Hierarchical Transition Research Articles

Investigate the role of V in the Nitrogen-doped hierarchical porous carbon-supported binary transition metal nitrides catalyst for oxygen reduction reactions

N-doped carbon-supported titanium nitride (TiN/NC) is considered promising for its application in Zn-air batteries. However, the performance of TiN/NC cannot meet the practical application. To solve this problem, the catalytic activity and stability of the catalyst can be improved by introducing the second metal element V. In this paper, a high-performance catalyst (TixV1−xN/NC/C) was prepared by supporting titanium-vanadium binary transition metal nitride nanoparticles on nitrogen-doped carbon. The experimental results and density functional theory (DFT) calculations confirm that the electronic, atomic and microstructure of titanium nitride nanoparticles can be properly tuned by introducing V ions, which is beneficial to tune the adsorption/adsorption of oxygen intermediates on titanium nitride nanoparticles and decreasing the potential of the rate determining step, thereby increasing the catalytic activity. The TixV1−xN/NC/C composite exhibits excellent ORR performance with an onset potential (Eonset) and limiting current density of 0.91 V (vs. RHE) and 4.90 mA∙cm−2, respectively. The Ti0.85V0.15N/NC/C-based Zn-air battery exhibits the power density of 124.78 mW·cm−2, open circuit voltage of 1.34 V and high specific capacity of 731.38 mAh·g−1. More importantly, this work has deepened the understanding of the TMN-based catalytic mechanism and paved the way for enhancing the catalytic performance of TMN-based catalysts.

Hierarchical conversation flow transition and reasoning for conversational machine comprehension

Hierarchical conversation flow transition and reasoning for conversational machine comprehension

Wheat-like Co3O4 on carbon derived from silk as anode materials for enhanced lithium storage

The design and preparation of hierarchical porous transition metal oxide-carbon matrix anodes with unique structure play the significant role in highly reversible lithium ion batteries. Herein, hierarchical porous wheat-like Co3O4 on carbon derived from natural silk (named as SK@Co3O4) nanobelts are fabricated successfully by one-step hydrothermal technique and ensuing high-temperature calcination. The wheat-like SK@Co3O4 nanobelts consist of a number of nanobeams. The length of nanobelts is around 1 µm whereas the diameter is 200 nm. Moreover, the SK@Co3O4 anode for lithium ion batteries retains 1108 mA h g−1 following 100 cycles at 100 mA g−1, 707 mA h g−1 and 709 mA h g−1 after 150 cycles at 2 A g−1, 625 mA h g−1 and 617 mA h g−1 after 150 cycles at 5 A g−1,which show extraordinary cycle stability of the composite. The remarkable lithium storage property results from the hierarchical porous structure and this structure can not only provide a short ion transport path but also raise the area of contact between the electrolyte and electrode.

Cognitive control is modulated by hierarchical complexity of task switching: An event-related potential study

The study aimed to explore the effect of hierarchical complexity on task switching. The participants (n = 36) were asked to perform a magnitude or parity judgement on digits (1−9) in the hierarchical simple or complex block. In the simple block, participants made a numerical judgement on the presented digit (1−9) in each trial, whereas in the complex block, they had to first identify whether the digit in the current trial belonged to a predefined category (e.g., whether it was an even number), then perform a numerical judgement or not respond. The behavioural results revealed a significant interaction between hierarchical complexity and transition type (repeat vs. switch), with greater switch cost in the complex than in the simple block. Event-related potentials (ERPs) locked in the cue stage did not reveal this interaction, whereas the ERPs locked in the target stage revealed this interaction during the N2 and P3 time windows, with a larger switch negativity (switch minus repeat) in the complex than in the simple block. These findings demonstrate that an increase in hierarchical complexity triggers increased reactive control in the inhibition of the old task-set and reconfiguration of the new task-set during task switching.

Translating a large subset of stateflow to hybrid CSP with code optimization

Stateflow is a graphical language for modeling hierarchical transition systems, well-known for the complexity of its semantics, which is only informally explained in its user manual. Formal analysis and verification of Stateflow models usually proceed by first translating a subset of Stateflow to a formal language with precise semantics. Most existing work address only “safe” subset of Stateflow and ignore the most complex semantic issues. Moreover, it is difficult to balance simplicity of the translation algorithm with conciseness of the resulting model. In this paper, we describe a two-stage process for translating a large subset of Stateflow to Hybrid CSP, where the first stage is mostly syntax-directed and addresses each feature of Stateflow separately, and the second stage is a code optimization step that simplifies the resulting model using information from static analysis. We further incorporate this method into translation of Simulink models, in particular consider Stateflow charts triggered by various signal sources and function calls. The translation process is thoroughly validated using a hand-designed set of benchmarks, as well as larger case studies from existing work.

Interpersonal predictors of loneliness in Japanese children: variable- and person-centered approaches

BackgroundLoneliness in children has been a major topic of interest in both clinical and developmental psychology. Further studies to investigate predictors of loneliness are needed for educational practices.MethodsA total of 1088 late elementary school-aged children (48.81% boys, Mage = 10.35) participated in a 1-year longitudinal survey. We used hierarchical linear modeling and mover-stayer latent transition analysis.DiscussionFindings from the variable- and person- centered approaches suggested that less positive peer relations, higher victimization, and higher relational aggression are predictors of higher future loneliness. Meanwhile, both approaches did not reach an agreement concerning predictors to reduce loneliness. This result highlighted a utility of a combined approach and sounded an alarm for overreliance on the variable-centered approach dominating child research.ConclusionTo protect young children from loneliness, it will be more beneficial to prevent the development of loneliness rather than to apply interventions to reduce loneliness once established. Preventive practices need to be implemented to protect children from loneliness.

Efficient hierarchical robust adaptive control of mode transition for parallel hybrid electric vehicles

A fast and smooth mode transition process for parallel hybrid electric vehicles (HEVs) can improve vehicle drivability. At the same time, system uncertainty resulting from friction, gearbox, parameter perturbation, production deviations, and external disturbance of the mode transition process makes control design challenges. In this regard, this paper introduces a novel efficient hierarchical robust adaptive mode transition control strategy to achieve an accurate and fast engagement of the clutch of a parallel HEV during mode transition in the case of uncertain system parameters and unmeasurable actual clutch torque in this paper. At the upper level of the controller, a robust adaptive sliding mode control (RASMC) is proposed to calculate the clutch transmitted required torque based on the current states of the electric motor (EM) and engine, and the control parameters are optimized via the particle swarm optimization (PSO) algorithm by compromising the vehicle jerk and the clutch slipping energy loss. Moreover, a fuzzy controller is designed to calculate the expected clutch engaging speed by employing the deviation of the desired and actual clutch torques, and the actual clutch torque is not a measured value but an estimate obtained by a proportional-integral (PI) observer. At the lower level, an adaptive finite-time control (AFTC) scheme is developed to overcome the gear backlash, parameter perturbation, and external disturbance during the clutch position tracking process. The effectiveness and advantage of the proposed control strategy are verified by both MATLAB/Simulink simulations and the hardware-in-loop (HIL) test.

Hierarchical transition structure induced by gradient composition distribution in layered Ti-TiNb alloy

In this study, a hierarchical transition structure including multiphase architectures, caused by elemental gradients, is obtained in the investigated layered Ti-TiNb alloy. The formation of hierarchical transition structure enriches the component types of the layered Ti-TiNb alloy from 2 types to 7 types. Special attention was paid to the architectures consisting of α-phase in two shapes and nano-sized ω-phase, introduced by heterogeneously precipitating behavior. This study may serve as a template for designing and developing new class of layered metal materials with multi-component features.

Building a hierarchical sustainable development transition model in qualitative information approach: Electric utility industry in Indonesia

This study contributes to the literature by evaluating the sustainable development transition using qualitative information approach in the electric utility industry and recommending practical implications for decision makers. The sustainable development transition has gained more concerns to address the social, environment, economy and technological perspectives. Still, prior studies neglect to determine the sustainable development attributes in a hierarchical model and lack of qualitative information derived from linguistic preference of experts’ judgement. To fulfill this gap, the study aims to build the hierarchical model of sustainable development transition. A combined method, including fuzzy Delphi method, fuzzy interpretive structural modeling, and best worst method, is applied. From the initial proposed attribute set, thirty-seven criteria from four perspectives are validated. The results revealed that the technology transfer, innovation and production capabilities are the top aspects of the hierarchy, while learning process and social entrepreneurship practices are at the least ranking. Resource use and waste, innovation and technology adoption, and research and development are found to be the important criteria to support decision makers in the electric utility Industry in Indonesia to expedite the transition decision making for the transition acceleration.

Isomerization Reactions of the Cu15V+ Cluster: A Density Functional Theory Study.

The investigation of the chemical reactivity of complex systems such as transition metal clusters is a very complicated task because often the structures of the corresponding transition states are far from being intuitive. Bimetallic transition metal clusters represent a particular class of complex systems. In this work, density functional theory (DFT) is applied to study the isomerization reactions of the Cu15V+ cluster. Full geometry optimizations of dozens of initial structures taken along Born-Oppenheimer molecular dynamics (BOMD) trajectories were performed using a quasi-Newton method in a reduced space Cartesian coordinate system that works considering the internal degrees of freedom. Harmonic frequencies calculations were performed at the optimized structures. To study the isomerization reactions between the obtained stable isomers, a hierarchical transition state algorithm has been applied to locate the transition states of this cluster. The found transition states were than connected with the corresponding minimum structures by calculating the intrinsic reaction coordinates. This work demonstrates the capability of the applied method to study non-intuitive rearrangement mechanisms in complex finite systems and to create networks between minima and transition state structures on their potential energy surface.

Synthesis of hierarchical transition metal oxyhydroxides in aqueous solution at ambient temperature and their application as OER electrocatalysts

First-row (3d) transition metal oxyhydroxides have attracted increasing attention due to their various advantages. Although investigating the oxidation mechanism and processing such materials into hierarchical architectures are greatly desired for their further development, it remains unclear how the oxidation state change occurs, and efforts to produce hierarchical oxyhydroxides in compliance with high ecological and economic standards have progressed slowly. Here, we describe a facile one-step coprecipitation route for the preparation of hierarchical CoOOH, NiOOH and MnOOH, which involves the diffusion of NH3 originating from ammonium hydroxide solution into an aqueous solution containing metal ion salts and K2S2O8. Comprehensive characterizations by scanning electron microscope, transmission electron microscopy, X-ray diffraction analysis, X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy and in situ pH measurement demonstrated that K2S2O8 induces the oxidation state change of metal ion species after the start of hydrolysis. Meanwhile, it was found that, benefiting from the OH– concentration gradient created by the NH3 diffusion method and the suitable growth environment provided by the presence of K2S2O8 (high nucleation rate and secondary nucleation), the formation of hierarchical oxyhydroxide structures can be realized in aqueous solution at ambient temperature without the use of heat energy and additional structure-directing agents. The hierarchical CoOOH structures are performed as the electrocatalysts for the oxygen evolution reaction in alkaline media, which exhibit good activity with an overpotential of 320 mV at 10 mA cm−2 and a low Tafel slope of 59.6 mV dec–1, outperforming many congeneric electrocatalysts. Overall, our study not only provides important insights to understand the formation mechanism of hierarchical oxyhydroxides, but also opens up new opportunities for the preparation of hierarchical oxyhydroxides via a facile, green and low-cost method.

Facile synthesis of hierarchical g-C3N4@WS2 composite as Lithium-ion battery anode

Transition metal sulfides (TMSs), as highly promising candidate anode materials, are gradually attracting the attention for lithium-ion batteries (LIBs) recently on account of its multiple valence states as well as considerable capacity. Nevertheless, TMSs have relatively low inherent electronic conductivity and large volume variation, which stands in the way of their practical applications. Herein, to ameliorate the drawbacks of TMSs, we report a hierarchical g-C3N4@WS2 composite synthesized by a solvothermal reaction. The as-synthesized g-C3N4@WS2 composite provides abundant reaction active sites for lithium storage and sufficient interspace to buffer the volume variation of WS2 nanoparticles. Moreover, the ultrathin g-C3N4 nanosheets could restraint WS2 nanoparticles from agglomeration, increase the contact chances with electrolyte and facilitate the charge transport and ion diffusion. In consequence, the optimized g-C3N4@WS2 electrode delivers a large discharge capacity (1136.1 mAh g−1 at 0.1C) and superior cycling stability (433.8 mAh g−1 after 1000 cycles). In summary, a simple method for constructing hierarchical transition metal sulfides as anode materials for LIBs is proposed.

Fabrication of hierarchical flower-shaped cobalt silicate spheres with boosting performance for lithium storage

As a new type of electrode material, transition metal silicates anode has drawn increasing attention owing to high theoretical capacity, sufficient reserves and nontoxicity. Herein, a unique flower-shaped cobalt silicate was fabricated via an alkali-assisted hydrothermal synthesis method, which feathered large specific surface area and abundant meso-pores. Serving as an anode material for lithium ion batteries, the hierarchical CoSiO 2 material exhibited excellent cycling stability (1111 mAh g −1 at 0.1 A g −1 after 200 cycles) and superior rate capability (411 mAh g −1 at 10 A g −1 ). The novel structure of F–CoSiO 2 anode not only provided abundant active sites for electrochemical reactions and effectively facilitated the migration of Li ions during charge-discharge process, but also contributed to the primary pseudocapacitive charge storage behaviors. This work may open up opportunities in structure design and represent the enormous potential of hierarchical transition metal silicate as practical advanced electrode for lithium storage. • A novel flower-shaped CoSiO 2 anode material for lithium ion batteries was designed and fabricated firstly. • The 3D architecture assembled by 2D nanosheets generated large surface area and abundant mesopores. • The hierarchical structure greatly shortened mass diffusion and fascinated the transport of Li ions. • The CoSiO 2 material exhibited remarkable cycling and rate performance.

Hierarchical porous transition metal oxide nanosheets templated from waste bagasse: General synthesis and Li/Na storage performance

As a promising anode candidate, hierarchical porous transition metal oxide nanosheets (TMO-NSs) have attracted significant interest due to their various advantages of abundant active sites, high specific capacity and shortened ion/electrons transport pathways. Although the TMO-NSs have been developed in the past decades, the previous synthesis strategies have some drawbacks such as high cost, complex synthesis techniques, and the requirement of special instruments. Herein, we develop a generalized and facile biomorphic method to synthesize various controllable hierarchical porous TMO-NSs by using waste bagasse as biotemplate. Furthermore, the porosity and pore size of as-prepared hierarchical porous TMO-NSs can be adjusted by changing the precursor solution concentration. Novel hierarchical porous TMO-NSs have been successfully prepared for many ternary or binary TMO, such as NiFe 2 O 4 , ZnFe 2 O 4 , ZnMn 2 O 4 , NiO and ZnO. Owing to their unique nanostructure, as-synthesized hierarchical porous TMO-NSs show an excellent electrochemical performance when used as anode for Li/Na-ion batteries. We believe that various hierarchical porous TMO-NSs available from the green, economical and convenient biomorphic strategy may lead to further developments in research and application on TMO-NSs materials.

Stearic Acid / Mxene - Graphene Oxide Shape-Stabilized Phase Change Materials with Abnormal Properties: Ascended Phase Transition Temperature, Hierarchical Phase Transition and Formation of Confinement Layer

Stearic Acid / Mxene - Graphene Oxide Shape-Stabilized Phase Change Materials with Abnormal Properties: Ascended Phase Transition Temperature, Hierarchical Phase Transition and Formation of Confinement Layer

Self-combustion induced hierarchical nanoporous alloy transition toward high area property electrode for supercapacitor

The surfaces of nanoporous metals are easy to be oxidized under normal ambient condition. This usual attribute permits the exploration of metal-core oxide-shell structure that would be used for supercapacitors (SCs). However, the large-scale application of such electrodes is still limited by the intrinsically low ion diffusion coefficient, poor electronic conductivity and frustrating structural stability. Here we design a defect decorated hierarchical nanoporous CuMn2O4/Cu0.2Ni0.8O/CuxOy @ alloy electrode (HNP-TMO) by dealloying-coarsening-dealloying a sandwich-like NiCuMn/Ni/NiCuMn alloy and followed by self-combusting (2.1 mm s−1). The sandwiched Ni can synergy with unoxidized alloy to provide excellent mechanical stability and electronic conductivity, while the hierarchically porous structure with robust defects can ensure rapid electron/ion transportation. Benefiting from these merits, the HNP-TMO electrode with high mass loading of 7.8 mg cm−2 delivers an ultrahigh area capacity of 6.78 mAh cm−2 at 10 mA cm−2, good rate capability (maintaining 3.33 mAh cm−2 at ultra-high current density of 100 mA cm−2) and outstanding cycling performance with capacity retention of 92.7% after 12000 cycles. Full symmetric supercapacitor also demonstrates high energy and power density of 0.17 mWh cm−2 and 40.15 mW cm−2, respectively, indicating the promise for practical energy storage applications.

Tri-level attribute reduction in rough set theory

Attribute reduction serves as a pivotal topic of rough set theory for data analysis. The ideas of tri-level thinking from three-way decision can shed new light on three-level attribute reduction. Existing classification-specific and class-specific attribute reducts consider only macro-top and meso-middle levels. This paper introduces a micro-bottom level of object-specific reducts. The existing two types of reducts apply to the global classification with all objects and a local class with partial objects, respectively. The new type applies to an individual object. These three types of reducts constitute tri-level attribute reducts. Their development and hierarchy are worthy of systematical explorations. Firstly, object-specific reducts are defined by object consistency from dependency, and they improve both classification-specific and class-specific reducts. Secondly, tri-level reducts are unified by tri-level consistency. Hierarchical relationships between object-specific reducts and class-specific, classification-specific reducts are analyzed, and relevant connections of three-way classifications of attributes are given. Finally, tri-level reducts are systematically analyzed, and two approaches, i.e., the direct calculation and hierarchical transition, are suggested for constructing a specific reduct. We build a framework of tri-level thinking and analysis of attribute reduction to enrich three-way granular computing. Tri-level reducts lead to the sequential development and hierarchical deepening of attribute reduction, and their results profit intelligence processing and system reasoning.

Transformation of Danube Recreational Sites

The purpose of the research was to verify models of sustainable urbanization of the Danube riverside landscape in the suburban surroundings of Bratislava. The research focused on landscape-ecological forms of suburban urbanization in the contact of the river Danube, in the context of meanders of the Danube branches with the formation of recreational localities. The implementation of ecological principles was based on the concept of regional structures with a vision of the renewal of the ancient branches of the Danube for the creation of the climatic envelope of Bratislava from the southwestern side. The completion of the Petržalka, Slnečnice, Južné Mesto, and rural structures near Jarovce, Rusovce, and Čuňovo, conditioned by ecological urbanization, will acquire more landscape elements and a system of blue and green infrastructure. The hierarchical transition of the city to the suburban localities is solved by creating zones of recreation and sports on the Danube. Variant case studies of the "Danubia Park" near the village of Čuňovo are located on the southwestern bank of the Hrušov Reservoir of the Danube, with access to the Wild Water sports zone and the Danubiana Gallery complex. The research followed up on the verification of the recreational function in the landscape and focused on the level of low occupancy, the integration of sports and recreational functions, accessibility by all modes of transport, the penetration of recreation into the open landscape. For the identity of the original landscape, freely modeled connections to the riparian zone, work with water flow in the area, port, pedestrian and cycling connections to the EuroVelo route, outdoor museums of the Danube meadows, lakes and wetland communities, workouts, and multifunctional playgrounds, forms of wellness, sauna world and natural swimming. Ecological recreation concepts in the landscape of the Danube floodplains on the banks of the Danube used the modeling of banks, watercourse lines, meandering of recreational areas, green axes, play areas, elements, and zones. They used lighthouses and lookout towers for accent and orientation. The hierarchy of the release of small urban structures and loose forms of sensitive urbanization with functional flexibility and attractiveness proved the justification and location in the landscape of the Danube meadows, in the contact zones of the protected landscape and the watercourse. In this way, the importance of the suburban landscape structure is beneficial for the city not only in terms of functional attractiveness but also in terms of landscape protection and the climatic influence of the city's hinterland on its compact structures.

Co9S8-Ni3S2@WS2 hierarchical yolk-shelled nanospheres as superior Pt-free catalytic materials for highly efficient dye-sensitized solar cells

The hierarchical polymetallic sulfide electrocatalysts are endowed with high expectations in various energy conversion/storage fields. Herein, a facile two-step solvothermal method was employed to synthesize a series of hierarchical transition metal sulfide nanospheres with defined-well yolk-shelled structures (Co9S8-Ni3S2@WS2, Co9S8@WS2 and Ni3S2@WS2). Noteworthily, the resultant samples as the bifunctional electrocatalysts for the dye-sensitized solar cells possessed prominent electrocatalytic performances. Benefiting from the higher specific surface area, unique morphology, the synergistic effect of multi-elements and more favorable chemical compositions, the quaternary Co9S8-Ni3S2@WS2 nanospheres showed great advantaged features at promoting the reduction of triiodides in comparison with ternary Co9S8@WS2 and Ni3S2@WS2 nanospheres. Among these samples, the counter electrode with Co9S8-Ni3S2@WS2 catalysts exhibited a noteworthy power conversion efficiency of 9.67% for solar cell, which was much superior to that of Pt (8.16%).

Expanding the Structural Diversity and Functional Scope of Diphenylalanine-Based Peptide Architectures by Hierarchical Coassembly.

Modulation of the structural diversity of diphenylalanine-based assemblies by molecular modification and solvent alteration has been extensively explored for bio- and nanotechnology. However, regulation of the structural transition of assemblies based on this minimal building block into tunable supramolecular nanostructures and further construction of smart supramolecular materials with multiple responsiveness are still an unmet need. Coassembly, the tactic employed by natural systems to expand the architectural space, has been rarely explored. Herein, we present a coassembly approach to investigate the morphology manipulation of assemblies formed by N-terminally capped diphenylalanine by mixing with various bipyridine derivatives through intermolecular hydrogen bonding. The coassembly-induced structural diversity is fully studied by a set of biophysical techniques and computational simulations. Moreover, multiple-responsive two-component supramolecular gels are constructed through the incorporation of functional bipyridine molecules into the coassemblies. This study not only depicts the coassembly strategy to manipulate the hierarchical nanoarchitecture and morphology transition of diphenylalanine-based assemblies by supramolecular interactions but also promotes the rational design and development of smart hydrogel-based biomaterials responsive to various external stimuli.