Rational Structure Research Articles

A high-performance electrode based on low cobalt content Co0.12Ni1.88S2 growing on honeycomb-like NiCo(HPO4)2·3H2O for hybrid supercapacitors

It is desirable to design highly electrochemically active materials for practical hybrid capacitors to fulfill the demand of rapid development of portable and wearable electronics. In this work, ternary Co0.12Ni1.88S2 with low cobalt content is electrodeposited on honeycomb-like NiCo(HPO4)2·3H2O modified carbon cloth (CC@Ni–Co–P@Co0.12Ni1.88S2). The as-prepared CC@Ni–Co–P@Co0.12Ni1.88S2 can avoid the introduction of inactive components. Besides, the honeycomb-like Ni–Co–P modifier provides many active sites for Co0.12Ni1.88S2 deposition and improves its utilization efficiency. Significantly, in the three-electrode system, the CC@Ni–Co–P@Co0.12Ni1.88S2 shows specific capacitance of 1.06 F/cm2, which is three times higher than that of CC@Co0.12Ni1.88S2 without Ni–Co–P modification. Surprisingly, the hybrid supercapacitors based on CC@Ni–Co–P@Co0.12Ni1.88S2 cathode and active carbon anode also delivers excellent long-term cycle stability with capacitance retention of 94.8% after 10,000 cycles. This rational structure design provides a choice for achieving high utilization of high-quality active materials.

Constructing 3D Tent-Like frameworks in melamine hybrid foam for superior microwave absorption and thermal insulation

Taking serious electromagnetic pollution and practical application requirements into consideration, it’s imperative to develop multifunctional microwave absorption materials. In this work, the phenol–formaldehyde resin (PF) successfully adheres to melamine–formaldehyde foam (MF) as three-dimensional (3D) porous frameworks, and subsequently the substrate anchors few-layered MXene nanosheets by dripping-squeeze-drying procedures. According to the results, the hollow tent-like structure of MXene/PF@MF (MPM) shows a significant effect on microwave absorption capability, including extending heterogeneous interfaces for polarization relaxation and prolonging microwave propagation paths for energy dissipation. Based on the synergy of multiple components and rational structure, MPM exhibits a minimum reflection loss (RLmin) value of −58.8 dB at 2.2 mm and achieves an effective absorption bandwidth (EAB) of 6.74 GHz covering the entire Ku band. The microwave absorption mechanism reveals that the superior microwave absorption capability results from high conduction loss, polarization relaxation, multiple attenuations, and appropriate impedance matching. Furthermore, the MPMs possess lightweight features (32.7–48.7 g cm−3) and low thermal conductivity (0.0309–0.0318 W m−1 K−1) benefitting the unique 3D porous structure. Meanwhile, the low thermal conductivity endows MPMs with infrared stealth, which broadens the application in military fields. This work proposes a facile strategy for constructing highly efficient microwave absorbers with multiple functions.

Superior capacitive performance of spherical MnV2O6·2H2O-graphene nanosheet hybrid as electrode material for asymmetric supercapacitor

The evolution of advanced supercapacitors depends highly on the design and synthesis of electrodes with rational morphology and structure. In this paper, a facile methanol-assisted solvothermal method is reported for the synthesis of spherical hydrated manganese vanadate (MnV2O6·2H2O)-reduced graphene oxide (rGO) nanosheets hybrid. In particular, the utilization of methanol can not only change the isotropy growth of MnV2O6 but also suppresses the phase-transformation process (from orthorhombic to monoclinic) by preventing the deintercalation of crystal water. Remarkably, the MnV2O6·2H2O exhibits a superior specific capacity of 1678.5 F g−1 which is nearly four times more than that of MnV2O6 (410.2 F g−1) at 2 A g−1. After integrating with graphene, MnV2O6·2H2O spheres are uniformly encapsulated by graphene sheets with a size reduction from 1 μm to 200 nm. And a “GO-assisted Ostwald ripen-splitting” mechanism is proposed to explain the formation of MnV2O6·2H2O-rGO. Consequently, the MnV2O6·2H2O-rGO hybrid exhibits significantly improved conductivity, enhanced specific capacity (1976.3 F g−1 at 2 A g−1) and good rate capability (1422.5 F g−1 at 10 A g−1 and 1155.5 F g−1 at 20 A g−1) as well as excellent cycling stability (94.2% capacitance retention after 10,000 cycles). Moreover, the assembled asymmetric supercapacitor using MnV2O6·2H2O-rGO (the positive electrode) and activated carbon (the negative electrode) shows a superior energy density of 51.5 Wh⋅kg−1 at the power density of 849.2 W kg−1.

Profiles in understanding the density of rational numbers among primary and secondary school students

The present cross-sectional study investigated 953 fifth to tenth grade students’ understanding of the dense structure of rational numbers. After an inductive analysis, coding the answers based on three types of items on density, a TwoStep Cluster Analysis revealed different intermediate profiles in the understanding of density along grades. The analysis highlighted qualitatively different ways of thinking: i) the idea of consecutiveness, ii) the idea of a finite number of numbers, and iii) the idea that between fractions, there are only fractions, and between decimals, there are only decimals. Furthermore, our profiles showed differences regarding rational number representation since students first recognised the dense nature of decimal numbers and then of fractions. Learners, however, were still found to have a natural number-based idea of the rational number structure by the end of secondary school, especially when they had to write a number between two pseudo-consecutive rational numbers.

Problems of development of innovative power supply systems of Ukraine in the context of European integration

Purpose. To analyse problems and features of the formation of perspective concepts and scenarios for the development of the latest structures of energy supply systems for Ukraine in the context of the energy transition and European integration. Methodology. Theoretical studies, analysis, and generalization of scientific and practical results along with the comparative analysis. Findings. The European Green Deal contributes to the wide development of relevant RES-based systems in the EU countries. Ukraine has also declared its active position regarding the issues of low-carbon development and green transition with the formation of relevant implementation scenarios until 2035, 2050, and 2070. The paper analyses the current state and structure of the electricity supply system in Germany and Ukraine on their ways to low-carbon development of the energy sector and economy. As a result of the conducted research, it is possible to determine further rational steps for effective transformation of the electric power industry according to the strategy of pragmatic or low-carbon development with further measures to modernize the nuclear and thermal energy sectors and moderate RES development. Development of rational structures of electric power systems of new technological order is a constantly relevant, science-intensive direction, which brings serious changes to the traditional raw-resource economy and energy industry. Originality. The conducted comprehensive analysis of the current state and prospects for the development of the structure of electric power complexes of Ukraine and Germany makes it possible to formulate high-priority rational steps in achieving energy independence and energy security, taking into account low-carbon development of the national economy. Practical value. The represented analytics can be used to ensure sustainable development of Ukrainian energy industry, to form an outlook on problems, prospects, and aspects of optimistic and pessimistic scenarios of the generation system development.

In situ construction of hierarchical core-shell SiCnws@SiO2-carbon foam hybrid composites with enhanced polarization loss for highly efficient electromagnetic wave absorption

The drawbacks of single loss capability and skin effect severely impede the electromagnetic (EM) wave absorption performance of carbon-based materials. Developing a rational hierarchical structure with high efficiency and facile method to optimize impedance matching and improve EM wave absorption performance still remains challenge. Herein, SiCnws/carbon foam (SCF) composites with hierarchical structure, were successfully prepared by chemical vapor deposition method. The core shell structure of SiCnws@SiO2 was grown on the scaffold and inside of the cell structure in CFs. Significantly, the amount of SiCnws can be modulated by the growth temperature. Benefiting from the impedance gradient structure, coupled with interface polarization dominated loss mechanism jointly promoted the excellent EM wave absorption performance. Specifically, when the growth temperature is 1400 °C, the SCF composite achieved an optimal reflection loss value of −55.8 dB at 10.30 GHz with a thickness of 4.35 mm and a wide effective absorption bandwidth of 3.97 GHz at 3.71 mm. Meanwhile, in-situ growth of SiCnws in CFs substantially increased the compressive strength to 21.08 MPa. This work paves a new avenue to develop highly efficient EM wave absorption materials with hierarchical structures.

The Effect of Digital Economy on Urban Green Transformation—An Empirical Study Based on the Yangtze River Delta City Cluster in China

Under the new development pattern, promoting urban green transformation efficiently addresses resource and environmental restrictions and is the foundation of high-quality development. However, the development of green transformation in Chinese cities faces constraints in three dimensions, production, life, and ecology, and it is not clear whether the digital economy, as a key driver of green development, can empower urban green transformation. Therefore, this paper measures the level of urban green transformation from the three dimensions of production, life, and ecological space and empirically tests the impact of the digital economy on urban green transformation from 2011 to 2020 by using panel data from 41 cities in the Yangtze River Delta urban agglomeration. The results indicate: (1) The development of the green transformation level in the Yangtze River Delta urban agglomeration demonstrates a constant upward trend, but the absolute difference fluctuates and declines; (2) the development of the digital economy has a positive impact on urban green transformation, as well as changes in urban production, living, and ecological space; (3) the digital economy helps the green transformation of cities by supporting the growth of an advanced and rationalized industrial structure. Nevertheless, the indirect influence of an advanced and rational industrial structure on urban green transformation is quite different.

Towards an ethics perspective on the rational structure tradition of organisational communication

The rational structure tradition of organisational communication is much referenced in academicliterature. The article outlines some key characteristics of this tradition. Some important theoriststo have contributed to this tradition include the great sociologist, Max Weber; the great championof scientific management, Fredrerick Taylor; and Luther Gulick, the champion of the division andcoordination of work. The MacDonaldised organisation is used to illustrate, not to evidence, oneform of organisation that has taken key aspects of the rational structure tradition to a fatal end.This article attempts to overview this tradition and thereby to contribute an ethics perspectivefocusing on the issue of the denial of the individual.

Biomass chitosan derived 3D hierarchical porous carbon framework: Green synthesis and efficient polysulfide confinement

In this study, we synthesize a nitrogen-doped hierarchical porous carbon framework with an ultrahigh surface area (a Brunauer-Emmett-Teller surface area of 2514.79 m2/g) rich in micropores/mesopores using a template-free strategy utilizing low-cost biomass chitosan as a precursor. This environmental-friendly non-organic potassium/lithium hydroxide system not only dissolves chitosan but also activates carbon framework. Moreover, rational pore structure and physical properties (e.g. conductivity) are realized by adjusting the heat-treatment temperature. The nitrogen-doped hierarchical porous carbon framework/S cathodes reach high area capacities of 4.02 mAh/cm2 and 6.02 mAh/cm2 at 0.2C with high sulfur loadings of 4 and 8 mg/cm2, which can be attributed to the immobilization of lithium polysulfide via micropores/mesopores combined with heteroatom doping. In-situ Raman and X-ray diffraction tests further confirm that the rich micropores/mesopores of the carbon host can act as an active site for the inhibition and catalytic conversion of polysulfide. It is a new strategy and direction for recycling biomass chitosan and also provides a reference for the practical and commercial large-scale application of lithium sulfur batteries.

Construction of 0D/1D/2D MXene nanoribbons-NiCo@NC hierarchical network and their coupling effect on electromagnetic wave absorption

The construction of MXene-based composites with rational hierarchical structures and networks has emerged as a promising candidate for high-performance electromagnetic wave (EMW) absorption, stemming from the unpredictable formation of multiple components and multiple interfaces. Herein, a stable and porous 0D/1D/2D MXene nanoribbons (NRs)-NiCo@NC hierarchical network consisting of 0D NiCo alloy embedded in nitrogen (N)-doped carbon (NiCo@NC), 1D Ti3C2Tx MXene nanoribbons, and 2D N-doped carbon nanosheets is rationally constructed for EMW absorption. The “shearing effect” of alkaline KOH can induce the formation of 1D MXene nanoribbons with staggered-connected nanoribbon network and macroporosity, which greatly increases the attenuation of multiple reflections of EMW. Meanwhile, MXene nanoribbons can serve as a structural network for the subsequent growth of 2D NiCo layered double hydroxide (LDH) ultrathin nanosheets as well as a conductive network for conduction loss. The 0D NiCo@NC derived from NiCo LDH nanosheets inherit excellent eddy current losses that contribute to magnetic loss and abundant N heteroatoms that contribute to dipole polarization. Furthermore, thanks to the coupling effect, 0D/1D/2D hierarchical network provides numerous interfaces that contribute to interfacial polarization and considerable exchange resonances that contribute to magnetic loss. As a result, 0D/1D/2D MXene nanoribbons-NiCo@NC hierarchical network exhibits robust EMW absorption performance with a reflection loss (RL) value of −57.1 dB at a thickness of 4.82 mm and a RL value of −33.19 dB at a thickness of only 1.4 mm. This study provides new inspiration for the future construction of EMW absorbers with hierarchical networks.

Two Types of Subgroup-Valence Heteroatoms (PIII, TeIV) Synergistically Controlling Octa-CeIII-Encapsulated Heteropolyoxotungstate and Its Electrochemical Recognition Properties.

Rapid development of the synthetic chemistry of polyoxometalates (POMs) has greatly driven the generation of structurally variable innovative POM-based materials. Herein, we synthesized a novel PIII and TeIV synergistically controlling octa-CeIII-encapsulated heteropolyoxotungstate [H2N(CH3)2]11K2Na6H11[Ce8(CH3COO)2(HPIIIO3)2W8O20(H2O)12(B-β-TeW8O30)2(B-α-TeW8O31)4]·64H2O (1). Its distinctive anion skeleton [Ce8(CH3COO)2(HPIIIO3)2W8O20(H2O)12(B-β-TeW8O30)2(B-α-TeW8O31)4]30- is built by two tetra-vacancy [B-β-TeW8O30]8- and four tetra-vacancy [B-α-TeW8O31]10- moieties linked through an inorganic-organic hybrid [Ce8(CH3COO)2(HPIIIO3)2W8O20(H2O)12]26+ {Ce8P2W8} cluster core. Interestingly, {Ce8P2W8} is assembled from four [W2O11]10- groups and two [HPIIIO3]2- anions and eight Ce3+ ions. Besides, 1 was further composited with carboxylated multiwalled carbon nanotube (CMCN), resulting in a bi-component 1/CMCN nanocomposite. An electrochemical recognition platform (named as 1/CMCN/GCE) was built by modifying 1/CMCN on a glassy carbon electrode (GCE) for electrochemical detection of dopamine (DPA) at physiological pH (pH = 7.0). The findings have shown that 1/CMCN/GCE exhibits a good detection limit of 4.95 nM for DPA. This work provides considerable inspiration to promote innovative and rational structure designs of POM-based materials and expand their applications to electrochemical and biological detection fields.

Self-doped N, S porous carbon from semi-coking wastewater-based phenolic resin for supercapacitor electrodes.

Contamination of phenolic compounds has devastating effects on the environment. Therefore, its harmless treatment and recycling have received extensive attention. Herein, a novel method for preparing N-S doped phenolic resin (NSPR) from phenols, N and S groups in semi-coking wastewater, and formaldehyde are developed. The KOH is consequently incorporated into the NSPR through simultaneous carbonization and activation in a single step to produce porous carbon material (NSPC). The as-obtained NSPC exhibits a high specific capacitance of 182 F g−1 at 0.5 A g−1, a high energy density of 9.1 Wh kg−1 at a power density of 0.15 kW kg−1, and remarkable cycling stability in aqueous KOH electrolyte. This outstanding electrochemical performance is attributed to its ultrahigh specific surface area (SSA, 2,523 m2 g−1), enormous total pore volume (Vt, 1.30 cm3 g−1), rational pore structure, and N-S heteroatom self-doping (0.76 at% N and 0.914 at% S), which ensures adequate charge storage, rapid electrolyte ion diffusion, and contributed pseudo-capacitance. This work not only provides a facile method for transforming phenolic wastewater into high-value products but also offers a cost-effective and high-performance porous carbon material for supercapacitors.

Constructing MoS2@Co1.11Te2/Co-NCD with Te nanorods for efficient hydrogen evolution reaction and triiodide reduction

Herein, we designed and constructed MoS2@Co1.11Te2/Co-doped nitrogen carbon dodecahedron with Te nanorods (Co-NCD-T) by rational structure engineering. The as-synthesized MoS2@Co1.11Te2/Co-NCD-T composite served as a bifunctional catalyst for the hydrogen evolution reaction and triiodide reduction reaction. The incorporation of Te nanorods provided additional charge transport channels and subsequently accelerated the electron transport between the electrode and electrolyte. The synergistic effect between Co1.11Te2 and MoS2 further enhanced the catalytic activity. The MoS2@Co1.11Te2/Co-NCD-T electrode catalyst showed an overpotential of 124 mV when the current density was 10 mA·cm−2 and a small Tafel slope of 49 mV·dec−1 in an alkaline medium. The assembled solar cell exhibited a superior conversion efficiency of 9.00%, significantly higher than Pt (7.32%). The proposed strategy based on rational structure engineering is expected to facilitate the fabrication of hybrids for multi-functional applications.

Rational control of the temperature of vortex energy separator under destabilizing influence

The object of study in this article is the formation process of a rational control of the temperature of a vortex energy separator under destabilizing influences. The subject matter of the article is the process of forming a dichotomous tree by two-digit predicates from diagnostic models a vortex energy-separator device as a rational control object when destabilizing influences appear, and its further recovery. The goal is to develop an analytical approach to the formation of digital algorithms for the rational control of cold and hot air flow temperatures of a vortex energy separator. The tasks are to study the features of the process in the vortex energy-separator device; to describe a rational control system of the vortex energy-separator device; to analyze the experimental characteristics of the vortex energy-separator device; to form linear mathematical models of the nominal mode of the vortex energy-separator device; to develop linear diagnostic models that describe the inoperable states of the vortex energy separator as a rational control object; to form logical signs of diagnosing using diagnostic models, to develop recovering algorithms for the vortex energy separator. The methods used are transfer functions, discrete state space, forming production rules, two-digit predicate equations, dichotomous trees, diagnosing and recovering the operability of dynamic objects. The following results were obtained: the vortex energy-separation process features analysis, the rational control system structure and function description, the experimental characteristics analysis, the development of mathematical models, diagnostic and recovering tool development for the emergency operation process of a vortex energy separator as a rational control object for a given destabilizing influence set. Conclusions. Scientific novelty is the development of an analytical approach to the development of rational control of the vortex separation process of the air flow under the significant influence of various kinds of destabilizing influences.

Realizing High-Efficiency Yellow Emission of Organic Antimony Halides via Rational Structural Design.

Zero-dimensional (0D) organic metal halides have captured extensive attention for their various structures and distinguished optical characteristics. However, achieving efficient emission through rational crystal structure design remains a great challenge, and how the crystal structure affects the photophysical properties of 0D metal halides is currently unclear. Herein, a rational crystal structure regulation strategy in 0D Sb(III)-based metal halides is proposed to realize near-unity photoluminescence quantum yield (PLQY). Specifically, two 0D organic Sb(III)-based compounds with different coordination configurations, namely, (C25H22P)2SbCl5 and (C25H22P)SbCl4 (C25H22P+ = benzyltriphenylphosphonium), were successfully obtained by precisely controlling the ratio of the initial raw materials. (C25H22P)2SbCl5 adopts an octahedral coordination geometry and shows highly efficient broadband yellow emission with a PLQY of 98.6%, while (C25H22P)SbCl4 exhibits a seesaw-shaped [SbCl4]- cluster and does not emit light under photoexcitation. Theoretical calculations reveal that, by rationally controlling the coordination structure, the indirect bandgap of (C25H22P)SbCl4 can be converted to the direct bandgap of (C25H22P)2SbCl5, thus ultimately boosting the emission intensity. Together with efficient emission and outstanding stability of (C25H22P)2SbCl5, a high-performance white-light emitting diode (WLED) with a high luminous efficiency of 31.2 lm W-1 is demonstrated. Our findings provide a novel strategy to regulate the coordination structure of the crystals, so as to rationally optimize the luminescence properties of organic metal halides.

Quantifying the Anomalous Local and Nanostructure Evolutions Induced by Lattice Oxygen Redox in Lithium-Rich Cathodes.

Due to their accessible lattice oxygen redox (l-OR) at high voltages, Li-rich layered transition metal (TM) oxides have shown promising potential as candidate cathodes for high-energy-density Li-ion batteries. However, this l-OR process is also associated with unusual electrochemical issues such as voltage hysteresis and long-term voltage decay. The structure response mechanism to the l-OR behavior also remains unclear, hindering rational structure optimizations that would enable practical Li-rich cathodes. Here, this study reveals a strong coupling between l-OR and structure dynamic evolutions, as well as their effects on the electrochemical properties. Using the technique of neutron total scattering with pair distribution function analysis and small-angle neutron scattering, this study quantifies the local TM migration and formation of nanopores that accompany the l-OR. These experiments demonstrate the causal relationships among l-OR, the local/nanostructure evolutions, and the unusual electrochemistry. The TM migration triggered by the l-OR can change local oxygen coordination environments, which results in voltage hysteresis. Coupled with formed oxygen vacancies, it will accelerate the formation of nanopores, inducing a phase transition, and leading to irreversible capacity and long-cycling voltage fade.

Energy effective Technologies on Transport: Safety of Appliance of LED Railway Signals

For about 50 years the LED technology of visual information transfer is world-known, in spite of it, there is a row of unsolved questions of implementation of LED railway signals till present. This article is devoted to the analysis of topical issues on introduction of LED signals on railway transport, in particular: modes of operations of railway signals, influence of the atmospheric phenomena on the transmission of signal, unconcern of new technology as compared to glow lamps etc. There have been separately analysed the possible failures of LED matrix elements and the choice of the most rational structure of matrix has been grounded from the point of view of the railway signal functioning safety.

Aerodynamic analysis for a bat-like robot with a deformable flexible wing

AbstractDue to the efficient and flexible flight ability of bats, bat-like robots have become the focus of research in the field of bionic robots. Aerodynamic calculation is an important part of the research field of bat-like robot, which is the basis of the structure design and flight controller design of bat-like robot. However, due to the complex flight mechanism of bats, there is no mature theoretical method to calculate the flight aerodynamic force of bat-like robots. To solve this problem, this paper takes the membrane of a bat-like robot as the research object and analyzes in detail the effects of wing folding and unfolding and flexible deformation of the membrane on the chord length, passive torsion angle and relative velocity. Based on quasi-steady state model and blade element method, a set of aerodynamic calculation method for flexible deformed wing is established. In order to verify the effectiveness of the proposed method, the theoretical calculation results and the results of the fluid-structure interaction simulation are compared and analyzed under various working conditions. The two results are in good agreement under each working condition, and the errors are all within reasonable range, which proves the effectiveness of the method. This study can provide a theoretical basis for rational structure design and precise flight control of bat-like robot.

Системная концепция организационного механизма управления предприятиями строительного комплекса в условиях кризисной ситуации

The characteristic is given to the basic principles of the efficiency of the enterprises of the construction complex. A methodological apparatus has been developed that makes it possible to implement effective anti-crisis programs at these enterprises. The content of the concepts of complexity, manageability of a construction organization is disclosed. Specific organizational mechanisms are outlined. The stages of analysis of the state of enterprises during the reorganization of the management system in an unstable economic environment are formed. This analysis makes it possible to develop a rational structure for managing economically insolvent enterprises in the construction complex, and provides an increase in the level of organization of these enterprises as an open socio-economic system, which is very significant due to the special requirements for speed and validity of decisions in modern economic conditions.

Reducing graphene oxide carbon skeleton supported P-N heterostructure of bimetallic sulfide CoS-MoS2 nanorods for high-performance lithium storage

Constructing bimetallic sulfide components are considered to be a promising and efficient lithium storage materials. Nonetheless, preparation routes of rational structures that have abundant hierarchical interfaces or phase boundaries bimetallic sulfide are still a problem to over come. In this work, a novel hierarchical nanostructure of bimetal sulfide CoS-MoS2 nanorods are synthesized successfully by in-situ self-growth means at the hydrothermal conditions. Subsequently, we loaded it to the carbon matrix (CoS-MoS2@rGO) forming a three-dimensional structures with the help of freeze drying technology. This well-designed hierarchical structure could created a stable heterogeneous contact surface, which guarantees rapid Li+ ions diffusion and facilitates charge transfer at the heterointerface. Which can maintain capacity of 776 mAh/g over 800 cycles at 1 A/g. On the other hand, it shows an excellent rate capability of 464 mAg h−1 at 5 A/g. From the perspective of electrochemical kinetics, we analyze and explore the reason about the improved lithium storage performance. Furthermore, to insight into the relationship between matter and phase conversion, the in-situ X-ray diffraction characterization is executed. The strategy of rationally designing hierarchical heterostructures will shed light on outstanding electrochemical performance in energy storage applications.