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Groundwater infiltration into tunnels causes water to percolate through the fissure channels in the initial support shotcrete. This results in the dissolution and outflow of calcium hydroxide, a key product of cement hydration. This process significantly incurs the formation of crystallization blockages in the tunnel drainage systems. Optimizing the shotcrete mixing ratio is a feasible way to mitigate these blockages. Therefore, this study conducts calcium dissolution tests to investigate the impact of six admixtures, namely, antialkali agent, nanosilica, nanosilica carbonate, fly ash, sodium methyl silicate waterproofing agents, and silane waterproofing agents, on calcium dissolution resistance. Also, mechanical and microscopic tests are carried out to examine their impact on the strength and pore structure of the shotcrete. The objective of this study is to determine the optimal admixture for enhancing the calcium dissolution resistance of shotcrete. Results indicate that the antialkali agent significantly reduces the calcium leaching content of shotcrete. When the dosage is 14%, the calcium leaching amount is reduced by 68.4% in 28 days. Followed by nanosilica and silane waterproofing agents, with optimal dosages of 12 and 0.4%, respectively, the dissolution amount of calcium ions in shotcrete was reduced by 32.87 and 26.5%, respectively. Fly ash curing for 28 days can also reduce the calcium ion dissolution of shotcrete, while nanocalcium carbonate and sodium methyl silicate have little effect on the calcium dissolution of shotcrete. The antialkali agent with a strong calcium ion dissolution effect can improve the tensile strength of shotcrete under long-term curing conditions, which can be increased by 52%, but it compromises the growth of compressive strength. Nanosilica, fly ash, and silane waterproofing agents can improve both the compressive strength and tensile strength of shotcrete under long-term curing conditions. Specifically, at 28 days of curing, the compressive strength increased by 16.83, 28.8, and 20% and the tensile strength increased by 50.24, 60, and 64.5%. In addition, the microscopy results show that the antialkali agent, nanosilica, and silane waterproofing agents promote the hydration process of cement to form ettringite with a low and stable calcium–silicon ratio and reduce calcium hydroxide crystals. Nanosilica and silane waterproofing agents optimize the pore distribution in shotcrete by increasing beneficial pores, decreasing harmful pores, and reducing total porosity.

The cross-section, thickness, and material of the autobody structure determine the crashworthiness and lightweight level. Different from the variables in traditional autobody design that are considered separately, the basic theory of 3G-optimization is to simultaneously consider geometric shape (Geometry), the thickness of structure (Gauge), and material grade (Grade) in structural optimization design, which is conducive to maximizing the lightweight potential of the structure. This paper presents a cross-section optimization method for multi-cell thin-walled structures based on 3G-optimization, which is used in the structural design of crash box. Based on full width frontal collision condition, the cross-section shape, thickness, and material variables of the multi-cell crash box are optimized simultaneously. Multiple sets of optimization schemes show obvious weight reduction effect while ensuring safety. Besides, the sub-system decoupling method and hybrid cellular automaton (HCA) method are applied to 3G-optimization process, which is beneficial to improve the calculation efficiency and provide a theoretical basis for the definition of the initial design space for 3G-optimization.

Mimicking the temporal pattern of biological behaviors during the natural repair process is a promising strategy for biomaterial-mediated tissue regeneration. However, precise regulation of dynamic cell behaviors allocated in a microenvironment post-implantation remains challenging until now. Here, remote tuning of electric cues is accomplished by wireless ultrasound stimulation (US) on an electroactive membrane for bone regeneration under a diabetic background. Programmable electric cues mediated by US from the piezoelectric membrane achieve the temporal regulation of macrophage polarization, satisfying the pattern of immunoregulation during the natural healing process and effectively promoting diabetic bone repair. Mechanistic insight reveals that the controllable decrease in AKT2 expression and phosphorylation could explain US-mediated macrophage polarization. This study exhibits a strategy aimed at precisely biosimulating the temporal regenerative pattern by controllable and programmable electric output for optimized diabetic tissue regeneration and provides basic insights into bionic design-based precision medicine achieved by intelligent and external field-responsive biomaterials.

This paper probes into the different stages of development of public policies of the global wind power industry since the beginning of the 21st century and the impetus of such development. The Danish government introduced two energy plans which made it become a world leader in wind power; the German government launched public policies to buy-back and support the development of offshore wind power to boost the growth of its wind power industry, the booming of the wind power industry in the United States cannot be separated from its tax model and policy promotion. After a rapid development from 2000 to 2021, China’s wind power industry is stepping into the “parity era”. Combining with its national conditions, it has deployed “carbon neutral” and “carbon peaking” and other strategies. However, through analysis, this paper finds that wind energy in China has not been utilized well. For example, in 2020, China’s annual wind curtailment rate reached 16.61 billion kWh, which is equivalent to the total energy production of some countries a year. In the northwestern region of China, where this phenomenon is the most serious, the total curtailment reaches 1.95 billion kWh. Shannxi, Qinghai, Ningxia, and Xinjiang are four provinces in the region. The amount of curtailment of these places account for 30,100 kW, 32,100 kW, 20,100 kW, 35,100 kW respectively, accounting for 10.4%, 8,6%, 3.8%, and 11.2% respectively in northwest China. At the same time, in the first half of 2021, the bidding volume of wind power in the national open market reached 32.92 GW, which equals the annual bidding volume in 2020, leading to a surge in the volume and a severe shortfall in energy subsidies. Currently, the subsidies have decreased from 0.25 yuan per kWh at the peak to 0.06 yuan per kWh, making wind power companies cash-strapped. In summary, the current Chinese wind power industry has problems such as the serious “wind curtailment” phenomenon and imperfect policies related to subsidies for renewable energy. This paper aims to provide suggestions for the development of China’s wind power industry from three aspects, namely learning policies and innovating public policies, learning technologies and suggestions to policies, under the complex context at home, and abroad and the development process of leading countries in the wind power industry.

A nanocoral like composite was prepared by simply grinding the Fe-based metal-organic framework (NH2-MIL-53), Co-based metal-organic framework (ZIF-67) and dicyandiamide (DCDA) and subsequent pyrolysis treatment. The prepared composites displayed the hierarchical porous structure, the large specific surface area, and abundant N catalytic active sites. The optimal composite exhibited an excellent oxygen reduction reaction (ORR) activity with a half-wave potential (E1/2) of 0.87 V (vs. reversible hydrogen electrode, RHE) which was higher than that of the commercial 20 wt% Pt/C. At the same time, the oxygen evolution reaction (OER) overpotential of the composite at 10 mA cm−2(Ej10) was 1.563 V, which was also lower than that of the commercial RuO2under the same conditions. The doping of DCDA increased the content of N, significantly improving the ORR and OER activities of the composites. The prepared composite exhibited excellent ORR/OER bifunctional catalytic activity with the ORR/OER potential gap (the potential difference, i.e., ΔE = Ej10- E1/2) of only 0.693 V, lower than that of Pt/C + RuO2(ΔE = 0.763 V) under the same conditions. Assembled in the Zn-air battery, the prepared composite showed a better performance than Pt/C + RuO2(m: m = 1: 1). It provided a promising strategy for preparing the efficient bifunctional catalyst.

Background: Tetralone derivatives, important resources for the development of new drugs which can act in the treatment of central nervous system disorders or participate in synthesis reaction for the synthesis of various pharmaceuticals, have great research value and a bright prospect in exploitation. Methods: A novel chiral HPLC method for efficient enantioseparation of eight tetralone derivative enantiomers was developed on cellulose based CHIRALPAK IC chiral stationary phase under normal mode by investigating the effects of type and content of organic modifier, column temperature and flow rate on retention and enantioselectivity. Besides, the specificity, linearity, stability, precision, accuracy and robustness of this method were also validated. Results: Satisfactory enantioseparation was obtained for all enantiomers in n-hexane/2-propanol mobile phase system at ambient temperature. The thermodynamic study indicated that the solute transfer from the mobile to stationary phase was enthalpically favorable, and the process of enantioseparation was mainly enthalpy controlled. This method met the requirements for quantitative determination of tetralone derivative enantiomers. Conclusion: This study can provide great and important application value for enantioseparation of eight pairs of newly synthesized tetralone derivative enantiomers under normal mode using CHIRALPAK IC chiral column.

Stem cell therapy serves as an effective treatment for bone regeneration. Nevertheless, stem cells from bone marrow and peripheral blood are still lacking homologous properties. Dental pulp stem cells (DPSCs) are derived from neural crest, in coincidence with maxillofacial tissues, thus attracting great interest in in situ maxillofacial regenerative medicine. However, insufficient number and heterogenous alteration of seed cells retard further exploration of DPSC‐based tissue engineering. Electric stimulation has recently attracted great interest in tissue regeneration. In this study, a novel DPSC‐loaded conductive hydrogel microspheres integrated with wireless electric generator is fabricated. Application of exogenous electric cues can promote stemness maintaining and heterogeneity suppression for unpredictable differentiation of encapsulated DPSCs. Further investigations observe that electric signal fine‐tunes regenerative niche by improvement on DPSC‐mediated paracrine pattern, evidenced by enhanced angiogenic behavior and upregulated anti‐inflammatory macrophage polarization. By wireless electric stimulation on implanted conductive hydrogel microspheres, loaded DPSCs facilitates the construction of immuno‐angiogenic niche at early stage of tissue repair, and further contributes to advanced autologous mandibular bone defect regeneration. This novel strategy of DPSC‐based tissue engineering exhibits promising translational and therapeutic potential for autologous maxillofacial tissue regeneration. (A) Maxillofacial bone and teeth (yellow) are originated from an isogenic group of cells within neural crest. (B) Fabrication of conductive hydrogel microspheres. (C) DPSCs isolated form autologous teeth are encapsulated within hydrogel microspheres and injected into mandibular bone def. Nanogenerator is then subcutaneously implanted and connected to microspheres for electric output in response to ultrasound. (D) Improved paracrine behavior of DPSCs contributed to the construction of regenerative niche, resulting in facilitated mandibular bone regeneration.

Due to the complex composition of biochar and the potential interactions between the components that jointly make up biochar, previous studies have always shown controversial results regarding impacts of biochar on soil phosphorus (P) solubilization. Using a nested experimental design, this study investigated the effects of different components of biochar, i.e.whole biochar (BC), dissolved biochar (DBC) and washed biochar (WBC) on the microbial-mediated P solubilizing process. The growth of Bacillus megaterium, acid/alkaline phosphatase activity, differential metabolites of bacteria and metabolic pathways were measured in treatments with biochar pyrolyzed at 200, 300, 400, 500 and 600 °C. Results showed that BC, DBC and WBC all negatively affected the growth and alkaline phosphatase activity of B. megaterium, and BC500/WBC500 and BC400/WBC400 had the greatest impacts. The negative effects of high-temperature biochar on cell proliferation were caused by persistent free radicals and included down-regulation of histidine metabolism by BC400 and interference in nucleotide metabolism by BC600. The impacts of low-temperature biochar on cell proliferation and alkaline phosphatase activity were highly related to the metal content. Using the independent action model, antagonistic effects were found between DBC and WBC on inhibiting B. megateriumgrowth, while these biochars had synergistic effects on inhibition of alkaline phosphatase activity. Overall, this study provides insights on how biochar adversely modulates microbial-mediated P solubilization.

Metal/composite hybrid thin-walled structure is the most preferential approach to achieve dual contradictive objectives of high crashworthiness and lightweight of auto body. Its collapse with regard to different fiber layup patterns is one of the governing mechanisms of energy dissipation, which is yet to be explored. Especially, the effect of different fiber layup angles and layup sequences on bending collapse, which is one of the most significant performance indicators, has received little attention. To this gap, this study investigates experimentally and numerically the bending characteristics of aluminum/carbon fiber reinforced plastic (Al/CFRP) hybrid structures with different layup angles and layup sequences. To start with, three-point bending tests are carried out on specimens to derive the bending failure behavior and crashworthiness, and the internal section damage is observed by CT scan. Finite element model is then constructed and benchmarked against the test results to be proficient. On this basis, the effects of Al thickness, number of CFRP layers and CFRP wrapping range on the bending performance of hybrid tube are analyzed numerically. The simulation results show that layup angle has greater effect on the bending performance than layup sequence. Increasing Al thickness and the number of CFRP layers can effectively improve the bending resistance of structure, and appropriate partial wrapping of CFRP can increase the specific energy absorption (SEA) by 10.92% compared with that of complete wrapping. The revelation from this study provides sound reference for the crashworthiness design of metal/composite hybrid thin-walled structure.

This paper focuses on the multi-scale modelling method for strain rate dependent behaviour of long fibre reinforced thermoplastics based on the Mori–Tanaka scheme. In the present work, the anisotropic and nonlinear viscoelastic–viscoplastic behaviour of an injection moulded plate are experimentally characterised, and the sensitive range of strain rates is discussed. Fibre orientation tensors, content and fibre length are measured and analysed based on micro computed tomography images at different positions of the plate. Further, a multi-scale material model considering microstructure variables, constitutive models of two phases and failure criteria, is proposed. The accuracy of the model is validated by finite element simulations, including five strain rates and three loading directions. The comparison results indicate that the calculated stress–strain curves show a good consistency with the experimental data.

Differential Evolution is a well-known stochastic algorithm in Evolutionary Computation (EC) for single-objective numerical optimization, and its powerful variants secured excellent ranks in recent competitions. These winner DE variants all employed binomial crossover which tackles the positional bias in crossover operation by treating the D parameters separately and independently, however, the binomial crossover in these winner DE variants still have bias from the spatial search perspective, and this was the reason why the QU asi- A ffine TR ansformation E volution (QUATRE) algorithm in the literature was proposed. In this paper, a novel QUATRE algorithm with novel adaptation of E volution M atrix and S election operation (QUATRE-EMS) was proposed to further improve the overall performance of the QUATRE variants for numerical optimization and the main highlights can be summarized as follows. First, the number of control parameters is reduced from three in DE to two in QUATRE-EMS by proposing an auto-generated evolution matrix. Second, a novel adaptation scheme of the evolution matrix M is proposed for a better adaptation of the landscape of the objective during evolution; Third, a new selection operation is proposed instead of employing the canonical selection operation in DE. Finally, a large test suite containing 100 benchmarks from CEC2013, CEC2014, CEC2017 and CEC2022 test suites for single-objective numerical optimization is used for algorithm validation, and total 11 state-of-the-art algorithms including our QUATRE-EMS are taken into comparison. The experimental results show the superiority of our algorithm in comparison with former QUATRE variants and several state-of-the-art DE variants. [ABSTRACT FROM AUTHOR]

In order to accelerate the optimization process of automotive seats, decrease the amount of computations, and realize forward design of seat performance, a simplified parametric model (SPM) is introduced in this paper during the optimization process of a school bus seat. The validity of the SPM of the seat and the feasibility of the modeling method are proved. The results calculated by the SPM show a good consistency with the shell element model. The SPM can also accurately reflect the deformation and stress of the seat in dynamic tests. Through mechanical analysis and energy analysis of the seat frame, the dynamic performance of the seat is improved to meet regulatory requirements. The SPM has the advantages of simple process, less number of units, time savings in modeling and calculation, and it provides the possibility to quickly analyze the performance of school bus seats and improve seat structure.

This paper presents a new method to evaluate the design stiffness of vehicle structure and restraint system from the perspective of coupling effect, at the preliminary stage of safety design. The fast iteration algorithm is established to calculate occupant response database. Subsequently, the expressions about three indexes are derived to evaluate the crash pulse, the restraint system and the coupling effect between them. Based on the data from National Highway Traffic Safety Administration (NHTSA) frontal crash impact tests, the star-estimate map is established to estimate the star rating and design stiffness. Finally, a safety design example of M6 model is optimised to verify the validity of the proposed method, and the relative risk score (RRS) of design solution decreases by 43.6%. The proposed method can be used in the phase of conceptual design, greatly reduce the calculation amount of CAE analysis and shorten the product development cycle.

Aiming at the issue of crystallization and blockage of drainage system due to the massive calcium loss from the tunnel shotcrete, a self-designed tunnel seepage crystallization modelling system was developed. This system was produced in conjunction with the initial tunnel support shotcrete construction and drainage pipe installation, and is capable of simulating both the seepage process of groundwater in the shotcrete and the process of crystallization in the drainage pipe. Based on three different mechanisms of anti-crystallization, which include absorbing free calcium, reducing the porosity and increasing hydrophobicity, antialkali agent, nano-calcium carbonate, and silane were selected to test, respectively. Firstly, the suitable dosing ranges of these three external admixtures for resisting calcium loss in shotcrete were determined by single factor tests, which were 7%–11%, 4%–8%, and 0.3%–0.5%, respectively. Thereafter, the response surface method was employed to evaluate the interaction of antialkali agent, nano-calcium carbonate and silane on calcium loss in shotcrete, and to establish the relationship between them, and thus to determine the admixture ratio that can effectively reduce calcium loss crystallization in shotcrete, with the optimal admixture amounts of antialkali agent being 9.242%, nano-calcium carbonate 4.889% and silane 0.366%. Lastly, the reliability of the model test results was verified by the microscopic analysis, and the results showed that the total amount of calcium dissolution in the optimized group could be reduced by 75% compared with the blank control group, and was basically consistent with that derived from the response surface regression model, validating the high accuracy of the buildup response surface regression model. The present study can provide some ideas and references for reducing the seepage crystallization behavior of groundwater in the initial tunnel support shotcrete.

The current design and optimization of the occupant restraint system (ORS) are based on numerous actual tests and mathematic simulations. These two methods are overly time-consuming and complex for the concept design phase of the ORS, though they’re quite effective and accurate. Therefore, a fast and directive method of the design and optimization is needed in the concept design phase of the ORS. Since the airbag system is a crucial part of the ORS, in this paper, a theoretical model for the vehicle airbag is established in order to clarify the interaction between occupants and airbags, and further a fast design and optimization method of airbags in the concept design phase is made based on the proposed theoretical model. First, the theoretical expression of the simplified mechanical relationship between the airbag’s design parameters and the occupant response is developed based on classical mechanics, then the momentum theorem and the ideal gas state equation are adopted to illustrate the relationship between airbag’s design parameters and occupant response. By using MATLAB software, the iterative algorithm method and discrete variables are applied to the solution of the proposed theoretical model with a random input in a certain scope. And validations by MADYMO software prove the validity and accuracy of this theoretical model in two principal design parameters, the inflated gas mass and vent diameter, within a regular range. This research contributes to a deeper comprehension of the relation between occupants and airbags, further a fast design and optimization method for airbags’ principal parameters in the concept design phase, and provides the range of the airbag’s initial design parameters for the subsequent CAE simulations and actual tests.

Throughout the vehicle crash event, the interactions between vehicle, occupant, restraint system (VOR) are complicated and highly non-linear. CAE and physical tests are the most widely used in vehicle passive safety development, but they can only be done with the detailed 3D model or physical samples. Often some design errors and imperfections are difficult to correct at that time, and a large amount of time will be needed. A restraint system concept design approach which based on single-degree-of-freedom occupant-vehicle model (SDOF) is proposed in this paper. The interactions between the restraint system parameters and the occupant responses in a crash are studied from the view of mechanics and energy. The discrete input and the iterative algorithm method are applied to the SDOF model to get the occupant responses quickly for arbitrary excitations (impact pulse) by MATLAB. By studying the relationships between the ridedown efficiency, the restraint stiffness, and the occupant response, the design principle of the restraint stiffness aiming to reduce occupant injury level during conceptual design is represented. Higher ridedown efficiency means more occupant energy absorbed by the vehicle, but the research result shows that higher ridedown efficiency does not mean lower occupant injury level. A proper restraint system design principle depends on two aspects. On one hand, the restraint system should lead to as high ridedown efficiency as possible, and at the same time, the restraint system should maximize use of the survival space to reduce the occupant deceleration level. As an example, an optimization of a passenger vehicle restraint system is designed by the concept design method above, and the final results are validated by MADYMO, which is the most widely used software in restraint system design, and the sled test. Consequently, a guideline and method for the occupant restraint system concept design is established in this paper.

Abstract: There has not been an effective method to measure the resistivity of small-size sample of mineral and solid insulating material until now. According to the Chinese National Standard (GB/T1410-2006) and features of digital high resistance meter, a small electrode experimental installation was developed; it can work with current high resistance meter; the sample decreases to 18 mm from standard size 100 mm in diameter and reduces by 30.86 times in area. A three-electrode system is supported and precisely positioned by two insulating bases whose diameter is 60 mm and height is 20 mm, which ensures accuracy of device structure and reliability of measuring results. The key technological parameters are as follows: diameter of high voltage electrode is 18 mm; diameter of measuring electrode is 14.6 mm; internal diameter and external diameter of guard electrode are 16 and 18 mm, respectively; the gap between guard electrode and measuring electrode is set at 0.6 mm. These parameters are adequate for the measurement of flat specimen of mineral and solid insulating material whose diameter is 18 mm. According to the confirmatory experiment on the volume resistivity and surface resistivity, the measuring results are almost the same, using a small electrode experimental installation and a standard electrode.

This paper presents a design method for manufacturable casting parts based on topology optimization of structural assemblies, which considers the geometry requirement and the manufacturing constraint of die-set material cost. The problem formulation follows the previous work presented in multi-component topology optimization for stamped sheet metal assemblies (MTO-S). Based on the vector method combined with Heaviside function, the moldability constraints for casting parts is formulated. As the base structure of component is easily misidentified as an undercut structure by the moldability constraints in the structural assemblies, the component baseline is proposed to realize the automatic filtering of the “fake” undercut structures which can be extended to the parting line to obtain the form of two-mold design. Several numerical examples on compliance minimization of single-mold and two-mold casting parts are conducted to verify the validity of the proposed method. The optimized results show that there is no interior void for each component and the component manufacturability has been improved obviously. The setting of minimum-area bounding box (MABB) area constraint limits and the number of components will have a significant effect on the performance of the optimized structure. Users can achieve the desirable solution based on their actual demand by making trade-offs between the structural performance and manufacturing cost.