Structural Conversion Research Articles

A Centralized Shifted Power Control Scheme for Isolated Bidirectional DC-DC Converter in Standalone DC Distribution System

When parallel converter structures are considered in modern DC distribution systems, several challenges are faced in the energy management system (EMS). For example, the circuit parameter mismatches of parallel isolated DC-DC converter modules will cause power imbalances, which is the most important concern in DC distribution system. To deal with this issue, this study presents a power management control scheme in the EMS to ensure the power balance of isolated DC-DC converters in DC distribution system. In the proposed method, the proposed shifted voltage is introduced at the output of each converter to compensate the output impedance mismatches. Especially, the shifted voltage is flexibly determined according to the output current sharing error to obtain a balanced output impedance among converters, and the balanced power sharing is achieved by means of the modified voltage reference. The simulation results with the stand-alone DC distribution system are carried out to verify the effectiveness of the proposed control scheme.

A FPGA based PI adaptive sliding mode controller for PEM fuel cell with boost converter

Proton exchange membrane (PEM) is one of the most popular fuel cells for renewable energy production, and this paper presents a DC/DC boost converter structure to improve energy efficiency. To achieve high output power as well as constant output voltage, a combined method consisting of proportional-integral controller and adaptive sliding mode technique is designed. Also, due to the use of adaptive technique, the proposed technique has the ability to cover the effects of uncertainty with an unknown high limit and in addition to improving the quality of output power and voltage of PEM, it eliminates permanent tracking error and guarantees closed loop system stability. To show the operational implementation capability and flexibility of the method, FPGA has been used, which in addition to showing real-time performance, provides the ability to execute the controller at high speeds. Operationality and the possibility of practical implementation of the planned scheme on the existing systems provide the possibility of increasing the efficiency of energy extraction without further investment. The stability of the closed-loop system is achieved using Lyapunov technique and the results of simulation and comparison indicate the optimal performance of the system under the planned scheme and high efficiency in comparison with existing approaches.

Pathological structural conversion of α-synuclein at the mitochondria induces neuronal toxicity

Aggregation of alpha-synuclein (α-Syn) drives Parkinson’s disease (PD), although the initial stages of self-assembly and structural conversion have not been directly observed inside neurons. In this study, we tracked the intracellular conformational states of α-Syn using a single-molecule Förster resonance energy transfer (smFRET) biosensor, and we show here that α-Syn converts from a monomeric state into two distinct oligomeric states in neurons in a concentration-dependent and sequence-specific manner. Three-dimensional FRET-correlative light and electron microscopy (FRET-CLEM) revealed that intracellular seeding events occur preferentially on membrane surfaces, especially at mitochondrial membranes. The mitochondrial lipid cardiolipin triggers rapid oligomerization of A53T α-Syn, and cardiolipin is sequestered within aggregating lipid–protein complexes. Mitochondrial aggregates impair complex I activity and increase mitochondrial reactive oxygen species (ROS) generation, which accelerates the oligomerization of A53T α-Syn and causes permeabilization of mitochondrial membranes and cell death. These processes were also observed in induced pluripotent stem cell (iPSC)–derived neurons harboring A53T mutations from patients with PD. Our study highlights a mechanism of de novo α-Syn oligomerization at mitochondrial membranes and subsequent neuronal toxicity.

Front Cover: Metal‐Organic‐Frameworks and Their Derived Materials in Photo‐Thermal Catalysis (Eur. J. Inorg. Chem. 28/2022)

The Front Cover shows the two routes in which metal-organic frameworks (MOFs) can participate in photo-thermal reactions. In the case of MOF-based composites, MOFs can act as hosts for plasmonic metal nanoparticles that, upon irradiation, are able to drive chemical reactions through high-energy electrons and/or thermal enhancement. In the case of MOF-derived materials, MOFs play a role as sacrificial templates to create new materials based on highly dispersed metal nanoparticles embedded into a carbon matrix. These latter materials benefit from the outstanding light-to-heat conversion and broadband absorption of carbon structures. Both approaches mentioned above represent promising pathways for the implementation of MOFs as photo-thermal catalysts for the production of solar fuels and chemicals. More information can be found in the Review by J. Gascon and co-workers.

Unsteady flow analysis regarding stall flow and rotating cavitation in the first-stage of a multistage LNG cryogenic submerged pump

In this paper, the evolution of vortex structure and energy conversion process under the coupling of stall and cavitation flow (CSC) in the first-stage of a multistage LNG cryogenic submerged pump are numerically studied in detail, using a time-scale-driven hybrid URANS/LES turbulence model and a mushy interfacial dynamics cavitation model. The flow instability diagnostic parameter, PVS, is then established combining the first and second laws of thermodynamics. Further, the dynamic behaviors under CSC are analyzed by Liutex method and the fluctuations of vortex intensity are investigated in time-frequency domain. Results show that compared with the oscillation process of the pump head, PVS is more intuitive to depict the stall state. It is treated as light and deep stall as PVS drops to 0.2 and 0.15, while PVS is further reduced and finally locks at about 0.12. For the above conditions, vortices at the inlet section involves high-frequency cavity-shedding vortex and low-frequency impact vortex. The middle separation region absorbs the upstream shedding vortex and transports the separation vortex downstream, whereas vortices with the highest intensity locates at the outlet diffusion section in the helical shape. Among the vortex-vortex interaction, broadband oscillations get more significant under CSC.

КОМБІНОВАНА ТРАНСФОРМАТОРНО-КЛЮЧОВА ВИКОНАВЧА СТРУКТУРА ДВОФУНКЦІЙНОГО ПЕРЕТВОРЮВАЧА З ДИСКРЕТНО-РАЗОВИМ КЕРУВАННЯМ

Power supply systems with transformer-and-switches executive structures have a prominent place in the power supply systems of electrical and electro technological equipment. Voltage converters based on them with discrete-time control of semiconductor switches are characterized by high energy performance and the absence of distortions in the operating states of the output voltage and input current. The constant increase in the range and number of electricity consumers that require the use of such converters for their standardized operation, encourages their appropriate improvement, in particular to expand functionality. The peculiarities of forming a combined transformer- and-switches executive structure of a two-function converter for a rectified current power supply system, which is characterized by increased efficiency of semiconductor devices and lower losses in them, are investigated. Possible and expedient ranges of regulation of output voltage of such converters are defined. References 12, tables 2, figures 4.

Developing efficient dye-sensitized solar cells by inclusion of ferrocene and benzene π-bridges into molecular structures of triphenylamine dyes

Two triphenylamine (TPA)-based D─π─A sensitizers have been introduced with benzene (B) and ferrocene (Fc) π-bridges which were named as TPA-diazo-B and TPA-diazo-Fc for comparing their ability to find better insight about relation between dye structure and power conversion efficiency (PCE) of dye sensitized solar cells (DSSCs). The optical, electrochemical, interfacial and photovoltaic (PV) properties of these dyes revealed that replacing the B π-bridge with Fc not only provides bathochromic shift in absorption wavelength, but also tunes the band gap (Eg) to the smaller value. In consistent with these observations, PV characteristics of TPA-diazo-Fc sensitized devices (JSC = 1 4.60 mA cm−2, VOC = 652.26 mV, FF = 57% and PCE = 5.42%) were better than DSSCs that used the TPA-diazo-B (JSC = 12.91 mA cm−2, VOC = 619.15 mV, FF = 55% and PCE = 4.46%) for sensitization. Inclusion of a Fc π-bridge improves the intramolecular charge transfer (ICT) from donor (D) to acceptor (A) in dye structure. The main reason for such great ICT is presence of quantum interference effects (QIEs) in Fc π-bridge that facilitates the single molecule conductance of TPA-diazo-Fc dye in comparison to TPA-diazo-B. This study revealed a new horizon in molecular engineering of dyes for developing DSSCs with better performance.

Multiscale Functional Metal Architectures by Antibody‐Guided Metallization of Specific Protein Assemblies in Ex Vivo Multicellular Organisms

Biological systems consist of hierarchical protein structures, each of which has unique 3Dgeometries optimized for specific functions. In the past decades, the growth of inorganic materials on specific proteins has attracted considerable attention. However, the use of specific proteins as templates has only been demonstrated in relatively simple organisms, such as viruses, limiting the range of structures that can be used as scaffolds. This study proposes a method for synthesizing metallic structures that resemble the 3D assemblies of specific proteins in mammalian cells and animal tissues. Using 1.4 nm nanogold-conjugated antibodies, specific proteins within cells and ex vivo tissues are labeled, and then the nanogold acts as nucleation sites for growth of metal particles. As proof of concept, various metal particles are grown using microtubules in cells as templates. The metal-containing cells are applied as catalysts and show catalytic stability in liquid-phase reactions due to the rigid support provided by the microtubules. Finally, this method is used to produce metal structures that replicate the specific protein assemblies of neurons in the mouse brain or the extracellular matrices in the mouse kidney and heart. This new biotemplating approach can facilitate the conversion of specific protein structures into metallic forms in ex vivo multicellular organisms.

Bi12O17Cl2 with a Sextuple BiO Layer Composed of Rock‐Salt and Fluorite Units and its Structural Conversion through Fluorination to Enhance Photocatalytic Activity

AbstractLayered bismuth oxyhalides with bilayered (Bi2O2) fluorite (FL) slabs are promising visible‐light photocatalysts because of their excellent stability and the ability to adjust band levels depending on the layers combined. It is interesting to manipulate the Bi2O2 slab itself, but only trilayered FL blocks (e.g., Bi3O4) are reported so far. Here, a structurally uncharacterized Bi12O17Cl2, which is extensively studied as a photocatalyst for a variety of reactions, has a sextuple Bi6O8.5 block separated by Cl is shown. Unlike double and triple layered cases, the inner region of the Bi6O8.5 block contains 1D rock‐salt (RS) units in the FL matrix along the a‐axis, causing in‐plane corrugation. A topochemical reaction involving anion‐exchange gives Bi12O17–0.5xFxCl2 (x ≤ 6) with alternate FL and RS slabs along the c‐axis. The elimination of the structural corrugation increases higher photo‐conductivity and improves photocatalytic activity against acetic acid decomposition under visible light irradiation. This study paves new opportunities of controlling the properties of layered bismuth oxyhalides by the thickness of Bi–O block, FL/RS configuration, and structural modulation.

Real-Time Optimization-Based Reference Calculation Integrated Control for MMCs Considering Converter Limitations

The paper addresses a real-time optimization-based reference calculation integrated with a control structure for Modular Multilevel Converters (MMC) operating under normal and constrained situations (where it has reached current and/or voltage limitations, as it may occur during system faults). Firstly, a nonlinear optimization problem has been developed in which it prioritizes to satisfy the AC grid current set-points imposed by the transmission System Operator (TSO). The constrained nonlinear optimization problem is formulated based on the steady-state model of the MMC, whereby the prioritization is achieved through distinct weights defined in the Objective Function’s (OF) terms. The resultant optimization problem, however, is highly nonlinear requiring high computation burden to be solved in real-time. To cope with this issue, this paper applies a Linear Time-Varying (LTV) approximation, which permits to represent the nonlinear dynamics of the system as constant parameters, while a Linear Time-Invariant (LTI) system is used to formulate the optimization constraints. The converter’s current references are determined in real-time by solving a constrained linearized optimization problem at each control time step, which considers the TSO’s demands, the current MMC operating point and its physical limitations. Theoretical analyses comparing the responses of the linear and nonlinear optimization problems are performed to validate the accuracy of the LTV approximation. Finally, the linearized-optimization problem is integrated with the MMC controllers, evaluated under different AC and DC network conditions and compared with conventional control strategies, where it is shown that the presented method can be potentially employed to obtain the MMC current references for distinct network scenarios.

Improvement and Analysis of Phase-Phase Failure of Double Feed Induction Generator Using Maximum Power Monitoring Method

This study presents an analysis and control method for the doubly fed induction generator (DFIG) based wind energy production under the conditions of sudden grid voltage dips. The control aims are as follows: limiting the rotor currents, suppressing the fluctuations in the torque and suppressing the dc-link voltage fluctuation via the converter controls and ensuring maximum power point tracking. Rotor side converter (RSC) and grid side converter (GSC) structures have been given in the article and their limitations have been specified. Maximum power tracking control block has also been included in the system and its structure has been given. In this study; while RSC is controlled in a way that it will suppress the fluctuations in the torque and rotor currents, GSC is controlled in a way that it will suppress the fluctuations in dc-link voltage while taking the rotor power impact into consideration. Crowbar unit has been used in the rotor side to minimize these impacts. This unit is activated at the moment when a grid dip occurs and deactivates the RSC side. In this way, RSC side will not be affected by the high current fluctuations. The detailed results of the study were carried out in the MATLAB/Simulink environment,and the effectiveness of the proposed method was supported by the graphic results.

Design of High-Power Solid-State Transformers with Grain-Oriented Electrical Steel Cores

The paper proposes a simple structure of high-power solid-state transformers (SSTs) able to control the energy flow in critical lines of the medium-voltage (20 kV) distribution grid. With an increasing number of renewable intermittent sources connected at the nodes of the meshed distribution grid and a reduced number of nodes connected to large power plants, the distribution grid stability is more and more difficult to achieve. Control of the energy flow in critical lines can improve the stability of the distribution grid. This control can be provided by the proposed high-power SSTs operating a 20 kV with powers over 10 MW. This function is difficult to achieve with standard SST technologies that operate at high frequencies. These devices are made with expensive magnetic materials (amorphous or nanocrystalline cores) and a limited power by SST cells. The required total power is reached by assembling many SST cells. On the other hand, existing SST designs are mainly aimed at reducing the equipment’s size and it is difficult to design small objects able to operate at high voltages. The authors propose to use cores made with grain-oriented electrical steel (GOES) thin strips assembled in wound cores. Experimental results obtained, with GOES wound cores, show that the core losses are lower for a square voltage than for a sine one. This counterintuitive result is explained with an analytical calculus of eddy currents and confirmed by a non-linear time-stepping simulation. Therefore, simple converter structures, operating with rectangular voltages and low switching losses, are the best solutions. Experimental results also show that the core losses decrease with temperature. Consequently, high-power SST cells can be made with transformers whose GOES cores are hotter than coils for reducing core losses and keeping copper losses at low levels. The paper proposes an appropriate transformer mechanical structure that avoids any contact between the hot GOES wound core and the winding, with a specific cooling system and thermal insulation of the hot GOES wound core. The proposed design makes it possible to build SST cells over 1MW and full SSTs over 10 MW at moderate costs.

Crosslinking control of hydrophobic benzoxazine-based hybrid sol-gel coating for corrosion protection on aluminum alloys

Benzoxazine (Bz)-based hybrid sol-gel coating (TEOS-PBz) was prepared by compositing benzoxazine functional silane and Tetraethoxysilane (TEOS) and its distinct crosslinking structures were controlled by a designed curing procedure. The coatings' structures were analyzed by Fourier transform infrared spectroscopy, X-ray photoelectron spectrums and differential scanning calorimetry. It is evident that a prolonged curing procedure could promote curing of Bz functionality completely with high crosslinking degree in the coating, which is a key factor to the coatings' corrosion resistance. The hydrophobicity of the coating is also taken into account as this is also one of the factors affecting the corrosion protection performance. According to the result of electrochemical impedance spectroscopy, the TEOS-PBz with the maximum static water contact angle of 105.6 ± 0.4° showed the highest impedance with the value of Rct above 105 Ω after being immersed in 3.5 wt% NaCl aqueous solution for one week, more than one order of magnitude higher than traditional Tetraethoxysilane-Glycidoxypropyltriethoxysilane (TEOS-GPTES) hybrid sol-gel coating. It is possible to conclude that complete curing crosslinking structure with the conversion of Bz structure >94 % and high hydrophobicity contributed by less intermolecular hydrogen bonding ratio in the coating presented better corrosion protection performance.

Investigation of the Mechanism of 60Co Gamma-Ray Irradiation-Stimulated Oxidation Enhancing the Antigenicity of Ovalbumin by High-Resolution Mass Spectrometry.

60Co gamma-ray irradiation-induced antigenicity changes in ovalbumin (OVA) were investigated, and the molecular mechanism was analyzed. Irradiation treatment at 0-100 kGy could significantly enhance the IgG/IgE binding ability of OVA in a dose-dependent paradigm by concomitant oxidative modification, which exhibited color browning and an increase in carbonyl content caused by high-penetrable rays. More allergenic epitopes of OVA were exposed after irradiation treatment reflected by structural changes including the unfolding of tertiary structure, the conversion of α-helix structures to β-sheet and random coil structures, and the cleavage of several peptide bonds. Meanwhile, three oxidation sites of K46, T49, and N260 located in key linear epitopes were observed, which might increase the allergenic ability of OVA via the disaggregation of noncovalent bonds and the unwinding of α-helix structures. Conclusively, irradiation may enhance the potential allergenicity of OVA by oxidative modification, which provides theoretical guidance for effectively controlling the oxidation of proteins in the irradiation process.

Investigation on the mechanism of carbon structural evolution of Huolinhe lignite during different pretreatment processes

The depth understanding of the organic structure characteristics of coal and its evolution is beneficial to the clean and efficient coal directional conversion. This research probes the evolution path and mechanism of carbon structure of lignite during the hydrothermal transitions dewatering (HTD) and tetralin solvent thermal transitions dewatering (TTD). The structural evolution with these two transitions was explored using 13C NMR and XRD in an autoclave at different temperatures. The moisture content in lignite is effectively decreased during HTD and TTD processes, and this is mainly due to the removal of O-containing functional groups and the decrease of water holding capacity. The TTD process is achieved a higher dehydration and deoxidation for lignite compared with HTD process. This is possibly due to that the dehydrating energy of TTD process not only comes from the thermal energy, but also the tetralin is more likely to form hydrogen bonds with water. The aromaticity is increased during HTD and TTD processes, and this increase is possibly contributed by aromatization while the contribution of aromatic rings condensation was limited because the molar ratio of aromatic bridgehead carbon has changed little. Also, from the XRD data, the stacking of aromatic structural units are significantly promoted and are not obvious for the lateral extended size for crystal structural evolution during HTD and TTD processes. when the pretreatment temperature was at 310 °C, the aromaticity increase from 60.94% to 69.50% and 69.68% during HTD and TTD processes, respectively. The stacking height increase from 8.94 Å to 12.06 Å and 13.27 Å, and the stacking number increase from 2.49 to 3.51 and 3.86, the lateral sizes have changed little. The increase of aromaticity is finally manifested in aromatic units vertical stacking height and stacking layer number. These results indicate that the graphitization and ordering are promoted to some degree during HTD and TTD processes. Compared with the HTD, the TTD had the greater impact on the conversion of lignite carbon structure to high-rank coal. Those results are potentially useful to the clean and efficient utilization of lignite.

Spatiotemporal Heterogeneity Monitoring of Cropland Evolution and Its Impact on Grain Production Changes in the Southern Sanjiang Plain of Northeast China

High-speed cropland changes are taking place in Northeast China, bringing about the sustainable changes in ecological landscape and food production; however, the lack of continuous research limits the revelation of new findings in this region. The integrated approach of land migration tracking, ecological landscape and mathematical statistics was established to conduct a comprehensive survey of land change–landscape–food security in a typical grain-planting region of Northeast China to reveal new changes from 1990 to 2020. Results display that the cropland area continued to increase from 25,885.16 km2 in 1990 to 31,144.46 km2 in 2020, leading to the loss of forest land, grassland, water body and unused land. For cropland structure, the proportion of paddy fields in cropland increased rapidly from 7.18 to 39.53% during 1990–2020; in contrast, upland crops decreased sharply. The richness of landscape presented gradually complex characteristics with SHDI from 0.258 to 0.671 and other ecological indicators underwent similar changes with strong regularity. Total grain production displayed a continuous increase, with values from 523.79 × 104 t to 1839.12 × 104 t, increasing by 2.51 times from 1990 to 2020. We also revealed the contribution rate of unchanged upland crops to grain increments was the largest (i.e., 46.29%), and the conversion of internal cropland structure (i.e., the paddy fields converted from upland crops) contributed 12.17% from 1990 to 2020, showing a positive signal for food security. These new findings provide studies on land use change, ecological landscape and food security in China and abroad.

Improved Predictions of Organic Photovoltaic Performance through Machine Learning Models Empowered by Artificially Generated Failure Data

The conventional development of organic photovoltaic (OPV) materials has been driven by the inspiration and continuous endeavors of experimentalists, whereas machine learning (ML) approaches enable extremely high-throughput data processing. However, the predictive accuracy of ML currently remains insufficient for the design of OPV semiconductors that exhibit a complex connectivity between chemical structure and power conversion efficiency (PCE). In this study, we examined the impact of data selection and the introduction of artificially generated failure data on ML predictions of polymer/non-fullerene, small-molecular-acceptor (NFA) solar cells. We demonstrated that an ML model empowered by artificially generated failure data (∼0% PCE by insoluble polymers based on an inappropriate choice of solubilizing side alkyl chains) led to improved predictions. This approach was validated through the synthesis and characterization of twelve polymers (benzothiadiazole, thienothiophene, or tetrazine coupled with benzodithiophene; benzobisthiazole coupled with dioxo-benzodithiophene). Our work offers a facile approach to mitigate the difficulties of the ML-driven development of OPV materials that is also readily applicable to other material science fields.

A pH‐Driven Small‐Molecule Nanotransformer Hijacks Lysosomes and Overcomes Autophagy‐Induced Resistance in Cancer

AbstractSmart conversion of supramolecular structures in vivo is an attractive strategy in cancer nanomedicine, which is usually achieved via specific peptide sequences. Here we developed a lysosomal targeting small‐molecule conjugate, PBC, which self‐assembles into nanoparticles at physiological pH and smartly converts to nanofibrils in lysosomes of tumor cells. Such a transformation mechanically leads to lysosomal dysfunction, autophagy inhibition, and unusual cytoplasmic vacuolation, thus granting PBC a unique anticancer activity as a monotherapy. Importantly, the photo‐activated PBC elicits significant phototoxicity to lysosomes and shows enormous advantages in overcoming autophagy‐caused treatment resistance frequently occurring in conventional phototherapy. This improved phototherapy achieves a complete cure of oral cancer xenografts upon limited administration. Our work provides a new paradigm for the construction of nonpeptide nanotransformers with biomedical activities.

A pH-Driven Small-Molecule Nanotransformer Hijacks Lysosomes and Overcomes Autophagy-Induced Resistance in Cancer.

Smart conversion of supramolecular structures in vivo is an attractive strategy in cancer nanomedicine, which is usually achieved via specific peptide sequences. Here we developed a lysosomal targeting small-molecule conjugate, PBC, which self-assembles into nanoparticles at physiological pH and smartly converts to nanofibrils in lysosomes of tumor cells. Such a transformation mechanically leads to lysosomal dysfunction, autophagy inhibition, and unusual cytoplasmic vacuolation, thus granting PBC a unique anticancer activity as a monotherapy. Importantly, the photo-activated PBC elicits significant phototoxicity to lysosomes and shows enormous advantages in overcoming autophagy-caused treatment resistance frequently occurring in conventional phototherapy. This improved phototherapy achieves a complete cure of oral cancer xenografts upon limited administration. Our work provides a new paradigm for the construction of nonpeptide nanotransformers with biomedical activities.

Tracking carrier and exciton dynamics in mixed-cation lead mixed-halide perovskite thin films

Mixed-cation lead mixed-halide perovskites simultaneously possess structural stability and high power conversion efficiency. A thorough study of both carrier and exciton dynamics is needed to understand the photophysical properties that underpin its superior photovoltaic performance. By utilizing a broadband transient absorption spectroscopy, we observe the carrier and exciton dynamics in a FA0.85Cs0.15Pb(I0.97Br0.03)3 (FCPIB) perovskite by simultaneously resolving the carrier and exciton contribution to the transient change of the absorption spectra, from which the carrier density and exciton oscillator strength can be determined. Our data reveal a quick and significant conversion of the photogenerated carriers to excitons, on top of the usual carrier recombination process. Moreover, the decay of carrier density shows a change of kinetics from a second-order recombination at high pump fluence to a third-order recombination at low pump fluence. Our analysis utilizes band anharmonicity, presents an independent determination of electronic temperature and quasi-Fermi energy, and reveals an interesting interplay among the processes of carrier cooling, exciton formation/decay and carrier recombination, all as a function of time after photoexcitation. Our work demonstrates the use of pump fluence as a knob to tune the relative populations of carriers and excitons in halide perovskite materials.