Traditional ceramic materials are generally brittle and not flexible with high production costs,which seriously hinders their practical applications.Multifunctional nanofiber ceramic aerogels are highly desirable for ...Traditional ceramic materials are generally brittle and not flexible with high production costs,which seriously hinders their practical applications.Multifunctional nanofiber ceramic aerogels are highly desirable for applications in extreme environments,however,the integration of multiple functions in their preparation is extremely challenging.To tackle these challenges,we fabricated a multifunctional SiC@SiO_(2) nanofiber aerogel(SiC@SiO_(2) NFA)with a threedimensional(3D)porous cross-linked structure through a simple chemical vapor deposition method and subsequent heat-treatment process.The as-prepared SiC@SiO_(2) NFA exhibits an ultralow density(~11 mg cm^(-3)),ultra-elastic,fatigue-resistant and refractory performance,high temperature thermal stability,thermal insulation properties,and significant strain-dependent piezoresistive sensing behavior.Furthermore,the SiC@SiO_(2) NFA shows a superior electromagnetic wave absorption performance with a minimum refection loss(RL_(min))value of-50.36 d B and a maximum effective absorption bandwidth(EAB_(max))of 8.6 GHz.The successful preparation of this multifunctional aerogel material provides a promising prospect for the design and fabrication of the cutting-edge ceramic materials.展开更多
Energy and bandwidth are the scarce resources in ad hoc networks because most of the mobile nodes are battery-supplied and share the exclusive wireless medium. Integrating the power control into MAC protocol is a prom...Energy and bandwidth are the scarce resources in ad hoc networks because most of the mobile nodes are battery-supplied and share the exclusive wireless medium. Integrating the power control into MAC protocol is a promising technique to fully exploit these precious resources of ad hoc wireless networks. In this paper, a new intelligent power-controlled Medium Access Control (MAC) (iMAC) protocol with dynamic neighbor prediction is proposed. Through the elaborate design of the distributed transmit-receive strategy of mobile nodes, iMAC greatly outperforms the prevailing IEEE 802.11 MAC protocols in not only energy conservation but also network throughput. Using the Dynamic Neighbor Prediction (DNP), iMAC performs well in mobile scenes. To the best of our knowledge, iMAC is the first protocol that considers the performance deterioration of power-controlled MAC protocols in mobile scenes and then proposes a solution. Simulation results indicate that DNP is important and necessary for power-controlled MAC protocols in mobile ad hoc networks.展开更多
Lithium–sulfur(Li–S)batteries are supposed to be one of the most potential next-generation batteries owing to their high theoretical capacity and low cost.Nevertheless,the shuttle effect of firm multi-step two-elect...Lithium–sulfur(Li–S)batteries are supposed to be one of the most potential next-generation batteries owing to their high theoretical capacity and low cost.Nevertheless,the shuttle effect of firm multi-step two-electron reaction between sulfur and lithium in liquid electrolyte makes the capacity much smaller than the theoretical value.Many methods were proposed for inhibiting the shuttle effect of polysulfide,improving corresponding redox kinetics and enhancing the integral performance of Li–S batteries.Here,we will comprehensively and systematically summarize the strategies for inhibiting the shuttle effect from all components of Li–S batteries.First,the electrochemical principles/mechanism and origin of the shuttle effect are described in detail.Moreover,the efficient strategies,including boosting the sulfur conversion rate of sulfur,confining sulfur or lithium polysulfides(LPS)within cathode host,confining LPS in the shield layer,and preventing LPS from contacting the anode,will be discussed to suppress the shuttle effect.Then,recent advances in inhibition of shuttle effect in cathode,electrolyte,separator,and anode with the aforementioned strategies have been summarized to direct the further design of efficient materials for Li–S batteries.Finally,we present prospects for inhibition of the LPS shuttle and potential development directions in Li–S batteries.展开更多
Background: Seasonal adjustments in body mass and energy budget are important for the survival of small birds in temperate zones. Seasonal changes in body mass, body temperature, gross energy intake(GEI), digestible e...Background: Seasonal adjustments in body mass and energy budget are important for the survival of small birds in temperate zones. Seasonal changes in body mass, body temperature, gross energy intake(GEI), digestible energy intake(DEI), body fat content, as well as length and mass of the digestive tract, were measured in Chinese Bulbuls(Pycnonotus sinensis) caught in the wild at Wenzhou, China.Methods: Body mass was determined with a Sartorius balance. The caloric contents of the dried food and feces were then determined using a oxygen bomb calorimeter. Total fat was extracted from the dried carcasses by ether extraction in a Soxhlet apparatus. The digestive tract of each bird was measured and weighed, and was then dried to a constant mass.Results: Body mass showed a significant seasonal variation and was higher in spring and winter than in summer and autumn. Body fat was higher in winter than in other seasons. GEI and DEI were significantly higher in winter.The length and mass of the digestive tract were greatest in winter and the magnitude of both these parameters was positively correlated with body mass, GEI and DEI. Small passerines typically have higher daily energy expenditure in winter, necessitating increased food consumption.Conclusions: This general observation is consistent with the observed winter increase in gut volume and body mass in Chinese Bulbuls. These results suggest that Chinese Bulbuls adjust to winter conditions by increasing their body mass, body fat, GEI, DEI and digestive tract size.展开更多
Two-dimensional(2D)MoS_(2)with appealing physical properties is a promising candidate for next-generation electronic and optoelectronic devices,where the ultrathin MoS_(2)is usually laid on or gated by a dielectric ox...Two-dimensional(2D)MoS_(2)with appealing physical properties is a promising candidate for next-generation electronic and optoelectronic devices,where the ultrathin MoS_(2)is usually laid on or gated by a dielectric oxide layer.The oxide/MoS_(2)interfaces widely existing in these devices have significant impacts on the carrier transport of the MoS_(2)channel by diverse interface interactions.Artificial design of the oxide/MoS_(2)interfaces would provide an effective way to break through the performance limit of the 2D devices but has yet been well explored.Here,we report a high-performance MoS_(2)-based phototransistor with an enhanced photoresponse by interfacing few-layer MoS_(2)with an ultrathin Ti0_(2)layer.The Ti0_(2)is deposited on MoS_(2)through the oxidation of an e-beam-evaporated ultrathin Ti layer.Upon a visible-light illumination,the fabricated Ti0_(2)/MoS_(2)phototransistor exhibits a responsivity of up to 2,199 A/W at a gate voltage of 60 V and a detectivity of up to 1.67×10^(13)Jones at a zero-gate voltage under a power density of 23.2μW/mm^(2).These values are 4.0 and 4.2 times those of the pure MoS_(2)phototransistor.The significantly enhanced photoresponse of Ti0_(2)/MoS_(2)device can be attributed to both interface charge transfer and photogating effects.Our results not only provide valuable insights into the interactions at Ti0_(2)/MoS_(2)interface,but also may inspire new approach to develop other novel optoelectronic devices based on 2D layered materials.展开更多
Background Chronic hepatitis C virus （HCV） infection can affect multiple organ systems and cause a variety of extrahepatic manifestations （EMs）.We sought to assess the constituent ratio of EMs in Chinese patients ...Background Chronic hepatitis C virus （HCV） infection can affect multiple organ systems and cause a variety of extrahepatic manifestations （EMs）.We sought to assess the constituent ratio of EMs in Chinese patients with chronic HCV infection and identify the clinical and biological factors associated with EM.Methods The medical records of 297 patients with chronic HCV infection were analyzed and demographic and epidemiological information was collected.The diagnosis of chronic HCV infection was based on positive anti-HCV combined with a positive HCV-RNA or at least two times of elevated aminotransferases attributable to HCV infection.Patients with HBV and/or HIV coinfection,autoimmune hepatitis,and history of alcohol abuse were excluded.Results Sixty-two percent （184/297） of the patients had at least one EM,including fatigue （29.4％）,type 2 diabetes mellitus （28.2％）,renal involvement （12.5％）,lymphadenopathy （9.6％）,fever （9.4％）,thyroid dysfunction （8.1％）,and arthralgia （7.4％）.Neuropathy,sicca syndrome,B-cell lymphoma,Raynaud＇s phenomenon,and lichen planus were rare.The mean age of patients with EM was older compared with those without EM.Conclusions EMs were common in Chinese patients with chronic HCV infection,particularly fatigue,type 2 diabetes,renal impairment,lymphadenophy,fever,and thyroid dysfunction.Older age was associated with EMs.展开更多
目的:研究辣木在全球的潜在气候适宜区划。方法:基于全球物种多样性信息数据库、实地调研、文献收集等共收集960条有效数据,综合全球气候数据库的68组生态影响因子,通过生态位最大信息熵(MaxEnt)模型研究辣木在全球和中国的潜在气候适...目的:研究辣木在全球的潜在气候适宜区划。方法:基于全球物种多样性信息数据库、实地调研、文献收集等共收集960条有效数据,综合全球气候数据库的68组生态影响因子,通过生态位最大信息熵(MaxEnt)模型研究辣木在全球和中国的潜在气候适宜区。结果:辣木在全球的气候分布概率>50%的区域有拉丁美洲、非洲中部及东部沿海区域、亚洲的东南亚地区及澳大利亚北部沿海地区;在中国范围内的气候分布概率>50%的区域为海南中南部,分布概率为30%~50%的区域主要有广东、广西、云南、福建的部分地区。结论:气候适宜性区划与《中国植物志》和《Flora of China》中描述的范围基本一致,可以为辣木在全球范围内的野生和栽培资源调查、保护和可持续发展提供参考。展开更多
Multifunctionalization is the development direction of personal thermal energy regulation equipment in the future.However,it is still a huge challenge to effectively integrate multiple functionalities into one materia...Multifunctionalization is the development direction of personal thermal energy regulation equipment in the future.However,it is still a huge challenge to effectively integrate multiple functionalities into one material.In this study,a simple thermochemical process was used to prepare a multifunctional SiC nanofiber aerogel spring(SiC NFAS),which exhibited ultralow density(9 mg/cm3),ultralow thermal conductivity(0.029 W/(m·K)at 20℃),excellent ablation and oxidation resistance,and a stable three-dimensional(3D)structure that composed of a large number of interlacing 3C-SiC nanofibers with diameters of 300–500 nm and lengths in tens to hundreds of microns.Furthermore,the as-prepared SiC NFAS displayed excellent mechanical properties,with a permanent deformation of only 1.3%at 20℃after 1000 cycles.Remarkably,the SiC NFAS exhibited robust hyperelasticity and cyclic fatigue resistance at both low(~-196℃)and high(~700℃)temperatures.Due to its exceptional thermal insulation performance,the SiC NFAS can be used for personal thermal energy regulation.The results of the study conclusively show that the SiC NFAS is a multifunctional material and has potential insulation applications in both low-and high-temperature environments.展开更多
Material composition and structural design are important factors influencing the electromagnetic wave(EMW)absorption performance of materials.To alleviate the impedance mismatch attributed to the high dielectric const...Material composition and structural design are important factors influencing the electromagnetic wave(EMW)absorption performance of materials.To alleviate the impedance mismatch attributed to the high dielectric constant of Ti_(3)C_(2)T_(x)MXene,we have successfully synthesized core‐shell structured SiO_(2)@MXene@MoS_(2)nanospheres.This architecture,comprising SiO_(2) as the core,MXene as the intermediate layer,and MoS_(2) as the outer shell,is achieved through an electrostatic self‐assembly method combined with a hydrothermal process.This complex core‐shell structure not only provides a variety of loss mechanisms that effectively dissipate electromagnetic energy but also prevents self‐aggregation of MXene and MoS_(2) nanosheets.Notably,the synergistic combination of SiO_(2) and MoS_(2) with highly conductive MXene enables the suitable dielectric constant of the composites,ensuring optimal impedance matching.Therefore,the core‐shell structured SiO_(2)@MXene@MoS_(2) nanospheres exhibit excellent EMW absorption performance,featuring a remarkable minimum reflection loss(RL_(min))of−52.11 dB(2.4 mm).It is noteworthy that these nanospheres achieve an ultra‐wide effective absorption bandwidth(EAB)of 6.72 GHz.This work provides a novel approach for designing and synthesizing high‐performance EMW absorbers characterized by“wide bandwidth and strong reflection loss.”展开更多
Switching the reaction routes in peroxymonosulfate(PMS)-based advanced oxidation processes have attracted much attention but remain challenging.Herein,a series of Co-N/C catalysts with different compositions and struc...Switching the reaction routes in peroxymonosulfate(PMS)-based advanced oxidation processes have attracted much attention but remain challenging.Herein,a series of Co-N/C catalysts with different compositions and structures were prepared by using bimetallic zeolitic imidazolate frameworks based on ZIF-8 and ZIF-67(x Zn/Co-ZIFs).Results show that Co doping amount could mediate the transformation of the activation pathway of PMS over CoN/C.When Co doping amount was less than 10%,the constructed x Co-N/C/PMS system(x≤10%)was singlet oxygen-dominated reaction;however further increasing Co doping amount would lead to the generation and coexistence of sulfate radicals and high-valent cobalt,besides singlet oxygen.Furthermore,the nitrogen-coordinated Co(Co-NX)sites could serve as main catalytically active sites to generate singlet oxygen.While excess Co doping amount caused the formation of Co nanoparticles from which leached Co ions were responsible for the generation of sulfate radicals and high-valent cobalt.Compared to undoped N/C,Co doping could significantly enhance the catalytic performance.The 0.5%Co-N/C could achieve the optimum degradation(0.488 min^(-1))and mineralization abilities(78.4%)of sulfamethoxazole among the investigated Co-N/C catalysts,which was superior to most of previously reported catalysts.In addition,the application prospects of the two systems in different environmental scenarios(pH,inorganic anions and natural organic matter)were assessed and showed different degradation behaviors.This study provides a strategy to regulate the reactive species in PMS-based advanced oxidation process.展开更多
Background:Patients who undergo coronary artery bypass grafting(CABG)are known to be at a significant risk of experiencing long-term adverse events,emphasizing the importance of regular assessments.Evaluating health-r...Background:Patients who undergo coronary artery bypass grafting(CABG)are known to be at a significant risk of experiencing long-term adverse events,emphasizing the importance of regular assessments.Evaluating health-related quality of life(HRQoL)serves as a direct method to gauge prognosis.Our objective is to ascertain the prognostic significance of consecutive HRQoL assessments using the Physical Component Summary(PCS)and Mental Component Summary(MCS)derived from the Short-Form 36(SF-36)health survey in CABG patients.Methods:The study population consisted of 433 patients who underwent isolated elective CABG at Fuwai Hospital between 2012 and 2013.SF-36 assessments were conducted during both the hospitalization period and follow-up.The primary endpoint of the study was all-cause mortality,while the secondary outcome was a composite measure including death,myocardial infarction,stroke,and repeat revascularization.We assessed the relationships between the PCS and MCS at baseline,as well as their changes during the first 6 months after the surgery(referred to asΔPCS andΔMCS,respectively),and the observed outcomes.Results:The patients were followed for an average of 6.28 years,during which 35 individuals(35/433,8.1%)died.After adjusting for clinical variables,it was observed that baseline MCS scores(hazard ratio[HR]for a 1-standard deviation[SD]decrease,1.57;95%confidence interval[CI],1.07-2.30)andΔMCS(HR for a 1-SD decrease,1.67;95%CI,1.09-2.56)were associated with all-cause mortality.However,baseline PCS scores andΔPCS did not exhibit a significant relationship with all-cause mortality.Notably,there was a dose-response relationship observed betweenΔMCS and the likelihood of all-cause mortality(HRs for the 2nd,3rd and 4th quartiles compared to the 1st quartile,0.33,0.45 and 0.11,respectively).Conclusions:Baseline MCS and changes in MCS were independent predictors for long-term mortality of CABG.Better mental health status and recovery indicated better prognosis.展开更多
In the era of new media,short videos as an innovative means of communication have led to significant changes in the promotion strategies of tourist cities.The prosperity of the tourism industry has a significant drivi...In the era of new media,short videos as an innovative means of communication have led to significant changes in the promotion strategies of tourist cities.The prosperity of the tourism industry has a significant driving effect on local economic growth,and marketing strategies are the key to the progress of the tourism industry.Through efficient marketing methods,the visibility of tourist attractions and cities can be significantly improved,thereby attracting more tourists and injecting new vitality into the local tourism industry and the overall economy.At present,with the rapid development of short video platforms such as TikTok and the sharp increase in the number of users,short video marketing has gradually received widespread attention from industry professionals and the general public.Some cities have achieved good results in tourism marketing implemented with the help of short video platforms,prompting more cities to use short videos for marketing activities.However,short videos also negatively impact urban tourism marketing,reducing the appeal of TikTok marketing to audiences.Therefore,this article conducts in-depth research on the impact of short video media on urban tourism marketing,elaborates on the advantages,analyzes the impact,proposes strategies for the application,and hopes to provide a reference for cities to use short videos for tourism marketing.展开更多
Background:ALDH6A1,a member of the ALDH family,plays a crucial role in the catabolic pathways of valine and thymine.Dysregulation of ALDH6A1 expression has been linked to a variety of diseases.Methylmalonate semialdeh...Background:ALDH6A1,a member of the ALDH family,plays a crucial role in the catabolic pathways of valine and thymine.Dysregulation of ALDH6A1 expression has been linked to a variety of diseases.Methylmalonate semialdehyde dehydrogenase deficiency(MMSDH deficiency),an autosomal recessive disorder,arises from muta-tions in the ALDH6A1 gene.Additionally,ALDH6A1 has emerged as a biomarker for several types of severe cancer.Despite its significance,the structural and biochemical mechanisms of ALDH6A1 remain poorly explored.Methods:The apo form of ALDH6A1 was solved by cryo-electron microscopy.Enzyme activity assay and thermal stability assays were conducted to elucidate the bio-chemical properties of ALDH6A1 and to find an agonist of ALDH6A1,Alda-1.The binding pattern of ALDH6A1 and nicotinamide adenine dinucleotide(NAD^(+))was explored by molecular docking.Results:This study presents,for the first time,a structural analysis of ALDH6A1 in its apo form at a resolution of 2.75Å,uncovering a tetrameric architecture with tightly interacting monomers.Our findings indicate that Alda-1,an agonist of ALDH2,enhances ALDH6A1 activity as well.Moreover,ALDH6A1,compared with ALDH2,exhibits a unique binding model with NAD^(+).Conclusion:Our results shed light on the structural aspects of ALDH6A1 and provide valuable insights into its catalytic mechanism.The precise determination of the ALDH6A1 structure holds promise for the development of targeted therapies aimed at restoring ALDH6A1 activity,thus providing potential value for individuals affected by related diseases.展开更多
The high-strength and creep-resistant Mg-Al-Ca-Mn alloys have broad application prospects.However,solidification cracking occurs in these alloys in certain conditions and the origin is still unclear.This work investig...The high-strength and creep-resistant Mg-Al-Ca-Mn alloys have broad application prospects.However,solidification cracking occurs in these alloys in certain conditions and the origin is still unclear.This work investigated the relationship between the solidification path,microstructure evolution and solidification cracking behavior of the Mg-xAl-2Ca-Mn alloys during tungsten inert gas(TIG)welding.Results show that when the fusion zone’s Ca/Al mass ratio ranges from 0.4 to 1.64,solidification cracking occurs at a Ca/Al mass ratio of∼0.7.As the Ca/Al mass ratio approaches this value,the grain size increases,and the Laves phases are reduced gradually.The early formed Laves phases play an important role in promoting dendrite segmentation,refining grain size and enhancing grain boundaries.When a solidification path delays the formation of Laves phases,the Laves phases will be reduced accompanied by grain coarsening.In such a solidifying microstructure,intergranular cavitation is easy to occur,and the resistance of the semi-solid alloy to crack propagation is severely reduced.展开更多
It is proved that, any finite dimensional complex Lie algebra/~ = [Z：, ~：], hence, over a field of characteristic zero, any finite dimensional Lie algebra l： = [/2, ~：] possessing a basis with complex structure co...It is proved that, any finite dimensional complex Lie algebra/~ = [Z：, ~：], hence, over a field of characteristic zero, any finite dimensional Lie algebra l： = [/2, ~：] possessing a basis with complex structure constants, should be a weak co-split Lie algebra. A class of non-semi-simple co-split Lie algebras is given.展开更多
Flexible electronics can be seamlessly attached to human skin and used for various purposes, such as pulse monitoring, pressure measurement, tensile sensing, and motion detection. Despite their broad applications, mos...Flexible electronics can be seamlessly attached to human skin and used for various purposes, such as pulse monitoring, pressure measurement, tensile sensing, and motion detection. Despite their broad applications, most flexible electronics do not possess both high sensitivity and wide detection range simultaneously;their sensitivity drops rapidly when they are subjected to even just medium pressure. In this study, ultrabroad-range, high-sensitivity flexible electronics are fabricated through additive manufacturing to address this issue. The key to possess high sensitivity and a wide detection range simultaneously is to fabricate flexible electronics with large depth-width ratio circuit channels using the additive manufacturing inner-rinsing template method. These electronics exhibit an unprecedented high sensitivity of 320 kPa^(−1) over the whole detection range, which ranges from 0.3 to 30,000 Pa (five orders of magnitude). Their minimum detectable weight is 0.02 g (the weight of a fly), which is comparable with human skin. They can stretch to over 500% strain without breaking and show no tensile fatigue after 1000 repetitions of stretching to 100% strain. A highly sensitive and flexible electronic epidermal pulse monitor is fabricated to detect multiple physiological signals, such as pulse signal, breathing rhythm, and real-time beat-to-beat cuffless blood pressure. All of these signals can be obtained simultaneously for detailed health detection and monitoring. The fabrication method does not involve complex expensive equipment or complicated operational processes, so it is especially suitable for the fabrication of large-area, complex flexible electronics. We believe this approach will pave the way for the application of flexible electronics in biomedical detection and health monitoring.展开更多
Objective：Research has demonstrated that microRNA（miR）-106a is related to cisplatin resistance.We investigated the expression of miR-106a in the serum of patients with non-small cell lung cancer（NSCLC）and their s...Objective：Research has demonstrated that microRNA（miR）-106a is related to cisplatin resistance.We investigated the expression of miR-106a in the serum of patients with non-small cell lung cancer（NSCLC）and their sensitivity to chemotherapy by cisplatin combined with gemcitabine.Methods：Eighty-five NSCLC patients,who completed four cycles of gemcitabine and cisplatin chemotherapy,volunteered for this study and their serum samples were collected.Serum samples from 60 healthy subjects were used as controls.Real-time quantitative polymerase chain reaction（real-time q PCR）was used to quantify the level of miR-106a in the serum.Demographic and survival data of these patients were collected for the analysis.Results：The expression of miR-106a in the serum of NSCLC patients was significantly higher than that of healthy subjects（P＆lt;0.001）.The expression of miR-106a was not correlated with patients＇gender,age,tumor size,lymphatic metastasis,and pathological types;but was correlated with patients＇tumor staging（P=0.003）.After chemotherapy,serum miR-106a expression decreased in patients.The decrease in miR-106a expression in the chemotherapy-sensitive group was much higher than that in the chemotherapy-resistant group.Survival analysis shows that NSCLC patients with high expression of miR-106a have a poorer prognosis.The overall survival of NSCLC patients in the chemotherapy-sensitive group was significantly higher than that in the chemotherapy-resistant group.Conclusions：High expression of miR-106a may be involved in the development of NSCLC.Mi R-106a has significance in the prognosis of NSCLC.The level of miR-106a in the serum can be a useful parameter in screening for drug resistance during cisplatin-based chemotherapy.展开更多
To enable the capacity of climbing robots to work on steep surfaces,especially on inverted surfaces,is a fundamental but challenging task.This capacity can extend the reachable workspace and applications of climbing r...To enable the capacity of climbing robots to work on steep surfaces,especially on inverted surfaces,is a fundamental but challenging task.This capacity can extend the reachable workspace and applications of climbing robots.A track-type inverted climbing robot called SpinyCrawler was developed in this paper.Using a spiny track with an opposed gripping mechanism,the robot was experimentally demonstrated to have the ability of generating considerable adhesion to achieve stable inverted climbing.First,to guarantee reliable attachment of the robot on rough ceilings,a spiny gripper inspired by the opposed gripping prolegs of caterpillars is designed,and a gripping model of the interaction between spines and the ceiling asperities is established and analyzed.Second,a spiny track is developed by assembling dozens of spiny grippers to enable continuous attachment.A cam mechanism is introduced in the robot design without extra actuators to achieve stable attachment and easy detachment during continuous climbing.Finally,climbing experiments are conducted on different surfaces,using a SpinyCrawler prototype.Experimental results demonstrated stable climbing ability on various rough inverted and vertical surfaces,including concrete walls,crushed stone walls,sandpaper walls,brick walls,and brick ceilings.展开更多
The effects of Al content and Ca/Al mass ratio on the microstructure and mechanical properties of tungsten inert gas(TIG)welded Mg-2Ca-x Al-0.5Mn(x=0,1,5)alloy joints were studied in present work.Results showed that i...The effects of Al content and Ca/Al mass ratio on the microstructure and mechanical properties of tungsten inert gas(TIG)welded Mg-2Ca-x Al-0.5Mn(x=0,1,5)alloy joints were studied in present work.Results showed that increasing Al content was effective in reducing the dendrite spacing at the fusion zone(FZ)edge.The Laves phases in the FZ and the heat-affected zone(HAZ)can be changed from Mg_(2)Ca to(Mg,Al)_(2)Ca with the decrease of Ca/Al ratio,and the(Mg,Al)_(2)Ca could be further transformed to Al_(2)Ca under welding thermal cycle.Furthermore,dynamic dissolution and precipitation of Laves phases and Al_(8)Mn_(5)phases occurred in the HAZ,resulting in a gradient microstructure and hardness peak in this area.The tensile properties of the joints were significantly improved with the increase of Al content,which was mainly due to the modification of Laves phases.展开更多
基金financially supported by the National Natural Science Foundation of China(No.U2004177 and U21A2064)Outstanding Youth Fund of Henan Province(No.212300410081)+1 种基金Scientific and Technological Innovation Talents in Colleges and Universities in Henan Province(22HASTIT001)The Research and Entrepreneurship Start-up Projects for Overseas Returned Talents。
文摘Traditional ceramic materials are generally brittle and not flexible with high production costs,which seriously hinders their practical applications.Multifunctional nanofiber ceramic aerogels are highly desirable for applications in extreme environments,however,the integration of multiple functions in their preparation is extremely challenging.To tackle these challenges,we fabricated a multifunctional SiC@SiO_(2) nanofiber aerogel(SiC@SiO_(2) NFA)with a threedimensional(3D)porous cross-linked structure through a simple chemical vapor deposition method and subsequent heat-treatment process.The as-prepared SiC@SiO_(2) NFA exhibits an ultralow density(~11 mg cm^(-3)),ultra-elastic,fatigue-resistant and refractory performance,high temperature thermal stability,thermal insulation properties,and significant strain-dependent piezoresistive sensing behavior.Furthermore,the SiC@SiO_(2) NFA shows a superior electromagnetic wave absorption performance with a minimum refection loss(RL_(min))value of-50.36 d B and a maximum effective absorption bandwidth(EAB_(max))of 8.6 GHz.The successful preparation of this multifunctional aerogel material provides a promising prospect for the design and fabrication of the cutting-edge ceramic materials.
文摘Energy and bandwidth are the scarce resources in ad hoc networks because most of the mobile nodes are battery-supplied and share the exclusive wireless medium. Integrating the power control into MAC protocol is a promising technique to fully exploit these precious resources of ad hoc wireless networks. In this paper, a new intelligent power-controlled Medium Access Control (MAC) (iMAC) protocol with dynamic neighbor prediction is proposed. Through the elaborate design of the distributed transmit-receive strategy of mobile nodes, iMAC greatly outperforms the prevailing IEEE 802.11 MAC protocols in not only energy conservation but also network throughput. Using the Dynamic Neighbor Prediction (DNP), iMAC performs well in mobile scenes. To the best of our knowledge, iMAC is the first protocol that considers the performance deterioration of power-controlled MAC protocols in mobile scenes and then proposes a solution. Simulation results indicate that DNP is important and necessary for power-controlled MAC protocols in mobile ad hoc networks.
基金support from the “Joint International Laboratory on Environmental and Energy Frontier Materials”“Innovation Research Team of High-Level Local Universities in Shanghai”support from the National Natural Science Foundation of China (22209103)
文摘Lithium–sulfur(Li–S)batteries are supposed to be one of the most potential next-generation batteries owing to their high theoretical capacity and low cost.Nevertheless,the shuttle effect of firm multi-step two-electron reaction between sulfur and lithium in liquid electrolyte makes the capacity much smaller than the theoretical value.Many methods were proposed for inhibiting the shuttle effect of polysulfide,improving corresponding redox kinetics and enhancing the integral performance of Li–S batteries.Here,we will comprehensively and systematically summarize the strategies for inhibiting the shuttle effect from all components of Li–S batteries.First,the electrochemical principles/mechanism and origin of the shuttle effect are described in detail.Moreover,the efficient strategies,including boosting the sulfur conversion rate of sulfur,confining sulfur or lithium polysulfides(LPS)within cathode host,confining LPS in the shield layer,and preventing LPS from contacting the anode,will be discussed to suppress the shuttle effect.Then,recent advances in inhibition of shuttle effect in cathode,electrolyte,separator,and anode with the aforementioned strategies have been summarized to direct the further design of efficient materials for Li–S batteries.Finally,we present prospects for inhibition of the LPS shuttle and potential development directions in Li–S batteries.
基金financially supported by grants from the National Natural Science Foundation of China (No.31070366 and No.31470472)the Natural Science Foundation (LY13C030005) in Zhejian Provincethe Zhejiang Province ‘Xinmiao’ Project
文摘Background: Seasonal adjustments in body mass and energy budget are important for the survival of small birds in temperate zones. Seasonal changes in body mass, body temperature, gross energy intake(GEI), digestible energy intake(DEI), body fat content, as well as length and mass of the digestive tract, were measured in Chinese Bulbuls(Pycnonotus sinensis) caught in the wild at Wenzhou, China.Methods: Body mass was determined with a Sartorius balance. The caloric contents of the dried food and feces were then determined using a oxygen bomb calorimeter. Total fat was extracted from the dried carcasses by ether extraction in a Soxhlet apparatus. The digestive tract of each bird was measured and weighed, and was then dried to a constant mass.Results: Body mass showed a significant seasonal variation and was higher in spring and winter than in summer and autumn. Body fat was higher in winter than in other seasons. GEI and DEI were significantly higher in winter.The length and mass of the digestive tract were greatest in winter and the magnitude of both these parameters was positively correlated with body mass, GEI and DEI. Small passerines typically have higher daily energy expenditure in winter, necessitating increased food consumption.Conclusions: This general observation is consistent with the observed winter increase in gut volume and body mass in Chinese Bulbuls. These results suggest that Chinese Bulbuls adjust to winter conditions by increasing their body mass, body fat, GEI, DEI and digestive tract size.
基金the National Key Research and Development Program of China(No.2018YFA0703700)the National Natural Science Foundation of China(Nos.11974041,51971025)+1 种基金111 Project(No.B170003)the Fundamental Research Funds for the Central Universities(No.FRF-BD-19-016A).
文摘Two-dimensional(2D)MoS_(2)with appealing physical properties is a promising candidate for next-generation electronic and optoelectronic devices,where the ultrathin MoS_(2)is usually laid on or gated by a dielectric oxide layer.The oxide/MoS_(2)interfaces widely existing in these devices have significant impacts on the carrier transport of the MoS_(2)channel by diverse interface interactions.Artificial design of the oxide/MoS_(2)interfaces would provide an effective way to break through the performance limit of the 2D devices but has yet been well explored.Here,we report a high-performance MoS_(2)-based phototransistor with an enhanced photoresponse by interfacing few-layer MoS_(2)with an ultrathin Ti0_(2)layer.The Ti0_(2)is deposited on MoS_(2)through the oxidation of an e-beam-evaporated ultrathin Ti layer.Upon a visible-light illumination,the fabricated Ti0_(2)/MoS_(2)phototransistor exhibits a responsivity of up to 2,199 A/W at a gate voltage of 60 V and a detectivity of up to 1.67×10^(13)Jones at a zero-gate voltage under a power density of 23.2μW/mm^(2).These values are 4.0 and 4.2 times those of the pure MoS_(2)phototransistor.The significantly enhanced photoresponse of Ti0_(2)/MoS_(2)device can be attributed to both interface charge transfer and photogating effects.Our results not only provide valuable insights into the interactions at Ti0_(2)/MoS_(2)interface,but also may inspire new approach to develop other novel optoelectronic devices based on 2D layered materials.
文摘Background Chronic hepatitis C virus （HCV） infection can affect multiple organ systems and cause a variety of extrahepatic manifestations （EMs）.We sought to assess the constituent ratio of EMs in Chinese patients with chronic HCV infection and identify the clinical and biological factors associated with EM.Methods The medical records of 297 patients with chronic HCV infection were analyzed and demographic and epidemiological information was collected.The diagnosis of chronic HCV infection was based on positive anti-HCV combined with a positive HCV-RNA or at least two times of elevated aminotransferases attributable to HCV infection.Patients with HBV and/or HIV coinfection,autoimmune hepatitis,and history of alcohol abuse were excluded.Results Sixty-two percent （184/297） of the patients had at least one EM,including fatigue （29.4％）,type 2 diabetes mellitus （28.2％）,renal involvement （12.5％）,lymphadenopathy （9.6％）,fever （9.4％）,thyroid dysfunction （8.1％）,and arthralgia （7.4％）.Neuropathy,sicca syndrome,B-cell lymphoma,Raynaud＇s phenomenon,and lichen planus were rare.The mean age of patients with EM was older compared with those without EM.Conclusions EMs were common in Chinese patients with chronic HCV infection,particularly fatigue,type 2 diabetes,renal impairment,lymphadenophy,fever,and thyroid dysfunction.Older age was associated with EMs.
文摘目的:研究辣木在全球的潜在气候适宜区划。方法:基于全球物种多样性信息数据库、实地调研、文献收集等共收集960条有效数据,综合全球气候数据库的68组生态影响因子,通过生态位最大信息熵(MaxEnt)模型研究辣木在全球和中国的潜在气候适宜区。结果:辣木在全球的气候分布概率>50%的区域有拉丁美洲、非洲中部及东部沿海区域、亚洲的东南亚地区及澳大利亚北部沿海地区;在中国范围内的气候分布概率>50%的区域为海南中南部,分布概率为30%~50%的区域主要有广东、广西、云南、福建的部分地区。结论:气候适宜性区划与《中国植物志》和《Flora of China》中描述的范围基本一致,可以为辣木在全球范围内的野生和栽培资源调查、保护和可持续发展提供参考。
基金This work was financially supported by the National Natural Science Foundation of China(Nos.U2004177 and U21A2064)Outstanding Youth Fund of the National Science Fundation of Henan Province(No.212300410081).
文摘Multifunctionalization is the development direction of personal thermal energy regulation equipment in the future.However,it is still a huge challenge to effectively integrate multiple functionalities into one material.In this study,a simple thermochemical process was used to prepare a multifunctional SiC nanofiber aerogel spring(SiC NFAS),which exhibited ultralow density(9 mg/cm3),ultralow thermal conductivity(0.029 W/(m·K)at 20℃),excellent ablation and oxidation resistance,and a stable three-dimensional(3D)structure that composed of a large number of interlacing 3C-SiC nanofibers with diameters of 300–500 nm and lengths in tens to hundreds of microns.Furthermore,the as-prepared SiC NFAS displayed excellent mechanical properties,with a permanent deformation of only 1.3%at 20℃after 1000 cycles.Remarkably,the SiC NFAS exhibited robust hyperelasticity and cyclic fatigue resistance at both low(~-196℃)and high(~700℃)temperatures.Due to its exceptional thermal insulation performance,the SiC NFAS can be used for personal thermal energy regulation.The results of the study conclusively show that the SiC NFAS is a multifunctional material and has potential insulation applications in both low-and high-temperature environments.
基金Joint Fund of Research and Development Program of Henan Province,Grant/Award Number:222301420002National Natural Science Foundation of China,Grant/Award Number:U21A2064Scientific and Technological Innovation Talents in Colleges and Universities in Henan Province,Grant/Award Number:22HASTIT001。
文摘Material composition and structural design are important factors influencing the electromagnetic wave(EMW)absorption performance of materials.To alleviate the impedance mismatch attributed to the high dielectric constant of Ti_(3)C_(2)T_(x)MXene,we have successfully synthesized core‐shell structured SiO_(2)@MXene@MoS_(2)nanospheres.This architecture,comprising SiO_(2) as the core,MXene as the intermediate layer,and MoS_(2) as the outer shell,is achieved through an electrostatic self‐assembly method combined with a hydrothermal process.This complex core‐shell structure not only provides a variety of loss mechanisms that effectively dissipate electromagnetic energy but also prevents self‐aggregation of MXene and MoS_(2) nanosheets.Notably,the synergistic combination of SiO_(2) and MoS_(2) with highly conductive MXene enables the suitable dielectric constant of the composites,ensuring optimal impedance matching.Therefore,the core‐shell structured SiO_(2)@MXene@MoS_(2) nanospheres exhibit excellent EMW absorption performance,featuring a remarkable minimum reflection loss(RL_(min))of−52.11 dB(2.4 mm).It is noteworthy that these nanospheres achieve an ultra‐wide effective absorption bandwidth(EAB)of 6.72 GHz.This work provides a novel approach for designing and synthesizing high‐performance EMW absorbers characterized by“wide bandwidth and strong reflection loss.”
基金supported by the National Natural Science Foundation of China(Nos.52100081,51978178,and 51521006)the Department of Science and Technology of Guangdong Province of China(Nos.2021A1515011797,2023A1515012062,2019A1515012044,and 2022A1515010226)+4 种基金the Department of Education of Guangdong Province of China(No.2021KTSCX078)the Program for Innovative Research Teams of Guangdong Higher Education Institutes of China(No.2021KCXTD043)Maoming Municipal Department of Science and Technology of Guangdong Province of China(No.2018S0013)the Key Laboratory of Petrochemical Pollution Control of Guangdong Higher Education Institutes(No.2017KSYS004)the Startup Fund of GDUPT(Nos.2018rc63 and 2020rc041)。
文摘Switching the reaction routes in peroxymonosulfate(PMS)-based advanced oxidation processes have attracted much attention but remain challenging.Herein,a series of Co-N/C catalysts with different compositions and structures were prepared by using bimetallic zeolitic imidazolate frameworks based on ZIF-8 and ZIF-67(x Zn/Co-ZIFs).Results show that Co doping amount could mediate the transformation of the activation pathway of PMS over CoN/C.When Co doping amount was less than 10%,the constructed x Co-N/C/PMS system(x≤10%)was singlet oxygen-dominated reaction;however further increasing Co doping amount would lead to the generation and coexistence of sulfate radicals and high-valent cobalt,besides singlet oxygen.Furthermore,the nitrogen-coordinated Co(Co-NX)sites could serve as main catalytically active sites to generate singlet oxygen.While excess Co doping amount caused the formation of Co nanoparticles from which leached Co ions were responsible for the generation of sulfate radicals and high-valent cobalt.Compared to undoped N/C,Co doping could significantly enhance the catalytic performance.The 0.5%Co-N/C could achieve the optimum degradation(0.488 min^(-1))and mineralization abilities(78.4%)of sulfamethoxazole among the investigated Co-N/C catalysts,which was superior to most of previously reported catalysts.In addition,the application prospects of the two systems in different environmental scenarios(pH,inorganic anions and natural organic matter)were assessed and showed different degradation behaviors.This study provides a strategy to regulate the reactive species in PMS-based advanced oxidation process.
基金supported by a grant from the National Natural Science Foundation of China(No.81830072)
文摘Background:Patients who undergo coronary artery bypass grafting(CABG)are known to be at a significant risk of experiencing long-term adverse events,emphasizing the importance of regular assessments.Evaluating health-related quality of life(HRQoL)serves as a direct method to gauge prognosis.Our objective is to ascertain the prognostic significance of consecutive HRQoL assessments using the Physical Component Summary(PCS)and Mental Component Summary(MCS)derived from the Short-Form 36(SF-36)health survey in CABG patients.Methods:The study population consisted of 433 patients who underwent isolated elective CABG at Fuwai Hospital between 2012 and 2013.SF-36 assessments were conducted during both the hospitalization period and follow-up.The primary endpoint of the study was all-cause mortality,while the secondary outcome was a composite measure including death,myocardial infarction,stroke,and repeat revascularization.We assessed the relationships between the PCS and MCS at baseline,as well as their changes during the first 6 months after the surgery(referred to asΔPCS andΔMCS,respectively),and the observed outcomes.Results:The patients were followed for an average of 6.28 years,during which 35 individuals(35/433,8.1%)died.After adjusting for clinical variables,it was observed that baseline MCS scores(hazard ratio[HR]for a 1-standard deviation[SD]decrease,1.57;95%confidence interval[CI],1.07-2.30)andΔMCS(HR for a 1-SD decrease,1.67;95%CI,1.09-2.56)were associated with all-cause mortality.However,baseline PCS scores andΔPCS did not exhibit a significant relationship with all-cause mortality.Notably,there was a dose-response relationship observed betweenΔMCS and the likelihood of all-cause mortality(HRs for the 2nd,3rd and 4th quartiles compared to the 1st quartile,0.33,0.45 and 0.11,respectively).Conclusions:Baseline MCS and changes in MCS were independent predictors for long-term mortality of CABG.Better mental health status and recovery indicated better prognosis.
文摘In the era of new media,short videos as an innovative means of communication have led to significant changes in the promotion strategies of tourist cities.The prosperity of the tourism industry has a significant driving effect on local economic growth,and marketing strategies are the key to the progress of the tourism industry.Through efficient marketing methods,the visibility of tourist attractions and cities can be significantly improved,thereby attracting more tourists and injecting new vitality into the local tourism industry and the overall economy.At present,with the rapid development of short video platforms such as TikTok and the sharp increase in the number of users,short video marketing has gradually received widespread attention from industry professionals and the general public.Some cities have achieved good results in tourism marketing implemented with the help of short video platforms,prompting more cities to use short videos for marketing activities.However,short videos also negatively impact urban tourism marketing,reducing the appeal of TikTok marketing to audiences.Therefore,this article conducts in-depth research on the impact of short video media on urban tourism marketing,elaborates on the advantages,analyzes the impact,proposes strategies for the application,and hopes to provide a reference for cities to use short videos for tourism marketing.
基金supported by the National Key Research and Development Program of China(2022YFC2703100 and 2023YFC3605504)the Chinese Academy of Medical Sciences Innovation Fund for Medical Sciences(2021-I2M-1003)the National High Level Hospital Clinical Research Funding(2022-PUMCH-D-002 and 2022 PUMCH-B-098).
文摘Background:ALDH6A1,a member of the ALDH family,plays a crucial role in the catabolic pathways of valine and thymine.Dysregulation of ALDH6A1 expression has been linked to a variety of diseases.Methylmalonate semialdehyde dehydrogenase deficiency(MMSDH deficiency),an autosomal recessive disorder,arises from muta-tions in the ALDH6A1 gene.Additionally,ALDH6A1 has emerged as a biomarker for several types of severe cancer.Despite its significance,the structural and biochemical mechanisms of ALDH6A1 remain poorly explored.Methods:The apo form of ALDH6A1 was solved by cryo-electron microscopy.Enzyme activity assay and thermal stability assays were conducted to elucidate the bio-chemical properties of ALDH6A1 and to find an agonist of ALDH6A1,Alda-1.The binding pattern of ALDH6A1 and nicotinamide adenine dinucleotide(NAD^(+))was explored by molecular docking.Results:This study presents,for the first time,a structural analysis of ALDH6A1 in its apo form at a resolution of 2.75Å,uncovering a tetrameric architecture with tightly interacting monomers.Our findings indicate that Alda-1,an agonist of ALDH2,enhances ALDH6A1 activity as well.Moreover,ALDH6A1,compared with ALDH2,exhibits a unique binding model with NAD^(+).Conclusion:Our results shed light on the structural aspects of ALDH6A1 and provide valuable insights into its catalytic mechanism.The precise determination of the ALDH6A1 structure holds promise for the development of targeted therapies aimed at restoring ALDH6A1 activity,thus providing potential value for individuals affected by related diseases.
基金supported by the National Natural Science Foun-dation of China(Nos.U2102212,52301134,52271092,52371095)Natural Science Foundation of Chongqing(Nos.CSTB2022NSCQ-MSX1438,CSTB2022NSCQ-MSX0891)+1 种基金Scientific and Technological Research Program of Chongqing Municipal Education Commission(No.KJQN202001527)Innovative research team of universities in Chongqing(No.CXQT21030).
文摘The high-strength and creep-resistant Mg-Al-Ca-Mn alloys have broad application prospects.However,solidification cracking occurs in these alloys in certain conditions and the origin is still unclear.This work investigated the relationship between the solidification path,microstructure evolution and solidification cracking behavior of the Mg-xAl-2Ca-Mn alloys during tungsten inert gas(TIG)welding.Results show that when the fusion zone’s Ca/Al mass ratio ranges from 0.4 to 1.64,solidification cracking occurs at a Ca/Al mass ratio of∼0.7.As the Ca/Al mass ratio approaches this value,the grain size increases,and the Laves phases are reduced gradually.The early formed Laves phases play an important role in promoting dendrite segmentation,refining grain size and enhancing grain boundaries.When a solidification path delays the formation of Laves phases,the Laves phases will be reduced accompanied by grain coarsening.In such a solidifying microstructure,intergranular cavitation is easy to occur,and the resistance of the semi-solid alloy to crack propagation is severely reduced.
基金Project supported by the National Natural Science Foundation of China (No. 11001110)
文摘It is proved that, any finite dimensional complex Lie algebra/~ = [Z：, ~：], hence, over a field of characteristic zero, any finite dimensional Lie algebra l： = [/2, ~：] possessing a basis with complex structure constants, should be a weak co-split Lie algebra. A class of non-semi-simple co-split Lie algebras is given.
基金This research was funded by the Shenzhen Science and Technology Planning Project(Grant Numbers JCYJ20180507183224565 and ZDSYS20190902093220279)the Shenzhen Peacock Group(Grant Numbers KQTD20170809110344233 and KQTD20200820113045083).
文摘Flexible electronics can be seamlessly attached to human skin and used for various purposes, such as pulse monitoring, pressure measurement, tensile sensing, and motion detection. Despite their broad applications, most flexible electronics do not possess both high sensitivity and wide detection range simultaneously;their sensitivity drops rapidly when they are subjected to even just medium pressure. In this study, ultrabroad-range, high-sensitivity flexible electronics are fabricated through additive manufacturing to address this issue. The key to possess high sensitivity and a wide detection range simultaneously is to fabricate flexible electronics with large depth-width ratio circuit channels using the additive manufacturing inner-rinsing template method. These electronics exhibit an unprecedented high sensitivity of 320 kPa^(−1) over the whole detection range, which ranges from 0.3 to 30,000 Pa (five orders of magnitude). Their minimum detectable weight is 0.02 g (the weight of a fly), which is comparable with human skin. They can stretch to over 500% strain without breaking and show no tensile fatigue after 1000 repetitions of stretching to 100% strain. A highly sensitive and flexible electronic epidermal pulse monitor is fabricated to detect multiple physiological signals, such as pulse signal, breathing rhythm, and real-time beat-to-beat cuffless blood pressure. All of these signals can be obtained simultaneously for detailed health detection and monitoring. The fabrication method does not involve complex expensive equipment or complicated operational processes, so it is especially suitable for the fabrication of large-area, complex flexible electronics. We believe this approach will pave the way for the application of flexible electronics in biomedical detection and health monitoring.
文摘Objective：Research has demonstrated that microRNA（miR）-106a is related to cisplatin resistance.We investigated the expression of miR-106a in the serum of patients with non-small cell lung cancer（NSCLC）and their sensitivity to chemotherapy by cisplatin combined with gemcitabine.Methods：Eighty-five NSCLC patients,who completed four cycles of gemcitabine and cisplatin chemotherapy,volunteered for this study and their serum samples were collected.Serum samples from 60 healthy subjects were used as controls.Real-time quantitative polymerase chain reaction（real-time q PCR）was used to quantify the level of miR-106a in the serum.Demographic and survival data of these patients were collected for the analysis.Results：The expression of miR-106a in the serum of NSCLC patients was significantly higher than that of healthy subjects（P＆lt;0.001）.The expression of miR-106a was not correlated with patients＇gender,age,tumor size,lymphatic metastasis,and pathological types;but was correlated with patients＇tumor staging（P=0.003）.After chemotherapy,serum miR-106a expression decreased in patients.The decrease in miR-106a expression in the chemotherapy-sensitive group was much higher than that in the chemotherapy-resistant group.Survival analysis shows that NSCLC patients with high expression of miR-106a have a poorer prognosis.The overall survival of NSCLC patients in the chemotherapy-sensitive group was significantly higher than that in the chemotherapy-resistant group.Conclusions：High expression of miR-106a may be involved in the development of NSCLC.Mi R-106a has significance in the prognosis of NSCLC.The level of miR-106a in the serum can be a useful parameter in screening for drug resistance during cisplatin-based chemotherapy.
基金supported by the National Natural Science Foundation of China(Grant No.51805431)the China Postdoctoral Science Foundation(Grant No.2018M643695)the Suzhou Science and Technology Foundation(Grant No.SYG201813).
文摘To enable the capacity of climbing robots to work on steep surfaces,especially on inverted surfaces,is a fundamental but challenging task.This capacity can extend the reachable workspace and applications of climbing robots.A track-type inverted climbing robot called SpinyCrawler was developed in this paper.Using a spiny track with an opposed gripping mechanism,the robot was experimentally demonstrated to have the ability of generating considerable adhesion to achieve stable inverted climbing.First,to guarantee reliable attachment of the robot on rough ceilings,a spiny gripper inspired by the opposed gripping prolegs of caterpillars is designed,and a gripping model of the interaction between spines and the ceiling asperities is established and analyzed.Second,a spiny track is developed by assembling dozens of spiny grippers to enable continuous attachment.A cam mechanism is introduced in the robot design without extra actuators to achieve stable attachment and easy detachment during continuous climbing.Finally,climbing experiments are conducted on different surfaces,using a SpinyCrawler prototype.Experimental results demonstrated stable climbing ability on various rough inverted and vertical surfaces,including concrete walls,crushed stone walls,sandpaper walls,brick walls,and brick ceilings.
基金financially supported by the National Natural Science Foundation of China(No.52175288)the Scientific and Technological Research Program of Chongqing Municipal Education Commission(Nos.KJQN202001527 and KJZD-K202001502)+2 种基金the Innovation Research Group of Nniversities in Chongqing(No.CXQT21030),t Chongqing Talent Project(No.CQYC201905100)the State Key Lab of Advanced Welding and Joining,Harbin Institute of Technology(No.AWJ-22M21)the Natural Science Foundation of Chongqing(No.cstc2020jcyj-msxm X0552)。
文摘The effects of Al content and Ca/Al mass ratio on the microstructure and mechanical properties of tungsten inert gas(TIG)welded Mg-2Ca-x Al-0.5Mn(x=0,1,5)alloy joints were studied in present work.Results showed that increasing Al content was effective in reducing the dendrite spacing at the fusion zone(FZ)edge.The Laves phases in the FZ and the heat-affected zone(HAZ)can be changed from Mg_(2)Ca to(Mg,Al)_(2)Ca with the decrease of Ca/Al ratio,and the(Mg,Al)_(2)Ca could be further transformed to Al_(2)Ca under welding thermal cycle.Furthermore,dynamic dissolution and precipitation of Laves phases and Al_(8)Mn_(5)phases occurred in the HAZ,resulting in a gradient microstructure and hardness peak in this area.The tensile properties of the joints were significantly improved with the increase of Al content,which was mainly due to the modification of Laves phases.
