Z-source matrix rectifier

This paper presents a novel Z-source matrix rectifier(ZSMR). To overcome the inherent disadvantage that the voltage transfer ratio for traditional matrix rectifier cannot be more than 0.866, a Z-source network has been combined with the matrix rectifier. The proposed rectifier realizes a voltage-boost function and the Z-source network also serves as power storage and guarantees double filtration grade at the output of the rectifier. The open-circuit zero state is required to obtain the voltage-boost function and ensure the output angle of the current vector to be invariant to obtain the expected power factor. In addition, to widely extend the voltage transfer ratio of the proposed rectifier, this paper presents the switched-inductor matrix rectifier(SL-ZSMR) and tapped-inductor matrix rectifier(TL-ZSMR). The corresponding circuit topologies, control strategies and operating principles are introduced. Both simulation and experiment results are shown to verify the theoretical analysis

High Step-Up Dual-Switch X-Source DC-DC Converters Integrating Various Capacitor-Winding-Diode Voltage-Double Technology

In this article, a new class of high step-up dual-switch X-source dc–dc converters integrating various capacitor-winding-diode voltage-double technology is presented, which are parallel-winding dual-switch X-source dc–dc converters, series-winding dual-switch X-source dc–dc converters, and flipped parallel-winding dual-switch X-source dc–dc converters. According to different winding homonymous end connections, voltage gains and turn ratios of proposed converters have two relations: inversely proportional relations and positive proportional relations. Also, all proposed topologies can produce the higher voltage gain, and own the lower voltage stresses. Operation principles, math derivations, and performance advantages of the proposed converters are analyzed in detail. Finally, the experimental prototype is built to demonstrate the operational feasibility of the proposed converter

An Improved Coupled-Inductor Impedance Source Network With More Freedom in Winding Match

In this paper, an improved coupled-inductor impedance source network (CL-ISN) with more freedom in winding match is proposed. Through introducing three-winding coupled-inductor cells, the proposed CL-ISN can produce the same voltage gain by using different turn ratios among three windings, which will largely increase the freedom in winding match. Also, the proposed CL-ISN can produce the higher boost ability, realize the continuous input current and suppress the start-up inrush current. The topology derivations, math calculations and parameter design of proposed CL-ISN are given out. The proposed CL-ISN is applied for DC-AC converter, and a full comparison between proposed CL-ISN and other impedance source networks are made based on DC-AC converter. Finally, the experiment prototype is built to verify the validity of the theoretical analysis

Machine Learning Estimation of Reaction Energy Barriers and its Applications in Astrochemistry

We developed a machine learning model for fast estimating reaction energy barriers. The model was trained on data for 11,730 elementary reactions and barriers computed with an estimated accuracy of 2.3 kcal/mol by Grambow and coworkers. Although it was trained, and then applied, only for reactions involving atoms of H, C, N and O, our model can readily be generalized to molecules and reactions involving other elements. We designed and tested many molecular representations. Our best model has 363 features calculated from the chemical composition, structure, and energy of products and reactants that can all be obtained at a small computational cost. A Kernel Ridge Regression with Laplacian kernel was found to give the best fit to the data. It makes predictions with a mean absolute error of 4.1 kcal/mol for barriers smaller than 40 kcal/mol. We used this machine learning model to estimate the barriers of 136,081 hypothetical association reactions between molecules known to exist in the circumstellar envelopes and interstellar medium, where temperatures range between 10 and 150 K. A screening procedure identified reactions likely to occur (those with near zero barriers) that could play a role in the formation of relatively complex organic molecules (those with at least one double bond and containing at least one atom each of the elements H, C, N and O). Reactions identified as the most promising were investigated with density functional theory and coupled cluster quantum chemical methods to obtain reaction pathways and energies of reactants, intermediates, transition states and products with an accuracy of roughly 1 kcal/mol. We found no barrierless reaction but found two reactions with low barriers leading to the formation of N-methyleneformamide (CH2NCHO) and imine acetaldehyde (NHCHCHO). These molecules have not yet been observed in space. The low barriers that we calculated, and the possibility that these reactions would be facilitated by adsorption on ice covered dust grains in the interstellar medium, suggest that these two molecules may exist in space and could be detected by determinations of rotational constants from spectroscopic lines in the microwave region

Computational Study of the Reactions of Interstellar Molecules: CH2 Reacting with HCNO and HNCO

Association reactions among small molecules known to exist in the interstellar medium are interesting for theories on the origins of life. A screening of thousands of reactions, using machine learning estimates of energy barriers, identified the reaction of CH2 with HCNO and HNCO as particularly interesting. We report reaction mechanisms, including energies of transition states and products, computed with density functional theory and coupled cluster theory. The lowest energy pathway on the triplet ground state surface of CH2 + HNCO has a barrier of 11 kcal/mol and produces CH2(CO)NH. Singlet CH2 is 9 kcal/mol above the ground state. It can react with HCNO or HNCO without barrier giving four products: CH2NCHO, N-methyleneformamide, the thermodynamically favoured product; NHCHCHO; NHCHOCH; and (CH2OC)NH, oxiran-2-ylazanide. If triplet to singlet crossing occurs, an upper bound of roughly 10 kcal/mol is implied for the barrier to formation of these four products

Enhanced Formaldehyde Removal from Air Using Fully Biodegradable Chitosan Grafted β-Cyclodextrin Adsorbent with Weak Chemical Interaction

Formaldehyde (HCHO) is an important indoor air pollutant. Herein, a fully biodegradable adsorbent was synthesized by the crosslinking reaction of β-cyclodextrin (β-CD) and chitosan via glutaraldehyde (CGC). The as-prepared CGC showed large adsorption capacities for gaseous formaldehyde. To clarify the adsorption performance of the as-synthesized HCHO adsorbents, changing the adsorption parameters performed various continuous flow adsorption tests. It was found that the adsorption data agreed best with the Freundlich isotherm, and the HCHO adsorption kinetic data fitted well with the pseudo second order model. The breakthrough curves indicated that the HCHO adsorbing capacity of CGC was up to 15.5 mg/g, with the inlet HCHO concentration of 46.1 mg/m3, GHSV of 28 mL/min, and temperature of 20 °C. The regeneration and reusability of the adsorbent were evaluated and CGC was found to retain its adsorptive capacity after four cycles. The introduction of β-CD was a key factor for the satisfied HCHO adsorption performance of CGC. A plausible HCHO adsorption mechanism by CGC with the consideration of the synergistic effects of Schiff base reaction and the hydrogen bonding interaction was proposed based on in situ DRIFTS studies. The present study suggests that CGC is a promising adsorbent for the indoor formaldehyde treatment