Variable stiffness composites present a promising solution for mitigating impact loads via varying the fiber volume fraction layer-wise,thereby adjusting the panel's stiffness.Since each layer of the composite may...Variable stiffness composites present a promising solution for mitigating impact loads via varying the fiber volume fraction layer-wise,thereby adjusting the panel's stiffness.Since each layer of the composite may be affected by a different failure mode,the optimal fiber volume fraction to suppress damage initiation and evolution is different across the layers.This research examines how re-allocating the fibers layer-wise enhances the composites'impact resistance.In this study,constant stiffness panels with the same fiber volume fraction throughout the layers are compared to variable stiffness ones by varying volume fraction layer-wise.A method is established that utilizes numerical analysis coupled with optimization techniques to determine the optimal fiber volume fraction in both scenarios.Three different reinforcement fibers(Kevlar,carbon,and glass)embedded in epoxy resin were studied.Panels were manufactured and tested under various loading conditions to validate results.Kevlar reinforcement revealed the highest tensile toughness,followed by carbon and then glass fibers.Varying reinforcement volume fraction significantly influences failure modes.Higher fractions lead to matrix cracking and debonding,while lower fractions result in more fiber breakage.The optimal volume fraction for maximizing fiber breakage energy is around 45%,whereas it is about 90%for matrix cracking and debonding.A drop tower test was used to examine the composite structure's behavior under lowvelocity impact,confirming the superiority of Kevlar-reinforced composites with variable stiffness.Conversely,glass-reinforced composites with constant stiffness revealed the lowest performance with the highest deflection.Across all reinforcement materials,the variable stiffness structure consistently outperformed its constant stiffness counterpart.展开更多
By introducing geological and natural conditions of Shuangtaizi Estuary Wetland,a national nature reserve,and borrowing Landsat5 TM wetland data of the year 1987 and 2005,the core area of Shuangtaizi Estuary Wetland i...By introducing geological and natural conditions of Shuangtaizi Estuary Wetland,a national nature reserve,and borrowing Landsat5 TM wetland data of the year 1987 and 2005,the core area of Shuangtaizi Estuary Wetland is studied,areas of its natural water,mudflat,seepweed beach,culture zone,reservoir and swag,reed field,rice field and non-wetland landscape are respectively analyzed,as well as the changes of wetland community,water quality,waterfowl quantity and species.It is found that the study area is suffering from serious fragmentation of wetland,reducing reed yield,degrading water quality,decreasing bird species and amount,which implies that the degraded wetland environment has imposed threats on the survival of some wetland species.Root causes of such a result are analyzed from the perspectives of regional climate changes and human interventions;while regional climate changes include obvious temperature increase and precipitation decrease,human interventions include oil exploration,reclamation of land from the lake,overuse of biotic resources,environment pollution.Due to the interactive influence of these two factors,ecosystem of Shuangtaizi Estuary Wetland has experienced drastic changes,which should be attached sufficient importance by relevant departments so as to enhance its protection and management.展开更多
Quenched and tempered steels are prone to hydrogen induced cracking in the heat affected zone after welding. The use of austenitic stainless steel consumables to weld the above steel was the only available remedy beca...Quenched and tempered steels are prone to hydrogen induced cracking in the heat affected zone after welding. The use of austenitic stainless steel consumables to weld the above steel was the only available remedy because of higher solubility for hydrogen in austenitic phase. In this investigation, an attempt was made to determine a suitable consumable to replace expensive austenitic consumables. Two different consumables, namely, austenitie stain less steel and low hydrogen ferritic steel, were used to fabricate the joints by shielded metal are welding （SMAW） and flux cored arc welding （FCAW） processes. The joints fabricated by using low hydrogen ferritic steel consumables showed superior transverse tensile properties, whereas joints fabricated by using austenitic stainless steel consumables exhibited better impact toughness, irrespective of the welding process used. The SMAW joints exhibited superior mechanical and impact properties, irrespective of the consumables used, than their FCAW counterparts.展开更多
No failure, moderate failure, severe failure, and slight failure are the four failure modes generalized observed in the dynamic response of the single-layer reticulated dome under vertical impact load on apex. TE (the...No failure, moderate failure, severe failure, and slight failure are the four failure modes generalized observed in the dynamic response of the single-layer reticulated dome under vertical impact load on apex. TE (the time that the end of impact force) and TF (the time that members are broken) are two key times in the failure process. Characteristics of dynamic responses at the two key times are shown in order to make the failure mechanism clear. Then three steps of energy transfer are summarized, i.e. energy applying, energy loss and energy transfer, energy consump-tion. Based on the three steps, energy transfer process for the failure reticulated dome under once impact is introduced. Energy transmissibility and local loss ratio are put forward firstly to obtain EL F(the energy left in the main reticulated dome) from the initial kinetic energy of impactor. More-over, the distribution of failure modes is decided by EL F which leads to the maximum dynamic re-sponse of the reticulated dome, but not by the initial impact kinetic energy of impactor.展开更多
The present article aims at elucidating the effect of thermo-mechanical controlled processing(TMCP), especially the finish cooling temperature, on microstructure and mechanical properties of high strength low alloy st...The present article aims at elucidating the effect of thermo-mechanical controlled processing(TMCP), especially the finish cooling temperature, on microstructure and mechanical properties of high strength low alloy steels for developing superior low temperature toughness construction steel. The microstructural features were characterized by scanning electron microscope equipped with electron backscatter diffraction, and the mechanical behaviors in terms of tensile properties and impact toughness were analyzed in correlation with microstructural evolution. The results showed that the lower finish cooling temperature could lead to a considerable increase in impact toughness for this steel. A mixed microstructure was obtained by TMCP at lower finish cooling temperature, which contained much fine lath-like bainite with dot-shaped M/A constituent and less granular bainite and bainite ferrite. In this case, this steel possesses yield and ultimate tensile strengths of ~ 885 MPa and 1089 MPa, respectively, and a total elongation of ~ 15.3%, while it has a lower yield ratio of ~ 0.81. The superior impact toughness of ~ 89 J at-20 °C was obtained, and this was resulted from the multi-phase microstructure including grain refinement, preferred grain boundaries misorientation, fine lath-like bainite with dot-shaped M/A constituent.展开更多
Semi-solid processing of A380 aluminum alloy was performed by gas induced semi-solid(GISS)process.The effects of argon inert gas flow rate,starting temperature and duration of gas purging as key GISS parameters and al...Semi-solid processing of A380 aluminum alloy was performed by gas induced semi-solid(GISS)process.The effects of argon inert gas flow rate,starting temperature and duration of gas purging as key GISS parameters and also modification with Sr on the structural refinements,hardness and impact strength of GISS alloys were investigated.Microstructural evolution shows that there is an important effect of the pouring temperature and Sr addition on the morphology and size of primaryα(A1)in the alloy to change from coarse dendritic to fine globular structure.The best sample which has fine grains of 51.18μm in average size and a high level of globularity of 0.89 is achieved from a GISS processing of Sr modified alloy in which the gas purging started at 610℃.The impact strength of the GISS optimized samples((4.67±0.18)J/cm^(2))shows an increase of about 40%with respect to the as-cast sample due to the globular structure and fibrous Si morphology.Moreover,the hardness of the optimized GISS sample((89.34±2.85)HB)increases to(93.84±3.14)HB by modification with the Sr and GISS process.The fracture surface of Sr modified alloy is also dominated by complex topography showing typical ductile fracture features.展开更多
Split Hopkinson pressure bar(SHPB)has been used to study the dynamic failure pattern of flattened mortar Brazilian disc under impact load.Each disc contains several prefabricated cracks paralleled to each other.Dynami...Split Hopkinson pressure bar(SHPB)has been used to study the dynamic failure pattern of flattened mortar Brazilian disc under impact load.Each disc contains several prefabricated cracks paralleled to each other.Dynamic FEM has also been adopted to simulate such failure behavior.The mechanism of crack initiation,propagation and cut-through have been scrutinized with both experimental and numerical approaches.Influence of the number of the prefabricated cracks on the specimen strength and acoustic emission(AE)performance can be observed and studied.The results show that the strength decreases and AE counts increases,when the number of the prefabricated cracks increases.展开更多
BACKGROUND Journal Impact Factor™(JIF)is often used to evaluate the relative reputation and quality of academic journals in their respective fields,and can greatly influence the quality and scope of subsequent manuscr...BACKGROUND Journal Impact Factor™(JIF)is often used to evaluate the relative reputation and quality of academic journals in their respective fields,and can greatly influence the quality and scope of subsequent manuscript submissions.Therefore,many if not all academic journals are interested in increasing their JIF,to improve their academic impact.AIM To determine the importance of the integrity of the editorial and publication process in improving the academic influence of academic journals and the JIF of academic journals.METHODS In this paper,we describe our statistical analysis of bibliometric factors-including the 2021 JIFs released in the Journal Citation Report™2022,discipline rankings,received and published articles in 2019-2021,and webpage visits and downloads-for seven journals published by Baishideng Publishing Group(Baishideng)and indexed in Science Citation Index Expanded™;ultimately,we introduce and discuss the editing and publishing processes of Baishideng’s journals in their entirety,as they form the basis for our objective of safeguarding and bolstering integrity in academic publication.RESULTS For the seven journals assessed,their 2021 JIFs were basically unchanged from 2020,with the current metric ranging from 5.374 for World Journal of Gastroenterology(WJG)to 1.534 for World Journal of Clinical Cases(WJCC).Further assessments of the journals’bibliometrics from 2019 to 2020,showed that World Journal of Stem Cells has the highest self-citation rate(1.43%)and World Journal of Gastrointestinal Surgery has the lowest(0.21%).Additionally,the total 3012 articles published during this period were cited by more than 20000 articles in approximately 8000 academic journals.Of note,the 1102 articles published in WJG were cited by articles in 3059 journals,among which 171 journals have a JIF of>10,including internationally renowned academic journals such as CA-A Cancer Journal for Clinicians(2021 JIF 286.130,record count:1),Lancet(2021 JIF 202.731,record count:4),Nature Reviews Immunology(2021 JIF 108.555,record count:2),Nature Reviews Gastroenterology&Hepatology(2021 JIF 73.082,record count:9),Lancet Gastroenterology&Hepatology(2021 JIF 45.042,record count:8),Gastroenterology(2021 JIF 33.883,record count:19),and Gut(2021 JIF 31.793,record count:21).This suggests that Baishideng’s journals have been widely recognized for their academic quality.In the Reference Citation Analysis(RCA)database,all seven Baishidengpublished journals obtained a 2022 Journal Article Influence Index(JAII).For example,WJG has a 2022 JAII of 22.048,ranking 18th out of 102 journals in the field of gastroenterology&hepatology in the RCA,with 469909 total citations(6/102)and 21313 total articles(5/102).The numbers of manuscripts received and published in 2021 were both higher than those in 2019-2020.For example,WJCC received a total of 3650 manuscripts in 2021,which is 91.1%higher than those in 2019-2020(average:1910 papers/year).In 2021,WJCC published 1296 articles,representing an increase of 105.1%compared to those in 2019-2020(average:632 articles/year).The numbers of webpage visits and downloads received by the seven journals have increased year by year.For example,the number of total visits received by WJG in 2019-2021 was 1974052 in 2019,2317835 in 2020(increased by 17.4%compared with that in 2019),and 2652555 in 2021(increased by 4.4%compared with that in 2020).The visitors were from more than 220 countries and regions worldwide,such as the United States,China,and the United Kingdom.Open access(OA)plays a vital role in improving the quality,efficiency,transparency,and integrity of academic journal publishing.From 2019 to 2021,a total of 5543 OA articles were published in the seven journals,of which 2083(37.6%)were invited and published free-of-charge.During the same period,1683 articles were published in WJG,and the authors were from more than 70 countries and regions.For the total 5543 articles published in the seven journals from 2019 to 2021,3903 article quality tracking reports were received after the online publication of these articles.The quality of the articles was further evaluated through the Baishideng’s article quality and author evaluation tracking system,with 4655 articles(84.0%)having received author evaluation and feedback,which contributes to tracking metrics for authors’satisfaction with the collective publication processes.From March 25,2021 to June 28,2022,the seven journals received a total of 424 reader evaluations and 229 letters from readers;this subsequent reader engagement demonstrates that the popularity of the published articles and the volume of their readership audience were improved through the reader evaluation system.CONCLUSION Ultimately,the findings from our bibliometric assessments indicate that establishing,promoting and actively practicing processes that safeguard and bolster the integrity of the editing and publication process also help to improve the academic influence of academic journals,which itself is the cornerstone for improving JIF.展开更多
A methodology is presented to identify environmental impact minimization alternatives for reaction processes and assess their environmental performance. The potential environmental impact (PEI) scheme can be used to v...A methodology is presented to identify environmental impact minimization alternatives for reaction processes and assess their environmental performance. The potential environmental impact (PEI) scheme can be used to visibly display the transformation relationships among different types of PEI, identify the sources of environmental impacts, and propose alternatives for eliminating or minimizing the impacts. To evaluate the environmental performance of the alternatives effectively, some new indices, such as PEI input rate of non-products, PEI output rate of non-products per profit and the PEI conversion efficiency are proposed. Finally, the application of the methodology is illustrated using an industrial case study.展开更多
Upper Triassic sedimentary systems of both the Arabian Plate and the Germanic Basin reveal climate- and plate tectonic-forced effects through certain time-intervals experienced by architectural elements, lithofacies t...Upper Triassic sedimentary systems of both the Arabian Plate and the Germanic Basin reveal climate- and plate tectonic-forced effects through certain time-intervals experienced by architectural elements, lithofacies types, unconformities, flash flood deposits, maximum flooding surfaces/sequence boundary (MFS/SB), mineralogy, and isotope anomalies. Further, Moon recession and changes of Earth’s rotation velocity (core/mantle boundary) are associated with multiple impacting and large igneous provinces/Mid Oceanic Ridge Basalt, LIP/MORB-rifting/degassing. While acidification (by degassing, sturz-rain) does influence tectosilicates and carbonates, montmorillonite represents a key mineral as transformation of volcanic/impact glass (Tephra) to be found as co-components in and in certain pelite units as “boundary clay-suspicions” (mixture of eolian paleoloess, pelite, paleosol, and tephra → tuffite). Obviously, unconformities and sequence boundaries of both study areas separate and dislocate interrupted ∂<sup>13</sup>C and <sup>87</sup>Sr/<sup>86</sup>Sr-data groups along the isotope curves. Both Proto-Arctic Ocean rifting/degassing comprising kimberlitic pyroclastic eruptions and Neotethys rifting/degassing as well as multiple impacting played the most important role during the Norian, followed by the incipient Central Atlantic Magmatic Provinces rifting since the Rhaetian. The following associations are encountered and dealt with in this study: Sequence boundaries-∂<sup>13</sup>C, maximum flooding surfaces-(FUCs)-∂<sup>13</sup>C, unconformities-plate motion, tephra-pelite-tuffite-montmorillonite. Norian: maximum flooding surfaces (MFSs)-“paleosol”/boundary clay?-rifting-volcanism, Moon/Earth data change. So the Norian (~221 - 206 Ma) hosts anomalous “amalgamated maximum flooding surfaces (MFSs)”, amalgamated paleosol (Jordanian Platform), multiple impacting (~219 - 214 Ma), the maximum opening of the Proto-Arctic Ocean (PAO) (~230 - 200 Ma), Neo-Tethys (NT)-subvolcanic (sills, dikes) in the NE Dead Sea area prior the Rhaetian, and a significant change of Earth/Moon relation data. The study concludes that rare and extreme events are very strongly shaping the geologic constellations in the Earth System.展开更多
Multiply charged ions of Ar and NO were observed in MPI experiment Of NO/Ar with TOF-MS. A delayable pulsed acceleration field wn applied tO investigate the effect of the photoelectrons on the formation of the multi...Multiply charged ions of Ar and NO were observed in MPI experiment Of NO/Ar with TOF-MS. A delayable pulsed acceleration field wn applied tO investigate the effect of the photoelectrons on the formation of the multiply charged ions. The multiply charged ions were suggested to be produced by photoelectron impact ionization, in the region bentween the extractor grid and the repeller plate, step by step, from neutral species and lower charged ions. The 50-60ns of FWHM of the ion peaks implies that the pulse width of the photoelectrons should be shorter considering the broadening effect during the ionization process.展开更多
Caffeine is a widely consumed stimulant known for its cardiovascular and metabolic effects.However,its impact on cardiovascular risk,including arrhythmias,in older adults remains underexplored.Emerging evidence highli...Caffeine is a widely consumed stimulant known for its cardiovascular and metabolic effects.However,its impact on cardiovascular risk,including arrhythmias,in older adults remains underexplored.Emerging evidence highlights sex-specific differences in caffeine metabolism,which may influence its role in cardiovascular health.This perspective examines the interaction between caffeine,hormonal changes,metabolic processes,and lifestyle factors,focusing on older women compared to men.Understanding these differences is essential for tailoring dietary and clinical recommendations to mitigate cardiovascular risks and promote healthy aging.展开更多
Low temperature mechanical properties of AZ91D magnesium alloy fabricated by solid recycling process from recycled scraps were studied. Various microstructural analyses were performed using optical microscopy （OM） a...Low temperature mechanical properties of AZ91D magnesium alloy fabricated by solid recycling process from recycled scraps were studied. Various microstructural analyses were performed using optical microscopy （OM） and scanning electron microscopy （SEM）. The recycled specimens consist of fine grains due to dynamic recrystallization and the interfaces of original individual scraps are not identified. Tensile tests were performed at a strain rate of 5 x 10 3 s 1 at room temperature （27 ~C）, -70, -100 and 130 ~C, respectively. Ultimate tensile strength of the specimens increases slightly with decreasing the tensile temperature, and elongation to failure decreases with decreasing the tensile temperature. The tensile specimens at -130 ~C show the highest ultimate tensile strength of 360.65 MPa and the lowest elongation to failure of 5.46%. Impact tests were performed at room temperature （27 ~C）, -70 and -130 ~C, respectively. Impact toughness decreases with decreasing the impact temperature. The impact specimens at -130 ~C show the lowest impact toughness of 3.06 J/cm2.展开更多
篮球运动员落地过程中气垫运动鞋对足部冲击负荷的影响分析容易受到噪声信号的影响,导致分析结果不精准。为了解决该问题,提出了冲击负荷影响分析方法,评估气垫运动鞋对足部冲击负荷影响相关的动态特性。根据触地阶段足部加速度信号和...篮球运动员落地过程中气垫运动鞋对足部冲击负荷的影响分析容易受到噪声信号的影响,导致分析结果不精准。为了解决该问题,提出了冲击负荷影响分析方法,评估气垫运动鞋对足部冲击负荷影响相关的动态特性。根据触地阶段足部加速度信号和软组织应力响应信号的自身频谱和交互频谱关联关系,结合快速傅里叶变换(Fast Fourier Transform,FFT)能够将时域信号转换为频域信号,更容易识别和滤除噪声信号。结合自身频谱、交互频谱,构建冲击负荷判断式,以分析气垫运动鞋对足部冲击负荷的影响。试验结果表明,气垫运动鞋对第一趾骨的冲击力较大,左足、右足的最大负荷值分别为34、33 k N,对第五趾骨的冲击力较小,左足、右足的最小负荷值分别为3、2 k N,该方法能够精准地分析气垫运动鞋对足部冲击负荷的影响。展开更多
基金funded by the American University of Sharjah.United Arab Emirates award number EN 9502-FRG19-M-E75。
文摘Variable stiffness composites present a promising solution for mitigating impact loads via varying the fiber volume fraction layer-wise,thereby adjusting the panel's stiffness.Since each layer of the composite may be affected by a different failure mode,the optimal fiber volume fraction to suppress damage initiation and evolution is different across the layers.This research examines how re-allocating the fibers layer-wise enhances the composites'impact resistance.In this study,constant stiffness panels with the same fiber volume fraction throughout the layers are compared to variable stiffness ones by varying volume fraction layer-wise.A method is established that utilizes numerical analysis coupled with optimization techniques to determine the optimal fiber volume fraction in both scenarios.Three different reinforcement fibers(Kevlar,carbon,and glass)embedded in epoxy resin were studied.Panels were manufactured and tested under various loading conditions to validate results.Kevlar reinforcement revealed the highest tensile toughness,followed by carbon and then glass fibers.Varying reinforcement volume fraction significantly influences failure modes.Higher fractions lead to matrix cracking and debonding,while lower fractions result in more fiber breakage.The optimal volume fraction for maximizing fiber breakage energy is around 45%,whereas it is about 90%for matrix cracking and debonding.A drop tower test was used to examine the composite structure's behavior under lowvelocity impact,confirming the superiority of Kevlar-reinforced composites with variable stiffness.Conversely,glass-reinforced composites with constant stiffness revealed the lowest performance with the highest deflection.Across all reinforcement materials,the variable stiffness structure consistently outperformed its constant stiffness counterpart.
基金Supported by National Natural Science Foundation(40871259)~~
文摘By introducing geological and natural conditions of Shuangtaizi Estuary Wetland,a national nature reserve,and borrowing Landsat5 TM wetland data of the year 1987 and 2005,the core area of Shuangtaizi Estuary Wetland is studied,areas of its natural water,mudflat,seepweed beach,culture zone,reservoir and swag,reed field,rice field and non-wetland landscape are respectively analyzed,as well as the changes of wetland community,water quality,waterfowl quantity and species.It is found that the study area is suffering from serious fragmentation of wetland,reducing reed yield,degrading water quality,decreasing bird species and amount,which implies that the degraded wetland environment has imposed threats on the survival of some wetland species.Root causes of such a result are analyzed from the perspectives of regional climate changes and human interventions;while regional climate changes include obvious temperature increase and precipitation decrease,human interventions include oil exploration,reclamation of land from the lake,overuse of biotic resources,environment pollution.Due to the interactive influence of these two factors,ecosystem of Shuangtaizi Estuary Wetland has experienced drastic changes,which should be attached sufficient importance by relevant departments so as to enhance its protection and management.
文摘Quenched and tempered steels are prone to hydrogen induced cracking in the heat affected zone after welding. The use of austenitic stainless steel consumables to weld the above steel was the only available remedy because of higher solubility for hydrogen in austenitic phase. In this investigation, an attempt was made to determine a suitable consumable to replace expensive austenitic consumables. Two different consumables, namely, austenitie stain less steel and low hydrogen ferritic steel, were used to fabricate the joints by shielded metal are welding （SMAW） and flux cored arc welding （FCAW） processes. The joints fabricated by using low hydrogen ferritic steel consumables showed superior transverse tensile properties, whereas joints fabricated by using austenitic stainless steel consumables exhibited better impact toughness, irrespective of the welding process used. The SMAW joints exhibited superior mechanical and impact properties, irrespective of the consumables used, than their FCAW counterparts.
基金Supported by National Natural Science Foundation of China(No.90715034)
文摘No failure, moderate failure, severe failure, and slight failure are the four failure modes generalized observed in the dynamic response of the single-layer reticulated dome under vertical impact load on apex. TE (the time that the end of impact force) and TF (the time that members are broken) are two key times in the failure process. Characteristics of dynamic responses at the two key times are shown in order to make the failure mechanism clear. Then three steps of energy transfer are summarized, i.e. energy applying, energy loss and energy transfer, energy consump-tion. Based on the three steps, energy transfer process for the failure reticulated dome under once impact is introduced. Energy transmissibility and local loss ratio are put forward firstly to obtain EL F(the energy left in the main reticulated dome) from the initial kinetic energy of impactor. More-over, the distribution of failure modes is decided by EL F which leads to the maximum dynamic re-sponse of the reticulated dome, but not by the initial impact kinetic energy of impactor.
基金financially supported by the National Natural Science Foundation of China(Grant No.51904071)the Independent Project of State Key Laboratory of Rolling and Automation,Northeastern University(Grant No.ZZ202001)+1 种基金the Key Research and Development Program of Hebei Province of China(Grant No.18211019D)the Start-up Project of Doctor Scientific Research of Liaoning Province(Grant No.2020-BS-271)。
文摘The present article aims at elucidating the effect of thermo-mechanical controlled processing(TMCP), especially the finish cooling temperature, on microstructure and mechanical properties of high strength low alloy steels for developing superior low temperature toughness construction steel. The microstructural features were characterized by scanning electron microscope equipped with electron backscatter diffraction, and the mechanical behaviors in terms of tensile properties and impact toughness were analyzed in correlation with microstructural evolution. The results showed that the lower finish cooling temperature could lead to a considerable increase in impact toughness for this steel. A mixed microstructure was obtained by TMCP at lower finish cooling temperature, which contained much fine lath-like bainite with dot-shaped M/A constituent and less granular bainite and bainite ferrite. In this case, this steel possesses yield and ultimate tensile strengths of ~ 885 MPa and 1089 MPa, respectively, and a total elongation of ~ 15.3%, while it has a lower yield ratio of ~ 0.81. The superior impact toughness of ~ 89 J at-20 °C was obtained, and this was resulted from the multi-phase microstructure including grain refinement, preferred grain boundaries misorientation, fine lath-like bainite with dot-shaped M/A constituent.
文摘Semi-solid processing of A380 aluminum alloy was performed by gas induced semi-solid(GISS)process.The effects of argon inert gas flow rate,starting temperature and duration of gas purging as key GISS parameters and also modification with Sr on the structural refinements,hardness and impact strength of GISS alloys were investigated.Microstructural evolution shows that there is an important effect of the pouring temperature and Sr addition on the morphology and size of primaryα(A1)in the alloy to change from coarse dendritic to fine globular structure.The best sample which has fine grains of 51.18μm in average size and a high level of globularity of 0.89 is achieved from a GISS processing of Sr modified alloy in which the gas purging started at 610℃.The impact strength of the GISS optimized samples((4.67±0.18)J/cm^(2))shows an increase of about 40%with respect to the as-cast sample due to the globular structure and fibrous Si morphology.Moreover,the hardness of the optimized GISS sample((89.34±2.85)HB)increases to(93.84±3.14)HB by modification with the Sr and GISS process.The fracture surface of Sr modified alloy is also dominated by complex topography showing typical ductile fracture features.
基金Funded by the National Natural Science Foundation of China(Nos.51678170,51878190)。
文摘Split Hopkinson pressure bar(SHPB)has been used to study the dynamic failure pattern of flattened mortar Brazilian disc under impact load.Each disc contains several prefabricated cracks paralleled to each other.Dynamic FEM has also been adopted to simulate such failure behavior.The mechanism of crack initiation,propagation and cut-through have been scrutinized with both experimental and numerical approaches.Influence of the number of the prefabricated cracks on the specimen strength and acoustic emission(AE)performance can be observed and studied.The results show that the strength decreases and AE counts increases,when the number of the prefabricated cracks increases.
文摘BACKGROUND Journal Impact Factor™(JIF)is often used to evaluate the relative reputation and quality of academic journals in their respective fields,and can greatly influence the quality and scope of subsequent manuscript submissions.Therefore,many if not all academic journals are interested in increasing their JIF,to improve their academic impact.AIM To determine the importance of the integrity of the editorial and publication process in improving the academic influence of academic journals and the JIF of academic journals.METHODS In this paper,we describe our statistical analysis of bibliometric factors-including the 2021 JIFs released in the Journal Citation Report™2022,discipline rankings,received and published articles in 2019-2021,and webpage visits and downloads-for seven journals published by Baishideng Publishing Group(Baishideng)and indexed in Science Citation Index Expanded™;ultimately,we introduce and discuss the editing and publishing processes of Baishideng’s journals in their entirety,as they form the basis for our objective of safeguarding and bolstering integrity in academic publication.RESULTS For the seven journals assessed,their 2021 JIFs were basically unchanged from 2020,with the current metric ranging from 5.374 for World Journal of Gastroenterology(WJG)to 1.534 for World Journal of Clinical Cases(WJCC).Further assessments of the journals’bibliometrics from 2019 to 2020,showed that World Journal of Stem Cells has the highest self-citation rate(1.43%)and World Journal of Gastrointestinal Surgery has the lowest(0.21%).Additionally,the total 3012 articles published during this period were cited by more than 20000 articles in approximately 8000 academic journals.Of note,the 1102 articles published in WJG were cited by articles in 3059 journals,among which 171 journals have a JIF of>10,including internationally renowned academic journals such as CA-A Cancer Journal for Clinicians(2021 JIF 286.130,record count:1),Lancet(2021 JIF 202.731,record count:4),Nature Reviews Immunology(2021 JIF 108.555,record count:2),Nature Reviews Gastroenterology&Hepatology(2021 JIF 73.082,record count:9),Lancet Gastroenterology&Hepatology(2021 JIF 45.042,record count:8),Gastroenterology(2021 JIF 33.883,record count:19),and Gut(2021 JIF 31.793,record count:21).This suggests that Baishideng’s journals have been widely recognized for their academic quality.In the Reference Citation Analysis(RCA)database,all seven Baishidengpublished journals obtained a 2022 Journal Article Influence Index(JAII).For example,WJG has a 2022 JAII of 22.048,ranking 18th out of 102 journals in the field of gastroenterology&hepatology in the RCA,with 469909 total citations(6/102)and 21313 total articles(5/102).The numbers of manuscripts received and published in 2021 were both higher than those in 2019-2020.For example,WJCC received a total of 3650 manuscripts in 2021,which is 91.1%higher than those in 2019-2020(average:1910 papers/year).In 2021,WJCC published 1296 articles,representing an increase of 105.1%compared to those in 2019-2020(average:632 articles/year).The numbers of webpage visits and downloads received by the seven journals have increased year by year.For example,the number of total visits received by WJG in 2019-2021 was 1974052 in 2019,2317835 in 2020(increased by 17.4%compared with that in 2019),and 2652555 in 2021(increased by 4.4%compared with that in 2020).The visitors were from more than 220 countries and regions worldwide,such as the United States,China,and the United Kingdom.Open access(OA)plays a vital role in improving the quality,efficiency,transparency,and integrity of academic journal publishing.From 2019 to 2021,a total of 5543 OA articles were published in the seven journals,of which 2083(37.6%)were invited and published free-of-charge.During the same period,1683 articles were published in WJG,and the authors were from more than 70 countries and regions.For the total 5543 articles published in the seven journals from 2019 to 2021,3903 article quality tracking reports were received after the online publication of these articles.The quality of the articles was further evaluated through the Baishideng’s article quality and author evaluation tracking system,with 4655 articles(84.0%)having received author evaluation and feedback,which contributes to tracking metrics for authors’satisfaction with the collective publication processes.From March 25,2021 to June 28,2022,the seven journals received a total of 424 reader evaluations and 229 letters from readers;this subsequent reader engagement demonstrates that the popularity of the published articles and the volume of their readership audience were improved through the reader evaluation system.CONCLUSION Ultimately,the findings from our bibliometric assessments indicate that establishing,promoting and actively practicing processes that safeguard and bolster the integrity of the editing and publication process also help to improve the academic influence of academic journals,which itself is the cornerstone for improving JIF.
基金National Natural Science Foundation of China(No.20176045)Major State Basic Research Development Program(No.G20000263)
文摘A methodology is presented to identify environmental impact minimization alternatives for reaction processes and assess their environmental performance. The potential environmental impact (PEI) scheme can be used to visibly display the transformation relationships among different types of PEI, identify the sources of environmental impacts, and propose alternatives for eliminating or minimizing the impacts. To evaluate the environmental performance of the alternatives effectively, some new indices, such as PEI input rate of non-products, PEI output rate of non-products per profit and the PEI conversion efficiency are proposed. Finally, the application of the methodology is illustrated using an industrial case study.
文摘Upper Triassic sedimentary systems of both the Arabian Plate and the Germanic Basin reveal climate- and plate tectonic-forced effects through certain time-intervals experienced by architectural elements, lithofacies types, unconformities, flash flood deposits, maximum flooding surfaces/sequence boundary (MFS/SB), mineralogy, and isotope anomalies. Further, Moon recession and changes of Earth’s rotation velocity (core/mantle boundary) are associated with multiple impacting and large igneous provinces/Mid Oceanic Ridge Basalt, LIP/MORB-rifting/degassing. While acidification (by degassing, sturz-rain) does influence tectosilicates and carbonates, montmorillonite represents a key mineral as transformation of volcanic/impact glass (Tephra) to be found as co-components in and in certain pelite units as “boundary clay-suspicions” (mixture of eolian paleoloess, pelite, paleosol, and tephra → tuffite). Obviously, unconformities and sequence boundaries of both study areas separate and dislocate interrupted ∂<sup>13</sup>C and <sup>87</sup>Sr/<sup>86</sup>Sr-data groups along the isotope curves. Both Proto-Arctic Ocean rifting/degassing comprising kimberlitic pyroclastic eruptions and Neotethys rifting/degassing as well as multiple impacting played the most important role during the Norian, followed by the incipient Central Atlantic Magmatic Provinces rifting since the Rhaetian. The following associations are encountered and dealt with in this study: Sequence boundaries-∂<sup>13</sup>C, maximum flooding surfaces-(FUCs)-∂<sup>13</sup>C, unconformities-plate motion, tephra-pelite-tuffite-montmorillonite. Norian: maximum flooding surfaces (MFSs)-“paleosol”/boundary clay?-rifting-volcanism, Moon/Earth data change. So the Norian (~221 - 206 Ma) hosts anomalous “amalgamated maximum flooding surfaces (MFSs)”, amalgamated paleosol (Jordanian Platform), multiple impacting (~219 - 214 Ma), the maximum opening of the Proto-Arctic Ocean (PAO) (~230 - 200 Ma), Neo-Tethys (NT)-subvolcanic (sills, dikes) in the NE Dead Sea area prior the Rhaetian, and a significant change of Earth/Moon relation data. The study concludes that rare and extreme events are very strongly shaping the geologic constellations in the Earth System.
文摘Multiply charged ions of Ar and NO were observed in MPI experiment Of NO/Ar with TOF-MS. A delayable pulsed acceleration field wn applied tO investigate the effect of the photoelectrons on the formation of the multiply charged ions. The multiply charged ions were suggested to be produced by photoelectron impact ionization, in the region bentween the extractor grid and the repeller plate, step by step, from neutral species and lower charged ions. The 50-60ns of FWHM of the ion peaks implies that the pulse width of the photoelectrons should be shorter considering the broadening effect during the ionization process.
文摘Caffeine is a widely consumed stimulant known for its cardiovascular and metabolic effects.However,its impact on cardiovascular risk,including arrhythmias,in older adults remains underexplored.Emerging evidence highlights sex-specific differences in caffeine metabolism,which may influence its role in cardiovascular health.This perspective examines the interaction between caffeine,hormonal changes,metabolic processes,and lifestyle factors,focusing on older women compared to men.Understanding these differences is essential for tailoring dietary and clinical recommendations to mitigate cardiovascular risks and promote healthy aging.
基金Projects(50674038,50974048)supported by the National Natural Science Foundation of ChinaProject(200802140004)supported by Doctoral Fund of Ministry of Education of China
文摘Low temperature mechanical properties of AZ91D magnesium alloy fabricated by solid recycling process from recycled scraps were studied. Various microstructural analyses were performed using optical microscopy （OM） and scanning electron microscopy （SEM）. The recycled specimens consist of fine grains due to dynamic recrystallization and the interfaces of original individual scraps are not identified. Tensile tests were performed at a strain rate of 5 x 10 3 s 1 at room temperature （27 ~C）, -70, -100 and 130 ~C, respectively. Ultimate tensile strength of the specimens increases slightly with decreasing the tensile temperature, and elongation to failure decreases with decreasing the tensile temperature. The tensile specimens at -130 ~C show the highest ultimate tensile strength of 360.65 MPa and the lowest elongation to failure of 5.46%. Impact tests were performed at room temperature （27 ~C）, -70 and -130 ~C, respectively. Impact toughness decreases with decreasing the impact temperature. The impact specimens at -130 ~C show the lowest impact toughness of 3.06 J/cm2.
文摘篮球运动员落地过程中气垫运动鞋对足部冲击负荷的影响分析容易受到噪声信号的影响,导致分析结果不精准。为了解决该问题,提出了冲击负荷影响分析方法,评估气垫运动鞋对足部冲击负荷影响相关的动态特性。根据触地阶段足部加速度信号和软组织应力响应信号的自身频谱和交互频谱关联关系,结合快速傅里叶变换(Fast Fourier Transform,FFT)能够将时域信号转换为频域信号,更容易识别和滤除噪声信号。结合自身频谱、交互频谱,构建冲击负荷判断式,以分析气垫运动鞋对足部冲击负荷的影响。试验结果表明,气垫运动鞋对第一趾骨的冲击力较大,左足、右足的最大负荷值分别为34、33 k N,对第五趾骨的冲击力较小,左足、右足的最小负荷值分别为3、2 k N,该方法能够精准地分析气垫运动鞋对足部冲击负荷的影响。
