Recently, the Chinese government has implemented stringent water requirements based on the concept of ‘Basing four aspects on water resources’. However, existing research has inadequately addressed the constraints of water resources on population, city boundaries, land, and production, failing to adequately analyze the interplay between water resource limitations and urban development. Recognizing the interconnectedness between urban water use and economic development, a multi-objective model becomes crucial for optimizing urban water resources. This study establishes a nonlinear multi-objective water resources joint optimization model, aligning with the “Basing four aspects on water resources” requirement to maximize urban GDP and minimize total water use. A genetic algorithm (NSGA-II Algorithm) is applied to solve this complex nonlinear multi-objective model and obtain the Pareto solution set, addressing information loss inherent in the traditional water quota method. The model was tested in Wujiang District, an area located in China’s Jiangsu Province that has been rapidly urbanizing over the past few decades, and yielded 50 non-inferior water resource optimization schemes. The results reveal that the Pareto solution set visually illustrates the competition among objectives and comprehensively displays the interplay between water and urban development. The model takes a holistic approach to consider the relationships between water resources and urban population, land use, and industries, clearly presenting their intricate interdependencies. This study serves as a valuable reference for the rational optimization of water resources in urban development.

γ-graphdiyne (γ-GDY) is a new two-dimensional carbon allotrope that has received increasing attention in scientific and engineering fields. The mechanical properties of γ-GDY should be thoroughly understood for realizing their practical applications. Although γ-GDY is synthesized and employed mainly in their bilayer or multilayer forms, previous theoretical studies mainly focused on the single-layer form. To evaluate the characteristics of the multilayer form, the mechanical properties of the bilayer γ-GDY (γ-BGDY) were tested under uniaxial tension using the molecular dynamics simulations. The stress–strain relation of γ-BGDY is highly temperature-dependent and exhibits a brittle-to-ductile transition with increasing temperature. When the temperature is below the critical brittle-to-ductile transition temperature, γ-BGDY cracks in a brittle manner and the fracture strain decreases with increasing temperature. Otherwise, it exhibits ductile characteristics and the fracture strain increases with temperature. Such a temperature-dependent brittle-to-ductile transition is attributed to the interlayer cooperative deformation mechanism, in which the co-rearrangement of neighboring layers is dominated by thermal vibrations of carbon atoms in diacetylenic chains. Furthermore, the brittle-to-ductile transition behavior of γ-BGDY is independent of loading direction and loading rate. The ultimate stress and Young’s modulus decrease at higher temperatures. These results are beneficial for the design of advanced γ-GDY-based devices.

Graphyne nanotube (GNT), as a promising one-dimensional carbon material, attracts extensive attention in recent years. However, the synthesis of GNT is still challenging even in the laboratory. This study reveals the feasibility of fabricating a GNT by self-assembling a monolayer graphyne (GY) ribbon on a carbon nanotube (CNT) via theoretical and numerical analysis. Triggered by the van der Waals force from the CNT, a GY ribbon near the tube first winds upon the tube and then conditionally self-assembles to form a GNT. The self-assembly process and result are heavily influenced by the ambient temperature, which indicates the thermal vibration of the nanosystem. Molecular dynamic simulation results address the temperature range conducive to successful self-assembly. Different types of GNTs, e.g. α-, β-, and γ-GNTs with specified chirality (armchair, zigzag, and chiral), length, and radius, can be obtained via self-assembly by controlling the geometry of the GY ribbons and temperature. The present theoretical understanding is helpful for fabricating GNTs with predefined morphology.

It was discovered that large-amplitude axial oscillation can occur on a rotor with an internally hydrogenated deformable part (HDP) in a rotation–translation nanoconverter. The dynamic outputs of the system were investigated using molecular dynamics simulations. When an input rotational frequency (100 GHz > ω > 20 GHz) was applied at one end of the rotor, the HDP deformed under the centrifugal and van der Waals forces, which simultaneously led to the axial translation of the other end of the rotor. Except at too high an input rotational frequency (e.g., >100 GHz), which led to eccentric rotation and even collapse of the system, the present system could generate a periodic axial oscillation with an amplitude above 0.5 nm at a temperature below 50 K. In other ranges of temperature and amplitude, the oscillation dampened quickly due to the drastic thermal vibrations of the atoms. Furthermore, the effects of the hydrogenation scheme and the length of HDP on the equilibrium position, amplitude, and frequency of oscillation were investigated. The conclusions can be applied to the design of an ideal nano-oscillator based on the present rotation–translation converter model.

Graphene, as a typical two-dimensional material, is popular in the design of nanodevices. The interlayer relative sliding of graphene sheets can significantly affect the effective bending stiffness of the few-layered graphene. For restricting the relative sliding, we adopted the atomic shot peening method to bond the graphene sheets together by ballistic C60 fullerenes from its two surfaces. Collision effects are evaluated via molecular dynamics simulations. Results obtained indicate that the fullerenes’ incident velocity has an interval, in which the graphene sheet can be bonded after collision while no atoms on the fullerenes escaping from the graphene ribbon after collision. The limits of the interval increase with the layer number. Within a few picoseconds of collision, a stable carbon network is produced at an impacted area. The graphene sheets are bonded via the network and cannot slide relatively anymore. Conclusions are drawn to show the way of potential applications of the method in manufacturing a new graphene-based two-dimensional material that has a high out-of-plane bending stiffness.

We propose a model of a nanostructure which can transform an input rotation into an output oscillation. In the model, the rotor has two identical internally hydrogenated deformable parts. The mechanism is that the rotation-induced centrifugal force and van der Waals force drive the recoverable deformation of the hydrogenated deformable parts, which gives rise to the axial translation of the free end of the rotor. Once the two hydrogenated deformable parts deform periodically, the free end of the rotor oscillates periodically in the axial direction. Molecular dynamics simulations are conducted to reveal the dynamic response of the system at low temperature. Four main types of deformation and the first three orders of vibration responses of the hydrogenated deformable parts are analyzed. Synchronous breathing vibration of the two hydrogenated deformable parts produces ideal oscillation with large amplitude. Asynchronous axial vibration of the hydrogenated deformable parts reduces the oscillation amplitude or produces beat vibration. The way to control the amplitude of the axial oscillation/vibration is given.