The construction of the New Medical Sciences aims to cultivate interdisciplinary medical talents,placing higher demands on physiology experiment teaching.In light of the challenges of traditional teaching,such as outd...The construction of the New Medical Sciences aims to cultivate interdisciplinary medical talents,placing higher demands on physiology experiment teaching.In light of the challenges of traditional teaching,such as outdated content,a single assessment mechanism,low student engagement,and limited research experience among instructors,this study proposes a reform pathway centered on research competence development,supported by diversified evaluation methods and the deep integration of ideological and scenario-based teaching.By optimizing teaching content,introducing innovative projects,establishing a multidimensional assessment system,and strengthening faculty development,the proposed reforms effectively enhance students’Innovative ability and practical skills.This study provides theoretical insights and practical experience for training interdisciplinary medical professionals to meet the demands of the new era.展开更多
In recent years,photocatalytic technologies have been extensively studied and diffusely used in water splitting,decomposition of organic pollutants,reduction of carbon dioxide,etc.As a type of eye-catching semiconduct...In recent years,photocatalytic technologies have been extensively studied and diffusely used in water splitting,decomposition of organic pollutants,reduction of carbon dioxide,etc.As a type of eye-catching semiconductors,BiVO_(4),Bi_(2)WO_(6),and Bi_(2)MoO_(6) (denoted as BiaAOb)have become a hotspot in photocatalytic researches due to their crystal structure stability,high light quantum and electronic transmission efficiency,and outstanding energy utilization capacity.However,pristine BiaAOb(A=V,W,and Mo)possesses several drawbacks,such as low separation efficiency of photo-excited electron-hole pairs,low specific surface area,as well as the poor quantum utilization,which restrict their photocatalytic performance.Considerable efforts,such as nanostructure modification,surface engineering,and heterojunction/homojunction fabrication,have been conducted to solve these problems.This integrated review aims to sum up recent advances in current studies on fabrication of high efficiency BiaAOb photocatalysts to accelerate the developments of BiaAOb-based materials in the photocatalysis(PC)field.The current challenges and prospects of BiaAOb are emphasized which stretches the existing fundamental theories of PC as well as provide a promising strategy to fabricate high efficiency BiaAOb catalysts to control environmental pollution and assist the sustainable development of energy.展开更多
Fretting wear has an adverse impact on the fatigue life of turbine blade roots.The current work is to comparatively investigate the fretting wear behaviour of the nickel-based superalloy surfaces produced by polishing...Fretting wear has an adverse impact on the fatigue life of turbine blade roots.The current work is to comparatively investigate the fretting wear behaviour of the nickel-based superalloy surfaces produced by polishing and creep-feed profile grinding,respectively,in terms of surface/subsurface fretting damage,the friction coefficient,wear volume and wear rate.Experimental results show that the granulated tribolayer aggravates the workpiece wear,while the flat compacted tribolayer enhances the wear resistance ability of workpiece,irrespective of whether the workpiece is processed by polishing or grinding.However,the wear behaviors of tribolayers are different.For the polished surface,when the normal load exceeds 100 N,the main defects are crack,rupture,delamination and peeling of workpiece materials;the wear mechanism changes from severe oxidative wear to fatigue wear and abrasive wear when the loads increase from 50 to 180 N.As for the ground surface,the main wear mechanism is abrasive wear.Particularly,the ground surface possesses better wear-resistant ability than the polished surface because the former has the lower values in coefficient friction(0.23),wear volume(0.06×10^(6)μm^(3))and wear rate(0.25×10^(-16)Pa^(-1)).Finally,an illustration is given to characterize the evolution of wear debris on such nickel-based superalloy on the ground surface.展开更多
Gamma titanium-aluminum intermetallic compounds(γ-TiAl)have gained considerable attentions in the aerospace industry due to their exceptional thermal resilience and comprehensive attributes,making them a prime exampl...Gamma titanium-aluminum intermetallic compounds(γ-TiAl)have gained considerable attentions in the aerospace industry due to their exceptional thermal resilience and comprehensive attributes,making them a prime example of lightweight and advanced materials.To address the frequent occurrence of burns and severe tool deterioration during the process of high-efficiency deep grinding(HEDG)onγ-TiAl alloys,ultrasonic vibration-assisted high-efficiency deep grinding(UVHEDG)has been emerged.Results indicate that in UVHEDG,the grinding temperature is on average 15.4%lower than HEDG due to the employment of ultrasonic vibrations,enhancing coolant penetration into the grinding area and thus reducing heat generation.Besides,UVHEDG possesses superior performance in terms of grinding forces compared to HEDG.As the material removal volume(MRV)increases,the tangential grinding force(F_(t))and normal grinding force(F_(n))of UVHEDG increase but to a lesser extent than in HEDG,with an average reduction of16.25%and 14.7%,respectively.UVHEDG primarily experiences microfracture of grains,whereas HEDG undergoes large-scale wear later in the process due to increased grinding forces.The surface roughness(R_(a))characteristics of UVHEDG are superior,with the average value of R_(a)decreasing by 46.5%compared to HEDG as MRV increases.The surface morphology in UVHEDG exhibits enhanced smoothness and a shallower layer of plastic deformation.Grinding chips generated by UVHEDG show a more shear-like shape,with the applied influence of ultrasonic vibration on chip morphology,thereby impacting material removal behaviors.These aforementioned findings contribute to enhanced machining efficiency and product quality ofγ-TiAl alloys after employing ultrasonic vibrations into HEDG.展开更多
To obtain large-volume non-thermal arc plasma(NTAP), a multiple NTAP generator with three pairs of electrodes has been developed. The arc plasma characteristics, including dynamic process, spatial distribution, and ro...To obtain large-volume non-thermal arc plasma(NTAP), a multiple NTAP generator with three pairs of electrodes has been developed. The arc plasma characteristics, including dynamic process, spatial distribution, and rotation velocity in the discharge zone, were investigated by high speed photograph and image processing methods. The results showed that the dynamic behaviors and spatial distribution of the arc plasma were strongly related to the electrode configuration.A swirl flow of multi-arc plasma was formed by adjusting the electrode configuration, and a steady luminance area was clearly observed in the center of the discharge zone. Moreover, the size of the luminance area increased by decreasing the gas flow rate. The electrical connection in series could be formed between/among these arc columns with their respective driving power supplies in the multi-arc dynamic evolution process. An approximately periodical process of acceleration and deceleration of the arc rotation velocity was observed in the multi-arc generator with swirl flow configuration. In general, the mean velocity of arc rotation was higher in the multi-arc generator with swirl flow configuration when a pair of electrodes driven by a power supply were opposite to each other rather than adjacent.展开更多
We investigate characteristics of multi-arc torches with three pairs of electrodes(three cathodes and three anodes)and their performance on the spheroidization of SiO2 powder.The effect of electrode arrangement,includ...We investigate characteristics of multi-arc torches with three pairs of electrodes(three cathodes and three anodes)and their performance on the spheroidization of SiO2 powder.The effect of electrode arrangement,including adjacent pattern(AD pattern,adjacent electrodes powered by one power supply)and opposite pattern(OP pattern,opposite electrodes powered by one power supply),on the dynamics of arc plasma is investigated based on synchronous acquisition of electrical and optical signals.The results show that both the voltage and spatial distribution of each arc of multiple arcs are more stable compared with those of a single arc.The fluctuation of an arc in multiple arcs mainly comes from the small-scale arc-to-arc restrikes among multiple arcs.Moreover,these arc-to-arc restrikes occur more frequently among multiple arc columns in OP pattern than in AD pattern.Moreover,the high-temperature area of the central region of arc chamber in OP pattern is larger than that in AP pattern.For the spheroidization of SiO2 in this multi-arc generator,the spheronization degrees of plasma treated silica in OP pattern are at least 20%higher than those in AD pattern.展开更多
The enhanced volume of thermal plasma is produced by a multi-arc thermal plasma generator with three pairs of discharge electrodes driven by three directed current power suppliers.Combined with a high-speed camera and...The enhanced volume of thermal plasma is produced by a multi-arc thermal plasma generator with three pairs of discharge electrodes driven by three directed current power suppliers.Combined with a high-speed camera and an oscilloscope,which acquire optical and electric signals synchronously,the dynamic behavior of different kinds of multi-arc discharge adjusted by the electrode arrangement is investigated.Also,the spatial distributions and instability of the arc discharge are analyzed in four electrode configurations using the gray value statistical method.It is found that the cathodic arcs mainly show a contracting state,while the anodic arcs have a trend of transition from shrinkage to a diffusion-like state with the increase of the discharge current.As a result of the adjustment of the electrode configuration,a high temperature region formed in the center of the discharge region in configurations of adjacent electrodes with opposite flow distribution and opposite electrodes with swirl flow distribution due to severe fluctuation of arcs.The discharge voltage rises with increased discharge current in this novel multi-arc plasma generator.It is also found that anode ablation mainly occurs on the conical surface at the copper electrode tip,while cathode erosion mainly occurs on the surface of the inserted tungsten and the nearby copper.展开更多
Cubic boron nitride(cBN)superabrasive grinding wheels exhibit unique advantages in the grinding of difficult-to-cut materials with high strength and toughness,such as titanium alloys and superalloys.However,grinding w...Cubic boron nitride(cBN)superabrasive grinding wheels exhibit unique advantages in the grinding of difficult-to-cut materials with high strength and toughness,such as titanium alloys and superalloys.However,grinding with multilayered metallic cBN superabrasive wheels faces problems in terms of grain wear resistance,the chip storage capability of the working layers and the stability and controllability of the dressing process.Therefore,in this work,novel metallic cBN superabrasive wheels with aggregated cBN(AcBN)grains and open pore structures were fabricated to improve machining efficiency and surface quality.Prior to the grinding trials,the airborne abrasive blasting process was conducted and the abrasive blasting parameters were optimized in view of wear properties of cBN grains and metallic matrix materials.Subsequently,the comparative experiments were performed and then the variations in grinding force and force ratio,grinding temperature,tool wear morphology and ground surface quality of the multilayered AcBN grinding wheels were investigated during machining Ti-6Al-4V alloys.In consideration of the variations of grain erosion wear volume and material removal rate per unit of pure metallic matrix materials as the abrasive blasting parameters changes,the optimal abrasive blasting parameters were identified as the SiC abrasive mesh size of 60#and the abrasive blasting distance and time of 60 mm and 15 s,respectively.The as-developed AcBN grains exhibited better fracture toughness and impact resistance than monocrystalline cBN(McBN)grains because of the existence of metal-bonded materials amongst multiple cBN particles that decreased crack propagation inside whole grains.The metallic porous AcBN wheels had lower grinding forces and temperature and better ground surface quality than vitrified McBN wheels due to the constant layer-by-layer exposure of cBN particles in the working layer of AcBN wheels.展开更多
Cubic boron nitride(cBN)grinding wheels play a pivotal role in precision machining,serving as indispensable tools for achieving exceptional surface quality.Ensuring the sharpness of cBN grains and optimizing the grind...Cubic boron nitride(cBN)grinding wheels play a pivotal role in precision machining,serving as indispensable tools for achieving exceptional surface quality.Ensuring the sharpness of cBN grains and optimizing the grinding wheel’s chip storage capacity are critical factors.This paper presents a study on the metal-bonded segments and single cBN grain samples using the vacuum sintering method.It investigates the impact of blasting parameters-specifically silicon carbide(SiC)abrasive size,blasting distance,and blasting time-on the erosive wear characteristics of both the metal bond and abrasive.The findings indicate that the abrasive size and blasting distance significantly affect the erosive wear performance of the metal bond.Following a comprehensive analysis of the material removal rate of the metal bond and the erosive wear condition of cBN grains,optimal parameters for the working layer are determined:a blasting distance of 60 mm,a blasting time of 15 s,and SiC particle size of 100#.Furthermore,an advanced simulation model investigates the dressing process of abrasive blasting,revealing that the metal bond effectively inhibits crack propagation within cBN abrasive grains,thereby enhancing fracture toughness and impact resistance.Additionally,a comparative analysis is conducted between the grinding performance of porous cBN grinding wheels and vitrified cBN grinding wheels.The results demonstrate that using porous cBN grinding wheels significantly reduces grinding force,temperature,and chip adhesion,thereby enhancing the surface quality of the workpiece.展开更多
Continuous fiber-reinforced metal matrix composites(CFMMCs),reinforced by ceramic fibers(e.g.,Al_(2)O_(3)and SiC fibers)in a tough metal matrix,are extensively utilized in aerospace applications,such as engine casings...Continuous fiber-reinforced metal matrix composites(CFMMCs),reinforced by ceramic fibers(e.g.,Al_(2)O_(3)and SiC fibers)in a tough metal matrix,are extensively utilized in aerospace applications,such as engine casings and piston rods,because of their excellent high-temperature resistance and creep resistance.However,their heterogeneous composition presents machining challenges,including fiber pull-out,matrix adhesion,and increased tool wear.Ultrasonic vibration-assisted grinding(UVAG)effectively reduces grinding forces and abrasive wear.However,research on abrasive machining of specific CFMMCs is lacking.This study conducted single-grain cubic boron nitride grinding on SiC_(f)/TC17 with UVAG and compared the material removal mechanisms along two different directions(longitudinal fiber[LF]and transverse fiber[TF]).A simulation model was proposed to reveal the stress distribution and its propagation.Results showed that UVAG could effectively reduce grinding forces along both directions,with an average reduction of about 17.8%compared with conventional grinding.SiC fibers were removed in three models:micro-fractures,macro-fractures,and pull-outs.The introduction of ultrasonic energy mitigated fiber damage.The simulation model was consistent with Removal Model 1.The matrix’s surface stress during grinding along LF was more concentrated than that during grinding along TF under the action of the abrasive grain.The proposed model helps understand the removal behavior of CFMMCs.This research is expected to enhance the comprehension of abrasive machining of CFMMCs and facilitate their application in the aerospace field.展开更多
We propose to achieve nonreciprocal quantum control of photons in a quadratic optomechanical(QOM)system based on directional nonlinear interactions.We show that by optically pumping the QOM system in one side,the effe...We propose to achieve nonreciprocal quantum control of photons in a quadratic optomechanical(QOM)system based on directional nonlinear interactions.We show that by optically pumping the QOM system in one side,the effective QOM coupling can be enhanced significantly in that side,but not for the other side.This,contrary to the intuitive picture,allows the emergence of a nonreciprocal photon blockade in such optomechanical devices with weak single-photon QOM coupling.Our proposal opens up the prospect of exploring and utilizing quantum nonreciprocal optomechanics,with applications ranging from single-photon nonreciprocal devices to on-chip chiral quantum engineering.展开更多
Stimulated emission and absorption are two fundamental processes of light–matter interaction, and the coefficients of the two processes should be equal. However, we will describe a generic method to realize the signi...Stimulated emission and absorption are two fundamental processes of light–matter interaction, and the coefficients of the two processes should be equal. However, we will describe a generic method to realize the significant difference between the stimulated emission and absorption coefficients of two nondegenerate energy levels, which we refer to as a nonreciprocal transition. As a simple implementation, a cyclic three-level atom system, comprising two nondegenerate energy levels and one auxiliary energy level, is employed to show a nonreciprocal transition via a combination of synthetic magnetism and reservoir engineering. Moreover, a single-photon nonreciprocal transporter is proposed using two one-dimensional semi-infinite coupled-resonator waveguides connected by an atom with nonreciprocal transition effect. Our work opens up a route to design atom-mediated nonreciprocal devices in a wide range of physical systems.展开更多
The conformation-dependent activity of azo-benzene combretastatin A4(Azo-CA4)provides a unique approach to reduce the side-effects of chemotherapy,due to the light-triggered conformation transition of its azobenzene m...The conformation-dependent activity of azo-benzene combretastatin A4(Azo-CA4)provides a unique approach to reduce the side-effects of chemotherapy,due to the light-triggered conformation transition of its azobenzene moiety.Under hypoxic tumor microenviron-ment,however,the high expression of azoreductase can reduce azobenzene to aniline.It was postulated that the Azo-CA4 might be degraded under hypoxia,resulting in the decrease of its anti-tumor activity.The aim of this study was to verify such hypothesis in HeLa cells in vitro.The quantitative drug concentration analysis shows the ratio-metric formation of degradation end-products,confirming the bioreduction of Azo-CA4.The tubulin staining study indicates that Azo-CA4 loses the potency of switching off microtubule dynamics under hypoxia.Furthermore,the cell cycle analysis shows that the ability of Azo-CA4 to induce mitotic arrest is lost at low oxygen content.Therefore,the cytotoxicity of Azo-CA4 is compromised under hypoxia.In contrast,combretastatin A4 as a positive control maintains the potency to inhibit tubulin polymer-ization and break down the nuclei irrespective of light irradiation and oxygen level.This work highlights the influence of hypoxic tumor microenvironment on the anti-tumor potency of Azo-CA4,which should be considered during the early stage of designing translational Azo-CA4 delivery systems.展开更多
The tumor microenvironment features over-expressed hydrogen peroxide(H_(2)O_(2)).Thus,versatile therapeutic strategies based on H_(2)O_(2) as a reaction substrate to generate hydroxyl radical(•OH)have been used as a p...The tumor microenvironment features over-expressed hydrogen peroxide(H_(2)O_(2)).Thus,versatile therapeutic strategies based on H_(2)O_(2) as a reaction substrate to generate hydroxyl radical(•OH)have been used as a prospective therapeutic method to boost anticancer efficiency.However,the limited Fenton catalysts and insufficient endogenous H_(2)O_(2) content in tumor sites greatly hinder•OH production,failing to achieve the desired therapeutic effect.Therefore,supplying Fenton catalysts and elevating H_(2)O_(2) levels into cancer cells are effective strategies to improve•OH generation.These therapeutic strategies are systematically discussed in this review.Furthermore,the challenges and future developments of hydroxyl radical-involved cancer therapy are discussed to improve therapeutic efficacy.展开更多
We consider a SEIR epidemic model with infectious force in latent period and infected period under discontinuous treatment.The treatment rate has at most a finite number of jump discontinuities in every compact interv...We consider a SEIR epidemic model with infectious force in latent period and infected period under discontinuous treatment.The treatment rate has at most a finite number of jump discontinuities in every compact interval.By using Lyapunov theory for discontinuous differential equations and other techniques on non-smooth analysis,the basic reproductive number Ro is proved to be a sharp threshold value which completely determines the dynamics of the model.If Ro<1,then there exists a disease-free equilibrium which is globally stable.If Ro>1,the disease-free equilibrium becomes unstable and there exists an endemic equilibrium which is globally stable.We discuss that the disease will die out in a finite time which is impossible for the corresponding SEIR model with continuous treatment.Furthermore,the numerical simulations indicate that strengthening treatment measure after infective individuals reach some level is beneficial to disease control.展开更多
The progression of Alzheimer’s disease(AD)is characterized with the deposition and aggregation ofβ-amyloid(Aβ).Visualizing Aβaggregates at high spatial resolution is beneficial for AD diagnosis and treatment.Herei...The progression of Alzheimer’s disease(AD)is characterized with the deposition and aggregation ofβ-amyloid(Aβ).Visualizing Aβaggregates at high spatial resolution is beneficial for AD diagnosis and treatment.Herein,we designed a new molecule by conjugating corannulene(Cor)with rhodamine B isothiocyanate(Rhb),namely Cor-Rhb,for the nanoscopic imaging and modulating Aβpeptide fibrillation.The low duty cycle,high photon output and sufficient switching cycles enable Cor-Rhb suitable for localization-based nanoscopic fluorescence imaging.We find that Cor-Rhb can inhibit Aβpeptides fibrillization and interact directly with mature fibrils,triggering their disaggregation under light illumination.Noticeably reduced Aβ-mediated cytotoxicity after the addition of Cor-Rhb is also confirmed.These explorations suggest that Cor-Rhb displays great potential as a multifunctional therapeutic agent against amyloid-related diseases,and may largely facilitate a variety of super-resolution based biological applications.展开更多
Available,effectively converting low-frequency vibration into available electricity,triboelectric nanogenerator(TENG)is always research hot nowadays.However,the enhancing effect of the existing methods for the output ...Available,effectively converting low-frequency vibration into available electricity,triboelectric nanogenerator(TENG)is always research hot nowadays.However,the enhancing effect of the existing methods for the output have all sorts of drawbacks,i.e..展开更多
基金supported by the Key Teaching Reform and Practice Project of Pingdingshan University in 2023,titled“Research and Practice on Innovation and Entrepreneurship Pathways for Medical Students under the New Medical Discipline Framework”(Project No.2023-JYZD15)Additionally,this study received support from the Henan Province Higher Education Teaching Reform Research and Practice Project,titled“Research on the Integration Path of Medical Education and Innovation&Entrepreneurship Education under the‘Project-based+Mentorship System’Model”(Project No.2024SJGLX0495).
文摘The construction of the New Medical Sciences aims to cultivate interdisciplinary medical talents,placing higher demands on physiology experiment teaching.In light of the challenges of traditional teaching,such as outdated content,a single assessment mechanism,low student engagement,and limited research experience among instructors,this study proposes a reform pathway centered on research competence development,supported by diversified evaluation methods and the deep integration of ideological and scenario-based teaching.By optimizing teaching content,introducing innovative projects,establishing a multidimensional assessment system,and strengthening faculty development,the proposed reforms effectively enhance students’Innovative ability and practical skills.This study provides theoretical insights and practical experience for training interdisciplinary medical professionals to meet the demands of the new era.
基金financially supported by the National Natural Science Foundation of China(Nos.21271022,51972180,and 51572134)the Program for Scientific Research Innovation Team in Colleges and Universities of Jinan(No.2018GXRC006)the Key Research&Development Project of Shandong Province(No.2019GGX102070)。
文摘In recent years,photocatalytic technologies have been extensively studied and diffusely used in water splitting,decomposition of organic pollutants,reduction of carbon dioxide,etc.As a type of eye-catching semiconductors,BiVO_(4),Bi_(2)WO_(6),and Bi_(2)MoO_(6) (denoted as BiaAOb)have become a hotspot in photocatalytic researches due to their crystal structure stability,high light quantum and electronic transmission efficiency,and outstanding energy utilization capacity.However,pristine BiaAOb(A=V,W,and Mo)possesses several drawbacks,such as low separation efficiency of photo-excited electron-hole pairs,low specific surface area,as well as the poor quantum utilization,which restrict their photocatalytic performance.Considerable efforts,such as nanostructure modification,surface engineering,and heterojunction/homojunction fabrication,have been conducted to solve these problems.This integrated review aims to sum up recent advances in current studies on fabrication of high efficiency BiaAOb photocatalysts to accelerate the developments of BiaAOb-based materials in the photocatalysis(PC)field.The current challenges and prospects of BiaAOb are emphasized which stretches the existing fundamental theories of PC as well as provide a promising strategy to fabricate high efficiency BiaAOb catalysts to control environmental pollution and assist the sustainable development of energy.
基金financially supported by the National Natural Science Foundation of China(Nos.51921003 and 51775275)National Major Science and Technology Projects of China(No.2017-VII-0002-0095)Six Talents Summit Project in Jiangsu Province(No.JXQC-002)。
文摘Fretting wear has an adverse impact on the fatigue life of turbine blade roots.The current work is to comparatively investigate the fretting wear behaviour of the nickel-based superalloy surfaces produced by polishing and creep-feed profile grinding,respectively,in terms of surface/subsurface fretting damage,the friction coefficient,wear volume and wear rate.Experimental results show that the granulated tribolayer aggravates the workpiece wear,while the flat compacted tribolayer enhances the wear resistance ability of workpiece,irrespective of whether the workpiece is processed by polishing or grinding.However,the wear behaviors of tribolayers are different.For the polished surface,when the normal load exceeds 100 N,the main defects are crack,rupture,delamination and peeling of workpiece materials;the wear mechanism changes from severe oxidative wear to fatigue wear and abrasive wear when the loads increase from 50 to 180 N.As for the ground surface,the main wear mechanism is abrasive wear.Particularly,the ground surface possesses better wear-resistant ability than the polished surface because the former has the lower values in coefficient friction(0.23),wear volume(0.06×10^(6)μm^(3))and wear rate(0.25×10^(-16)Pa^(-1)).Finally,an illustration is given to characterize the evolution of wear debris on such nickel-based superalloy on the ground surface.
基金financially supported by the National Natural Science Foundation of China(Nos.92160301,92060203,52175415 and 52205475)the Science Center for Gas Turbine Project(Nos.P2022-AB-Ⅳ-002-001 and P2023-B-Ⅳ-003-001)+4 种基金the Natural Science Foundation of Jiangsu Province(No.BK20210295)the Superior Postdoctoral Project of Jiangsu Province(No.2022ZB215)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX23_0355)the Interdisciplinary Innovation Fund for Doctoral Students of Nanjing University of Aeronautics and Astronautics(KXKCXJJ202305)the Fundamental Research Funds for the Central Universities(Nos.NS2023028 and NG2024015)。
文摘Gamma titanium-aluminum intermetallic compounds(γ-TiAl)have gained considerable attentions in the aerospace industry due to their exceptional thermal resilience and comprehensive attributes,making them a prime example of lightweight and advanced materials.To address the frequent occurrence of burns and severe tool deterioration during the process of high-efficiency deep grinding(HEDG)onγ-TiAl alloys,ultrasonic vibration-assisted high-efficiency deep grinding(UVHEDG)has been emerged.Results indicate that in UVHEDG,the grinding temperature is on average 15.4%lower than HEDG due to the employment of ultrasonic vibrations,enhancing coolant penetration into the grinding area and thus reducing heat generation.Besides,UVHEDG possesses superior performance in terms of grinding forces compared to HEDG.As the material removal volume(MRV)increases,the tangential grinding force(F_(t))and normal grinding force(F_(n))of UVHEDG increase but to a lesser extent than in HEDG,with an average reduction of16.25%and 14.7%,respectively.UVHEDG primarily experiences microfracture of grains,whereas HEDG undergoes large-scale wear later in the process due to increased grinding forces.The surface roughness(R_(a))characteristics of UVHEDG are superior,with the average value of R_(a)decreasing by 46.5%compared to HEDG as MRV increases.The surface morphology in UVHEDG exhibits enhanced smoothness and a shallower layer of plastic deformation.Grinding chips generated by UVHEDG show a more shear-like shape,with the applied influence of ultrasonic vibration on chip morphology,thereby impacting material removal behaviors.These aforementioned findings contribute to enhanced machining efficiency and product quality ofγ-TiAl alloys after employing ultrasonic vibrations into HEDG.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11875295 and 11535003)Provincial Science and Technology Major Project of Anhui Province,China(Grant No.17030801035)Key Program of 13th Five-year Plan,CASHIPS,China(Grant No.KP-2017-25)
文摘To obtain large-volume non-thermal arc plasma(NTAP), a multiple NTAP generator with three pairs of electrodes has been developed. The arc plasma characteristics, including dynamic process, spatial distribution, and rotation velocity in the discharge zone, were investigated by high speed photograph and image processing methods. The results showed that the dynamic behaviors and spatial distribution of the arc plasma were strongly related to the electrode configuration.A swirl flow of multi-arc plasma was formed by adjusting the electrode configuration, and a steady luminance area was clearly observed in the center of the discharge zone. Moreover, the size of the luminance area increased by decreasing the gas flow rate. The electrical connection in series could be formed between/among these arc columns with their respective driving power supplies in the multi-arc dynamic evolution process. An approximately periodical process of acceleration and deceleration of the arc rotation velocity was observed in the multi-arc generator with swirl flow configuration. In general, the mean velocity of arc rotation was higher in the multi-arc generator with swirl flow configuration when a pair of electrodes driven by a power supply were opposite to each other rather than adjacent.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11875295 and 11535003)the National Key R&D Program of China(Grant No.2019YFC0119000)+1 种基金Provincial Science and Technology Major Project of Anhui Province,China(Grant No.17030801035)Key Program of 13th Five-Year Plan,CASHIPS,China(Grant No.KP-2017-25).
文摘We investigate characteristics of multi-arc torches with three pairs of electrodes(three cathodes and three anodes)and their performance on the spheroidization of SiO2 powder.The effect of electrode arrangement,including adjacent pattern(AD pattern,adjacent electrodes powered by one power supply)and opposite pattern(OP pattern,opposite electrodes powered by one power supply),on the dynamics of arc plasma is investigated based on synchronous acquisition of electrical and optical signals.The results show that both the voltage and spatial distribution of each arc of multiple arcs are more stable compared with those of a single arc.The fluctuation of an arc in multiple arcs mainly comes from the small-scale arc-to-arc restrikes among multiple arcs.Moreover,these arc-to-arc restrikes occur more frequently among multiple arc columns in OP pattern than in AD pattern.Moreover,the high-temperature area of the central region of arc chamber in OP pattern is larger than that in AP pattern.For the spheroidization of SiO2 in this multi-arc generator,the spheronization degrees of plasma treated silica in OP pattern are at least 20%higher than those in AD pattern.
基金supported by National Natural Science Foundation of China(No.11875295)the National Key R&D Program of China(No.2019YFC0119000)。
文摘The enhanced volume of thermal plasma is produced by a multi-arc thermal plasma generator with three pairs of discharge electrodes driven by three directed current power suppliers.Combined with a high-speed camera and an oscilloscope,which acquire optical and electric signals synchronously,the dynamic behavior of different kinds of multi-arc discharge adjusted by the electrode arrangement is investigated.Also,the spatial distributions and instability of the arc discharge are analyzed in four electrode configurations using the gray value statistical method.It is found that the cathodic arcs mainly show a contracting state,while the anodic arcs have a trend of transition from shrinkage to a diffusion-like state with the increase of the discharge current.As a result of the adjustment of the electrode configuration,a high temperature region formed in the center of the discharge region in configurations of adjacent electrodes with opposite flow distribution and opposite electrodes with swirl flow distribution due to severe fluctuation of arcs.The discharge voltage rises with increased discharge current in this novel multi-arc plasma generator.It is also found that anode ablation mainly occurs on the conical surface at the copper electrode tip,while cathode erosion mainly occurs on the surface of the inserted tungsten and the nearby copper.
基金financially supported by the National Natural Science Foundation of China(Nos.51921003,92160301 and 52175415)the Fundamental Research Funds for the Central University(No.NP2022441)+1 种基金the Natural Science Foundation of Jiangsu Province(No.BK20210295)the Open Foundation State Key Laboratory of Mechanical Transmissions(No.SKLMT-MSKFKT-202101).
文摘Cubic boron nitride(cBN)superabrasive grinding wheels exhibit unique advantages in the grinding of difficult-to-cut materials with high strength and toughness,such as titanium alloys and superalloys.However,grinding with multilayered metallic cBN superabrasive wheels faces problems in terms of grain wear resistance,the chip storage capability of the working layers and the stability and controllability of the dressing process.Therefore,in this work,novel metallic cBN superabrasive wheels with aggregated cBN(AcBN)grains and open pore structures were fabricated to improve machining efficiency and surface quality.Prior to the grinding trials,the airborne abrasive blasting process was conducted and the abrasive blasting parameters were optimized in view of wear properties of cBN grains and metallic matrix materials.Subsequently,the comparative experiments were performed and then the variations in grinding force and force ratio,grinding temperature,tool wear morphology and ground surface quality of the multilayered AcBN grinding wheels were investigated during machining Ti-6Al-4V alloys.In consideration of the variations of grain erosion wear volume and material removal rate per unit of pure metallic matrix materials as the abrasive blasting parameters changes,the optimal abrasive blasting parameters were identified as the SiC abrasive mesh size of 60#and the abrasive blasting distance and time of 60 mm and 15 s,respectively.The as-developed AcBN grains exhibited better fracture toughness and impact resistance than monocrystalline cBN(McBN)grains because of the existence of metal-bonded materials amongst multiple cBN particles that decreased crack propagation inside whole grains.The metallic porous AcBN wheels had lower grinding forces and temperature and better ground surface quality than vitrified McBN wheels due to the constant layer-by-layer exposure of cBN particles in the working layer of AcBN wheels.
基金Supported by National Natural Science Foundation of China(Grant Nos.92160301,92060203,52175415,52205475,and 52205493)Science Center for Gas Turbine Project(Grant Nos.P2022-AB-IV-002-001 and P2023-B-IV-003-001)+3 种基金Jiangsu Provincial Natural Science Foundation(Grant No.BK20210295)the Huaqiao University Engineering Research Center of Brittle Materials Machining(Grant No.2023IME-001)Foundation of Graduate Innovation Centre in NUAA(Grant No.XCXJH20230509)Fundamental Research Funds for the Central Universities(Grant Nos.NS2023028 and NG2024015).
文摘Cubic boron nitride(cBN)grinding wheels play a pivotal role in precision machining,serving as indispensable tools for achieving exceptional surface quality.Ensuring the sharpness of cBN grains and optimizing the grinding wheel’s chip storage capacity are critical factors.This paper presents a study on the metal-bonded segments and single cBN grain samples using the vacuum sintering method.It investigates the impact of blasting parameters-specifically silicon carbide(SiC)abrasive size,blasting distance,and blasting time-on the erosive wear characteristics of both the metal bond and abrasive.The findings indicate that the abrasive size and blasting distance significantly affect the erosive wear performance of the metal bond.Following a comprehensive analysis of the material removal rate of the metal bond and the erosive wear condition of cBN grains,optimal parameters for the working layer are determined:a blasting distance of 60 mm,a blasting time of 15 s,and SiC particle size of 100#.Furthermore,an advanced simulation model investigates the dressing process of abrasive blasting,revealing that the metal bond effectively inhibits crack propagation within cBN abrasive grains,thereby enhancing fracture toughness and impact resistance.Additionally,a comparative analysis is conducted between the grinding performance of porous cBN grinding wheels and vitrified cBN grinding wheels.The results demonstrate that using porous cBN grinding wheels significantly reduces grinding force,temperature,and chip adhesion,thereby enhancing the surface quality of the workpiece.
基金supported by the National Natural Science Foundation of China(Grant Nos.92160301,92060203,52175415,and 52205475)the Science Center for Gas Turbine Project(Grant No.P2023-B-IV-003-001)+1 种基金the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20210295)the State Key Laboratory of Mechanics and Control for Aerospace Structures(Nanjing University of Aeronautics and Astronautics,China)(Grant No.MCAS-S-0423G02).
文摘Continuous fiber-reinforced metal matrix composites(CFMMCs),reinforced by ceramic fibers(e.g.,Al_(2)O_(3)and SiC fibers)in a tough metal matrix,are extensively utilized in aerospace applications,such as engine casings and piston rods,because of their excellent high-temperature resistance and creep resistance.However,their heterogeneous composition presents machining challenges,including fiber pull-out,matrix adhesion,and increased tool wear.Ultrasonic vibration-assisted grinding(UVAG)effectively reduces grinding forces and abrasive wear.However,research on abrasive machining of specific CFMMCs is lacking.This study conducted single-grain cubic boron nitride grinding on SiC_(f)/TC17 with UVAG and compared the material removal mechanisms along two different directions(longitudinal fiber[LF]and transverse fiber[TF]).A simulation model was proposed to reveal the stress distribution and its propagation.Results showed that UVAG could effectively reduce grinding forces along both directions,with an average reduction of about 17.8%compared with conventional grinding.SiC fibers were removed in three models:micro-fractures,macro-fractures,and pull-outs.The introduction of ultrasonic energy mitigated fiber damage.The simulation model was consistent with Removal Model 1.The matrix’s surface stress during grinding along LF was more concentrated than that during grinding along TF under the action of the abrasive grain.The proposed model helps understand the removal behavior of CFMMCs.This research is expected to enhance the comprehension of abrasive machining of CFMMCs and facilitate their application in the aerospace field.
基金Natural Science Foundation of Jiangxi Province(20192ACB21002)National Natural Science Foundation of China(11604096,11904013,11847165,11474087,11774086,11935006,11775190)。
文摘We propose to achieve nonreciprocal quantum control of photons in a quadratic optomechanical(QOM)system based on directional nonlinear interactions.We show that by optically pumping the QOM system in one side,the effective QOM coupling can be enhanced significantly in that side,but not for the other side.This,contrary to the intuitive picture,allows the emergence of a nonreciprocal photon blockade in such optomechanical devices with weak single-photon QOM coupling.Our proposal opens up the prospect of exploring and utilizing quantum nonreciprocal optomechanics,with applications ranging from single-photon nonreciprocal devices to on-chip chiral quantum engineering.
基金National Natural Science Foundation of China(12064010,11904013,11847165,11775190)Natural Science Foundation of Jiangxi Province(20192ACB21002)+2 种基金National Basic Research Program of China(973 Program)(2014CB921401)Tsinghua University Initiative Scientific Research ProgramTsinghua National Laboratory for Information Science and Technology(TNList)Crossdiscipline Foundation。
文摘Stimulated emission and absorption are two fundamental processes of light–matter interaction, and the coefficients of the two processes should be equal. However, we will describe a generic method to realize the significant difference between the stimulated emission and absorption coefficients of two nondegenerate energy levels, which we refer to as a nonreciprocal transition. As a simple implementation, a cyclic three-level atom system, comprising two nondegenerate energy levels and one auxiliary energy level, is employed to show a nonreciprocal transition via a combination of synthetic magnetism and reservoir engineering. Moreover, a single-photon nonreciprocal transporter is proposed using two one-dimensional semi-infinite coupled-resonator waveguides connected by an atom with nonreciprocal transition effect. Our work opens up a route to design atom-mediated nonreciprocal devices in a wide range of physical systems.
基金The work was financially supported by the National Natural Science Foundation of China(Grant No.21650110447).
文摘The conformation-dependent activity of azo-benzene combretastatin A4(Azo-CA4)provides a unique approach to reduce the side-effects of chemotherapy,due to the light-triggered conformation transition of its azobenzene moiety.Under hypoxic tumor microenviron-ment,however,the high expression of azoreductase can reduce azobenzene to aniline.It was postulated that the Azo-CA4 might be degraded under hypoxia,resulting in the decrease of its anti-tumor activity.The aim of this study was to verify such hypothesis in HeLa cells in vitro.The quantitative drug concentration analysis shows the ratio-metric formation of degradation end-products,confirming the bioreduction of Azo-CA4.The tubulin staining study indicates that Azo-CA4 loses the potency of switching off microtubule dynamics under hypoxia.Furthermore,the cell cycle analysis shows that the ability of Azo-CA4 to induce mitotic arrest is lost at low oxygen content.Therefore,the cytotoxicity of Azo-CA4 is compromised under hypoxia.In contrast,combretastatin A4 as a positive control maintains the potency to inhibit tubulin polymer-ization and break down the nuclei irrespective of light irradiation and oxygen level.This work highlights the influence of hypoxic tumor microenvironment on the anti-tumor potency of Azo-CA4,which should be considered during the early stage of designing translational Azo-CA4 delivery systems.
基金The authors acknowledge the financial support from the Tianjin Science and Technology Committee(Grant No.19JCYBJC28400)the Basic Research General Program of Shenzhen Science and Technology Innovation Commission in 2020(Grant No.JCYJ20190806162412752).
文摘The tumor microenvironment features over-expressed hydrogen peroxide(H_(2)O_(2)).Thus,versatile therapeutic strategies based on H_(2)O_(2) as a reaction substrate to generate hydroxyl radical(•OH)have been used as a prospective therapeutic method to boost anticancer efficiency.However,the limited Fenton catalysts and insufficient endogenous H_(2)O_(2) content in tumor sites greatly hinder•OH production,failing to achieve the desired therapeutic effect.Therefore,supplying Fenton catalysts and elevating H_(2)O_(2) levels into cancer cells are effective strategies to improve•OH generation.These therapeutic strategies are systematically discussed in this review.Furthermore,the challenges and future developments of hydroxyl radical-involved cancer therapy are discussed to improve therapeutic efficacy.
基金supported by the National Nature Science Foundation of China(11271154).
文摘We consider a SEIR epidemic model with infectious force in latent period and infected period under discontinuous treatment.The treatment rate has at most a finite number of jump discontinuities in every compact interval.By using Lyapunov theory for discontinuous differential equations and other techniques on non-smooth analysis,the basic reproductive number Ro is proved to be a sharp threshold value which completely determines the dynamics of the model.If Ro<1,then there exists a disease-free equilibrium which is globally stable.If Ro>1,the disease-free equilibrium becomes unstable and there exists an endemic equilibrium which is globally stable.We discuss that the disease will die out in a finite time which is impossible for the corresponding SEIR model with continuous treatment.Furthermore,the numerical simulations indicate that strengthening treatment measure after infective individuals reach some level is beneficial to disease control.
基金This work was supported by the National Natural Science Foundation of China(Nos.22174079 and 21974073).
文摘The progression of Alzheimer’s disease(AD)is characterized with the deposition and aggregation ofβ-amyloid(Aβ).Visualizing Aβaggregates at high spatial resolution is beneficial for AD diagnosis and treatment.Herein,we designed a new molecule by conjugating corannulene(Cor)with rhodamine B isothiocyanate(Rhb),namely Cor-Rhb,for the nanoscopic imaging and modulating Aβpeptide fibrillation.The low duty cycle,high photon output and sufficient switching cycles enable Cor-Rhb suitable for localization-based nanoscopic fluorescence imaging.We find that Cor-Rhb can inhibit Aβpeptides fibrillization and interact directly with mature fibrils,triggering their disaggregation under light illumination.Noticeably reduced Aβ-mediated cytotoxicity after the addition of Cor-Rhb is also confirmed.These explorations suggest that Cor-Rhb displays great potential as a multifunctional therapeutic agent against amyloid-related diseases,and may largely facilitate a variety of super-resolution based biological applications.
基金We are also grateful for the General Program of National Natural Science Foundation of China(NSFC,No.52075061)the support of the National Key Research and Development Program of China(No.2019YFB2004800)+2 种基金the Fundamental Research Funds for the Central Universities(No.2019CDCGGD320)the Chongqing University Scientific Research Reserve Top Talent Cultivation Program(CQU2019HBRC1A04)The authors also gratefully acknowledge financial support from project of open foundation from Defence Key Disciplines Lab of Novel Micro-Nano Devices and System Technology graduate scientific research and innovation foundation of College of Optoelectronic Engineering,Chongqing University,Chongqing,China(Grant No.GDYKC202004).
文摘Available,effectively converting low-frequency vibration into available electricity,triboelectric nanogenerator(TENG)is always research hot nowadays.However,the enhancing effect of the existing methods for the output have all sorts of drawbacks,i.e..
