Carbon‐based heteroatom‐coordinated single‐atom catalysts (SACs) are promising candidates for energy‐related electrocatalysts because of their low‐cost, tunable catalytic activity/selectivity, and ...relatively homogeneous morphologies. Unique interactions between single metal sites and their surrounding coordination environments play a significant role in modulating the electronic structure of the metal centers, leading to unusual scaling relationships, new reaction mechanisms, and improved catalytic performance. This review summarizes recent advancements in engineering of the local coordination environment of SACs for improved electrocatalytic performance for several crucial energy‐convention electrochemical reactions: oxygen reduction reaction, hydrogen evolution reaction, oxygen evolution reaction, CO2 reduction reaction, and nitrogen reduction reaction. Various engineering strategies including heteroatom‐doping, changing the location of SACs on their support, introducing external ligands, and constructing dual metal sites are comprehensively discussed. The controllable synthetic methods and the activity enhancement mechanism of state‐of‐the‐art SACs are also highlighted. Recent achievements in the electronic modification of SACs will provide an understanding of the structure–activity relationship for the rational design of advanced electrocatalysts.
Carbon‐based heteroatom‐coordinated single‐atom catalysts are promising candidates for energy‐conversion related electrocatalysts. This review summarizes the recent advancements in the engineering of carbon‐based heteroatom‐coordinated single metal site catalysts for energy‐related electrochemical reactions, including the oxygen reduction reaction, hydrogen evolution reaction, oxygen evolution reaction, CO2 reduction reaction, and nitrogen reduction reaction.
This paper proposes and discusses the aerodynamic retrofit design schemes for a multistage high pressure axial compressor. A high hub/tip ratio mixed-flow compressor is designed and analyzed to ...replace the rear stage of the axial compressor. In order to minimize the axial dimension and maximize the load capacity, three unconventional types of combined compressors equipped with the high hub/tip ratio mixed-flow compressor are explored. Further, the effects of blade number, splitter blades and dimensionless geometric parameters on the mixed-flow compressor performance are investigated by an improved loss model. A full-surface parameterization control method is introduced and adopted for blade optimizations of the mixed-flow impeller and the tandem stator. The results indicate that after aerodynamic improved design and optimization, the total pressure ratio is relatively improved by 3.71% and the adiabatic efficiency is improved by 0.95 percent point for the mixed-flow compressor at the near design point. Based on this, the retrofit schemes for the axial compressor are beneficial to improve the load capacity and reduce the axial dimension with a slight impact on efficiency and surge margin. These show the potential application prospects of high hub/tip ratio mixed-flow compressors.
A new airfoil shape parameterization method is developed, which extended the Bezier curve to the generalized form with adjustable shape parameters. The local control parameters at airfoil leading and ...trailing edge regions are enhanced, where have significant effect on the aerodynamic performance of wind turbine. The results show this improved parameterization method has advantages in the fitting characteristics of geometry shape and aero- dynamic performance comparing with other three common airfoil parameterization methods. The new paramete- rization method is then applied to airfoil shape optimization for wind turbine using Genetic Algorithm （GA）, and the wind turbine special airfoil, DU93-W-210, is optimized to achieve the favorable C1/Cd at specified flow con- ditions. The aerodynamic characteristic of the optimum airfoil is obtained by solving the RANS equations in computational fluid dynamics （CFD） method, and the optimization convergence curves show that the new para- meterization method has good convergence rate in less number of generations comparing with other methods. It is concluded that the new method not only has well controllability and completeness in airfoil shape representation and provides more flexibility in expressing the airfoil geometry shape, but also is capable to find efficient and op- timal wind turbine airfoil. Additionally, it is shown that a suitable parameterization method is helpful for improv- ing the convergence rate of the optimization algorithm.
Ag nanoparticles (NPs) with different surface morphologies can be synthesized through white light irradiation of photochemically prepared Ag nanoseeds within 20 min. The fundamental photophysical and ...photochemical properties of benzil in deaerated solvents at room temperature are investigated through analyzing nanosecond absorption spectra. In ethanol, after the single photon excitation of benzil by 355 nm nanosecond laser pulses, one kind of reactive intermediate with a long-lived lifetime of 375.83 ± 93.70 μs is generated and capable of reducing the coexisted Ag+ to generate Ag nanoseeds with their diameters in the range from 3 to 12 nm. Theoretical calculations indicate that the reactive intermediate is benzil-ethanol hydrogen-bonded complex biradical (ben-eth biradical). Furthermore, the excited-state hydrogen bonding dynamics and its influence on the photophysical and photochemical properties are discussed. White light irradiation under air can make these Ag nanoseeds grow in size with a speed of 10 nm/min and have unique morphologies. In particularly, the nanowhisker covered Ag NPs can be synthesized and possess a unique narrow optical absorption peak at 325 nm. This work not only provides insights into the mechanisms of photosensitized synthesis of Ag nanoseeds but also emphasizes the utilization of white light as a convenient and efficient tool to tailor morphologies of Ag NPs.
The hybrid vortex method, in which vortex panel method is combined with the viscous-vortex particle method (HPVP), was established to model the wind turbine aerodynamic and relevant numerical ...procedure program was developed to solve flow equations. The panel method was used to calculate the blade surface vortex sheets and the vortex particle method was employed to simulate the blade wake vortices. As a result of numerical calculations on the flow over a wind turbine, the HPVP method shows significant advantages in accuracy and less computation resource consuming. The validation of the aerodynamic parameters against Phase VI wind turbine experimental data is performed, which shows reasonable agreement.
Stereoelectroencephalography (SEEG) has been widely used in the presurgical evaluation of patients with medically intractable epilepsy. In the past, SEEG was commonly used as a method for mapping and ...localizing the epileptogenic zone (EZ). Since 2004, several studies have been conducted to examine the effectiveness of SEEG-guided radiofrequency thermocoagulation (RF-TC) in treating refractory epilepsy. However, the seizure-free and responder rates varied greatly across studies. We aimed to analyze the outcome of 56 patients who were treated with SEEG-guided RF-TC to evaluate the effectiveness of this treatment. SEEG-guided RF-TC can be considered as a treatment for refractory epilepsy. However, due to its limited efficacy, SEEG-guided RF-TC might be regarded as a temporary treatment performed under SEEG rather than a promising treatment for refractory epilepsy.
The electrocatalytic hydrogen evolution reaction (HER) is a green chemistry route for sustainable energy production. Compared to 2H-phase molybdenum disulfide (MoS
2
), the 1T-phase MoS
2
(1T-MoS
2
) ...has higher theoretical activity and faster charge transfer kinetics, but the HER performance of 1T-MoS
2
is commonly hindered by limited active edge/defect as well as poor structural stability. Herein, we synthesize a well-defined 2D vdW heterostructure composed of Pd doped 1T-MoS
2
and black phosphorus (BP) nanosheets
via
electrostatic self-assembly. The spontaneous Pd doping under mild reaction conditions could introduce catalytically active sulfur vacancies in MoS
2
without triggering a wide range of 1T to 2H phase transformation. The hetero-interfacial charge transfer from BP to Pd-1T-MoS
2
can effectively improve the intrinsic activity of Pd-1T-MoS
2
with a relatively low S vacancy concentration and simultaneously stabilize the 1T-phase structure. Due to the wide-range light absorption of BP nanosheets and the high carrier mobilities of 2D materials, the HER activity of the obtained Pd-1T-MoS
2
/BP could be further enhanced under ≥420 nm visible light illumination.
We synthesized a well-defined 2D van der Waals heterostructure composed of Pd doped 1T-phase MoS
2
and black phosphorene. The hetero-interfacial charge transfer improve the visible-light enhanced eletrocatalytic hydrogen evolution performance.
Covalent triazine frameworks (CTFs) are promising photocatalysts for hydrogen evolution. The current research focuses on optimizing the band structure and intrinsic charge separation efficiency of ...CTFs. Other influential factors, i.e., the water affinity and the interaction with the Pt co-catalyst, are rarely investigated. Herein, we provide a facile protonation strategy for significantly improving the photocatalytic performance of CTFs. The protonated CTFs (P-CTF) can exhibit a hydrogen evolution rate of 6595 μmol g–1 h–1, which is 7.14 times that of pristine CTFs. The main contribution of protonation is to improve the interaction among the P-CTF, H2O molecules, and Pt co-catalyst, which can increase the H2O concentration around the active catalytic sites, thus facilitating the transfer of the photogenerated electron from the Pt co-catalyst to the H2O. Our results provide some insight into the role of protonation in promoting the photocatalytic hydrogen evolution performance.
An improved mean streamline loss model for splittered centrifugal/mixed-flow compressor impellers is presented. One-dimensional model predictions, CFD simulations and experimental results for Krain ...impeller are compared to confirm the model validity. A new description for the interaction between blade number and splitter blade length of a splittered mixed-flow compressor impeller with high hub/tip ratio is discussed and formulized. The optimal principal blade number and optimal splitter blade length corresponding to maximum impeller efficiency are selected by the new formulas studied. The results indicate that the improved model and new formulas have reasonable prediction effects for the impeller efficiency and the selection of blade number and splitter blade length. Blade height/pitch ratio can also be adopted as a selection reference especially for high hub/tip impellers. Effective blade number or equivalent solidity is only suitable for evaluating load capacity rather than efficiency in impeller design processes.
Objective
Insulo‐opercular seizures are characterized by diverse semiology, related to the insula's multiple functional roles and extensive connectivity. We aimed to identify semiologic subgroups and ...correlate these with insulo‐opercular subregions based on connectional architecture.
Methods
We retrospectively collected a large series of 37 patients with insulo‐opercular seizures explored by stereoelectroencephalography (SEEG) from three epilepsy centers. A new human brain atlas (Brainnetome Atlas, BNA) based on both anatomic and functional connections was employed to segment insulo‐opercular cortex. Semiology and SEEG changes were carefully reviewed and quantified. Principal component analysis and cluster analysis were used to correlate semiologic characteristics with insulo‐opercular subregions.
Results
Four main semiologic subgroups were identified, organized along an anteroventral to posterodorsal axis based on BNA. Group 1 was characterized by epigastric sensation and/or integrated gestural motor behaviors with or without feelings of fear or rage, involving the anteroventral insular regions and mesial temporal lobes. Group 2 was characterized by auditory sensations and symmetric proximal/axial tonic signs involving the posteroventral temporal operculum. The characteristics of group 3 were orofacial and laryngeal signs, involving the intermediate insulo‐opercular regions. The features of group 4 were somatosensory signs followed by nonintegrated gestural motor behaviors and/or asymmetric tonic signs involving the posterodorsal insulo‐opercular regions with propagation to the mesial frontal lobes. Thus anteroventral seizure organizations predominantly showed limbic system semiology, whereas more posterodorsal regions were associated with semiology involving mainly the sensorimotor system. Subjective symptoms proved to be particularly discriminating factors.
Significance
Insulo‐opercular seizures can be categorized in terms of clinical semiology and correlate with connectional architecture subregions along an anteroventral‐posterodorsal axis in line with the cytoarchitectonic gradient rather than the gyral anatomy of the insula cortex. This provides new insights into facilitating differential diagnosis and presurgical localization but also highlights the importance of considering connectional architecture in determining neural correlates of complex semiologic patterns.
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