Glucose molecules are of great significance being one of the most important molecules in metabolic chain.However,due to the small Raman scattering cross-section and weak/non-adsorption on bare metals,accurately obtain...Glucose molecules are of great significance being one of the most important molecules in metabolic chain.However,due to the small Raman scattering cross-section and weak/non-adsorption on bare metals,accurately obtaining their"fingerprint information"remains a huge obstacle.Herein,we developed a tip-enhanced Raman scattering(TERS)technique to address this challenge.Adopting an optical fiber radial vector mode internally illuminates the plasmonic fiber tip to effectively suppress the background noise while generating a strong electric-field enhanced tip hotspot.Furthermore,the tip hotspot approaching the glucose molecules was manipulated via the shear-force feedback to provide more freedom for selecting substrates.Consequently,our TERS technique achieves the visualization of all Raman modes of glucose molecules within spectral window of 400-3200 cm^(-1),which is not achievable through the far-field/surface-enhanced Raman,or the existing TERS techniques.Our TERS technique offers a powerful tool for accurately identifying Raman scattering of molecules,paving the way for biomolecular analysis.展开更多
Postgrouting at the pile tip enhances the performance of cast-in-place piles.To clarify the performance of tip and side resistances,this study analyzed static load test data from two test piles before and after grouti...Postgrouting at the pile tip enhances the performance of cast-in-place piles.To clarify the performance of tip and side resistances,this study analyzed static load test data from two test piles before and after grouting.Mechanisms underlying an improvement in tip resistance and the influence of postgrouting on side resistance were investigated via theoretical analysis.Finally,a design method for tip resistance control via settlement was proposed.Results indicate that the ultimate bearing capacity of piles increases after grouting compared to before,underscoring the importance of tip grouting in gravelly soils and its profound impact on load transmission in pile foundations.Postgrouting at the pile tip enhances the strength as well as initial stiffness of the bearing stratum,ultimately elevating the overall pile foundation-bearing capacity.Additionally,tip grouting helps in strengthening over-all side resistance,especially around the pile tip.The grouting procedure has an impact on the soil’s arching effect at the pile tip;the extent of the arching effect and an increase in horizontal tension close to the pile tip are positively correlated with the effectiveness of grouting reinforcement.The design method for tip resistance control via settlement based on measured data statistics was validated using engineering examples,and the method has a practical reference value.展开更多
Precise control and measurement of nanoparticles using low-power optical tweezers are pivotal for advancing single-particle analysis,nanoscale sensing,and energy transport research.In this work,we present the tipassis...Precise control and measurement of nanoparticles using low-power optical tweezers are pivotal for advancing single-particle analysis,nanoscale sensing,and energy transport research.In this work,we present the tipassisted nanoparticle capture system that simultaneously achieves localized temperature probing and nanoparticle trapping,significantly lowering the required laser power input.Unlike traditional metal-tip plasmonic techniques that predominantly rely on intense electric field gradients,our approach employs a silicon nanotip under resonant laser excitation,uniquely integrating optical forces,thermophoretic forces,and interatomic interactions for stable nanoparticle confinement.This synergistic collaboration mechanism enables approximately a 42%reduction in laser power density compared to conventional bowtie nanoaperture methods.This experimental method achieved direct and simultaneous Raman-based measurements of localized thermal dynamics,providing new insights into nanoscale thermodynamics during optical trapping.Additionally,the silicon nanotip demonstrates reduced thermal transport due to its confined nanoscale geometry,aligning closely with our theoretical predictions.Our integrated strategy of efficient nanoparticle manipulation coupled with precise thermal probing not only enhances overall energy efficiency but also broadens the scope of potential applications in cutting-edge nanoscience and nanotechnology.展开更多
Low-electrode capacitive deionization(FCDI)is an emerging desalination technology with great potential for removal and/or recycling ions from a range of waters.However,it still suffers from inefficient charge transfer...Low-electrode capacitive deionization(FCDI)is an emerging desalination technology with great potential for removal and/or recycling ions from a range of waters.However,it still suffers from inefficient charge transfer and ion transport kinetics due to weak turbulence and low electric intensity in flow electrodes,both restricted by the current collectors.Herein,a new tip-array current collector(designated as T-CC)was developed to replace the conventional planar current collectors,which intensifies both the charge transfer and ion transport significantly.The effects of tip arrays on flow and electric fields were studied by both computational simulations and electrochemical impedance spectroscopy,which revealed the reduction of ion transport barrier,charge transport barrier and internal resistance.With the voltage increased from 1.0 to 1.5 and 2.0 V,the T-CC-based FCDI system(T-FCDI)exhibited average salt removal rates(ASRR)of 0.18,0.50,and 0.89μmol cm^(-2) min^(-1),respectively,which are 1.82,2.65,and 2.48 folds higher than that of the conventional serpentine current collectors,and 1.48,1.67,and 1.49 folds higher than that of the planar current collectors.Meanwhile,with the solid content in flow electrodes increased from 1 to 5 wt%,the ASRR for T-FCDI increased from 0.29 to 0.50μmol cm^(-2) min^(-1),which are 1.70 and 1.67 folds higher than that of the planar current collectors.Additionally,a salt removal efficiency of 99.89%was achieved with T-FCDI and the charge efficiency remained above 95%after 24 h of operation,thus showing its superior long-term stability.展开更多
Background: Reconstruction of Nasal Tip Columella (NTC) subunits is one of the most challenging aspects in functional aesthetic rhinoplasty. Moreover, racial variation for Asian nose rhinoplasty could even demand soph...Background: Reconstruction of Nasal Tip Columella (NTC) subunits is one of the most challenging aspects in functional aesthetic rhinoplasty. Moreover, racial variation for Asian nose rhinoplasty could even demand sophistication of tip and columella strut graft infrastructure enhancement. Various autogenous graft options such as 6th costal cartilage, septal cartilage and conchal cartilage are very commonly considered whilst the 10th costal cartilage is scarcely reported. Objective and Method: The purpose of this manuscript is to illustrate the detailed operative steps to harvest the 10th costal cartilage for infrastructural grafting at NTC subunits by a case illustration. The pros and cons of different cartilage options will be discussed, particularly its application in cleft nose rhinoplasty in Chinese patient. We have adopted the 10th rib as the key option for NTC reconstruction in 11 cases of Chinese cleft secondary rhinoplasty since 2019 and have achieved good and stable results without complications. Conclusion: The 10th costal cartilage is one of the best options in Nasal Tip Columella subunits reconstruction, particularly in complex cleft nose or failure revision aesthetic rhinoplasty cases, due to its safety of harvesting, and the sufficient quality and quantity of grafting materials it provides for simultaneous adjunctive augmentation purpose.展开更多
Root tips are the main components of absorptive fine roots,but their seasonal dynamics and relationship to environmental factors remain unclear due to the difficulties in methodology.In this study,we explored the temp...Root tips are the main components of absorptive fine roots,but their seasonal dynamics and relationship to environmental factors remain unclear due to the difficulties in methodology.In this study,we explored the temporal patterns of root-tip production and mortality in monoculture plantations of five temperate tree species at a common site in northeastern China,and identified the general environmental controls on such processes.We made monthly in-situ assessments of root tip length(RTL)production and mortality in two hardwood and three coniferous species with a minirhizotron(MR)method during the growing seasons of 2008 and 2009.Air temperature,rainfall,soil temperature and water content at 10 cm depth were determined concurrently.RTL production in all species exhibited consistent peaks in summer(June–August)in two growing seasons.RTL mortality showed substantial interannual and interspecific variability,with peaks in autumn and winter in 2008,but various patterns in 2009.RTL production positively correlated with monthly soil and air temperature across all species,and with monthly rainfall in three coniferous species.However,there was no significant correlation between RTL production and soil water content.By contrast,RTL mortality was weakly related to environmental factors,showing positive correlations with soil temperature in Korean spruce,and with rainfall in Korean pine and Korean spruce.Our findings suggest that the seasonal patterns of RTL production are convergent across the five temperate tree species due to the overlapped distribution of heat and rainfall,which can conduce roots to maximizing the acquisition of nutrient resources in the soil.展开更多
Anti-aliasing spectrum analysis is essential for rotor blade condition monitoring based on Blade Tip Timing(BTT).The Multiple Signal Classification(MUSIC)algorithm,which exploits the orthogonality between signal and n...Anti-aliasing spectrum analysis is essential for rotor blade condition monitoring based on Blade Tip Timing(BTT).The Multiple Signal Classification(MUSIC)algorithm,which exploits the orthogonality between signal and noise subspaces,has been successfully applied for this purpose.However,conventional subspace selection methods relying on fixed thresholds are sensitive to variations in large eigenvalues.Furthermore,the complex disturbances during rotor operation and measurement complicate the identification of blade vibration characteristics.To overcome these challenges,this paper proposes Adaptive Subspace Separation(ASS)and Local Spectral Centroid(LSC)methods to improve the adaptability of subspace selection and the stability of frequency identification,respectively.The impacts of overestimating and underestimating the subspace dimensions on MUSIC's performance are derived mathematically.Simulation and experiments demonstrate the effectiveness of proposed approaches:ASS offers more accurate and stable subspace dimension selection and tracking,while LSC reduces the standard deviation of estimated frequencies by 30 percent.展开更多
The fabrication of nanostructures beyond the diffraction limit has been the focus of nanotechnology research.Scanning probe microscopy(SPM)has attracted the attention of researchers for the detection and manufacture o...The fabrication of nanostructures beyond the diffraction limit has been the focus of nanotechnology research.Scanning probe microscopy(SPM)has attracted the attention of researchers for the detection and manufacture of nanostructures.Here,a nanosecond laser irradiated a cantilevered scanning nearfield optical microscopy(SNOM)tip and directly wrote subwavelength nanostructures on Au nano-film,without the assistance of a mask or vacuum atmosphere.This method was stable and reproducible for long-term use.The in situ morphology detection was conducted after the writing process by atomic force microscope(AFM).A feature linewidth of approximately 83.6 nm(<k/6)was confirmed using scanning electron microscopy(SEM).Linewidth of(167.8±6.6)nm was reproduced stably.Theoretical calculations revealed that the elliptical heat distribution under the SNOM tip generated different linewidths when the tip scanned vertically and horizontally.It also interpreted the influential mechanism of single-pulse energy.The simulated linewidths were consistent with the fabricated linewidths.According to the elemental analysis by energy dispersive spectrometer(EDS),the mechanism of this method can be interpreted asmelting of the Au nano-film instead of oxidation.Owing to its high positioning,machining accuracy,and instantaneous energy,this technology is considered convenient and economical for nanostructure fabrication and is proposed to be applied in nanolithography on multiple materials in the future.展开更多
The existence of the aeroengine casing,limited monitoring points,and multi-fault characteristics make obtaining the rotor’s vibration transmission characteristics challenging,resulting in difficulties accurately iden...The existence of the aeroengine casing,limited monitoring points,and multi-fault characteristics make obtaining the rotor’s vibration transmission characteristics challenging,resulting in difficulties accurately identifying the rotor unbalance.This paper utilizes a high-frequency composite sensor to monitor the engine’s blade tip clearance(BTC)and extracts unbalanced information from BTC signals for rotor dynamic balancing,while avoiding the need for the once per revolution(OPR)sensor.First,the vibration characteristics of the rotor-blade system under multi-fault conditions are investigated.Then,based on BTC measurement,a none OPR method and an unbalance identification method are proposed,in which the radial vibration of the blade tip in the BTC signals at different speeds is extracted and operated in the time domain to obtain the rotor unbalanced vibration,the signal is reconstructed,and cross-correlation analysis is used to accurately identify the magnitude and phase of the unbalanced signal.Finally,a rotor test bench is utilized for experimental verification.The results reveal that the dynamic balancing method based on the BTC signal can more precisely identify the rotor unbalance than the traditional rotor dynamic balancing method.The application of this technique will effectively improve engine health management and fault prediction.展开更多
BACKGROUND Despite advancements,endoscopic retrograde cholangiopancreatography(ERCP)poses challenges,including the risk of post-ERCP pancreatitis and difficulty of biliary cannulation.AIM To compare dome and tapered t...BACKGROUND Despite advancements,endoscopic retrograde cholangiopancreatography(ERCP)poses challenges,including the risk of post-ERCP pancreatitis and difficulty of biliary cannulation.AIM To compare dome and tapered tip sphincterotomes,focusing on their efficacy in achieving successful biliary cannulation and reducing the incidence of post-ERCP pancreatitis.METHODS In this prospective,single-blind,randomized pilot study conducted at Inha Uni-versity Hospital,85 patients undergoing ERCP were equally divided into dome and tapered tip sphincterotome groups.The co-primary outcomes were the success rate of selective biliary cannulation and incidence of post-ERCP pancre-atitis.The secondary outcomes included biliary cannulation time,number of unintended pancreatic duct access events,and total procedure time.RESULTS The success rates of selective biliary cannulation were 74.4%and 85.7%in the dome and tapered tip groups,respectively,with no significant difference(P=0.20).Similarly,the incidence of post-ERCP pancreatitis did not differ significantly between the groups(5 cases in the tapered tip group vs 6 in the dome tip group,P=0.72).However,difficult cannulation was significantly more common in the dome tip group than in the tapered tip group(P=0.05).Selective biliary cannula-tion time emerged as a significant predictor of post-ERCP pancreatitis(multivariate odds ratio=9.33,95%confi-dence interval:1.31-66.44,P=0.03).CONCLUSION This study indicated that the sphincterotome tip type does not markedly affect biliary cannulation success or post-ERCP pancreatitis rates.However,cannulation duration is a key risk factor for post-ERCP pancreatitis.These findings provide preliminary insights that highlight the importance of refining ERCP practices,including sphinc-terotome selection,while underscoring the need for larger multicenter studies to improve procedure time and patient safety.展开更多
The Stokes–Einstein–Debye(SED) relation in TIP5P water is tested with the original formula and its variants within the temperature range 240–390 K. The results indicate that although the variants explicitly break d...The Stokes–Einstein–Debye(SED) relation in TIP5P water is tested with the original formula and its variants within the temperature range 240–390 K. The results indicate that although the variants explicitly break down, the original SED relation is almost valid. Compared with the Stokes–Einstein relation, no explicit decoupling is observed in translational and rotational motion. Variation of the effective hydrodynamic radius is critical to testing the validity of the SED relation.展开更多
Permafrost,a critical component of Earth’s climate system,is increasingly subject to abrupt thaw events,which jeopardize infrastructure,reshape landforms,alter hydrological regimes,and disrupt ecosystems,thereby posi...Permafrost,a critical component of Earth’s climate system,is increasingly subject to abrupt thaw events,which jeopardize infrastructure,reshape landforms,alter hydrological regimes,and disrupt ecosystems,thereby posing substantial threats to global sustainability.However,the underlying mechanisms that trigger these abrupt transitions remain incompletely understood.Here,we present decade-long in-situ observations from HRQ1,a marginal permafrost site in the Headwater Area of the Yellow River,northeastern Qinghai-Xizang Plateau.These data reveal the formation and growth of a talik,indicative of a permafrost tipping point.Absent before 2017,the talik subsequently formed and progressively deepened,extending to the maximum observation depth of 300 cm by 2024.The transition from perennially frozen to thawed conditions was accompanied by a substantial increase in mean annual soil temperature(MAST)throughout the entire soil profile.From 2015 to 2023,MAST in the upper 200 cm rose from sub-zero(−0.30 to−0.49℃)to consistently above 0℃(0.07 to 1.08℃).Concurrently,maximum daily soil temperatures in deeper layers(200–300 cm)became positive,indicating thaw propagation into the relict permafrost.This warming coincided with a marked increase in unfrozen soil moisture,particularly within the expanding talik.The rapid,non-linear deepening of the talik,far exceeding rates attributable to conductive heat transfer alone,was driven by a strong convective mechanism(Rayleigh-Darcy instability).This advective process was triggered when the soil profile became fully saturated,a condition resulting from the convergence of intensified rainfall and enhanced water retention linked to decadal vegetation greening.Intriguingly,despite the accelerated subsurface warming,the annual amplitude of ground surface temperature decreased from 29.0±2.8℃ to 24.5±3.6℃ following talik formation,likely due to the buffering effect of increased vegetation cover,which modified the surface energy balance.Our results demonstrate that climatic warming and wetting can initiate a cascade of internal feedbacks,propelling marginal permafrost beyond an abrupt tipping point.These findings emphasize the acute vulnerability of marginal permafrost and highlight the urgent necessity for sustained monitoring to assess ecosystem stability and quantify associated greenhouse gas emissions.展开更多
基金supported by National Natural Science Foundation of China(12374358,91950207)Guangdong Basic and Applied Basic Research Foundation(2024A1515010420).
文摘Glucose molecules are of great significance being one of the most important molecules in metabolic chain.However,due to the small Raman scattering cross-section and weak/non-adsorption on bare metals,accurately obtaining their"fingerprint information"remains a huge obstacle.Herein,we developed a tip-enhanced Raman scattering(TERS)technique to address this challenge.Adopting an optical fiber radial vector mode internally illuminates the plasmonic fiber tip to effectively suppress the background noise while generating a strong electric-field enhanced tip hotspot.Furthermore,the tip hotspot approaching the glucose molecules was manipulated via the shear-force feedback to provide more freedom for selecting substrates.Consequently,our TERS technique achieves the visualization of all Raman modes of glucose molecules within spectral window of 400-3200 cm^(-1),which is not achievable through the far-field/surface-enhanced Raman,or the existing TERS techniques.Our TERS technique offers a powerful tool for accurately identifying Raman scattering of molecules,paving the way for biomolecular analysis.
基金The National Natural Science Foundation of China(No.52008100,52178317)the Natural Science Foundation of Jiangsu Province(No.BK20200400)+1 种基金China Postdoctoral Science Foundation(No.2022M723534)the Natural Science Foundation of Jiangsu Higher Education Institutions of China(No.23KJA560005).
文摘Postgrouting at the pile tip enhances the performance of cast-in-place piles.To clarify the performance of tip and side resistances,this study analyzed static load test data from two test piles before and after grouting.Mechanisms underlying an improvement in tip resistance and the influence of postgrouting on side resistance were investigated via theoretical analysis.Finally,a design method for tip resistance control via settlement was proposed.Results indicate that the ultimate bearing capacity of piles increases after grouting compared to before,underscoring the importance of tip grouting in gravelly soils and its profound impact on load transmission in pile foundations.Postgrouting at the pile tip enhances the strength as well as initial stiffness of the bearing stratum,ultimately elevating the overall pile foundation-bearing capacity.Additionally,tip grouting helps in strengthening over-all side resistance,especially around the pile tip.The grouting procedure has an impact on the soil’s arching effect at the pile tip;the extent of the arching effect and an increase in horizontal tension close to the pile tip are positively correlated with the effectiveness of grouting reinforcement.The design method for tip resistance control via settlement based on measured data statistics was validated using engineering examples,and the method has a practical reference value.
基金supported by the National Natural Science Foundation of China(Grant No.52206107)the National Key R&D Program of China(Grant No.2023YFE0120200)。
文摘Precise control and measurement of nanoparticles using low-power optical tweezers are pivotal for advancing single-particle analysis,nanoscale sensing,and energy transport research.In this work,we present the tipassisted nanoparticle capture system that simultaneously achieves localized temperature probing and nanoparticle trapping,significantly lowering the required laser power input.Unlike traditional metal-tip plasmonic techniques that predominantly rely on intense electric field gradients,our approach employs a silicon nanotip under resonant laser excitation,uniquely integrating optical forces,thermophoretic forces,and interatomic interactions for stable nanoparticle confinement.This synergistic collaboration mechanism enables approximately a 42%reduction in laser power density compared to conventional bowtie nanoaperture methods.This experimental method achieved direct and simultaneous Raman-based measurements of localized thermal dynamics,providing new insights into nanoscale thermodynamics during optical trapping.Additionally,the silicon nanotip demonstrates reduced thermal transport due to its confined nanoscale geometry,aligning closely with our theoretical predictions.Our integrated strategy of efficient nanoparticle manipulation coupled with precise thermal probing not only enhances overall energy efficiency but also broadens the scope of potential applications in cutting-edge nanoscience and nanotechnology.
基金supported by the Shenzhen Science and Technology Program(JCYJ20230808105111022,JCYJ20220818095806013)Natural Science Foundation of Guangdong(2023A1515012267)+1 种基金the National Natural Science Foundation of China(22178223)the Royal Society/NSFC cost share program(IEC\NSFC\223372).
文摘Low-electrode capacitive deionization(FCDI)is an emerging desalination technology with great potential for removal and/or recycling ions from a range of waters.However,it still suffers from inefficient charge transfer and ion transport kinetics due to weak turbulence and low electric intensity in flow electrodes,both restricted by the current collectors.Herein,a new tip-array current collector(designated as T-CC)was developed to replace the conventional planar current collectors,which intensifies both the charge transfer and ion transport significantly.The effects of tip arrays on flow and electric fields were studied by both computational simulations and electrochemical impedance spectroscopy,which revealed the reduction of ion transport barrier,charge transport barrier and internal resistance.With the voltage increased from 1.0 to 1.5 and 2.0 V,the T-CC-based FCDI system(T-FCDI)exhibited average salt removal rates(ASRR)of 0.18,0.50,and 0.89μmol cm^(-2) min^(-1),respectively,which are 1.82,2.65,and 2.48 folds higher than that of the conventional serpentine current collectors,and 1.48,1.67,and 1.49 folds higher than that of the planar current collectors.Meanwhile,with the solid content in flow electrodes increased from 1 to 5 wt%,the ASRR for T-FCDI increased from 0.29 to 0.50μmol cm^(-2) min^(-1),which are 1.70 and 1.67 folds higher than that of the planar current collectors.Additionally,a salt removal efficiency of 99.89%was achieved with T-FCDI and the charge efficiency remained above 95%after 24 h of operation,thus showing its superior long-term stability.
文摘Background: Reconstruction of Nasal Tip Columella (NTC) subunits is one of the most challenging aspects in functional aesthetic rhinoplasty. Moreover, racial variation for Asian nose rhinoplasty could even demand sophistication of tip and columella strut graft infrastructure enhancement. Various autogenous graft options such as 6th costal cartilage, septal cartilage and conchal cartilage are very commonly considered whilst the 10th costal cartilage is scarcely reported. Objective and Method: The purpose of this manuscript is to illustrate the detailed operative steps to harvest the 10th costal cartilage for infrastructural grafting at NTC subunits by a case illustration. The pros and cons of different cartilage options will be discussed, particularly its application in cleft nose rhinoplasty in Chinese patient. We have adopted the 10th rib as the key option for NTC reconstruction in 11 cases of Chinese cleft secondary rhinoplasty since 2019 and have achieved good and stable results without complications. Conclusion: The 10th costal cartilage is one of the best options in Nasal Tip Columella subunits reconstruction, particularly in complex cleft nose or failure revision aesthetic rhinoplasty cases, due to its safety of harvesting, and the sufficient quality and quantity of grafting materials it provides for simultaneous adjunctive augmentation purpose.
基金supported by the National Natural Science Foundation of China(32071749)。
文摘Root tips are the main components of absorptive fine roots,but their seasonal dynamics and relationship to environmental factors remain unclear due to the difficulties in methodology.In this study,we explored the temporal patterns of root-tip production and mortality in monoculture plantations of five temperate tree species at a common site in northeastern China,and identified the general environmental controls on such processes.We made monthly in-situ assessments of root tip length(RTL)production and mortality in two hardwood and three coniferous species with a minirhizotron(MR)method during the growing seasons of 2008 and 2009.Air temperature,rainfall,soil temperature and water content at 10 cm depth were determined concurrently.RTL production in all species exhibited consistent peaks in summer(June–August)in two growing seasons.RTL mortality showed substantial interannual and interspecific variability,with peaks in autumn and winter in 2008,but various patterns in 2009.RTL production positively correlated with monthly soil and air temperature across all species,and with monthly rainfall in three coniferous species.However,there was no significant correlation between RTL production and soil water content.By contrast,RTL mortality was weakly related to environmental factors,showing positive correlations with soil temperature in Korean spruce,and with rainfall in Korean pine and Korean spruce.Our findings suggest that the seasonal patterns of RTL production are convergent across the five temperate tree species due to the overlapped distribution of heat and rainfall,which can conduce roots to maximizing the acquisition of nutrient resources in the soil.
基金supported by the National Natural Science Foundation of China(Nos.52405088 and 92360306)the Postdoctoral Fellowship Program of CPSF,China(No.GZC20241446)+2 种基金the Natural Science Basic Research Program of Shaanxi,China(No.2024JC-YBMS-402)the Fundamental Research Funds for the Central Universities,CHD(No.300102254102)the Foundation of Beilin District,China(No.GX2455)。
文摘Anti-aliasing spectrum analysis is essential for rotor blade condition monitoring based on Blade Tip Timing(BTT).The Multiple Signal Classification(MUSIC)algorithm,which exploits the orthogonality between signal and noise subspaces,has been successfully applied for this purpose.However,conventional subspace selection methods relying on fixed thresholds are sensitive to variations in large eigenvalues.Furthermore,the complex disturbances during rotor operation and measurement complicate the identification of blade vibration characteristics.To overcome these challenges,this paper proposes Adaptive Subspace Separation(ASS)and Local Spectral Centroid(LSC)methods to improve the adaptability of subspace selection and the stability of frequency identification,respectively.The impacts of overestimating and underestimating the subspace dimensions on MUSIC's performance are derived mathematically.Simulation and experiments demonstrate the effectiveness of proposed approaches:ASS offers more accurate and stable subspace dimension selection and tracking,while LSC reduces the standard deviation of estimated frequencies by 30 percent.
基金supported by the National Key Research and Development Program of China(2023YFB4605100)the Shaanxi Provincial Key Research and Development Program(2019ZDLGY01-09 and 2021ZDLGY10-02)the State Key Laboratory of Solidification Processing(SKLSP202203).
文摘The fabrication of nanostructures beyond the diffraction limit has been the focus of nanotechnology research.Scanning probe microscopy(SPM)has attracted the attention of researchers for the detection and manufacture of nanostructures.Here,a nanosecond laser irradiated a cantilevered scanning nearfield optical microscopy(SNOM)tip and directly wrote subwavelength nanostructures on Au nano-film,without the assistance of a mask or vacuum atmosphere.This method was stable and reproducible for long-term use.The in situ morphology detection was conducted after the writing process by atomic force microscope(AFM).A feature linewidth of approximately 83.6 nm(<k/6)was confirmed using scanning electron microscopy(SEM).Linewidth of(167.8±6.6)nm was reproduced stably.Theoretical calculations revealed that the elliptical heat distribution under the SNOM tip generated different linewidths when the tip scanned vertically and horizontally.It also interpreted the influential mechanism of single-pulse energy.The simulated linewidths were consistent with the fabricated linewidths.According to the elemental analysis by energy dispersive spectrometer(EDS),the mechanism of this method can be interpreted asmelting of the Au nano-film instead of oxidation.Owing to its high positioning,machining accuracy,and instantaneous energy,this technology is considered convenient and economical for nanostructure fabrication and is proposed to be applied in nanolithography on multiple materials in the future.
基金supported by the Key Program of National Natural Science Foundation of China(No.92160203)National Natural Science Foundation of China(No.92360306).
文摘The existence of the aeroengine casing,limited monitoring points,and multi-fault characteristics make obtaining the rotor’s vibration transmission characteristics challenging,resulting in difficulties accurately identifying the rotor unbalance.This paper utilizes a high-frequency composite sensor to monitor the engine’s blade tip clearance(BTC)and extracts unbalanced information from BTC signals for rotor dynamic balancing,while avoiding the need for the once per revolution(OPR)sensor.First,the vibration characteristics of the rotor-blade system under multi-fault conditions are investigated.Then,based on BTC measurement,a none OPR method and an unbalance identification method are proposed,in which the radial vibration of the blade tip in the BTC signals at different speeds is extracted and operated in the time domain to obtain the rotor unbalanced vibration,the signal is reconstructed,and cross-correlation analysis is used to accurately identify the magnitude and phase of the unbalanced signal.Finally,a rotor test bench is utilized for experimental verification.The results reveal that the dynamic balancing method based on the BTC signal can more precisely identify the rotor unbalance than the traditional rotor dynamic balancing method.The application of this technique will effectively improve engine health management and fault prediction.
基金Supported by the Shihwa Medical Center Research Fund.
文摘BACKGROUND Despite advancements,endoscopic retrograde cholangiopancreatography(ERCP)poses challenges,including the risk of post-ERCP pancreatitis and difficulty of biliary cannulation.AIM To compare dome and tapered tip sphincterotomes,focusing on their efficacy in achieving successful biliary cannulation and reducing the incidence of post-ERCP pancreatitis.METHODS In this prospective,single-blind,randomized pilot study conducted at Inha Uni-versity Hospital,85 patients undergoing ERCP were equally divided into dome and tapered tip sphincterotome groups.The co-primary outcomes were the success rate of selective biliary cannulation and incidence of post-ERCP pancre-atitis.The secondary outcomes included biliary cannulation time,number of unintended pancreatic duct access events,and total procedure time.RESULTS The success rates of selective biliary cannulation were 74.4%and 85.7%in the dome and tapered tip groups,respectively,with no significant difference(P=0.20).Similarly,the incidence of post-ERCP pancreatitis did not differ significantly between the groups(5 cases in the tapered tip group vs 6 in the dome tip group,P=0.72).However,difficult cannulation was significantly more common in the dome tip group than in the tapered tip group(P=0.05).Selective biliary cannula-tion time emerged as a significant predictor of post-ERCP pancreatitis(multivariate odds ratio=9.33,95%confi-dence interval:1.31-66.44,P=0.03).CONCLUSION This study indicated that the sphincterotome tip type does not markedly affect biliary cannulation success or post-ERCP pancreatitis rates.However,cannulation duration is a key risk factor for post-ERCP pancreatitis.These findings provide preliminary insights that highlight the importance of refining ERCP practices,including sphinc-terotome selection,while underscoring the need for larger multicenter studies to improve procedure time and patient safety.
基金Project supported by the National Natural Science Foundation of China (Grant No. 12104502)the Natural Science Foundation of Sichuan Province (Grant No. 2023YFG0308)the Fundamental Research Funds for the Central Universities (Grant No. 24CAFUC03057)。
文摘The Stokes–Einstein–Debye(SED) relation in TIP5P water is tested with the original formula and its variants within the temperature range 240–390 K. The results indicate that although the variants explicitly break down, the original SED relation is almost valid. Compared with the Stokes–Einstein relation, no explicit decoupling is observed in translational and rotational motion. Variation of the effective hydrodynamic radius is critical to testing the validity of the SED relation.
基金funded by the Science and Technology program of Gansu Province(Grant No.23ZDFA017)Longyuan Young Talents(D.Luo),Western Young Scholars Project of the Chinese Academy of Sciences(D.Luo)National Natural Science Foundation of China(U2243214).
文摘Permafrost,a critical component of Earth’s climate system,is increasingly subject to abrupt thaw events,which jeopardize infrastructure,reshape landforms,alter hydrological regimes,and disrupt ecosystems,thereby posing substantial threats to global sustainability.However,the underlying mechanisms that trigger these abrupt transitions remain incompletely understood.Here,we present decade-long in-situ observations from HRQ1,a marginal permafrost site in the Headwater Area of the Yellow River,northeastern Qinghai-Xizang Plateau.These data reveal the formation and growth of a talik,indicative of a permafrost tipping point.Absent before 2017,the talik subsequently formed and progressively deepened,extending to the maximum observation depth of 300 cm by 2024.The transition from perennially frozen to thawed conditions was accompanied by a substantial increase in mean annual soil temperature(MAST)throughout the entire soil profile.From 2015 to 2023,MAST in the upper 200 cm rose from sub-zero(−0.30 to−0.49℃)to consistently above 0℃(0.07 to 1.08℃).Concurrently,maximum daily soil temperatures in deeper layers(200–300 cm)became positive,indicating thaw propagation into the relict permafrost.This warming coincided with a marked increase in unfrozen soil moisture,particularly within the expanding talik.The rapid,non-linear deepening of the talik,far exceeding rates attributable to conductive heat transfer alone,was driven by a strong convective mechanism(Rayleigh-Darcy instability).This advective process was triggered when the soil profile became fully saturated,a condition resulting from the convergence of intensified rainfall and enhanced water retention linked to decadal vegetation greening.Intriguingly,despite the accelerated subsurface warming,the annual amplitude of ground surface temperature decreased from 29.0±2.8℃ to 24.5±3.6℃ following talik formation,likely due to the buffering effect of increased vegetation cover,which modified the surface energy balance.Our results demonstrate that climatic warming and wetting can initiate a cascade of internal feedbacks,propelling marginal permafrost beyond an abrupt tipping point.These findings emphasize the acute vulnerability of marginal permafrost and highlight the urgent necessity for sustained monitoring to assess ecosystem stability and quantify associated greenhouse gas emissions.
