Re-entrant honeycombs are widely used in safeguard structures due to their geometric simplicity and excellent energy absorption capacities.However,traditional re-entrant honeycombs exhibit insufficient stiffness and s...Re-entrant honeycombs are widely used in safeguard structures due to their geometric simplicity and excellent energy absorption capacities.However,traditional re-entrant honeycombs exhibit insufficient stiffness and stability owing to the lack of internal support.This paper proposes a new hybrid honeycomb by integrating a chiral component inside the re-entrant honeycomb.Since Young's modulus is a key parameter to evaluate the energy absorption performance and stiffness,an analytical model is given to predict the effective Young's modulus of the proposed hybrid honeycomb.It is found that the optimal design scheme is to directly insert a circular ring inside the re-entrant honeycomb.The normalized specific energy absorption(SEA)of the hybrid honeycomb is 95%larger than that of the traditional re-entrant honeycomb.The normalized SEA first increases to a peak value and then decreases with the cell wall thickness.The optimal thickness of the cell wall for the maximum SEA is derived in terms of the geometric configuration of the unit cell.The normalized SEA first decreases to a valley value and then increases with the re-entrant angle.A longer horizontal cell wall results in a smaller normalized SEA.This paper provides a new design method for safeguard structures with high stiffness and energy absorption performance.展开更多
The pseudo-planar heterojunction(PPHJ)structure obtained via layer-by-layer(LBL)deposition offers a promising pathway for efficient and stable organic solar cells(OSCs);however,solvent-induced swelling and erosion of ...The pseudo-planar heterojunction(PPHJ)structure obtained via layer-by-layer(LBL)deposition offers a promising pathway for efficient and stable organic solar cells(OSCs);however,solvent-induced swelling and erosion of the donor layer during acceptor deposition often hinder the formation of an ideal vertical phase separation(VPS)morphology.Here,a simple approach for incorporating a highly crystalline polymer as a buffer layer between the donor and acceptor layers is proposed.We investigated the effectiveness of this strategy by constructing three systems:PM6/L8-BO,PM6:D18/L8-BO,and PM6/D18/L8-BO.Compared with the other two systems,when deposited as a separate layer,D18 with low surface energy forms a dense crystalline fibrillar network,effectively suppressing L8-BO over-penetration and mitigating chloroform-induced PM6 erosion.This architecture achieves the most favorable VPS morphology with an improved donor/acceptor gradient distribution and higher phase purity,facilitating charge transport and suppressing recombination.Moreover,the D18 buffer layer can regulate molecular packing,improve active layer crystallinity,and passivate interfacial defects to reduce energy loss.Consequently,the PM6/D18/L8-BO-based device achieved a superior power conversion efficiency(PCE)of 19.80%.Notably,integrating BTP-e C9 further increased the PCE to 20.21%.This study demonstrates that introducing a highly crystalline polymer as a p-i-n buffer layer can effectively optimize the VPS morphology,enabling highperformance PPHJ OSCs.展开更多
Due to the unique deformation characteristics of auxetic materials(Poisson’s ratioμ<0),they have better shock resistance and energy absorption properties than traditional materials.Inspired by the concept of vari...Due to the unique deformation characteristics of auxetic materials(Poisson’s ratioμ<0),they have better shock resistance and energy absorption properties than traditional materials.Inspired by the concept of variable crosssection design,a new auxetic re-entrant honeycomb structure is designed in this study.The detailed design method of re-entrant honeycomb with variable cross-section(VCRH)is provided,and five VCRH structures with the same relative density and different cross-section change rates are proposed.The in-plane impact resistance and energy absorption abilities of VCRH under constant velocity are investigated by ABAQUS/EXPLICIT.The results show that the introduction of variable cross-section design can effectively improve the impact resistance and energy absorption abilities of auxetic re-entrant honeycombs.The VCRH structure has better Young’s modulus,plateau stress,and specific energy absorption(SEA)than traditional re-entrant honeycomb(RH).The influence of microstructure parameters(such as cross-section change rateα)on the dynamic impact performance of VCRH is also studied.Results show that,with the increase in impact velocity andα,the plateau stress and SEA of VCRH increase.A positive correlation is also found between the energy absorption efficiency,impact load uniformity andαunder both medium and high impact speeds.These results can provide a reference for designing improved auxetic re-entrant honeycomb structures.展开更多
Based on the symmetric re-entrant honeycomb(S-RH)structure with negative Poisson’s ratios,a novel asymmetric and rotatable re-entrant honeycomb(AR-RH)structure was proposed.Both the S-RH structure and AR-RH structure...Based on the symmetric re-entrant honeycomb(S-RH)structure with negative Poisson’s ratios,a novel asymmetric and rotatable re-entrant honeycomb(AR-RH)structure was proposed.Both the S-RH structure and AR-RH structure were produced by the 3D printing technology.Through experimental test and finite element simulation,the deformation mechanism and energy absorption characteristics of the AR-RH structure and the S-RH structure with negative Poisson’s ratios at different impact velocities were compared.The experimental test and finite element simulation results show that the novel AR-RH structure with negative Poisson’s ratios has stronger energy absorption capacity than the S-RH structure,and it has been verified that the rotatability of AR-RH can indeed absorb energy.Furthermore,the degree of asymmetry of the AR-RH structure was discussed.展开更多
The re-entrant double-staggered ladder slow-wave structure is employed in a high-power V-band coupled-cavity traveling-wave tube. This structure has a wide bandwidth, a moderate interaction impedance, and excellent th...The re-entrant double-staggered ladder slow-wave structure is employed in a high-power V-band coupled-cavity traveling-wave tube. This structure has a wide bandwidth, a moderate interaction impedance, and excellent thermal dissipation properties, as well as easy fabrication. A well-matched waveguide coupler is proposed for the structure. Combining the design of attenuators, a full-scale three-dimensional circuit model for the V-band coupled-cavity traveling- wave tube is constructed. The electromagnetic characteristics and the beam wave interaction of this structure are investigated. The beam current is set to be 100 mA, and the cathode voltage is tuned from 16.8 kV to 15.8 kV. The calculation results show that this tube can produce a saturated average output power over 100 W with an instantaneous bandwidth greater than 1.25 GHz in the frequency ranging from 58 GHz to 62 GHz. The corresponding gain and electronic efficiency can reach over 32 dB and 6.5%, respectively.展开更多
Based on the traditional re-entrant honeycomb,a novel re-entrant octagon honeycomb(ROH)is proposed.The deformation mode of the honeycomb under quasi-static compression is analyzed by numerical simulation,and the resul...Based on the traditional re-entrant honeycomb,a novel re-entrant octagon honeycomb(ROH)is proposed.The deformation mode of the honeycomb under quasi-static compression is analyzed by numerical simulation,and the results are in good agreement with the experimental ones.The deformation modes,mechanical properties,and energy absorption characteristics of ROH along the impact and perpendicular directions gradient design are investigated under different velocities.The results indicated that the deformation mode of ROH is affected by gradient design along the direction of impact and impact speed.In addition,gradient design along the direction of impact can increase the initial peak stress of ROH and accelerate its densification phase.Gradient design perpendicular to the impact direction can enhance the energy absorption performance of ROH,especially for ROH,with wall thickness increasing from the inside outwards.Compared to ROH with uniform wall thickness at the same relative density,ROH with a gradient design can increase the plateau stress by over half.With the elevation of impact velocity,the plateau stress and specific energy absorption exhibit an upward trend,aligning with the dynamic performance pattern observed in conventional honeycombs.The results can be used as a reference for the design and application of honeycomb and provide a new idea for developing more efficient and reliable energy-absorbing materials.展开更多
To overcome the shortcomings of the traditional passive ranging technology based on image, such as poor ranging accuracy, low reliability and complex system, a new visual passive ranging method based on re-entrant coa...To overcome the shortcomings of the traditional passive ranging technology based on image, such as poor ranging accuracy, low reliability and complex system, a new visual passive ranging method based on re-entrant coaxial optical path is presented. The target image is obtained using double cameras with coaxial optical path. Since there is imaging optical path difference between the cameras, the images are different. In comparison of the image differences, the target range could be reversed. The principle of the ranging method and the ranging model are described. The relationship among parameters in the ranging process is analyzed quantitatively. Meanwhile,the system composition and technical realization scheme are also presented. Also, the principle of the method is verified by the equivalent experiment. The experimental results show that the design scheme is correct and feasible with good robustness. Generally, the ranging error is less than 10% with good convergence. The optical path is designed in a re-entrant mode to reduce the volume and weight of the system. Through the coaxial design,the visual passive range of the targets with any posture can be obtained in real time. The system can be widely used in electro-optical countermeasure and concealed photoelectric detection.展开更多
The squeezing deformation of surrounding rock is an important factor restricting the safe construction and long-term operation of tunnels when a tunnel passes through soft strata with high ground stress.Under such sof...The squeezing deformation of surrounding rock is an important factor restricting the safe construction and long-term operation of tunnels when a tunnel passes through soft strata with high ground stress.Under such soft rock geological conditions,the large deformation of the surrounding rock can easily lead to the failure of supporting structures,including shotcrete cracks,spalling,and steel arch distortion.To improve the lining support performance during the large deformation of squeezed surrounding rock,this work selects aluminum foam with densities of 0.25 g/cm3,0.42 g/cm3 and 0.61 g/cm3 as the buffer layer material and carries out uniaxial confined compression tests.Through the evaluation and analysis of energy absorption and the comparison of the yield pressure of aluminum foam with those of other cushioning materials and yield pressure support systems,the strength,deformation and energy absorption of aluminum foam with a density of 0.25 g/cm3 meet the yield pressure performance requirements.The numerical model of the buffer layer yielding support system is then established via the finite element analysis software ABAQUS,and the influence of the buffer layer setting on the lining support is analyzed.Compared with the conventional support scheme,the addition of an aluminum foam buffer layer can reduce the stress and deformation of the primary support and secondary lining.The maximum and minimum principal stresses of the primary support are reduced by 13%and 15%,respectively.The maximum and minimum principal stresses of the secondary lining are reduced by 15%and 12%,respectively,and the displacement deformation of the secondary lining position is reduced by 15%.In summary,the application of aluminum foam buffer layer can reduce the stress and deformation of the primary support and secondary lining,improve the stress safety of the support and reduce the deformation of the support.展开更多
The Casimir pressure plays an important role in the adhesion stability of nanofilms at submicro scales.In this work,the Casimir pressure of peptide films deposited on a layered substrate is investigated.Three types of...The Casimir pressure plays an important role in the adhesion stability of nanofilms at submicro scales.In this work,the Casimir pressure of peptide films deposited on a layered substrate is investigated.Three types of semi-infinite substrates,i.e.,silica,silicon and gold,are considered.The buffer layer between the peptide film and substrate consists of silicon or silica.The switching sign of the Casimir pressure can be controlled in a region ranging from about 130 nm to 1000 nm,depending on the thickness of the buffer layer and the substrate.The results suggest that the critical thickness of peptide films for Casimir equilibrium increases(or decreases)by increasing the thickness of the silicon(or silica)buffer film.The influences of wetting and electrolyte screening on the Casimir pressure are also investigated.Our finding provides a theoretical guide for the adhesion stability of peptide films in organic electronics.展开更多
Stochastic optical reconstruction microscopy(STORM),as a typical technique of single-molecule localization microscopy(SMLM),has overcome the diffraction limit by randomly switching fluorophores between fluorescent and...Stochastic optical reconstruction microscopy(STORM),as a typical technique of single-molecule localization microscopy(SMLM),has overcome the diffraction limit by randomly switching fluorophores between fluorescent and dark states,allowing for the precise localization of isolated emission patterns and the super-resolution reconstruction from millions of localized positions of single fluorophores.A critical factor influencing localization precision is the photo-switching behavior of fluorophores,which is affected by the imaging buffer.The imaging buffer typically comprises oxygen scavengers,photo-switching reagents,and refractive index regulators.Oxygen scavengers help prevent photobleaching,photo-switching reagents assist in facilitating the conversion of fluorophores,and refractive index regulators are used to adjust the refractive index of the solution.The synergistic interaction of these components promotes stable blinking of fluorophores,reduces irreversible photobleaching,and thereby ensures high-quality super-resolution imaging.This review provides a comprehensive overview of the essential compositions and functionalities of imaging buffers used in STORM,serving as a valuable resource for researchers seeking to select appropriate imaging buffers for their experiments.展开更多
Maglev trains experience significant aerodynamic effects when passing through tunnels.A moving model test was conducted to explore the practical effects of speed reduction and entrance buffer structures on mitigating ...Maglev trains experience significant aerodynamic effects when passing through tunnels.A moving model test was conducted to explore the practical effects of speed reduction and entrance buffer structures on mitigating tunnel/maglev aerodynamic effects.It is found that both have an overall positive effect on mitigating the aerodynamic environment inside and outside the tunnel.Trains operating at 200 km/h show a 49.8%decrease in peak-to-peak pressure and a 50.7%decrease in transient pressure instability on inner walls compared to those at 280 km/h.Lower speeds resulted in a 65.6%decrease in amplitude and a 24.5%decrease in decay rate,both of which are parameters for exponential fittings of pressure peaks that decay naturally after the train leaves.The buffer structures result in a reduction of up to 25.7%in the maximum positive pressure and a 29.0%decrease in transient pressure instability.Additionally,a reduction in amplitude of up to 21.2%and a 32.2%increase in decay rate were observed with the use of buffer structures.Nevertheless,it is difficult to conclude direct correlations between the maximum pressure,peak-to-peak values,etc.,and the speeds or buffer structures due to the complex wave propagation in tunnels.However,speed reduction and buffer structures are proven to be effective in reducing the micro-pressure wave levels with a simpler monotonic relationship.展开更多
Man-made superheavy elements(SHE)are produced as energetic recoils in complete-fusion reactions and need to be thermalized in a gas-filled chamber for chemical studies.The ever-shorter half-lives and decreasing produc...Man-made superheavy elements(SHE)are produced as energetic recoils in complete-fusion reactions and need to be thermalized in a gas-filled chamber for chemical studies.The ever-shorter half-lives and decreasing production rates of the elements beyond Fl(atomic number Z=114)-the heaviest element chemically studied today-require the development of novel techniques for quantitative thermalization and fast extraction efficiency.The Universal high-density gas stopping Cell(UniCell),currently under construction,was proposed to achieve this.Within this work,we propose an Ion Transfer by Gas Flow(ITGF)device,which serves as a UniCell ejector to interface with a gas chromatography detector array for chemical studies.Detailed parameter optimizations,using gas dynamics and Monte Carlo ion-trajectory simulations,promise fast(within a few ms)and highly efficient(up to 100%)ion extraction across a wide mass range.These ions can then be transmitted quantitatively through the ITGF into the high-pressure environment needed for further chemical studies.展开更多
Temperate forests exert significant biogeophysical influences on local and regional climates through modulating the energy and moisture exchanges between the land surface and the atmosphere,thereby serving as crucial ...Temperate forests exert significant biogeophysical influences on local and regional climates through modulating the energy and moisture exchanges between the land surface and the atmosphere,thereby serving as crucial barriers with significant buffering impacts on the productivity of adjacent agricultural ecosystems.However,the extent and underlying mechanisms of these biogeophysical and buffering effects of temperate forest barriers remains insufficiently understood.In this study,we integrated the dynamic crop model Noah-MP-Crop with the Weather Research and Forecasting(WRF)model to investigate the biogeophysical climate regulation of temperate forests and its buffering effects on crop yields in adjacent agricultural lands across Northeast China.Our findings revealed that temperate forest barriers induced significant local climate effects by cooling air and surface temperatures and reducing wind speeds within forested areas during the growing season,while also regulating non-local climate,particularly by altering regional precipitation patterns,2 m water vapor mixing ratio(Q2),and soil moisture,predominantly in adjacent cropland areas.Furthermore,these forest barriers were found to modulate climate extremes,through affecting maximum temperature and wind speed on a local scale,as well as both maximum and minimum Q2 in non-local croplands.Our study also observed that temperate forest barriers,through biogeophysical climate regulation,enhanced GPP,NPP,and grain yields across most cropland areas.This productivity boost was especially pronounced,with yield increases up to 20%in certain regions during the extreme drought conditions of 2017,underscoring the critical role of temperate forest barriers in sustaining and enhancing crop yields under severe climatic stress.Our findings underscore the significant buffering effects of temperate forest barriers on regional agricultural production,having important implications for climate adaptation strategies aimed at bolstering agricultural resilience in the face of increasing climate variability and extremes.展开更多
The shop scheduling problem with limited buffers has broad applications in real-world production scenarios,so this research direction is of great practical significance.However,there is currently little research on th...The shop scheduling problem with limited buffers has broad applications in real-world production scenarios,so this research direction is of great practical significance.However,there is currently little research on the hybrid flow shop scheduling problem with limited buffers(LBHFSP).This paper deeply investigates the LBHFSP to optimize the goal of the total completion time.To better solve the LBHFSP,a multi-level subpopulation-based particle swarm optimization algorithm(MLPSO)is proposed,which is founded on the attributes of the LBHFSP and the shortcomings of the basic PSO(particle swarm optimization)algorithm.In MLPSO,firstly,considering the impact of the limited buffers on the process of subsequent operations,a specific circular decoding strategy is developed to accommodate the characteristics of limited buffers.Secondly,an initialization strategy based on blocking time is designed to enhance the quality and diversity of the initial population.Afterward,a multi-level subpopulation collaborative search is developed to prevent being trapped in a local optimum and improve the global exploration capability.Additionally,a local search strategy based on the first blocked job is designed to enhance the MLPSO algorithm’s exploitation capability.Lastly,numerous experiments are carried out to test the performance of the proposed MLPSO by comparing it with classical intelligent optimization and popular algorithms in recent years.The results confirm that the proposed MLPSO has an outstanding performance when compared to other algorithms when solving LBHFSP.展开更多
Aqueous zinc-ion batteries(AZIBs)have developed rapidly in recent years but still face several challenges,including zinc dendrites growth,hydrogen evolution reaction,passivation and corrosion.The pH of the electrolyte...Aqueous zinc-ion batteries(AZIBs)have developed rapidly in recent years but still face several challenges,including zinc dendrites growth,hydrogen evolution reaction,passivation and corrosion.The pH of the electrolyte plays a crucial role in these processes,significantly impacting the stability and reversibility of Zn^(2+)deposition.Therefore,pH-buffer tris(hydroxymethyl)amino methane(tris)is chosen as a versatile electrolyte additive to address these issues.Tris can buffer electrolyte pH at Zn/electrolyte interface by protonated/deprotonated nature of amino group,optimize the coordination environment of zinc solvate ions by its strong interaction with zinc ions,and simultaneously create an in-situ stable solid electrolyte interface membrane on the zinc anode surface.These synergistic effects effectively restrain dendrite formation and side reactions,resulting in a highly stable and reversible Zn anode,thereby enhancing the electrochemical performance of AZIBs.The Zn||Zn battery with 0.15 wt%tris additives maintains stable cycling for 1500 h at 4 mA·cm^(−2) and 1120 h at 10 mA·cm^(−2).Furthermore,the Coulombic efficiency reaches~99.2%at 4 mA·cm^(−2)@1 mAh·cm^(−2).The Zn||NVO full batteries also demonstrated a stable specific capacity and exceptional capacity retention.展开更多
Photocatalytic hydrogen peroxide(H_(2)O_(2))production offers a sustainable route to convert water and oxygen into H_(2)O_(2)using solar energy.However,achieving long-term stability in photocatalysts remains a critica...Photocatalytic hydrogen peroxide(H_(2)O_(2))production offers a sustainable route to convert water and oxygen into H_(2)O_(2)using solar energy.However,achieving long-term stability in photocatalysts remains a critical challenge due to mismatched kinetics between oxygen reduction(ORR)and water oxidation(WOR),which leads to hole accumulation and oxidative degradation.Here,we report a redox-mediated strategy to address this bottleneck by designing a hydroquinone-embedded covalent organic framework(Tz-QH-COF)that enables reversible hole buffering and kinetic balance.The hydroquinone(QH)units act as dynamic hole reservoirs,capturing excess holes during ORR and converting to benzoquinone(Q),which is regenerated to QH via WOR,thereby preventing oxidative decomposition.This reversible QH/Q cycle,directly visualized through in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy,ensures unmatched stability,achieving continuous H_(2)O_(2) production for 528 h(22 d)with an accumulated yield of 18.6 mmol L^(–1)—the highest reported duration for organic photocatalysts.Density functional theory calculations reveal that the QH units exhibit a strong oxygen adsorption energy and favorable two-electron ORR/WOR pathways with low energy barriers.The synergy between experimental and theoretical insights elucidates a redox-mediated charge-balance mechanism,advancing the design of robust photocatalysts for solar-driven H_(2)O_(2) synthesis.展开更多
The buffer zone of a World Natural Heritage Site constitutes a critical element of the heritage site protection system.It not only functions as an ecological security barrier,but also significantly influences the visu...The buffer zone of a World Natural Heritage Site constitutes a critical element of the heritage site protection system.It not only functions as an ecological security barrier,but also significantly influences the visual integrity and aesthetic value of the core area’s landscape.Given the rapid development of transportation infrastructure,particularly the growing number of high-speed railways traversing ecologically sensitive regions,the scientific assessment of their impact on the landscape environment of heritage sites has emerged as a pivotal concern in heritage conservation and regional development.This study focused on the section of the Guiyang-Nanning High-Speed Railway that traverses the buffer zone of the Libo World Natural Heritage Site in Guizhou Province.Beginning with five primary indicators,including natural landscape and aesthetic value,geological geomorphology and Earth history value,biodiversity value,integrity and protection management,and impact on ecological environment,a visual landscape impact assessment system for high-speed railways was developed based on the analytic hierarchy process(AHP)and the fuzzy comprehensive evaluation method(FCE).Through expert scoring,hierarchical weight calculation,and fuzzy membership degree analysis,a comprehensive assessment was conducted on the landscape ecological quality,visual coordination,and aesthetic perception within the buffer zone following the construction of high-speed railways.The findings indicate that the construction of the Guiyang-Nanning High-Speed Railway generally harmonizes well with the landscape environment of the heritage site.The level of visual disturbance remains within an acceptable range and has not significantly damaged the overall aesthetic value or authenticity of the heritage site.Although the integrity of the landscape in certain local areas has experienced a slight decline due to the exposure of bridge and slope structures,the adverse effects have been effectively mitigated through engineering interventions such as vegetation restoration and color coordination.This study innovatively integrates the AHP with fuzzy mathematics methods to achieve a comprehensive evaluation that combines both qualitative and quantitative approaches.This integration provides a scientifically grounded analytical path and a practical technical framework for assessing the visual impact of linear infrastructure projects,such as high-speed railways,within the buffer zones of World Heritage Sites.The findings offer valuable insights for the protection of landscapes and the sustainable development of infrastructure in heritage sites.展开更多
Optimizing the orientation of β-Ga_(2)O_(3) has emerged as an effective strategy to design high-performance β-Ga_(2)O_(3) device,but the orientation growth mechanism and approach have not been revealed yet.Herein,by...Optimizing the orientation of β-Ga_(2)O_(3) has emerged as an effective strategy to design high-performance β-Ga_(2)O_(3) device,but the orientation growth mechanism and approach have not been revealed yet.Herein,by employing AlN buffer layer,the highly preferred orientation of β-Ga_(2)O_(3)(100)film rather than(-201)film is realized on 4H-SiC substrate at low sputtering power and temperature.Because β-Ga_(2)O_(3)(100)film exhibits a slower growth speed than(-201)film,the former possesses the higher dangling bond density and the lower nucleation energy,and a large conversion barrier exists between these two ori-entations.Moreover,the AlN buffer layer can suppress the surface oxidation of the 4H-SiC substrate and eliminate the strain of β-Ga_(2)O_(3)(100)film,which further reduces the nucleation energy and en-larges the conversion barrier.Meanwhile,the AlN buffer layer can increase the oxygen vacancy formation energy and decrease the oxygen vacancy concentration of β-Ga_(2)O_(3)(100)film.Consequently,the solar-blind photodetector based on the oriented film exhibits the outstanding detectivity of 1.22×10^(12) Jones and photo-to-dark current ratio of 1.11×10^(5),which are the highest among the reported β-Ga_(2)O_(3) solar-blind photodetector on the SiC substrate.Our results offer in-depth insights into the preferred orientation growth mechanism,and provide an effective way to design high-quality β-Ga_(2)O_(3)(100)orientation film and high-performance solar-blind photodetector.展开更多
基金Project supported by Guangdong Basic and Applied Basic Research Foundation(Nos.2022A1515240072,2023A1515240053,2022B1515020099,and 2023A1515012641)Shenzhen Science and Technology Program(No.JCYJ20220818102409020)the National Natural Science Foundation of China(Nos.12102104 and 12002180)。
文摘Re-entrant honeycombs are widely used in safeguard structures due to their geometric simplicity and excellent energy absorption capacities.However,traditional re-entrant honeycombs exhibit insufficient stiffness and stability owing to the lack of internal support.This paper proposes a new hybrid honeycomb by integrating a chiral component inside the re-entrant honeycomb.Since Young's modulus is a key parameter to evaluate the energy absorption performance and stiffness,an analytical model is given to predict the effective Young's modulus of the proposed hybrid honeycomb.It is found that the optimal design scheme is to directly insert a circular ring inside the re-entrant honeycomb.The normalized specific energy absorption(SEA)of the hybrid honeycomb is 95%larger than that of the traditional re-entrant honeycomb.The normalized SEA first increases to a peak value and then decreases with the cell wall thickness.The optimal thickness of the cell wall for the maximum SEA is derived in terms of the geometric configuration of the unit cell.The normalized SEA first decreases to a valley value and then increases with the re-entrant angle.A longer horizontal cell wall results in a smaller normalized SEA.This paper provides a new design method for safeguard structures with high stiffness and energy absorption performance.
基金supported by the National Natural Science Foundation of China(Nos.52333006 and 22479066)Jiangxi Provincial Natural Science Foundation(No.20224ACB214002)。
文摘The pseudo-planar heterojunction(PPHJ)structure obtained via layer-by-layer(LBL)deposition offers a promising pathway for efficient and stable organic solar cells(OSCs);however,solvent-induced swelling and erosion of the donor layer during acceptor deposition often hinder the formation of an ideal vertical phase separation(VPS)morphology.Here,a simple approach for incorporating a highly crystalline polymer as a buffer layer between the donor and acceptor layers is proposed.We investigated the effectiveness of this strategy by constructing three systems:PM6/L8-BO,PM6:D18/L8-BO,and PM6/D18/L8-BO.Compared with the other two systems,when deposited as a separate layer,D18 with low surface energy forms a dense crystalline fibrillar network,effectively suppressing L8-BO over-penetration and mitigating chloroform-induced PM6 erosion.This architecture achieves the most favorable VPS morphology with an improved donor/acceptor gradient distribution and higher phase purity,facilitating charge transport and suppressing recombination.Moreover,the D18 buffer layer can regulate molecular packing,improve active layer crystallinity,and passivate interfacial defects to reduce energy loss.Consequently,the PM6/D18/L8-BO-based device achieved a superior power conversion efficiency(PCE)of 19.80%.Notably,integrating BTP-e C9 further increased the PCE to 20.21%.This study demonstrates that introducing a highly crystalline polymer as a p-i-n buffer layer can effectively optimize the VPS morphology,enabling highperformance PPHJ OSCs.
基金This research is supported by the National Natural Science Foundation of China(No.11902232).
文摘Due to the unique deformation characteristics of auxetic materials(Poisson’s ratioμ<0),they have better shock resistance and energy absorption properties than traditional materials.Inspired by the concept of variable crosssection design,a new auxetic re-entrant honeycomb structure is designed in this study.The detailed design method of re-entrant honeycomb with variable cross-section(VCRH)is provided,and five VCRH structures with the same relative density and different cross-section change rates are proposed.The in-plane impact resistance and energy absorption abilities of VCRH under constant velocity are investigated by ABAQUS/EXPLICIT.The results show that the introduction of variable cross-section design can effectively improve the impact resistance and energy absorption abilities of auxetic re-entrant honeycombs.The VCRH structure has better Young’s modulus,plateau stress,and specific energy absorption(SEA)than traditional re-entrant honeycomb(RH).The influence of microstructure parameters(such as cross-section change rateα)on the dynamic impact performance of VCRH is also studied.Results show that,with the increase in impact velocity andα,the plateau stress and SEA of VCRH increase.A positive correlation is also found between the energy absorption efficiency,impact load uniformity andαunder both medium and high impact speeds.These results can provide a reference for designing improved auxetic re-entrant honeycomb structures.
基金This work is supported by the State Key for Strength and Vibration of Mechanical Structures of Xi’an Jiaotong University(No.SV2018-KF-32)the Natural Science Foundation of Guangdong Province of China(2020A1515011064).
文摘Based on the symmetric re-entrant honeycomb(S-RH)structure with negative Poisson’s ratios,a novel asymmetric and rotatable re-entrant honeycomb(AR-RH)structure was proposed.Both the S-RH structure and AR-RH structure were produced by the 3D printing technology.Through experimental test and finite element simulation,the deformation mechanism and energy absorption characteristics of the AR-RH structure and the S-RH structure with negative Poisson’s ratios at different impact velocities were compared.The experimental test and finite element simulation results show that the novel AR-RH structure with negative Poisson’s ratios has stronger energy absorption capacity than the S-RH structure,and it has been verified that the rotatability of AR-RH can indeed absorb energy.Furthermore,the degree of asymmetry of the AR-RH structure was discussed.
基金Project supported by the National Science Fund for Distinguished Young Scholars of China (Grant No. 61125103)the Vacuum Electronics National Lab Foundation, China (Grant No. 9140C050101110C0501)the Fundamental Research Funds for the Central Universities, China (Grant Nos. ZYGX2009Z003 and ZYGX2010J054)
文摘The re-entrant double-staggered ladder slow-wave structure is employed in a high-power V-band coupled-cavity traveling-wave tube. This structure has a wide bandwidth, a moderate interaction impedance, and excellent thermal dissipation properties, as well as easy fabrication. A well-matched waveguide coupler is proposed for the structure. Combining the design of attenuators, a full-scale three-dimensional circuit model for the V-band coupled-cavity traveling- wave tube is constructed. The electromagnetic characteristics and the beam wave interaction of this structure are investigated. The beam current is set to be 100 mA, and the cathode voltage is tuned from 16.8 kV to 15.8 kV. The calculation results show that this tube can produce a saturated average output power over 100 W with an instantaneous bandwidth greater than 1.25 GHz in the frequency ranging from 58 GHz to 62 GHz. The corresponding gain and electronic efficiency can reach over 32 dB and 6.5%, respectively.
基金This work is supported by the National Natural Science Foundation of China(No.11902232).
文摘Based on the traditional re-entrant honeycomb,a novel re-entrant octagon honeycomb(ROH)is proposed.The deformation mode of the honeycomb under quasi-static compression is analyzed by numerical simulation,and the results are in good agreement with the experimental ones.The deformation modes,mechanical properties,and energy absorption characteristics of ROH along the impact and perpendicular directions gradient design are investigated under different velocities.The results indicated that the deformation mode of ROH is affected by gradient design along the direction of impact and impact speed.In addition,gradient design along the direction of impact can increase the initial peak stress of ROH and accelerate its densification phase.Gradient design perpendicular to the impact direction can enhance the energy absorption performance of ROH,especially for ROH,with wall thickness increasing from the inside outwards.Compared to ROH with uniform wall thickness at the same relative density,ROH with a gradient design can increase the plateau stress by over half.With the elevation of impact velocity,the plateau stress and specific energy absorption exhibit an upward trend,aligning with the dynamic performance pattern observed in conventional honeycombs.The results can be used as a reference for the design and application of honeycomb and provide a new idea for developing more efficient and reliable energy-absorbing materials.
基金Supported by the National Basic Research Program of China under Grant No 2014CB340102
文摘To overcome the shortcomings of the traditional passive ranging technology based on image, such as poor ranging accuracy, low reliability and complex system, a new visual passive ranging method based on re-entrant coaxial optical path is presented. The target image is obtained using double cameras with coaxial optical path. Since there is imaging optical path difference between the cameras, the images are different. In comparison of the image differences, the target range could be reversed. The principle of the ranging method and the ranging model are described. The relationship among parameters in the ranging process is analyzed quantitatively. Meanwhile,the system composition and technical realization scheme are also presented. Also, the principle of the method is verified by the equivalent experiment. The experimental results show that the design scheme is correct and feasible with good robustness. Generally, the ranging error is less than 10% with good convergence. The optical path is designed in a re-entrant mode to reduce the volume and weight of the system. Through the coaxial design,the visual passive range of the targets with any posture can be obtained in real time. The system can be widely used in electro-optical countermeasure and concealed photoelectric detection.
基金the support of the National Natural Science Foundation of China(Grant No.42207199)Scientific Research Project of Education of Zhejiang Province(No.Y202351343)+1 种基金Zhejiang Postdoctoral Scientific Research Project(Grant Nos.ZJ2022155,ZJ2022156)Zhejiang Province International Science and Technology Cooperation Base Open Fund Project(IBGDP-2023-01)。
文摘The squeezing deformation of surrounding rock is an important factor restricting the safe construction and long-term operation of tunnels when a tunnel passes through soft strata with high ground stress.Under such soft rock geological conditions,the large deformation of the surrounding rock can easily lead to the failure of supporting structures,including shotcrete cracks,spalling,and steel arch distortion.To improve the lining support performance during the large deformation of squeezed surrounding rock,this work selects aluminum foam with densities of 0.25 g/cm3,0.42 g/cm3 and 0.61 g/cm3 as the buffer layer material and carries out uniaxial confined compression tests.Through the evaluation and analysis of energy absorption and the comparison of the yield pressure of aluminum foam with those of other cushioning materials and yield pressure support systems,the strength,deformation and energy absorption of aluminum foam with a density of 0.25 g/cm3 meet the yield pressure performance requirements.The numerical model of the buffer layer yielding support system is then established via the finite element analysis software ABAQUS,and the influence of the buffer layer setting on the lining support is analyzed.Compared with the conventional support scheme,the addition of an aluminum foam buffer layer can reduce the stress and deformation of the primary support and secondary lining.The maximum and minimum principal stresses of the primary support are reduced by 13%and 15%,respectively.The maximum and minimum principal stresses of the secondary lining are reduced by 15%and 12%,respectively,and the displacement deformation of the secondary lining position is reduced by 15%.In summary,the application of aluminum foam buffer layer can reduce the stress and deformation of the primary support and secondary lining,improve the stress safety of the support and reduce the deformation of the support.
基金supported by the National Natural Science Foundation of China(Grant No.11804288)the Natural Science Foundation of Henan(Grant No.232300420120)。
文摘The Casimir pressure plays an important role in the adhesion stability of nanofilms at submicro scales.In this work,the Casimir pressure of peptide films deposited on a layered substrate is investigated.Three types of semi-infinite substrates,i.e.,silica,silicon and gold,are considered.The buffer layer between the peptide film and substrate consists of silicon or silica.The switching sign of the Casimir pressure can be controlled in a region ranging from about 130 nm to 1000 nm,depending on the thickness of the buffer layer and the substrate.The results suggest that the critical thickness of peptide films for Casimir equilibrium increases(or decreases)by increasing the thickness of the silicon(or silica)buffer film.The influences of wetting and electrolyte screening on the Casimir pressure are also investigated.Our finding provides a theoretical guide for the adhesion stability of peptide films in organic electronics.
基金funded by the National Natural Science Foundation of China(No.62305041)the Natural Science Foundation of Liaoning Province(No.2023-MS-103)。
文摘Stochastic optical reconstruction microscopy(STORM),as a typical technique of single-molecule localization microscopy(SMLM),has overcome the diffraction limit by randomly switching fluorophores between fluorescent and dark states,allowing for the precise localization of isolated emission patterns and the super-resolution reconstruction from millions of localized positions of single fluorophores.A critical factor influencing localization precision is the photo-switching behavior of fluorophores,which is affected by the imaging buffer.The imaging buffer typically comprises oxygen scavengers,photo-switching reagents,and refractive index regulators.Oxygen scavengers help prevent photobleaching,photo-switching reagents assist in facilitating the conversion of fluorophores,and refractive index regulators are used to adjust the refractive index of the solution.The synergistic interaction of these components promotes stable blinking of fluorophores,reduces irreversible photobleaching,and thereby ensures high-quality super-resolution imaging.This review provides a comprehensive overview of the essential compositions and functionalities of imaging buffers used in STORM,serving as a valuable resource for researchers seeking to select appropriate imaging buffers for their experiments.
基金Project(52202426)supported by the National Natural Science Foundation of ChinaProjects(15205723,15226424)supported by the Research Grants Council of the Hong Kong Special Administrative Region,China。
文摘Maglev trains experience significant aerodynamic effects when passing through tunnels.A moving model test was conducted to explore the practical effects of speed reduction and entrance buffer structures on mitigating tunnel/maglev aerodynamic effects.It is found that both have an overall positive effect on mitigating the aerodynamic environment inside and outside the tunnel.Trains operating at 200 km/h show a 49.8%decrease in peak-to-peak pressure and a 50.7%decrease in transient pressure instability on inner walls compared to those at 280 km/h.Lower speeds resulted in a 65.6%decrease in amplitude and a 24.5%decrease in decay rate,both of which are parameters for exponential fittings of pressure peaks that decay naturally after the train leaves.The buffer structures result in a reduction of up to 25.7%in the maximum positive pressure and a 29.0%decrease in transient pressure instability.Additionally,a reduction in amplitude of up to 21.2%and a 32.2%increase in decay rate were observed with the use of buffer structures.Nevertheless,it is difficult to conclude direct correlations between the maximum pressure,peak-to-peak values,etc.,and the speeds or buffer structures due to the complex wave propagation in tunnels.However,speed reduction and buffer structures are proven to be effective in reducing the micro-pressure wave levels with a simpler monotonic relationship.
基金This work was supported by the German BMBF (No.05P21UMFN2)
文摘Man-made superheavy elements(SHE)are produced as energetic recoils in complete-fusion reactions and need to be thermalized in a gas-filled chamber for chemical studies.The ever-shorter half-lives and decreasing production rates of the elements beyond Fl(atomic number Z=114)-the heaviest element chemically studied today-require the development of novel techniques for quantitative thermalization and fast extraction efficiency.The Universal high-density gas stopping Cell(UniCell),currently under construction,was proposed to achieve this.Within this work,we propose an Ion Transfer by Gas Flow(ITGF)device,which serves as a UniCell ejector to interface with a gas chromatography detector array for chemical studies.Detailed parameter optimizations,using gas dynamics and Monte Carlo ion-trajectory simulations,promise fast(within a few ms)and highly efficient(up to 100%)ion extraction across a wide mass range.These ions can then be transmitted quantitatively through the ITGF into the high-pressure environment needed for further chemical studies.
基金supported by National Key R&D Program of China(Grant No.2024YFD1501600)the National Natural Science Foundation of China(Grants No.42071025,42371075)the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.2023240).
文摘Temperate forests exert significant biogeophysical influences on local and regional climates through modulating the energy and moisture exchanges between the land surface and the atmosphere,thereby serving as crucial barriers with significant buffering impacts on the productivity of adjacent agricultural ecosystems.However,the extent and underlying mechanisms of these biogeophysical and buffering effects of temperate forest barriers remains insufficiently understood.In this study,we integrated the dynamic crop model Noah-MP-Crop with the Weather Research and Forecasting(WRF)model to investigate the biogeophysical climate regulation of temperate forests and its buffering effects on crop yields in adjacent agricultural lands across Northeast China.Our findings revealed that temperate forest barriers induced significant local climate effects by cooling air and surface temperatures and reducing wind speeds within forested areas during the growing season,while also regulating non-local climate,particularly by altering regional precipitation patterns,2 m water vapor mixing ratio(Q2),and soil moisture,predominantly in adjacent cropland areas.Furthermore,these forest barriers were found to modulate climate extremes,through affecting maximum temperature and wind speed on a local scale,as well as both maximum and minimum Q2 in non-local croplands.Our study also observed that temperate forest barriers,through biogeophysical climate regulation,enhanced GPP,NPP,and grain yields across most cropland areas.This productivity boost was especially pronounced,with yield increases up to 20%in certain regions during the extreme drought conditions of 2017,underscoring the critical role of temperate forest barriers in sustaining and enhancing crop yields under severe climatic stress.Our findings underscore the significant buffering effects of temperate forest barriers on regional agricultural production,having important implications for climate adaptation strategies aimed at bolstering agricultural resilience in the face of increasing climate variability and extremes.
基金supported in part by the National Natural Science Foundation of China under Grant No.52175490.
文摘The shop scheduling problem with limited buffers has broad applications in real-world production scenarios,so this research direction is of great practical significance.However,there is currently little research on the hybrid flow shop scheduling problem with limited buffers(LBHFSP).This paper deeply investigates the LBHFSP to optimize the goal of the total completion time.To better solve the LBHFSP,a multi-level subpopulation-based particle swarm optimization algorithm(MLPSO)is proposed,which is founded on the attributes of the LBHFSP and the shortcomings of the basic PSO(particle swarm optimization)algorithm.In MLPSO,firstly,considering the impact of the limited buffers on the process of subsequent operations,a specific circular decoding strategy is developed to accommodate the characteristics of limited buffers.Secondly,an initialization strategy based on blocking time is designed to enhance the quality and diversity of the initial population.Afterward,a multi-level subpopulation collaborative search is developed to prevent being trapped in a local optimum and improve the global exploration capability.Additionally,a local search strategy based on the first blocked job is designed to enhance the MLPSO algorithm’s exploitation capability.Lastly,numerous experiments are carried out to test the performance of the proposed MLPSO by comparing it with classical intelligent optimization and popular algorithms in recent years.The results confirm that the proposed MLPSO has an outstanding performance when compared to other algorithms when solving LBHFSP.
基金supported by the Fund of Xuzhou Science and Technology Key R&D Program(Social Development)Project(No.KC22289)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX22_2783).
文摘Aqueous zinc-ion batteries(AZIBs)have developed rapidly in recent years but still face several challenges,including zinc dendrites growth,hydrogen evolution reaction,passivation and corrosion.The pH of the electrolyte plays a crucial role in these processes,significantly impacting the stability and reversibility of Zn^(2+)deposition.Therefore,pH-buffer tris(hydroxymethyl)amino methane(tris)is chosen as a versatile electrolyte additive to address these issues.Tris can buffer electrolyte pH at Zn/electrolyte interface by protonated/deprotonated nature of amino group,optimize the coordination environment of zinc solvate ions by its strong interaction with zinc ions,and simultaneously create an in-situ stable solid electrolyte interface membrane on the zinc anode surface.These synergistic effects effectively restrain dendrite formation and side reactions,resulting in a highly stable and reversible Zn anode,thereby enhancing the electrochemical performance of AZIBs.The Zn||Zn battery with 0.15 wt%tris additives maintains stable cycling for 1500 h at 4 mA·cm^(−2) and 1120 h at 10 mA·cm^(−2).Furthermore,the Coulombic efficiency reaches~99.2%at 4 mA·cm^(−2)@1 mAh·cm^(−2).The Zn||NVO full batteries also demonstrated a stable specific capacity and exceptional capacity retention.
文摘Photocatalytic hydrogen peroxide(H_(2)O_(2))production offers a sustainable route to convert water and oxygen into H_(2)O_(2)using solar energy.However,achieving long-term stability in photocatalysts remains a critical challenge due to mismatched kinetics between oxygen reduction(ORR)and water oxidation(WOR),which leads to hole accumulation and oxidative degradation.Here,we report a redox-mediated strategy to address this bottleneck by designing a hydroquinone-embedded covalent organic framework(Tz-QH-COF)that enables reversible hole buffering and kinetic balance.The hydroquinone(QH)units act as dynamic hole reservoirs,capturing excess holes during ORR and converting to benzoquinone(Q),which is regenerated to QH via WOR,thereby preventing oxidative decomposition.This reversible QH/Q cycle,directly visualized through in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy,ensures unmatched stability,achieving continuous H_(2)O_(2) production for 528 h(22 d)with an accumulated yield of 18.6 mmol L^(–1)—the highest reported duration for organic photocatalysts.Density functional theory calculations reveal that the QH units exhibit a strong oxygen adsorption energy and favorable two-electron ORR/WOR pathways with low energy barriers.The synergy between experimental and theoretical insights elucidates a redox-mediated charge-balance mechanism,advancing the design of robust photocatalysts for solar-driven H_(2)O_(2) synthesis.
基金Sponsored by Guizhou Provincial Key Technology R&D Program“A Study on the Conservation Model with Technology and Sustainable Development Demonstration of the World Natural Heritages in Guizhou”(2202023 QKHZC)the China Overseas Expertise Introduction Project for Discipline Innovation(China 111 Project)(D17016).
文摘The buffer zone of a World Natural Heritage Site constitutes a critical element of the heritage site protection system.It not only functions as an ecological security barrier,but also significantly influences the visual integrity and aesthetic value of the core area’s landscape.Given the rapid development of transportation infrastructure,particularly the growing number of high-speed railways traversing ecologically sensitive regions,the scientific assessment of their impact on the landscape environment of heritage sites has emerged as a pivotal concern in heritage conservation and regional development.This study focused on the section of the Guiyang-Nanning High-Speed Railway that traverses the buffer zone of the Libo World Natural Heritage Site in Guizhou Province.Beginning with five primary indicators,including natural landscape and aesthetic value,geological geomorphology and Earth history value,biodiversity value,integrity and protection management,and impact on ecological environment,a visual landscape impact assessment system for high-speed railways was developed based on the analytic hierarchy process(AHP)and the fuzzy comprehensive evaluation method(FCE).Through expert scoring,hierarchical weight calculation,and fuzzy membership degree analysis,a comprehensive assessment was conducted on the landscape ecological quality,visual coordination,and aesthetic perception within the buffer zone following the construction of high-speed railways.The findings indicate that the construction of the Guiyang-Nanning High-Speed Railway generally harmonizes well with the landscape environment of the heritage site.The level of visual disturbance remains within an acceptable range and has not significantly damaged the overall aesthetic value or authenticity of the heritage site.Although the integrity of the landscape in certain local areas has experienced a slight decline due to the exposure of bridge and slope structures,the adverse effects have been effectively mitigated through engineering interventions such as vegetation restoration and color coordination.This study innovatively integrates the AHP with fuzzy mathematics methods to achieve a comprehensive evaluation that combines both qualitative and quantitative approaches.This integration provides a scientifically grounded analytical path and a practical technical framework for assessing the visual impact of linear infrastructure projects,such as high-speed railways,within the buffer zones of World Heritage Sites.The findings offer valuable insights for the protection of landscapes and the sustainable development of infrastructure in heritage sites.
基金supported by the National Key Research and Development Program of China(No.2021YFA0715600)the National Natural Science Foundation of China(Nos.62274125,52192611)+2 种基金the Guangdong Basic and Applied Basic Research Fund(No.2023A1515030084)the Key Research and Development Program of Shaanxi Province(Grant No.2024GX-YBXM-410)the fund of the State Key Laboratory of Solidification Processing in NWPU(No.SKLSP202220).
文摘Optimizing the orientation of β-Ga_(2)O_(3) has emerged as an effective strategy to design high-performance β-Ga_(2)O_(3) device,but the orientation growth mechanism and approach have not been revealed yet.Herein,by employing AlN buffer layer,the highly preferred orientation of β-Ga_(2)O_(3)(100)film rather than(-201)film is realized on 4H-SiC substrate at low sputtering power and temperature.Because β-Ga_(2)O_(3)(100)film exhibits a slower growth speed than(-201)film,the former possesses the higher dangling bond density and the lower nucleation energy,and a large conversion barrier exists between these two ori-entations.Moreover,the AlN buffer layer can suppress the surface oxidation of the 4H-SiC substrate and eliminate the strain of β-Ga_(2)O_(3)(100)film,which further reduces the nucleation energy and en-larges the conversion barrier.Meanwhile,the AlN buffer layer can increase the oxygen vacancy formation energy and decrease the oxygen vacancy concentration of β-Ga_(2)O_(3)(100)film.Consequently,the solar-blind photodetector based on the oriented film exhibits the outstanding detectivity of 1.22×10^(12) Jones and photo-to-dark current ratio of 1.11×10^(5),which are the highest among the reported β-Ga_(2)O_(3) solar-blind photodetector on the SiC substrate.Our results offer in-depth insights into the preferred orientation growth mechanism,and provide an effective way to design high-quality β-Ga_(2)O_(3)(100)orientation film and high-performance solar-blind photodetector.
