Traditional impact protection structures(IPSs)dissipate impact energy according to the plastic dissipation mechanism,which is only effective for single impacts due to the irreversible deformation of structures.To achi...Traditional impact protection structures(IPSs)dissipate impact energy according to the plastic dissipation mechanism,which is only effective for single impacts due to the irreversible deformation of structures.To achieve multi-impact protection,this paper proposes a novel chiral periodic structure with the deformation self-recovery function and the high energy conversion efficiency based on the flexoelectric mechanism.A theoretical model is formulated on the electromechanical responses of a flexoelectric beam under rotational boundaries.The equivalent stiffness and damping characteristics are subsequently derived to construct the electromechanical responses of the structure under constant velocity and mass impacts.Discussions are addressed for the influence of the structural scale effect and resistance on the electromechanical responses.The results show that the energy conversion efficiency increases by 2 to 3 orders of magnitude,reaching as high as 85.3%,which can match well with those of structures reported in the literature based on the plastic energy dissipating mechanism.展开更多
Blocking rockfalls directly by reinforced concrete(RC) flat sheds with thick sand cushions is an outdated method. Such conventional sheds typically accumulate rock heavily, and become progressively damaged and are dif...Blocking rockfalls directly by reinforced concrete(RC) flat sheds with thick sand cushions is an outdated method. Such conventional sheds typically accumulate rock heavily, and become progressively damaged and are difficult to repair, and are very costly. To address these problems, we propose a new structure called a Graded Dissipating Inclined Steel Rock(GDISR) shed that utilizes the graded energy dissipation method. Here, we study the dynamic response of the GDISR shed with model test and numerical simulation, and give its optimization design combining with a practical engineering case. Our results show that the optimized modular E-block and corrugated steel tube can deform to sufficiently absorb the energy of different impact intensities. This efficiently and economically provides GDISR sheds with two security lines. Compared with conventional RC sheds, GDISR sheds with optimal incline have a more efficient anti-impact function, are faster and easier to repair, and are much simpler and cheaper to build.展开更多
Based on the matching conditions of different fluid regions, the eigenfunction expansion method is used to develop a theoretical formula for wave reflection in front of the perforated structure with a partially slit f...Based on the matching conditions of different fluid regions, the eigenfunction expansion method is used to develop a theoretical formula for wave reflection in front of the perforated structure with a partially slit front wall. The accuracy of the solution is verified by comparing the numerical results with experimental data. In addition, a new hydraulic design method is developed by derivation of the theoretical formula with respect to the porosity of the slit wall, and the results of this design method is drafted for harbour engineers to use.展开更多
Purpose:The aim of the present study was to determine the effects of an upper body compression garment(UBCG)on thermoregulatory responses during cycling in a controlled laboratory thermoneutral environment(~23℃).A se...Purpose:The aim of the present study was to determine the effects of an upper body compression garment(UBCG)on thermoregulatory responses during cycling in a controlled laboratory thermoneutral environment(~23℃).A secondary aim was to determine the cardiovascular and perceptual responses when wearing the garment.Methods:Sixteen untrained participants(age:21.3±5.7 years;peak oxygen consumption(V02 peak):50.88±8.00 mL/min/kg;mean±SD)performed 2 cycling trials in a thermoneutral environment(~23℃)wearing either UBCG or control(Con)garment.Testing consisted of a 5-min rest on a cycle ergometer,followed by 4 bouts of cycling for 14-min at ~50%VO2 peak,with 1-min rest between each bout.At the end of these bouts there was 10-min of passive recovery.During the entire protocol rectal temperature(Trec),skin temperature(Tskin),mean body temperature(Tbody),and heat storage(HS)were measured.Heart rate(HR),VO2,pH,hematocrit(Hct),plasma electrolytes,weight loss(Wloss),and perceptual responses were also measured.Results:There were no significant differences between garments for Tskin,HS,HR,VO2,pH,Hct,plasma electrolyte concentration,Wloss,and perceptual responses during the trial.Trec did not differ between garment conditions during rest,exercise,or recovery although a greater reduction in Trec wearing UBCG(p=0.01)was observed during recovery.Lower Tbody during recovery was found when wearing UBCG(36.82℃±0.30℃ vs.36.99℃±0.24℃).Conclusion:Wearing a UBCG did not benefit thermoregulatory,cardiovascular,and perceptual responses during exercise although it was found to lower Tbody during recovery,which suggests that it could be used as a recovery tool after exercise.展开更多
Theperformanceof a structurally dissipating rock-shed(SDR)depends largely onthecapacityofitsenergy dissipators.At present,mostenergy dissipatorsare made of metals,which dissipateenergy by unrecoverable plastic deforma...Theperformanceof a structurally dissipating rock-shed(SDR)depends largely onthecapacityofitsenergy dissipators.At present,mostenergy dissipatorsare made of metals,which dissipateenergy by unrecoverable plastic deformation.Therefore,they are not able to recover their energy-dissipation capacity after deformation under rockfall impact.However,a rockfall usually disintegrates into pieces when it rolls down from a higher position and results in multiple rockfall impacts.An energy dissipator with self-recovery capability is therefore more suitable for ensuring the safety of SDRs.Replacing metal with polyurethane(a hyperelastic material with remarkable self-recovery capability)can provide self-recovery capability for energy dissipators,making them more suitable for resisting multiple rockfall impacts.In this work,polyurethane was manufactured into twotypes ofenergy dissipators:cylindrical and cubical.Full-scale falling rock impact testsand dynamic numerical simulationswereconducted to study the mechanical response of the energy dissipators.In addition,in order to ensure the accuracy of the simulation,the dynamic mechanical properties of the polyurethanewere tested and its dynamic constitutive model was established.The experimental and simulation tests have clarified the advantages of the polyurethane energy dissipator.We also summarized the practical considerations in the design of energy dissipators.展开更多
Rapid population growth and major trends of world economy growth have led to significant energy needs in our country. Benin, Gulf of Guinea country, although with a significant coastal network powered by potential ene...Rapid population growth and major trends of world economy growth have led to significant energy needs in our country. Benin, Gulf of Guinea country, although with a significant coastal network powered by potential energy from breaking waves, has experienced a deficit and a critical energy instability, marked by recurrent power cuts and disruption of the national economy. To ensure the integration of this source of renewable energy in the Benin energy mix and sustainably reduce the energy deficit in progress, this work has aimed to study the dissipation of wave energy at the bathymetric breaking in the breakers zone of Cotonou coast. Sea conditions and the statistics parameters of the breaking waves under perturbation effect of the seabed were evaluated to predict the beginning of the breaking. The modeling is based on the Navier-Stokes equation in which the viscosity and the interactions between the molecules of the oceanic fluid are neglected. The nonlinear wave dispersion relation is also used. The results obtained for this purpose showed that water particles have an almost parabolic motion during their fall;their velocity is higher than those of the early breaking. In this area, the waves dissipate about 80% of their energy: it generates turbulence which leads to a strong setting in motion of sediments.展开更多
The high-speed railway track-bridge system(HSRTBS)is susceptible to damage under the effects of earthquakes,thus threatening the safety of running trains.To improve the seismic performance of HSRTBS and reduce damage ...The high-speed railway track-bridge system(HSRTBS)is susceptible to damage under the effects of earthquakes,thus threatening the safety of running trains.To improve the seismic performance of HSRTBS and reduce damage to the system,a replaceable X-shaped Energy Dissipating Steel Damper(X-EDSD)is proposed,which contains the energy-dissipating component(EDC)to dissipate the earthquake energy.Cyclic tests were performed to obtain the hysteretic performance of the EDC and X-EDSD,and a test-validated numerical model was developed to conduct parametric analyses.The X-EDSD was simplified as a nonlinear spring element with hysteretic parameters and modeled into the numerical model of the HSRTBS for seismic dynamic analyses.The peak displacements of girder and rail decreased by approximately 48.1%and 47.7%,respectively.The peak deflections of the fasteners,cement asphalt mortar layer and sliding layer were reduced by 70.4%,70.8%,and 86.1%,respectively.A comprehensive consideration of the system response control-economic cost ratio coefficient R_(pe)is proposed,and the optimal thickness of 14.94 mm is obtained by applying cubic term coefficient fitting according to 5 groups of steel plate thickness data for the specific case study in this paper.The method can be used for cost-informed X-EDSD-selection for seismic mitigation of HSRTBS.展开更多
Objective: The objective of this study is to evaluate the efficacy and safety of the clearing the lung and dissipating phlegm method in the treatment of acute exacerbation of chronic obstructive pulmonary disease(COPD...Objective: The objective of this study is to evaluate the efficacy and safety of the clearing the lung and dissipating phlegm method in the treatment of acute exacerbation of chronic obstructive pulmonary disease(COPD) and to provide evidence for the treatment of the disease. Materials and Methods: Literature was searched from the United States National Library of Medicine(PubMed), Embase, Cochrane Library, China National Knowledge Infrastructure, Wanfang Database(Wanfang), and the Full?Text Database of Chinese Scientific and Technical Periodicals(VIP).A comprehensive collection was made of randomized controlled trials(RCTs) before June 2018, in which the treatment groups used either the clearing the lung and dissipating phlegm formulas only or combined it with routine Western medicine therapy, and the control group adopted routine Western medicine therapy only for the acute exacerbation of COPD. The Cochrane risk of bias method was used to evaluate the quality of the literature. The data were analyzed and retrieved independently by two reviewers before meta?analysis was carried out with RevMan 5.3 software to evaluate the primary outcome measures, including the total clinical effective rate, and the secondary outcome measures such as the pulmonary function(forced vital capacity [FVC], forced expiratory volume in the 1 s [FEV1], percentage of FEV1 [FEV1%], and FEV1/FVC)and blood gases(PaO_2 and PaCo_2). Results: A total of 13 RCTs involving 990 patients(496 in the treatment group and 494 in the control group)were included in this study. Meta?analysis revealed significant difference in the efficacy of the group that adopted solely the routine Western medicine method and the group that combined the Western medicine with the clearing the lung and dissipating phlegm method. Outcome measures including the pulmonary function(FVC, FEV1, FEV1%, and FEV1/FVC) and the blood gases(PaO_2 and PaCo_2) were significantly improved as compared to the control group(P < 0.00001). However, adverse effects in the treatment group using combined traditional Chinese medicine were not reported due to the short observation time of the study. Conclusion: The clearing the lung and dissipating phlegm method can improve the efficacy in the treatment of acute exacerbation of COPD, the outcome measures of the pulmonary function and the blood gases,as well as the life quality of the patients. However, due to the fact that the existing studies are generally of poor quality in which randomization and its implementation were not properly carried out, more high?quality RCTs are necessary to confirm the findings of this study.展开更多
A multi-physics approach was used to quantify the effect of process parameters (laser power, scanning speed, hatch spacing, and scanning strategy) on the thermal history and corresponding microstructure evolution of T...A multi-physics approach was used to quantify the effect of process parameters (laser power, scanning speed, hatch spacing, and scanning strategy) on the thermal history and corresponding microstructure evolution of Ti-25Nb (at%) alloy during the dual-track selective laser melting (SLM) process. Simulation results reveal that during the dual-track SLM process, increasing laser power results in greater thermal accumulation, leading to a molten pool of larger volume and coarser grains. Reducing scanning speed enhances remelting and promotes cellular growth at the top of molten pool, whereas faster scanning speed leads to rougher melt tracks and finer grains. Notably, hatch spacing significantly influences the molten pool dimensions and microstructures, and smaller hatch spacing promotes remelting. Furthermore, the orientations of grains in the second track during zigzag scanning differ markedly from those in the first track. More importantly, compared with those after the first track, both the temperature gradient and cooling rate at the boundaries of remelting molten pool are reduced after the second track scanning, resulting in slower interface velocity and significant change in solidification microstructure. This research provides a theoretical foundation for controlling non-equilibrium microstructure and offering novel insights into the optimization of SLM process parameters of titanium alloys.展开更多
To explore the distribution law of the temperature field in the motor pump and the influence of the fanshaped DC channel with spoiler in the pump housing on its heat dissipation performance.This study takes the arc-ge...To explore the distribution law of the temperature field in the motor pump and the influence of the fanshaped DC channel with spoiler in the pump housing on its heat dissipation performance.This study takes the arc-gear type hydraulicmotor pump as the research object.In COMSOL,a coupled heat transfer simulationmodel of themotor pump’s fluid-solid coupling is established,and the internal temperature field characteristics are analyzed.To improve the heat dissipation effect of the motor pump,it is proposed to arrange spoiler in the fan-shaped DC channel of the pump housing to enhance heat dissipation.Three types of spoilers,namely,wing-shaped,inclined rectangle-shaped,and wave-shaped,are designed.The simulation results show that when the motor pump operates under rated conditions,due to the poor heat dissipation environment inside the motor pump,the high-temperature areas of the motor pump are concentrated in the rotor and permanent magnet parts.After arranging the spoiler,the turbulent kinetic energy and vorticity in the fan-shaped DC channel of the pump housing are significantly enhanced.All three spoiler structures can reduce the maximum temperature of each component of the motor.According to the comprehensive performance evaluation criterion(PEC),the inclined rectangle-shaped structure has the best comprehensive heat transfer performance(PEC=1.114),while the wave-shaped structure has higher heat transfer efficiency but greater pressure loss.The wing-shaped structure has relatively limited enhancement effect on heat dissipation.This study systematically quantifies the influence of different spoiler structures on heat dissipation performance and flowresistance characteristics,providing a solution for enhancing the heat dissipation of the motor pump.展开更多
China has limited acaricide options for tea plantations.Cyetpyrafen,a novel domestic acaricide with high efficacy,low toxicity and a negative temperature coefficient,offers an alternative for tea pest control;however,...China has limited acaricide options for tea plantations.Cyetpyrafen,a novel domestic acaricide with high efficacy,low toxicity and a negative temperature coefficient,offers an alternative for tea pest control;however,its residue fate in tea remains unclear.This study developed a method to simultaneously detect cyetpyrafen and its metabolites(M-309,M-325-1,and M-409-3)in different tea matrices to investigate their fate.Recoveries of compounds ranged from 73.4 to 106.2%with the relative standard deviations(RSDs)below 12.0%.During tea cultivation,the dissipation half-life of cyetpyrafen was 0.59 d,with M-309 as a major metabolite.The residues of cyetpyrafen and M-309 were affected by different processing stages,especially water loss and high temperatures during fixing,drying and withering.The total processing factors ranged from 1.39 to 1.71 for green tea and 1.48 to 2.28 for black tea(processed from fresh tea leaves sampled at 1,5,and 7 d),respectively.The leaching rates of cyetpyrafen from green tea and black tea into tea infusions were 7.4 and 6%,respectively.The risk associated with cyetpyrafen intake from tea consumption was low,with risk quotient values below 100%.However,theoretical calculation indicated potential harm to non-target organisms from its metabolites.This research provides a reference for the safe and efficient use of cyetpyrafen in tea gardens.展开更多
A critical scientific gap exists in quantifying the intrinsic mechanisms of shale mechanical property degradation induced by the combined effects of perforation(impact)and acidization—two core techniques for shale re...A critical scientific gap exists in quantifying the intrinsic mechanisms of shale mechanical property degradation induced by the combined effects of perforation(impact)and acidization—two core techniques for shale reservoir permeability enhancement.To address this gap,this study proposed an innovative coupled experimental framework integrating dynamic-static cyclic loading(to simulate perforation impact)and acid erosion.Static uniaxial compression tests were performed on treated damaged shale samples,with microstructural characterization via X-ray diffraction(XRD)and scanning electron microscopy(SEM).Key findings include:(1)The damage factor(characterized by longitudinal wave velocity)showed a significant positive correlation with acid concentration;(2)Combined damage(impact+acidization)caused far more severe mechanical deterioration than single damage modes—for instance,samples under combined damage with 20%hydrochloric acid exhibited a strength reduction to 158.97 MPa,with sharp decreases in peak strength and elastic modulus;(3)Damage reduced total energy and elastic strain energy of samples while increasing dissipated energy proportion,leading to more developed internal fractures and severe failure in combined damage samples;(4)Acidization promoted sample fragmentation into smaller debris,resulting in significantly higher fractal dimensions of acidized shale than other damage types under the same acid concentration;(5)XRD and SEM analyses confirmed that high-concentration acid erosion reduced shale carbonate content,and the synergy of mechanical pre-damage and chemical dissolution in combined damage accelerated acid-rock reactions,significantly increasing micro-interfacial pores and degrading shale structural integrity.This study’s innovation lies in establishing a coupled experimental framework that reproduces the actual“perforation-acidization”sequence,quantitatively revealing the synergistic degradation mechanism of shale mechanical properties under combined damage—providing a novel theoretical basis for optimizing shale reservoir stimulation parameters.展开更多
By combining the merits of radiative cooling(RC)and evaporation cooling(EC),radiative coupled evaporative cooling(REC)has attracted considerable attention for sub-ambient cooling purposes.However,for outdoor devices,t...By combining the merits of radiative cooling(RC)and evaporation cooling(EC),radiative coupled evaporative cooling(REC)has attracted considerable attention for sub-ambient cooling purposes.However,for outdoor devices,the interior heating power would increase the working temperature and fire risk,which would suppress their above-ambient heat dissipation capabilities and passive water cycle properties.In this work,we introduced a REC design based on an all-in-one photonic hydrogel for above-ambient heat dissipation and flame retardancy.Unlike conventional design RC film for heat dissipation with limited cooling power and fire risk,REC hydrogel can greatly improve the heat dissipation performance in the daytime with a high workload,indicating a 12.0℃lower temperature than the RC film under the same conditions in the outdoor experiment.In the nighttime with a low workload,RC-assisted adsorption can improve atmospheric water harvesting to ensure EC in the daytime.In addition,our REC hydrogel significantly enhanced flame retardancy by absorbing heat without a corresponding temperature rise,thus mitigating fire risks.Thus,our design shows a promising solution for the thermal management of outdoor devices,delivering outstanding performance in both heat dissipation and flame retardancy.展开更多
Understanding the shakedown behavior of fill material is paramount to estimate the deformation stability of railway subgrade.Especially for red mudstone fill material(RMF),the noticeable overestimation of bearing capa...Understanding the shakedown behavior of fill material is paramount to estimate the deformation stability of railway subgrade.Especially for red mudstone fill material(RMF),the noticeable overestimation of bearing capacity would be encountered if the conventional strength method is used.This paper presents the shakedown analysis on RMF,with a specific emphasis on the effect of water content.A series of cyclic triaxial tests with 50,000 loading cycles was conducted.Two-stage behavior of permanent deformation and dissipated energy responses was clearly characterized,from which an energy-based criterion was proposed to determine the shakedown limits.The proposed energy-based criterion was validated by examining its performance to various geomaterials including cohesive soils and unbound granular materials(UGMs).By applying the proposed method to RMF,the S-shape evolution curve was obtained in terms of shakedown limits with initial suction.Microfabric difference was believed as the main consequence of the S-shape mode.Demonstration was confirmed by the mercury intrusion porosimetry(MIP)and scanning electron microscope(SEM)analyses.By applying the proposed method to different geomaterials,an extensive comparison was made between the shakedown limits and the static shear strength.The ratio of shakedown limits to the static shear strength for saturated RMF specimen fell within the range of soft clays,while that of unsaturated specimen lies within the range of UGMs.展开更多
Nociceptive pain is a cardinal feature of traumatic and inflammatory bone diseases.However,whether and how nociceptors actively regulate the immune response during bone regeneration remains unclear.Here,we found that ...Nociceptive pain is a cardinal feature of traumatic and inflammatory bone diseases.However,whether and how nociceptors actively regulate the immune response during bone regeneration remains unclear.Here,we found that neutrophil-triggered nociceptive ingrowth functioned as negative feedback regulation to inflammation during bone healing.A unique Il4ra^(+)Ccl2^(high) neutrophil subset drove intense postinjury TRPV1^(+)nociceptive ingrowth,which in return dissipated inflammation by activating the production of pro-resolving mediator lipoxin A4(LXA4)in osteoblasts.Mechanistically,osteoblastic autophagy activated by nociceptor-derived calcitonin gene-related peptide(CGRP)suppressed the nuclear translocation of arachidonate 5-lipoxygenase(5-LOX)to favor the LXA4 biosynthesis.Moreover,in alveolar bone from patients with Type Ⅱ diabetes,we found diminished nociceptive innervation correlated with reduced autophagy,increased inflammation,and impaired bone formation.Activating nociceptive nerves by spicy diet or topical administration of a clinical-approved TRPV1 agonist showed therapeutic benefits on alveolar bone healing in diabetic mice.These results reveal a critical neuroimmune interaction underlying the inflammation-regeneration balance during bone repairing and may lead to novel therapeutic strategies for inflammatory bone diseases.展开更多
To enhance the mechanical reliability of dental prostheses under long-term service conditions,this study aimed to evaluate the fracture behavior and energy dissipation characteristics of three commonly used prosthetic...To enhance the mechanical reliability of dental prostheses under long-term service conditions,this study aimed to evaluate the fracture behavior and energy dissipation characteristics of three commonly used prosthetic materials,namely,zirconia ceramics(ZrO_(2)),cobalt-chromium alloy(Co-Cr),and titanium-zirconium alloy(Ti-13Zr),under various crack configurations.A three-dimensional finite element model of a single-crown prosthesis incorporating predefined cracks was established,and both axial and oblique multidirectional loads were applied.Using LS-DYNA software,the deformation patterns,principal stress distribution,and energy release characteristics during crack propagation were systematically analyzed.The experimental results indicate that Ti-13Zr alloy exhibited the highest crack resistance,making it particularly suitable for patients with insufficient bone volume or limited implant space.Co-Cr alloy demonstrated favorable structural stability and mechanical performance under high-load conditions.In contrast,due to its inherent brittleness,ZrO_(2)was more prone to rapid fracture propagation in long-span or high-stress scenarios,although it remains a preferred option for anterior esthetic zones and patients with metal sensitivities.Furthermore,the simulation outcomes were theoretically validated using Griffith's energy-based fracture criterion,reinforcing the accuracy of failure predictions based on principal stress analysis.This study elucidates the differences in clinical applicability among prosthetic materials and reveals their distinct fracture mechanisms,thereby providing a theoretical foundation for optimizing material selection and structural design.The findings contribute to improving the long-term safety and functional stability of implant-supported dental restorations.展开更多
To enhance the heat-dissipation capacity of infrared(IR)stealth structures in high-temperature environments,a selective heat emitter with multi-band thermal management is fabricated.This emitter comprises a hightemper...To enhance the heat-dissipation capacity of infrared(IR)stealth structures in high-temperature environments,a selective heat emitter with multi-band thermal management is fabricated.This emitter comprises a hightemperature-resistant titanium dioxide(TiO_(2))/hafnium dioxide(HfO_(2))/Cr/Ge/Mo multi-film-layer structure.Additionally,the thickness of each layer is determined by the transfer-matrix algorithm.The emissivity of the structure across the IR band is simulated,and its electric field distributions are analyzed across different wavelengths.The stealth-and heat-dissipation bands of the structure are calculated to confirm its overall stealth and heat-dissipation capabilities.The results reveal that the average emissivities of the fabricated TiO_(2)/HfO_(2)/Cr/Ge/Mo multi-film-layer structure decrease to 0.21 and 0.27 within 3-5 and 8-14μm atmospheric window bands,respectively,achieving the IR concealment effect.Conversely,the average emissivities of the structure increase to 0.56 and 0.80 within the 2.5-3 and 5-8μm non-atmospheric window(NAW)bands,respectively.These high-emissivity bands enhance radiative heat dissipation to reduce heat accumulation and further weaken the detection and characterization of thermal signals.The simulated thermal images confirm the IR-stealth effect of the structure within a wide temperature range.Moreover,its efficient NAW heat-dissipation capability improves its operating life in high-temperature environments.展开更多
Bolting steel angles at the bottom ends of columns provides a rapid and efficient method for repairing damaged structures,while also offering a viable approach to restore their potential bearing capacity.To validate t...Bolting steel angles at the bottom ends of columns provides a rapid and efficient method for repairing damaged structures,while also offering a viable approach to restore their potential bearing capacity.To validate the suitability of specific strengthening strategies,particularly the utilization of bolted steel angles,three reinforced concrete frame specimens were subjected to hysteresis testing.These specimens all featured RC columns strengthened with steel angle ends.Additionally,one control specimen without steel angle ends was included in the testing.The hysteresis effects of bolting steel angles were discussed in terms of typical failure mode,hysteresis and skeleton curves,stiffness degradation and energy dissipation.The experimental results revealed that the three specimens that had bolted steel angles exhibited ductile failure behavior.Through analysis of hysteresis and skeleton curves,it was observed that the frame demonstrated distinct plasticity,maintaining sufficient load-bearing capacity even after yielding and exhibiting superior displacement ductility performance.Considering equivalent viscous damping,the energy dissipation capacity of the RC frame increased linearly with drift and remained largely unaffected by structural damage.Therefore,bolting steel angles at specified cross-sections proved to be a viable technique for structural repair and restoration.展开更多
This paper proposes two types of integrated sound absorbing-insulating metamaterials with low thickness and efficient sound attenuation in the low-frequency bandwidth,i.e.,labyrinth-type metamaterial and multi-order r...This paper proposes two types of integrated sound absorbing-insulating metamaterials with low thickness and efficient sound attenuation in the low-frequency bandwidth,i.e.,labyrinth-type metamaterial and multi-order resonator metamaterial.The labyrinth-type metamaterial is designed through spatial dimension transfer,transferring the required dimension in the thickness direction to the planar thin layer.Based on the Helmholtz resonance,the metamaterial achieves noise reduction through the reflection of sound waves and the thermoviscous dissipation of holes and cavities.This mechanism enables its sound insulation performance to produce the same gain effect as absorption,thereby accomplishing the broadband absorbing-insulating integrated design.With a thickness of only 33 mm,it achieves both sound absorption and insulation effects over more than one octave.The multi-order resonator metamaterial has a larger working bandwidth than the labyrinth-type metamaterial.It is designed based on the multiorder resonance absorption mechanism,and consists of 9 different orders of resonator units.The metamaterial obtains a continuous sound absorption coefficient curve in the low-frequency range of 362–1712 Hz,and possesses high transmission loss(TL)above 346 Hz.In addition,this paper deeply explores the sound absorbing-insulating mechanism through the correlation analysis between the sound absorption coefficient and TL curves.The experimental results verify the continuous and efficient absorption effects of the two metamaterials,as well as their insulation performance that breaks the mass law.In low-frequency engineering applications,the two designed metamaterials demonstrate great potential and value at sub-wavelength dimensions.展开更多
There is a need for accurate prediction of heat and mass transfer in aerodynamically designed,non-Newtonian nanofluids across aerodynamically designed,high-flux biomedical micro-devices for thermal management and reac...There is a need for accurate prediction of heat and mass transfer in aerodynamically designed,non-Newtonian nanofluids across aerodynamically designed,high-flux biomedical micro-devices for thermal management and reactive coating processes,but existing work is not uncharacteristically remiss regarding viscoelasticity,radiative heating,viscous dissipation,and homogeneous–heterogeneous reactions within a single scheme that is calibrated.This research investigates the flow of Williamson nanofluid across a dynamically wedged surface under conditions that include viscous dissipation,thermal radiation,and homogeneous-heterogeneous reactions.The paper develops a detailed mathematical approach that utilizes boundary layers to transform partial differential equations into ordinary differential equations using similarity transformations.RK4 is the technique for gaining numerical solutions,but with the addition of ANNs,there is an improvement in prediction accuracy and computational efficiency.The study investigates the influence of wedge angle parameter,along with Weissenberg number,thermal radiation parameter and Brownian motion parameter,and Schmidt number,on velocity distribution,temperature distribution,and concentra-tion distribution.Enhanced Weissenberg numbers enhance viscoelastic responses that modify velocity patterns,but radiation parameters and thermophoresis have key impacts on thermal transfer phenomena.This research develops findings that are of enormous application in aerospace,biomedical(artificial hearts and drug delivery),and industrial cooling technology applications.New findings on non-Newtonian nanofluids under full flow systems are included in this work to enhance heat transfer methods in novel fluid-based systems.展开更多
基金Project supported by the National Natural Science Foundation of China(No.12272138)。
文摘Traditional impact protection structures(IPSs)dissipate impact energy according to the plastic dissipation mechanism,which is only effective for single impacts due to the irreversible deformation of structures.To achieve multi-impact protection,this paper proposes a novel chiral periodic structure with the deformation self-recovery function and the high energy conversion efficiency based on the flexoelectric mechanism.A theoretical model is formulated on the electromechanical responses of a flexoelectric beam under rotational boundaries.The equivalent stiffness and damping characteristics are subsequently derived to construct the electromechanical responses of the structure under constant velocity and mass impacts.Discussions are addressed for the influence of the structural scale effect and resistance on the electromechanical responses.The results show that the energy conversion efficiency increases by 2 to 3 orders of magnitude,reaching as high as 85.3%,which can match well with those of structures reported in the literature based on the plastic energy dissipating mechanism.
基金supported by the National Key Basic Research Program of China(2016YFB0201003)the National Natural Science Foundation of China(41672356)the 135 Strategic Program of the Institute of Mountain Hazards and Environment,CAS(SDS-135-1704)
文摘Blocking rockfalls directly by reinforced concrete(RC) flat sheds with thick sand cushions is an outdated method. Such conventional sheds typically accumulate rock heavily, and become progressively damaged and are difficult to repair, and are very costly. To address these problems, we propose a new structure called a Graded Dissipating Inclined Steel Rock(GDISR) shed that utilizes the graded energy dissipation method. Here, we study the dynamic response of the GDISR shed with model test and numerical simulation, and give its optimization design combining with a practical engineering case. Our results show that the optimized modular E-block and corrugated steel tube can deform to sufficiently absorb the energy of different impact intensities. This efficiently and economically provides GDISR sheds with two security lines. Compared with conventional RC sheds, GDISR sheds with optimal incline have a more efficient anti-impact function, are faster and easier to repair, and are much simpler and cheaper to build.
文摘Based on the matching conditions of different fluid regions, the eigenfunction expansion method is used to develop a theoretical formula for wave reflection in front of the perforated structure with a partially slit front wall. The accuracy of the solution is verified by comparing the numerical results with experimental data. In addition, a new hydraulic design method is developed by derivation of the theoretical formula with respect to the porosity of the slit wall, and the results of this design method is drafted for harbour engineers to use.
文摘Purpose:The aim of the present study was to determine the effects of an upper body compression garment(UBCG)on thermoregulatory responses during cycling in a controlled laboratory thermoneutral environment(~23℃).A secondary aim was to determine the cardiovascular and perceptual responses when wearing the garment.Methods:Sixteen untrained participants(age:21.3±5.7 years;peak oxygen consumption(V02 peak):50.88±8.00 mL/min/kg;mean±SD)performed 2 cycling trials in a thermoneutral environment(~23℃)wearing either UBCG or control(Con)garment.Testing consisted of a 5-min rest on a cycle ergometer,followed by 4 bouts of cycling for 14-min at ~50%VO2 peak,with 1-min rest between each bout.At the end of these bouts there was 10-min of passive recovery.During the entire protocol rectal temperature(Trec),skin temperature(Tskin),mean body temperature(Tbody),and heat storage(HS)were measured.Heart rate(HR),VO2,pH,hematocrit(Hct),plasma electrolytes,weight loss(Wloss),and perceptual responses were also measured.Results:There were no significant differences between garments for Tskin,HS,HR,VO2,pH,Hct,plasma electrolyte concentration,Wloss,and perceptual responses during the trial.Trec did not differ between garment conditions during rest,exercise,or recovery although a greater reduction in Trec wearing UBCG(p=0.01)was observed during recovery.Lower Tbody during recovery was found when wearing UBCG(36.82℃±0.30℃ vs.36.99℃±0.24℃).Conclusion:Wearing a UBCG did not benefit thermoregulatory,cardiovascular,and perceptual responses during exercise although it was found to lower Tbody during recovery,which suggests that it could be used as a recovery tool after exercise.
基金The research reported in this manuscript was funded by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA20030301)the International Partnership Program of the Chinese Academy of Sciences(Grant No.131551KYSB20180042)+1 种基金“Belt&Road”international cooperation team for the“Light of West”program of CAS(Su Lijun),Sichuan Science and Technology Program(Grant No.2021YJ0040)CAS“Light of West China”Program(Grant No.E0R2160).
文摘Theperformanceof a structurally dissipating rock-shed(SDR)depends largely onthecapacityofitsenergy dissipators.At present,mostenergy dissipatorsare made of metals,which dissipateenergy by unrecoverable plastic deformation.Therefore,they are not able to recover their energy-dissipation capacity after deformation under rockfall impact.However,a rockfall usually disintegrates into pieces when it rolls down from a higher position and results in multiple rockfall impacts.An energy dissipator with self-recovery capability is therefore more suitable for ensuring the safety of SDRs.Replacing metal with polyurethane(a hyperelastic material with remarkable self-recovery capability)can provide self-recovery capability for energy dissipators,making them more suitable for resisting multiple rockfall impacts.In this work,polyurethane was manufactured into twotypes ofenergy dissipators:cylindrical and cubical.Full-scale falling rock impact testsand dynamic numerical simulationswereconducted to study the mechanical response of the energy dissipators.In addition,in order to ensure the accuracy of the simulation,the dynamic mechanical properties of the polyurethanewere tested and its dynamic constitutive model was established.The experimental and simulation tests have clarified the advantages of the polyurethane energy dissipator.We also summarized the practical considerations in the design of energy dissipators.
文摘Rapid population growth and major trends of world economy growth have led to significant energy needs in our country. Benin, Gulf of Guinea country, although with a significant coastal network powered by potential energy from breaking waves, has experienced a deficit and a critical energy instability, marked by recurrent power cuts and disruption of the national economy. To ensure the integration of this source of renewable energy in the Benin energy mix and sustainably reduce the energy deficit in progress, this work has aimed to study the dissipation of wave energy at the bathymetric breaking in the breakers zone of Cotonou coast. Sea conditions and the statistics parameters of the breaking waves under perturbation effect of the seabed were evaluated to predict the beginning of the breaking. The modeling is based on the Navier-Stokes equation in which the viscosity and the interactions between the molecules of the oceanic fluid are neglected. The nonlinear wave dispersion relation is also used. The results obtained for this purpose showed that water particles have an almost parabolic motion during their fall;their velocity is higher than those of the early breaking. In this area, the waves dissipate about 80% of their energy: it generates turbulence which leads to a strong setting in motion of sediments.
基金supported by the National Key Research and Development Program of China(No.2022YFC3004304)the National Natural Science Foundation of China(Grant No.52378209)+1 种基金the Hunan Province Science and Technology Project Huxiang Young Talents Program(No.2023RC3057)the Xiaohe SciTech Talents Special Funding under Hunan Provincial Sci-Tech Talents Sponsorship Program(No.2023TJ-X66).
文摘The high-speed railway track-bridge system(HSRTBS)is susceptible to damage under the effects of earthquakes,thus threatening the safety of running trains.To improve the seismic performance of HSRTBS and reduce damage to the system,a replaceable X-shaped Energy Dissipating Steel Damper(X-EDSD)is proposed,which contains the energy-dissipating component(EDC)to dissipate the earthquake energy.Cyclic tests were performed to obtain the hysteretic performance of the EDC and X-EDSD,and a test-validated numerical model was developed to conduct parametric analyses.The X-EDSD was simplified as a nonlinear spring element with hysteretic parameters and modeled into the numerical model of the HSRTBS for seismic dynamic analyses.The peak displacements of girder and rail decreased by approximately 48.1%and 47.7%,respectively.The peak deflections of the fasteners,cement asphalt mortar layer and sliding layer were reduced by 70.4%,70.8%,and 86.1%,respectively.A comprehensive consideration of the system response control-economic cost ratio coefficient R_(pe)is proposed,and the optimal thickness of 14.94 mm is obtained by applying cubic term coefficient fitting according to 5 groups of steel plate thickness data for the specific case study in this paper.The method can be used for cost-informed X-EDSD-selection for seismic mitigation of HSRTBS.
文摘Objective: The objective of this study is to evaluate the efficacy and safety of the clearing the lung and dissipating phlegm method in the treatment of acute exacerbation of chronic obstructive pulmonary disease(COPD) and to provide evidence for the treatment of the disease. Materials and Methods: Literature was searched from the United States National Library of Medicine(PubMed), Embase, Cochrane Library, China National Knowledge Infrastructure, Wanfang Database(Wanfang), and the Full?Text Database of Chinese Scientific and Technical Periodicals(VIP).A comprehensive collection was made of randomized controlled trials(RCTs) before June 2018, in which the treatment groups used either the clearing the lung and dissipating phlegm formulas only or combined it with routine Western medicine therapy, and the control group adopted routine Western medicine therapy only for the acute exacerbation of COPD. The Cochrane risk of bias method was used to evaluate the quality of the literature. The data were analyzed and retrieved independently by two reviewers before meta?analysis was carried out with RevMan 5.3 software to evaluate the primary outcome measures, including the total clinical effective rate, and the secondary outcome measures such as the pulmonary function(forced vital capacity [FVC], forced expiratory volume in the 1 s [FEV1], percentage of FEV1 [FEV1%], and FEV1/FVC)and blood gases(PaO_2 and PaCo_2). Results: A total of 13 RCTs involving 990 patients(496 in the treatment group and 494 in the control group)were included in this study. Meta?analysis revealed significant difference in the efficacy of the group that adopted solely the routine Western medicine method and the group that combined the Western medicine with the clearing the lung and dissipating phlegm method. Outcome measures including the pulmonary function(FVC, FEV1, FEV1%, and FEV1/FVC) and the blood gases(PaO_2 and PaCo_2) were significantly improved as compared to the control group(P < 0.00001). However, adverse effects in the treatment group using combined traditional Chinese medicine were not reported due to the short observation time of the study. Conclusion: The clearing the lung and dissipating phlegm method can improve the efficacy in the treatment of acute exacerbation of COPD, the outcome measures of the pulmonary function and the blood gases,as well as the life quality of the patients. However, due to the fact that the existing studies are generally of poor quality in which randomization and its implementation were not properly carried out, more high?quality RCTs are necessary to confirm the findings of this study.
基金Guangdong Basic and Applied Basic Research Foundation (2024A1515011873)Shenzhen Basic Research Project (JCYJ20241202123504007)Shenzhen Science and Technology Innovation Commission (KJZD20240903101400001, KJZD20240903102006009)。
文摘A multi-physics approach was used to quantify the effect of process parameters (laser power, scanning speed, hatch spacing, and scanning strategy) on the thermal history and corresponding microstructure evolution of Ti-25Nb (at%) alloy during the dual-track selective laser melting (SLM) process. Simulation results reveal that during the dual-track SLM process, increasing laser power results in greater thermal accumulation, leading to a molten pool of larger volume and coarser grains. Reducing scanning speed enhances remelting and promotes cellular growth at the top of molten pool, whereas faster scanning speed leads to rougher melt tracks and finer grains. Notably, hatch spacing significantly influences the molten pool dimensions and microstructures, and smaller hatch spacing promotes remelting. Furthermore, the orientations of grains in the second track during zigzag scanning differ markedly from those in the first track. More importantly, compared with those after the first track, both the temperature gradient and cooling rate at the boundaries of remelting molten pool are reduced after the second track scanning, resulting in slower interface velocity and significant change in solidification microstructure. This research provides a theoretical foundation for controlling non-equilibrium microstructure and offering novel insights into the optimization of SLM process parameters of titanium alloys.
基金supported by the Henan Provincial Key Research and Development Special Project(251111220200)Natural Science Foundation of Henan Province Project(252300420446).
文摘To explore the distribution law of the temperature field in the motor pump and the influence of the fanshaped DC channel with spoiler in the pump housing on its heat dissipation performance.This study takes the arc-gear type hydraulicmotor pump as the research object.In COMSOL,a coupled heat transfer simulationmodel of themotor pump’s fluid-solid coupling is established,and the internal temperature field characteristics are analyzed.To improve the heat dissipation effect of the motor pump,it is proposed to arrange spoiler in the fan-shaped DC channel of the pump housing to enhance heat dissipation.Three types of spoilers,namely,wing-shaped,inclined rectangle-shaped,and wave-shaped,are designed.The simulation results show that when the motor pump operates under rated conditions,due to the poor heat dissipation environment inside the motor pump,the high-temperature areas of the motor pump are concentrated in the rotor and permanent magnet parts.After arranging the spoiler,the turbulent kinetic energy and vorticity in the fan-shaped DC channel of the pump housing are significantly enhanced.All three spoiler structures can reduce the maximum temperature of each component of the motor.According to the comprehensive performance evaluation criterion(PEC),the inclined rectangle-shaped structure has the best comprehensive heat transfer performance(PEC=1.114),while the wave-shaped structure has higher heat transfer efficiency but greater pressure loss.The wing-shaped structure has relatively limited enhancement effect on heat dissipation.This study systematically quantifies the influence of different spoiler structures on heat dissipation performance and flowresistance characteristics,providing a solution for enhancing the heat dissipation of the motor pump.
基金financially supported by the National Key Research and Development Program of China(2022YFD1600803)the National Natural Science Foundation of China(31772077)+1 种基金the Yunnan Provincial Tea Industry Technology Innovation Center,China(202505AK340010)the Chinese Academy of Agricultural Sciences for Agricultural Science and Technology Innovation Program of Tea Research Institute(CAAS-ASTIP-2021-TRI)。
文摘China has limited acaricide options for tea plantations.Cyetpyrafen,a novel domestic acaricide with high efficacy,low toxicity and a negative temperature coefficient,offers an alternative for tea pest control;however,its residue fate in tea remains unclear.This study developed a method to simultaneously detect cyetpyrafen and its metabolites(M-309,M-325-1,and M-409-3)in different tea matrices to investigate their fate.Recoveries of compounds ranged from 73.4 to 106.2%with the relative standard deviations(RSDs)below 12.0%.During tea cultivation,the dissipation half-life of cyetpyrafen was 0.59 d,with M-309 as a major metabolite.The residues of cyetpyrafen and M-309 were affected by different processing stages,especially water loss and high temperatures during fixing,drying and withering.The total processing factors ranged from 1.39 to 1.71 for green tea and 1.48 to 2.28 for black tea(processed from fresh tea leaves sampled at 1,5,and 7 d),respectively.The leaching rates of cyetpyrafen from green tea and black tea into tea infusions were 7.4 and 6%,respectively.The risk associated with cyetpyrafen intake from tea consumption was low,with risk quotient values below 100%.However,theoretical calculation indicated potential harm to non-target organisms from its metabolites.This research provides a reference for the safe and efficient use of cyetpyrafen in tea gardens.
基金funded by the National Natural Science Foundation of China(No.52474120)the National Key Research and Development Program of China—2023 Key Special Project(No.2023YFC2907400)+1 种基金the Fundamental Research Funds for the Central Universities(No.2023CXQD045)the Hunan Provincial Natural Science Foundation for Distinguished Young Scholars(No.2023JJ10072).
文摘A critical scientific gap exists in quantifying the intrinsic mechanisms of shale mechanical property degradation induced by the combined effects of perforation(impact)and acidization—two core techniques for shale reservoir permeability enhancement.To address this gap,this study proposed an innovative coupled experimental framework integrating dynamic-static cyclic loading(to simulate perforation impact)and acid erosion.Static uniaxial compression tests were performed on treated damaged shale samples,with microstructural characterization via X-ray diffraction(XRD)and scanning electron microscopy(SEM).Key findings include:(1)The damage factor(characterized by longitudinal wave velocity)showed a significant positive correlation with acid concentration;(2)Combined damage(impact+acidization)caused far more severe mechanical deterioration than single damage modes—for instance,samples under combined damage with 20%hydrochloric acid exhibited a strength reduction to 158.97 MPa,with sharp decreases in peak strength and elastic modulus;(3)Damage reduced total energy and elastic strain energy of samples while increasing dissipated energy proportion,leading to more developed internal fractures and severe failure in combined damage samples;(4)Acidization promoted sample fragmentation into smaller debris,resulting in significantly higher fractal dimensions of acidized shale than other damage types under the same acid concentration;(5)XRD and SEM analyses confirmed that high-concentration acid erosion reduced shale carbonate content,and the synergy of mechanical pre-damage and chemical dissolution in combined damage accelerated acid-rock reactions,significantly increasing micro-interfacial pores and degrading shale structural integrity.This study’s innovation lies in establishing a coupled experimental framework that reproduces the actual“perforation-acidization”sequence,quantitatively revealing the synergistic degradation mechanism of shale mechanical properties under combined damage—providing a novel theoretical basis for optimizing shale reservoir stimulation parameters.
基金financially supported by the Science and Technology Innovation Program of Hunan Province(2024RC3003)the Central South University Innovation-Driven Research Programme(2023CXQD012)the Initiative for Sustainable Energy for its financial support。
文摘By combining the merits of radiative cooling(RC)and evaporation cooling(EC),radiative coupled evaporative cooling(REC)has attracted considerable attention for sub-ambient cooling purposes.However,for outdoor devices,the interior heating power would increase the working temperature and fire risk,which would suppress their above-ambient heat dissipation capabilities and passive water cycle properties.In this work,we introduced a REC design based on an all-in-one photonic hydrogel for above-ambient heat dissipation and flame retardancy.Unlike conventional design RC film for heat dissipation with limited cooling power and fire risk,REC hydrogel can greatly improve the heat dissipation performance in the daytime with a high workload,indicating a 12.0℃lower temperature than the RC film under the same conditions in the outdoor experiment.In the nighttime with a low workload,RC-assisted adsorption can improve atmospheric water harvesting to ensure EC in the daytime.In addition,our REC hydrogel significantly enhanced flame retardancy by absorbing heat without a corresponding temperature rise,thus mitigating fire risks.Thus,our design shows a promising solution for the thermal management of outdoor devices,delivering outstanding performance in both heat dissipation and flame retardancy.
基金support from the National Natural Science Foundation of China(Grant Nos.52278432 and 52478475)the Science and Technology Research and Development Plan of China National Railway Group Co.,Ltd.(Grant No.K2023G033)were greatly appreciated.
文摘Understanding the shakedown behavior of fill material is paramount to estimate the deformation stability of railway subgrade.Especially for red mudstone fill material(RMF),the noticeable overestimation of bearing capacity would be encountered if the conventional strength method is used.This paper presents the shakedown analysis on RMF,with a specific emphasis on the effect of water content.A series of cyclic triaxial tests with 50,000 loading cycles was conducted.Two-stage behavior of permanent deformation and dissipated energy responses was clearly characterized,from which an energy-based criterion was proposed to determine the shakedown limits.The proposed energy-based criterion was validated by examining its performance to various geomaterials including cohesive soils and unbound granular materials(UGMs).By applying the proposed method to RMF,the S-shape evolution curve was obtained in terms of shakedown limits with initial suction.Microfabric difference was believed as the main consequence of the S-shape mode.Demonstration was confirmed by the mercury intrusion porosimetry(MIP)and scanning electron microscope(SEM)analyses.By applying the proposed method to different geomaterials,an extensive comparison was made between the shakedown limits and the static shear strength.The ratio of shakedown limits to the static shear strength for saturated RMF specimen fell within the range of soft clays,while that of unsaturated specimen lies within the range of UGMs.
基金The National Natural Science Foundation of China(No.82130027,82301020,82100966)Young Elite Scientists Sponsorship Program by CAST(2024QNRC001)+5 种基金The China Postdoctoral Science Foundation(2023M732283)The National Key Research and Development Program of China(No.2023YFC2413600)The Shanghai Sailing Program(23YF1422000,21YF1424400)Innovative Research Team of High-level Local Universities in Shanghai(SHSMU-ZLCX20212400)Young Elite Scientists Sponsorship Program by CAST(2021QNRC001)Shanghai Pujiang Program(24PJD054).
文摘Nociceptive pain is a cardinal feature of traumatic and inflammatory bone diseases.However,whether and how nociceptors actively regulate the immune response during bone regeneration remains unclear.Here,we found that neutrophil-triggered nociceptive ingrowth functioned as negative feedback regulation to inflammation during bone healing.A unique Il4ra^(+)Ccl2^(high) neutrophil subset drove intense postinjury TRPV1^(+)nociceptive ingrowth,which in return dissipated inflammation by activating the production of pro-resolving mediator lipoxin A4(LXA4)in osteoblasts.Mechanistically,osteoblastic autophagy activated by nociceptor-derived calcitonin gene-related peptide(CGRP)suppressed the nuclear translocation of arachidonate 5-lipoxygenase(5-LOX)to favor the LXA4 biosynthesis.Moreover,in alveolar bone from patients with Type Ⅱ diabetes,we found diminished nociceptive innervation correlated with reduced autophagy,increased inflammation,and impaired bone formation.Activating nociceptive nerves by spicy diet or topical administration of a clinical-approved TRPV1 agonist showed therapeutic benefits on alveolar bone healing in diabetic mice.These results reveal a critical neuroimmune interaction underlying the inflammation-regeneration balance during bone repairing and may lead to novel therapeutic strategies for inflammatory bone diseases.
基金Funded by the National Key R&D Program of China(No.2023YFC2412300)the Technology Development Project of Shan-dong Weigao Orthopedic Materials Co.,Ltd.(No.20221h0074)the Independent Innovation Research Fund of Wuhan University of Technology(No.104972024ZHZXhp0027)。
文摘To enhance the mechanical reliability of dental prostheses under long-term service conditions,this study aimed to evaluate the fracture behavior and energy dissipation characteristics of three commonly used prosthetic materials,namely,zirconia ceramics(ZrO_(2)),cobalt-chromium alloy(Co-Cr),and titanium-zirconium alloy(Ti-13Zr),under various crack configurations.A three-dimensional finite element model of a single-crown prosthesis incorporating predefined cracks was established,and both axial and oblique multidirectional loads were applied.Using LS-DYNA software,the deformation patterns,principal stress distribution,and energy release characteristics during crack propagation were systematically analyzed.The experimental results indicate that Ti-13Zr alloy exhibited the highest crack resistance,making it particularly suitable for patients with insufficient bone volume or limited implant space.Co-Cr alloy demonstrated favorable structural stability and mechanical performance under high-load conditions.In contrast,due to its inherent brittleness,ZrO_(2)was more prone to rapid fracture propagation in long-span or high-stress scenarios,although it remains a preferred option for anterior esthetic zones and patients with metal sensitivities.Furthermore,the simulation outcomes were theoretically validated using Griffith's energy-based fracture criterion,reinforcing the accuracy of failure predictions based on principal stress analysis.This study elucidates the differences in clinical applicability among prosthetic materials and reveals their distinct fracture mechanisms,thereby providing a theoretical foundation for optimizing material selection and structural design.The findings contribute to improving the long-term safety and functional stability of implant-supported dental restorations.
基金The National Natural Science Foundation of China(No.52106099)the Science and Technology Development Joint Fundof Henan province(No.225200810077).
文摘To enhance the heat-dissipation capacity of infrared(IR)stealth structures in high-temperature environments,a selective heat emitter with multi-band thermal management is fabricated.This emitter comprises a hightemperature-resistant titanium dioxide(TiO_(2))/hafnium dioxide(HfO_(2))/Cr/Ge/Mo multi-film-layer structure.Additionally,the thickness of each layer is determined by the transfer-matrix algorithm.The emissivity of the structure across the IR band is simulated,and its electric field distributions are analyzed across different wavelengths.The stealth-and heat-dissipation bands of the structure are calculated to confirm its overall stealth and heat-dissipation capabilities.The results reveal that the average emissivities of the fabricated TiO_(2)/HfO_(2)/Cr/Ge/Mo multi-film-layer structure decrease to 0.21 and 0.27 within 3-5 and 8-14μm atmospheric window bands,respectively,achieving the IR concealment effect.Conversely,the average emissivities of the structure increase to 0.56 and 0.80 within the 2.5-3 and 5-8μm non-atmospheric window(NAW)bands,respectively.These high-emissivity bands enhance radiative heat dissipation to reduce heat accumulation and further weaken the detection and characterization of thermal signals.The simulated thermal images confirm the IR-stealth effect of the structure within a wide temperature range.Moreover,its efficient NAW heat-dissipation capability improves its operating life in high-temperature environments.
基金National Key R&D Program of China under Grant No.2023YFC3805100Technologies R&D Project of China Construction First Group Corporation Limited under Grant No.PT-2022-09National Natural Science Foundation of China under Grant No.52178126。
文摘Bolting steel angles at the bottom ends of columns provides a rapid and efficient method for repairing damaged structures,while also offering a viable approach to restore their potential bearing capacity.To validate the suitability of specific strengthening strategies,particularly the utilization of bolted steel angles,three reinforced concrete frame specimens were subjected to hysteresis testing.These specimens all featured RC columns strengthened with steel angle ends.Additionally,one control specimen without steel angle ends was included in the testing.The hysteresis effects of bolting steel angles were discussed in terms of typical failure mode,hysteresis and skeleton curves,stiffness degradation and energy dissipation.The experimental results revealed that the three specimens that had bolted steel angles exhibited ductile failure behavior.Through analysis of hysteresis and skeleton curves,it was observed that the frame demonstrated distinct plasticity,maintaining sufficient load-bearing capacity even after yielding and exhibiting superior displacement ductility performance.Considering equivalent viscous damping,the energy dissipation capacity of the RC frame increased linearly with drift and remained largely unaffected by structural damage.Therefore,bolting steel angles at specified cross-sections proved to be a viable technique for structural repair and restoration.
基金Project supported by the National Natural Science Foundation of China(No.52250287)the Outstanding Youth Science Fund Project of Shaanxi Province of China(No.2024JC-JCQN-49)。
文摘This paper proposes two types of integrated sound absorbing-insulating metamaterials with low thickness and efficient sound attenuation in the low-frequency bandwidth,i.e.,labyrinth-type metamaterial and multi-order resonator metamaterial.The labyrinth-type metamaterial is designed through spatial dimension transfer,transferring the required dimension in the thickness direction to the planar thin layer.Based on the Helmholtz resonance,the metamaterial achieves noise reduction through the reflection of sound waves and the thermoviscous dissipation of holes and cavities.This mechanism enables its sound insulation performance to produce the same gain effect as absorption,thereby accomplishing the broadband absorbing-insulating integrated design.With a thickness of only 33 mm,it achieves both sound absorption and insulation effects over more than one octave.The multi-order resonator metamaterial has a larger working bandwidth than the labyrinth-type metamaterial.It is designed based on the multiorder resonance absorption mechanism,and consists of 9 different orders of resonator units.The metamaterial obtains a continuous sound absorption coefficient curve in the low-frequency range of 362–1712 Hz,and possesses high transmission loss(TL)above 346 Hz.In addition,this paper deeply explores the sound absorbing-insulating mechanism through the correlation analysis between the sound absorption coefficient and TL curves.The experimental results verify the continuous and efficient absorption effects of the two metamaterials,as well as their insulation performance that breaks the mass law.In low-frequency engineering applications,the two designed metamaterials demonstrate great potential and value at sub-wavelength dimensions.
基金supported by the Korea Institute of Energy Technology Evaluation and Planning(KETEP)and the Ministry of Trade,Industry&Energy(MOTIE)of the Republic of Korea(No.RS-2025-02315209).
文摘There is a need for accurate prediction of heat and mass transfer in aerodynamically designed,non-Newtonian nanofluids across aerodynamically designed,high-flux biomedical micro-devices for thermal management and reactive coating processes,but existing work is not uncharacteristically remiss regarding viscoelasticity,radiative heating,viscous dissipation,and homogeneous–heterogeneous reactions within a single scheme that is calibrated.This research investigates the flow of Williamson nanofluid across a dynamically wedged surface under conditions that include viscous dissipation,thermal radiation,and homogeneous-heterogeneous reactions.The paper develops a detailed mathematical approach that utilizes boundary layers to transform partial differential equations into ordinary differential equations using similarity transformations.RK4 is the technique for gaining numerical solutions,but with the addition of ANNs,there is an improvement in prediction accuracy and computational efficiency.The study investigates the influence of wedge angle parameter,along with Weissenberg number,thermal radiation parameter and Brownian motion parameter,and Schmidt number,on velocity distribution,temperature distribution,and concentra-tion distribution.Enhanced Weissenberg numbers enhance viscoelastic responses that modify velocity patterns,but radiation parameters and thermophoresis have key impacts on thermal transfer phenomena.This research develops findings that are of enormous application in aerospace,biomedical(artificial hearts and drug delivery),and industrial cooling technology applications.New findings on non-Newtonian nanofluids under full flow systems are included in this work to enhance heat transfer methods in novel fluid-based systems.
