. Moreover, simple methods for experimentally extracting model parameters, including the coupling coefficient, are provided to empower engineers to quickly and easily integrate PTs in SPICE simulations for the rapid and improved development of PT interface circuits. The model and parameter extractions are validated by comparing them to the measured response of a physical cantilever-style PT excited by regular and irregular vibrations. In most cases, less than a 5-10% error between measured and simulated responses is observed.

Small Sample Image Segmentation by Coupling Convolutions and Transformers

Small Sample Image Segmentation by Coupling Convolutions and Transformers

Real-time analysis of voltage and frequency regulation of self-excited induction generator based micro hydro plant using generalized impedance controller

– The self-excited induction generator (SEIG) is well accepted for application in micro hydropower plants. However, in the edge-of-grid application it exhibits a limitation in its capacity to sustain the desired terminal voltage along with the frequency of variations in the prime mover's speed and load. Terminal voltage and frequency regulation are significant concerns for such schemes, and many such techniques are available to regulate the same. This paper presents a closed-loop control technique based on a generalized impedance controller (GIC) responsible for the impedance-controlled functioning of the pulse width variation voltage source converter (PWM-VSC) to regulate frequency and terminal voltage of machine with various loading conditions. A coupling transformer is connected between GIC and SEIG, and the ratings of GIC and transformer should be the same as SEIG, as GIC must compensate for the entire SEIG output. Three phase, 2.2 kW, 415 V, 4.8 A, 50 Hz SEIG, and a three IGBT-based voltage-sourced inverter with coupling transformer, are modelled in MATLAB environment. SEIG frequency and voltage effects in response to the GIC modulation index and phase angle are investigated in the real-time environment using the OPAL-RT (ver. OP4510) environment. The voltage and frequency are controlled using the proposed SEIG-GIC scheme, and the simulation results achieved from MATLAB/Simulink were validated with real-time observations.

The coupling transformation process of biodegradation and pyrolysis for Dananhu low-rank coal

The study presented a novel approach for coupling biodegradation and pyrolysis to transform low-rank coal. In the first stage, four kinds of bacteria, Planomicrobium huatugouensis (P. huatugouensis), Sphingomonas polyaromaticivorans (S. polyaromaticivorans), Pseudomonas putida (P. putida), and Bacillus subtilis subsp. subtilis (B. subtilis subsp. subtilis), were used to transform the Dananhu low-rank coal. After the first stage, the coal that has not been biodegraded (residual coal) undergoes the second stage of pyrolytic transformation, which is carried out by a thermogravimetric analyzer combined with Fourier-transform infrared spectrometry (TG-FTIR). The results showed that the maximum coupling transformation rate of biodegradation and pyrolysis could reach 73.95%, which was 21.88% higher than the thermal transformation rate of Dananhu low-rank coal and 27.37% higher than the optimal microbial transformation rate. This indicated that coupling transformation could significantly improve the utilization rate of Dananhu low-rank coal. In the stage of biodegradation transformation, bacteria destroyed the carboxyl groups, ether bonds, and other oxygen-containing functional groups in Dananhu low-rank coal, converting the large molecules of coal into liquid molecules, meanwhile, the compact coal structure became loose, and the residual coal was also pyrolyzed easily than Dananhu low-rank coal. During the pyrolysis process, a large number of fatty chains, carboxyl groups, oxy groups, and hydroxy groups were decomposed to produce lots of gas-phase products. The pyrolysis products showed an increase in the release of CO and CH4, and an increase in the proportion of aliphatic hydrocarbons in the volatiles. The high efficiency of coupling transformation is due to the combination of the advantages of the two technologies, which is achieving the green and energy-efficient utilization of low-rank coal.

Enantioselective Hydrofunctionalization of Cyclobutenones: Total Synthesis of gem‐Dimethylcyclobutane Natural Products

AbstractCyclobutanes with a gem‐dimethyl group are common motifs in natural products. However, strategies for constructing enantioenriched gem‐dimethyl cyclobutanes are still underdeveloped. Herein, we report an enantioselective approach to synthesize a broad group of chiral 2,3‐disubstituted cyclobutanones through sequential 1,4‐conjugate addition/trapping/cross‐coupling of readily available cyclobutenones. The intermediate 2‐bromocyclobutanone provides a valuable synthetic handle for further coupling transformations. In addition, this strategy was successfully utilized to synthesize gem‐dimethyl cyclobutane‐containing natural products, including (+)‐β‐caryophyllene, (−)‐raikovenal, (−)‐1β,9αH‐5‐linoleoyloxy‐4,5‐secocaryophyllen‐4‐one, and (−)‐rumphellanones A−C.

Enantioselective Hydrofunctionalization of Cyclobutenones: Total Synthesis of gem-Dimethylcyclobutane Natural Products.

Cyclobutanes with a gem-dimethyl group are common motifs in natural products. However, strategies for constructing enantioenriched gem-dimethyl cyclobutanes are still underdeveloped. Herein, we report an enantioselective approach to synthesize a broad group of chiral 2,3-disubstituted cyclobutanones through sequential 1,4-conjugate addition/trapping/cross-coupling of readily available cyclobutenones. The intermediate 2-bromocyclobutanone provides a valuable synthetic handle for further coupling transformations. In addition, this strategy was successfully utilized to synthesize gem-dimethyl cyclobutane-containing natural products, including (+)-β-caryophyllene, (-)-raikovenal, (-)-1β,9αH-5-linoleoyloxy-4,5-secocaryophyllen-4-one, and (-)-rumphellanones A-C.

Asynchronous characteristics of Feammox and iron reduction from paddy soils in Southern China

Recently, the newly discovered anaerobic ammonium oxidation coupled with iron reduction (i.e., Feammox) has been proven to be a widespread nitrogen (N) loss pathway in ecosystems and has an essential contribution to gaseous N loss in paddy soil. However, the mechanism of iron-nitrogen coupling transformation and the role of iron-reducing bacteria (IRB) in Feammox were poorly understood. This study investigated the Feammox and iron reduction changes and microbial community evolution in a long-term anaerobic incubation by 15N isotope labeling combined with molecular biological techniques. The average rates of Feammox and iron reduction during the whole incubation were 0.25 ± 0.04 μg N g−1 d−1 and 40.58 ± 3.28 μg Fe g−1 d−1, respectively. High iron oxide content increased the Feammox rate, but decreased the proportion of Feammox–N2 in three Feammox pathways. RBG-13-54-9, Brevundimonas, and Pelomonas played a vital role in the evolution of microbial communities. The characteristics of asynchronous changes between Feammox and iron reduction were found through long-term incubation. IRB might not be the key species directly driving Feammox, and it is necessary to reevaluate the role of IRB in Feammox process.

Toward Value-Added Chemicals from Carbohydrates via C–C Bond Cleavage and Coupling Transformations

Toward Value-Added Chemicals from Carbohydrates via C–C Bond Cleavage and Coupling Transformations

Direct single‐phase isolated improved gamma Z‐source AC–AC converter suitable for DVR application

AbstractA direct single‐phase isolated improved gamma Z‐source AC–AC converter is designed and manufactured in proposed paper. This converter contains an impedance source structure and its advantages. In general, these advantages are as follows. Firstly, the proposed structure has a wide range of output voltage as boost and buck as well as in‐phase or out‐of‐phase states. Secondly, the proposed converter is electrically isolated thanks to a high frequency transformer (HFT), which significantly reduces the volume of the structure; therefore, in applications such as dynamic voltage restorer (DVR), there is no need to install a coupling transformer with the grid frequency which is very bulky and full of losses. Furthermore, the HFT of the proposed converter is a three winding transformer which also acts as the inductance needed for impedance source network. In addition, the safe commutation method has been utilized, which reduces the voltage spikes on the power switches. Finally, the analysis and design of this converter has been done, and then confirmed by a small‐scale laboratory prototype.

Semantic-Oriented Feature Coupling Transformer for Vehicle Re-Identification in Intelligent Transportation System

More robust intelligent transportation systems including autonomous driving systems are in full flourish with the revolution of deep learning and the 6G wireless communication network. Vehicle Re-Identification, an indispensable branch of the intelligent transportation system, aims to retrieve specific vehicles captured from non-overlapping cameras. However, this is fundamentally challenging with the substantial inter-class similarity and substantial intra-class divergence. Embedding semantic information into vehicle re-identification task has gained ample interest, but the performance needs to be further improved. This work proposes a semantic-oriented feature coupling transformer (SOFCT) for vehicle re-identification as a solution. Specifically, the knowledge-based transformer is first embedded to model images with discriminative attributes. Second, original patches are divided into five semantic groups via semantics-patches coupling, and the feature extractions for different semantics are performed in the semantic feature extraction (SFE) transformer. Third, patch features are weighted via semantics-patches coupling in the patch feature weighting (PFW) transformer, the weighted feature is fed into subsequent encoders to excavate information. Finally, two groups of learnable semantics are embedded to automatically learn semantic features in the learnable semantic extraction (LSE) transformer. Experiments demonstrate that the proposed SOFCT method surpasses other state-of-the-arts with the mAP/Rank-1 of 80.7%/96.6%, 89.8%/84.5%, 86.4%/80.9%, and 84.3%/78.7% on VeRi776 and VehicleID.

Research on Mine Wide Voltage Adaptive Power Supply

To solve the problem of multiple voltage levels and wide range of variations of underground power supply in domestic coal mines, this paper putting forward four wide power supply of adaptive design options with wide input voltage (AC 80-850 V), including phase shifted rectification based on fully controlled bridge, direct voltage adjustment based on AC power supply, voltage adjustment based on AC power supply rectification followed by chopping control, and a power supply voltage adjustment based on magnetic coupling transformer and thyristor automatic switching. After experimental comparison, the preferred scheme for automatic switching between magnetic coupling transformer and thyristors is preferred. The main circuit of this scheme adopts magnetic coupling transformer and thyristor control method, and the control circuit adopts a three way drive circuit based on MCU control, while adopting the strategy of instantaneous voltage tracking control. This scheme achieves stable operation of the output DC power supply voltage at 24V when the input AC power supply voltage varies from 80 to 850 V. The experimental results showed programme was stable and reliable, and it’s worth applying and has practical significance.

Effect of Metal Oxide Semiconductor Field-Effect Transistor Output Parasitic Capacitance on Efficiency in Full-Bridge LLC DC/DC Converters.

This study analyzed the efficiency impact of a MOSFET output parasitic capacitance (Coss) on a full-bridge LLC DC/DC converter. The core of the converter was the control chip for a half-bridge LLC DC/DC converter, and the output signal of the chip controlled the first-arm power transistors of the primary side of the converter. The coupling transformer reversed the output signal to control the primary side of the second arm of the power transistor. The full-bridge converter comprises a half-bridge control chip that converts the high-voltage DC power supply to a low-voltage DC power supply, which is then synchronously rectified and supplied to the load. The primary side of the power transistor achieves a zero-voltage switching (ZVS) state through the resonance of the LLC converter. This design gives the converter high power density and a simple structure. Furthermore, to determine the appropriate output parasitic capacitance for improving converter efficiency, this study analyzed the effect of the output parasitic capacitance on the switching loss and conduction loss of the power transistor on the basis of the output parasitic capacitance of the primary-side power transistor. A 1200 W converter prototype was fabricated in this study, and when the output was 300 W, efficiency increased from 92.603% to 93.462%, a 0.859% increase. The empirical results verified the feasibility of the proposed theory.

Real-Time Implementation of Controlled Energization of Coupled Power Transformer Using Multi-Stepped PIR, Part-1

Real-Time Implementation of Controlled Energization of Coupled Power Transformer Using Multi-Stepped PIR, Part-1

State-Feedback Control of a Hybrid Distribution Transformer for Power Quality Improvement of a Distribution Grid

A Hybrid Distribution Transformer (HDT) combines a power converter and a conventional Low-Frequency Transformer (LFT) in a single device. The most recurrent configuration consists of a shunt converter fed by the Auxiliary Winding (AW) of the LFT and a series converter connected to the low-voltage grid. Nonetheless, load harmonics circulate through the power converter and LFT, affecting their lifetime. In this work, an HDT composed of a series converter connected to the primary side through Coupling Transformers and a shunt converter directly connected to the secondary side is presented. The HDT model and discrete-time state-feedback control are presented. The results show that the HDT can improve the power quality of the grid, focused on extending the LFT lifetime.