Structure determination plays the most crucial role in the discovery of novel functional materials,because only by knowing the intrinsic structures can we accurately and completely understand their properties and appl...Structure determination plays the most crucial role in the discovery of novel functional materials,because only by knowing the intrinsic structures can we accurately and completely understand their properties and applications.However,most new materials are obtained in polycrystalline form or even as mixtures with multiple phases when first synthesized,presenting significant challenges in their structure determination and phase elucidation.Fortunately,the developed three-dimensional electron diffraction(3DED/MicroED)has provided a promising solution to overcome these challenges.In this study,we have constructed a state-of-the-art 3DED/MicroED data acquisition equipment by integrating a hybrid-pixel detector with a script developed for Serial EM,and thus successfully developed an automated 3DED/MicroED method for the high-throughput structure determination.To demonstrate its effectiveness,a multiphase sample with complex porous structures is employed,showcasing that individual phases and their structures can be identified and determined,respectively.One remarkable finding is the identification of an impurity metal-organic framework(MOF)that is completely invisible to traditional powder X-ray diffraction in a supposedly“pure”commercial MOF sample.Additionally,our method also enables the atomic-resolution structure determination of flexible covalent organic framework materials,which are highly sensitive to electron beams.Moreover,a new microporous aluminoborate is discovered using this rapid structure determination method.These experimental results highlight the enormous potential of our 3DED/MicroED method in the field of new materials discovery,offering a powerful tool for the structure determination of polycrystalline functional materials.展开更多
The complex ceramic core used for hollow turbine blades requires a high porosity and a high fiexural strength. For a better balance between porosity and fiexural strength, ceramic materials with porous structures are ...The complex ceramic core used for hollow turbine blades requires a high porosity and a high fiexural strength. For a better balance between porosity and fiexural strength, ceramic materials with porous structures are preferred. In order to achieve the transition from disordered pore formation to ordered pore formation, Al_(2)O_(3) ceramic cores with triply periodic minimal surface(TPMS) micro lattice structures with different structural configurations(gyroid, diamond, and neovius) and different volume fractions of lattice structures(30, 40, and 50, vol.%) were designed and prepared by vat photopolymerization 3D printing. The effects of structural configuration and volume fraction of the lattice structure on the following structural shrinkage, microstructure, and flexural strength were investigated. The shrinkage relationship of the three lattice configurations is: neovius>diamond>gyroid. Besides, it is found that with an increase in the volume fraction of the 3D printed Al_(2)O_(3) ceramic micro lattice structures, their fiexural strength correspondingly increases ranging from 54.95 MPa to 139.1 MPa. The maximum average fiexural strength of the 3D printed Al_(2)O_(3) ceramic micro lattice structures is obtained when the structural configuration is diamond and with a volume fraction of 50vol.%, which is 139.1 MPa. Even when the volume fraction of the lattice structure is 30vol.%, that is to say the porosity is 70%, the fiexural strength is as high as 50-70 MPa, which can still be maintained at a high level. In addition, when the volume fraction of the lattice structure is a certain value, the sample with diamond configuration has a higher strength. The internal pore morphology, pore size, and porosity of the cores are precisely controlled, achieving both a high porosity and a high strength. Therefore, this study maintains high porosity and high strength simultaneously, providing a new lattice structure design idea for 3D printed ceramic cores.展开更多
Increasing the texture complexity of high-performance surfaces can enhance their antifriction properties by altering their distribution and retention of lubricating oils.When a fluid flows through a fish-scale texture...Increasing the texture complexity of high-performance surfaces can enhance their antifriction properties by altering their distribution and retention of lubricating oils.When a fluid flows through a fish-scale texture,a lubricating layer is formed,effectively reducing friction.In this study,a bionic fish-scale structure is proposed,and ceramic components are fabricated and analyzed using micro/nano additive-manufacturing technology.First,the effects of various parameters on the antifriction performance of the fish-scale texture under hydrodynamic lubrication conditions are investigated.Then,the pressure distribution of the oil film—including both positive and negative pressures—is simulated by adjusting parameters such as the angleα,ratio of textured area to total surface area,and depth of the fish-scale texture.The results indicate that for a textured area that accounts for 20%of the total surface,texture depth of 150μm,and angleαof 30°,the pressure differential reaches its maximum.Finally,based on the optimized parameters,the designed fish-scale structure is fabricated using micro/nano ceramic three-dimensional-printing technology.Friction and wear tests are conducted on the sintered samples.The experimental results align well with the simulation data,indicating that the structure can reduce the friction coefficient by approximately 15%,thereby significantly improving the antifriction performance.This study provides a valuable reference for the surface engineering of other high-performance functional structures.展开更多
A micro mechanical model is carried out to predict micro stresses and macro elastic properties of 3-D woven composites. A unit cell is composed of two phases. One is fiber yarn and the other is resin or fiber yarn in ...A micro mechanical model is carried out to predict micro stresses and macro elastic properties of 3-D woven composites. A unit cell is composed of two phases. One is fiber yarn and the other is resin or fiber yarn in transverse. The additional shearing introduced by bending of fiber yarn is considered. The method to determine the microstructure is also discussed. This model is applied to the analysis of a 3-D woven graphite/epoxy composite. Micro stresses of the cell are studied, and then macro modulus is obtained by employing the average method. The predictions agree well with experimental results.展开更多
Topology optimization is an effective method to obtain a lightweight structure that meets the requirements of structural strength.Whether the optimization results meet the actual needs mainly depends on the accuracy o...Topology optimization is an effective method to obtain a lightweight structure that meets the requirements of structural strength.Whether the optimization results meet the actual needs mainly depends on the accuracy of the material properties and the boundary conditions,especially for a tiny Flapping-wing Micro Aerial Vehicle(FMAV)transmission system manufactured by 3D printing.In this paper,experimental and numerical computation efforts were undertaken to gain a reliable topology optimization method for the bottom of the transmission system.First,the constitutive behavior of the ultraviolet(UV)curable resin used in fabrication was evaluated.Second,a numerical computation model describing further verified via experiments.Topology optimization modeling considering nonlinear factors,e.g.contact,friction and collision,was presented,and the optimization results were verified by both dynamic simulation and experiments.Finally,detailed discussions on different load cases and constraints were presented to clarify their effect on the optimization.Our methods and results presented in this paper may shed light on the lightweight design of a FMAV.展开更多
A combined beam model representing the periodicity of the microstructure and micro deformation of 3D woven composites is developed for predicting mechanical properties. The model considers the effects of off axial ten...A combined beam model representing the periodicity of the microstructure and micro deformation of 3D woven composites is developed for predicting mechanical properties. The model considers the effects of off axial tension/compression and bending/shearing couplings as well as the mutual reactions of fiber yarns. The method determining microstructure by using woven parameters is described for a typical 3D woven composite material. An analytical cell, constructed by a minimum periodic section of yarn and interlayer matrix, is adopted. Micro stresses in the cell under in-plane tensile loading are obtained by using the proposed beam model and macro modulus is then obtained by the averaging method. Material tests and a 2D micro FEM analysis are made to evaluate this model. Analyses reveal that micro stress caused by tensile/bending coupling effect is not negligible in the stress analysis.展开更多
Servo scanning 3D micro electrical discharge machining (3D SSMEDM) is a novel and effective method in fabricating complex 3D micro structures with high aspect ratio on conducting materials. In 3D SSMEDM process, the a...Servo scanning 3D micro electrical discharge machining (3D SSMEDM) is a novel and effective method in fabricating complex 3D micro structures with high aspect ratio on conducting materials. In 3D SSMEDM process, the axial wear of tool electrode can be compensated automatically by servo-keeping discharge gap, instead of the traditional methods that depend on experiential models or intermittent compensation. However, the effects of process parameters on 3D SSMEDM have not been reported up until now. In this study, the emphasis is laid on the effects of pulse duration, peak current, machining polarity, track style, track overlap, and scanning velocity on the 3D SSMEDM performances of machining efficiency, processing status, and surface accuracy. A series of experiments were carried out by machining a micro-rectangle cavity (900 μm×600 μm) on doped silicon. The experimental results were obtained as follows. Peak current plays a main role in machining efficiency and surface accuracy. Pulse duration affects obviously the stability of discharge state. The material removal rate of cathode processing is about 3/5 of that of anode processing. Compared with direction-parallel path, contour-parallel path is better in counteracting the lateral wear of tool electrode end. Scanning velocity should be selected moderately to avoid electric arc and short. Track overlap should be slightly less than the radius of tool electrode. In addition, a typical 3D micro structure of eye shape was machined based on the optimized process parameters. These results are beneficial to improve machining stability, accuracy, and efficiency in 3D SSMEDM.展开更多
The rapid advancement in the miniaturization,integration,and intelligence of electronic devices has escalated the demand for customizable microsupercapacitors(MSCs)with high energy density.However,efficient microfabri...The rapid advancement in the miniaturization,integration,and intelligence of electronic devices has escalated the demand for customizable microsupercapacitors(MSCs)with high energy density.However,efficient microfabrication of safe and high‐energy MXene MSCs for integrating microelectronics remains a significant challenge due to the low voltage window in aqueous electrolytes(typically≤0.6 V)and limited areal mass loading of MXene microelectrodes.Here,we tackle these challenges by developing a highconcentration(18mol kg^(−1))“water‐in‐LiBr”(WiB)gel electrolyte for MXene symmetric MSCs(M‐SMSCs),demonstrating a record high voltage window of 1.8 V.Subsequently,additive‐free aqueous MXene ink with excellent rheological behavior is developed for three‐dimensional(3D)printing customizable all‐MXene microelectrodes on various substrates.Leveraging the synergy of a highvoltage WiB gel electrolyte and 3D‐printed microelectrodes,quasi‐solid‐state MSMSCs operating stably at 1.8 V are constructed,and achieve an ultrahigh areal energy density of 1772μWhcm^(−2) and excellent low‐temperature tolerance,with a long‐term operation at−40℃.Finally,by extending the 3D printing protocol,M‐SMSCs are integrated with humidity sensors on a single planar substrate,demonstrating their reliability in miniaturized integrated microsystems.展开更多
The radial ultrasonic rolling electrochemical micromachining(RUR-EMM)combined rolling electrochemical micromachining(R-EMM)and ultrasonic vibration was studied in this paper.The fundamental understanding of the machin...The radial ultrasonic rolling electrochemical micromachining(RUR-EMM)combined rolling electrochemical micromachining(R-EMM)and ultrasonic vibration was studied in this paper.The fundamental understanding of the machining process especially the interaction between multiphysics in the interelectrode gap(IEG)was investigated and discussed by the finite element method.The multiphysics coupling model including flow field model,Joule heating model,material dissolution model and vibration model was built.3D multiphysics simulation based on micro dimples process in RUR-EMM and R-EMM was proposed.Simulation results showed that the electrolyte flowed into and out IEG periodically,gas bubbles were easy to squeeze out and the gas void fraction deceased about 16%to 54%,the maximum current density increased by 1.36 times in RUR-EMM than in R-EMM in one vibration period of time.And application of the ultrasonic vibration increased the electrolyte temperature about 1.3–4.4%in IEG.Verification experiments of the micro dimple process denoted better corrosion consistency of array dimples in RUR-EMM,there was no island at the micro dimple bottom which always formed in R-EMM,and an aggregated deviation of less than 8.7%for the micro dimple depth and 4%for the material removal amount between theory and experiment was obtained.展开更多
To investigate the characteristics of vaporized RP-3 kerosene combustion in a scramjet combustor enhanced by the micro vortex generator(MVG),a series of experiments are carried out based on the advanced combustion dia...To investigate the characteristics of vaporized RP-3 kerosene combustion in a scramjet combustor enhanced by the micro vortex generator(MVG),a series of experiments are carried out based on the advanced combustion diagnosis technique.The high-enthalpy incoming flow is accelerated to supersonic through a Mach 2.52 nozzle,the total pressure and temperature of which are 1.6 MPa and 1486 K,respectively.The effect of MVG on the ignition process,flame distribution,and combustor pressure along the bottom wall is well revealed,and the effects of the position and number of MVGs on stable combustion performance are analyzed.The results indicate that the development processes of the initial flame kernel with and without an MVG during ignition process show a similar behavior.The installation of an MVG can lift the shear layer,promote the penetration of flame deeper into the mainstream,and expand the area of the reactive region.Reducing the distance between the MVG and the injection position and increasing the number of MVGs are regarded as effective ways of improving the mixing degree of fuel and air with a resultant intensification of chemical reactions and flame luminescence.The effect of mixing and subsequent combustion is enhanced by shortening the distance between the MVG and the injection position.As the layout schemes of the MVG vary,the pressure distribution between the injection position and the leading edge of the cavity changes considerably,while that in the cavity remains almost constant.Increasing the number of MVGs is also beneficial for improving the premixed degree of fuel and incoming flow and results in more violent chemical reactions downstream of the cavity.展开更多
In this study,hierarchical Ag/La2 O2 CO3 micro/nanostructures(MNSs)were synthesized by in situ loading Ag nanoparticles(NPs)on the surface of the La2 O2 CO3 MNSs.The prepared La2 O2 CO3 MNSs present flower-like shape ...In this study,hierarchical Ag/La2 O2 CO3 micro/nanostructures(MNSs)were synthesized by in situ loading Ag nanoparticles(NPs)on the surface of the La2 O2 CO3 MNSs.The prepared La2 O2 CO3 MNSs present flower-like shape and can be tuned by the molar ratio of La(NO3)3 and CO(NH2)2.In the molar ratio of 1:2 to 1:55,the La2 O2 CO3 MNSs mainly consist of polyhedral rods,irregular rods and irregular spindles and their size is about 10,8 and 7μm,respectively.After loading Ag NPs,the spindle-like Ag/La2 O2 CO3 MNSs were used for phosphate removal and antibacterial activity.At the initial phosphate concentration of20 mg/L,the removal rate is 59.6%.The Ag/La2 O2 CO3 MNSs have significant antibacterial activity and their MIC values for S.aureus and E.coli are 31.3 and 15.6μg/mL,respectively.The results indicate that Ag/La2 O2 CO3 MNSs may have good application prospects in open water to inhibit bacterial growth.展开更多
Titanium(Ti)and its alloys have been extensively explored for treating load-bearing bone defects.How-ever,high-stress shielding,weak osteogenic activity,and insufficient vascularization remain key chal-lenges for the ...Titanium(Ti)and its alloys have been extensively explored for treating load-bearing bone defects.How-ever,high-stress shielding,weak osteogenic activity,and insufficient vascularization remain key chal-lenges for the long-term clinical outcomes of Ti-based implants.Herein,inspired by structural and func-tional cues of bone regeneration,a silicon-doped nano-hydroxyapatite(nSiHA)/titanium dioxide(TiO_(2))composite coating with a hierarchical micro/nano-network structure is constructed on the surface of a 3D-printed porous Ti scaffold via a combined strategy of acid-alkali(AA)treatment and electrochemi-cal deposition technique,which not only endows the scaffold with excellent osteoinduction ability but can also effectively immobilize and release vascular endothelial growth factor(VEGF).The results of the in vitro cell experiments show that the functionalized Ti scaffold significantly promotes osteogenesis in bone marrow mesenchymal stem cells(BMSCs)and angiogenesis in human umbilical vein endothelial cells(HUVECs)by activating the extracellular signal-regulated protein kinase(ERK)and HIF-1αsignaling pathways.After being implanted into a rat femoral condyle defect model,the functionalized Ti scaffold can induce in situ vascularized bone regeneration by orchestrating the two coupled processes of angio-genesis and osteogenesis.These findings indicate that the functionalized Ti scaffold has great potential in bone tissue regeneration and is a promising candidate for load-bearing bone defect repair.展开更多
The advent of three-dimensional （3-D） printed technique provides great possibility in the fabrication of customized porous titanium （Ti） implant. However, the bioinert property of the printed Ti poses an out- stan...The advent of three-dimensional （3-D） printed technique provides great possibility in the fabrication of customized porous titanium （Ti） implant. However, the bioinert property of the printed Ti poses an out- standing problem. Hybrid micro-arc oxidation and hydrothermal （MAO-HT） treatment on porous metals is able to produce multi-scaled hierarchical orthopedic implant, showing great potential for surface mod- ification of 3-D printed implant. In this study, cylindrical porous Ti6Al4V （Ti64） scaffolds with pore size of 640 lure, porosity of ？3% were 3-D printed by electron beam melting process, and their surfaces were left untreated or treated by a combined MAO-HT procedure. In vitro bioactivity was tested by immer- sion in simulated body fluid for different time points. Then, 12 scaffolds in each group were implanted into the femoral condyles of New Zealand rabbit for 8 weeks. Osseointegration was evaluated by qual- itative and quantitative histological analysis, and the bone ingrowth features were probed by sequential fluorescent labeling at 3 and 6 weeks post-surgery, Following the MAO-HT treatment, the porous Ti64 scaffold was endowed with multi-scaled micro/nano-topographies and high amounts of CaP on its surface. The treated scaffold exhibited drastically enhanced apatite forming ability compared with the un- treated one. In vivo test revealed significantly that a higher amount of bone ingrowth and bone implant contact at the treated scaffold. The 2 types of scaffolds had different patterns of bone ingrowth; the treated scaffold exhibited a pattern of contact osteogenesis, by which bone formed directly on the treated implant surface, whereas bone formed distal to the implant surface of the untreated scaffold. MAO-HT treat- ment can significantly enhance the in vitro apatite-inducing ability and in vivo osseointegration capacity of 3-D porous Ti64 scaffold and may provide as a viable approach for the fabrication of bioactive 3-D printed porous implant for orthopedic applications.展开更多
AIM: To explore the regulatory mechanism of the target gene of micro RNA-21(mi R-21), phosphatase gene(p TEN), and its downstream proteins, protein kinase B(AKT) and phosphatidylinositol 3-kinase(p I3K), in colorectal...AIM: To explore the regulatory mechanism of the target gene of micro RNA-21(mi R-21), phosphatase gene(p TEN), and its downstream proteins, protein kinase B(AKT) and phosphatidylinositol 3-kinase(p I3K), in colorectal cancer(CRC) cells. METHODS: Quantitative real-time p CR(q RT-p CR) and Western blot were used to detect the expression levels of mi R-21 and p TEN in HCT116, HT29, Colo32 and SW480 CRC cell lines. Also, the expression levels of p TEN m RNA and its downstream proteins AKT and p I3 K in HCT116 cells after downregulating mi R-21 were investigated. RESULTS: Comparing the mi R-21 expression in CRC cells, the expression levels of mi R-21 were highest in HCT116 cells, and the expression levels of mi R-21 were lowest in SW480 cells. In comparing mi R-21 and p TEN expression in CRC cells, we found that the protein expression levels of mi R-21 and p TEN were inversely correlated(p < 0.05); when mi R-21 expression was reduced, m RNA expression levels of p TEN did not significantly change(p > 0.05), but the expression levels of its protein significantly increased(p < 0.05). In comparing the levels of p TEN protein and downstream AKT and p I3 K in HCT116 cells after downregulation of mi R-21 expression, the levels of AKT and p I3 K protein expression significantly decreased(p < 0.05). CONCLUSION: p TEN is one of the direct target genesof mi R-21. Thus, phosphatase gene and its downstream AKT and p I3 K expression levels can be regulated by regulating the expression levels of mi R-21, which in turn regulates the development of CRC.展开更多
The radiation shielding characteristics of 50wt% WO3/E44 epoxy composite in various gamma energies from 80 keV to 1.33 MeV are investigated via the MCNP code. Thus two scales are considered for WOa filler particles： ...The radiation shielding characteristics of 50wt% WO3/E44 epoxy composite in various gamma energies from 80 keV to 1.33 MeV are investigated via the MCNP code. Thus two scales are considered for WOa filler particles： micro and nano with sizes of i #m and 5Onto, respectively. The simulation results show that W03 nano particles exhibit a larger increase in linear attenuation coefficient in comparison with micro size particles. Finally, validation of simulation results with the published experimental data shows a good agreement.展开更多
基金supported by the National Natural Science Foundation of China(22371121)the Natural Science Foundation of Jiangsu Province(BK20230772)the Fundamental Research Funds for Central Universities of China(020514380306)。
文摘Structure determination plays the most crucial role in the discovery of novel functional materials,because only by knowing the intrinsic structures can we accurately and completely understand their properties and applications.However,most new materials are obtained in polycrystalline form or even as mixtures with multiple phases when first synthesized,presenting significant challenges in their structure determination and phase elucidation.Fortunately,the developed three-dimensional electron diffraction(3DED/MicroED)has provided a promising solution to overcome these challenges.In this study,we have constructed a state-of-the-art 3DED/MicroED data acquisition equipment by integrating a hybrid-pixel detector with a script developed for Serial EM,and thus successfully developed an automated 3DED/MicroED method for the high-throughput structure determination.To demonstrate its effectiveness,a multiphase sample with complex porous structures is employed,showcasing that individual phases and their structures can be identified and determined,respectively.One remarkable finding is the identification of an impurity metal-organic framework(MOF)that is completely invisible to traditional powder X-ray diffraction in a supposedly“pure”commercial MOF sample.Additionally,our method also enables the atomic-resolution structure determination of flexible covalent organic framework materials,which are highly sensitive to electron beams.Moreover,a new microporous aluminoborate is discovered using this rapid structure determination method.These experimental results highlight the enormous potential of our 3DED/MicroED method in the field of new materials discovery,offering a powerful tool for the structure determination of polycrystalline functional materials.
基金supported by the National Natural Science Foundation of China (Grant No. 52275310)。
文摘The complex ceramic core used for hollow turbine blades requires a high porosity and a high fiexural strength. For a better balance between porosity and fiexural strength, ceramic materials with porous structures are preferred. In order to achieve the transition from disordered pore formation to ordered pore formation, Al_(2)O_(3) ceramic cores with triply periodic minimal surface(TPMS) micro lattice structures with different structural configurations(gyroid, diamond, and neovius) and different volume fractions of lattice structures(30, 40, and 50, vol.%) were designed and prepared by vat photopolymerization 3D printing. The effects of structural configuration and volume fraction of the lattice structure on the following structural shrinkage, microstructure, and flexural strength were investigated. The shrinkage relationship of the three lattice configurations is: neovius>diamond>gyroid. Besides, it is found that with an increase in the volume fraction of the 3D printed Al_(2)O_(3) ceramic micro lattice structures, their fiexural strength correspondingly increases ranging from 54.95 MPa to 139.1 MPa. The maximum average fiexural strength of the 3D printed Al_(2)O_(3) ceramic micro lattice structures is obtained when the structural configuration is diamond and with a volume fraction of 50vol.%, which is 139.1 MPa. Even when the volume fraction of the lattice structure is 30vol.%, that is to say the porosity is 70%, the fiexural strength is as high as 50-70 MPa, which can still be maintained at a high level. In addition, when the volume fraction of the lattice structure is a certain value, the sample with diamond configuration has a higher strength. The internal pore morphology, pore size, and porosity of the cores are precisely controlled, achieving both a high porosity and a high strength. Therefore, this study maintains high porosity and high strength simultaneously, providing a new lattice structure design idea for 3D printed ceramic cores.
基金supported by Shanghai Collaborative Innovation Project(Grant No.XTCX-KJ-2024-01)the National Natural Science Foundation of China(Grant No.52205493).
文摘Increasing the texture complexity of high-performance surfaces can enhance their antifriction properties by altering their distribution and retention of lubricating oils.When a fluid flows through a fish-scale texture,a lubricating layer is formed,effectively reducing friction.In this study,a bionic fish-scale structure is proposed,and ceramic components are fabricated and analyzed using micro/nano additive-manufacturing technology.First,the effects of various parameters on the antifriction performance of the fish-scale texture under hydrodynamic lubrication conditions are investigated.Then,the pressure distribution of the oil film—including both positive and negative pressures—is simulated by adjusting parameters such as the angleα,ratio of textured area to total surface area,and depth of the fish-scale texture.The results indicate that for a textured area that accounts for 20%of the total surface,texture depth of 150μm,and angleαof 30°,the pressure differential reaches its maximum.Finally,based on the optimized parameters,the designed fish-scale structure is fabricated using micro/nano ceramic three-dimensional-printing technology.Friction and wear tests are conducted on the sintered samples.The experimental results align well with the simulation data,indicating that the structure can reduce the friction coefficient by approximately 15%,thereby significantly improving the antifriction performance.This study provides a valuable reference for the surface engineering of other high-performance functional structures.
文摘A micro mechanical model is carried out to predict micro stresses and macro elastic properties of 3-D woven composites. A unit cell is composed of two phases. One is fiber yarn and the other is resin or fiber yarn in transverse. The additional shearing introduced by bending of fiber yarn is considered. The method to determine the microstructure is also discussed. This model is applied to the analysis of a 3-D woven graphite/epoxy composite. Micro stresses of the cell are studied, and then macro modulus is obtained by employing the average method. The predictions agree well with experimental results.
基金supported by the National Natural Science Foundation of China(No.11672022)。
文摘Topology optimization is an effective method to obtain a lightweight structure that meets the requirements of structural strength.Whether the optimization results meet the actual needs mainly depends on the accuracy of the material properties and the boundary conditions,especially for a tiny Flapping-wing Micro Aerial Vehicle(FMAV)transmission system manufactured by 3D printing.In this paper,experimental and numerical computation efforts were undertaken to gain a reliable topology optimization method for the bottom of the transmission system.First,the constitutive behavior of the ultraviolet(UV)curable resin used in fabrication was evaluated.Second,a numerical computation model describing further verified via experiments.Topology optimization modeling considering nonlinear factors,e.g.contact,friction and collision,was presented,and the optimization results were verified by both dynamic simulation and experiments.Finally,detailed discussions on different load cases and constraints were presented to clarify their effect on the optimization.Our methods and results presented in this paper may shed light on the lightweight design of a FMAV.
文摘A combined beam model representing the periodicity of the microstructure and micro deformation of 3D woven composites is developed for predicting mechanical properties. The model considers the effects of off axial tension/compression and bending/shearing couplings as well as the mutual reactions of fiber yarns. The method determining microstructure by using woven parameters is described for a typical 3D woven composite material. An analytical cell, constructed by a minimum periodic section of yarn and interlayer matrix, is adopted. Micro stresses in the cell under in-plane tensile loading are obtained by using the proposed beam model and macro modulus is then obtained by the averaging method. Material tests and a 2D micro FEM analysis are made to evaluate this model. Analyses reveal that micro stress caused by tensile/bending coupling effect is not negligible in the stress analysis.
基金supported by National Natural Science Foundation of China (Grant No. 50905094)National Hi-tech Research and Development Program of China (863 Program, Grant No. 2009AA044204, Grant No. 2009AA044205)China Postdoctoral Science Foundation (Grant No. 20080440378, Grant No. 200902097)
文摘Servo scanning 3D micro electrical discharge machining (3D SSMEDM) is a novel and effective method in fabricating complex 3D micro structures with high aspect ratio on conducting materials. In 3D SSMEDM process, the axial wear of tool electrode can be compensated automatically by servo-keeping discharge gap, instead of the traditional methods that depend on experiential models or intermittent compensation. However, the effects of process parameters on 3D SSMEDM have not been reported up until now. In this study, the emphasis is laid on the effects of pulse duration, peak current, machining polarity, track style, track overlap, and scanning velocity on the 3D SSMEDM performances of machining efficiency, processing status, and surface accuracy. A series of experiments were carried out by machining a micro-rectangle cavity (900 μm×600 μm) on doped silicon. The experimental results were obtained as follows. Peak current plays a main role in machining efficiency and surface accuracy. Pulse duration affects obviously the stability of discharge state. The material removal rate of cathode processing is about 3/5 of that of anode processing. Compared with direction-parallel path, contour-parallel path is better in counteracting the lateral wear of tool electrode end. Scanning velocity should be selected moderately to avoid electric arc and short. Track overlap should be slightly less than the radius of tool electrode. In addition, a typical 3D micro structure of eye shape was machined based on the optimized process parameters. These results are beneficial to improve machining stability, accuracy, and efficiency in 3D SSMEDM.
基金National Natural Science Foundation of China,Grant/Award Numbers:22005297,22125903,51872283,22209175,22209176National Key Research and Development Program of China,Grant/Award Number:2022YFA1504100+8 种基金Support Program for Excellent Young Talents in Universities of Anhui Province,Grant/Award Number:2022AH030134Anhui Province Higher Education Innovation Team:Key Technologies and Equipment Innovation Team for Clean Energy,Grant/Award Number:2023AH010055Strategic Priority Research Program of the Chinese Academy of Sciences,Grant/Award Number:XDB36030200Dalian Innovation Support Plan for High Level Talents,Grant/Award Number:2019RT09Dalian National Laboratory for Clean Energy(DNL),CAS,DNL Cooperation Fund,CAS,Grant/Award Numbers:DNL202016,DNL202019,DNL202003DICP,Grant/Award Number:DICP I2020032Doctor Research Startup Foundation of Suzhou University,Grant/Award Number:2023BSK015China Postdoctoral Science Foundation,Grant/Award Numbers:2020M680995,2021M693127International Postdoctoral Exchange Fellowship Program,Grant/Award Number:YJ20210311。
文摘The rapid advancement in the miniaturization,integration,and intelligence of electronic devices has escalated the demand for customizable microsupercapacitors(MSCs)with high energy density.However,efficient microfabrication of safe and high‐energy MXene MSCs for integrating microelectronics remains a significant challenge due to the low voltage window in aqueous electrolytes(typically≤0.6 V)and limited areal mass loading of MXene microelectrodes.Here,we tackle these challenges by developing a highconcentration(18mol kg^(−1))“water‐in‐LiBr”(WiB)gel electrolyte for MXene symmetric MSCs(M‐SMSCs),demonstrating a record high voltage window of 1.8 V.Subsequently,additive‐free aqueous MXene ink with excellent rheological behavior is developed for three‐dimensional(3D)printing customizable all‐MXene microelectrodes on various substrates.Leveraging the synergy of a highvoltage WiB gel electrolyte and 3D‐printed microelectrodes,quasi‐solid‐state MSMSCs operating stably at 1.8 V are constructed,and achieve an ultrahigh areal energy density of 1772μWhcm^(−2) and excellent low‐temperature tolerance,with a long‐term operation at−40℃.Finally,by extending the 3D printing protocol,M‐SMSCs are integrated with humidity sensors on a single planar substrate,demonstrating their reliability in miniaturized integrated microsystems.
基金financial support of the projects from the National Natural Science Foundation of China(Nos.51975532 and 51475428)the Zhejiang Provincial Natural Science Foundation(No.LY19E050007)。
文摘The radial ultrasonic rolling electrochemical micromachining(RUR-EMM)combined rolling electrochemical micromachining(R-EMM)and ultrasonic vibration was studied in this paper.The fundamental understanding of the machining process especially the interaction between multiphysics in the interelectrode gap(IEG)was investigated and discussed by the finite element method.The multiphysics coupling model including flow field model,Joule heating model,material dissolution model and vibration model was built.3D multiphysics simulation based on micro dimples process in RUR-EMM and R-EMM was proposed.Simulation results showed that the electrolyte flowed into and out IEG periodically,gas bubbles were easy to squeeze out and the gas void fraction deceased about 16%to 54%,the maximum current density increased by 1.36 times in RUR-EMM than in R-EMM in one vibration period of time.And application of the ultrasonic vibration increased the electrolyte temperature about 1.3–4.4%in IEG.Verification experiments of the micro dimple process denoted better corrosion consistency of array dimples in RUR-EMM,there was no island at the micro dimple bottom which always formed in R-EMM,and an aggregated deviation of less than 8.7%for the micro dimple depth and 4%for the material removal amount between theory and experiment was obtained.
基金supported by the National Natural Science Foundation of China(No.12002373)。
文摘To investigate the characteristics of vaporized RP-3 kerosene combustion in a scramjet combustor enhanced by the micro vortex generator(MVG),a series of experiments are carried out based on the advanced combustion diagnosis technique.The high-enthalpy incoming flow is accelerated to supersonic through a Mach 2.52 nozzle,the total pressure and temperature of which are 1.6 MPa and 1486 K,respectively.The effect of MVG on the ignition process,flame distribution,and combustor pressure along the bottom wall is well revealed,and the effects of the position and number of MVGs on stable combustion performance are analyzed.The results indicate that the development processes of the initial flame kernel with and without an MVG during ignition process show a similar behavior.The installation of an MVG can lift the shear layer,promote the penetration of flame deeper into the mainstream,and expand the area of the reactive region.Reducing the distance between the MVG and the injection position and increasing the number of MVGs are regarded as effective ways of improving the mixing degree of fuel and air with a resultant intensification of chemical reactions and flame luminescence.The effect of mixing and subsequent combustion is enhanced by shortening the distance between the MVG and the injection position.As the layout schemes of the MVG vary,the pressure distribution between the injection position and the leading edge of the cavity changes considerably,while that in the cavity remains almost constant.Increasing the number of MVGs is also beneficial for improving the premixed degree of fuel and incoming flow and results in more violent chemical reactions downstream of the cavity.
基金Project supported by the National Natural Science Foundation of China(21271062)。
文摘In this study,hierarchical Ag/La2 O2 CO3 micro/nanostructures(MNSs)were synthesized by in situ loading Ag nanoparticles(NPs)on the surface of the La2 O2 CO3 MNSs.The prepared La2 O2 CO3 MNSs present flower-like shape and can be tuned by the molar ratio of La(NO3)3 and CO(NH2)2.In the molar ratio of 1:2 to 1:55,the La2 O2 CO3 MNSs mainly consist of polyhedral rods,irregular rods and irregular spindles and their size is about 10,8 and 7μm,respectively.After loading Ag NPs,the spindle-like Ag/La2 O2 CO3 MNSs were used for phosphate removal and antibacterial activity.At the initial phosphate concentration of20 mg/L,the removal rate is 59.6%.The Ag/La2 O2 CO3 MNSs have significant antibacterial activity and their MIC values for S.aureus and E.coli are 31.3 and 15.6μg/mL,respectively.The results indicate that Ag/La2 O2 CO3 MNSs may have good application prospects in open water to inhibit bacterial growth.
基金supported by the Sichuan Science and Technology Program (Nos.2019JDTD0008 and 2022YFG0109)the China Postdoctoral Science Foundation (Nos.2021M692316 and 2020TQ0218).
文摘Titanium(Ti)and its alloys have been extensively explored for treating load-bearing bone defects.How-ever,high-stress shielding,weak osteogenic activity,and insufficient vascularization remain key chal-lenges for the long-term clinical outcomes of Ti-based implants.Herein,inspired by structural and func-tional cues of bone regeneration,a silicon-doped nano-hydroxyapatite(nSiHA)/titanium dioxide(TiO_(2))composite coating with a hierarchical micro/nano-network structure is constructed on the surface of a 3D-printed porous Ti scaffold via a combined strategy of acid-alkali(AA)treatment and electrochemi-cal deposition technique,which not only endows the scaffold with excellent osteoinduction ability but can also effectively immobilize and release vascular endothelial growth factor(VEGF).The results of the in vitro cell experiments show that the functionalized Ti scaffold significantly promotes osteogenesis in bone marrow mesenchymal stem cells(BMSCs)and angiogenesis in human umbilical vein endothelial cells(HUVECs)by activating the extracellular signal-regulated protein kinase(ERK)and HIF-1αsignaling pathways.After being implanted into a rat femoral condyle defect model,the functionalized Ti scaffold can induce in situ vascularized bone regeneration by orchestrating the two coupled processes of angio-genesis and osteogenesis.These findings indicate that the functionalized Ti scaffold has great potential in bone tissue regeneration and is a promising candidate for load-bearing bone defect repair.
基金the Beijing AKEC Medical Co.,LtdMedical Research Center of Peking University Third Hospitalsupported by the Project of Scientific and Technical Plan of Beijing(Nos.Z121100005312005 and Z141100002814008)
文摘The advent of three-dimensional （3-D） printed technique provides great possibility in the fabrication of customized porous titanium （Ti） implant. However, the bioinert property of the printed Ti poses an out- standing problem. Hybrid micro-arc oxidation and hydrothermal （MAO-HT） treatment on porous metals is able to produce multi-scaled hierarchical orthopedic implant, showing great potential for surface mod- ification of 3-D printed implant. In this study, cylindrical porous Ti6Al4V （Ti64） scaffolds with pore size of 640 lure, porosity of ？3% were 3-D printed by electron beam melting process, and their surfaces were left untreated or treated by a combined MAO-HT procedure. In vitro bioactivity was tested by immer- sion in simulated body fluid for different time points. Then, 12 scaffolds in each group were implanted into the femoral condyles of New Zealand rabbit for 8 weeks. Osseointegration was evaluated by qual- itative and quantitative histological analysis, and the bone ingrowth features were probed by sequential fluorescent labeling at 3 and 6 weeks post-surgery, Following the MAO-HT treatment, the porous Ti64 scaffold was endowed with multi-scaled micro/nano-topographies and high amounts of CaP on its surface. The treated scaffold exhibited drastically enhanced apatite forming ability compared with the un- treated one. In vivo test revealed significantly that a higher amount of bone ingrowth and bone implant contact at the treated scaffold. The 2 types of scaffolds had different patterns of bone ingrowth; the treated scaffold exhibited a pattern of contact osteogenesis, by which bone formed directly on the treated implant surface, whereas bone formed distal to the implant surface of the untreated scaffold. MAO-HT treat- ment can significantly enhance the in vitro apatite-inducing ability and in vivo osseointegration capacity of 3-D porous Ti64 scaffold and may provide as a viable approach for the fabrication of bioactive 3-D printed porous implant for orthopedic applications.
文摘AIM: To explore the regulatory mechanism of the target gene of micro RNA-21(mi R-21), phosphatase gene(p TEN), and its downstream proteins, protein kinase B(AKT) and phosphatidylinositol 3-kinase(p I3K), in colorectal cancer(CRC) cells. METHODS: Quantitative real-time p CR(q RT-p CR) and Western blot were used to detect the expression levels of mi R-21 and p TEN in HCT116, HT29, Colo32 and SW480 CRC cell lines. Also, the expression levels of p TEN m RNA and its downstream proteins AKT and p I3 K in HCT116 cells after downregulating mi R-21 were investigated. RESULTS: Comparing the mi R-21 expression in CRC cells, the expression levels of mi R-21 were highest in HCT116 cells, and the expression levels of mi R-21 were lowest in SW480 cells. In comparing mi R-21 and p TEN expression in CRC cells, we found that the protein expression levels of mi R-21 and p TEN were inversely correlated(p < 0.05); when mi R-21 expression was reduced, m RNA expression levels of p TEN did not significantly change(p > 0.05), but the expression levels of its protein significantly increased(p < 0.05). In comparing the levels of p TEN protein and downstream AKT and p I3 K in HCT116 cells after downregulation of mi R-21 expression, the levels of AKT and p I3 K protein expression significantly decreased(p < 0.05). CONCLUSION: p TEN is one of the direct target genesof mi R-21. Thus, phosphatase gene and its downstream AKT and p I3 K expression levels can be regulated by regulating the expression levels of mi R-21, which in turn regulates the development of CRC.
文摘The radiation shielding characteristics of 50wt% WO3/E44 epoxy composite in various gamma energies from 80 keV to 1.33 MeV are investigated via the MCNP code. Thus two scales are considered for WOa filler particles： micro and nano with sizes of i #m and 5Onto, respectively. The simulation results show that W03 nano particles exhibit a larger increase in linear attenuation coefficient in comparison with micro size particles. Finally, validation of simulation results with the published experimental data shows a good agreement.
