Single-walled carbon nanotubes(SWNTs)with enriched(n,m)species are in high demand for various advanced applications.Since the SWNT structure is largely influenced by the chemistry of the active catalyst during growth ...Single-walled carbon nanotubes(SWNTs)with enriched(n,m)species are in high demand for various advanced applications.Since the SWNT structure is largely influenced by the chemistry of the active catalyst during growth process,exploiting novel catalyst with bias towards specific SWNT chiralities has been challenging.In this work,we introduce a vanadium catalyst supported by mesoporous magnesia(V-MgO)for the selective growth of SWNTs using CO chemical vapor deposition(CVD).At a reaction temperature of 650℃,the(6,5)SWNT content reaches an impressive 67.9%among all semiconducting species,exceeding the selectivity of many commercial SWNT products.Post-CVD analysis reveals that the catalyst transforms into vanadium carbide(VC),which acts as a nucleation site for SWNT growth.Molecular dynamics simulations indicate that the energy at the SWNT-VC interface and the growth kinetics of SWNTs contribute to the chirality selectivity.This research opens up possibilities for the selective synthesis of SWNTs using cost-effective early transition metals,illuminating their future applications in fields such as bioimaging.展开更多
The thermochemical non-equilibrium phenomena encountered by hypersonic vehicles present significant challenges in their design.To investigate the thermochemical reaction flow behind shock waves,the non-equilibrium rad...The thermochemical non-equilibrium phenomena encountered by hypersonic vehicles present significant challenges in their design.To investigate the thermochemical reaction flow behind shock waves,the non-equilibrium radiation in the visible range using a shock tube was studied.Experiments were conducted with a shock velocity of 4.7 km/s,using nitrogen at a pressure of 20 Pa.To address measurement difficulties associated with weak radiation,a special square section shock tube with a side length of 380 mm was utilized.A high-speed camera characterized the shock wave’s morphology,and a spectrograph and a monochromator captured the radiation.The spectra were analyzed,and the numerical spectra were compared with experimental results,showing a close match.Temperature changes behind the shock wave were obtained and compared with numerical predictions.The findings indicate that the vibrational temperatures are overestimated,while the vibrational relaxation time is likely underestimated,due to the oversimplified portrayals of the non-equilibrium relaxation process in the models.Additionally,both experimental and simulated time-resolved profiles of radiation intensity at specific wavelengths were analyzed.The gathered data aims to enhance computational fluid dynamics codes and radiation models,improving their predictive accuracy.展开更多
The influence of the squeeze film between the tube and the support structure on flow-induced vibrations is a critical factor in tube bundles subjected to two-phase cross-flow.This aspect can significantly alter the th...The influence of the squeeze film between the tube and the support structure on flow-induced vibrations is a critical factor in tube bundles subjected to two-phase cross-flow.This aspect can significantly alter the threshold for fluidelastic instability and affect heat transfer efficiency.This paper presents a mathematical model incorporating the squeeze film force between the tube and the support structure.We aim to clarify the mechanisms underlying fluidelastic instability in tube bundle systems exposed to two-phase flow.Using a self-developed computer program,we performed numerical calculations to examine the influence of the squeeze film on the threshold of fluidelastic instability in the tube bundle system.Furthermore,we analyzed how the thickness and length of the squeeze film affect both the underlying mechanisms and the critical velocity of fluidelastic instability.展开更多
The commercialization of solid oxide fuel cells depends on the cathode,which possesses both high catalytic activity and a thermal-expansion coefficient(TEC)that aligns with the electrolyte.Although the cobalt-based ca...The commercialization of solid oxide fuel cells depends on the cathode,which possesses both high catalytic activity and a thermal-expansion coefficient(TEC)that aligns with the electrolyte.Although the cobalt-based cathode La_(0.6)Sr_(0.4)CoO_(3)(LSC)offers excellent catalytic performance,its TEC is significantly larger than that of the electrolyte.In this study,we mechanically mix Sm_(0.2)Ce_(0.8)O_(2−δ)(SDC)with LSC to create a composite cathode.By incorporating 50wt%SDC,the TEC decreases significantly from 18.29×10^(−6) to 13.90×10^(−6) K^(−1).Under thermal-shock conditions ranging from room temperature to 800℃,the growth rate of polarization resistance is only 0.658%per cycle,i.e.,merely 49%that of pure LSC.The button cell comprising the LSC-SDC composite cathode operates stably for over 900 h without Sr segregation,with a voltage growth rate of 1.11%/kh.A commercial flat-tube cell(active area:70 cm^(2))compris-ing the LSC-SDC composite cathode delivers 54.8 W at 750℃.The distribution of relaxation-time shows that the non-electrode portion is the main rate-limiting step.This study demonstrates that the LSC-SDC mixture strategy effectively improves the compatibility with the electrolyte while maintaining a high output,thus rendering it a promising commercial cathode material.展开更多
This study investigates the bond performance at the interfacial region shared by Ultra-High Performance Concrete(UHPC)and steel tubes through push-out tests.This study examines how changes in steel fiber volumetric ra...This study investigates the bond performance at the interfacial region shared by Ultra-High Performance Concrete(UHPC)and steel tubes through push-out tests.This study examines how changes in steel fiber volumetric ratio and thickness of steel tube influence the bond strength characteristics.The results show that as the enhancement of the steel tube wall thickness,the ultimate bond strength at the interface improves significantly,whereas the initial bond strength exhibits only slight variations.The influence of steel fiber volumetric ratio presents a nonlinear trend,with initial bond strength decreasing at low fiber content and increasing significantly as fiber content rises.Additionally,finite element(FE)simulations were applied to replicate the experimental conditions,and the outcomes showed strong correlation with the experimental data,confirming the exactitude of the FE model in predicting the bond behavior at the UHPC-Steel interface.These findings provide valuable insights for optimizing the design of UHPC-Filled steel tubes in high-performance structure.展开更多
In this paper,the Paley-Wiener theorem is extended to the analytic function spaces with general weights.We first generalize the theorem to weighted Hardy spaces Hp(0<p<∞)on tube domains by constructing a sequen...In this paper,the Paley-Wiener theorem is extended to the analytic function spaces with general weights.We first generalize the theorem to weighted Hardy spaces Hp(0<p<∞)on tube domains by constructing a sequence of L^(1)functions converging to the given function and verifying their representation in the form of Fourier transform to establish the desired result of the given function.Applying this main result,we further generalize the Paley-Wiener theorem for band-limited functions to the analytic function spaces L^(p)(0<p<∞)with general weights.展开更多
This study develops an analytical model to evaluate the cooling performance of a porous terracotta tubular direct evaporative heat and mass exchanger. By combining energy and mass balance equations with heat and mass ...This study develops an analytical model to evaluate the cooling performance of a porous terracotta tubular direct evaporative heat and mass exchanger. By combining energy and mass balance equations with heat and mass transfer coefficients and air psychrometric correlations, the model provides insights into the impact of design and operational parameters on the exchanger cooling performance. Validated against an established numerical model, it accurately simulates cooling behavior with a Root Mean Square Deviation of 0.43 - 1.18˚C under varying inlet air conditions. The results show that tube geometry, including equivalent diameter, flatness ratio, and length significantly influences cooling outcomes. Smaller diameters enhance wet-bulb effectiveness but reduce cooling capacity, while increased flatness and length improve both. For example, extending the flatness ratio of a 15 mm diameter, 0.6 m long tube from 1 (circular) to 4 raises the exchange surface area from 0.028 to 0.037 m2, increasing wet-bulb effectiveness from 60% to 71%. Recommended diameters range from 5 mm for tubes under 0.5 m to 1 cm for tubes 0.5 to 1 m in length. Optimal air velocities depend on tube length: 1 m/s for tubes under 0.8 m, 1.5 m/s for lengths of 0.8 to 1.2 m, and up to 2 m/s for longer tubes. This model offers a practical alternative to complex numerical and CFD methods, with potential applications in cooling tower optimization for thermal and nuclear power plants and geothermal heat exchangers.展开更多
This research investigates the bending response of folded multi-celled tubes(FMTs)fabricated by folded metal sheets.A three-point bending test for FMTs with circular and square sections is designed and introduced.The ...This research investigates the bending response of folded multi-celled tubes(FMTs)fabricated by folded metal sheets.A three-point bending test for FMTs with circular and square sections is designed and introduced.The base numerical models are correlated with physical experiments and a static crashworthiness analysis of six FMT configurations to assess their energy absorption characteristics.The influences of thickness,sectional shape,and load direction on the bending response are studied.Results indicate that increasing the thickness of the tube and radian of the inner tube enhances the crashworthiness performance of FMT,yielding a 20.50%increase in mean crushing force,a 55.53%increase in specific energy absorption,and an 18.05%decrease in peak crushing force compared to traditional multi-celled tubes(TMTs).A theoretical analysis of the specific energy absorption indicates that FMTs outperform TMTs,particularly when the peak crushing force is prominent.This study highlights the innovative and practical potential of FMTs to improve the crashworthiness of thin-walled structures.展开更多
The behavior of reinforced concrete(RC)square columns strengthened with self-compacting concrete(SCC)-filled steel tubes under cyclic loading was experimentally investigated.Tests were carried out on eleven reinforced...The behavior of reinforced concrete(RC)square columns strengthened with self-compacting concrete(SCC)-filled steel tubes under cyclic loading was experimentally investigated.Tests were carried out on eleven reinforced columns and one unreinforced column.The parameters studied for the strengthened columns included axial compression ratio,reinforcement rate,defect rate,strength of SCC,and the section form of a reinforced steel tube.The results show that the steel tube SCC reinforcement method can effectively strengthen RC columns,exert the restraint effect of steel tube,and delay the development of internal concrete cracks.The method can also significantly improve the bearing capacity of RC columns.Regarding ductility,the improvement of the reinforced column is obvious,the deformation resistance of the specimen is enhanced,and the degradation of stiffness and strength is relatively slow,indicating that it has good seismic performance.展开更多
This pictorial review discusses the imaging approach to evaluate for proper placement or complications of pediatric gastrostomy tube(G-tube)placement and long-term use.G-tubes are crucial for long-term nutritional sup...This pictorial review discusses the imaging approach to evaluate for proper placement or complications of pediatric gastrostomy tube(G-tube)placement and long-term use.G-tubes are crucial for long-term nutritional support in patients facing challenges with oral intake.The article depicts the role of imaging such as contrast radiography,fluoroscopy,ultrasound,and computed tomography scans for confirming G-tube position and evaluating complications,in addition to basic anatomical considerations and placement techniques.Complications discussed include malposition,intraperitoneal placement,buried bumper syndrome,and tube malfunction.Specific imaging techniques and checklists are provided to guide clinicians in assessing G-tube placement accurately.The latter half of the review is a comprehensive exploration of pearls and pitfalls of imaging when employed to detect complications to avoid false positives and negatives.展开更多
BACKGROUND Esophageal cancer(EC)is an aggressive malignancy with low survival(10%-30%).Nutritional problems are present throughout the perioperative period and are key to prognosis.Home enteral nutrition appears to im...BACKGROUND Esophageal cancer(EC)is an aggressive malignancy with low survival(10%-30%).Nutritional problems are present throughout the perioperative period and are key to prognosis.Home enteral nutrition appears to improve the nutritional status of patients with EC.Few studies have addressed the experience of patients administering their own nutritional fluids and managing their own feeding tubes at home.The aim of this study was to explore the real-life experience of self-management of feeding tubes in patients at home after EC surgery in the first 3 months after discharge following surgery.AIM To explore feeding tube self-management experience of patients at home 3 months after discharge following EC surgery.METHODS Face-to-face semi-structured interviews were conducted with 18 patients using a feeding tube at home after EC surgery.Thematic analysis of the recordings identified themes related to feeding tube self-management.RESULTS Patients expressed similar feelings about their tube management experiences concerning three contextualized themes:Self-management dilemmas,distressing experiences,and self-management facilitators.CONCLUSION There are many dilemmas and problems in self-managing feeding tubes in postoperative homebound patients with EC.Clinical staff should provide guidance to promote a positive change in self-management behavior.展开更多
The fabrication of one-dimensional metal/N-doped carbon materials has shown a promising prospect as efficient electrocata-lysts for oxygen reduction reaction(ORR).Herein,CoNi alloy nanoparticles anchored on N-doped ca...The fabrication of one-dimensional metal/N-doped carbon materials has shown a promising prospect as efficient electrocata-lysts for oxygen reduction reaction(ORR).Herein,CoNi alloy nanoparticles anchored on N-doped carbon nanotubes(CoNi@NCNT)are prepared by a dual-template strategy,using polypyrrole(PPy)tubes and CoNi-based metal-organic framework as the precursors.The as-formed CoNi@NCNT catalyst displays a half-wave potential(0.83 V)as well as good durability under alkaline medium.The excellent electrocatalytic performance is ascribed to a synergistic coupling of hierarchically tubular structure,highly electronic conductivity,and abundantly alloy-type active sites.When the CoNi@NCNT catalyst is applied in zinc-air battery(ZAB),the device displays a stable charge-discharge cycling performance.The present work affords a useful approach to constructing alloy/nitrogen-incorporated carbon-aceous materials as bifunctional electrocatalysts for high-performance ZABs.展开更多
In the anticorrosive coating line of a welded tube plant, the current status and existing problems of the medium-frequency induction heating equipment were discussed.Partial renovations of the power control cabinet ha...In the anticorrosive coating line of a welded tube plant, the current status and existing problems of the medium-frequency induction heating equipment were discussed.Partial renovations of the power control cabinet have been conducted.Parameters such as the DC current, DC voltage, intermediate frequency power, heating temperature, and the positioning signal at the pipe end were collected.A data acquisition and processing system, which can process data according to user needs and provide convenient data processing functions, has been developed using LabVIEW software.This system has been successfully applied in the coating line for the automatic control of high-power induction heating equipment, production management, and digital steel tube and/or digital delivery.展开更多
This study presents a fragility curve to assess explosively induced damage to military vehicle tires based on shock tube experiments.To replicate lateral damage scenarios that may occur in real battlefield environment...This study presents a fragility curve to assess explosively induced damage to military vehicle tires based on shock tube experiments.To replicate lateral damage scenarios that may occur in real battlefield environments involving missile or bomb detonations,extreme overpressure conditions were generated using a shock tube.The influence of explosive charge mass on tire damage was quantitatively evaluated.Experimental results identified two critical failure thresholds:for loss of pressure,the threshold was 354 kPa peak overpressure and 3052 kPa·ms impulse;for rupture,the values were 485 kPa and 4237 kPa-ms,respectively.The same damage profile was reproduced through finite element analysis(FEA),verifying the reliability of the simulation.A Single Degree of Freedom(SDOF)model and Kingery-Bulmash(K-B)chart were employed to generate pressure-impulse data as a function of standoff distance.These data were applied to a finite element tire model using the BLAST ENHANCED keyword in LS-DYNA.The applied peak overpressures were identical to the experimental values with a 24%-27%difference in impulse.The simulation also captured recurring bead rim separation phenomenon,leading to internal pressure loss consistent with high-speed camera observations from the experiments.The resulting fragility curve clearly defines the threshold conditions for tire damage and provides a standardized damage assessment model applicable to various explosive charge masses and stand-off distances.The proposed model offers a quantitative basis for evaluating tire vulnerability,providing foundational reference data for defense applications.Specifically,the findings are expected to serve as a reliable source for weapon effects analysis and target vulnerability assessments involving wheeled military vehicles.展开更多
BACKGROUND Gastroesophageal junction(GEJ)or gastrointestinal stromal tumor(GIST)are located in unfavorable parts of the stomach,due to the anatomical complexity of these regions,protecting the cardia while ensuring R0...BACKGROUND Gastroesophageal junction(GEJ)or gastrointestinal stromal tumor(GIST)are located in unfavorable parts of the stomach,due to the anatomical complexity of these regions,protecting the cardia while ensuring R0 resection is a major challenge for surgeons.CASE SUMMARY Two cases of GEJ stromal tumors were reported.Abdominal computed tomography scans revealed that both tumors were located at the GEJ,close to the posterior wall,with one tumor measuring greater than 5 cm.Both patients successfully underwent robot-assisted laparoscopic wedge resection of the stomach.The surgeries achieved R0 resection while preserving the cardia sphincter and maximizing gastric tissue preservation.Postoperatively,no symptoms such as gastroesophageal reflux or cardia stenosis were observed.Case 1:Postoperative pathology:GIST.Immunohistochemical results:Tumor cells were positive for CD34,CD117,and DOG1,and negative for SMA,desmin,S-100,and SDHB(normal expression).The Ki-67 proliferation index was approximately 5%.Case 2:Postoperative pathology:GIST.Immunohistochemical results:Tumor cells were positive for CD117(++),CD34(++),DOG1(+++),and focal positivity for SMA.Negative for desmin,S-100(few cells positive),and SDHB(preserved expression).The Ki-67 proliferation index was approximately 10%.CONCLUSION The gastric tube-guided robotic-assisted laparoscopic resection is a safe and effective method for tumor resection while preserving the cardia,and it is worth further promotion in clinical practice.展开更多
Knotting occurs in polymers and affects polymer properties.Physical understanding of polymer knots is limited due to the complex confo rmational space of knotted structures.The knotting problem can be handled by the t...Knotting occurs in polymers and affects polymer properties.Physical understanding of polymer knots is limited due to the complex confo rmational space of knotted structures.The knotting problem can be handled by the tube model,which assumes that knotted polymer segments are confined in a virtual tube.Recently,we quantified this virtual tube using a computational algorithm.The algorithm was limited to the simplest knot:3_(1)knot.It remains unclear how the tube model and computational algorithm are applied to more complex knots.In this work,we apply the tube model to 4_(1),5_(1),and 5_(2) knots,resulting in several findings.First,the computational algorithm developed for 3_(1) knot cannot be directly applied to 4_(1) knot.After modifying the algorithm,we quantify the tubes for 4_(1) knot.Second,we find that,for all four knot types,the knotcore region have less average bending energy density than unknotted regions when the chain bending stiffness is small.This counterintuitive result is explained by the tube model.Third,for all four knot types,polymer segments at the boundaries of knot cores adopt nearly straight conformations(almost zero bending)and exhibit lower local bending compared to other knot-core regions and unknotting regions.This local behavior is also consistent with prediction from the tube model.This counterintuitive result is also explained by the tube model.Fourth,for all four knot types,when a polymer has non-uniform bending stiffness,a knot prefers certain chain positions such that the knot boundary locates at one stiff segment.Overall,our work paves the way for applying the tube model to complex polymer knots and obtains many common results for different knot types,which can be useful in understanding many knotting systems,such as DNA knots in vivo.展开更多
In this study,we numerically investigate the rise of a Taylor bubble in a vertically oscillating round tube.The results show that increasing the oscillation frequency and amplitude reduces the bubble rise velocity,whi...In this study,we numerically investigate the rise of a Taylor bubble in a vertically oscillating round tube.The results show that increasing the oscillation frequency and amplitude reduces the bubble rise velocity,which is consistent with previously reported experimental findings.Analysis of the flow in the annular film region indicates that the influence of tube wall oscillations is minimal.This suggests that the effect of tube oscillations is essentially equivalent to that of an oscillating piston above the bubble,leading to a similar mechanism for bubble deceleration.Using a theoretical formula from the literature,we demonstrate that at sufficiently high frequencies,the amplitude of the tube velocity oscillations becomes the sole control parameter affecting bubble deceleration.This study enhances our understanding of Taylor bubble behavior in mechanically oscillating environments and provides useful insights into the design of control strategies for Taylor bubble motion in vertical slug flows.展开更多
Purpose:Acute otitis media caused by gram-negative bacteria is a common otological condition among pediatric patients.Eustachian tube dysfunction(ETD)plays a pivotal role in the delayed resolution of acute otitis medi...Purpose:Acute otitis media caused by gram-negative bacteria is a common otological condition among pediatric patients.Eustachian tube dysfunction(ETD)plays a pivotal role in the delayed resolution of acute otitis media,whereas the precise contribution of SIRT3 in this mechanism remains uncertain.This study aims to reveal the involvement of SIRT3 in murine ETD induced by LPS.Results:Histological analysis showed no baseline differences in ET structure between WT and SIRT3 knockout(SIRT3-KO)mice.However,LPS exposure led to increased goblet cell proliferation and MUC5 AC mucus secretion in both genotypes,with SIRT3-KO exacerbating these effects.The SIRT3-KO group displayed reduced cilia length.Functionally,SIRT3-KO mice showed a significantly higher initial POP and decreased MCC compared to the WT group after LPS exposure.Additionally,the active clearance of negative pressure(ACNP)was significantly reduced in SIRT3-KO mice,indicating compromised ET function.Conclusions:SIRT3-KO increased resistance to ET opening in mice exposed to LPS,and this effect may be related to the upregulated MUC5 AC expression,the increased surface tension of the luminal fluid and the impaired MCC function in mice exposed to LPS.展开更多
Recently,there have been few reports on the hot extrusion process of magnesium(Mg)alloy square tubes.In this work,we introduce a novel hot extrusion process called tube continuous expanding shear extrusion(t CESE)to p...Recently,there have been few reports on the hot extrusion process of magnesium(Mg)alloy square tubes.In this work,we introduce a novel hot extrusion process called tube continuous expanding shear extrusion(t CESE)to produce Mg alloy square tubes with heterogeneous structures.Compared to previously reported hot-extruded Mg alloy tubes,the tCESE samples exhibit simultaneous enhancements in both strength and ductility.The microstructure evolution during the t CESE process was analyzed in detail.It was found that the microstructure developed consecutively as a result of twinning-induced dynamic recrystallization(TDRX),discontinuous dynamic recrystallization(DDRX)and continuous dynamic recrystallization(CDRX)with different nucleation of new orientations,while static recrystallization(SRX)promoted the formation of heterogeneous structures.The strengthening mechanism in the t CESE samples was revealed by loading-unloading-reloading(LUR)tensile tests,viscoplastic self-consistent(VPSC)simulation and intermittent tensile tests.The improvement of the strength in the tCESE samples is attributed to the size refinement of the grains and the second-phases,and more importantly,to hetero-deformation induced(HDI)strengthening.The improvement of the ductility in the t CESE samples can be attributed to the significant increase in non-basal dislocations within the heterogeneous structures during tensile deformation.展开更多
Promoting the development of deep-sea mineral exploration instrumentation can help alleviate the global resource shortage faced by mankind.X-ray fluorescence(XRF)spectrometry has been widely used in the in situ analys...Promoting the development of deep-sea mineral exploration instrumentation can help alleviate the global resource shortage faced by mankind.X-ray fluorescence(XRF)spectrometry has been widely used in the in situ analysis of deep-sea minerals owing to its fast analytical speed,nondestructive nature,and wide analytical range.This study focused on the structural safety and detection efficiency of X-ray fluorescence in situ measurement equipment under high pressure for deep-sea XRF analysis.This study first combined finite element analysis and experiments to design and optimize the structure of an X-ray probe tube required for deep-sea mineral exploration and to determine the Be window thickness to ensure stress safety.Subsequently,the Monte Carlo method was used to analyze and optimize the Be window thickness on the X-ray probe tube to improve the accuracy of the elemental analyses.Finally,the effect of seawater thickness between the transmitter outer tube and rock wall was also considered.The results show that based on ocean depth in different detection environments,Be windows with a thickness of 1.5 mm or 2.0 mm can be selected to improve the detection efficiency of the device while ensuring the structural safety of the instrument.According to the design features and detection requirements of the device,in deep-sea exploration of minerals with characteristic peak energies below 10 keV,the transmitter outer tube should be as close as possible to the rock wall inside the logging.When the characteristic peak energy of the minerals is more than 10 keV,the distance between the transmitter outer tube and rock wall inside the logging should be controlled to approximately 2 mm.This study provides feasible solutions for future deep-sea mineral resource development and a useful reference for elemental analysis of minerals in the deep-sea or other extreme working environments.展开更多
基金financially supported by the Key Basic Research Project of Shandong Province(No.ZR2019ZD49)Taishan Scholar Foundation of Shandong Province(No.tstp20230627)Open Research Fund of State Key Laboratory of Polymer Physics and Chemistry,Changchun Institute of Applied Chemistry,Chinese Academy of Sciences。
文摘Single-walled carbon nanotubes(SWNTs)with enriched(n,m)species are in high demand for various advanced applications.Since the SWNT structure is largely influenced by the chemistry of the active catalyst during growth process,exploiting novel catalyst with bias towards specific SWNT chiralities has been challenging.In this work,we introduce a vanadium catalyst supported by mesoporous magnesia(V-MgO)for the selective growth of SWNTs using CO chemical vapor deposition(CVD).At a reaction temperature of 650℃,the(6,5)SWNT content reaches an impressive 67.9%among all semiconducting species,exceeding the selectivity of many commercial SWNT products.Post-CVD analysis reveals that the catalyst transforms into vanadium carbide(VC),which acts as a nucleation site for SWNT growth.Molecular dynamics simulations indicate that the energy at the SWNT-VC interface and the growth kinetics of SWNTs contribute to the chirality selectivity.This research opens up possibilities for the selective synthesis of SWNTs using cost-effective early transition metals,illuminating their future applications in fields such as bioimaging.
基金supported by the Key-Area Research and Development Program of Guangdong Province(Grant No.2021B0909060004)the National Natural Science Foundation of China(Grant Nos.12072355 and 92271117)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB0620202).
文摘The thermochemical non-equilibrium phenomena encountered by hypersonic vehicles present significant challenges in their design.To investigate the thermochemical reaction flow behind shock waves,the non-equilibrium radiation in the visible range using a shock tube was studied.Experiments were conducted with a shock velocity of 4.7 km/s,using nitrogen at a pressure of 20 Pa.To address measurement difficulties associated with weak radiation,a special square section shock tube with a side length of 380 mm was utilized.A high-speed camera characterized the shock wave’s morphology,and a spectrograph and a monochromator captured the radiation.The spectra were analyzed,and the numerical spectra were compared with experimental results,showing a close match.Temperature changes behind the shock wave were obtained and compared with numerical predictions.The findings indicate that the vibrational temperatures are overestimated,while the vibrational relaxation time is likely underestimated,due to the oversimplified portrayals of the non-equilibrium relaxation process in the models.Additionally,both experimental and simulated time-resolved profiles of radiation intensity at specific wavelengths were analyzed.The gathered data aims to enhance computational fluid dynamics codes and radiation models,improving their predictive accuracy.
基金financially supported by the National Natural Science Foundation of China(Grant No.12072336).
文摘The influence of the squeeze film between the tube and the support structure on flow-induced vibrations is a critical factor in tube bundles subjected to two-phase cross-flow.This aspect can significantly alter the threshold for fluidelastic instability and affect heat transfer efficiency.This paper presents a mathematical model incorporating the squeeze film force between the tube and the support structure.We aim to clarify the mechanisms underlying fluidelastic instability in tube bundle systems exposed to two-phase flow.Using a self-developed computer program,we performed numerical calculations to examine the influence of the squeeze film on the threshold of fluidelastic instability in the tube bundle system.Furthermore,we analyzed how the thickness and length of the squeeze film affect both the underlying mechanisms and the critical velocity of fluidelastic instability.
基金the financial support from the National Natural Science Foundation of China(No.22209191)Ningbo Key R&D Project(No.2023Z155).
文摘The commercialization of solid oxide fuel cells depends on the cathode,which possesses both high catalytic activity and a thermal-expansion coefficient(TEC)that aligns with the electrolyte.Although the cobalt-based cathode La_(0.6)Sr_(0.4)CoO_(3)(LSC)offers excellent catalytic performance,its TEC is significantly larger than that of the electrolyte.In this study,we mechanically mix Sm_(0.2)Ce_(0.8)O_(2−δ)(SDC)with LSC to create a composite cathode.By incorporating 50wt%SDC,the TEC decreases significantly from 18.29×10^(−6) to 13.90×10^(−6) K^(−1).Under thermal-shock conditions ranging from room temperature to 800℃,the growth rate of polarization resistance is only 0.658%per cycle,i.e.,merely 49%that of pure LSC.The button cell comprising the LSC-SDC composite cathode operates stably for over 900 h without Sr segregation,with a voltage growth rate of 1.11%/kh.A commercial flat-tube cell(active area:70 cm^(2))compris-ing the LSC-SDC composite cathode delivers 54.8 W at 750℃.The distribution of relaxation-time shows that the non-electrode portion is the main rate-limiting step.This study demonstrates that the LSC-SDC mixture strategy effectively improves the compatibility with the electrolyte while maintaining a high output,thus rendering it a promising commercial cathode material.
基金supported by grants from the Natural Science Foundation of Fujian Province(2021J011062)Minjiang Scholars Funding(GY-633Z21067).
文摘This study investigates the bond performance at the interfacial region shared by Ultra-High Performance Concrete(UHPC)and steel tubes through push-out tests.This study examines how changes in steel fiber volumetric ratio and thickness of steel tube influence the bond strength characteristics.The results show that as the enhancement of the steel tube wall thickness,the ultimate bond strength at the interface improves significantly,whereas the initial bond strength exhibits only slight variations.The influence of steel fiber volumetric ratio presents a nonlinear trend,with initial bond strength decreasing at low fiber content and increasing significantly as fiber content rises.Additionally,finite element(FE)simulations were applied to replicate the experimental conditions,and the outcomes showed strong correlation with the experimental data,confirming the exactitude of the FE model in predicting the bond behavior at the UHPC-Steel interface.These findings provide valuable insights for optimizing the design of UHPC-Filled steel tubes in high-performance structure.
基金Supported by the National Natural Science Foundation of China(12301101)the Guangdong Basic and Applied Basic Research Foundation(2022A1515110019 and 2020A1515110585)。
文摘In this paper,the Paley-Wiener theorem is extended to the analytic function spaces with general weights.We first generalize the theorem to weighted Hardy spaces Hp(0<p<∞)on tube domains by constructing a sequence of L^(1)functions converging to the given function and verifying their representation in the form of Fourier transform to establish the desired result of the given function.Applying this main result,we further generalize the Paley-Wiener theorem for band-limited functions to the analytic function spaces L^(p)(0<p<∞)with general weights.
文摘This study develops an analytical model to evaluate the cooling performance of a porous terracotta tubular direct evaporative heat and mass exchanger. By combining energy and mass balance equations with heat and mass transfer coefficients and air psychrometric correlations, the model provides insights into the impact of design and operational parameters on the exchanger cooling performance. Validated against an established numerical model, it accurately simulates cooling behavior with a Root Mean Square Deviation of 0.43 - 1.18˚C under varying inlet air conditions. The results show that tube geometry, including equivalent diameter, flatness ratio, and length significantly influences cooling outcomes. Smaller diameters enhance wet-bulb effectiveness but reduce cooling capacity, while increased flatness and length improve both. For example, extending the flatness ratio of a 15 mm diameter, 0.6 m long tube from 1 (circular) to 4 raises the exchange surface area from 0.028 to 0.037 m2, increasing wet-bulb effectiveness from 60% to 71%. Recommended diameters range from 5 mm for tubes under 0.5 m to 1 cm for tubes 0.5 to 1 m in length. Optimal air velocities depend on tube length: 1 m/s for tubes under 0.8 m, 1.5 m/s for lengths of 0.8 to 1.2 m, and up to 2 m/s for longer tubes. This model offers a practical alternative to complex numerical and CFD methods, with potential applications in cooling tower optimization for thermal and nuclear power plants and geothermal heat exchangers.
基金supported by the National Natural Science Foundation of China(Grant No.52475277)2022 Guangxi University Young and Middle-aged Teachers’Basic Research Ability Improvement Project(Grant No.2022KY0781)Scientific Research Funds of Guilin University of Aerospace Technology(Grant No.XJ22KT29).
文摘This research investigates the bending response of folded multi-celled tubes(FMTs)fabricated by folded metal sheets.A three-point bending test for FMTs with circular and square sections is designed and introduced.The base numerical models are correlated with physical experiments and a static crashworthiness analysis of six FMT configurations to assess their energy absorption characteristics.The influences of thickness,sectional shape,and load direction on the bending response are studied.Results indicate that increasing the thickness of the tube and radian of the inner tube enhances the crashworthiness performance of FMT,yielding a 20.50%increase in mean crushing force,a 55.53%increase in specific energy absorption,and an 18.05%decrease in peak crushing force compared to traditional multi-celled tubes(TMTs).A theoretical analysis of the specific energy absorption indicates that FMTs outperform TMTs,particularly when the peak crushing force is prominent.This study highlights the innovative and practical potential of FMTs to improve the crashworthiness of thin-walled structures.
基金Natural Science Foundation of Sichuan Province under Grant Nos.2022NSFSC0319 and 2022NSFSC0095the Science and Technology Research Projects of Mianyang,China under Grant No.15S-02-3。
文摘The behavior of reinforced concrete(RC)square columns strengthened with self-compacting concrete(SCC)-filled steel tubes under cyclic loading was experimentally investigated.Tests were carried out on eleven reinforced columns and one unreinforced column.The parameters studied for the strengthened columns included axial compression ratio,reinforcement rate,defect rate,strength of SCC,and the section form of a reinforced steel tube.The results show that the steel tube SCC reinforcement method can effectively strengthen RC columns,exert the restraint effect of steel tube,and delay the development of internal concrete cracks.The method can also significantly improve the bearing capacity of RC columns.Regarding ductility,the improvement of the reinforced column is obvious,the deformation resistance of the specimen is enhanced,and the degradation of stiffness and strength is relatively slow,indicating that it has good seismic performance.
文摘This pictorial review discusses the imaging approach to evaluate for proper placement or complications of pediatric gastrostomy tube(G-tube)placement and long-term use.G-tubes are crucial for long-term nutritional support in patients facing challenges with oral intake.The article depicts the role of imaging such as contrast radiography,fluoroscopy,ultrasound,and computed tomography scans for confirming G-tube position and evaluating complications,in addition to basic anatomical considerations and placement techniques.Complications discussed include malposition,intraperitoneal placement,buried bumper syndrome,and tube malfunction.Specific imaging techniques and checklists are provided to guide clinicians in assessing G-tube placement accurately.The latter half of the review is a comprehensive exploration of pearls and pitfalls of imaging when employed to detect complications to avoid false positives and negatives.
文摘BACKGROUND Esophageal cancer(EC)is an aggressive malignancy with low survival(10%-30%).Nutritional problems are present throughout the perioperative period and are key to prognosis.Home enteral nutrition appears to improve the nutritional status of patients with EC.Few studies have addressed the experience of patients administering their own nutritional fluids and managing their own feeding tubes at home.The aim of this study was to explore the real-life experience of self-management of feeding tubes in patients at home after EC surgery in the first 3 months after discharge following surgery.AIM To explore feeding tube self-management experience of patients at home 3 months after discharge following EC surgery.METHODS Face-to-face semi-structured interviews were conducted with 18 patients using a feeding tube at home after EC surgery.Thematic analysis of the recordings identified themes related to feeding tube self-management.RESULTS Patients expressed similar feelings about their tube management experiences concerning three contextualized themes:Self-management dilemmas,distressing experiences,and self-management facilitators.CONCLUSION There are many dilemmas and problems in self-managing feeding tubes in postoperative homebound patients with EC.Clinical staff should provide guidance to promote a positive change in self-management behavior.
基金support by the National Natural Science Foundation of China(No.22279047).
文摘The fabrication of one-dimensional metal/N-doped carbon materials has shown a promising prospect as efficient electrocata-lysts for oxygen reduction reaction(ORR).Herein,CoNi alloy nanoparticles anchored on N-doped carbon nanotubes(CoNi@NCNT)are prepared by a dual-template strategy,using polypyrrole(PPy)tubes and CoNi-based metal-organic framework as the precursors.The as-formed CoNi@NCNT catalyst displays a half-wave potential(0.83 V)as well as good durability under alkaline medium.The excellent electrocatalytic performance is ascribed to a synergistic coupling of hierarchically tubular structure,highly electronic conductivity,and abundantly alloy-type active sites.When the CoNi@NCNT catalyst is applied in zinc-air battery(ZAB),the device displays a stable charge-discharge cycling performance.The present work affords a useful approach to constructing alloy/nitrogen-incorporated carbon-aceous materials as bifunctional electrocatalysts for high-performance ZABs.
文摘In the anticorrosive coating line of a welded tube plant, the current status and existing problems of the medium-frequency induction heating equipment were discussed.Partial renovations of the power control cabinet have been conducted.Parameters such as the DC current, DC voltage, intermediate frequency power, heating temperature, and the positioning signal at the pipe end were collected.A data acquisition and processing system, which can process data according to user needs and provide convenient data processing functions, has been developed using LabVIEW software.This system has been successfully applied in the coating line for the automatic control of high-power induction heating equipment, production management, and digital steel tube and/or digital delivery.
基金part of the Agency for Defense Development(ADD)research project on Weapon lethality/effectiveness analysis technology for material targets and grant funded by the korean goverment(511225-912A03301)。
文摘This study presents a fragility curve to assess explosively induced damage to military vehicle tires based on shock tube experiments.To replicate lateral damage scenarios that may occur in real battlefield environments involving missile or bomb detonations,extreme overpressure conditions were generated using a shock tube.The influence of explosive charge mass on tire damage was quantitatively evaluated.Experimental results identified two critical failure thresholds:for loss of pressure,the threshold was 354 kPa peak overpressure and 3052 kPa·ms impulse;for rupture,the values were 485 kPa and 4237 kPa-ms,respectively.The same damage profile was reproduced through finite element analysis(FEA),verifying the reliability of the simulation.A Single Degree of Freedom(SDOF)model and Kingery-Bulmash(K-B)chart were employed to generate pressure-impulse data as a function of standoff distance.These data were applied to a finite element tire model using the BLAST ENHANCED keyword in LS-DYNA.The applied peak overpressures were identical to the experimental values with a 24%-27%difference in impulse.The simulation also captured recurring bead rim separation phenomenon,leading to internal pressure loss consistent with high-speed camera observations from the experiments.The resulting fragility curve clearly defines the threshold conditions for tire damage and provides a standardized damage assessment model applicable to various explosive charge masses and stand-off distances.The proposed model offers a quantitative basis for evaluating tire vulnerability,providing foundational reference data for defense applications.Specifically,the findings are expected to serve as a reliable source for weapon effects analysis and target vulnerability assessments involving wheeled military vehicles.
基金Supported by Jiangsu Provincial Administration of Traditional Chinese Medicine,No.MS2023017 and No.SLJ0311the Jiangsu Provincial Health Commission,No.ZDXK202251.
文摘BACKGROUND Gastroesophageal junction(GEJ)or gastrointestinal stromal tumor(GIST)are located in unfavorable parts of the stomach,due to the anatomical complexity of these regions,protecting the cardia while ensuring R0 resection is a major challenge for surgeons.CASE SUMMARY Two cases of GEJ stromal tumors were reported.Abdominal computed tomography scans revealed that both tumors were located at the GEJ,close to the posterior wall,with one tumor measuring greater than 5 cm.Both patients successfully underwent robot-assisted laparoscopic wedge resection of the stomach.The surgeries achieved R0 resection while preserving the cardia sphincter and maximizing gastric tissue preservation.Postoperatively,no symptoms such as gastroesophageal reflux or cardia stenosis were observed.Case 1:Postoperative pathology:GIST.Immunohistochemical results:Tumor cells were positive for CD34,CD117,and DOG1,and negative for SMA,desmin,S-100,and SDHB(normal expression).The Ki-67 proliferation index was approximately 5%.Case 2:Postoperative pathology:GIST.Immunohistochemical results:Tumor cells were positive for CD117(++),CD34(++),DOG1(+++),and focal positivity for SMA.Negative for desmin,S-100(few cells positive),and SDHB(preserved expression).The Ki-67 proliferation index was approximately 10%.CONCLUSION The gastric tube-guided robotic-assisted laparoscopic resection is a safe and effective method for tumor resection while preserving the cardia,and it is worth further promotion in clinical practice.
基金financially supported by the National Natural Science Foundation of China(No.22273080)Research Grants Council of Hong Kong(Nos.11313322 and 11307224)。
文摘Knotting occurs in polymers and affects polymer properties.Physical understanding of polymer knots is limited due to the complex confo rmational space of knotted structures.The knotting problem can be handled by the tube model,which assumes that knotted polymer segments are confined in a virtual tube.Recently,we quantified this virtual tube using a computational algorithm.The algorithm was limited to the simplest knot:3_(1)knot.It remains unclear how the tube model and computational algorithm are applied to more complex knots.In this work,we apply the tube model to 4_(1),5_(1),and 5_(2) knots,resulting in several findings.First,the computational algorithm developed for 3_(1) knot cannot be directly applied to 4_(1) knot.After modifying the algorithm,we quantify the tubes for 4_(1) knot.Second,we find that,for all four knot types,the knotcore region have less average bending energy density than unknotted regions when the chain bending stiffness is small.This counterintuitive result is explained by the tube model.Third,for all four knot types,polymer segments at the boundaries of knot cores adopt nearly straight conformations(almost zero bending)and exhibit lower local bending compared to other knot-core regions and unknotting regions.This local behavior is also consistent with prediction from the tube model.This counterintuitive result is also explained by the tube model.Fourth,for all four knot types,when a polymer has non-uniform bending stiffness,a knot prefers certain chain positions such that the knot boundary locates at one stiff segment.Overall,our work paves the way for applying the tube model to complex polymer knots and obtains many common results for different knot types,which can be useful in understanding many knotting systems,such as DNA knots in vivo.
基金supported by the National Natural Science Foundation of China(Grant No.12202441).
文摘In this study,we numerically investigate the rise of a Taylor bubble in a vertically oscillating round tube.The results show that increasing the oscillation frequency and amplitude reduces the bubble rise velocity,which is consistent with previously reported experimental findings.Analysis of the flow in the annular film region indicates that the influence of tube wall oscillations is minimal.This suggests that the effect of tube oscillations is essentially equivalent to that of an oscillating piston above the bubble,leading to a similar mechanism for bubble deceleration.Using a theoretical formula from the literature,we demonstrate that at sufficiently high frequencies,the amplitude of the tube velocity oscillations becomes the sole control parameter affecting bubble deceleration.This study enhances our understanding of Taylor bubble behavior in mechanically oscillating environments and provides useful insights into the design of control strategies for Taylor bubble motion in vertical slug flows.
基金supported by the National Natural Science Foundation of China(Grant NO.82071057,82101229)National Key Research and Development Program of China(Grant NO.2023YFC2508001)。
文摘Purpose:Acute otitis media caused by gram-negative bacteria is a common otological condition among pediatric patients.Eustachian tube dysfunction(ETD)plays a pivotal role in the delayed resolution of acute otitis media,whereas the precise contribution of SIRT3 in this mechanism remains uncertain.This study aims to reveal the involvement of SIRT3 in murine ETD induced by LPS.Results:Histological analysis showed no baseline differences in ET structure between WT and SIRT3 knockout(SIRT3-KO)mice.However,LPS exposure led to increased goblet cell proliferation and MUC5 AC mucus secretion in both genotypes,with SIRT3-KO exacerbating these effects.The SIRT3-KO group displayed reduced cilia length.Functionally,SIRT3-KO mice showed a significantly higher initial POP and decreased MCC compared to the WT group after LPS exposure.Additionally,the active clearance of negative pressure(ACNP)was significantly reduced in SIRT3-KO mice,indicating compromised ET function.Conclusions:SIRT3-KO increased resistance to ET opening in mice exposed to LPS,and this effect may be related to the upregulated MUC5 AC expression,the increased surface tension of the luminal fluid and the impaired MCC function in mice exposed to LPS.
基金the National Science Foundation of China(52071042)Chongqing Talent Plan(CQYC202003047)+1 种基金the Chongqing Natural Science Foundation Project of CSTB2021YCJH-BGZXM0148 and CSTB2023NSCQ-MSX0079the Open Fund of the National Key Laboratory of Advanced Design and Manufacturing Technology for Vehicle,Hunan University(Grant No.82315001)。
文摘Recently,there have been few reports on the hot extrusion process of magnesium(Mg)alloy square tubes.In this work,we introduce a novel hot extrusion process called tube continuous expanding shear extrusion(t CESE)to produce Mg alloy square tubes with heterogeneous structures.Compared to previously reported hot-extruded Mg alloy tubes,the tCESE samples exhibit simultaneous enhancements in both strength and ductility.The microstructure evolution during the t CESE process was analyzed in detail.It was found that the microstructure developed consecutively as a result of twinning-induced dynamic recrystallization(TDRX),discontinuous dynamic recrystallization(DDRX)and continuous dynamic recrystallization(CDRX)with different nucleation of new orientations,while static recrystallization(SRX)promoted the formation of heterogeneous structures.The strengthening mechanism in the t CESE samples was revealed by loading-unloading-reloading(LUR)tensile tests,viscoplastic self-consistent(VPSC)simulation and intermittent tensile tests.The improvement of the strength in the tCESE samples is attributed to the size refinement of the grains and the second-phases,and more importantly,to hetero-deformation induced(HDI)strengthening.The improvement of the ductility in the t CESE samples can be attributed to the significant increase in non-basal dislocations within the heterogeneous structures during tensile deformation.
基金supported by the National Major Scientific Research Instrument Development Projects(No.42127807)the National Natural Science Foundation of China(No.12105030)。
文摘Promoting the development of deep-sea mineral exploration instrumentation can help alleviate the global resource shortage faced by mankind.X-ray fluorescence(XRF)spectrometry has been widely used in the in situ analysis of deep-sea minerals owing to its fast analytical speed,nondestructive nature,and wide analytical range.This study focused on the structural safety and detection efficiency of X-ray fluorescence in situ measurement equipment under high pressure for deep-sea XRF analysis.This study first combined finite element analysis and experiments to design and optimize the structure of an X-ray probe tube required for deep-sea mineral exploration and to determine the Be window thickness to ensure stress safety.Subsequently,the Monte Carlo method was used to analyze and optimize the Be window thickness on the X-ray probe tube to improve the accuracy of the elemental analyses.Finally,the effect of seawater thickness between the transmitter outer tube and rock wall was also considered.The results show that based on ocean depth in different detection environments,Be windows with a thickness of 1.5 mm or 2.0 mm can be selected to improve the detection efficiency of the device while ensuring the structural safety of the instrument.According to the design features and detection requirements of the device,in deep-sea exploration of minerals with characteristic peak energies below 10 keV,the transmitter outer tube should be as close as possible to the rock wall inside the logging.When the characteristic peak energy of the minerals is more than 10 keV,the distance between the transmitter outer tube and rock wall inside the logging should be controlled to approximately 2 mm.This study provides feasible solutions for future deep-sea mineral resource development and a useful reference for elemental analysis of minerals in the deep-sea or other extreme working environments.
