Passively mode-locked 2-μm Tm:YAP laser with a double-wall carbon nanotube absorber

We report on a diode-pumped passively continuous wave （cw） mode-locked Tm：YAP laser with a double-wall carbon nanotube （DWCNT） absorber operating at a wavelength of 2023 nm for the first time, to the best our knowledge. The DWCNT absorber is fabricated on a hydrophilic quartz substrate by using the vertical evaporation technique. The output power is as high as 375 mW. A stable pulse train with a repetition rate of 72.26 MHz is generated with a highest single pulse energy of 5.2 μJ.

A Continuum Shell Model Including van derWaals Interaction for Free Vibrations of Double-Walled Carbon Nanotubes

This paper proposes the free vibration analysis of Double-Walled Carbon NanoTubes(DWCNTs).A continuum elastic three-dimensional shell model is used for natural frequency investigation of simply supported DWCNTs.The 3D shell method is compared with beam analyses to show the applicability limits of 1D beam models.The effect of van der Waals interaction between the two cylinders is shown for different Carbon NanoTube(CNT)lengths and vibration modes.Results give the van der Waals interaction effect in terms of frequency values.In order to apply the 3D shell continuum model,DWCNTs are defined as two concentric isotropic cylinders(with an equivalent thickness and Young modulus)which can be linked by means of the interlaminar continuity conditions or by means of an infinitesimal fictitious layer which represents the van der Waals interaction.

Diffusion Behaviour of Fe-Cu Interface of Copper Brazed Double-wall Steel Tubes

By means of electron probe(EPMA),scanning electron microscope(SEM),and optical microscope (QM),the diffusion behaviour on the Fe-Cu interface of copper brazed double-wall steel tubes and the microstructure of the diffusion layer have been investigated.There are three kinds of metallurgical bonds between copper plating layer and steel substrate: (1)the Cu diffusing into steel substrate along grain boundary of ferrite;(2)the Cu diffusion into grain bulk of ferrite: (3)the Fe diffusing into Cu layer.The copper brazed double-wall steel tubes are formed by the combination of the diffusions mentioned above and this is the reason for excellent mechanical and technological properties of the copper brazed double-wall steel tubes.

Properties of the incandescent light emitted from double-walled carbon nanotube filament

We have studied the radiation of a double-walled carbon nanotube （DWNT） filament with a length of 4.5 mm and a diameter of 10μm by applying an electric current through the filament. The DWNT filament starts emitting incandescent light at voltage U =6V. Emission spectra of the DWNT below temperature 1250K can well be fitted to those of the blackbody radiation. The intensity of the incandescent light shows an exponential dependence on the voltage applied on the DWNT filaments. The resistance of the DWNT filaments is very stable at high temperatures between 900 and 1250 K during the emission of light in the experiments.

Reasons and countermeasures for “marking problem” during the production of double-walled copper-brazed steel tubes

This study explores the reasons underlying the frequent appearance of ＂marking problem＂ during the production of double-walled copper-brazed steel tubes. To this end, we compared two types of copper-coated steel strips, of which one has almost no problem during production, whereas the other has higher number of incidences of ＂marking problem＂. We analyzed the chemical composition,mechanical properties,the cross-sectional metallographs, and surface quality of the trimmed edge in both types of specimen. After the roll forming process, the bonding condition between the steel layers of the tubes before and after brazing process has also been examined. Results indicate that the chemical composition and mechanical properties of the two kinds of strips are similar; however, the edge quality of the trimmed strips is significantly different. It is believed that the irregular shape of the edge portions in the strips will be more pronounced during the bevel treatment. Consequently, smooth and tight seams cannot be guaranteed by such uneven beveled edges,which lead to higher number of incidences of ＂marking problem＂ during production.

Pullout Behavior of Large-diameter Collapsed Double-walled Carbon Nanotubes

The pullout behavior of large-diameter collapsed double-walled carbon nanotubes（DWCNT） was studied by molecular dynamics simulations and compared with those in the circular cross-sectioned state. The pullout force-displacement curves of both are in good agreement with the same mean value of the pullout force during the steady pullout stage. The pullout force was mainly due to the formation of new surfaces; the friction between nested walls was negligible. The effects of different chiral combinations and inter-wall spacings on the pullout behavior for both section situations were investigated. The commensurate（zigzag/zigzag or armchair/armchair） bi-tube systems have a larger fluctuation in the pullout force. The smaller interspacing implies lower mean pullout force with stronger fluctuations.

Critical Length of Double-Walled Carbon Nanotubes Based Oscillators

The critical lengths of an oscillator based on double-walled carbon nanotubes(DWCNTs)are studied by energy minimization and molecular dynamics simulation.Van der Waals(vdW)potential energy in DWCNTs is shown to be changed periodically with the lattice matching of the inner and outer tubes by using atomistic models with energy minimization method.If the coincidence length between the inner and outer tubes is long enough,the restoring force cannot drive the DWCNT to slide over the vdW potential barrier to assure the DWCNT acts as an oscillator.The critical coincidence lengths of the oscillators are predicted by a very simple equation and then confirmed with energy minimization method for both the zigzag/zigzag system and the armchair/armchair system.The critical length of the armchair/armchair system is much larger than that of the zigzag/zigzag system.The vdW potential energy fluctuation of the armchair/armchair system is weaker than that of the zigzag/zigzag system.So it is easier to slide over the barrier for the armchair/armchair system.The critical lengths of zigzag/zigzag DWCNTbased oscillator are found increasing along with temperature,by molecular dynamics simulations.

Feeding tube self-management experience of patients at home after discharge following esophageal cancer surgery

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.

A Review of the Applications of Nanofluids and Related Hybrid Variants in Flat Tube Car Radiators

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.

Effect of pouring time on microstructure and mechanical properties of centrifugal cast Ti-46Al alloy tubes

The grain size of TiAl alloy castings prepared by traditional casting process is coarse,thus showing poor mechanical properties.In this study,a new type of high performance Ti-46Al alloy tube prepared by vacuum centrifugal casting technology was introduced.This research comprehensively examined the influence of pouring time on the microstructure and mechanical performance of the castings,employing both experimental approaches and ProCast simulation methodologies.The findings indicate that prolonging the pouring time facilitates a microstructural evolution from coarse columnar grains to refined equiaxed grains.Under the condition of pouring temperature of 1,600℃,rotation speed of 800 r·min^(-1) and pouring time of 6 s,the tensile strength of Ti-46Al alloy at room temperature reaches 650 MPa,and the tensile strength at 800℃ reaches 705 MPa,which is significantly higher than that of traditional as-cast Ti-Al alloy.

Experimental and Numerical Study of Bonding Capacity of Interface between Ultra-High Performance Concrete and Steel Tube

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.

Experimental Study and Numerical Simulation of Hypervelocity Projectile Impact on Double-Wall Structure

Tests of hypervelocity projectile impact on double-wall structure were performed with the front wall ranging from 0.5 mm to 2.0 mm thick and different impact velocities. Smooth particle hydrodynamics (SPH) code in LS-DYNA was employed for the simulation of hypervelocity impact on the double-wall structure. By using elementary shock wave theory, the experimental results above are analyzed. The analysis can provide an explanation for the penetration mechanism of hypervelocity projectile impact on double-wall structure about the effect of front wall thickness and impact velocity..

Consecutive hybrid mechanism boosting Na+storage performance of dual-confined SnSe2 in N,Se-doping double-walled hollow carbon spheres

Rationally designed hierarchical structures and heteroatomic doping of carbon are effective strategies to enhance the stability and electrical conductivity of materials.Herein,SnSe_(2)flakes were generated in the double-walled hollow carbon spheres(DWHCSs),in which N and Se atoms were doped in the carbon walls,to construct SnSe_(2)@N,Se-DWHCSs by confined growth and in-situ derivatization.The N and Sedoped DWHCSs can effectively limit the size increase of SnSe_(2),promote ion diffusion kinetics,and buffer volume expansion,which can be proved by electron microscope observation and density functional theory calculation.Consequently,the SnSe_(2)@N,Se-DWHCSs as an anode material for sodium ion batteries(SIBs)demonstrated a distinguished reversible capacity of 322.8 mAh g^(-1)at 5 A g^(-1)after 1000 cycles and a superior rate ability of 235.3 m Ah g^(-1)at an ultrahigh rate of 15 A g^(-1).Furthermore,the structure evolution and electrochemical reaction processes of SnSe2@N,Se-DWHCSs in SIBs were analyzed by exsitu methods,which confirmed the consecutive hybrid mechanism and the phase transition process.

Study on the low mechanical anisotropy of extruded Mg-Zn-Mn-Ce-Ca alloy tube in the compression process

In this study,the extruded Mg-Zn-Mn-Ce-Ca alloy tube with a low compression anisotropy along the ED,45ED and TD was prepared.The effect of the second phases,initial texture and deformation behavior on this low mechanical anisotropy was investigated.The results revealed that the alloy tube contains the high content(Mg1-xZnx)11Ce phase and the low content of Mg12Ce phase.These second phases are respectively incoherent and coherent with the Mg matrix,and their influence can be ignored.Additionally,the alloy tube exhibited a weak basal fiber texture,where the c-axis was aligned along the 0°∼30°tilt from TD to ED.Such a texture made the initial deformation(at 1.0%∼1.6%strain)of the three samples controlled by comparable basalslip.As deformation progressed(1.6∼9.0%strain),larger amounts of ETWs nucleated and gradually approached saturation in the three samples,re-orienting the c-axis to a 0°∼±30°deviation with respect to the loading directions.Meanwhile,the prismatic and pyramidal<c+a>slips replaced the dominant deformation progressively until fracture.Eventually,the similar deformation mechanisms determined by the weak initial texture in the three samples contribute to the comparable strain hardening rates,resulting in the low compressive anisotropy of the alloy tube.

Experimental Investigation on Space-dispersed Double-wall Jet Combustion System for DI Diesel Engine

A space-dispersed double-wall jet combustion system was developed by adopting the wall-guiding spray method and the stratification theory.The experimental test was carried out to optimize the structural parameters of the diesel-engine combustion system,including chamber structure,swirl ratio of cylinder head,included angle of jet orifice,number and diameter of jet orifice,fuel injection pressure and timing.The effect of double-wall jet combustion system on combustion and engine performance was tested to obtain the best performance indexes,and the double-wall jet combustion system was compared to the prototype.The results show that NOx is reduced from 712 PPm to 487 PPm at 2 100 r/min,and from 593 PPm to 369 PPm at 3 000 r/min,which are reduced by 31.6% and 37.7%,respectively.The smoke intensity was reduced form 3.67 BSU to 2.1 BSU,and the oil consumption was reduced from 240.5 g/(kW·h) to 225.4 g/(kW·h),which was decreased by 6.3% at low speed.The pressure in the cylinder was obviously reduced from 115 bar to 108 bar,which was reduced by 6%.

A comprehensive review of lunar lava tube base construction and field research on a potential Earth test site

The Moon,as the closest celestial body to the Earth,plays a pivotal role in the progression of deep space exploration,and the establishment of research outposts on its surface represents a crucial step in this mission.Lunar lava tubes are special underground caves formed by volcanic eruptions and are considered as ideal natural shelters and scientific laboratories for lunar base construction.This paper begins with an in-depth overview of the geological origins,exploration history,and distribution locations of lunar lava tubes.Subsequently,it delves into the presentation of four distinctive advantages and typical concepts for constructing bases within lava tubes,summarizing the ground-based attempts made thus far in lunar lava tube base construction.Field studies conducted on a lava tube in Hainan revealed rock compositions similar to those found during the Apollo missions and clear lava tube structures,making it a promising analog site.Lastly,the challenges and opportunities encountered in the field of geotechnical engineering regarding the establishment of lunar lava tube bases are discussed,encompassing cave exploration technologies,in-situ testing methods,geomechanical properties under lunar extreme environments,base design and structural stability assessment,excavation and reinforcement techniques,and simulated Earth-based lava tube base.

Sandwich structures with tapered tubes as core:A quasi-static investigation

In this article,the experimental and finite element analysis is utilized to investigate the quasi-static compression features of sandwich constructions built with tapered tubes.3D printing technology was utilized to create the hollow centers of the tapering tubes,with and without corrugations.The results demonstrate that the energy absorption(EA)and specific energy absorption(SEA)of the single corrugated tapered tube sandwich are 51.6% and 19.8% higher,respectively,than those of the conical tube sandwich.Furthermore,the results demonstrate that energy absorbers can benefit from corrugation in order to increase their efficiency.Additionally,the tapered corrugated tubes'resistance to oblique impacts was studied.Compared to a straight tube,the tapered tube is more resistant to oblique loads and has a lower initial peak crushing force(PCF),according to numerical simulations.After conducting a parametric study,it was discovered that the energy absorption performance of the sandwich construction is significantly affected by the amplitude,number of corrugations,and wall thickness.EA and SEA of DTS with corrugation number of 8 increased by 17.4%and 29.6%,respectively,while PCF decreased by 9.2% compared to DTS with corrugation number of 10.

Nasogastric tube syndrome:A Meta-summary of case reports

BACKGROUND Since its description in 1790 by Hunter,the nasogastric tube(NGT)is commonly used in any healthcare setting for alleviating gastrointestinal symptoms or enteral feeding.However,the risks associated with its placement are often underes-timated.Upper airway obstruction with a NGT is an uncommon but potentially life-threatening complication.NGT syndrome is characterized by the presence of an NGT,throat pain and vocal cord(VC)paralysis,usually bilateral.It is poten-tially life–threatening,and early diagnosis is the key to the prevention of fatal upper airway obstruction.However,fewer cases may have been reported than might have occurred,primarily due to the clinicians'unawareness.The lack of specific signs and symptoms and the inability to prove temporal relation with NGT insertion has made diagnosing the syndrome quite challenging.AIM To review and collate the data from the published case reports and case series to understand the possible risk factors,early warning signs and symptoms for timely detection to prevent the manifestation of the complete syndrome with life-threatening airway obstruction.METHODS We conducted a systematic search for this meta-summary from the database of PubMed,EMBASE,Reference Citation Analysis(https://www.referencecitation-analysis.com/)and Google scholar,from all the past studies till August 2023.The search terms included major MESH terms"Nasogastric tube","Intubation,Gastrointestinal","Vocal Cord Paralysis",and“Syndrome”.All the case reports and case series were evaluated,and the data were extracted for patient demographics,clinical symptomatology,diagnostic and therapeutic interventions,clinical course and outcomes.A datasheet for evaluation was further prepared.RESULTS Twenty-seven cases,from five case series and 13 case reports,of NGT syndrome were retrieved from our search.There was male predominance(17,62.96%),and age at presentation ranged from 28 to 86 years.Ten patients had diabetes mellitus(37.04%),and nine were hypertensive(33.33%).Only three(11.11%)patients were reported to be immunocompromised.The median time for developing symptoms after NGT insertion was 14.5 d(interquartile range 6.25-33.75 d).The most commonly reported reason for NGT insertion was acute stroke(10,37.01%)and the most commonly reported symptoms were stridor or wheezing 17(62.96%).In 77.78%of cases,bilateral VC were affected.The only treatment instituted in most patients(77.78%)was removing the NG tube.Most patients(62.96%)required tracheostomy for airway protection.But 8 of the 23 survivors recovered within five weeks and could be decannulated.Three patients were reported to have died.CONCLUSION NGT syndrome is an uncommon clinical complication of a very common clinical procedure.However,an under-reporting is possible because of misdiagnosis or lack of awareness among clinicians.Patients in early stages and with mild symptoms may be missed.Further,high variability in the presentation timing after NGT insertion makes diagnosis challenging.Early diagnosis and prompt removal of NGT may suffice in most patients,but a significant proportion of patients presenting with respiratory compromise may require tracheostomy for airway protection.

Analysis of impact pressure,rock-breaking effect,and ground vibration induced by the disposable CO_(2)fracturing tube

The technology of expansion fracturing with liquid CO_(2)(EFLCO_(2))has attracted increasing attention due to reduced vibration and damage.The disposable fracturing tube has been developed and is gradually replacing the Cardox tube.However,there is a lack of impact pressure testing of disposable tubes under real working conditions,selection of gas explosion design parameters,and systematic analysis of blasting vibration.This limitation has constrained the widespread application of disposable fracturing tubes in engineering.A joint monitoring of the pressure-time curves in the disposable tubes and boreholes was conducted.The rock-breaking effect of varying hole spacing parameters in the EFLCO_(2)design was analyzed,and a systematic study was carried out on the vibration peak value,frequency,and energy characteristics.The results show that(1)the pressure distribution characteristics,stress peak value,and duration in the disposable tubes are different from those of Cardox tubes,which show multi-peak distribution,low-pressure peak value,and short duration.The correlation between the pressure in the disposable tube,filling pressure,and liquid CO_(2)weight is established,and a theoretical calculation method for the borehole wall pressure is proposed;(2)The hole spacing in rocks of different hardness is suggested;and(3)At the same scale distance,the peak particle velocity(PPV)caused by EFLCO_(2)(PPVCO_(2))is significantly smaller than that caused by blasting(PPVexplosive).The ratio of PPVexplosive to PPVCO_(2)is a power function related to scale distance,and a distance-related zonality exist in this relationship.The frequency composition of the vibration signal caused by EFLCO_(2)is relatively simple with a narrow frequency band.Its PPV and energy are mainly concentrated in the low-frequency band.This research contributes to the optimization of disposable fracturing tubes,gas explosion design,and vibration hazard control.

Enhanced performance of solution-processed carbon nanotube transparent electrodes in foldable perovskite solar cells through vertical separation of binders by using eco-friendly parylene substrate

The successful utilization of an eco-friendly and biocompatible parylene-C substrate for high-performance solution-processed double-walled carbon nanotube(CNT)electrode-based perovskite solar cells(PSCs)was demonstrated.Through the use of a novel inversion transfer technique,vertical separation of the binders from the CNTs was induced,rendering a stronger p-doping effect and thereby a higher conductivity of the CNTs.The resulting foldable devices exhibited a power conversion efficiency of 18.11%,which is the highest reported among CNT transparent electrode-based PSCs to date,and withstood more than 10,000 folding cycles at a radius of 0.5 mm,demonstrating unprecedented mechanical stability.Furthermore,solar modules were fabricated using entirely laser scribing processes to assess the potential of the solution-processable nanocarbon electrode.Notably,this is the only one to be processed entirely by the laser scribing process and to be biocompatible as well as eco-friendly among the previously reported nonindium tin oxide-based perovskite solar modules.