Owls exhibit remarkably silent flight,largely attributed to trailing-edge(TE)serrations on their wings.Inspired by this biological adaptation,TE serrations have become promising passive-noise-control strategies for ae...Owls exhibit remarkably silent flight,largely attributed to trailing-edge(TE)serrations on their wings.Inspired by this biological adaptation,TE serrations have become promising passive-noise-control strategies for aerodynamic devices,including drones and wind turbines.However,conventional designs typically feature single-scale geometries—Such as sawtooth or sinusoidal serrations—that fail to replicate the owl’s inherently dual-scale morphology:Macro-scale waviness formed by feather tips combined with micro-scale morphology.Here,we introduce and evaluate a hybrid TE serration design that incorporates both macro-scale wave patterns and micro-scale fringe-like elements to closely emulate the owl wing structure.Using large-eddy simulations coupled with the Ffowcs Williams-Hawkings acoustic analogy,we assess three configurations:A smooth baseline,a conventional wavy serration,and the proposed hybrid serration.Our results indicate that the hybrid configuration achieves an overall noise reduction of about 12 dB relative to the smooth baseline,surpassing the conventional wavy configuration by approximately 2.5 dB,while preserving aerodynamic performance as measured by lift-to-drag ratio.Flow-field analyses further reveal that dual-scale serrations effectively suppress TE pressure fluctuations,highlighting a key aeroacoustic advantage of the owl-inspired hybrid approach.These insights advance our understanding of bioinspired noisecontrol mechanisms and provide practical guidelines for designing quieter aerodynamic systems.展开更多
Biomimetics has recently emerged as an interesting approach to enhance renewable energy technologies.In this work,bioinspired Trailing Edge Serrations(TES)were evaluated on a typical Vertical Axis Wind Turbine(VAWT)ai...Biomimetics has recently emerged as an interesting approach to enhance renewable energy technologies.In this work,bioinspired Trailing Edge Serrations(TES)were evaluated on a typical Vertical Axis Wind Turbine(VAWT)airfoil,the DU06-W200.As noise reduction benefits of these mechanisms are already well-established,this study focuses on their impact on airfoil and VAWT performance.A saw-tooth geometry was chosen based on VAWT specifications and existing research,followed by a detailed assessment through wind tunnel tests using a newly developed aerodynamic balance.For a broad spectrum of attack angles and Reynolds numbers,lift,drag,and pitching moments were carefully measured.The results show that TES enhance the lift-to-drag ratio,especially in stalled conditions,and postpone stall at negative angles,expanding the effective performance range.A notable increase in pitching moment also is also observed,relevant for blade-strut joint design.Additionally,the impact on turbine performance was estimated using an analytical model,demonstrating excellent accuracy when compared against previous experimental results.TES offer a modest 2%improve-ment in peak performance,though they slightly narrow the optimal tip-speed ratio zone.Despite this,the potential noise reduction and performance gains make TES a valuable addition to VAWT designs,especially in urban settings.展开更多
Trailing edge serrations(TESs)are capable of noticeably suppressing the turbulent trailing edge noise induced by rotating wind turbine blades and become an integral part of a blade.However,the challenges involved in t...Trailing edge serrations(TESs)are capable of noticeably suppressing the turbulent trailing edge noise induced by rotating wind turbine blades and become an integral part of a blade.However,the challenges involved in the dimensional design of serration height 2 h,wavelengthλand flap angleϕare yet to be dealt with in a satisfactory manner.To address the problem,a general model for simulating the effects of serrations on the hydrodynamic and aeroacoustic performance is proposed due to its ease of use and relatively low requirements for user input.The solid serrations are replicated by momentum sources calculated by its aerodynamic forces.Then,a case relevant to wind turbine airfoil is examined,a hybrid improved delay detached eddy simulation(IDDES)method coupled with FW-H integration is deployed to obtain the flow features and far-field sound pressure level.It is found that the modeling method could reproduce the flow field and noise as serrated airfoil.展开更多
Metallic amorphous/crystalline(A/C)nanolaminates exhibit excellent ductility while retaining their high strength.However,the underlying physical mechanisms and the resultant structural changes during plastic deformati...Metallic amorphous/crystalline(A/C)nanolaminates exhibit excellent ductility while retaining their high strength.However,the underlying physical mechanisms and the resultant structural changes during plastic deformation still remain unclear.In the present work,the structure-property relationship of CuZr/Cu A/C nanolaminates is established through integrated high-throughput micro-compression tests and molecular dynamics simulations together with high-resolution transmission electron microcopy.The serrated flow of nanolaminates results from the formation of hexagonal-close-packed(HCP)-type stacking faults and twins inside the face-centered-cubic(FCC)Cu nano-grains,the body-centered-cubic(BCC)-type ordering at their grain boundaries,and the crystallization of the amorphous CuZr layers.The serration behavior of CuZr/Cu A/C nanolaminates is determined by several factors,including the formation of dense dislocation networks from the multiplication of initial dislocations that formed after yielding,weak-spots-related configurational-transitions and shear-transition-zone activities,and deformation-induced devitrification.The present work provides an insight into the heterogeneous deformation mechanism of A/C nanolaminates at the atomic scale,and mechanistic base for the microstructural design of self-toughening metallic-glass(MG)-based composites and A/C nanolaminates.展开更多
By means of statistical analysis,the deformation mechanisms taking place in elastic loading and plastic shearing stages during serrated flows on the stress-strain curves for bulk metallic glasses were studied comprehe...By means of statistical analysis,the deformation mechanisms taking place in elastic loading and plastic shearing stages during serrated flows on the stress-strain curves for bulk metallic glasses were studied comprehensively.Normalized serration number presented a linear increasing tendency with the decrease of applied strain rates due to the reduction of free volumes.An excellent plastic deformation was illustrated from the influences of structure arrangement with activation energy.By using mean-field theory（MFT）,maximum elastic-energy density at different strain rates could be predicted by MFT besides maximum stress drops during serrations.These results were helpful for understanding the serrated flow behavior or designing decent schemes to improve the plasticity of bulk metallic glasses at room temperature.展开更多
Due to the gradually prominent impact of fracture characteristics and serrated yielding in the application of nickel-based superalloys,the hot tensile properties of Inconel 718 superalloy were studied,including fractu...Due to the gradually prominent impact of fracture characteristics and serrated yielding in the application of nickel-based superalloys,the hot tensile properties of Inconel 718 superalloy were studied,including fracture behavior,mechanical properties,and plastic behavior.The experiments adopted three heat treatment regimes and two tensile directions.Results show that various heat treatments make grain sizes different.The larger-sized grains make the vertical surface uneven,which also decrease the number of grain boundaries and carbides,restricting the occurrence of dimples and ultimately reducing the material plasticity.The reduced grain boundaries can decrease dislocations,increase the demand for thermal activation energy,and transform the serration mode of serrated yielding.In addition,various heat treatments also make precipitates different.Carbides can promote the formation of dimples.The needle-shaped δ phase precipitates at grain boundaries and twin boundaries,and slightly inclines towards the rolling direction.Therefore,its pinning effect is outstanding along the transverse direction,which can affect the dimple aggregation and the dislocation movement,ultimately exhibiting anisotropy in fracture characteristics,mechanical properties,and serrated yielding.展开更多
BACKGROUND Serrated polyposis syndrome(SPS)is a polyposis condition with neoplastic potential,but its psychological impact is not well understood.AIM To assess health anxiety prevalence in a regional Australian cohort...BACKGROUND Serrated polyposis syndrome(SPS)is a polyposis condition with neoplastic potential,but its psychological impact is not well understood.AIM To assess health anxiety prevalence in a regional Australian cohort of SPS patients and explore factors influencing it,including workforce impacts of regular surveillance.METHODS This cross-sectional study screened patients aged 18-65 undergoing colonoscopy in a regional gastroenterology practice between January 2015 and June 2022.Eligible SPS patients were invited to participate.Data included the Short Health Anxiety Inventory,employment status,and previous demographic and medical findings.RESULTS Health anxiety was found in 21.57%of SPS patients,with anxious patients being significantly more concerned about surveillance(OR=7.70).Patients lost an average of 11.04 work hours per colonoscopy.CONCLUSION Health anxiety in SPS patients aligns with rates in other gastroenterology populations.Identifying it may improve management,though further research is needed to better understand prevalence and care improvements.展开更多
This editorial discusses Thompson et al's original article,which is published in the most recent edition of the World Journal of Clinical Oncology and sheds critical light on the intertwined issues of health anxie...This editorial discusses Thompson et al's original article,which is published in the most recent edition of the World Journal of Clinical Oncology and sheds critical light on the intertwined issues of health anxiety and work loss in individuals diagnosed with serrated polyposis syndrome(SPS).SPS is rare,characterized by the development of multiple serrated colorectal polyps.This editorial provides an overview of SPS,including its pathophysiology,clinical presentation,diagnostic criteria,management strategies,and the psychosocial impact.SPS is linked to molecular alterations,which drive carcinogenesis.Colonoscopy and histological analysis are used for diagnosis.Genetic testing is also considered where there is a family history.Quality of life can be greatly impacted by the psychosocial effects of SPS,especially health anxiety.Further understanding of the molecular mechanisms and creating individualized surveillance are required.展开更多
BACKGROUND Traditional serrated adenoma(TSA)is a rare and precancerous lesion of colorectal cancer.The clinical and endoscopic differentiations between TSAs without dysplasia or adenocarcinoma(TSAOs)and TSAs with dysp...BACKGROUND Traditional serrated adenoma(TSA)is a rare and precancerous lesion of colorectal cancer.The clinical and endoscopic differentiations between TSAs without dysplasia or adenocarcinoma(TSAOs)and TSAs with dysplasia or adenocarcinoma(TSADs)remain unclear.AIM To evaluate the characteristics of colorectal TSAs and compare the characteristics of TSAOs with those of TSADs.METHODS This retrospective study included 193 patients who underwent endoscopic resection and received a pathologic diagnosis of TSA.We reviewed the medical,endoscopic,and histopathologic records of patients who underwent endoscopic resection of TSAs between January 2010 and December 2023.RESULTS TSAs were more frequently located in the rectosigmoid colon.Most TSAs had 0-Ip,0-Isp,or 0-Is morphologies.The TSAD lesions were larger than TSAO lesions.TSAD lesions more commonly had a red color and an irregular border than TSAO lesions.TSAOs were usually treated using conventional endoscopic mucosal resection,whereas TSADs were treated using conventional endoscopic mucosal resection,endoscopic submucosal dissection,and surgery.Post-polypectomy bleeding was more common with TSADs than with TSAOs.Univariate analysis showed that gastrointestinal bleeding,red color,0-IIa,irregular border,and lobular mucosal surface were significantly associated with TSADs.Multivariate analysis showed that gastrointestinal bleeding,an irregular border,and a lobular mucosal surface were significantly associated with TSADs.CONCLUSION TSAs with gastrointestinal bleeding,an irregular border,and a lobular mucosal surface are associated with an increased risk of dysplasia or adenocarcinoma.展开更多
BACKGROUND According to the guidelines in the United States,individuals with a family history of colorectal cancer should be screened at the age of 40 years.Data on the prevalence of adenomas and sessile serrated lesi...BACKGROUND According to the guidelines in the United States,individuals with a family history of colorectal cancer should be screened at the age of 40 years.Data on the prevalence of adenomas and sessile serrated lesions(SSLs)in individuals aged 40-49 years in Japan are lacking.AIM To investigate the effect of family history on the detection of adenomas and SSLs during colonoscopy in Japan.METHODS This retrospective,single-center cohort study included individuals aged 40-79 years who underwent colonoscopy by expert endoscopists with an adenoma detection rate(ADR)≥40%between 2021 and 2024.The ADR and adenoma plus SSL detection rate(ASDR)were investigated according to age.Multivariable analyses were performed to examine the effects of first-degree family history of colorectal cancer,fecal immunochemical test,and sex on the ADR and ASDR for each age group.A binomial logistic regression model was used.RESULTS In 10248 participants,the overall ADR and ASDR were 53.6%and 59.1%,respectively.The ADR and ASDR increased with age.Among 2317 participants aged 40-49 years,the presence of a family history significantly increased the ADR(47.6%vs 38.2%).The odds ratio of a family history for the ADR adjusted by sex and fecal immunochemical test was 1.59(95%confidence interval:1.13-2.25).In contrast,there was no significant association between the ADR and family history in participants aged 50-59,60-69,and 70-79 years.Similarly,a family history significantly increased the ASDR(58.0%vs 43.7%)in participants aged 40-49 years.The odds ratio of a family history for the ASDR was 1.92(95%confidence interval:1.36-2.71).CONCLUSION Participants with a family history exhibited significantly elevated ADR(47.6%)and ASDR(58.0%),in their 40s.Individuals with a family history should initiate colonoscopy at 40 years old.展开更多
The effects of rejuvenation heat treatment(RHT)on the serrated flow behavior and fracture mode of nickel-based superalloys(R26)were investigated by tensile tests and microstructural characterization.The serrated flow ...The effects of rejuvenation heat treatment(RHT)on the serrated flow behavior and fracture mode of nickel-based superalloys(R26)were investigated by tensile tests and microstructural characterization.The serrated flow activation energies were determined to be 41−72 and 64−81 kJ/mol before and after RHT,respectively.Dynamic strain aging in the alloy is caused by the diffusion of carbon atoms into dislocation channels in the nickel matrix.Before RHT,carbides are concentrated at the grain boundaries.Cracks initiate from these carbides and propagate along the grain boundaries.RHT dissolves carbides at grain boundaries,transferring crack initiation to the precipitated phase group in the grains.RHT increases carbon atom concentration in the nickel matrix,enhancing dynamic strain aging and serrated flow behavior.展开更多
The serrated flow behavior,known as the Portevin-Le Chatelier(PLC)effect,is commonly observed during high-temperature deformation.In this study,we report a serrated flow behavior in FeCoCrNiMo0.2 high-entropy alloy(HE...The serrated flow behavior,known as the Portevin-Le Chatelier(PLC)effect,is commonly observed during high-temperature deformation.In this study,we report a serrated flow behavior in FeCoCrNiMo0.2 high-entropy alloy(HEA),which is mediated by nano-twinning and phase transformation at cryogenic temperatures.During uniaxial tensile deformation at 77 K,the alloy exhibited the formation of high-density deformation nano-twinning,cross-twinning,stacking faults(SFs)and Lomer-Cottrell locks(L-C locks).Additionally,the lower stacking fault energy(SFE)at low temperatures promotes the formation of the 9R phase.The high-density twin boundaries effectively hinder dislocation movement,leading to the instability of plastic deformation and promoting the serrated flow behavior.Furthermore,the rapid and unstable transformation of the 9R phase contributes to the pronounced serrated flow behavior.Nano-twinning,SFs,cross-twinning,L-C locks and 9R phase collectively induce a dynamic Hall-Petch effect,enhancing the strength-ductility synergy and strain-hardening ability of deformed alloy at 77 K.Our work provides valuable insights into the mechanism of tensile deformation at cryogenic temperatures in single-phase FCC HEA.展开更多
Some studies have reported that approximately 50%of appendiceal lesions are sessile serrated lesions(SSLs).Traditionally,surgical intervention has been the preferred method.Endoscopic procedures such as endoscopic muc...Some studies have reported that approximately 50%of appendiceal lesions are sessile serrated lesions(SSLs).Traditionally,surgical intervention has been the preferred method.Endoscopic procedures such as endoscopic mucosal resection(EMR)serve as alternative treatments for lesions at the appendiceal orifice(AO).However,EMR is not appropriate when the lesion margin within the AO cannot be visualized.When lesions extend into the lumen,extended laparoscopic appendectomy(ELA)or combined surgery can be used to resect the lesions.Compared with traditional surgery and EMR,ELA or combined surgery is a safer and more precise option that preserves the function of the ileocecal region.However,the need for coordination between surgeons and endoscopists,along with the requirement for staged procedures and multiple bowel preparations,increases the complexity of the treatment.In recent years,with the advancement of endoscopic full-thickness resection,endoscopic transcecal appendectomy(ETA)has been used to treat SSLs involving the AO.The use of choledochoscopy in conjunction with ETA can further enhance treatment precision.This integrated approach holds promise for replacing the combined endoscopic and laparoscopic surgical techniques.However,additional data are required to confirm its safety and efficacy.展开更多
BACKGROUND Sessile serrated lesions(SSLs)are premalignant polyps implicated in up to 30%of colorectal cancers.Australia reports high SSL detection rates(SSL-DRs),yet with marked variability(3.1%-24%).This substantial ...BACKGROUND Sessile serrated lesions(SSLs)are premalignant polyps implicated in up to 30%of colorectal cancers.Australia reports high SSL detection rates(SSL-DRs),yet with marked variability(3.1%-24%).This substantial variation raises concerns about missed lesions and post-colonoscopy colorectal cancer.This study investigates determinants associated with SSL-DR variation in regional Australia.AIM To study how patient,clinical,and colonoscopy factors are associated with SSL detection in a regional Australian practice.We aimed to contribute high-detection data to the literature by analyzing the association of SSL detection with various determinants.METHODS This retrospective,cross-sectional analysis examined 1450 colonoscopies performed at Port Macquarie Gastroenterology during 2023.Sigmoidoscopies and repeat procedures were excluded.Multivariate logistic regression analyzed associations between SSL detection and patient demographics,clinical indications,procedural factors,and comorbidities.RESULTS The overall SSL-DR was 30.7%.Multivariate analysis identified several independent predictors:Clinical indication,bowel preparation quality,inflammatory bowel disease status,and serrated polyposis syndrome.The faecal occult blood test positive(FOBT)(+)cohort showed the highest predicted SSL detection probability(39.8%),while clinical symptoms showed the lowest(22.3%).After adjustment,SSL detection odds were 2.3 times greater among FOBT(+)patients than those with clinical symptoms(adjusted odds ratio=2.30,95%confidence interval:1.20-4.40,P=0.004).CONCLUSION SSL-DR as a quality indicator requires contextualization regarding clinical indications,bowel preparation quality,and comorbidities.There was a significantly higher prevalence of SSLs in FOBT(+)patients.Despite comprehensive adjustment,this study cannot fully explain the wide SSL-DR variation in Australia,highlighting the need for standardized detection protocols and further research to ensure optimal cancer prevention outcomes.展开更多
Fe-Cr-Ni austenitic alloys are extensively utilized in the hot-end components of nuclear light water reactors,turbine disks,and gas compressors.However,their low strength at elevated temperatures limits their engineer...Fe-Cr-Ni austenitic alloys are extensively utilized in the hot-end components of nuclear light water reactors,turbine disks,and gas compressors.However,their low strength at elevated temperatures limits their engineering applications.In this study,a novel precipit-ation-strengthened alloy system is developed by incorporating Al and Si elements into a FeCrNi equiatomic alloy.The results indicate that the FeCrNiAl_(x)Si_(x)(at%,x=0.1,0.2)alloys possess heterogeneous precipitation structures that feature a micron-scaleσphase at the grain boundaries and a nanoscale ordered body-centered cube(B2)phase within the grains.An exceptional strength-ductility synergy across a wide temperature range is achieved in FeCrNiAl_(0.1)Si_(0.1)alloys due to grain refinement and precipitation strengthening.Notably,a yield strength of 693.83 MPa,an ultimate tensile strength of 817.55 MPa,and a uniform elongation of 18.27%are attained at 873 K.The dislo-cation shearing mechanism for B2 phases and the Orowan bypass mechanism forσphase,coupled with a high density of nano-twins and stacking faults in the matrix,contribute to the excellent mechanical properties at cryogenic and ambient temperatures.Moreover,the emergence of serratedσphase and micro-twins in the matrix plays a crucial role in the strengthening and toughening mechanisms at inter-mediate temperatures.This study offers a novel perspective and strategy for the development of precipitation-hardened Fe-Cr-Ni austen-itic alloys with exceptional strength-ductility synergy over a broad temperature range.展开更多
Plastic instability,including both the discontinuous yielding and stress serrations,has been frequently observed during the tensile deformation of medium-Mn steels(MMnS)and has been intensively studied in recent years...Plastic instability,including both the discontinuous yielding and stress serrations,has been frequently observed during the tensile deformation of medium-Mn steels(MMnS)and has been intensively studied in recent years.Unfortunately,research results are controversial,and no consensus has been achieved regarding the topic.Here,we first summarize all the possible factors that affect the yielding and flow stress serrations in MMnS,including the morphology and stability of austenite,the feature of the phase interface,and the deformation parameters.Then,we propose a universal mechanism to explain the conflicting experimental results.We conclude that the discontinuous yielding can be attributed to the lack of mobile dislocation before deformation and the rapid dislocation multiplication at the beginning of plastic deformation.Meanwhile,the results show that the stress serrations are formed due to the pinning and depinning between dislocations and interstitial atoms in austenite.Strain-induced martensitic transformation,influenced by the mechanical stability of austenite grain and deformation parameters,should not be the intrinsic cause of plastic instability.However,it can intensify or weaken the discontinuous yielding and the stress serrations by affecting the mobility and density of dislocations,as well as the interaction between the interstitial atoms and dislocations in austenite grains.展开更多
The structure and the migration mechanisms of{1012}twin boundaries(TBs)of pure zinc deformed by rolling were studied using high-resolution transmission electron microscopy(HRTEM)at atomic scale.We found the presence o...The structure and the migration mechanisms of{1012}twin boundaries(TBs)of pure zinc deformed by rolling were studied using high-resolution transmission electron microscopy(HRTEM)at atomic scale.We found the presence of basal/prismatic(BP/PB)planes serrations on{1012}TBs and the coexistence of two kinds of TBs with different structures in the same{1012}twin:TBs composed of{1012}coherent twin boundaries(CTBs)plus short BP/PB serrations,and TBs composed of successive BP/PB segments without{1012}CTBs.The formation of BP/PB serrations has no relation to the c/a ratio of hexagonal-closepacked(HCP)metals because the BP/PB serrations are energetically preferred and geometrically favored.Based on dislocation theory,we proposed the migration mechanisms of the TBs to be the glide of twinning dislocations(TDs)on the CTBs and the climb of interface dislocations(IDs)on the BP/PB segments.展开更多
This work intends to manipulate the internal flow units in Zr_(55)Cu_(30)Ni_(5)Al_(10)bulk-metallic glasses(BMGs)through plasma-assisted hydrogenation to generate a positive microalloying effect on plasticity.Based on...This work intends to manipulate the internal flow units in Zr_(55)Cu_(30)Ni_(5)Al_(10)bulk-metallic glasses(BMGs)through plasma-assisted hydrogenation to generate a positive microalloying effect on plasticity.Based on the cooperative shear model theory,serration-flow statistics during nanoindentation loading and creep tests during the holding stage were used to analyze the influence of hydrogen on the behavior of flow units in BMGs.Experimental observations showed that the hydrogen in the Zr_(55)Cu_(30)Ni_(5)Al_(10)BMGs caused mechanical softening,plasticity improvement,and structural relaxation.Analysis also showed that the average volume,size,and activation energy of internal flow units in the BMGs all increased as a result of the increase in the hydrogen content.The hydrogenation in the BMGs was found to lead to a prolifera-tion of shear bands,which promoted plasticity.The aggregation of these internal flow units reduced the stress required for plastic deformation through shear bands,ultimately causing softening and structural relaxation.展开更多
基金supported by a Grant-in-Aid for Scientific Research of KAKENHI,Japan Society for the Promotion of Science(Grant Nos.23H01373 and 23K26068)support from the Japanese Government MEXT scholarship and the Excellent International Student Scholarship provided by Chiba University。
文摘Owls exhibit remarkably silent flight,largely attributed to trailing-edge(TE)serrations on their wings.Inspired by this biological adaptation,TE serrations have become promising passive-noise-control strategies for aerodynamic devices,including drones and wind turbines.However,conventional designs typically feature single-scale geometries—Such as sawtooth or sinusoidal serrations—that fail to replicate the owl’s inherently dual-scale morphology:Macro-scale waviness formed by feather tips combined with micro-scale morphology.Here,we introduce and evaluate a hybrid TE serration design that incorporates both macro-scale wave patterns and micro-scale fringe-like elements to closely emulate the owl wing structure.Using large-eddy simulations coupled with the Ffowcs Williams-Hawkings acoustic analogy,we assess three configurations:A smooth baseline,a conventional wavy serration,and the proposed hybrid serration.Our results indicate that the hybrid configuration achieves an overall noise reduction of about 12 dB relative to the smooth baseline,surpassing the conventional wavy configuration by approximately 2.5 dB,while preserving aerodynamic performance as measured by lift-to-drag ratio.Flow-field analyses further reveal that dual-scale serrations effectively suppress TE pressure fluctuations,highlighting a key aeroacoustic advantage of the owl-inspired hybrid approach.These insights advance our understanding of bioinspired noisecontrol mechanisms and provide practical guidelines for designing quieter aerodynamic systems.
基金The authors wish to thank the financial support of the Spanish Ministry of Science,Innovation and Universities in reference to the Project:Efficiency improvement and noise reduction of a vertical axis wind turbine for urban environments(MERTURB)-Ref.MCINN-22-TED2021-131307B-100.
文摘Biomimetics has recently emerged as an interesting approach to enhance renewable energy technologies.In this work,bioinspired Trailing Edge Serrations(TES)were evaluated on a typical Vertical Axis Wind Turbine(VAWT)airfoil,the DU06-W200.As noise reduction benefits of these mechanisms are already well-established,this study focuses on their impact on airfoil and VAWT performance.A saw-tooth geometry was chosen based on VAWT specifications and existing research,followed by a detailed assessment through wind tunnel tests using a newly developed aerodynamic balance.For a broad spectrum of attack angles and Reynolds numbers,lift,drag,and pitching moments were carefully measured.The results show that TES enhance the lift-to-drag ratio,especially in stalled conditions,and postpone stall at negative angles,expanding the effective performance range.A notable increase in pitching moment also is also observed,relevant for blade-strut joint design.Additionally,the impact on turbine performance was estimated using an analytical model,demonstrating excellent accuracy when compared against previous experimental results.TES offer a modest 2%improve-ment in peak performance,though they slightly narrow the optimal tip-speed ratio zone.Despite this,the potential noise reduction and performance gains make TES a valuable addition to VAWT designs,especially in urban settings.
基金This work was supported by the National Natural Science Foundation of China(Grant No.51736008)“Transformational Technologies for Clean Energy and Demonstration”,Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA21050303).
文摘Trailing edge serrations(TESs)are capable of noticeably suppressing the turbulent trailing edge noise induced by rotating wind turbine blades and become an integral part of a blade.However,the challenges involved in the dimensional design of serration height 2 h,wavelengthλand flap angleϕare yet to be dealt with in a satisfactory manner.To address the problem,a general model for simulating the effects of serrations on the hydrodynamic and aeroacoustic performance is proposed due to its ease of use and relatively low requirements for user input.The solid serrations are replicated by momentum sources calculated by its aerodynamic forces.Then,a case relevant to wind turbine airfoil is examined,a hybrid improved delay detached eddy simulation(IDDES)method coupled with FW-H integration is deployed to obtain the flow features and far-field sound pressure level.It is found that the modeling method could reproduce the flow field and noise as serrated airfoil.
基金financially supported by the National Natural Science Foundation of China(Nos.51690163 and 51601147)the Science Challenge Project(No.TZZT2019-D1.5)+4 种基金the Ministry of Science and Technology of China(No.2017YFA0700700)the United States National Science Foundation(Nos.DMR-1006557,1611180,and 1809640)the Fundamental Research Funds for the Central Universities in China(No.G2016KY0302)the CyberStar cluster funded by NSF through grant No.OCI-0821527the XSEDE clusters supported by NSF through Grant No.ACI-1053575。
文摘Metallic amorphous/crystalline(A/C)nanolaminates exhibit excellent ductility while retaining their high strength.However,the underlying physical mechanisms and the resultant structural changes during plastic deformation still remain unclear.In the present work,the structure-property relationship of CuZr/Cu A/C nanolaminates is established through integrated high-throughput micro-compression tests and molecular dynamics simulations together with high-resolution transmission electron microcopy.The serrated flow of nanolaminates results from the formation of hexagonal-close-packed(HCP)-type stacking faults and twins inside the face-centered-cubic(FCC)Cu nano-grains,the body-centered-cubic(BCC)-type ordering at their grain boundaries,and the crystallization of the amorphous CuZr layers.The serration behavior of CuZr/Cu A/C nanolaminates is determined by several factors,including the formation of dense dislocation networks from the multiplication of initial dislocations that formed after yielding,weak-spots-related configurational-transitions and shear-transition-zone activities,and deformation-induced devitrification.The present work provides an insight into the heterogeneous deformation mechanism of A/C nanolaminates at the atomic scale,and mechanistic base for the microstructural design of self-toughening metallic-glass(MG)-based composites and A/C nanolaminates.
基金the financial support of National Natural Science Foundation of China(No.51371122)the Youth Natural Science Foundation of Shanxi Province,China(No.2015021005)
文摘By means of statistical analysis,the deformation mechanisms taking place in elastic loading and plastic shearing stages during serrated flows on the stress-strain curves for bulk metallic glasses were studied comprehensively.Normalized serration number presented a linear increasing tendency with the decrease of applied strain rates due to the reduction of free volumes.An excellent plastic deformation was illustrated from the influences of structure arrangement with activation energy.By using mean-field theory（MFT）,maximum elastic-energy density at different strain rates could be predicted by MFT besides maximum stress drops during serrations.These results were helpful for understanding the serrated flow behavior or designing decent schemes to improve the plasticity of bulk metallic glasses at room temperature.
基金National Natural Science Foundation of China(52175353)Shanxi Province Key Research and Development Program(202102150401002)Shanxi Province Major Science and Technology Special Project(202101110401009)。
文摘Due to the gradually prominent impact of fracture characteristics and serrated yielding in the application of nickel-based superalloys,the hot tensile properties of Inconel 718 superalloy were studied,including fracture behavior,mechanical properties,and plastic behavior.The experiments adopted three heat treatment regimes and two tensile directions.Results show that various heat treatments make grain sizes different.The larger-sized grains make the vertical surface uneven,which also decrease the number of grain boundaries and carbides,restricting the occurrence of dimples and ultimately reducing the material plasticity.The reduced grain boundaries can decrease dislocations,increase the demand for thermal activation energy,and transform the serration mode of serrated yielding.In addition,various heat treatments also make precipitates different.Carbides can promote the formation of dimples.The needle-shaped δ phase precipitates at grain boundaries and twin boundaries,and slightly inclines towards the rolling direction.Therefore,its pinning effect is outstanding along the transverse direction,which can affect the dimple aggregation and the dislocation movement,ultimately exhibiting anisotropy in fracture characteristics,mechanical properties,and serrated yielding.
文摘BACKGROUND Serrated polyposis syndrome(SPS)is a polyposis condition with neoplastic potential,but its psychological impact is not well understood.AIM To assess health anxiety prevalence in a regional Australian cohort of SPS patients and explore factors influencing it,including workforce impacts of regular surveillance.METHODS This cross-sectional study screened patients aged 18-65 undergoing colonoscopy in a regional gastroenterology practice between January 2015 and June 2022.Eligible SPS patients were invited to participate.Data included the Short Health Anxiety Inventory,employment status,and previous demographic and medical findings.RESULTS Health anxiety was found in 21.57%of SPS patients,with anxious patients being significantly more concerned about surveillance(OR=7.70).Patients lost an average of 11.04 work hours per colonoscopy.CONCLUSION Health anxiety in SPS patients aligns with rates in other gastroenterology populations.Identifying it may improve management,though further research is needed to better understand prevalence and care improvements.
文摘This editorial discusses Thompson et al's original article,which is published in the most recent edition of the World Journal of Clinical Oncology and sheds critical light on the intertwined issues of health anxiety and work loss in individuals diagnosed with serrated polyposis syndrome(SPS).SPS is rare,characterized by the development of multiple serrated colorectal polyps.This editorial provides an overview of SPS,including its pathophysiology,clinical presentation,diagnostic criteria,management strategies,and the psychosocial impact.SPS is linked to molecular alterations,which drive carcinogenesis.Colonoscopy and histological analysis are used for diagnosis.Genetic testing is also considered where there is a family history.Quality of life can be greatly impacted by the psychosocial effects of SPS,especially health anxiety.Further understanding of the molecular mechanisms and creating individualized surveillance are required.
基金Supported by The First Research in Lifetime Grant from Chonnam National University Hospital Biomedical Research Institute,No.HCRI23005。
文摘BACKGROUND Traditional serrated adenoma(TSA)is a rare and precancerous lesion of colorectal cancer.The clinical and endoscopic differentiations between TSAs without dysplasia or adenocarcinoma(TSAOs)and TSAs with dysplasia or adenocarcinoma(TSADs)remain unclear.AIM To evaluate the characteristics of colorectal TSAs and compare the characteristics of TSAOs with those of TSADs.METHODS This retrospective study included 193 patients who underwent endoscopic resection and received a pathologic diagnosis of TSA.We reviewed the medical,endoscopic,and histopathologic records of patients who underwent endoscopic resection of TSAs between January 2010 and December 2023.RESULTS TSAs were more frequently located in the rectosigmoid colon.Most TSAs had 0-Ip,0-Isp,or 0-Is morphologies.The TSAD lesions were larger than TSAO lesions.TSAD lesions more commonly had a red color and an irregular border than TSAO lesions.TSAOs were usually treated using conventional endoscopic mucosal resection,whereas TSADs were treated using conventional endoscopic mucosal resection,endoscopic submucosal dissection,and surgery.Post-polypectomy bleeding was more common with TSADs than with TSAOs.Univariate analysis showed that gastrointestinal bleeding,red color,0-IIa,irregular border,and lobular mucosal surface were significantly associated with TSADs.Multivariate analysis showed that gastrointestinal bleeding,an irregular border,and a lobular mucosal surface were significantly associated with TSADs.CONCLUSION TSAs with gastrointestinal bleeding,an irregular border,and a lobular mucosal surface are associated with an increased risk of dysplasia or adenocarcinoma.
文摘BACKGROUND According to the guidelines in the United States,individuals with a family history of colorectal cancer should be screened at the age of 40 years.Data on the prevalence of adenomas and sessile serrated lesions(SSLs)in individuals aged 40-49 years in Japan are lacking.AIM To investigate the effect of family history on the detection of adenomas and SSLs during colonoscopy in Japan.METHODS This retrospective,single-center cohort study included individuals aged 40-79 years who underwent colonoscopy by expert endoscopists with an adenoma detection rate(ADR)≥40%between 2021 and 2024.The ADR and adenoma plus SSL detection rate(ASDR)were investigated according to age.Multivariable analyses were performed to examine the effects of first-degree family history of colorectal cancer,fecal immunochemical test,and sex on the ADR and ASDR for each age group.A binomial logistic regression model was used.RESULTS In 10248 participants,the overall ADR and ASDR were 53.6%and 59.1%,respectively.The ADR and ASDR increased with age.Among 2317 participants aged 40-49 years,the presence of a family history significantly increased the ADR(47.6%vs 38.2%).The odds ratio of a family history for the ADR adjusted by sex and fecal immunochemical test was 1.59(95%confidence interval:1.13-2.25).In contrast,there was no significant association between the ADR and family history in participants aged 50-59,60-69,and 70-79 years.Similarly,a family history significantly increased the ASDR(58.0%vs 43.7%)in participants aged 40-49 years.The odds ratio of a family history for the ASDR was 1.92(95%confidence interval:1.36-2.71).CONCLUSION Participants with a family history exhibited significantly elevated ADR(47.6%)and ASDR(58.0%),in their 40s.Individuals with a family history should initiate colonoscopy at 40 years old.
基金supported by the National Natural Science Foundation of China(No.52175286)the Tribology Science Fund of State Key Laboratory of Tribology in Advanced Equipment,Tsinghua University,China(No.SKLTKF20B16).
文摘The effects of rejuvenation heat treatment(RHT)on the serrated flow behavior and fracture mode of nickel-based superalloys(R26)were investigated by tensile tests and microstructural characterization.The serrated flow activation energies were determined to be 41−72 and 64−81 kJ/mol before and after RHT,respectively.Dynamic strain aging in the alloy is caused by the diffusion of carbon atoms into dislocation channels in the nickel matrix.Before RHT,carbides are concentrated at the grain boundaries.Cracks initiate from these carbides and propagate along the grain boundaries.RHT dissolves carbides at grain boundaries,transferring crack initiation to the precipitated phase group in the grains.RHT increases carbon atom concentration in the nickel matrix,enhancing dynamic strain aging and serrated flow behavior.
基金supported by the National Natural Science Foundation of China(Nos.52474403,52364050 and 52301137)Guizhou Provincial Program on Commercialization of Scientific and Technological Achievements(No.[2023]001)+2 种基金Guizhou Province Science and Technology Project(No.[2022]050)Guiyang city Science and Technology Project(No.[2023]48-16)the Central Government in Guidance of Local Science and Technology Development Funds(No.[2024]032).
文摘The serrated flow behavior,known as the Portevin-Le Chatelier(PLC)effect,is commonly observed during high-temperature deformation.In this study,we report a serrated flow behavior in FeCoCrNiMo0.2 high-entropy alloy(HEA),which is mediated by nano-twinning and phase transformation at cryogenic temperatures.During uniaxial tensile deformation at 77 K,the alloy exhibited the formation of high-density deformation nano-twinning,cross-twinning,stacking faults(SFs)and Lomer-Cottrell locks(L-C locks).Additionally,the lower stacking fault energy(SFE)at low temperatures promotes the formation of the 9R phase.The high-density twin boundaries effectively hinder dislocation movement,leading to the instability of plastic deformation and promoting the serrated flow behavior.Furthermore,the rapid and unstable transformation of the 9R phase contributes to the pronounced serrated flow behavior.Nano-twinning,SFs,cross-twinning,L-C locks and 9R phase collectively induce a dynamic Hall-Petch effect,enhancing the strength-ductility synergy and strain-hardening ability of deformed alloy at 77 K.Our work provides valuable insights into the mechanism of tensile deformation at cryogenic temperatures in single-phase FCC HEA.
文摘Some studies have reported that approximately 50%of appendiceal lesions are sessile serrated lesions(SSLs).Traditionally,surgical intervention has been the preferred method.Endoscopic procedures such as endoscopic mucosal resection(EMR)serve as alternative treatments for lesions at the appendiceal orifice(AO).However,EMR is not appropriate when the lesion margin within the AO cannot be visualized.When lesions extend into the lumen,extended laparoscopic appendectomy(ELA)or combined surgery can be used to resect the lesions.Compared with traditional surgery and EMR,ELA or combined surgery is a safer and more precise option that preserves the function of the ileocecal region.However,the need for coordination between surgeons and endoscopists,along with the requirement for staged procedures and multiple bowel preparations,increases the complexity of the treatment.In recent years,with the advancement of endoscopic full-thickness resection,endoscopic transcecal appendectomy(ETA)has been used to treat SSLs involving the AO.The use of choledochoscopy in conjunction with ETA can further enhance treatment precision.This integrated approach holds promise for replacing the combined endoscopic and laparoscopic surgical techniques.However,additional data are required to confirm its safety and efficacy.
文摘BACKGROUND Sessile serrated lesions(SSLs)are premalignant polyps implicated in up to 30%of colorectal cancers.Australia reports high SSL detection rates(SSL-DRs),yet with marked variability(3.1%-24%).This substantial variation raises concerns about missed lesions and post-colonoscopy colorectal cancer.This study investigates determinants associated with SSL-DR variation in regional Australia.AIM To study how patient,clinical,and colonoscopy factors are associated with SSL detection in a regional Australian practice.We aimed to contribute high-detection data to the literature by analyzing the association of SSL detection with various determinants.METHODS This retrospective,cross-sectional analysis examined 1450 colonoscopies performed at Port Macquarie Gastroenterology during 2023.Sigmoidoscopies and repeat procedures were excluded.Multivariate logistic regression analyzed associations between SSL detection and patient demographics,clinical indications,procedural factors,and comorbidities.RESULTS The overall SSL-DR was 30.7%.Multivariate analysis identified several independent predictors:Clinical indication,bowel preparation quality,inflammatory bowel disease status,and serrated polyposis syndrome.The faecal occult blood test positive(FOBT)(+)cohort showed the highest predicted SSL detection probability(39.8%),while clinical symptoms showed the lowest(22.3%).After adjustment,SSL detection odds were 2.3 times greater among FOBT(+)patients than those with clinical symptoms(adjusted odds ratio=2.30,95%confidence interval:1.20-4.40,P=0.004).CONCLUSION SSL-DR as a quality indicator requires contextualization regarding clinical indications,bowel preparation quality,and comorbidities.There was a significantly higher prevalence of SSLs in FOBT(+)patients.Despite comprehensive adjustment,this study cannot fully explain the wide SSL-DR variation in Australia,highlighting the need for standardized detection protocols and further research to ensure optimal cancer prevention outcomes.
基金supported by the National Natural Science Foundation of China(Nos.12072220,12102291,and 12225207)the Science and Technology Innovation Teams of Shanxi Province,China(No.202204051002006)the Central Guidance on Local Science and Technology Development Fund of Shanxi Province,China(No.YDZJSX2021B002).
文摘Fe-Cr-Ni austenitic alloys are extensively utilized in the hot-end components of nuclear light water reactors,turbine disks,and gas compressors.However,their low strength at elevated temperatures limits their engineering applications.In this study,a novel precipit-ation-strengthened alloy system is developed by incorporating Al and Si elements into a FeCrNi equiatomic alloy.The results indicate that the FeCrNiAl_(x)Si_(x)(at%,x=0.1,0.2)alloys possess heterogeneous precipitation structures that feature a micron-scaleσphase at the grain boundaries and a nanoscale ordered body-centered cube(B2)phase within the grains.An exceptional strength-ductility synergy across a wide temperature range is achieved in FeCrNiAl_(0.1)Si_(0.1)alloys due to grain refinement and precipitation strengthening.Notably,a yield strength of 693.83 MPa,an ultimate tensile strength of 817.55 MPa,and a uniform elongation of 18.27%are attained at 873 K.The dislo-cation shearing mechanism for B2 phases and the Orowan bypass mechanism forσphase,coupled with a high density of nano-twins and stacking faults in the matrix,contribute to the excellent mechanical properties at cryogenic and ambient temperatures.Moreover,the emergence of serratedσphase and micro-twins in the matrix plays a crucial role in the strengthening and toughening mechanisms at inter-mediate temperatures.This study offers a novel perspective and strategy for the development of precipitation-hardened Fe-Cr-Ni austen-itic alloys with exceptional strength-ductility synergy over a broad temperature range.
基金support from the National Natural Science Foundation of China(Nos.51831002,51904028,and 52233018)the Beijing Municipal Natural Science Foundation(No.2242048)the Fundamental Research Funds for the Central Universities,China(No.FRF-EYIT-23-08).
文摘Plastic instability,including both the discontinuous yielding and stress serrations,has been frequently observed during the tensile deformation of medium-Mn steels(MMnS)and has been intensively studied in recent years.Unfortunately,research results are controversial,and no consensus has been achieved regarding the topic.Here,we first summarize all the possible factors that affect the yielding and flow stress serrations in MMnS,including the morphology and stability of austenite,the feature of the phase interface,and the deformation parameters.Then,we propose a universal mechanism to explain the conflicting experimental results.We conclude that the discontinuous yielding can be attributed to the lack of mobile dislocation before deformation and the rapid dislocation multiplication at the beginning of plastic deformation.Meanwhile,the results show that the stress serrations are formed due to the pinning and depinning between dislocations and interstitial atoms in austenite.Strain-induced martensitic transformation,influenced by the mechanical stability of austenite grain and deformation parameters,should not be the intrinsic cause of plastic instability.However,it can intensify or weaken the discontinuous yielding and the stress serrations by affecting the mobility and density of dislocations,as well as the interaction between the interstitial atoms and dislocations in austenite grains.
文摘The structure and the migration mechanisms of{1012}twin boundaries(TBs)of pure zinc deformed by rolling were studied using high-resolution transmission electron microscopy(HRTEM)at atomic scale.We found the presence of basal/prismatic(BP/PB)planes serrations on{1012}TBs and the coexistence of two kinds of TBs with different structures in the same{1012}twin:TBs composed of{1012}coherent twin boundaries(CTBs)plus short BP/PB serrations,and TBs composed of successive BP/PB segments without{1012}CTBs.The formation of BP/PB serrations has no relation to the c/a ratio of hexagonal-closepacked(HCP)metals because the BP/PB serrations are energetically preferred and geometrically favored.Based on dislocation theory,we proposed the migration mechanisms of the TBs to be the glide of twinning dislocations(TDs)on the CTBs and the climb of interface dislocations(IDs)on the BP/PB segments.
基金supported the National Natural Science Foundation of China(51401129)Natural Science Foundation of Liaoning Province(2019-ZD-0216,20180510056)+2 种基金Foundation of Liaoning Province Education Administration(LQGD2019001)support from the National Science Foundation(DMR1611180 and 1809640)with the program directorssupported by the U.S.Department of Energy,Office of Science,Office of Basic Energy Sciences,Materials Sciences and Engineering Division under Contract No.DEAC02–05-CH11231。
文摘This work intends to manipulate the internal flow units in Zr_(55)Cu_(30)Ni_(5)Al_(10)bulk-metallic glasses(BMGs)through plasma-assisted hydrogenation to generate a positive microalloying effect on plasticity.Based on the cooperative shear model theory,serration-flow statistics during nanoindentation loading and creep tests during the holding stage were used to analyze the influence of hydrogen on the behavior of flow units in BMGs.Experimental observations showed that the hydrogen in the Zr_(55)Cu_(30)Ni_(5)Al_(10)BMGs caused mechanical softening,plasticity improvement,and structural relaxation.Analysis also showed that the average volume,size,and activation energy of internal flow units in the BMGs all increased as a result of the increase in the hydrogen content.The hydrogenation in the BMGs was found to lead to a prolifera-tion of shear bands,which promoted plasticity.The aggregation of these internal flow units reduced the stress required for plastic deformation through shear bands,ultimately causing softening and structural relaxation.
