•A novel composite is proposed by filling layered re-entrant honeycombs with concrete.•The mechanical properties and failure modes of two types of specimens under uniaxial compression are ...investigated.•The proposed auxetic composite exhibits an enhanced stiffness and shear resistance.•The effects of cell angle and cell wall thickness on the mechanical properties are investigated.
Auxetic materials exhibit desirable mechanical properties, e.g., fracture resistance, shear resistance and energy dissipation due to their unique deformation characteristics. Honeycomb sandwich structures also have superior properties, e.g., energy absorption performance and low density. These desirable characteristics enable them as promising alternatives for building construction to meet the modern construction requirement which a higher safety standard is needed. In this study, a novel concrete composite with auxetic layered honeycomb was designed, manufactured and investigated for exploring the load-bearing performance of auxetic metamaterials under quasi-static compression. The layered honeycomb sandwich structure was analyzed by quasi-static compression test and its energy absorption performance was evaluated. Numerical models, validated by experimental results, were employed in parametric studies to further examine their performance. The results show that the layered structure has higher initial peak stress and stable platform stress. Moreover, it could improve the shear resistance and overall stability of the structure. These findings are beneficial to the applications of auxetic metamaterials in building construction.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•A direct approach to controlling the topology in structural optimization is proposed.•The structural efficiency and the effect of complexity control are well balanced.•The methodology can provide ...the designer with diverse and competitive solutions.
Structural shape and topology optimization has undergone tremendous developments in recent years due to its important applications in many fields. However, effectively controlling the structural complexity of the optimization result remains a challenging issue. The structural complexity is usually characterized by the distribution and geometries of interior holes. In this work, a new approach is developed based on the graph theory and the set theory to control the number and size of interior holes of the optimized structures. The minimum distance between the edges of any two neighboring holes can also be constrained. The structural performance and the effect of the structural complexity control are well balanced by using this approach. We use three typical numerical examples to verify the effectiveness of the developed approach. The optimized structures with and without constraints on the structural complexity are quantitatively compared and analyzed. The present methodology not only enables the designer to have a direct control over the topology of the optimized structures, but also provides diverse and competitive solutions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Finding an ideal model for disclosing the role of oxygen vacancies in photocatalysis remains a huge challenge. Herein, O-vacancies confined in atomically thin sheets is proposed as an excellent ...platform to study the O-vacancy–photocatalysis relationship. As an example, O-vacancy-rich/-poor 5-atom-thick In2O3 porous sheets are first synthesized via a mesoscopic-assembly fast-heating strategy, taking advantage of an artificial hexagonal mesostructured In-oleate complex. Theoretical/experimental results reveal that the O-vacancies endow 5-atom-thick In2O3 sheets with a new donor level and increased states of density, hence narrowing the band gap from the UV to visible regime and improving the carrier separation efficiency. As expected, the O-vacancy-rich ultrathin In2O3 porous sheets-based photoelectrode exhibits a visible-light photocurrent of 1.73 mA/cm2, over 2.5 and 15 times larger than that of the O-vacancy-poor ultrathin In2O3 porous sheets- and bulk In2O3-based photoelectrodes.
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IJS, KILJ, NUK, PNG, UL, UM
Ports are critical centers of international trade and global logistics now that economic globalization has taken hold. The efficiency performance of port logistics is crucial to building an emerging ...pattern of development in which domestic and foreign dual cycles are complementary for China. This paper examines the efficiency performance of 19 ports within five major economic circles in China. It explores how their efficiency is distributed, and the configurations of efficiency improvement during the new normal of China's economy. First, the DEA-BCC model is employed to calculate the technical efficiency performance and distribution of each port from 2011 to 2020. Then, fuzzy-set qualitative comparative analysis (fsQCA) was applied to integrate and analyze the influencing factors. The results show as follows: (1) Each port group performed differently on efficiency rankings, as well as regional distributions. Among these, the port groups of the Bohai Rim region, the Yangtze River Delta region, and the Bohai Rim region continue to rank highly. (2) From the perspective of configuration analysis, the results suggest that government support is not necessary for port logistics with better economic endowments. However, it is critical for backward ones. (3) A rational industrial structure can enhance levels of infrastructure, openness, and information technology, improving port performance. The findings can provide theoretical and practical references for better promoting the development of Chinese port management.al references for better promoting the development of Chinese port management.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Organolead halide perovskites have attracted extensive attentions as light harvesting materials for solar cells recently, because of its high charge‐carrier mobilities, high photoconversion ...efficiencies, low energy cost, ease of deposition, and so on. Herein, with CH3NH3PbI3 film deposited on flexible ITO coated substrate, the first organolead halide perovskite based broadband photodetector is demonstrated. The organolead halide perovskite photodetector is sensitive to a broadband wavelength from the ultraviolet light to entire visible light, showing a photo‐responsivity of 3.49 A W−1, 0.0367 A W−1, an external quantum efficiency of 1.19×103%, 5.84% at 365 nm and 780 nm with a voltage bias of 3 V, respectively. Additionally, the as‐fabricated photodetector exhibit excellent flexibility and robustness with no obvious variation of photocurrent after bending for several times. The organolead halide perovskite photodetector with high sensitivity, high speed and broad spectrum photoresponse is promising for further practical applications. And this platform creates new opportunities for the development of low‐cost, solution‐processed and high‐efficiency photodetectors.
Organometal halide perovskites have shown tremendous potential as incident light absorbers for optoelectronic applications. In this work, a broadband photodetecotor is demonstrated based on the CH3NH3PbI3 film, showing a photo‐responsivity of 3.49 A W−1, 0.0367 A W−1, an external quantum efficiency of 1.19 × 103 %, 5.84% at 365 and 780 nm, respectively. These results provide new opportunities for the development of high‐efficiency photodetectors.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Due to its characteristics of nearby power generation, grid-connection, conversion and use, rooftop photovoltaic power generation has formed the advantages of less investment, flexible, efficient and ...environmental protection, with broad prospects for development. Therefore, studying its economic performance is of great significance to investment decision and policy improvement. Under the current technical cost and policy conditions of rooftop photovoltaic in China, this paper constructs a cost-benefit analysis model considering the impact of inflation on cash flow. The results show that: For small rooftop photovoltaic in China, first of all, under the existing subsidy price and cost, its investment payback period is short and the risk is low. Secondly, the average internal rate of return is more than 10%, and the levelized cost of electricity is 0.2727–0.5573CNY/kWh, so the economic performance is good. Then, although the subsidy price has been lowered twice in a row in 2018, its economic performance is still relatively good. Finally, in the economic performance analysis of rooftop photovoltaic, besides the influence of power generation capacity, loan interest rate, construction cost and other factors, the time value of capital and inflation are also factors that cannot be ignored.
•The analysis is based on current policy and technology levels.•The object of analysis is industrial and commercial household photovoltaic.•The inflation rate is added to the formula for calculating various economic indicators.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Time delay of the photons coupled to the Weyl tensor in a regular phantom black hole is investigated in both weak and strong deflection gravitational lensing. We find that the time delay in the weak ...deflection lensing strongly depends on the phantom hair while the delay in the strong deflection lensing is significantly affected by the hair and the strength of the coupling. We suggest that it is necessary to measure these two kind of time signals for fully understanding and distinguishing such an interaction beyond the standard Einstein–Maxwell theory.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Two-dimensional (2D) nanomaterials, especially the inorganic ultrathin nanosheets with single or few-atomic layers, have been extensively studied due to their special structures and rich physical ...properties coming from the quantum confinement of electrons. With atomic-scale thickness, 2D nanomaterials have an extremely high specific surface area enabling their surface phase to be as important as bulk counterparts, and therefore provide an alternative way of modifying the surface phase for engineering the intrinsic physical properties of inorganic 2D nanomaterials. In this review, we focus on recent research concerning surface chemical modification strategies to effectively engineer the intrinsic physical properties of inorganic 2D nanomaterials. We highlight the newly developed regulation strategies of surface incorporation, defect engineering, and structure modulation of inorganic 2D nanomaterials, which respectively influence the intrinsic conductivity, band structure, and magnetism while maintaining the primary 2D freestanding structures that are vital for 2D based ultrasensitive electronic response, enhanced catalytic and magnetocaloric capabilities.
This tutorial review summarizes the recent advances in engineering the intrinsic physical properties of inorganic two-dimensional nanomaterials by surface chemical modification.
Crystal facet engineering of semiconductors is of growing interest and an important strategy for fine-tuning solar-driven photocatalytic activity. However, the primary factor in the exposed active ...facets that determines the photocatalytic property is still elusive. Herein, we have experimentally achieved high solar photocatalytic activity in ultrathin BiOCl nanosheets with almost fully exposed active {001} facets and provide some new and deep-seated insights into how the defects in the exposed active facets affect the solar-driven photocatalytic property. As the thickness of the nanosheets reduces to atomic scale, the predominant defects change from isolated defects V Bi ‴ to triple vacancy associates V Bi ‴ V O •• V Bi ‴, which is unambiguously confirmed by the positron annihilation spectra. By virtue of the synergic advantages of enhanced adsorption capability, effective separation of electron–hole pairs and more reductive photoexcited electrons benefited from the V Bi ‴ V O •• V Bi ‴ vacancy associates, the ultrathin BiOCl nanosheets show significantly promoted solar-driven photocatalytic activity, even with extremely low photocatalyst loading. The finding of the existence of distinct defects (different from those in bulks) in ultrathin nanosheets undoubtedly leads to new possibilities for photocatalyst design using quasi-two-dimensional materials with high solar-driven photocatalytic activity.
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IJS, KILJ, NUK, PNG, UL, UM
The electrocatalytic activity of transition‐metal‐based compounds is strongly related to the spin states of metal atoms. However, the ways for regulation of spin states of catalysts are still ...limited, and the underlying relationship between the spin states and catalytic activities remains unclear. Herein, for the first time, by taking NiII‐based compounds without high or low spin states for example, it is shown that their spin states can be delocalized after introducing structural distortion to the atomic layers. The delocalized spin states for Ni atoms can provide not only high electrical conductivity but also low adsorption energy between the active sites and reaction intermediates for the system. As expected, the ultrathin nanosheets of nickel‐chalcogenides with structural distortions show dramatically enhanced activity in electrocatalytic oxygen evolution compared to their corresponding bulk samples. This work establishes new way for the design of advanced electrocatalysts in transition‐metal‐based compounds via regulation of spin states.
Delocalized spin states in transition‐metal‐based compounds by introducing structural distortion to their confined 2D atomic layers can enhance activity in electrocatalytic oxygen evolution. This work establishes new way for the design of advanced electrocatalysts in transition‐metal‐based compounds via regulation of spin states.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
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