The highly efficient manufacturing of atomic-scale smooth β-Ga_(2)O_(3)surface is fairly challenging because β-Ga_(2)O_(3)is a typical difficult-to-machine material.In this study,a novel plasma dry etching method na...The highly efficient manufacturing of atomic-scale smooth β-Ga_(2)O_(3)surface is fairly challenging because β-Ga_(2)O_(3)is a typical difficult-to-machine material.In this study,a novel plasma dry etching method named plasma-based atom-selective etching(PASE)is proposed to achieve the highly efficient,atomic-scale,and damage-free polishing of β-Ga_(2)O_(3).The plasma is excited through the inductive coupling principle and carbon tetrafluoride is utilized as the main reaction gas to etch β-Ga_(2)O_(3).The core of PASE polishing of β-Ga_(2)O_(3)is the remarkable lateral etching effect,which is ensured by both the intrinsic property of the surface and the extrinsic temperature condition.As revealed by density functional theory-based calculations,the intrinsic difference in the etching energy barrier of atoms at the step edge(2.36 eV)and in the terrace plane(4.37 eV)determines their difference in the etching rate,and their etching rate difference can be greatly enlarged by increasing the extrinsic temperature.The polishing of β-Ga_(2)O_(3)based on the lateral etching effect is further verified in the etching experiments.The Sa roughness of β-Ga_(2)O_(3)(001)substrate is reduced from 14.8 nm to 0.057 nm within 120 s,and the corresponding material removal rate reaches up to 20.96μm·min^(−1).The polished β-Ga_(2)O_(3)displays significantly improved crystalline quality and photoluminescence intensity,and the polishing effect of PASE is independent of the crystal face of β-Ga_(2)O_(3).In addition,the competition between chemical etching and physical reconstruction,which is determined by temperature and greatly affects the surface state of β-Ga_(2)O_(3),is deeply studied for the first time.These findings not only demonstrate the high-efficiency and high-quality polishing of β-Ga_(2)O_(3)via atmospheric plasma etching but also hold significant implications for guiding future plasma-based surface manufacturing of β-Ga_(2)O_(3).展开更多
We propose a method to measure the flatness of an object with a petal-like pattern generated by the interference of the measured orbital angular momentum(OAM)beam and the reference OAM beam which carries the opposite ...We propose a method to measure the flatness of an object with a petal-like pattern generated by the interference of the measured orbital angular momentum(OAM)beam and the reference OAM beam which carries the opposite OAM state.By calculating the difference between the petal rotation angle without/with the object,the thickness information of the object,and then the flatness information,can be evaluated.Furthermore,the direction of the object’s flatness can be determined by the petal’s clockwise/counterclockwise rotation.We theoretically analyze the relationship between the object’s thickness and petal rotation angle,and verify the proposed method by experiment.The experimental results show that the proposed method is a high precision flatness measurement and can obtain the convex/concave property of the flatness.For the 1.02 mm glass sample,the mean deviation of the flatness is 1.357×10^(-8) and the variance is 0.242×10^(-16).For the 0.50 mm glass sample,the mean deviation of the flatness is 1.931×10^(-8) and the variance is 2.405×10^(-16).Two different topological charges are adopted for the 2.00 mm glass sample,and their flatness deviations are 0.239×10^(-8)(ℓ=1)and 0.246×10^(-8)(ℓ=2),where their variances are 0.799×10^(-18)(ℓ=1)and 0.775×10^(-18)(ℓ=2),respectively.It is shown that the flatness measured by the proposed method is the same for the same sample when different topological charges are used.All results indicate that the proposed method may provide a high flatness measurement,and will be a promising way to measure the flatness.展开更多
Real flatness images are the bases for flatness detection based on machine vision of cold rolled strip.The characteristics of a real flatness image are analyzed,and a lightweight strip location detection(SLD)model wit...Real flatness images are the bases for flatness detection based on machine vision of cold rolled strip.The characteristics of a real flatness image are analyzed,and a lightweight strip location detection(SLD)model with deep semantic segmentation networks is established.The interference areas in the real flatness image can be eliminated by the SLD model,and valid information can be retained.On this basis,the concept of image flatness is proposed for the first time.An image flatness representation(IFAR)model is established on the basis of an autoencoder with a new structure.The optimal structure of the bottleneck layer is 16×16×4,and the IFAR model exhibits a good representation effect.Moreover,interpretability analysis of the representation factors is carried out,and the difference and physical meaning of the representation factors for image flatness with different categories are analyzed.Image flatness with new defect morphologies(bilateral quarter waves and large middle waves)that are not present in the original dataset are generated by modifying the representation factors of the no wave image.Lastly,the SLD and IFAR models are used to detect and represent all the real flatness images on the test set.The average processing time for a single image is 11.42 ms,which is suitable for industrial applications.The research results provide effective methods and ideas for intelligent flatness detection technology based on machine vision.展开更多
Aiming at the problem of insufficient prediction accuracy of strip flatness at the outlet of cold tandem rolling,the prediction performance of strip flatness based on different ensemble methods was studied and a high-...Aiming at the problem of insufficient prediction accuracy of strip flatness at the outlet of cold tandem rolling,the prediction performance of strip flatness based on different ensemble methods was studied and a high-precision prediction ensemble model of strip flatness at the outlet was established.Firstly,based on linear regression(LR),K nearest neighbors(KNN),support vector regression,regression trees(RT),and backpropagation neural network(BPN),bagging,boosting,and stacking ensemble methods were used for ensemble experiments.Secondly,three existing ensemble models,i.e.,random forest,extreme random tree(ET)and extreme gradient boosting,were used to conduct experiments and compare the results.The research shows that bagging,boosting,and stacking three ensemble methods have the most significant improvement in the prediction accuracy of the regression trees model,which is increased by 5.28%,6.51%,and 5.32%,respectively.At the same time,the stacking ensemble method improves both the simple model and the complex model,and the improvement effect on the simple base model is the greatest,which is 4.69%higher than that of the base model KNN.Comparing all of the ensemble models,the stacking ensemble model of level-1(ET,AdaBoost-RT,LR,BPN)paired with level-2(LR)was discovered to be the best model(EALB-LR)and can be further studied for industrial applications.展开更多
The signs of the electric field markers in Figs.2 and 4 of the paper[Chin.Phys.B 32104211(2023)]have been corrected.These modifications do not affect the results derived in the paper.
To achieve stable rolling,the influence of a tension mechanism of a large diameter ratio roll system on the rolling process of a strip flatness electromagnetic control rolling mill is studied.Through the analysis of t...To achieve stable rolling,the influence of a tension mechanism of a large diameter ratio roll system on the rolling process of a strip flatness electromagnetic control rolling mill is studied.Through the analysis of the rolling deformation zone,the deformation zone composition form of a large diameter ratio roll system and a calculation formula of neutral angle under tension are proposed.To analyze the effect of front and post tensions on the rolling characteristic and the strip flatness control characteristic,a three-dimensional rolling finite element(FE)model of a large diameter ratio roll system with the function of roll profile electromagnetic control is established by FE software and verified by a strip flatness electromagnetic control rolling mill.Based on the model,the strip thickness characteristic,metal transverse flow,strip flatness state,and adjustment range of the loaded roll gap are analyzed for different front and post tensions setting values.The results show that changing the front or post tension setting values can improve the single-pass reduction rate of a large diameter ratio roll system and have little effect on the flatness control ability of the strip flatness electromagnetic control rolling mill.展开更多
A non-contact method for millimeter-scale inspection of material surface flatness via Laser-Induced Breakdown Spectroscopy(LIBS)is investigated experimentally.The experiment is performed using a planished surface of a...A non-contact method for millimeter-scale inspection of material surface flatness via Laser-Induced Breakdown Spectroscopy(LIBS)is investigated experimentally.The experiment is performed using a planished surface of an alloy steel sample to simulate its various flatness,ranging from 0 to 4.4 mm,by adjusting the laser focal plane to the surface distance with a step length of 0.2 mm.It is found that LIBS measurements are successful in inspecting the flatness differences among these simulated cases,implying that the method investigated here is feasible.It is also found that,for achieving the inspection of surface flatness within such a wide range,when univariate analysis is applied,a piecewise calibration model must be constructed.This is due to the complex dependence of plasma formation conditions on the surface flatness,which inevitably complicates the inspection procedure.To solve the problem,a multivariate analysis with the help of Back-Propagation Neural Network(BPNN)algorithms is applied to further construct the calibration model.By detailed analysis of the model performance,we demonstrate that a unified calibration model can be well established based on BPNN algorithms for unambiguous millimeter-scale range inspection of surface flatness with a resolution of about 0.2 mm.展开更多
Systems hosting flat bands offer a powerful platform for exploring strong correlation physics.Theoretically,topological degeneracy arising in systems with non-trivial topological orders on periodic manifolds of non-ze...Systems hosting flat bands offer a powerful platform for exploring strong correlation physics.Theoretically,topological degeneracy arising in systems with non-trivial topological orders on periodic manifolds of non-zero genus can generate ideal flat bands.However,experimental realization of such geometrically engineered systems is very difficult.In this work,we demonstrate that flat planes with strategically patterned hole defects can engineer ideal flat bands.We construct two families of models:singular flat band systems where degeneracy is stabilized by non-contractible loop excitations tied to hole defects and perfectly nested van Hove systems where degeneracy arises from line excitations in momentum space.These models circumvent the need for exotic manifolds while retaining the essential features of topological flat bands.By directly linking defect engineering to degeneracy mechanisms,our results establish a scalable framework for experimentally accessible flat band design.展开更多
With the most advanced and sophisticated technologies and equipment,NYBELT is one of the largest manufacturers of flat transmission belts in the world.Under the Certified Quality,Environment,Occupational Health&Sa...With the most advanced and sophisticated technologies and equipment,NYBELT is one of the largest manufacturers of flat transmission belts in the world.Under the Certified Quality,Environment,Occupational Health&Safety,and Energy Standardized ISO Management System,NYBELT can produce all kinds of flat transmission belts,roller coverings and conveyor belts applicable to textile,printing&packaging,electronics and other industries.Due to the superior quality and the reasonable prices,we have become well known in providing high quality belting products and excellent service to customers all over the world.Our success in the past gives us the confidence to look into the future with great expectations.展开更多
In a peach orchard in Lyuxiang Town,Jinshan District,Shanghai,youth delegates from 13 countries,officials from the Food and Agriculture Organization of the United Nations(FAO),and agricultural heritage experts were im...In a peach orchard in Lyuxiang Town,Jinshan District,Shanghai,youth delegates from 13 countries,officials from the Food and Agriculture Organization of the United Nations(FAO),and agricultural heritage experts were impressed by sweet and juicy Jinshan flat peaches.Jinshan has a history of flat peach cultivation that spans hundreds of years dating back to the Yuan Dynasty(1271-1368).展开更多
Flat electronic bands in condensed matter provide a rich avenue for exploring novel quantum phenomena. Here, we report an optical spectroscopy study of a topological hourglass semimetal Nb_(3)SiTe_(6) with the electri...Flat electronic bands in condensed matter provide a rich avenue for exploring novel quantum phenomena. Here, we report an optical spectroscopy study of a topological hourglass semimetal Nb_(3)SiTe_(6) with the electric field of the incident light parallel to its crystalline ab-plane. The ab-plane optical conductivity spectra of Nb_(3)SiTe_(6) single crystals exhibit a remarkable peak-like feature around 1.20 eV, which is mainly contributed by the direct optical transitions between the two ab-initio-calculation-derived flat bands along the momentum direction Z–U. Our results pave the way for investigating exotic quantum phenomena based on the flat bands in topological hourglass semimetals.展开更多
In this paper,we will discuss the almost global existence result for d-dimensional fractional nonlinear Schrodinger equation on flat torus,which is based on BNF technique,the tame property and the analysis of the spec...In this paper,we will discuss the almost global existence result for d-dimensional fractional nonlinear Schrodinger equation on flat torus,which is based on BNF technique,the tame property and the analysis of the spectrum of(-Δ)^(s).展开更多
This study delves into both experimental and analytical examinations of heat exchange in a straight channel, where Al_(2)O_(3)-water nanofluids are utilized, spanning the Reynolds number spectrum from 100 to 1800. Div...This study delves into both experimental and analytical examinations of heat exchange in a straight channel, where Al_(2)O_(3)-water nanofluids are utilized, spanning the Reynolds number spectrum from 100 to 1800. Diverse volume fractions(1%, 2%, and 3%) of Al_(2)O_(3)-water nanofluids are meticulously prepared and analyzed. The essential physical properties of these nanofluids, critical for evaluating their thermal and flow characteristics, have been comprehensively assessed. From a quantitative perspective, numerical simulations are employed to predict the Nusselt number(Nu) and friction factor(f). The empirical findings reveal intriguing trends: the friction factor experiences an upward trend with diminishing velocity, attributed to heightened molecular cohesion. Conversely, the friction factor demonstrates a decline with diminishing volume fractions, a consequence of reduced particle size. Both the nanofluid's viscosity and heat transfer coefficient exhibit a rise in tandem with augmented volume flow rate and concentration gradient. Notably, the simulation results harmonize remarkably well with experimental data. Rigorous validation against prior studies underscores the robust consistency of these outcomes. In the pursuit of augmenting heat transfer, a volume fraction of 3% emerges as particularly influential, yielding an impressive 53.8% enhancement. Minor increments in the friction factor, while present, prove negligible and can be safely overlooked.展开更多
This paper proposes a method to generate Bessel-like collimated beams with suppressed side lobes using the flexural vibration modes of a fixed boundary circular plate,which is excited by a longitudinally vibrating tra...This paper proposes a method to generate Bessel-like collimated beams with suppressed side lobes using the flexural vibration modes of a fixed boundary circular plate,which is excited by a longitudinally vibrating transducer in a ring excitation manner.The factors affecting the generation of Bessel-like collimated beams are investigated by theoretical analysis,numerical simulation and experimental methods.The results indicate that Bessel-like wave can be generated by a thin circular plate with fixed boundaries.The third-order mode of the circular plate can be modified to generate a collimated beam with suppressing side lobes when it is excited in a ring excitation manner and the excitation position lies between the first two nodal circles of the plate.As the excitation radius increases,the main lobe width of the resulting Bessel-like collimated beam decreases,the extent of the focusing region increases,and the amplitude of the side lobes initially increases and then decreases.Based on the simulation results,a prototype Bessel-like collimated beam generation system is made and measured experimentally.The experimental results are in good agreement with the numerical results.The Bessel-like collimated beam can be generated by the proposed system,which has potential application in the fields of long-range detection,imaging of highly attenuated materials,and airflow acceleration.展开更多
The flattening of the internal governance of colleges and universities needs to follow the principles of democratic participation,equivalence of rights and responsibilities,and efficiency priority.The structural desig...The flattening of the internal governance of colleges and universities needs to follow the principles of democratic participation,equivalence of rights and responsibilities,and efficiency priority.The structural design should be comprehensively optimized and adjusted.The power distribution should follow the principle of coordination and balance between academic power and administrative power.The operation mechanism should focus on the scientificity and democracy of decision-making.The construction of supporting systems requires the improvement of the performance appraisal system as well as the incentive and supervision mechanisms.展开更多
Ice accretion on structures such as aircraft wings and wind turbine blades poses serious risks to aerodynamic performance and operational safety,particularly in cold and humid environments.This study conducts numerica...Ice accretion on structures such as aircraft wings and wind turbine blades poses serious risks to aerodynamic performance and operational safety,particularly in cold and humid environments.This study conducts numerical simulations of ice formation on thin flat plates using CFD and FENSAP-ICE,exploring how air temperature,wind velocity,and angle of attack(AOA)affect icing behavior and aerodynamic characteristics.Results indicate that ice thickness increases linearly over time.Rime ice forms at low temperatures due to immediate droplet freezing,whereas glaze ice develops at higher temperatures when a water film forms and subsequently refreezes into protruding ice horns;under identical conditions,rime ice consistently produces thicker ice layers than glaze ice.Increasing wind speed substantially enhances ice growth and coverage,while speeds as low as 1 m/s result in minimal accretion.Changes in AOA shift the icing region toward the pressure side,and AOAs of equal magnitude but opposite sign yield symmetrical ice accretion patterns and identical maximum thickness values.After icing,the plate’s leading edge becomes smoother,slightly reducing drag while increasing lift and moment coefficients.These findings highlight the dominant roles of temperature,wind speed,and AOA in determining ice morphology,extent,and aerodynamic impact,providing valuable insights for predicting icing effects and developing mitigation strategies for structures operating in icing-prone regions.展开更多
The present review explores the promising role of nanofluids and related hybrid variants in enhancing the efficiencyof flat tube car radiators.As vehicles become more advanced and demand better thermal performance,tra...The present review explores the promising role of nanofluids and related hybrid variants in enhancing the efficiencyof flat tube car radiators.As vehicles become more advanced and demand better thermal performance,traditional coolants are starting to fall short.Nanofluids,which involve tiny nanoparticles dispersed into standardcooling liquids,offer a new solution by significantly improving heat transfer capabilities.The article categorizesthe different types of nanofluids(ranging from those based on metals and metal oxides to carbon materials andhybrid combinations)and examines their effects on the improvement of radiator performance.General consensusexists in the literature that nanofluids can support better heat dissipation and enable accordingly the developmentof smaller and lighter radiators,which require less coolant and allow more compact vehicle designs.However,thisreview demonstrates that the use of nanofluids does not come without challenges.These include the long-termstability of these fluids and material compatibility issues.A critical discussion is therefore elaborated about thegaps to be filled and the steps to be undertaken to promote and standardize the use of these fluids in the industry.展开更多
The loop heat pipe with a flat evaporator is mainly divided into two forms:rectangular evaporator and disk-shaped evaporator.The rectangular evaporator has advantages such as low heat leakage,a thin shell,and a large ...The loop heat pipe with a flat evaporator is mainly divided into two forms:rectangular evaporator and disk-shaped evaporator.The rectangular evaporator has advantages such as low heat leakage,a thin shell,and a large contact area compared to the disk-shaped evaporator.However,most of the research on rectangular evaporators focuses onworking fluids such as water,methanol,and acetone,when theseworking fluids are in operation,the internal pressure of the evaporator is less than atmospheric pressure.Ammonia,propylene,and other working fluids can also be utilized in the loop heat pipe,these working fluids demonstrate better performance when operating within other temperature intervals,for example,the operating temperature range of ammonia is−20℃to 50℃,however,in an atmospheric pressure environment,it is very difficult for the shell of the rectangular evaporator to withstand the saturated vapor pressure of the working fluid.This paper designs a rectangular flat plate loop heat pipe that can use ammonia as the working fluid.The internal reinforcing structure is used to improve the pressure strength of the shell.The secondary wick connects the compensation chamber and the capillary wick hydraulically.The experiment indicates that this kind of rectangular evaporator is unaffected by the position,and the secondary wick can effectively supply liquid under different angles.The thermal resistance of the evaporator wall was analyzed,and it was found that the thermal resistance of the evaporator wall was the main component of the thermal resistance of the system.The heat transfer capacities of 460 W@0.5 m and 200W@10 m were tested.The test results indicate that by setting a reinforcing structure inside the flat plate evaporator,the evaporator can withstand internal pressure.Combined with the design of the secondary wick,the flat plate evaporator can use working fluids with different pressures,expanding the range of available working fluids.展开更多
This study presents a simplified numerical approach for evaluating the thermal performance of louvered fin and flat tube heat exchangers(LFFTHXs),which are critical in many thermal management applications but difficul...This study presents a simplified numerical approach for evaluating the thermal performance of louvered fin and flat tube heat exchangers(LFFTHXs),which are critical in many thermal management applications but difficult to model due to their complex geometries.The proposed method uses an equivalent convective heat transfer coefficient to represent the fins,significantly reducing the computational requirements of the simulations.Validation against the effectiveness-number of transfer units method showed average deviations of 4.4%for the novel louvered fin with two combined holes and 9.5%for conventional configurations,confirming the accuracy of the method.Further application to two-phase refrigerant scenarios using experimental data demonstrated the robustness of the method and its suitability for practical design and optimization of LFFTHXs.The approach not only improves the feasibility of thermal analysis in industrial applications but also provides a foundation for future research into more efficient heat exchanger designs.展开更多
Objective:To explore and analyze the clinical efficacy of flat mesh tension-free hernioplasty in the treatment of patients with inguinal hernia.Methods:A total of 60 patients with inguinal hernia were included and equ...Objective:To explore and analyze the clinical efficacy of flat mesh tension-free hernioplasty in the treatment of patients with inguinal hernia.Methods:A total of 60 patients with inguinal hernia were included and equally divided into an observation group(30 cases,flat mesh tension-free hernioplasty)and a control group(30 cases,mesh plug tension-free hernioplasty)based on differences in surgical plans.The visual analog scale(VAS)for postoperative pain,inflammatory markers(C-reactive protein,white blood cell count),and complication rates were compared between the two groups.Results:At 24 and 48 hours postoperatively,the VAS scores in the observation group were significantly lower than those in the control group(P<0.05).At 24 hours postoperatively,the levels of CRP and WBC were also lower in the observation group(P<0.05).The complication rate was slightly lower in the observation group(P>0.05).Conclusion:Flat mesh tension-free hernioplasty for inguinal hernia can alleviate postoperative pain and suppress inflammatory responses,with fewer complications,making it suitable for promotion at primary healthcare facilities.展开更多
基金supported by the National Natural Science Foundation of China(52375437,52035009)the Natural Science Foundation of Guangdong Province(2024B1515020027)+2 种基金the Shenzhen Science and Technology Program(Grant No.KQTD20170810110250357)for the financial supportthe assistance of SUSTech Core Research Facilitiessupported by Shenzhen Engineering Research Center for Semiconductorspecific Equipment。
文摘The highly efficient manufacturing of atomic-scale smooth β-Ga_(2)O_(3)surface is fairly challenging because β-Ga_(2)O_(3)is a typical difficult-to-machine material.In this study,a novel plasma dry etching method named plasma-based atom-selective etching(PASE)is proposed to achieve the highly efficient,atomic-scale,and damage-free polishing of β-Ga_(2)O_(3).The plasma is excited through the inductive coupling principle and carbon tetrafluoride is utilized as the main reaction gas to etch β-Ga_(2)O_(3).The core of PASE polishing of β-Ga_(2)O_(3)is the remarkable lateral etching effect,which is ensured by both the intrinsic property of the surface and the extrinsic temperature condition.As revealed by density functional theory-based calculations,the intrinsic difference in the etching energy barrier of atoms at the step edge(2.36 eV)and in the terrace plane(4.37 eV)determines their difference in the etching rate,and their etching rate difference can be greatly enlarged by increasing the extrinsic temperature.The polishing of β-Ga_(2)O_(3)based on the lateral etching effect is further verified in the etching experiments.The Sa roughness of β-Ga_(2)O_(3)(001)substrate is reduced from 14.8 nm to 0.057 nm within 120 s,and the corresponding material removal rate reaches up to 20.96μm·min^(−1).The polished β-Ga_(2)O_(3)displays significantly improved crystalline quality and photoluminescence intensity,and the polishing effect of PASE is independent of the crystal face of β-Ga_(2)O_(3).In addition,the competition between chemical etching and physical reconstruction,which is determined by temperature and greatly affects the surface state of β-Ga_(2)O_(3),is deeply studied for the first time.These findings not only demonstrate the high-efficiency and high-quality polishing of β-Ga_(2)O_(3)via atmospheric plasma etching but also hold significant implications for guiding future plasma-based surface manufacturing of β-Ga_(2)O_(3).
基金supported by the National Natural Science Foundation of China(Grant No.62375140)the Open Research Fund of National Laboratory of Solid State Microstructures(Grant No.M36055).
文摘We propose a method to measure the flatness of an object with a petal-like pattern generated by the interference of the measured orbital angular momentum(OAM)beam and the reference OAM beam which carries the opposite OAM state.By calculating the difference between the petal rotation angle without/with the object,the thickness information of the object,and then the flatness information,can be evaluated.Furthermore,the direction of the object’s flatness can be determined by the petal’s clockwise/counterclockwise rotation.We theoretically analyze the relationship between the object’s thickness and petal rotation angle,and verify the proposed method by experiment.The experimental results show that the proposed method is a high precision flatness measurement and can obtain the convex/concave property of the flatness.For the 1.02 mm glass sample,the mean deviation of the flatness is 1.357×10^(-8) and the variance is 0.242×10^(-16).For the 0.50 mm glass sample,the mean deviation of the flatness is 1.931×10^(-8) and the variance is 2.405×10^(-16).Two different topological charges are adopted for the 2.00 mm glass sample,and their flatness deviations are 0.239×10^(-8)(ℓ=1)and 0.246×10^(-8)(ℓ=2),where their variances are 0.799×10^(-18)(ℓ=1)and 0.775×10^(-18)(ℓ=2),respectively.It is shown that the flatness measured by the proposed method is the same for the same sample when different topological charges are used.All results indicate that the proposed method may provide a high flatness measurement,and will be a promising way to measure the flatness.
基金supported by the National Natural Science Foundation of China(No.U21A20118)the National Key Laboratory of Metal Forming Technology and Heavy Equipment,China National Heavy Machinery Research Institute Co.,Ltd.(No.S2208100.W04).
文摘Real flatness images are the bases for flatness detection based on machine vision of cold rolled strip.The characteristics of a real flatness image are analyzed,and a lightweight strip location detection(SLD)model with deep semantic segmentation networks is established.The interference areas in the real flatness image can be eliminated by the SLD model,and valid information can be retained.On this basis,the concept of image flatness is proposed for the first time.An image flatness representation(IFAR)model is established on the basis of an autoencoder with a new structure.The optimal structure of the bottleneck layer is 16×16×4,and the IFAR model exhibits a good representation effect.Moreover,interpretability analysis of the representation factors is carried out,and the difference and physical meaning of the representation factors for image flatness with different categories are analyzed.Image flatness with new defect morphologies(bilateral quarter waves and large middle waves)that are not present in the original dataset are generated by modifying the representation factors of the no wave image.Lastly,the SLD and IFAR models are used to detect and represent all the real flatness images on the test set.The average processing time for a single image is 11.42 ms,which is suitable for industrial applications.The research results provide effective methods and ideas for intelligent flatness detection technology based on machine vision.
基金This study was supported by the National Key Research and Development Program of China(No.2017YFB0304100)Key Projects of the National Natural Science Foundation of China(No.51634002).
文摘Aiming at the problem of insufficient prediction accuracy of strip flatness at the outlet of cold tandem rolling,the prediction performance of strip flatness based on different ensemble methods was studied and a high-precision prediction ensemble model of strip flatness at the outlet was established.Firstly,based on linear regression(LR),K nearest neighbors(KNN),support vector regression,regression trees(RT),and backpropagation neural network(BPN),bagging,boosting,and stacking ensemble methods were used for ensemble experiments.Secondly,three existing ensemble models,i.e.,random forest,extreme random tree(ET)and extreme gradient boosting,were used to conduct experiments and compare the results.The research shows that bagging,boosting,and stacking three ensemble methods have the most significant improvement in the prediction accuracy of the regression trees model,which is increased by 5.28%,6.51%,and 5.32%,respectively.At the same time,the stacking ensemble method improves both the simple model and the complex model,and the improvement effect on the simple base model is the greatest,which is 4.69%higher than that of the base model KNN.Comparing all of the ensemble models,the stacking ensemble model of level-1(ET,AdaBoost-RT,LR,BPN)paired with level-2(LR)was discovered to be the best model(EALB-LR)and can be further studied for industrial applications.
文摘The signs of the electric field markers in Figs.2 and 4 of the paper[Chin.Phys.B 32104211(2023)]have been corrected.These modifications do not affect the results derived in the paper.
基金supported by the Natural Science Foundation of Hebei Province of China(Grant No.E2021203129).
文摘To achieve stable rolling,the influence of a tension mechanism of a large diameter ratio roll system on the rolling process of a strip flatness electromagnetic control rolling mill is studied.Through the analysis of the rolling deformation zone,the deformation zone composition form of a large diameter ratio roll system and a calculation formula of neutral angle under tension are proposed.To analyze the effect of front and post tensions on the rolling characteristic and the strip flatness control characteristic,a three-dimensional rolling finite element(FE)model of a large diameter ratio roll system with the function of roll profile electromagnetic control is established by FE software and verified by a strip flatness electromagnetic control rolling mill.Based on the model,the strip thickness characteristic,metal transverse flow,strip flatness state,and adjustment range of the loaded roll gap are analyzed for different front and post tensions setting values.The results show that changing the front or post tension setting values can improve the single-pass reduction rate of a large diameter ratio roll system and have little effect on the flatness control ability of the strip flatness electromagnetic control rolling mill.
基金supported in part by the National Key Research and Development Program of China(No.2022YFA1602500)National Natural Science Foundation of China program(No.U2241288).
文摘A non-contact method for millimeter-scale inspection of material surface flatness via Laser-Induced Breakdown Spectroscopy(LIBS)is investigated experimentally.The experiment is performed using a planished surface of an alloy steel sample to simulate its various flatness,ranging from 0 to 4.4 mm,by adjusting the laser focal plane to the surface distance with a step length of 0.2 mm.It is found that LIBS measurements are successful in inspecting the flatness differences among these simulated cases,implying that the method investigated here is feasible.It is also found that,for achieving the inspection of surface flatness within such a wide range,when univariate analysis is applied,a piecewise calibration model must be constructed.This is due to the complex dependence of plasma formation conditions on the surface flatness,which inevitably complicates the inspection procedure.To solve the problem,a multivariate analysis with the help of Back-Propagation Neural Network(BPNN)algorithms is applied to further construct the calibration model.By detailed analysis of the model performance,we demonstrate that a unified calibration model can be well established based on BPNN algorithms for unambiguous millimeter-scale range inspection of surface flatness with a resolution of about 0.2 mm.
基金supported by the Ministry of Science and Technology(Grant No.2022YFA1403901)the National Natural Science Foundation of China(Grant Nos.12494594,11888101,12174428,and 12504192)+2 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB28000000)the New Cornerstone Investigator Program,the Chinese Academy of Sciences through the Youth Innovation Promotion Association(Grant No.2022YSBR-048)the Shanghai Science and Technology Innovation Action Plan(Grant No.24LZ1400800).
文摘Systems hosting flat bands offer a powerful platform for exploring strong correlation physics.Theoretically,topological degeneracy arising in systems with non-trivial topological orders on periodic manifolds of non-zero genus can generate ideal flat bands.However,experimental realization of such geometrically engineered systems is very difficult.In this work,we demonstrate that flat planes with strategically patterned hole defects can engineer ideal flat bands.We construct two families of models:singular flat band systems where degeneracy is stabilized by non-contractible loop excitations tied to hole defects and perfectly nested van Hove systems where degeneracy arises from line excitations in momentum space.These models circumvent the need for exotic manifolds while retaining the essential features of topological flat bands.By directly linking defect engineering to degeneracy mechanisms,our results establish a scalable framework for experimentally accessible flat band design.
文摘With the most advanced and sophisticated technologies and equipment,NYBELT is one of the largest manufacturers of flat transmission belts in the world.Under the Certified Quality,Environment,Occupational Health&Safety,and Energy Standardized ISO Management System,NYBELT can produce all kinds of flat transmission belts,roller coverings and conveyor belts applicable to textile,printing&packaging,electronics and other industries.Due to the superior quality and the reasonable prices,we have become well known in providing high quality belting products and excellent service to customers all over the world.Our success in the past gives us the confidence to look into the future with great expectations.
文摘In a peach orchard in Lyuxiang Town,Jinshan District,Shanghai,youth delegates from 13 countries,officials from the Food and Agriculture Organization of the United Nations(FAO),and agricultural heritage experts were impressed by sweet and juicy Jinshan flat peaches.Jinshan has a history of flat peach cultivation that spans hundreds of years dating back to the Yuan Dynasty(1271-1368).
基金Project supported by the Guangdong Basic and Applied Basic Research Foundation (Grant No. 2021B1515130007)the National Natural Science Foundation of China (Grant Nos. U21A20432 and 52273077)+1 种基金the National Key Research and Development Program of China (Grant No. 2022YFA1403800)the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB33000000)。
文摘Flat electronic bands in condensed matter provide a rich avenue for exploring novel quantum phenomena. Here, we report an optical spectroscopy study of a topological hourglass semimetal Nb_(3)SiTe_(6) with the electric field of the incident light parallel to its crystalline ab-plane. The ab-plane optical conductivity spectra of Nb_(3)SiTe_(6) single crystals exhibit a remarkable peak-like feature around 1.20 eV, which is mainly contributed by the direct optical transitions between the two ab-initio-calculation-derived flat bands along the momentum direction Z–U. Our results pave the way for investigating exotic quantum phenomena based on the flat bands in topological hourglass semimetals.
基金Supported by the National Natural Science Foundation of China(12101542,12371189,12371241).
文摘In this paper,we will discuss the almost global existence result for d-dimensional fractional nonlinear Schrodinger equation on flat torus,which is based on BNF technique,the tame property and the analysis of the spectrum of(-Δ)^(s).
文摘This study delves into both experimental and analytical examinations of heat exchange in a straight channel, where Al_(2)O_(3)-water nanofluids are utilized, spanning the Reynolds number spectrum from 100 to 1800. Diverse volume fractions(1%, 2%, and 3%) of Al_(2)O_(3)-water nanofluids are meticulously prepared and analyzed. The essential physical properties of these nanofluids, critical for evaluating their thermal and flow characteristics, have been comprehensively assessed. From a quantitative perspective, numerical simulations are employed to predict the Nusselt number(Nu) and friction factor(f). The empirical findings reveal intriguing trends: the friction factor experiences an upward trend with diminishing velocity, attributed to heightened molecular cohesion. Conversely, the friction factor demonstrates a decline with diminishing volume fractions, a consequence of reduced particle size. Both the nanofluid's viscosity and heat transfer coefficient exhibit a rise in tandem with augmented volume flow rate and concentration gradient. Notably, the simulation results harmonize remarkably well with experimental data. Rigorous validation against prior studies underscores the robust consistency of these outcomes. In the pursuit of augmenting heat transfer, a volume fraction of 3% emerges as particularly influential, yielding an impressive 53.8% enhancement. Minor increments in the friction factor, while present, prove negligible and can be safely overlooked.
基金Project supported by the National Natural Science Foundation of China(Grant No.12474440).
文摘This paper proposes a method to generate Bessel-like collimated beams with suppressed side lobes using the flexural vibration modes of a fixed boundary circular plate,which is excited by a longitudinally vibrating transducer in a ring excitation manner.The factors affecting the generation of Bessel-like collimated beams are investigated by theoretical analysis,numerical simulation and experimental methods.The results indicate that Bessel-like wave can be generated by a thin circular plate with fixed boundaries.The third-order mode of the circular plate can be modified to generate a collimated beam with suppressing side lobes when it is excited in a ring excitation manner and the excitation position lies between the first two nodal circles of the plate.As the excitation radius increases,the main lobe width of the resulting Bessel-like collimated beam decreases,the extent of the focusing region increases,and the amplitude of the side lobes initially increases and then decreases.Based on the simulation results,a prototype Bessel-like collimated beam generation system is made and measured experimentally.The experimental results are in good agreement with the numerical results.The Bessel-like collimated beam can be generated by the proposed system,which has potential application in the fields of long-range detection,imaging of highly attenuated materials,and airflow acceleration.
文摘The flattening of the internal governance of colleges and universities needs to follow the principles of democratic participation,equivalence of rights and responsibilities,and efficiency priority.The structural design should be comprehensively optimized and adjusted.The power distribution should follow the principle of coordination and balance between academic power and administrative power.The operation mechanism should focus on the scientificity and democracy of decision-making.The construction of supporting systems requires the improvement of the performance appraisal system as well as the incentive and supervision mechanisms.
基金supported by the National Natural Science Foundation of China(52278532)Sichuan Science and Technology Program(2024NSFSC0153)。
文摘Ice accretion on structures such as aircraft wings and wind turbine blades poses serious risks to aerodynamic performance and operational safety,particularly in cold and humid environments.This study conducts numerical simulations of ice formation on thin flat plates using CFD and FENSAP-ICE,exploring how air temperature,wind velocity,and angle of attack(AOA)affect icing behavior and aerodynamic characteristics.Results indicate that ice thickness increases linearly over time.Rime ice forms at low temperatures due to immediate droplet freezing,whereas glaze ice develops at higher temperatures when a water film forms and subsequently refreezes into protruding ice horns;under identical conditions,rime ice consistently produces thicker ice layers than glaze ice.Increasing wind speed substantially enhances ice growth and coverage,while speeds as low as 1 m/s result in minimal accretion.Changes in AOA shift the icing region toward the pressure side,and AOAs of equal magnitude but opposite sign yield symmetrical ice accretion patterns and identical maximum thickness values.After icing,the plate’s leading edge becomes smoother,slightly reducing drag while increasing lift and moment coefficients.These findings highlight the dominant roles of temperature,wind speed,and AOA in determining ice morphology,extent,and aerodynamic impact,providing valuable insights for predicting icing effects and developing mitigation strategies for structures operating in icing-prone regions.
文摘The present review explores the promising role of nanofluids and related hybrid variants in enhancing the efficiencyof flat tube car radiators.As vehicles become more advanced and demand better thermal performance,traditional coolants are starting to fall short.Nanofluids,which involve tiny nanoparticles dispersed into standardcooling liquids,offer a new solution by significantly improving heat transfer capabilities.The article categorizesthe different types of nanofluids(ranging from those based on metals and metal oxides to carbon materials andhybrid combinations)and examines their effects on the improvement of radiator performance.General consensusexists in the literature that nanofluids can support better heat dissipation and enable accordingly the developmentof smaller and lighter radiators,which require less coolant and allow more compact vehicle designs.However,thisreview demonstrates that the use of nanofluids does not come without challenges.These include the long-termstability of these fluids and material compatibility issues.A critical discussion is therefore elaborated about thegaps to be filled and the steps to be undertaken to promote and standardize the use of these fluids in the industry.
基金Science Foundation for Distinguished Young Scholars 2020-JCJQ-ZQ-042.
文摘The loop heat pipe with a flat evaporator is mainly divided into two forms:rectangular evaporator and disk-shaped evaporator.The rectangular evaporator has advantages such as low heat leakage,a thin shell,and a large contact area compared to the disk-shaped evaporator.However,most of the research on rectangular evaporators focuses onworking fluids such as water,methanol,and acetone,when theseworking fluids are in operation,the internal pressure of the evaporator is less than atmospheric pressure.Ammonia,propylene,and other working fluids can also be utilized in the loop heat pipe,these working fluids demonstrate better performance when operating within other temperature intervals,for example,the operating temperature range of ammonia is−20℃to 50℃,however,in an atmospheric pressure environment,it is very difficult for the shell of the rectangular evaporator to withstand the saturated vapor pressure of the working fluid.This paper designs a rectangular flat plate loop heat pipe that can use ammonia as the working fluid.The internal reinforcing structure is used to improve the pressure strength of the shell.The secondary wick connects the compensation chamber and the capillary wick hydraulically.The experiment indicates that this kind of rectangular evaporator is unaffected by the position,and the secondary wick can effectively supply liquid under different angles.The thermal resistance of the evaporator wall was analyzed,and it was found that the thermal resistance of the evaporator wall was the main component of the thermal resistance of the system.The heat transfer capacities of 460 W@0.5 m and 200W@10 m were tested.The test results indicate that by setting a reinforcing structure inside the flat plate evaporator,the evaporator can withstand internal pressure.Combined with the design of the secondary wick,the flat plate evaporator can use working fluids with different pressures,expanding the range of available working fluids.
基金supported by the National Natural Science Foundation of China(Grant No.12272345).
文摘This study presents a simplified numerical approach for evaluating the thermal performance of louvered fin and flat tube heat exchangers(LFFTHXs),which are critical in many thermal management applications but difficult to model due to their complex geometries.The proposed method uses an equivalent convective heat transfer coefficient to represent the fins,significantly reducing the computational requirements of the simulations.Validation against the effectiveness-number of transfer units method showed average deviations of 4.4%for the novel louvered fin with two combined holes and 9.5%for conventional configurations,confirming the accuracy of the method.Further application to two-phase refrigerant scenarios using experimental data demonstrated the robustness of the method and its suitability for practical design and optimization of LFFTHXs.The approach not only improves the feasibility of thermal analysis in industrial applications but also provides a foundation for future research into more efficient heat exchanger designs.
文摘Objective:To explore and analyze the clinical efficacy of flat mesh tension-free hernioplasty in the treatment of patients with inguinal hernia.Methods:A total of 60 patients with inguinal hernia were included and equally divided into an observation group(30 cases,flat mesh tension-free hernioplasty)and a control group(30 cases,mesh plug tension-free hernioplasty)based on differences in surgical plans.The visual analog scale(VAS)for postoperative pain,inflammatory markers(C-reactive protein,white blood cell count),and complication rates were compared between the two groups.Results:At 24 and 48 hours postoperatively,the VAS scores in the observation group were significantly lower than those in the control group(P<0.05).At 24 hours postoperatively,the levels of CRP and WBC were also lower in the observation group(P<0.05).The complication rate was slightly lower in the observation group(P>0.05).Conclusion:Flat mesh tension-free hernioplasty for inguinal hernia can alleviate postoperative pain and suppress inflammatory responses,with fewer complications,making it suitable for promotion at primary healthcare facilities.
