Large Conversion Research Articles

Design analysis of intelligent controller to minimize harmonic distortion and power loss of wind energy conversion system (grid connected)

<p>The controlling of internal parametric variations in addition to the non-linearity of a large conversion system of wind energy (WECS) is prime challenges to make the most of the generated energy, with less power loss and secure the proficiency (η) integration conventional grid. An adjustable speed control structure of grid-connected conversion system of wind energy (WECS), with the help of a Permanent Magnet Type Synchronous Generator with intelligent controller minimizes the power loss. The control system incorporates a pair of controllers dedicated to the converters of both the generator and grid edge. The controller at the generator side has the main function is to optimize power that can be withdrawal from the wind by intelligently regulating the turbine’s rotational speed. Meanwhile, the grid edge converter effectively manages active and reactive power by manipulating the d & q-axis current components, respectively. This paper discusses about the improvement in performance of the system when using Neuro-Fuzzy system as compared to Neural Network and Management of energy deliver system via direct control method. The findings reveal that the training time for Artificial Neural Networks (ANNs) is substantial, leading to the Neural Network-Direct Power Contol (NN-DPC) approach being the slowest option among the alternatives. Additionally, the NF-DPC system is less time-consuming than the NN-DPC, with a recorded duration of 24 seconds compared to the NN-DPC’s observation of 8 min and 5 s. However, it is worth noting that the NF-DPC system is somewhat more time-intensive than Common-Direct Power Contol (C-DPC).</p>

Generation of ultra-intense vortex laser from a binary phase square spiral zone plate.

With the development of ultra-intense laser technology, the manipulation of relativistic laser pulses has become progressively challenging due to the limitations of damage thresholds for traditional optical devices. In recent years, the generation and manipulation of ultra-intense vortex laser pulses by plasma has attracted a great deal of attention. Here, we propose a new scheme to produce a relativistic vortex laser. This is achieved by using a relativistic Gaussian drive laser to irradiate a plasma binary phase square spiral zone plate (BPSSZP). Based on three-dimensional particle-in-cell (3D-PIC) simulations, we find that the drive laser has a phase difference of π after passing through the BPSSZP, ultimately generating the vortex laser with unique square symmetry. Quantitatively, by employing a drive laser pulse with intensity of 1.3 × 1018~W/cm2, a vortex laser with intensity up to 1.8 × 1019~W/cm2, and energy conversion efficiency of 18.61% can be obtained. The vortex lasers generated using the BPSSZP follow the modulo-4 transmutation rule when varying the topological charge of BPSSZP. Furthermore, the plasma-based BPSSZP has exhibited robustness and the ability to withstand multiple ultra-intense laser pulses. As the vortex laser generated via the BPSSZP has high intensity and large energy conversion efficiency, our scheme may hold potential applications in the community of laser-plasma, such as particles acceleration, intense high-order vortex harmonic generation, and vortex X/γ-ray sources.

High power tunable Raman fiber laser at 1.2 μm waveband

Development of a high power fiber laser at special waveband, which is difficult to achieve by conventional rare-earth-doped fibers, is a significant challenge. One of the most common methods for achieving lasing at special wavelength is Raman conversion. Phosphorus-doped fiber (PDF), due to the phosphorus-related large frequency shift Raman peak at 40 THz, is a great choice for large frequency shift Raman conversion. Here, by adopting 150 m large mode area triple-clad PDF as Raman gain medium, and a novel wavelength-selective feedback mechanism to suppress the silica-related Raman emission, we build a high power cladding-pumped Raman fiber laser at 1.2 μm waveband. A Raman signal with power up to 735.8 W at 1252.7 nm is obtained. To the best of our knowledge, this is the highest output power ever reported for fiber lasers at 1.2 μm waveband. Moreover, by tuning the wavelength of the pump source, a tunable Raman output of more than 450 W over a wavelength range of 1240.6–1252.7 nm is demonstrated. This work proves PDF’s advantage in high power large frequency shift Raman conversion with a cladding pump scheme, thus providing a good solution for a high power laser source at special waveband.Graphical

Comparison between Developing and Nondeveloping Disturbances for Tropical Cyclogenesis in Different Large-Scale Flow Patterns over the Western North Pacific

Abstract This study classifies 407 developing disturbances (DEV) and 2309 nondeveloping disturbances (NONDEV) over the western North Pacific into five large-scale circulation patterns, namely the pre-existing cyclone (PC), easterly wave (EW), zonal wind convergence (CON), zonal wind shear line (SL), and mixed zonal wind convergence and shear line (CON-SL) patterns. The SL pattern has the highest TC yield percentage, followed by the CON-SL, while the EW is the least favorable pattern. The composite analysis shows that upper-level divergence, midlevel relative humidity, and surface heat flux (SHF) growth are crucial to the disturbance development in all the five patterns. Besides, large lower-level barotropic kinetic energy conversion and a well-developed primary circulation are good indicators for disturbance development in the PC, EW, and CON rather than in the SL and CON-SL patterns. Furthermore, for the PC, EW and CON patterns, the DEV features strong and rapidly growing SHF and mesoscale convective systems (MCS) closer to the disturbance center, which allows deep-layer warming and moistening, and drives a deep secondary circulation. Interestingly, due to an environment with high lower-level vorticity, the SL and CON-SL patterns typically foster a relatively mature primary circulation with strong SHF and MCS concentrated close to the center, especially for the NONDEV at the pre-genesis stage. However, a drier mid-to-upper-level environment for the NONDEV inhibits deep convection, which may explain its shallow secondary circulation and therefore poor potential to develop further.

Formulating Local Environment of Oxygen Mitigates Voltage Hysteresis in Li-Rich Materials.

Li-rich cathode materials have emerged as one of the most prospective options for Li-ion batteries owing to their remarkable energy density (>900Wh kg-1). However, voltage hysteresis during charge and discharge process lowers the energy conversion efficiency, which hinders their application in practical devices. Herein, the fundamental reason for voltage hysteresis through investigating the O redox behavior under different (de)lithiation states is unveiled and it is successfully addressed by formulating the local environment of O2-. In Li-rich Mn-based materials, it is confirmed that there exists reaction activity of oxygen ions at low discharge voltage (<3.6V) in the presence of TM-TM-Li ordered arrangement, generating massive amount of voltage hysteresis and resulting in a decreased energy efficiency (80.95%). Moreover, in the case where Li 2b sites are numerously occupied by TM ions, the local environment of O2- evolves, the reactivity of oxygen ions at low voltage is significantly inhibited, thus giving rise to the large energy conversion efficiency (89.07%). This study reveals the structure-activity relationship between the local environment around O2- and voltage hysteresis, which provides guidance in designing next-generation high-performance cathode materials.

Conversations of Hope in a Culture of Crisis

In the late 1990s, linguist Deborah Tannen argued that America had become an “argument culture” characterized by an adversarial frame of mind when approaching the world and the people in it. Recent events appear to have added apocalyptic fears (not entirely unfounded) to our adversarial approach. How can we talk to each other in such a communication climate? The Winsome Conviction Project was launched in early 2020 at Biola University to help improve our conversations both internally and in our community at large. The Winsome Conviction Project encourages civility, but is even more concerned about the effective communication of deeply held convictions. Particularly important is helping people articulate their convictions, including their backstory, reasons, and doubts. We have hosted large public conversations, small group discussions between people with conflicting convictions, and discussion groups that probe contested issues and help people develop well-formed convictions. This paper will: (1) give a short overview of key challenges we faced (both institutionally and culturally), (2) describe how the Winsome Conviction Project engaged and responded to these challenges, and (3) summarize some provisional lessons to be drawn from our experience.

Achievement of a giant electromechanical conversion coefficient in a molecule-based ferroelectric.

Molecule-based ferroelectrics are promising candidates for flexible self-powered power supplies (i.e., piezoelectric generators (PEGs)). Although the large electromechanical conversion coefficients (d 33 × g 33) of piezoelectrics are key to enhancing the performance of PEGs in their nonresonant states, it remains a great challenge to obtain molecule-based piezoelectrics with large d 33 × g 33. Here, we report a molecule-based ferroelectric [(CH3)3NCH2CH2Cl][GaBr4] (1) that exhibits the largest piezoelectric coefficient (∼454 pC N-1) and electromechanical conversion coefficient (4953.1 × 10-12 m2 N-1) among all known free-standing polycrystalline pellets. Notably, the PEG comprising 15 wt% 1 and polydimethylsiloxane (PDMS) achieves a power density of up to 120 μW cm-2, marking the highest reported power density for ferroelectric@PDMS PEGs to date.

Intense Magnetic Reconnection Process Embedded in Three‐Dimensional Turbulent Current Sheet

AbstractRecent magnetospheric observations and three‐dimensional (3D) kinetic simulations have shown that plasma wave activities are significantly enhanced around the reconnection x‐line, implying that the reconnection process is fully 3D. However, how the turbulence affects the local reconnection process has been poorly understood so far. We find by means of large‐scale particle‐in‐cell simulation in 3D system that the local reconnection rate can be significantly enhanced, reaching 0.4, which is much larger than theoretical predictions for two‐dimensional (2D) reconnection. The large reconnection rate is associated with large energy conversion rate and strong electron acceleration. The enhancement of the reconnection rate is caused by local increases of electron momentum transport and pressure gradient force induced by turbulence, which can not occur in 2D system. The result is expected to give better interpretations to in‐situ satellite observations where magnetic reconnection proceeds in 3D system.

Oxidation dynamics of soot or carbon black accounting for its core-shell structure and pore network

Internal oxidation is most important for removal of soot in diesel particulate filters. Furthermore, it enhances the porosity of carbon blacks (CBs), increases their specific surface area, SSA, determining their performance in batteries, inks and tires, as well as their environmental and health impact. Current models for oxidation of soot or CB neglect its fractal-like pore network during internal oxidation and underestimate its SSA by 60 % on average! Here, a lattice Monte Carlo (LMC) model elucidates both external and internal oxidation dynamics of soot (or CB) accounting for its fractal-like pore structure, for the first time to the best of our knowledge. Random internal oxidation takes place at the bulk soot (or CB), expanding its pore network and increasing the pore fractal dimension, Dfp, up to 3, in good agreement with data. This increases the SSA up to a factor of ten at 75 % conversion. In the presence of a less reactive shell though, internal oxidation stops after the reactive core is consumed. Thus the SSA levels off at large conversions (>50 %). Hence, accounting for the realistic core-shell, fractal-like pore structure during simultaneous external and internal oxidation nicely explains several measurements of soot and CB Dfp, SSA and particle diameter. So the LMC-derived oxidation dynamics of soot or CB presented here can be used to assist the design of highly porous CB grades from first principles, as well as the mitigation of soot emissions by enhancing their oxidation.

Contributions to the development of a new family of hybrid DC-DC converters

The paper presents a synthesis of the author contributions in developing a new class of DC-DC hybrid converters (HDC) with large voltage conversion ratio. The HDC structures are obtained by introducing commutated inductive and capacitive cells in the classical DC-DC converters. With these topologies, the voltage conversion ratio is larger, at the same duty cycle, compared with the classical converters. The paper presents some of the developed configurations, with unidirectional and bidirectional power flow, and some corresponding applications in renewable energy conversion and automotive industries.

A 12-bit, 27.8-ps resolution, Anti-PVT variation multi-parallel sampling based coarse-fine TDC for LiDAR sensors

This paper presents a multi-parallel sampling based coarse-fine time-to-digital converter (TDC) with sub-gate delay resolution, large measurement range and high conversion rate for light detection and ranging (LiDAR) sensors. The fine-TDC is designed based on a voltage-controlled delay line (VCDL) but with multi-parallel sampling D flip-flop (DFF) groups to achieve a sub-gate delay resolution based on multi-phase interpolation. These DFF groups are triggered by several successively delayed sampling clocks that generated by a phase-locked loop (PLL) based multi-phase clock generator. The coarse-TDC composed of a coarse counter and a logical control circuit (LCC) is designed to enlarge the measurement range. The LCC is used to calibrate and guarantee the coarse counter neither over-counted nor under-counted. Since the delay of delay units in fine-TDC is also voltage-controlled by another PLL, the resolution of this proposed TDC is robust to process-voltage-temperature (PVT) variation. Besides, this proposed TDC architecture also has the property of dynamic element matching (DEM), which contributes to mitigate the impact of device mismatch and scramble the quantization noise. The post-layout simulations demonstrate a 12-bit, 27.8-ps time resolution, 0.86-LSB DNL, 0.92-LSB INL with 13.6-mW power consumption at 33.3-MS/s under a 1.8-V supply.

Sayan–Yenisei Potential Petroleum Area and Its Resource Potential

Abstract ––This study presents the results of recent regional seismic exploration and deep drilling efforts in the Sayan–Yenisei syneclise and adjacent areas of the Lena–Tunguska petroleum province. These results were used to build a series of structure maps for Riphean, Vendian and Lower Cambrian reflectors; thickness maps of the Riphean and Vendian terrigenous geoseismic sequences within the syneclise, and a tectonic map of the Vendian–Paleozoic structural stage of the Sayan–Yenisei syneclise. The proposed oil and gas geological zoning of the Sayan–Yenisei potential petroleum area enabled us to identify eight potential petroleum regions and perform a quantitative assessment of the hydrocarbon potential. The original in-place resources of the Sayan–Yenisei potential petroleum area are estimated to be 3 billion 231 mln tons of hydrocarbon equivalent, including 3 trillion 39 billion m3 of gas and 192.7 mln tons of condensate. It is shown that over next 15–20 years, up to 1 trillion m3 gas reserves can be explored in the Sayan–Yenisei potential petroleum area. It is proposed to consider the Boguchany village as a large gas conversion and helium production center.

Rational design of promising candidates for photoactive layer in polymer solar cells: Insights from computation

AbstractThe design of organic solar cells, OSCs, requests a more efficient configuration of photoactive layers composed of p‐type (quinoxaline, Qx) and n‐type (naphthalene diimide, NDI) semiconductors that enable light harvesting along with a high‐power conversion efficiency. Here, Qx‐(phenyl or Ph) and NDI structures have been modulated using both electron withdrawing (EWG) and electron donating (EDG) groups such as −F, −NHCOCH3, −OCH3, −OH, −CHO, −COOCH3, −COOH, −CN, −SO3H, and −NO2, aiming to design an effective photoactive p‐n layer. The HOMO‐LUMO gap of Qx‐Ph can be tuned to the visible light spectrum by the addition of EWG in the Qx ring (decreasing the LUMO energy) and by EDG in the Ph ring (increasing the HOMO energy). The analyzed complexes show key electronic properties in organic solar cells with large power conversion efficiency. Descriptive data analysis suggests that the magnitude of the non‐covalent interactions in donor acceptor (D A) complexes is expected to play a role in the efficiency of OSCs. The results will contribute to a more effective design of the photoactive layer in OSCs.

Derivation of Ultra-High Gain Hybrid Converter Families for HASEL Actuators Used in Soft Mobile Robots.

This work proposes, analyzes, designs, and validates superior topologies of UHGH converters that are capable of supporting extremely large conversion ratios up to ∼2000× and output voltage up to ∼4-12 kV for future mobile soft robots from an input voltage as low as the range of a 1-cell battery pack. Thus, the converter makes soft robots standalone systems that can be untethered and mobile. The extremely large voltage gain is enabled by a unique hybrid combination of a high-gain switched magnetic element (HGSME) and a capacitor-based voltage multiplier rectifier (CVMR) that, together, achieve small overall size, efficient operation, and output voltage regulation and shaping with simple duty-cycle modulation. With superior performance, power density, and compact size, the UHGH converters prove to be a promising candidate for future untethered soft robots.

Targeted long-read sequencing for comprehensive detection of CYP21A2 mutations in patients with 21-hydroxylase deficiency.

21-Hydroxylase deficiency (21-OHD) is caused by pathogenic CYP21A2 variations. CYP21A2 is arranged in tandem with its highly homologous pseudogene CYP21A1P; therefore, it is prone to mismatch and rearrangement, producing different types of complex variations. There were few reports on using only one method to detect different CYP21A2 variants simultaneously. Targeted long-read sequencing method was used to detect all types of CYP21A2 variants in a series of patients with 21-OHD. A total of 59 patients with 21-OHD were enrolled from Peking Union Medical College Hospital. Long-range locus-specific PCR and long-read sequencing (LRS) were performed to detect the pathogenic variants in CYP21A2. Copy-number variants of CYP21A2 were found in 25.4% of patients, including 5.1% with 3 copies of CYP21A2, 16.9% with 1 copy of CYP21A2, and 3.4% with 0 copy of CYP21A2. The remaining 74.6% of patients had 2 copies of CYP21A2. Pathogenic variants were identified in all 121 alleles of 59 patients. Specifically, single-nucleotide variants and small insertions/deletions (< 50bp) were detected in 79 alleles, of which conversed from CYP21A1P were detected in 63 alleles, and rare variants were found in the other 16 alleles. Large gene conversions (> 50bp) from pseudogene were detected in 10 alleles, and different chimeric genes (CYP21A1P/CYP21A2 or TNXA/TNXB) formed by large deletions were detected in 32 alleles. Of all variants, p.I173N was the most common variant (19.0%). Our study demonstrated that targeted long-read sequencing is a comprehensive method for detecting CYP21A2 variations, which is helpful for genetic diagnosis in 21-OHD patients.

Soil physicochemical properties and crusts regulate the soil infiltration capacity after land-use conversions from farmlands in semiarid areas

Large scale land-use conversions played important role in regulating the process of soil infiltration, and thus changing soil moisture recharge. However, how the soil properties influence infiltration after farmland conversions remain unclear in the semiarid areas. This study used a double-ring infiltrometer to conduct infiltration experiments in soil surface and subsurface among land-uses on the Loess Plateau, to explore the mechanism of soil physicochemical properties and crusts on infiltration. The results showed that the revegetation lands effectively improved infiltration properties, while no significant differences were observed between the orchards and the farmlands. The loose soil structure, stable aggregates, higher organic matter and root mass density improved while soil crusts impeded infiltration capacity after farmland conversions. The impeding effect of the biocrusts presented throughout the infiltration process while physical crusts impeded infiltration only at the initial stage. Soil physical properties (i.e., bulk density, porosity, macroaggregate, texture, moisture), biochemical properties (i.e., soil organic matter, roots) and crusts were major factors in the variation of the surface (0–20 cm) infiltration properties, while subsurface (20–40 cm) infiltration were mainly influenced by soil physical properties. The deeper soils had a greater impact on steady infiltration rate than initial infiltration rate. Due to the plough pan in agricultural lands, the subsurface soil (20–40 cm) had a strong effect (42.1%) on the steady infiltration rate of the surface (0–20 cm) soil, even close to the surface (0–20 cm) soils (49.8%). These findings improve the comprehensive understanding of the soil hydrological processes after farmlands conversions in semiarid areas.

High-Performance Infrared Detectors Based on Black Phosphorus/Carbon Nanotube Heterojunctions.

Infrared detectors have broad application prospects in the fields of detection and communication. Using ideal materials and good device structure is crucial for achieving high-performance infrared detectors. Here, we utilized black phosphorus (BP) and single-walled carbon nanotube (SWCNT) films to construct a vertical van der Waals heterostructure, resulting in high-performance photovoltaic infrared detectors. In the device, a strong built-in electric field was formed in the heterojunction with a favored energy-band matching between the BP and the SWCNT, which caused a good photovoltaic effect. The fabricated devices exhibited a diode-like rectification behavior in the dark, which had a high rectification ratio up to a magnitude of 104 and a low ideal factor of 1.4. Under 1550 nm wavelength illumination, the 2D BP/SWCNT film photodetector demonstrated an open-circuit voltage of 0.34 V, a large external power conversion efficiency (η) of 7.5% and a high specific detectivity (D*) of 3.1 × 109 Jones. This external η was the highest among those for the photovoltaic devices fabricated with the SWCNTs or the heterostructures based on 2D materials and the obtained D* was also higher than those for most of the infrared detectors based on 2D materials or carbon materials. This work showcases the application potential of BP and SWCNTs in the detection field.

Seed‐Assisted Growth for Scalable and Efficient Perovskite Solar Modules

Perovskite solar modules (PSMs) have shown remarkable photovoltaic potentials, but they still suffer from large power conversion efficiency (PCE) loss on scale‐up and instability due to inferior uniformity and crystallization over large areas. Herein, the scalable production of efficient and stable PSMs using a suite of all‐scalable fabrication methods featuring a two‐step blade/dip‐coating approach to deposit the perovskite absorber layer is demonstrated. Rubidium chloride is introduced to embed (PbI2)2RbCl complex seeds in the first‐deposited PbI2 precursor, which assists in uniform crystallization of the perovskite layer with high crystallinity and reduced defect density over large areas. Following the optimization of RbCl additives, a champion PSM with 17.9% PCE on a 7.6 × 7.6 cm2 substrate with a 37 cm2 aperture area is achieved. Moreover, the RbCl‐incorporated PSMs demonstrate excellent reproducibility and stability under continuous 1 sun illumination. This work shows that the two‐step blade/dip coating is a promising method for producing high‐efficiency and stable PSMs on an industrially relevant scale.

Cobalt and iron metallates as catalysts for cyclization reactions of diynes and triynes: [2+2+2] Cycloaddition vs. Garratt-Braverman reaction

Highly reduced anthracene and naphthalene cobaltates and ferrates catalyze the cyclization of diynes and triynes, furnishing expected [2 + 2 + 2] cycloaddition products as well as unexpected annulation products from Garratt-Braverman cyclization reactions. The anionic Cp*Fe-naphthalene complex exclusively catalyzes the latter reaction. The Garratt-Braverman reactions show a large solvent-dependent substrate conversion. Diynes and triynes afforded the corresponding substituted 1,3-dihydronaphthofurane products with yields up to 91% isolated yield.

New Insights into Urea Electro-Oxidation: Complete Mass-Balances and Proof of Concept with Real-Matrix Effluent

In the present work, all the by-products formed during the urea electrooxidation (UEO) by Ni(III) in alkaline medium are identified and quantified for the first time (e.g., ). Complete mass balances are simultaneously established in both aqueous and gas phases for large urea conversion rates (>80%). The results provide clear evidence (with a maximal deviation of 2%) that, in addition to N-overoxidized by-products are produced during the UEO. Electrolyses conducted with human urine samples under identical operating conditions result in different distributions of N and C-by-products. In particular, the formation of formic and oxalic acids in these latter experiments suggests the presence of different and/or additional mechanistic pathways during the UEO process. The amount of generated at the cathode is also quantified, showing a reduction of 30% in energy consumption when compared with water electrolysis. Finally, this study assesses the energy efficiency of UEO with urea synthetic and real-matrix effluents, thereby contributing to the development of this sustainable process, which enables energy recovery from waste.