Harness High-Temperature Thermal Energy via Elastic Thermoelectric Aerogels

Despite notable progress in thermoelectric(TE)materials and devices,developing TE aerogels with high-temperature resistance,superior TE performance and excellent elasticity to enable self-powered high-temperature monitoring/warning in industrial and wearable applications remains a great challenge.Herein,a highly elastic,flame-retardant and high-temperature-resistant TE aerogel,made of poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate)/single-walled carbon nanotube(PEDOT:PSS/SWCNT)composites,has been fabricated,displaying attractive compression-induced power factor enhancement.The as-fabricated sensors with the aerogel can achieve accurately pressure stimuli detection and wide temperature range monitoring.Subsequently,a flexible TE generator is assembled,consisting of 25 aerogels connected in series,capable of delivering a maximum output power of 400μW when subjected to a temperature difference of 300 K.This demonstrates its outstanding high-temperature heat harvesting capability and promising application prospects for real-time temperature monitoring on industrial high-temperature pipelines.Moreover,the designed self-powered wearable sensing glove can realize precise wide-range temperature detection,high-temperature warning and accurate recognition of human hand gestures.The aerogel-based intelligent wearable sensing system developed for firefighters demonstrates the desired self-powered and highly sensitive high-temperature fire warning capability.Benefitting from these desirable properties,the elastic and high-temperature-resistant aerogels present various promising applications including self-powered high-temperature monitoring,industrial overheat warning,waste heat energy recycling and even wearable healthcare.

Synergistic effect of Zr and Mo on precipitation and high-temperature properties of Al-Si-Cu-Mg alloys

This study focuses on finding a solution to the sharp decline in mechanical properties of Al-Si-Cu-Mg alloys due to rapid coarsening of traditional intermediate phases at high temperature.A new type of modified al oy,to be used in automobile engines at high temperatures,was prepared by adding Zr and Mo into Al-Si-Cu-Mg alloy.The synergistic effects of Zr and Mo on the microstructure evolution and high-temperature mechanical properties were studied.Results show that the addition of Zr and Mo generates a series of intermetallic phases dispersed in the alloy.They can improve the strength of the alloy by hindering dislocation movement and crack propagation.In addition,some nano-strengthened phases show coherent interfaces with the matrix and improve grain refinement.The addition of Mo greatly improves the heat resistance of the alloy.The extremely low diffusivity of Mo enables it to improve the thermal stability of the intermetallic phases,inhibit precipitation during aging,reduce the size of the precipitates,and improve the heat resistance of the alloy.

HZSM-5 zeolites undergoing the high-temperature process for boosting the bimolecular reaction in n-heptane catalytic cracking

High-temperature treatment is key to the preparation of zeolite catalysts.Herein,the effects of hightemperature treatment on the property and performance of HZSM-5 zeolites were studied in this work.X-Ray diffraction,N2physisorption,27Al magic angle spinning nuclear magnetic resonance(MAS NMR),and temperature-programmed desorption of ammonia results indicated that the hightemperature treatment at 650℃ hardly affected the inherent crystal and texture of HZSM-5zeolites but facilitated the conversion of framework Al to extra-framework Al,reducing the acid site and enhancing the acid strength.Moreover,the high-temperature treatment improved the performance of HZSM-5 zeolites in n-heptane catalytic cracking,promoting the conversion and light olefins yield while inhibiting coke formation.Based on the kinetic and mechanism analysis,the improvement of HZSM-5 performance caused by high-temperature treatment has been attributed to the formation of extra-framework Al,which enhanced the acid strength,facilitated the bimolecular reaction,and promoted the entropy change to overcome a higher energy barrier in n-heptane catalytic cracking.

Sacrificial piles as a countermeasure against local scour around underwater pipelines

Local scour around pipelines crossing rivers or in marine environments is a significant concern.It can lead to failure of the pipelines resulting in environmental side effects and economic losses.This study developed an experimental method to reduce local scour around pipelines with a steady flow of clear water by installing cylindrical and cubical sacrificial piles.Three sizes of sacrificial piles were examined in a linear arrangement.Sacrificial piles were installed on the upstream side of the pipeline at three distances.Maximum scour depth reduction rates below the pipeline were computed.The results showed that sacrificial piles could protect a pipeline from local scour.A portion of scoured sediment around the sacrificial piles was deposited beneath the pipeline.This sediment accumulation reduced the scour depth beneath the pipeline.Analysis of the experimental results demonstrated that the size of piles(d),the spacing between piles,and the distance between the pipe and piles(Xp)were the variables that reduced the maximum scour beneath the pipeline with a diameter of D.For the piles with d=0.40D and 0.64D,X_(p)=4OD was the optimal distance to install a group of piles,and cubical piles could mitigate scour more effectively than cylindrical piles under similar conditions.For the piles with d=D,the greatest reduction in scour depth was achieved at X_(p)=50D with any desired spacings between piles,and cylindrical piles in this dimension could protect the pipeline against scour more effectively than cubical piles.

Novel Method for Evaluating the Aging of Aviation Turbine Engine Oils via High-Temperature Bearing Deposit Tests

Aviation turbine engine oils require excellent thermal-oxidative stability because of their high-temperature environments.High-temperature bearing deposit testing is a mandatory method for measuring the thermal-oxidative performance of aviation lubricant oils,and the relevant apparatus was improved in the present study.Two different commercial aviation turbine engine oils were tested,one with standard performance(known as the SL oil)and the other with high thermal stability,and their thermal-oxidative stability characteristics were evaluated.After 100 h of high-temperature bearing testing,the SL oil was analyzed by using various analytical techniques to investigate its thermal-oxidative process in the bearing test,with its thermal-oxidative degradation mechanism also being discussed.The results indicate that the developed high-temperature bearing apparatus easily meets the test requirements of method 3410.1 in standard FED-STD-791D.The viscosity and total acid number(TAN)of the SL oil increased with the bearing test time,and various deposits were produced in the bearing test,with the micro-particles of the carbon deposits being sphere-like,rod-like,and sheet-like in appearance.The antioxidant additives in the oil were consumed very rapidly in the first 30 h of the bearing test,with N-phenyl-1-naphthylamine being consumed faster than dioctyldiphenylamine.Overall,the oil thermal-oxidative process involves very complex physical and chemical mechanisms.

SDH-FCOS:An Efficient Neural Network for Defect Detection in Urban Underground Pipelines

Urban underground pipelines are an important infrastructure in cities,and timely investigation of problems in underground pipelines can help ensure the normal operation of cities.Owing to the growing demand for defect detection in urban underground pipelines,this study developed an improved defect detection method for urban underground pipelines based on fully convolutional one-stage object detector(FCOS),called spatial pyramid pooling-fast(SPPF)feature fusion and dual detection heads based on FCOS(SDH-FCOS)model.This study improved the feature fusion component of the model network based on FCOS,introduced an SPPF network structure behind the last output feature layer of the backbone network,fused the local and global features,added a top-down path to accelerate the circulation of shallowinformation,and enriched the semantic information acquired by shallow features.The ability of the model to detect objects with multiple morphologies was strengthened by introducing dual detection heads.The experimental results using an open dataset of underground pipes show that the proposed SDH-FCOS model can recognize underground pipe defects more accurately;the average accuracy was improved by 2.7% compared with the original FCOS model,reducing the leakage rate to a large extent and achieving real-time detection.Also,our model achieved a good trade-off between accuracy and speed compared with other mainstream methods.This proved the effectiveness of the proposed model.

High-performance and robust high-temperature polymer electrolyte membranes with moderate microphase separation by implementation of terphenyl-based polymers

Acid loss and plasticization of phosphoric acid(PA)-doped high-temperature polymer electrolyte membranes(HT-PEMs)are critical limitations to their practical application in fuel cells.To overcome these barriers,poly(terphenyl piperidinium)s constructed from the m-and p-isomers of terphenyl were synthesized to regulate the microstructure of the membrane.Highly rigid p-terphenyl units prompt the formation of moderate PA aggregates,where the ion-pair interaction between piperidinium and biphosphate is reinforced,leading to a reduction in the plasticizing effect.As a result,there are trade-offs between the proton conductivity,mechanical strength,and PA retention of the membranes with varied m/p-isomer ratios.The designed PA-doped PTP-20m membrane exhibits superior ionic conductivity,good mechanical strength,and excellent PA retention over a wide range of temperature(80–160°C)as well as satisfactory resistance to harsh accelerated aging tests.As a result,the membrane presents a desirable combination of performance(1.462 W cm^(-2) under the H_(2)/O_(2)condition,which is 1.5 times higher than that of PBI-based membrane)and durability(300 h at 160°C and 0.2 A cm^(-2))in the fuel cell.The results of this study provide new insights that will guide molecular design from the perspective of microstructure to improve the performance and robustness of HT-PEMs.

Numerical study on local scour characteristics around submarine pipelines in the Yellow River Delta silty sandy soil under waves and currents

Due to their high reliability and cost-efficiency,submarine pipelines are widely used in offshore oil and gas resource engineering.Due to the interaction of waves,currents,seabed,and pipeline structures,the soil around submarine pipelines is prone to local scour,severely affecting their operational safety.With the Yellow River Delta as the research area and based on the renormalized group(RNG)k-εturbulence model and Stokes fifth-order wave theory,this study solves the Navier-Stokes(N-S)equation using the finite difference method.The volume of fluid(VOF)method is used to describe the fluid-free surface,and a threedimensional numerical model of currents and waves-submarine pipeline-silty sandy seabed is established.The rationality of the numerical model is verified using a self-built waveflow flume.On this basis,in this study,the local scour development and characteristics of submarine pipelines in the Yellow River Delta silty sandy seabed in the prototype environment are explored and the influence of the presence of pipelines on hydrodynamic features such as surrounding flow field,shear stress,and turbulence intensity is analyzed.The results indicate that(1)local scour around submarine pipelines can be divided into three stages:rapid scour,slow scour,and stable scour.The maximum scour depth occurs directly below the pipeline,and the shape of the scour pits is asymmetric.(2)As the water depth decreases and the pipeline suspension height increases,the scour becomes more intense.(3)When currents go through a pipeline,a clear stagnation point is formed in front of the pipeline,and the flow velocity is positively correlated with the depth of scour.This study can provide a valuable reference for the protection of submarine pipelines in this area.

Integrated multi-scale approach combining global homogenization and local refinement for multi-field analysis of high-temperature superconducting composite magnets

Second-generation high-temperature superconducting(HTS)conductors,specifically rare earth-barium-copper-oxide(REBCO)coated conductor(CC)tapes,are promising candidates for high-energy and high-field superconducting applications.With respect to epoxy-impregnated REBCO composite magnets that comprise multilayer components,the thermomechanical characteristics of each component differ considerably under extremely low temperatures and strong electromagnetic fields.Traditional numerical models include homogenized orthotropic models,which simplify overall field calculation but miss detailed multi-physics aspects,and full refinement(FR)ones that are thorough but computationally demanding.Herein,we propose an extended multi-scale approach for analyzing the multi-field characteristics of an epoxy-impregnated composite magnet assembled by HTS pancake coils.This approach combines a global homogenization(GH)scheme based on the homogenized electromagnetic T-A model,a method for solving Maxwell's equations for superconducting materials based on the current vector potential T and the magnetic field vector potential A,and a homogenized orthotropic thermoelastic model to assess the electromagnetic and thermoelastic properties at the macroscopic scale.We then identify“dangerous regions”at the macroscopic scale and obtain finer details using a local refinement(LR)scheme to capture the responses of each component material in the HTS composite tapes at the mesoscopic scale.The results of the present GH-LR multi-scale approach agree well with those of the FR scheme and the experimental data in the literature,indicating that the present approach is accurate and efficient.The proposed GH-LR multi-scale approach can serve as a valuable tool for evaluating the risk of failure in large-scale HTS composite magnets.

Pipeline Flex血流导向装置治疗颅内动脉瘤疗效观察

目的观察使用Pipeline Flex血流导向装置(PED)治疗颅内动脉瘤的疗效及安全性。方法回顾性分析2020年6月至2022年6月中山市人民医院使用PED治疗的25例颅内动脉瘤(共29个动脉瘤)患者的临床资料,25例患者中2例存在2个串联动脉瘤,1例有3个串联动脉瘤。29个动脉瘤分布在颈内动脉26个,大脑中动脉1个,椎基底动脉2个。术后进行临床及影像学随访,评估术后即刻动脉瘤栓塞情况和出院时患者改良Rankin评分量表(mRS),并在术后6个月及12个月时随访进行影像学检查以明确动脉瘤闭塞情况。结果25例患者均成功置入PED,其中15个动脉瘤联合弹簧圈栓塞,14个动脉瘤单独置入PED支架。术中有1例使用球囊扩张,24例经导丝微导管按摩均贴壁良好,术后临床随访中1例(4%)患者有缺血症状。术后6个月随访22个(75.9%)动脉瘤完全闭合,术后12个月随访2个(6.9%)动脉瘤影像学随访中未见闭合,27个(93.1%)动脉瘤完全闭合。结论PED治疗颅内动脉瘤短期随访安全有效,并发症较少,动脉瘤闭塞率较高。

Research on the impact of high-temperature aging on the thermal safety of lithium-ion batteries

Understanding the thermal safety evolution of lithium-ion batteries during high-temperature usage conditions bears significant implications for enhancing the safety management of aging batteries.This work investigates the thermal safety evolution mechanism of lithium-ion batteries during high-temperature aging.Similarities arise in the thermal safety evolution and degradation mechanisms for lithium-ion batteries undergoing cyclic aging and calendar aging.Employing multi-angle characterization analysis,the intricate mechanism governing the thermal safety evolution of lithium-ion batteries during high-temperature aging is clarified.Specifically,lithium plating serves as the pivotal factor contributing to the reduction in the self-heating initial temperature.Additionally,the crystal structure of the cathode induced by the dissolution of transition metals and the reductive gas generated during aging attacking the crystal structure of the cathode lead to a decrease in thermal runaway triggering temperature.Furthermore,the loss of active materials and active lithium during aging contributes to a decline in both the maximum temperature and the maximum temperature rise rate,ultimately indicating a decrease in the thermal hazards of aging batteries.

Seasonal Prediction of Extreme High-Temperature Days in Southwestern China Based on the Physical Precursors

Extreme high temperatures frequently occur in southwestern China,significantly impacting the local ecological system and economic development.However,accurate prediction of extreme high-temperature days(EHDs)in this region is still an unresolved challenge.Based on the spatiotemporal characteristics of EHDs over China,a domain-averaged EHD index over southwestern China(SWC-EHDs)during April-May is defined.The simultaneous dynamic and thermodynamic fields associated with the increased SWC-EHDs are a local upper-level anticyclonic(high-pressure)anomaly and wavy geopotential height anomaly patterns over Eurasia.In tracing the origins of the lower boundary anomalies,two physically meaningful precursors are detected for SWC-EHDs.They are the tripolar SST change tendency from December-January to February-March in the northern Atlantic and the February-March mean snow depth in central Asia.Using these two selected predictors,a physics-based empirical model prediction was applied to the training period of 1961–2005 to obtain a skillful prediction of the EHDs index,attaining a correlation coefficient of 0.76 in the independent prediction period(2006–19),suggesting that 58%of the total SWC-EHDs variability is predictable.This study provides an estimate for the lower bound of the seasonal predictability of EHDs as well as for the hydrological drought over southwestern China.

Comparative investigation of microstructure and high-temperature oxidation resistance of high-velocity oxy-fuel sprayed CoNiCrAlY/nano-Al_(2)O_(3) composite coatings using satellited powders

Satellited CoNiCrAlY–Al_(2)O_(3)feedstocks with 2wt%, 4wt%, and 6wt% oxide nanoparticles and pure CoNiCrAlY powder were deposited by the high-velocity oxy fuel process on an Inconel738 superalloy substrate. The oxidation test was performed at 1050℃ for 5, 50, 100,150, 200, and 400 h. The microstructure and phase composition of powders and coatings were characterized by scanning electron microscopy and X-ray diffraction, respectively. The bonding strength of the coatings was also evaluated. The results proved that with the increase in the percentage of nanoparticles(from 2wt% to 6wt%), the amount of porosity(from 1vol% to 4.7vol%), unmelted particles, and roughness of the coatings(from 4.8 to 8.8 μm) increased, and the bonding strength decreased from 71 to 48 MPa. The thicknesses of the thermally grown oxide layer of pure and composite coatings(2wt%, 4wt%, and 6wt%) after 400 h oxidation were measured as 6.5, 5.5, 7.6, and 8.1 μm, respectively.The CoNiCrAlY–2wt% Al_(2)O_(3)coating showed the highest oxidation resistance due to the diffusion barrier effect of well-dispersed nanoparticles. The CoNiCrAlY–6wt% Al_(2)O_(3)coating had the lowest oxidation resistance due to its rough surface morphology and porous microstructure.

Study on the effect of thermal deformation on the liquid seal of high-temperature molten salt pump in molten salt reactor

The high-temperature molten salt pump is the core equipment in a molten salt reactor that drives the flow of the molten salt coolant.Rotor stability is key to the continuous and reliable operation of the molten salt pump,and the liquid seal at the wear ring can affect the dynamic characteristics of the rotor system.When the molten salt pump is operated in the hightemperature molten salt medium,thermal deformation of the submerged parts inevitably occurs,changing clearance between the stator and rotor,affecting the leakage and dynamic characteristics of the seal.In this study,the seal leakage,seal dynamic characteristics,and rotor system dynamic characteristics are simulated and analyzed using finite element simulation software based on two cases of considering the effect of seal thermal deformation effect or not.The results show a significant difference in the leakage characteristics and dynamic characteristics of the seal obtained by considering the effect of seal thermal deformation and neglecting the effect of thermal deformation.The leakage flow rate decreases,and the first-order critical speed of the seal-bearing-rotor system decrease after considering the seal’s thermal deformation.

High-temperature stress suppresses allene oxide cyclase 2 and causes male sterility in cotton by disrupting jasmonic acid signaling

Cotton(Gossypium spp.) yield is reduced by stress. In this study, high temperature(HT) suppressed the expression of the jasmonic acid(JA) biosynthesis gene allene oxide cyclase 2(GhAOC2), reducing JA content and causing male sterility in the cotton HT-sensitive line H05. Anther sterility was reversed by exogenous application of methyl jasmonate(MeJA) to early buds. To elucidate the role of GhAOC2 in JA biosynthesis and identify its putative contribution to the anther response to HT, we created gene knockout cotton plants using the CRISPR/Cas9 system. Ghaoc2 mutant lines showed male-sterile flowers with reduced JA content in the anthers at the tetrad stage(TS), tapetum degradation stage(TDS), and anther dehiscence stage(ADS). Exogenous application of MeJA to early mutant buds(containing TS or TDS anthers) rescued the sterile pollen and indehiscent anther phenotypes, while ROS signals were reduced in ADS anthers. We propose that HT downregulates the expression of GhAOC2 in anthers, reducing JA biosynthesis and causing excessive ROS accumulation in anthers, leading to male sterility. These findings suggest exogenous JA application as a strategy for increasing male fertility in cotton under HT.

A 3–5μm broadband YBCO high-temperature superconducting photonic crystal

Photonic crystal structures have excellent optical properties,so they are widely studied in conventional optical materials.Recent research shows that high-temperature superconducting periodic structures have natural photonic crystal features and they are favourable candidates for single-photon detection.Considering that superconductors have completely different properties from conventional optical materials,we study the energy level diagram and mid-infrared 3μm–5μm transmission spectrum of two-dimensional superconducting photonic crystals in both superconducting and quenched states with the finite element method.The energy level diagram of the circular crystal column superconducting structure shows that the structure has a large band gap width in both states.At the same fill factor,the circular crystal column superconducting structure has a larger band gap width than the others structures.For lattice structures,the zero transmission point of the square lattice structure is robust to the incident angle and environmental temperature.Our research has guiding significance for the design of new material photonic crystals,photon modulation and detection.

Enhancement of the Mechanical Performance of SiCf/Phenolic Composites after High-temperature Pyrolysis Using ZrC/B_(4)C Particles

The composites were prepared by modifying silicon carbide fiber with particles of zirconium carbide(ZrC)and boron carbide(B_(4)C)and incorporating them into a phenolic resin matrix.The influence of ZrC and B_(4)C on the mechanical performance of SiCf/phenolic composites after high-temperature pyrolysis was studied through flexural performance test.The results show that the composite material has good thermal stability and high-temperature mechanical properties.After static ablation at 1400℃ for 15 minutes,the flexural strength of the composite material reaches 286 MPa,which is still 7.3%higher than at room temperature,indicating that the composite material still has good mechanical properties even after heat treatment at 1400℃.

Natural aging mechanism of buried polyethylene pipelines during long-term service

Currently,accelerated aging tests are widely used to study the aging process of polyethylene pipelines.However,this approach can only simulate one or several main influencing factors in the natural environment,which are often quite different from the actual environment of the buried pipelines.In this study,five types of PE80 buried pipelines in service for 9e18 years were taken as the research object,while new PE80 pipelines were taken as the reference group.The aging process and mechanism of polyethylene buried pipelines were studied through mechanical and chemical property tests and microstructural analysis.The results showed that the pipeline exhibited cross-linking as the main aging mechanism after being in service for 0e18 years.The aging degree and law of the inner and outer surface of the pipeline were compared,and the observed mechanism of both surfaces was explained.After 18 years in service,the elongation at the break of the pipe decreased by 16.2%,and the toughness of the matrix in the main collapse area of the tensile sample was the fundamental reason responsible for changes in the mechanical properties.Finally,after 18 years in service,the oxidation induction time of the pipeline was 25.7 min,which was 28.5% higher than the national standard value.There were no potential safety hazards during continuous long-term service.The results of this paper provide reference data and theoretical guidance for the aging process study of buried polyethylene pipelines.

The Research for Surface Properties of Steel Slag Powder and High-Temperature Rheological Properties of Asphalt Mortar

In order to evaluate the feasibility of steel slag powder as filler,the coating properties of steel slag and limestone aggregate were compared by water boiling test,the micro morphology difierences between steel slag powder and mineral powder(limestone powder)were compared by scanning electron microscope(SEM),and the high-temperature rheological properties of asphalt mortar with difierent ratio of filler quality to asphalt quality(F/A)and difierent substitution rates of mineral powder(S/F)were studied by dynamic shear rheological test.The results show that the surface microstructure of steel slag powder is more abundant than that of mineral powder,and the adhesion of steel slag to asphalt is better than that of limestone.At the same temperature,the lower the ratio of S/F is,the greater the rutting factor and complex modulus will be.In addition,the complex modulus and rutting factor of the asphalt mortar increase with the increase of F/A,and the filler type and F/A have a negligible efiect on the phase angle.

Effect of nano TiO_(2) and SiO_(2) on gelation performance of HPAM/PEI gels for high-temperature reservoir conformance improvement

Nanoparticles have been widely used in polymer gel systems in recent years to improve gelation performance under high-temperature reservoir conditions. However, different types of nanoparticles have different effects on their gelation performance, which has been little researched. In this study, the high-temperature gelation performance, chemical structure, and microstructure of polymer gels prepared from two nanomaterials (i.e., nano-SiO_(2) and nano-TiO_(2)) were measured. The conventional HPAM/PEI polymer gel system was employed as the control sample. Results showed that the addition of nano-TiO_(2) could significantly enhance the gel strength of HPAM/PEI gel at 80 ℃. The gel strength of the enhanced HPAM/PEI gel with 0.1 wt% nano-TiO_(2) could reach grade I. The system also had excellent high-temperature stability at 150 ℃. The enhanced HPAM/PEI gel with 0.02 wt% nano-TiO_(2) reached the maximum gel strength at 150 ℃ with a storage modulus (G′) of 15 Pa, which can meet the need for efficient plugging. However, the nano-SiO_(2) enhanced HPAM/PEI polymer gel system showed weaker gel strength than that with nano-TiO_(2) at both 80 and 150 ℃ with G′ lower than 5 Pa. Microstructures showed that the nano-TiO_(2) enhanced HPAM/PEI gel had denser three-dimensional (3D) mesh structures, which makes the nano-TiO_(2) enhanced HPAM/PEI gel more firmly bound to water. The FT-IR results also confirmed that the chemical structure of the nano-TiO_(2) enhanced HPAM/PEI gel was more thermally stable than nano-SiO_(2) since there was a large amount of –OH groups on the structure surface. Therefore, nano-TiO_(2) was more suitable as the reinforcing material for HPAM/PEI gels for high-temperature petroleum reservoir conformance improvement.