Silicon carbide(SiC)is widely used in fields such as new energy,military radar,and aerospace due to its outstanding physical and chemical properties.The surface micro-grooves of SiC can enhance the performance of micr...Silicon carbide(SiC)is widely used in fields such as new energy,military radar,and aerospace due to its outstanding physical and chemical properties.The surface micro-grooves of SiC can enhance the performance of micro-electromechanical systems,micro-sensors,and field-effect transistors.However,SiC,being a brittle and hard material,poses challenges for traditional machining methods like micro-groove machining and chemical etching,including subsurface damage,short tool life,and low processing efficiency.This paper investigates the processing characteristics of femtosecond laser machining of SiC micro-grooves and compares them with those of single-crystal Si.The results indicate that femtosecond laser ablation of SiC primarily leads to melting and vaporization,forming modification,melted,and ablation areas in the affected area.Femtosecond laser processing of SiC micro-grooves involves three processes:heat absorption and melting,vaporization,and chipping,with vaporization as the primary material removal mechanism.The depth and width of SiC micro-grooves are positively correlated with pulse energy(E_(p)),pulse overlap rate(PO),and number of passes(N_(pass)).The bottom roughness of the micro-grooves is positively correlated with E_(p),negatively correlated with PO,and less affected by changes in the N_(pass).These findings further elucidate the material removal and micro-groove formation mechanisms of SiC under femtosecond laser irradiation,providing theoretical insights for high-quality and high-efficiency processing of SiC micro-grooves.展开更多
This study investigates the width of the secondary eyewall(SE)immediately following its formation in tropical cyclones with surface environmental winds aligned and counter-aligned with environmental vertical wind shea...This study investigates the width of the secondary eyewall(SE)immediately following its formation in tropical cyclones with surface environmental winds aligned and counter-aligned with environmental vertical wind shear(VWS),using idealized numerical experiments.Results reveal that the SE develops greater radial extent when surface winds align with VWS compared to counter-aligned conditions.In alignment configurations,shear-enhanced surface winds on the right flank amplify surface enthalpy fluxes,thereby elevating boundary-layer entropy within the downshear outer-core region.Subsequently,more vigorous outer rainbands develop,inducing marked acceleration of tangential winds in the outer core preceding SE formation.The resultant radial expansion of supergradient winds near the boundary-layer top triggers widespread convective activity immediately beyond the inner core.Progressive axisymmetrization of this convective forcing ultimately generates an expansive SE structure.展开更多
Microwave ablation(MWA)is a minimally invasive technique for treating hepatic tumors,necessitating precise monitoring to ensure treatment efficacy and minimize damage to surrounding tissues.This study explores the pot...Microwave ablation(MWA)is a minimally invasive technique for treating hepatic tumors,necessitating precise monitoring to ensure treatment efficacy and minimize damage to surrounding tissues.This study explores the potential of photoacoustic imaging(PAI)in monitoring MWA by examining ex vivo porcine liver tissues.In this study,a comprehensive analysis of photoacoustic signals was performed to compare the main lobe width(MLW)between ablated and normal regions in porcine liver tissue.Histological staining with succinate dehydrogenase(SDH)and shear wave elastography(SWE)were employed to validate the changes in tissue elasticity after ablation.The analysis demonstrated a notable reduction in the MLW of the average A-lines in ablated tissues compared to nonablated regions(p<0.01).This reduction,attributed to increased tissue density and enhanced elasticity,indicates accelerated sound propagation in thermally ablated areas,which then serves as a critical parameter for mapping tissue characteristics.The reconstruction of the MLW distribution successfully delineated the ablated regions,and was consistent with the results of SDH staining and SWE.In addition,MLW-based imaging exhibited higher spatial resolution compared to SWE.Incorporating MLW analysis into PAI may be a promising strategy to improve the accuracy and effectiveness of MWA monitoring in clinical settings.展开更多
Investigating the detonation reaction zone structures of high explosives is significant for understanding detonation reaction mechanism.This study employed an integrated approach combining machine learning prediction,...Investigating the detonation reaction zone structures of high explosives is significant for understanding detonation reaction mechanism.This study employed an integrated approach combining machine learning prediction,theoretical calculation,and experimental characterization to determine the detonation reaction zone width of CL-20-based aluminized explosive.In this study,the detonation reaction zone refers to the reaction zone between the von Neumann(VN)peak and sonic point,which usually means the so-called detonation driving zone(DDZ).For the machine learning prediction,an ensemble model integrating Random Forest and Support Vector Regression was developed to predict the reaction zone width using a dataset of 19 publicly available samples.For the theoretical calculation,the Wood-Kirkwood(W-K)detonation theory model was utilized to implement numerical calculation of the reaction zone structures,incorporating chemical reaction kinetics to describe the detonation reaction progress.In experimental characterization,the Photon Doppler Velocimetry(PDV)was applied with LiF as the optical window to measure the particle velocity profile of detonation products and derive the reaction zone width.The results indicate that the reaction zone width values are 0.25 mm,0.28 mm,and 0.26 mm obtained from machine learning prediction,theoretical calculation,and experimental characterization,respectively.The corresponding velocities at the Chapman-Jouguet(CJ)point are 1,938 m/s,2,047 m/s,and 1,982 m/s,respectively.The maximum relative deviation in reaction zone width among three methods is approximately 7.7%,while that for CJ particle velocity is approximately 3.3%.These results from all three methods agree well within engineering error.This validates the effectiveness of integrating machine learning prediction,theoretical calculation and advanced experimental techniques for studying the detonation reaction zone structures of high explosives.This research provides insights into the detonation reaction mechanism and reaction zone characteristics of CL-20-based aluminized explosive.展开更多
This work describes an experimental investigation into the influence of geometric micro-groove texture patterns on the tribological performance of stainless steel.Five geometries were studied:one with untextured and f...This work describes an experimental investigation into the influence of geometric micro-groove texture patterns on the tribological performance of stainless steel.Five geometries were studied:one with untextured and four with micro-groove textured making parallel,triangular,square and hexagonal patterns.The micro-groove textures were produced using an MFT-20laser system as well as a two-step laser surface texturing(LST)process.Tribological performance was measured using a pin-on-disk tribometer.The investigation showed that the two-step LST process could fabricate high-precision micro-grooves.The experimental data indicated that the micro-groove textured surfaces achieved the lower frictional coefficients than the untextured surface and the geometric patterns had significantly affected the tribological properties of samples in both lubricated and unlubricated states.The results were analyzed from the lubricant supplying and fluid dynamic pressure effect under lubricated conditions as well as abrasive capture and remove under dry friction conditions.展开更多
The collapse of thin-walled micro-grooved heat pipes is a common phenomenon in the tube flattening process, which seriously influences the heat transfer performance and appearance of heat pipe. At present, there is no...The collapse of thin-walled micro-grooved heat pipes is a common phenomenon in the tube flattening process, which seriously influences the heat transfer performance and appearance of heat pipe. At present, there is no other better method to solve this problem. A new method by heating the heat pipe is proposed to eliminate the collapse during the flattening process. The effectiveness of the proposed method is investigated through a theoretical model, a finite element（FE） analysis, and experimental method. Firstly, A theoretical model based on a deformation model of six plastic hinges and the Antoine equation of the working fluid is established to analyze the collapse of thin walls at different temperatures. Then, the FE simulation and experiments of flattening process at different temperatures are carried out and compared with theoretical model. Finally, the FE model is followed to study the loads of the plates at different temperatures and heights of flattened heat pipes. The results of the theoretical model conform to those of the FE simulation and experiments in the flattened zone. The collapse occurs at room temperature. As the temperature increases, the collapse decreases and finally disappears at approximately 130 ℃ for various heights of flattened heat pipes. The loads of the moving plate increase as the temperature increases. Thus, the reasonable temperature for eliminating the collapse and reducing the load is approximately 130℃. The advantage of the proposed method is that the collapse is reduced or eliminated by means of the thermal deformation characteristic of heat pipe itself instead of by external support. As a result, the heat transfer efficiency of heat pipe is raised.展开更多
Heat pipe is always bent in the typical application of electronic heat dissipation at high heat flux,which greatly affects its heat transfer performance. The capillary limit of heat transport in the bent micro-grooved...Heat pipe is always bent in the typical application of electronic heat dissipation at high heat flux,which greatly affects its heat transfer performance. The capillary limit of heat transport in the bent micro-grooved heat pipes was analyzed in the vapor pressure drop,the liquid pressure drop and the interaction of the vapor with wick fluid. The bent heat pipes were fabricated and tested from the bending angle,the bending position and the bending radius. The results show that temperature difference and thermal resistance increase while the heat transfer capacity of the heat pipe decreases,with the increase of the bending angles and the bending position closer to the vapor section. However,the effects of bending radius can be ignored. The result agrees well with the predicted equations.展开更多
We have investigated experimentally the process of a droplet impact on a regular micro-grooved surface. The target surfaces are patterned such that micro-scale spokes radiate from the center, concentric circles, and p...We have investigated experimentally the process of a droplet impact on a regular micro-grooved surface. The target surfaces are patterned such that micro-scale spokes radiate from the center, concentric circles, and parallel lines on the polishing copper plate, using Quasi-LIGA molding technology. The dynamic behavior of water droplets impacting on these structured surfaces is examined using a high-speed camera, including the drop impact processes, the maximum spreading diameters, and the lengths and numbers of fingers at different values of Weber number. Experimental results validate that the spreading processes are arrested on all target surfaces at low velocity. Also, the experimental results at higher impact velocity demonstrate that the spreading process is conducted on the surface parallel to the micro-grooves, but is arrested in the direction perpendicular to the micro-grooves. Besides, the lengths of fingers increase observably, even when they are ejected out as tiny droplets along the groove direction, at the same time the drop recoil velocity is reduced by micro-grooves which are parallel to the spreading direction, but not by micro-grooves which are vertical to the spreading direction.展开更多
A novel optical fiber sensor with a U-shaped micro-groove structure ablated by femtosecond laser on single-mode fiber for measuring air relative humidity(RH)is reported in this paper.In order to improve the accuracy o...A novel optical fiber sensor with a U-shaped micro-groove structure ablated by femtosecond laser on single-mode fiber for measuring air relative humidity(RH)is reported in this paper.In order to improve the accuracy of sensor,a graphene oxide(GO)/polyvinyl alcohol(PVA)composite film is coated on the surface of micro-groove structure.In the U-shaped micro-groove structure,the remaining core and micro-cavity in the micro-groove make up two major optical propagation paths,forming a Mach-Zehnder interferometer(MZI).The sensor has a good linear response within the RH range of 30%—85%,and the maximum sensitivity can reach 0.638 1 nm/%RH.The effect of temperature on the overall performance of the humidity sensor is also investigated.As a new type of all-fiber device,the sensor shows excellent sensitivity and stability.展开更多
A magnetic abrasive finishing process using an alternating magnetic field is proposed for the finishing of complex surfaces.In an alternating field,the periodic changes in current will cause the magnetic cluster used ...A magnetic abrasive finishing process using an alternating magnetic field is proposed for the finishing of complex surfaces.In an alternating field,the periodic changes in current will cause the magnetic cluster used as a magnetic brush to fluctuate,which will not only continuously replace the abrasive particles in contact with the workpiece,but also periodically adjust the shape of the magnetic cluster to better fit the surface of the workpiece.In this paper,the influence of a combination of alternating and static magnetic fields on the magnetic field in the finishing area is analyzed.The feasibility of this process for finishing micro-grooves is investigated.Simulations and experimental measurements show that the combination of alternating and static magnetic fields can retain the advantages of the alternating field while increasing the magnetic flux density in the finishing area.The experimental results show that the process is feasible for finishing micro-grooves,with an excellent deburring effect on the groove edges.展开更多
A growing interest is given to the hydrodynamic lubricated friction pair with surface textured. Because of its relatively simple processing methods and low manufacturing costs,micro-groove has become the most valuable...A growing interest is given to the hydrodynamic lubricated friction pair with surface textured. Because of its relatively simple processing methods and low manufacturing costs,micro-groove has become the most valuable form of surface texture,and definitely has broad application prospects in mechanical engineering. Based on numerical simulation,the present study aims to examine the effects of surface forms and cross-section types of micro-groove on the hydrodynamic lubrication performance,and to find out the optimal structural parameter for designing logical micro-grooves. Different surface form and cross-section types are designed to maximize the texture hydrodynamic effect. The average pressure of such microgrooved surface is evaluated in detail,and the variation trends with changes of the length of micro-groove,lp,or the depth,hp,are discussed. The theoretical results show that micro-grooves with rational design contribute to the improvement of hydrodynamic lubrication performance of friction pair largely. For a specific micro-grooved friction pair,the optimal surface form and crosssection type make the lubrication performance best.展开更多
BACKGROUND Post-hepatectomy liver failure(PHLF)after liver resection is one of the main complications causing postoperative death in patients with hepatocellular carcinoma(HCC).It is crucial to help clinicians identif...BACKGROUND Post-hepatectomy liver failure(PHLF)after liver resection is one of the main complications causing postoperative death in patients with hepatocellular carcinoma(HCC).It is crucial to help clinicians identify potential high-risk PHLF patients as early as possible through preoperative evaluation.AIM To identify risk factors for PHLF and develop a prediction model.METHODS This study included 248 patients with HCC at The Second Affiliated Hospital of Air Force Medical University between January 2014 and December 2023;these patients were divided into a training group(n=164)and a validation group(n=84)via random sampling.The independent variables for the occurrence of PHLF were identified by univariate and multivariate analyses and visualized as nomograms.Ultimately,comparisons were made with traditional models via receiver operating characteristic(ROC)curves,calibration curves,and decision curve analysis(DCA).RESULTS In this study,portal vein width[odds ratio(OR)=1.603,95%CI:1.288-1.994,P≤0.001],the preoperative neutrophil-to-lymphocyte ratio(NLR)(OR=1.495,95%CI:1.126-1.984,P=0.005),and the albumin-bilirubin(ALBI)score(OR=8.868,95%CI:2.144-36.678,P=0.003)were independent risk factors for PHLF.A nomogram prediction model was developed using these factors.ROC and DCA analyses revealed that the predictive efficacy and clinical value of this model were better than those of traditional models.CONCLUSION A new Nomogram model for predicting PHLF in HCC patients was successfully established based on portal vein width,the NLR,and the ALBI score,which outperforms the traditional model.展开更多
BACKGROUND As red blood cell distribution width(RDW)and albumin have been shown to be independent predictors of mortality from various diseases,this study aimed to investigate the effect of the RDW to albumin ratio(RA...BACKGROUND As red blood cell distribution width(RDW)and albumin have been shown to be independent predictors of mortality from various diseases,this study aimed to investigate the effect of the RDW to albumin ratio(RA)as an independent predictor of the prognosis of patients admitted to the coronary care unit(CCU).AIM To use the RDW and albumin level to predict the prognosis of patients in the CCU.METHODS Data were obtained from the Medical Information Mart Intensive Care III database.The primary outcome was 365-day all-cause mortality,whereas the secondary outcomes were 30-and 90-day all-cause mortality,hospital length of stay(LOS),and CCU LOS.Cox proportional hazards regression model,propen-sity score matching,and receiver operating characteristic curve analyses were used.RESULTS The hazard ratio(95%confidence interval)of the upper tertile(RA>4.66)was 1.62(1.29 to 2.03)when compared with the reference(RA<3.84)in 365-day all-cause mortality.This trend persisted after adjusting for demographic and clinical variables in the propensity score-matching analysis.Similar trends were observed for the secondary outcomes of hospital and CCU LOS.Receiver operating characteristic curve analysis was performed by combining the RA and sequential organ failure assessment(SOFA)scores,and the C-statistic was higher than that of the SOFA scores(0.733 vs 0.702,P<0.001).CONCLUSION RA is an independent prognostic factor in patients admitted to the CCU.RA combined with the SOFA score can improve the predictive ability of the SOFA score.However,our results should be verified in future prospective studies.展开更多
BACKGROUND Red blood cell distribution width(RDW)is associated with the development and progression of various diseases.AIM To explore the association between pretreatment RDW and short-term outcomes after laparoscopi...BACKGROUND Red blood cell distribution width(RDW)is associated with the development and progression of various diseases.AIM To explore the association between pretreatment RDW and short-term outcomes after laparoscopic pancreatoduodenectomy(LPD).METHODS A total of 804 consecutive patients who underwent LPD at our hospital between March 2017 and November 2021 were retrospectively analyzed.Correlations between pretreatment RDW and clinicopathological characteristics and short-term outcomes were investigated.RESULTS Patients with higher pretreatment RDW were older,had higher Eastern Cooperative Oncology Group scores and were associated with poorer short-term outcomes than those with normal RDW.High pretreatment RDW was an independent risk factor for postoperative complications(POCs)(hazard ratio=2.973,95%confidence interval:2.032-4.350,P<0.001)and severe POCs of grade IIIa or higher(hazard ratio=3.138,95%confidence interval:2.042-4.824,P<0.001)based on the Clavien-Dino classification system.Subgroup analysis showed that high pretreatment RDW was an independent risk factor for Clavien-Dino classi-fication grade IIIb or higher POCs,a comprehensive complication index score≥26.2,severe postoperative pancreatic fistula,severe bile leakage and severe hemorrhage.High pretreatment RDW was positively associated with the neutrophil-to-lymphocyte ratio and platelet-to-lymphocyte ratio and was negatively associated with albumin and the prognostic nutritional index.CONCLUSION Pretreatment RDW was a special parameter for patients who underwent LPD.It was associated with malnutrition,severe inflammatory status and poorer short-term outcomes.RDW could be a surrogate marker for nutritional and inflammatory status in identifying patients who were at high risk of developing POCs after LPD.展开更多
The minimal widths of three bounded subsets of the unit sphere associated to a unit vector in a normed linear space are studied,and three related geometric constants are introduced.New characterizations of inner produ...The minimal widths of three bounded subsets of the unit sphere associated to a unit vector in a normed linear space are studied,and three related geometric constants are introduced.New characterizations of inner product spaces are also presented.From the perspective of minimal width,strongε-symmetry of Birkhoff orthogonality is introduced,and its relation toε-symmetry of Birkhoff orthogonality is shown.Unlike most of the existing parameters of the underlying space,these new constants are full dimensional in nature.展开更多
The width of rice leaves determines the size of the photosynthetic area.Optimizing rice leaf width can improve the photosynthetic rate,thereby increasing rice yield.In this study,a genome-wide association study(GWAS)w...The width of rice leaves determines the size of the photosynthetic area.Optimizing rice leaf width can improve the photosynthetic rate,thereby increasing rice yield.In this study,a genome-wide association study(GWAS)was conducted by 225 rice germplasm resources to explore the genetic basis of rice flag leaf width(FLW).We identified nine QTLs associated with FLW(qFLWs),with phenotypic contribution rates ranging from 3.17%to 14.37%.Near-isogenic lines(NILs)were developed for fine-mapping of qFLW11,and the function of FLW11 was further verified.We narrowed down q FLW11 to an 87-kb interval,which contains five genes.展开更多
Intracranial aneurysm(IA)is a prevalent cerebrovascular disease associated with high mortality and disability rates upon rupture.The hemodynamics of IA,which are significantly influenced by geometric parameters,direct...Intracranial aneurysm(IA)is a prevalent cerebrovascular disease associated with high mortality and disability rates upon rupture.The hemodynamics of IA,which are significantly influenced by geometric parameters,directly impact its rupture.This study focuses on investigating the transient flow characteristics in saccular IA models fabricated using a water droplet-based method,specifically examining the influence of neck widths.Particle image velocimetry technique and numerical simulation were employed to investigate the dynamic evolution of flow structures within three IA models.The results reveal that neck width(W)has a substantial effect on flow characteristics in the neck region,subsequently impacting the deep flow inside the sac.Three distinct patterns were observed during flow evolution inside the sac:for W=2 mm,two vortices occur and then disappear with relatively low average flow velocity;for W=4 mm,enhanced effects of a high-speed jet result in periodic pulsatile flow velocity distribution while maintaining stable vortex core position;for W=6 mm,significant changes in flow velocity occur due to size expansion and intensity increase of vortices.These findings demonstrate that neck widths play a complex role in influencing transient flow characteristics within IAs.Overall,this research contributes to further understanding transient flow behaviors in IAs.展开更多
Accurate prediction of strip width is a key factor related to the quality of hot rolling manufacture.Firstly,based on strip width formation mechanism model within strip rolling process,an improved width mechanism calc...Accurate prediction of strip width is a key factor related to the quality of hot rolling manufacture.Firstly,based on strip width formation mechanism model within strip rolling process,an improved width mechanism calculation model is delineated for the optimization of process parameters via the particle swarm optimization algorithm.Subsequently,a hybrid strip width prediction model is proposed by effectively combining the respective advantages of the improved mechanism model and the data-driven model.In acknowledgment of prerequisite for positive error in strip width prediction,an adaptive width error compensation algorithm is proposed.Finally,comparative simulation experiments are designed on the actual rolling dataset after completing data cleaning and feature engineering.The experimental results show that the hybrid prediction model proposed has superior precision and robustness compared with the improved mechanism model and the other eight common data-driven models and satisfies the needs of practical applications.Moreover,the hybrid model can realize the complementary advantages of the mechanism model and the data-driven model,effectively alleviating the problems of difficult to improve the accuracy of the mechanism model and poor interpretability of the data-driven model,which bears significant practical implications for the research of strip width control.展开更多
To cater the need for real-time crack monitoring of infrastructural facilities,a CNN-regression model is proposed to directly estimate the crack properties from patches.RGB crack images and their corresponding masks o...To cater the need for real-time crack monitoring of infrastructural facilities,a CNN-regression model is proposed to directly estimate the crack properties from patches.RGB crack images and their corresponding masks obtained from a public dataset are cropped into patches of 256 square pixels that are classified with a pre-trained deep convolution neural network,the true positives are segmented,and crack properties are extracted using two different methods.The first method is primarily based on active contour models and level-set segmentation and the second method consists of the domain adaptation of a mathematical morphology-based method known as FIL-FINDER.A statistical test has been performed for the comparison of the stated methods and a database prepared with the more suitable method.An advanced convolution neural network-based multi-output regression model has been proposed which was trained with the prepared database and validated with the held-out dataset for the prediction of crack-length,crack-width,and width-uncertainty directly from input image patches.The pro-posed model has been tested on crack patches collected from different locations.Huber loss has been used to ensure the robustness of the proposed model selected from a set of 288 different variations of it.Additionally,an ablation study has been conducted on the top 3 models that demonstrated the influence of each network component on the pre-diction results.Finally,the best performing model HHc-X among the top 3 has been proposed that predicted crack properties which are in close agreement to the ground truths in the test data.展开更多
基金Supported by National Natural Science Foundation of China(Grant No.52122510)the School-enterprise Cooperation Project Funded by Dongguan Strong Laser Advanced Equipment Co.,Ltd.(Grant No.21HK0214)。
文摘Silicon carbide(SiC)is widely used in fields such as new energy,military radar,and aerospace due to its outstanding physical and chemical properties.The surface micro-grooves of SiC can enhance the performance of micro-electromechanical systems,micro-sensors,and field-effect transistors.However,SiC,being a brittle and hard material,poses challenges for traditional machining methods like micro-groove machining and chemical etching,including subsurface damage,short tool life,and low processing efficiency.This paper investigates the processing characteristics of femtosecond laser machining of SiC micro-grooves and compares them with those of single-crystal Si.The results indicate that femtosecond laser ablation of SiC primarily leads to melting and vaporization,forming modification,melted,and ablation areas in the affected area.Femtosecond laser processing of SiC micro-grooves involves three processes:heat absorption and melting,vaporization,and chipping,with vaporization as the primary material removal mechanism.The depth and width of SiC micro-grooves are positively correlated with pulse energy(E_(p)),pulse overlap rate(PO),and number of passes(N_(pass)).The bottom roughness of the micro-grooves is positively correlated with E_(p),negatively correlated with PO,and less affected by changes in the N_(pass).These findings further elucidate the material removal and micro-groove formation mechanisms of SiC under femtosecond laser irradiation,providing theoretical insights for high-quality and high-efficiency processing of SiC micro-grooves.
基金jointly supported by the National Natural Science Foundation of China[grant numbers U2342202,42175005,and 42175016]the Qing Lan Project[grant number R2023Q06]。
文摘This study investigates the width of the secondary eyewall(SE)immediately following its formation in tropical cyclones with surface environmental winds aligned and counter-aligned with environmental vertical wind shear(VWS),using idealized numerical experiments.Results reveal that the SE develops greater radial extent when surface winds align with VWS compared to counter-aligned conditions.In alignment configurations,shear-enhanced surface winds on the right flank amplify surface enthalpy fluxes,thereby elevating boundary-layer entropy within the downshear outer-core region.Subsequently,more vigorous outer rainbands develop,inducing marked acceleration of tangential winds in the outer core preceding SE formation.The resultant radial expansion of supergradient winds near the boundary-layer top triggers widespread convective activity immediately beyond the inner core.Progressive axisymmetrization of this convective forcing ultimately generates an expansive SE structure.
基金supported by the National Natural Science Foundation of China(82427808,61875085)the Jiangsu Provincial University Natural Science Foundation(25KJB413004)+1 种基金the Nanjing Health Science and Technology Development Foundation(ZKX24043)the Fundamental Research Funds for the Central Universities(NJ2024029).
文摘Microwave ablation(MWA)is a minimally invasive technique for treating hepatic tumors,necessitating precise monitoring to ensure treatment efficacy and minimize damage to surrounding tissues.This study explores the potential of photoacoustic imaging(PAI)in monitoring MWA by examining ex vivo porcine liver tissues.In this study,a comprehensive analysis of photoacoustic signals was performed to compare the main lobe width(MLW)between ablated and normal regions in porcine liver tissue.Histological staining with succinate dehydrogenase(SDH)and shear wave elastography(SWE)were employed to validate the changes in tissue elasticity after ablation.The analysis demonstrated a notable reduction in the MLW of the average A-lines in ablated tissues compared to nonablated regions(p<0.01).This reduction,attributed to increased tissue density and enhanced elasticity,indicates accelerated sound propagation in thermally ablated areas,which then serves as a critical parameter for mapping tissue characteristics.The reconstruction of the MLW distribution successfully delineated the ablated regions,and was consistent with the results of SDH staining and SWE.In addition,MLW-based imaging exhibited higher spatial resolution compared to SWE.Incorporating MLW analysis into PAI may be a promising strategy to improve the accuracy and effectiveness of MWA monitoring in clinical settings.
文摘Investigating the detonation reaction zone structures of high explosives is significant for understanding detonation reaction mechanism.This study employed an integrated approach combining machine learning prediction,theoretical calculation,and experimental characterization to determine the detonation reaction zone width of CL-20-based aluminized explosive.In this study,the detonation reaction zone refers to the reaction zone between the von Neumann(VN)peak and sonic point,which usually means the so-called detonation driving zone(DDZ).For the machine learning prediction,an ensemble model integrating Random Forest and Support Vector Regression was developed to predict the reaction zone width using a dataset of 19 publicly available samples.For the theoretical calculation,the Wood-Kirkwood(W-K)detonation theory model was utilized to implement numerical calculation of the reaction zone structures,incorporating chemical reaction kinetics to describe the detonation reaction progress.In experimental characterization,the Photon Doppler Velocimetry(PDV)was applied with LiF as the optical window to measure the particle velocity profile of detonation products and derive the reaction zone width.The results indicate that the reaction zone width values are 0.25 mm,0.28 mm,and 0.26 mm obtained from machine learning prediction,theoretical calculation,and experimental characterization,respectively.The corresponding velocities at the Chapman-Jouguet(CJ)point are 1,938 m/s,2,047 m/s,and 1,982 m/s,respectively.The maximum relative deviation in reaction zone width among three methods is approximately 7.7%,while that for CJ particle velocity is approximately 3.3%.These results from all three methods agree well within engineering error.This validates the effectiveness of integrating machine learning prediction,theoretical calculation and advanced experimental techniques for studying the detonation reaction zone structures of high explosives.This research provides insights into the detonation reaction mechanism and reaction zone characteristics of CL-20-based aluminized explosive.
基金Project(51305023) supported by the National Natural Science Foundation of ChinaProject(FRF-GF-17-B20) supported by the Fundamental Research Funds for the Central Universities of China
文摘This work describes an experimental investigation into the influence of geometric micro-groove texture patterns on the tribological performance of stainless steel.Five geometries were studied:one with untextured and four with micro-groove textured making parallel,triangular,square and hexagonal patterns.The micro-groove textures were produced using an MFT-20laser system as well as a two-step laser surface texturing(LST)process.Tribological performance was measured using a pin-on-disk tribometer.The investigation showed that the two-step LST process could fabricate high-precision micro-grooves.The experimental data indicated that the micro-groove textured surfaces achieved the lower frictional coefficients than the untextured surface and the geometric patterns had significantly affected the tribological properties of samples in both lubricated and unlubricated states.The results were analyzed from the lubricant supplying and fluid dynamic pressure effect under lubricated conditions as well as abrasive capture and remove under dry friction conditions.
基金supported by National Natural Science Foundation of China(Grant Nos. 50975096, 51175186)Guangdong Provincial Natural Science Foundation of China(Grant No. S2011010002225)+1 种基金Guangdong Provincial Science and Technology Planning Project of China(GrantNos. 2010A080802009, 2010A011300022, 2011B040300020)Fundamental Research Funds for the Central Universities of China(GrantNo.2012ZZ0053)
文摘The collapse of thin-walled micro-grooved heat pipes is a common phenomenon in the tube flattening process, which seriously influences the heat transfer performance and appearance of heat pipe. At present, there is no other better method to solve this problem. A new method by heating the heat pipe is proposed to eliminate the collapse during the flattening process. The effectiveness of the proposed method is investigated through a theoretical model, a finite element（FE） analysis, and experimental method. Firstly, A theoretical model based on a deformation model of six plastic hinges and the Antoine equation of the working fluid is established to analyze the collapse of thin walls at different temperatures. Then, the FE simulation and experiments of flattening process at different temperatures are carried out and compared with theoretical model. Finally, the FE model is followed to study the loads of the plates at different temperatures and heights of flattened heat pipes. The results of the theoretical model conform to those of the FE simulation and experiments in the flattened zone. The collapse occurs at room temperature. As the temperature increases, the collapse decreases and finally disappears at approximately 130 ℃ for various heights of flattened heat pipes. The loads of the moving plate increase as the temperature increases. Thus, the reasonable temperature for eliminating the collapse and reducing the load is approximately 130℃. The advantage of the proposed method is that the collapse is reduced or eliminated by means of the thermal deformation characteristic of heat pipe itself instead of by external support. As a result, the heat transfer efficiency of heat pipe is raised.
基金Project(U0834002) supported by the Joint Funds of the National Nature Science Foundation of China and Guangdong ProvinceProject (2009ZM0134) supported by the Foundational Research Funds for the Central Universities in China
文摘Heat pipe is always bent in the typical application of electronic heat dissipation at high heat flux,which greatly affects its heat transfer performance. The capillary limit of heat transport in the bent micro-grooved heat pipes was analyzed in the vapor pressure drop,the liquid pressure drop and the interaction of the vapor with wick fluid. The bent heat pipes were fabricated and tested from the bending angle,the bending position and the bending radius. The results show that temperature difference and thermal resistance increase while the heat transfer capacity of the heat pipe decreases,with the increase of the bending angles and the bending position closer to the vapor section. However,the effects of bending radius can be ignored. The result agrees well with the predicted equations.
基金supported by the National Natural Science Foundation of China(Grant No.51109178)the Science and Technology Innovation Foundation of Northwestern Polytechnical University,China(Grant No.JC20120218)
文摘We have investigated experimentally the process of a droplet impact on a regular micro-grooved surface. The target surfaces are patterned such that micro-scale spokes radiate from the center, concentric circles, and parallel lines on the polishing copper plate, using Quasi-LIGA molding technology. The dynamic behavior of water droplets impacting on these structured surfaces is examined using a high-speed camera, including the drop impact processes, the maximum spreading diameters, and the lengths and numbers of fingers at different values of Weber number. Experimental results validate that the spreading processes are arrested on all target surfaces at low velocity. Also, the experimental results at higher impact velocity demonstrate that the spreading process is conducted on the surface parallel to the micro-grooves, but is arrested in the direction perpendicular to the micro-grooves. Besides, the lengths of fingers increase observably, even when they are ejected out as tiny droplets along the groove direction, at the same time the drop recoil velocity is reduced by micro-grooves which are parallel to the spreading direction, but not by micro-grooves which are vertical to the spreading direction.
基金supported by the National Natural Science Foundation of China(No.11104162)the Shandong Province Young and Middle-Aged Scientists Research Awards Fund(No.2011BSB01110)
文摘A novel optical fiber sensor with a U-shaped micro-groove structure ablated by femtosecond laser on single-mode fiber for measuring air relative humidity(RH)is reported in this paper.In order to improve the accuracy of sensor,a graphene oxide(GO)/polyvinyl alcohol(PVA)composite film is coated on the surface of micro-groove structure.In the U-shaped micro-groove structure,the remaining core and micro-cavity in the micro-groove make up two major optical propagation paths,forming a Mach-Zehnder interferometer(MZI).The sensor has a good linear response within the RH range of 30%—85%,and the maximum sensitivity can reach 0.638 1 nm/%RH.The effect of temperature on the overall performance of the humidity sensor is also investigated.As a new type of all-fiber device,the sensor shows excellent sensitivity and stability.
文摘A magnetic abrasive finishing process using an alternating magnetic field is proposed for the finishing of complex surfaces.In an alternating field,the periodic changes in current will cause the magnetic cluster used as a magnetic brush to fluctuate,which will not only continuously replace the abrasive particles in contact with the workpiece,but also periodically adjust the shape of the magnetic cluster to better fit the surface of the workpiece.In this paper,the influence of a combination of alternating and static magnetic fields on the magnetic field in the finishing area is analyzed.The feasibility of this process for finishing micro-grooves is investigated.Simulations and experimental measurements show that the combination of alternating and static magnetic fields can retain the advantages of the alternating field while increasing the magnetic flux density in the finishing area.The experimental results show that the process is feasible for finishing micro-grooves,with an excellent deburring effect on the groove edges.
文摘A growing interest is given to the hydrodynamic lubricated friction pair with surface textured. Because of its relatively simple processing methods and low manufacturing costs,micro-groove has become the most valuable form of surface texture,and definitely has broad application prospects in mechanical engineering. Based on numerical simulation,the present study aims to examine the effects of surface forms and cross-section types of micro-groove on the hydrodynamic lubrication performance,and to find out the optimal structural parameter for designing logical micro-grooves. Different surface form and cross-section types are designed to maximize the texture hydrodynamic effect. The average pressure of such microgrooved surface is evaluated in detail,and the variation trends with changes of the length of micro-groove,lp,or the depth,hp,are discussed. The theoretical results show that micro-grooves with rational design contribute to the improvement of hydrodynamic lubrication performance of friction pair largely. For a specific micro-grooved friction pair,the optimal surface form and crosssection type make the lubrication performance best.
基金Supported by Shaanxi Provincial Social Development Fund,No.2024SF-YBXM-140.
文摘BACKGROUND Post-hepatectomy liver failure(PHLF)after liver resection is one of the main complications causing postoperative death in patients with hepatocellular carcinoma(HCC).It is crucial to help clinicians identify potential high-risk PHLF patients as early as possible through preoperative evaluation.AIM To identify risk factors for PHLF and develop a prediction model.METHODS This study included 248 patients with HCC at The Second Affiliated Hospital of Air Force Medical University between January 2014 and December 2023;these patients were divided into a training group(n=164)and a validation group(n=84)via random sampling.The independent variables for the occurrence of PHLF were identified by univariate and multivariate analyses and visualized as nomograms.Ultimately,comparisons were made with traditional models via receiver operating characteristic(ROC)curves,calibration curves,and decision curve analysis(DCA).RESULTS In this study,portal vein width[odds ratio(OR)=1.603,95%CI:1.288-1.994,P≤0.001],the preoperative neutrophil-to-lymphocyte ratio(NLR)(OR=1.495,95%CI:1.126-1.984,P=0.005),and the albumin-bilirubin(ALBI)score(OR=8.868,95%CI:2.144-36.678,P=0.003)were independent risk factors for PHLF.A nomogram prediction model was developed using these factors.ROC and DCA analyses revealed that the predictive efficacy and clinical value of this model were better than those of traditional models.CONCLUSION A new Nomogram model for predicting PHLF in HCC patients was successfully established based on portal vein width,the NLR,and the ALBI score,which outperforms the traditional model.
文摘BACKGROUND As red blood cell distribution width(RDW)and albumin have been shown to be independent predictors of mortality from various diseases,this study aimed to investigate the effect of the RDW to albumin ratio(RA)as an independent predictor of the prognosis of patients admitted to the coronary care unit(CCU).AIM To use the RDW and albumin level to predict the prognosis of patients in the CCU.METHODS Data were obtained from the Medical Information Mart Intensive Care III database.The primary outcome was 365-day all-cause mortality,whereas the secondary outcomes were 30-and 90-day all-cause mortality,hospital length of stay(LOS),and CCU LOS.Cox proportional hazards regression model,propen-sity score matching,and receiver operating characteristic curve analyses were used.RESULTS The hazard ratio(95%confidence interval)of the upper tertile(RA>4.66)was 1.62(1.29 to 2.03)when compared with the reference(RA<3.84)in 365-day all-cause mortality.This trend persisted after adjusting for demographic and clinical variables in the propensity score-matching analysis.Similar trends were observed for the secondary outcomes of hospital and CCU LOS.Receiver operating characteristic curve analysis was performed by combining the RA and sequential organ failure assessment(SOFA)scores,and the C-statistic was higher than that of the SOFA scores(0.733 vs 0.702,P<0.001).CONCLUSION RA is an independent prognostic factor in patients admitted to the CCU.RA combined with the SOFA score can improve the predictive ability of the SOFA score.However,our results should be verified in future prospective studies.
基金Supported by the National Natural Science Foundation of China,No.81302124.
文摘BACKGROUND Red blood cell distribution width(RDW)is associated with the development and progression of various diseases.AIM To explore the association between pretreatment RDW and short-term outcomes after laparoscopic pancreatoduodenectomy(LPD).METHODS A total of 804 consecutive patients who underwent LPD at our hospital between March 2017 and November 2021 were retrospectively analyzed.Correlations between pretreatment RDW and clinicopathological characteristics and short-term outcomes were investigated.RESULTS Patients with higher pretreatment RDW were older,had higher Eastern Cooperative Oncology Group scores and were associated with poorer short-term outcomes than those with normal RDW.High pretreatment RDW was an independent risk factor for postoperative complications(POCs)(hazard ratio=2.973,95%confidence interval:2.032-4.350,P<0.001)and severe POCs of grade IIIa or higher(hazard ratio=3.138,95%confidence interval:2.042-4.824,P<0.001)based on the Clavien-Dino classification system.Subgroup analysis showed that high pretreatment RDW was an independent risk factor for Clavien-Dino classi-fication grade IIIb or higher POCs,a comprehensive complication index score≥26.2,severe postoperative pancreatic fistula,severe bile leakage and severe hemorrhage.High pretreatment RDW was positively associated with the neutrophil-to-lymphocyte ratio and platelet-to-lymphocyte ratio and was negatively associated with albumin and the prognostic nutritional index.CONCLUSION Pretreatment RDW was a special parameter for patients who underwent LPD.It was associated with malnutrition,severe inflammatory status and poorer short-term outcomes.RDW could be a surrogate marker for nutritional and inflammatory status in identifying patients who were at high risk of developing POCs after LPD.
基金supported by the National Natural Science Foundation of China(12071444,12201581)the Fundamental Research Program of Shanxi Province of China(202103021223191).
文摘The minimal widths of three bounded subsets of the unit sphere associated to a unit vector in a normed linear space are studied,and three related geometric constants are introduced.New characterizations of inner product spaces are also presented.From the perspective of minimal width,strongε-symmetry of Birkhoff orthogonality is introduced,and its relation toε-symmetry of Birkhoff orthogonality is shown.Unlike most of the existing parameters of the underlying space,these new constants are full dimensional in nature.
基金supported by the Zhejiang Provincial Natural Science Foundation,China(Grant No.LD24C130001)the National Natural Science Foundation of China(Grant Nos.W2412006 and 32372125)+3 种基金the Hainan Provincial Natural Science Foundation,China(Grant Nos.GHYF2025029 and YBXM2422)the Innovation Platform for Academicians of Hainan Province,China(Grant No.YSPTZX202502)the National Modern Agricultural Industry Technology System Project,China(Grant No.CARS-01-18)the Special Support Program of Chinese Academy of Agricultural Sciences(Grant Nos.NKYCLJ-C-2021-015 and CAAS-ZDRW202401)。
文摘The width of rice leaves determines the size of the photosynthetic area.Optimizing rice leaf width can improve the photosynthetic rate,thereby increasing rice yield.In this study,a genome-wide association study(GWAS)was conducted by 225 rice germplasm resources to explore the genetic basis of rice flag leaf width(FLW).We identified nine QTLs associated with FLW(qFLWs),with phenotypic contribution rates ranging from 3.17%to 14.37%.Near-isogenic lines(NILs)were developed for fine-mapping of qFLW11,and the function of FLW11 was further verified.We narrowed down q FLW11 to an 87-kb interval,which contains five genes.
基金supported by the National Natural Science Foundation of China(Grant Nos.12172017 and 11872083)Project of Beijing Municipal Education Commission(Grant Nos.KZ202210005006 and KZ202110005007).
文摘Intracranial aneurysm(IA)is a prevalent cerebrovascular disease associated with high mortality and disability rates upon rupture.The hemodynamics of IA,which are significantly influenced by geometric parameters,directly impact its rupture.This study focuses on investigating the transient flow characteristics in saccular IA models fabricated using a water droplet-based method,specifically examining the influence of neck widths.Particle image velocimetry technique and numerical simulation were employed to investigate the dynamic evolution of flow structures within three IA models.The results reveal that neck width(W)has a substantial effect on flow characteristics in the neck region,subsequently impacting the deep flow inside the sac.Three distinct patterns were observed during flow evolution inside the sac:for W=2 mm,two vortices occur and then disappear with relatively low average flow velocity;for W=4 mm,enhanced effects of a high-speed jet result in periodic pulsatile flow velocity distribution while maintaining stable vortex core position;for W=6 mm,significant changes in flow velocity occur due to size expansion and intensity increase of vortices.These findings demonstrate that neck widths play a complex role in influencing transient flow characteristics within IAs.Overall,this research contributes to further understanding transient flow behaviors in IAs.
基金supported by the National Natural Science Foundation of China(No.62273234)Key Research and Development Program of Shaanxi(Program No.2022GY-306)Technology Innovation Leading Program of Shaanxi(Program No.2022QFY01-16).
文摘Accurate prediction of strip width is a key factor related to the quality of hot rolling manufacture.Firstly,based on strip width formation mechanism model within strip rolling process,an improved width mechanism calculation model is delineated for the optimization of process parameters via the particle swarm optimization algorithm.Subsequently,a hybrid strip width prediction model is proposed by effectively combining the respective advantages of the improved mechanism model and the data-driven model.In acknowledgment of prerequisite for positive error in strip width prediction,an adaptive width error compensation algorithm is proposed.Finally,comparative simulation experiments are designed on the actual rolling dataset after completing data cleaning and feature engineering.The experimental results show that the hybrid prediction model proposed has superior precision and robustness compared with the improved mechanism model and the other eight common data-driven models and satisfies the needs of practical applications.Moreover,the hybrid model can realize the complementary advantages of the mechanism model and the data-driven model,effectively alleviating the problems of difficult to improve the accuracy of the mechanism model and poor interpretability of the data-driven model,which bears significant practical implications for the research of strip width control.
文摘To cater the need for real-time crack monitoring of infrastructural facilities,a CNN-regression model is proposed to directly estimate the crack properties from patches.RGB crack images and their corresponding masks obtained from a public dataset are cropped into patches of 256 square pixels that are classified with a pre-trained deep convolution neural network,the true positives are segmented,and crack properties are extracted using two different methods.The first method is primarily based on active contour models and level-set segmentation and the second method consists of the domain adaptation of a mathematical morphology-based method known as FIL-FINDER.A statistical test has been performed for the comparison of the stated methods and a database prepared with the more suitable method.An advanced convolution neural network-based multi-output regression model has been proposed which was trained with the prepared database and validated with the held-out dataset for the prediction of crack-length,crack-width,and width-uncertainty directly from input image patches.The pro-posed model has been tested on crack patches collected from different locations.Huber loss has been used to ensure the robustness of the proposed model selected from a set of 288 different variations of it.Additionally,an ablation study has been conducted on the top 3 models that demonstrated the influence of each network component on the pre-diction results.Finally,the best performing model HHc-X among the top 3 has been proposed that predicted crack properties which are in close agreement to the ground truths in the test data.
