Transformer Coupling Research Articles

Crosslinked polymer encapsulated palladium nanoparticles for catalytic reduction and Suzuki reactions in aqueous medium

Acrylamide and N-isopropylacrylamide were copolymerized in the presence of a N,N-methylenebisacrylamide crosslinker to obtain poly(N-isopropylacrylamide-co-acrylamide) [P(NA)] polymer colloidal particles. Pd nano crystals with diameter of 4–8 nm were loaded into the [P(NA)] microgels by reduction of [PdCl4]-2 within dispersion of polymer microgels. The Pd NPs-loaded hybrid microgels were analysed by TEM, STEM, EDX and XRD. The catalytic ability of the Pd-[P(NA)] system was investigated towards reductive transformation of nitroarenes into corresponding aryl amines and Suzuki coupling transformation in a green solvent, H2O. The progress of catalytic reaction was examined by thin layer chromatography (TLC). Different reactants were effectively converted into their corresponding products with great to fabulous yields (extending from 75 to 97%) under gentle reaction conditions. The Pd-[P(NA)] catalyst is stable for long time and can be utilized numerous times without any notable loss in its catalytic action.

Synthesis of Alkenylboronates from N-Tosylhydrazones through Palladium-Catalyzed Carbene Migratory Insertion.

The palladium-catalyzed oxidative borylation reaction of N-tosylhydrazones has been developed. The reaction features mild conditions, broad substrate scope, and good functional group tolerance. It thus represents a highly efficient and practical method for the synthesis of di-, tri-, and tetrasubstituted alkenylboronates from readily available N-tosylhydrazones. One-pot Suzuki coupling and other transformations highlight the synthetic utility of the approach. DFT calculations have revealed that palladium-carbene formation and subsequent boryl migratory insertion are the key steps in the catalytic cycle. The high stereoselectivity observed in the formation of trisubstituted alkenylboronates has been explained by distortion-interaction analysis and NBO analysis.

Current-limiting characteristics of a modified flux-coupling type superconducting fault current limiter and its effects on the transient stability of a multi-machine power system

A modified flux-coupling type superconducting fault current limiter (SFCL) is proposed here for suppressing fault currents. The modified SFCL consists of a coupling transformer, an yttrium barium copper oxide (YBCO) pancake coil, and a controlled switch. By flexibly adjusting the controlled switch's contact states based on the system operational conditions, the coupling transformer's primary inductance as well as the YBCO coil's normal-state resistance are incorporated into the main system for current limitation. Because the modified SFCL has the advantages of resistive and inductive SFCLs, it may improve the power system's transient behavior. Hence, the SFCL's effect on the transient stability of a multi-machine power system was also theoretically investigated. Further, simulations were conducted for accessing the SFCL's performance characteristics under different fault conditions. The results show that using the proposed SFCL can effectively restrain the increased fault current and improve the bus voltage sag; meanwhile, the imitated multi-machine system's power-angle oscillation can be obviously reduced.

The Optimal Operation Model of Electric-Thermal-Gas Integrated Energy System Considering Multi-Energy Complementarity

As China’s environment and climate problems become more and more serious, the integrated energy system is booming. However, the coupling between various systems is not strong, and it is urgent to increase the coupling between multiple systems. Taking the total cost of the integrated energy system as the objective function, the independent operation and coupling transformation of the power system, natural gas system and thermal system within the system are considered. In this paper, a system planning model is built to meet the three types of loads in the system: electric load, thermal load and gas load, so as to increase the coupling of the system, ensure the reliable operation of the integrated energy system and improve the energy utilization efficiency.

Coupling transformation of carbon, nitrogen and sulfur in a long-term operated full-scale constructed wetland.

The coupling transformation of carbon, nitrogen and sulfur compounds has been studied in lab-scale and pilot-scale constructed wetlands (CWs), but few studies investigated full-scale CW. In this study, we used batch experiments to investigate the potentials of carbon, nitrogen and sulfur transformation in a long-term operated, full-scale horizontal subsurface flow wetland. The sediments collected from the HSFW were incubated for 48h in the laboratory with supplying various dosages of carbon, nitrogen and sulfur compounds. The results showed that heterotrophic denitrification was the main pathway. At the same time, the sulfide (S2-)-based autotrophic denitrification was also present. Increasing TOC concentration or NO3- concentration could promote heterotrophic denitrification but did not inhibit the sulfide-based autotrophic denitrification. In our experiment, the highest NO3- removal via autotrophic denitrification was 25.23% while that via heterotrophic denitrification was 73.66%, leading to the total NO3- removal of 98.89%. The results also demonstrated that NO3- rather than NO2- was the preferable electron acceptor for both heterotrophic and sulfide-based autotrophic denitrification in the CW. Increasing S2- concentrations promote NO3- removal from 12.99% to 25.23% without organic carbon, but varying NO3- or NO2- has no effects. These results indicated that concentrations of S2-, instead of NO3- or NO2-, was the limiting factor for sulfide-based autotrophic denitrification in the studied CW. The microbial community analysis and correlation analysis between the transformation of carbon, nitrogen and sulfur compounds and relative abundance of bacteria further confirmed that in the CW, the key pathways coupling transformation were heterotrophic denitrification and sulfide-based autotrophic denitrification. Overall, the current study will enhance understanding of carbon, nitrogen, and sulfur transformation in CW and support better design and treatment efficiency.

Optimal Range of Coupling Coefficient of Loosely Coupled Transformer Considering System Resistance

Accurate system resistance may lead to an obvious error between the simulated and the real efficiency of the system. This paper proposes an optimal range of coupling coefficient for ensuring the efficiency and the sufficient output power of the WPT (wireless power transfer) system. A 3-kW prototype WPT system is manufactured and the effectiveness of the optimal range of coupling coefficient is validated.

AC system’s strength evaluation of UHVDC system under hierarchical connection mode

The inverter’s end of ultra high voltage DC (UHVDC) system under hierarchical connection mode (HCM) is connected to 500 and 1000 kV AC buses through high end converter and low end converter transformers, respectively. The two AC buses are interconnected via coupling transformer and the tie line. This complex structure of interconnection at inverter’s end can make the understanding unclear about each AC system’s strength of UHVDC-HCM. Therefore, this paper covers the system’s strength evaluation by developing the “Hierarchical mode effective short circuit ratio” (HMESCR) index. The HMESCR incorporates the impact of neighborhood AC networks, impedance of coupling transformer, the tie line and strength of the objective AC network. Based on the proposed index, an equivalent model for UHVDC-HCM system is developed. An equivalent model is verified under the steady state conditions such as maximum available power and the transient conditions such as commutation failure immunity index under AC faults. In addition, three different cases are considered in order to get the in-depth and comparative performance analysis of an equivalent model with UHVDC-HCM system. MATLAB and PSCAD/EMTDC are used as analysis tools for illustrating the steady state and transient state conditions. The analysis indicates that the presented equivalent model has similar behavior as UHVDC-HCM system under both steady state and transient state conditions, which verifies the accuracy of proposed index in assessing the strength of both AC systems of UHVDC-HCM.

A 13.5-dBm 1-V Power Amplifier for W-Band Automotive Radar Applications in 28-nm FD-SOI CMOS Technology

This article presents a $W$ -band power amplifier (PA) for automotive radar applications. It was designed in a 28-nm fully depleted silicon-on-insulator CMOS technology with a transition frequency of around 270 GHz and a standard back-end-of-line. The circuit adopts a pseudo-differential topology with coupling transformers, which allow both compact matching networks and layout-optimized interstage interconnections. The power stage exploits a transformer-based folded-cascode structure that is very suitable for low-voltage mm-wave power applications. The PA is able to deliver a saturated output power as high as 13.5 dBm at 77 GHz with a power-added efficiency of 14.5%, while using a power supply as low as 1 V. The linear power gain is 26.5 dB and the current consumption is 150 mA. The PA occupies a core die size of $700\,\,\mu \text{m}\,\,\times 200\,\,\mu \text{m}$ .

Rhodium(III)-catalyzed chelation-assisted ortho-selective carbon−hydrogen alkylation of phenols with diazocarbonyl compounds involving a carbene migratory insertion process

An efficient and convenient rhodium(III)-catalyzed chelation-assisted ortho-selective carbon−hydrogen bond alkylation of phenols treated with readily available diazocarbonyl compounds as the alkyl source has been described. Migratory carbene insertion represents the principal step to realize this carbenoid coupling transformation, giving rise to a broad rang of alkylated products and at the same time, releasing nitrogen gas as sole byproduct. This protocol offers exclusive regioselectivities, moderate to excellent chemical yields, and good functional group tolerance.

Coupled nitrogen transformation and carbon sink in the karst aquatic system: a review

Abstract Carbonate bedrock regions represent that 14% of Earth's continental surface and carbon (C) sink in karst water plays an important role in the global C cycle due to the CO2 consumption during carbonate mineral weathering. Intensive agriculture and urbanization have led to the excessive input of nitrogen (N) into aquatic systems, while the high concentrations of inorganic C in the karst water might affect the N cycle. This paper summarized the characteristics of water in karst regions and discussed the N transformation coupled with the C cycle in the condition of high Ca2+ content, high pH, and high C/N ratios. Carbonates can consume more atmospheric and pedologic CO2 than non-carbonates because of their high solubility and high rate of dissolution, resulting in the higher average CO2 sink in karst basins worldwide than that in non-karst basins. Therefore, carbonate mineral weathering and aquatic photosynthesis are the two dominant ways of CO2 absorption, which are termed as coupled carbonate weathering. As the alkalinity and high C/N content of karst water inhibit the denitrification and mineralization processes, the karst aquatic environment is also served as the N sink.

Coupled Electrochemical Transformation and Filtration of Water Pollutants by Cathodic-Carbon Nanotube Membranes

Coupled Electrochemical Transformation and Filtration of Water Pollutants by Cathodic-Carbon Nanotube Membranes

Coupled heat transfer and phase transformations of dual-phase steel in coil cooling

Dual-phase steels are generally used in the car industry due to high tensile strength and good formability, which are obtained by a mixture of bainite and ferrite phases. This microstructure is achieved through slow rate coil cooling. However, the manufacturing of dual-phase steels introduces various challenges such as the instability of the cold rolling process. An important factor affecting this is the non-uniform coil cooling of a hot rolled strip. In coil cooling the cooling rates are not controlled and there are different thermal contacts during coil conveyance causing unequal cooling of the steel coil. Unequal cooling rates lead to non-uniform coil cooling, producing irregular phase transformations on different sides of the coil, which causes periodical variations of the phase fractions in the steel strip. Varying phase fractions cause thickness deviations in the strip during the cold rolling process. A three-dimensional transient heat transfer finite element model was developed and used for modeling the complete coil conveyance chain and coil field cooling of the coil on an industrial scale. A coupled phase transformation model is implemented as a subroutine into the finite element model for calculating the resulting phase fractions. It was found that the different thermal contacts during the coil conveyance produce uneven cooling rates causing length- and widthwise variations in the phase fractions. The heat transfer model is validated by comparing temperature profiles between the simulated and measured coil edges. The phase transformation model is fitted into experimental data and verification is carried out in industrial conditions by comparing the modeled phase fractions and test samples from a cooled and unwound steel coil.

The Atmospheric Boundary Layer and Surface Conditions during Katabatic Wind Events over the Terra Nova Bay Polynya

Off the coast of Victoria Land, Antarctica an area of open water—the Terra Nova Bay Polynya (TNBP)—persists throughout the austral winter. The development of this coastal polynya is driven by extreme katabatic winds blowing down the slopes of Transantarctic Mountains. The surface-atmosphere coupling and ABL transformation during the katabatic wind events between 18 and 25 September 2012 in Terra Nova Bay are studied, using observations from Aerosonde unmanned aircraft system (UAS), numerical modeling results and Antarctic Weather Station (AWS) measurements. First, we analyze how the persistence and strength of the katabatic winds relate to sea level pressure (SLP) changes in the region throughout the studied period. Secondly, the polynya extent variations are analysed in relation to wind speed changes. We conclude that the intensity of the flow, surface conditions in the bay and regional SLP fluctuations are all interconnected and contribute to polynya development. We also analyse the Antarctic Mesoscale Prediction System (AMPS) forecast for the studied period and find out that incorrect representation of vertical ABL properties over the TNBP might be caused by overestimated sea ice concentrations (SIC) used as model input. Altogether, this research provides a unique description of TNBP development and its interactions with the atmosphere and katabatic winds.

Phosphorus promoted HZSM-5 zeolites for the coupling transformation of methanol with 1-butene to propylene

Phosphorus promoted HZSM-5 zeolites (P-HZSM-5) were prepared by synthetic methods of incipient wetness impregnation and in situ synthesis, respectively. This was characterized by the means of powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller method (BET), thermogravimetry (TG), and NH3-TPD. The P-HZSM-5 zeolite prepared by incipient wetness impregnation has a large specific surface area and pore size, and the weak acidity is remarkably increased. The catalytic activity of P-HZSM-5 for the coupling transformation of methanol with 1-butene to propylene was investigated. Under the reaction conditions of temperature at 550 °C, pressure at 0.4 MPa, space velocity at 1800 mL/(gcath), and mole ratio of CH3OH/C4H8at 1:1, the conversion of C4H8can reach to 75.8%, and the selectivity and yield of propylene are 42.2% and 31.9%, respectively.

Decrease in the Mode Purity of Microwave Beams in the L-2M Stellarator Peripheral Plasma

The linear coupling (transformation) of two wave modes in a peripheral layer of inhomogeneous plasma confined by a magnetic field is theoretically analyzed. This transformation is a cause of a decrease in the purity of the X-mode introduced into plasma, which is optimum for electron—cyclotron plasma heating at the second harmonic of gyrofrequency. It is shown that the mode purity defect in radiation power under L-2M stellarator conditions can be no more than 6%. An increase in the mode purity defect because of the arbitrarily large steepness of the electron density profile in the peripheral layer appears insignificant.

Intricate partial waves in nuclear scattering

This article is meant as an encomium of the life-span endeavor of Jacques Raynal to relate nuclear scattering density matrices with numerical methods. The mathematical investigations he made involved intricate hypergeometric coupling algebras and transformations. He was among the first to appreciate the general importance of these studies. His efforts over 60 years are most praiseworthy and, for them, Jacques has gained much respect.

Research on key technology and application of flexibility transformation of heating unit to improve clean energy consumption capacity

The electric regulation capacity of heating units has been constantly improving due to the promotion of the heating units? flexibility transformation. This improvement has effectively alleviated the long remained serious wind and light abandonment phenomena in the heating season in China. In this paper, we discussed the key technologies of the low pressure zero output heating mode and bypass heating mode, both of which are widely used in thermo-electric decoupling. Moreover, the coupling transformation of the two heating modes has been successfully realized in a heating unit. The electric regulation capacity of the unit has been greatly improved, from 18.6% before the transformation to 66.7%, and the minimum technical output has been also reduced to 14.2% THA. After the transformation, the unit now is able to provide several heating modes with its operational flexibility greatly improved. By comparing the economical efficiency of these heating modes, we obtained the operation mode with the lowest heat rate. This transformation mode provides a huge grid space for the consumption of clean energy, so it is of positive reference value and exemplary significance in implementing the flexibility transformation of heating units.

Transformation of scalar couplings between Coleman-Weinberg and MS schemes

The Coleman-Weinberg (CW) renormalization scheme for renormalization-group improvement of the effective potential is particularly valuable for CW symmetry-breaking mechanisms (including the challenging case of models with multiple scalar fields). CW mechanism is typically studied using models with classical scale invariance which not only provide a possibility for an alternative symmetry breaking mechanism but also partially address the gauge hierarchies through dimensional transmutation. As outlined in our discussion section, when the couplings are not large, models with CW symmetry-breaking mechanisms have also been shown to naturally provide the strong first-order phase transition necessary for stochastic gravitational wave signals. A full understanding of the CW-MS scheme transformation of couplings thus becomes important in the era of gravitational wave detection and precision coupling measurements. A generalized Coleman-Weinberg (GCW) renormalization scheme is formulated and methods for transforming scalar self-couplings between the GCW and MS (minimal-subtraction) renormalization schemes are developed. Scalar $\ensuremath{\lambda}{\mathrm{\ensuremath{\Phi}}}^{4}$ theory with global $O(4)$ symmetry is explicitly studied up to six-loop order to explore the magnitude of this scheme transformation effect on the couplings. The dynamical rescaling of renormalization scales between the GCW and MS schemes can lead to significant (order of 10%) differences in the coupling at any order, and consequently GCW-MS scheme transformation effects must be considered within precision determinations of scalar couplings in extensions of the Standard Model.

A Co-Phase Traction Power Supply System Based on Asymmetric Three-Leg Hybrid Power Quality Conditioner

Single-phase 25kV AC traction power supply system (TPSS) is widely used for electric power feeders in high-speed rail. Modern locomotives draw a large amount of unbalanced, inductive power from two phases of the grid through the traction transformer and lead to severe problems of voltage unbalance and reactive power existence. These problems are mitigated in the promising co-phase TPSS with the equipment of Railway Power Conditioner (RPC) or Hybrid Power Quality Conditioner (HPQC), in which HPQC can operate with a lower voltage and cost. However, HPQC installation involves the adoption of a bulky and expensive coupling transformer. In this paper, a co-phase TPSS employing asymmetric back-to-back modular multilevel converter (MMC) is proposed and it is named asymmetric three-leg hybrid HPQC (ATHPQC). Through the simulation verifications in this research work, the proposed design can effectively remove the additional and costly step-down coupling transformer, which is required by symmetric HPQC. For comprehensiveness of the ATHPQC design, internal circulating current modeling and analysis are investigated. Control system is implemented, including external compensating current control, internal balancing control and PWM module. ATHPQC is a promising alternative TPSS for next-generation high-speed rail.

On the Wilsonian Meaning of Quantum Error Correction

AbstractWe sketch a recipe to define renormalization group transformations based on Kadanoff‐Wilson block packing using a quantum error correction code. In such a case the RG transformations of the couplings are determined by the error matrix of the QEC code. In order to define the RG transformation of couplings we use Weinberg's sum rule for an error Källen Lehman function. We define an error beta function that for holographic AdS codes is conjectured to be zero. For holographic codes the relation between Weinberg's sum rule for the error Källen Lehman function and bulk locality is briefly discussed.