The level of genetic variation within a breeding population affects the effectiveness of selection strategies for genetic improvement.The relationship between genetic variation level within Pinus tabuliformis breeding...The level of genetic variation within a breeding population affects the effectiveness of selection strategies for genetic improvement.The relationship between genetic variation level within Pinus tabuliformis breeding populations and selection strategies or selection effectiveness is not fully investigated.Here,we compared the selection effectiveness of combined and individual direct selection strategies using half-and full-sib families produced from advanced-generation P.tabuliformis seed orchard as our test populations.Our results revealed that,within half-sib families,average diameter at breast height(DBH),tree height,and volume growth of superior individuals selected by the direct selection strategy were higher by 7.72%,18.56%,and 31.01%,respectively,than those selected by the combined selection strategy.Furthermore,significant differences(P<0.01)were observed between the two strategies in terms of the expected genetic gains for average tree height and volume.In contrast,within full-sib families,the differences in tree average DBH,height,and volume between the two selection strategies were relatively minor with increase of 0.17%,2.73%,and 2.21%,respectively,and no significant differences were found in the average expected genetic gains for the studied traits.Half-sib families exhibited greater phenotypic and genetic variation,resulting in improved selection efficiency with the direct selection strategy but also introduced a level of inbreeding risk.Based on genetic distance estimates using molecular markers,our comparative seed orchard design analysis showed that the Improved Adaptive Genetic Programming Algorithm(IAPGA)reduced the average inbreeding coefficient by 14.36% and 14.73% compared to sequential and random designs,respectively.In conclusion,the combination of the direct selection strategy with IAPGA seed orchard design aimed at minimizing inbreeding offered an efficient approach for establishing advanced-generation P.tabuliformis seed orchards.展开更多
Ethanol synthesis via dimethyl oxalate hydrogenation has garnered increasing attention in the fields of syngas utilization.Althoughε-Fe_(2)C has been identified as a promising active species for DMO hydrogenation to ...Ethanol synthesis via dimethyl oxalate hydrogenation has garnered increasing attention in the fields of syngas utilization.Althoughε-Fe_(2)C has been identified as a promising active species for DMO hydrogenation to ethanol,its formation is kinetically challenging during carbonization.In this work,a Fe_(4)N phase was first synthesized by pretreating a 30Fe/SiO_(2)catalyst in an ammonia environment,followed by carbonization in a methanol-H_(2) flow to obtain ε-Fe_(2)C as the active phase.Fe_(4)N,rather than Fe-O-Si,facilitates the transformation into iron carbide during the carbonization process.The transformation pathway of iron nitride(Fe_(x)N)is mediated by intermediate iron carbonyl species(Fe-CO),ultimately leading to the formation of iron carbide as the active phase.The resulting catalyst exhibited 40 times higher catalytic activity than the untreated catalyst in DMO hydrogenation.Combined structure properties and DFT calculation revealed that the lower energy barrier ofε-Fe_(2)C for ester hydrogenation underpins/strengthens its superior performance,while the STY of ε-Fe_(2)C is 2.8 times that ofε'-Fe_(2.2)C and 58 times that ofχ-Fe_(5)C_(2).This study provides a novel strategy for designing highly efficient iron carbide catalysts for the esters hydrogenation system.展开更多
In recent years,(0001)twist grain boundaries(BTGBs)located in primary α grain clusters were identified as fatigue crack nucleation sites in different Ti alloys.In the present study,crack initiation was investigated i...In recent years,(0001)twist grain boundaries(BTGBs)located in primary α grain clusters were identified as fatigue crack nucleation sites in different Ti alloys.In the present study,crack initiation was investigated in a bimodal Ti-5Al-4 V alloy subjected to low-cycle fatigue and dwell-fatigue loadings at room temperature.The low fraction of primary α grains was not associated with a lack of sensitivity to BTGB cracking.Transmission electron microscopy and electron back-scattered diffraction were used to characterize BTGBs in the initial microstructure.The fatigue mechanisms were then analyzed with a focus on dislocation activity.α_(p) grains adjacent to cracked BTGBs contained a high dislocation density.It was primarily composed of planar slip bands of dislocations.In addition,<c+a>dislocations were noticed in the vicinity of cracked BTGBs.They supposedly pertain to crack tip plasticity during growth,and no evidence of a role of an incoming slip event in crack nucleation was obtained.Also,basal slip bands extending across adjacent grains were found to emerge from BTGBs.This feature provides an easier path for crack extension when growth along the grain boundary becomes difficult owing to a deviation from the basal plane.Atom probe tomography analyses evidenced V and Fe segregation at a grain boundary with a significant deviation from the BTGB configuration.This suggests a possible contribution of local solute segregation to the high cracking resistance of general α_(p)/α_(p) grain boundaries.This work provides new insights into the mechanisms involved in cracking of BTGB in Ti alloys subjected to cyclic loadings.展开更多
The deterioration of rock mass in the Three Gorges reservoir area results from the coupled damage effects of macro-micro cracks and dry-wet cycles,and the coupled damage progression can be characterized by energy rele...The deterioration of rock mass in the Three Gorges reservoir area results from the coupled damage effects of macro-micro cracks and dry-wet cycles,and the coupled damage progression can be characterized by energy release rate.In this study,a series of dry-wet cycle uniaxial compression tests was conducted on fractured sandstone,and a method was developed for calculating macro-micro damage(D_(R))and energy release rates(Y_(R))of fractured sandstone subjected to dry-wet cycles by considering energy release rate,dry-wet damage and macro-micro damage.Therewith,the damage mechanisms and complex microcrack propagation patterns of rocks were investigated.Research indicates that sandstone degradation after a limited cycle count primarily exhibits exsolution of internal fillers,progressing to grain skeleton alteration and erosion with increased cycles.Compared with conventional methods,the D_(R) and Y_(R) methodologies exhibit heightened sensitivity to microcrack closure during compaction and abrupt energy release at the point of failure.Based on D_(R) and Y_(R),the failure process of fractured sandstone can be classified into six stages:stress adjustment(I),microcracks equal closure(II),nonlinear slow closure(III),low-speed extension(IV),rapid extension(V),and macroscopic main fracture emergence(VI).The abrupt change in damage energy release rate during stage V may serve as a reliable precursor for inducing failure.The stage-based classification may enhance traditional methods by tracking damage progression and accurately identifying rock failure precursors.The findings are expected to provide a scientific basis for understanding damage mechanisms and enabling early warning of reservoir-bank slope failure.展开更多
To fully exploit the rich characteristic variation laws of an integrated energy system(IES)and further improve the short-term load-forecasting accuracy,a load-forecasting method is proposed for an IES based on LSTM an...To fully exploit the rich characteristic variation laws of an integrated energy system(IES)and further improve the short-term load-forecasting accuracy,a load-forecasting method is proposed for an IES based on LSTM and dynamic similar days with multi-features.Feature expansion was performed to construct a comprehensive load day covering the load and meteorological information with coarse and fine time granularity,far and near time periods.The Gaussian mixture model(GMM)was used to divide the scene of the comprehensive load day,and gray correlation analysis was used to match the scene with the coarse time granularity characteristics of the day to be forecasted.Five typical days with the highest correlation with the day to be predicted in the scene were selected to construct a“dynamic similar day”by weighting.The key features of adjacent days and dynamic similar days were used to forecast multi-loads with fine time granularity using LSTM.Comparing the static features as input and the selection method of similar days based on non-extended single features,the effectiveness of the proposed prediction method was verified.展开更多
With the development of electric helicopters’ motor technology and the widespread use of electric drive rotors, more aircraft use electric rotors to provide thrust and directional control.For a helicopter tail rotor,...With the development of electric helicopters’ motor technology and the widespread use of electric drive rotors, more aircraft use electric rotors to provide thrust and directional control.For a helicopter tail rotor, the wake of the main rotor influences the tail rotor’s inflow and wake.In the procedure of controlling, crosswind will also cause changes to the tail disk load. This paper describes requirements and design principles of an electric motor drive and variable pitch tail rotor system. A particular spoke-type architecture of the motor is designed, and the performance of blades is analyzed by the CFD method. The demand for simplicity of moving parts and strict constraints on the weight of a helicopter makes the design of electrical and mechanical components challenging. Different solutions have been investigated to propose an effective alternative to the mechanical actuation system. A test platform is constructed which can collect the dynamic response of the thrust control. The enhancement of the response speed due to an individual motor speed control and variable-pitch system is validated.展开更多
Considering the complex coupling of multiple energies and the varying load forecasting errors for an integrated energy system(IES),this study proposes a dynamic time-scale scheduling strategy based on long short-term ...Considering the complex coupling of multiple energies and the varying load forecasting errors for an integrated energy system(IES),this study proposes a dynamic time-scale scheduling strategy based on long short-term memory(LSTM)and multiple load forecasting errors.This strategy dynamically selects a hybrid timescale which is suitable for a variety of energies for each month.This is obtained by combining the mean absolute percentage error(MAPE)curve of the load forecasting with the error restriction requirements of the dispatcher.Based on the day-ahead scheduling plan,the output of the partial equipment is selectively adjusted at each time-scale to realize multi-energy collaborative optimization and gives full play to the comprehensive advantages of the IES.This is achieved by considering the differences in the response speed for each piece of equipment within the intra-day scheduling.This study uses the IES as an example,and it dynamically determines the time scale of the energy monthly.In addition,this investigation presents a detailed analysis of the output plan of the key equipment to demonstrate the necessity and the advantages of the strategy.展开更多
Rice(Oryza sativa L.)is a major food crop worldwide.Plant height and yield are important agronomic traits of rice.Several genes regulating plant height and/or yield have been cloned.However,the molecular mechanisms co...Rice(Oryza sativa L.)is a major food crop worldwide.Plant height and yield are important agronomic traits of rice.Several genes regulating plant height and/or yield have been cloned.However,the molecular mechanisms coordinating plant height and yield are not fully characterized.Here,we report a novel gene,OstMAPKKK5 that encodes a truncated variant of a mitogen-activated protein kinase kinase kinase 5(OsMAPKKK5)lacking an intact kinase domain.Transgenic plants overexpressing OstMAPKKK5 in indica cultivar 9311 showed increased plant height,grain length,grain width,1000-grain weight,grain number per main panicle,and yield.Real-time quantitative PCR showed that OstMAPKKK5 was widely expressed in various tissues and developmental stages.The increased plant height and yield were attributed to enlarged cell size.Overexpression of OstMAPKKK5 led to higher contents of various forms of endogenous gibberellin(GA),especially the most common active forms,GA1,GA3,GA4.We concluded that OstMAPKKK5 positively regulates plant height and yield in rice by affecting cell size,and that its underlying mechanism is based on increased endogenous GA content.展开更多
Aiming at overcoming the strength-ductility trade-off in structural Ti-alloys,a new family of TRIP/TWIP Ti-alloys was developed in the past decade(TWIP:twinning-induced plasticity;TRIP:transformationinduced plasticity...Aiming at overcoming the strength-ductility trade-off in structural Ti-alloys,a new family of TRIP/TWIP Ti-alloys was developed in the past decade(TWIP:twinning-induced plasticity;TRIP:transformationinduced plasticity).Herein,we study the tunable nature of deformation mechanisms with various TWIP and TRIP contributions by fine adjustment of the Zr content on ternary Ti-12 Mo-xZr(x=3,6,10)alloys.The microstructure and deformation mechanisms of the Ti-Mo-Zr alloys are explored by using in-situ electron backscatter diffraction(EBSD)and transmission electron microscopy(TEM).The results show that a transition of the dominant deformation mode occurred,going from TRIP to TWIP major mechanism with increasing Zr content.In the Ti-12 Mo-3 Zr alloy,the stress-induced martensitic transformation(SIM)is the major deformation mode which accommodates the plastic flow.Regarding the Ti-12 Mo-6 Zr alloy,the combined deformation twinning(DT)and SIM modes both contribute to the overall plasticity with enhanced strain-hardening rate and subsequent large uniform ductility.Further increase of the Zr content in Ti-12 Mo-10 Zr alloy leads to an improved yield stress involving single DT mode as a dominant deformation mechanism throughout the plastic regime.In the present work,a set of comprehensive in-situ and ex-situ microstructural investigations clarify the evolution of deformation microstructures during tensile loading and unloading processes.展开更多
1.Introduction In structural metallic materials,the occurrence of particular deformation mechanisms such as dislocation slip,deformation twins(DTs)[1,2]deformation kink bands(KBs)[3,4]or stressinduced phase transforma...1.Introduction In structural metallic materials,the occurrence of particular deformation mechanisms such as dislocation slip,deformation twins(DTs)[1,2]deformation kink bands(KBs)[3,4]or stressinduced phase transformations(SIM)[5],are closely related to both their crystal structures[6–8](e.g.FCC,BCC and HCP)and loading conditions(e.g.temperature and/or strain rate).展开更多
Mg-air batteries have attracted tremendous attention as a potential next-generation power source for portable electronics and e-transportation due to their remarkable high theoretical volumetric energy density,environ...Mg-air batteries have attracted tremendous attention as a potential next-generation power source for portable electronics and e-transportation due to their remarkable high theoretical volumetric energy density,environmental sustainability,and cost-effectiveness.However,the fast hydrogen evolution reaction(HER)in NaCl-based aqueous electrolytes impairs the performance of Mg-air batteries and leads to poor specific capacity,low energy density,and low utilization.Thus,the conventionally used NaCl solute was proposed to be replaced by NaNO_(3)and acetic acid additive as a corrosion inhibitor,therefore an electrolyte engineering for long-life time Mg-air batteries is reported.The resulting Mg-air batteries based on this optimized electrolyte demonstrate an improved discharge voltage reaching~1.8 V for initial 5 h at a current density of 0.5 mA/cm^(2) and significantly prolonged cells'operational lifetime to over 360 h,in contrast to only~17 h observed in NaCl electrolyte.X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry were employed to analyse the composition of surface film and scanning electron microscopy combined with transmission electron microscopy to clarify the morphology changes of the surface layer as a function of acetic acid addition.The thorough studies of chemical composition and morphology of corrosion products have allowed us to elucidate the working mechanism of Mg anode in this optimized electrolyte for Mg-air batteries.展开更多
The structure of the primary olfactory brain center was studied in male and female adult Ambrostoma quadriimpressum by means of a series of histological sections labeled using the reduced-silver-stain technique.The an...The structure of the primary olfactory brain center was studied in male and female adult Ambrostoma quadriimpressum by means of a series of histological sections labeled using the reduced-silver-stain technique.The antennal lobe was elliptical,and the total number of glomeruli was approximately 50 in the antennal lobe in both sexes.There was no sexual dimorphism with respect to the size of the antennal lobe or the number and shape of glomeruli.展开更多
In the arid region of northwestern China(ARNC),water resources are the most critical factor restricting socioeconomic development and influencing the stability of the area’s ecological systems.The region’s complex w...In the arid region of northwestern China(ARNC),water resources are the most critical factor restricting socioeconomic development and influencing the stability of the area’s ecological systems.The region’s complex water system and unique hydrological cycle show distinctive characteristics.Moreover,the intensified hydrological cycle and extreme climatic and hydrological events resulting from global warming have led to increased uncertainty around water resources as well as heightened conflict between water supply and water demand.All of these factors are exerting growing pressures on the socioeconomic development and vulnerable ecological environment in the region.This research evaluates the impacts of climate change on water resources,hydrological processes,agricultural system,and desert ecosystems in the ARNC,and addresses some associated risks and challenges specific to this area.The temperature is rising at a rate of 0.31C per decade during 1961–2017 and hydrological processes are being significantly influenced by changes in glaciers,snow cover,and precipitation form,especially in the rivers recharged primarily by melt water.Ecosystems are also largely influenced by climate change,with the Normalized Difference Vegetation Index(NDVI)of natural vegetation exhibited an increasing trend prior to 1998,and then reversed in Xinjiang while the Hexi Corridor of Gansu showed the opposite trends.Furthermore,the desert-oasis transition zone showed a reduction in area due to the warming trend and the recent rapid expansion of irrigated area.Both the warming and intensified drought are threatening agriculture security.The present study could shed light on sustainable development in this region under climate change and provides scientific basis to the construction of the“Silk Road Economic Belt”.展开更多
This paper reviewed advances in researches on genetic diversity of Lepidoptera insects from chromosome polymorphism,protein polymorphism,and DNA polymorphism,and stated that DNA sequence variation will become main poi...This paper reviewed advances in researches on genetic diversity of Lepidoptera insects from chromosome polymorphism,protein polymorphism,and DNA polymorphism,and stated that DNA sequence variation will become main points of researches about genetic diversity.展开更多
This study proposes a novel strategy for the design of a new family of metastable Zr alloys.These al-loys offer improved mechanical properties for implants,particularly in applications where conventional stainless ste...This study proposes a novel strategy for the design of a new family of metastable Zr alloys.These al-loys offer improved mechanical properties for implants,particularly in applications where conventional stainless steels and Co-Cr alloys are currently used but lack suitability.The design approach is based on the controlled twinning-induced plasticity(TWIP)effect,significantly enhancing the ductility and strain-hardenability of the Zr alloys.In order to draw a“blueprint”for the compositional design of biomedical T WIP(Bio-T WIP)Zr alloys-using only non-toxic elements,the study combines D-electron phase stability calculations(specifically bond order(Bo)and mean d-orbital energy(Md))with a systematic experimental screening of active deformation mechanisms within the Zr-Nb-Sn alloy system.This research aids in ac-curately identifying the TWIP line,which signifies the mechanism shift between TWIP and classic slip as the primary deformation mechanism.To demonstrate the efficacy of the TWIP mechanism in enhancing mechanical properties,Zr-12Nb-2Sn,Zr-13Nb-1Sn,and Zr-14Nb-3Sn alloys are selected.Results indicate that the TWIP mechanism leads to a significant improvement of strain-hardening rate and a uniform elongation of∼20%in Zr-12Nb-2Sn,which displays both{332}<113>mechanical twinning and disloca-tion slip as the primary deformation mechanisms.Conversely,Zr-14Nb-3Sn exhibits the typical mechan-ical properties found in stable body-centered cubic(BCC)alloys,characterized by the sole occurrence of dislocation slip.Cell viability tests confirm the superior biocompatibility of Zr-Nb-based alloys with deformation twins on the surface,in line with existing literature.Based on the whole set of results,a comprehensive design diagram is proposed.展开更多
Frontal upwelling is an important phenomenon in summer in the Yellow Sea(YS)and plays an essential role in the distribution of nutrients and biological species.In this paper,a three-dimensional hydrodynamic model is a...Frontal upwelling is an important phenomenon in summer in the Yellow Sea(YS)and plays an essential role in the distribution of nutrients and biological species.In this paper,a three-dimensional hydrodynamic model is applied to investigate the characteristics and influencing factors of frontal upwelling in the YS.The results show that the strength and distribution of frontal upwelling are largely dependent on the topography and bottom temperature fronts.The frontal upwelling in the YS is stronger and narrower near the eastern coast than near the western coast due to the steeper shelf slope.Moreover,external forcings,such as the meridional wind speed and air temperature in summer and the air temperature in the preceding winter and spring,have certain influences on the strength of frontal upwelling.An increase in air temperature in the previous winter and spring weakens the frontal upwelling in summer;in contrast,an increase in air temperature in summer strengthens the frontal upwelling.When the southerly wind in summer increases,the upwelling intensifies in the western YS and weakens in the eastern YS.The air temperature influences the strength of upwelling by changing the baroclinicity in the frontal region.Furthermore,the meridional wind speed in summer affects frontal upwelling via Ekman pumping.展开更多
基金financially supported by the Biological BreedingNational Science and Technology Major Project(2023ZD0405806)the National Key R&D Program for the 14th Five-Year Plan in China(2022YFD2200304).
文摘The level of genetic variation within a breeding population affects the effectiveness of selection strategies for genetic improvement.The relationship between genetic variation level within Pinus tabuliformis breeding populations and selection strategies or selection effectiveness is not fully investigated.Here,we compared the selection effectiveness of combined and individual direct selection strategies using half-and full-sib families produced from advanced-generation P.tabuliformis seed orchard as our test populations.Our results revealed that,within half-sib families,average diameter at breast height(DBH),tree height,and volume growth of superior individuals selected by the direct selection strategy were higher by 7.72%,18.56%,and 31.01%,respectively,than those selected by the combined selection strategy.Furthermore,significant differences(P<0.01)were observed between the two strategies in terms of the expected genetic gains for average tree height and volume.In contrast,within full-sib families,the differences in tree average DBH,height,and volume between the two selection strategies were relatively minor with increase of 0.17%,2.73%,and 2.21%,respectively,and no significant differences were found in the average expected genetic gains for the studied traits.Half-sib families exhibited greater phenotypic and genetic variation,resulting in improved selection efficiency with the direct selection strategy but also introduced a level of inbreeding risk.Based on genetic distance estimates using molecular markers,our comparative seed orchard design analysis showed that the Improved Adaptive Genetic Programming Algorithm(IAPGA)reduced the average inbreeding coefficient by 14.36% and 14.73% compared to sequential and random designs,respectively.In conclusion,the combination of the direct selection strategy with IAPGA seed orchard design aimed at minimizing inbreeding offered an efficient approach for establishing advanced-generation P.tabuliformis seed orchards.
基金supported by the National Natural Science Foundation of China(21878227,22278309)。
文摘Ethanol synthesis via dimethyl oxalate hydrogenation has garnered increasing attention in the fields of syngas utilization.Althoughε-Fe_(2)C has been identified as a promising active species for DMO hydrogenation to ethanol,its formation is kinetically challenging during carbonization.In this work,a Fe_(4)N phase was first synthesized by pretreating a 30Fe/SiO_(2)catalyst in an ammonia environment,followed by carbonization in a methanol-H_(2) flow to obtain ε-Fe_(2)C as the active phase.Fe_(4)N,rather than Fe-O-Si,facilitates the transformation into iron carbide during the carbonization process.The transformation pathway of iron nitride(Fe_(x)N)is mediated by intermediate iron carbonyl species(Fe-CO),ultimately leading to the formation of iron carbide as the active phase.The resulting catalyst exhibited 40 times higher catalytic activity than the untreated catalyst in DMO hydrogenation.Combined structure properties and DFT calculation revealed that the lower energy barrier ofε-Fe_(2)C for ester hydrogenation underpins/strengthens its superior performance,while the STY of ε-Fe_(2)C is 2.8 times that ofε'-Fe_(2.2)C and 58 times that ofχ-Fe_(5)C_(2).This study provides a novel strategy for designing highly efficient iron carbide catalysts for the esters hydrogenation system.
基金financially supported by the National Natural Science Foundation of China(No.U21A2050)support of the Chinese Scholarship Council(No.202006290165).
文摘In recent years,(0001)twist grain boundaries(BTGBs)located in primary α grain clusters were identified as fatigue crack nucleation sites in different Ti alloys.In the present study,crack initiation was investigated in a bimodal Ti-5Al-4 V alloy subjected to low-cycle fatigue and dwell-fatigue loadings at room temperature.The low fraction of primary α grains was not associated with a lack of sensitivity to BTGB cracking.Transmission electron microscopy and electron back-scattered diffraction were used to characterize BTGBs in the initial microstructure.The fatigue mechanisms were then analyzed with a focus on dislocation activity.α_(p) grains adjacent to cracked BTGBs contained a high dislocation density.It was primarily composed of planar slip bands of dislocations.In addition,<c+a>dislocations were noticed in the vicinity of cracked BTGBs.They supposedly pertain to crack tip plasticity during growth,and no evidence of a role of an incoming slip event in crack nucleation was obtained.Also,basal slip bands extending across adjacent grains were found to emerge from BTGBs.This feature provides an easier path for crack extension when growth along the grain boundary becomes difficult owing to a deviation from the basal plane.Atom probe tomography analyses evidenced V and Fe segregation at a grain boundary with a significant deviation from the BTGB configuration.This suggests a possible contribution of local solute segregation to the high cracking resistance of general α_(p)/α_(p) grain boundaries.This work provides new insights into the mechanisms involved in cracking of BTGB in Ti alloys subjected to cyclic loadings.
基金supported by the National Natural Science Foundation of China(Grant No.51978106)China Postdoctoral Science Foundation(Grant No.2022MD723831)Graduate Research and Innovation Foundation of Chongqing(Grant No.CYB240039).
文摘The deterioration of rock mass in the Three Gorges reservoir area results from the coupled damage effects of macro-micro cracks and dry-wet cycles,and the coupled damage progression can be characterized by energy release rate.In this study,a series of dry-wet cycle uniaxial compression tests was conducted on fractured sandstone,and a method was developed for calculating macro-micro damage(D_(R))and energy release rates(Y_(R))of fractured sandstone subjected to dry-wet cycles by considering energy release rate,dry-wet damage and macro-micro damage.Therewith,the damage mechanisms and complex microcrack propagation patterns of rocks were investigated.Research indicates that sandstone degradation after a limited cycle count primarily exhibits exsolution of internal fillers,progressing to grain skeleton alteration and erosion with increased cycles.Compared with conventional methods,the D_(R) and Y_(R) methodologies exhibit heightened sensitivity to microcrack closure during compaction and abrupt energy release at the point of failure.Based on D_(R) and Y_(R),the failure process of fractured sandstone can be classified into six stages:stress adjustment(I),microcracks equal closure(II),nonlinear slow closure(III),low-speed extension(IV),rapid extension(V),and macroscopic main fracture emergence(VI).The abrupt change in damage energy release rate during stage V may serve as a reliable precursor for inducing failure.The stage-based classification may enhance traditional methods by tracking damage progression and accurately identifying rock failure precursors.The findings are expected to provide a scientific basis for understanding damage mechanisms and enabling early warning of reservoir-bank slope failure.
基金supported by National Natural Science Foundation of China(NSFC)(62103126).
文摘To fully exploit the rich characteristic variation laws of an integrated energy system(IES)and further improve the short-term load-forecasting accuracy,a load-forecasting method is proposed for an IES based on LSTM and dynamic similar days with multi-features.Feature expansion was performed to construct a comprehensive load day covering the load and meteorological information with coarse and fine time granularity,far and near time periods.The Gaussian mixture model(GMM)was used to divide the scene of the comprehensive load day,and gray correlation analysis was used to match the scene with the coarse time granularity characteristics of the day to be forecasted.Five typical days with the highest correlation with the day to be predicted in the scene were selected to construct a“dynamic similar day”by weighting.The key features of adjacent days and dynamic similar days were used to forecast multi-loads with fine time granularity using LSTM.Comparing the static features as input and the selection method of similar days based on non-extended single features,the effectiveness of the proposed prediction method was verified.
文摘With the development of electric helicopters’ motor technology and the widespread use of electric drive rotors, more aircraft use electric rotors to provide thrust and directional control.For a helicopter tail rotor, the wake of the main rotor influences the tail rotor’s inflow and wake.In the procedure of controlling, crosswind will also cause changes to the tail disk load. This paper describes requirements and design principles of an electric motor drive and variable pitch tail rotor system. A particular spoke-type architecture of the motor is designed, and the performance of blades is analyzed by the CFD method. The demand for simplicity of moving parts and strict constraints on the weight of a helicopter makes the design of electrical and mechanical components challenging. Different solutions have been investigated to propose an effective alternative to the mechanical actuation system. A test platform is constructed which can collect the dynamic response of the thrust control. The enhancement of the response speed due to an individual motor speed control and variable-pitch system is validated.
基金supported by the Fundamental Research Funds for the Central Universities(No.2017MS093)
文摘Considering the complex coupling of multiple energies and the varying load forecasting errors for an integrated energy system(IES),this study proposes a dynamic time-scale scheduling strategy based on long short-term memory(LSTM)and multiple load forecasting errors.This strategy dynamically selects a hybrid timescale which is suitable for a variety of energies for each month.This is obtained by combining the mean absolute percentage error(MAPE)curve of the load forecasting with the error restriction requirements of the dispatcher.Based on the day-ahead scheduling plan,the output of the partial equipment is selectively adjusted at each time-scale to realize multi-energy collaborative optimization and gives full play to the comprehensive advantages of the IES.This is achieved by considering the differences in the response speed for each piece of equipment within the intra-day scheduling.This study uses the IES as an example,and it dynamically determines the time scale of the energy monthly.In addition,this investigation presents a detailed analysis of the output plan of the key equipment to demonstrate the necessity and the advantages of the strategy.
基金supported by the National Natural Science Foundation of China (31471461, 31671655)the National Transgenic Major Project of China (2016ZX08001004-001)Shanghai Agriculture Applied Technology Development Program, China (G2014070102)
文摘Rice(Oryza sativa L.)is a major food crop worldwide.Plant height and yield are important agronomic traits of rice.Several genes regulating plant height and/or yield have been cloned.However,the molecular mechanisms coordinating plant height and yield are not fully characterized.Here,we report a novel gene,OstMAPKKK5 that encodes a truncated variant of a mitogen-activated protein kinase kinase kinase 5(OsMAPKKK5)lacking an intact kinase domain.Transgenic plants overexpressing OstMAPKKK5 in indica cultivar 9311 showed increased plant height,grain length,grain width,1000-grain weight,grain number per main panicle,and yield.Real-time quantitative PCR showed that OstMAPKKK5 was widely expressed in various tissues and developmental stages.The increased plant height and yield were attributed to enlarged cell size.Overexpression of OstMAPKKK5 led to higher contents of various forms of endogenous gibberellin(GA),especially the most common active forms,GA1,GA3,GA4.We concluded that OstMAPKKK5 positively regulates plant height and yield in rice by affecting cell size,and that its underlying mechanism is based on increased endogenous GA content.
基金supported by National Natural Science foundation of China(Grant No.51601216 and 51901193)China Postdoctoral Science Foundation(Grant No.2018M632414)+4 种基金Fund of State Key Lab of Advanced Metals and Materials,University of Science and Technology Beijing(Grant No.2019-ZD03)Fundamental Research Funds for the Central Universities(Grant No.2017XKQY009)Funds of Industry-University-Research Cooperation in Jiangsu Province(Grand No.BY2018075)Key Research and Development Program of Shaanxi(Grant No.2019GY-151)sponsored by China Scholarship Council。
文摘Aiming at overcoming the strength-ductility trade-off in structural Ti-alloys,a new family of TRIP/TWIP Ti-alloys was developed in the past decade(TWIP:twinning-induced plasticity;TRIP:transformationinduced plasticity).Herein,we study the tunable nature of deformation mechanisms with various TWIP and TRIP contributions by fine adjustment of the Zr content on ternary Ti-12 Mo-xZr(x=3,6,10)alloys.The microstructure and deformation mechanisms of the Ti-Mo-Zr alloys are explored by using in-situ electron backscatter diffraction(EBSD)and transmission electron microscopy(TEM).The results show that a transition of the dominant deformation mode occurred,going from TRIP to TWIP major mechanism with increasing Zr content.In the Ti-12 Mo-3 Zr alloy,the stress-induced martensitic transformation(SIM)is the major deformation mode which accommodates the plastic flow.Regarding the Ti-12 Mo-6 Zr alloy,the combined deformation twinning(DT)and SIM modes both contribute to the overall plasticity with enhanced strain-hardening rate and subsequent large uniform ductility.Further increase of the Zr content in Ti-12 Mo-10 Zr alloy leads to an improved yield stress involving single DT mode as a dominant deformation mechanism throughout the plastic regime.In the present work,a set of comprehensive in-situ and ex-situ microstructural investigations clarify the evolution of deformation microstructures during tensile loading and unloading processes.
基金the State Key Laboratory of Solidification Processing in NWPU(No.SKLSP201818)the National Natural Science Foundation of China(No.51601216)the Fundamental Research Funds for the Central Universities(No.2018GF13)。
文摘1.Introduction In structural metallic materials,the occurrence of particular deformation mechanisms such as dislocation slip,deformation twins(DTs)[1,2]deformation kink bands(KBs)[3,4]or stressinduced phase transformations(SIM)[5],are closely related to both their crystal structures[6–8](e.g.FCC,BCC and HCP)and loading conditions(e.g.temperature and/or strain rate).
基金the China Scholarship Council(CSC)for funding(no.201806310116)。
文摘Mg-air batteries have attracted tremendous attention as a potential next-generation power source for portable electronics and e-transportation due to their remarkable high theoretical volumetric energy density,environmental sustainability,and cost-effectiveness.However,the fast hydrogen evolution reaction(HER)in NaCl-based aqueous electrolytes impairs the performance of Mg-air batteries and leads to poor specific capacity,low energy density,and low utilization.Thus,the conventionally used NaCl solute was proposed to be replaced by NaNO_(3)and acetic acid additive as a corrosion inhibitor,therefore an electrolyte engineering for long-life time Mg-air batteries is reported.The resulting Mg-air batteries based on this optimized electrolyte demonstrate an improved discharge voltage reaching~1.8 V for initial 5 h at a current density of 0.5 mA/cm^(2) and significantly prolonged cells'operational lifetime to over 360 h,in contrast to only~17 h observed in NaCl electrolyte.X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry were employed to analyse the composition of surface film and scanning electron microscopy combined with transmission electron microscopy to clarify the morphology changes of the surface layer as a function of acetic acid addition.The thorough studies of chemical composition and morphology of corrosion products have allowed us to elucidate the working mechanism of Mg anode in this optimized electrolyte for Mg-air batteries.
基金This research was supported by the Natural Science Foundation of China Heilongjiang(C2017059).
文摘The structure of the primary olfactory brain center was studied in male and female adult Ambrostoma quadriimpressum by means of a series of histological sections labeled using the reduced-silver-stain technique.The antennal lobe was elliptical,and the total number of glomeruli was approximately 50 in the antennal lobe in both sexes.There was no sexual dimorphism with respect to the size of the antennal lobe or the number and shape of glomeruli.
基金supported by the National Key Research and Development Program(2019YFA0606902)the National Natural Science Foundation of China(U1903208)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(2019431).
文摘In the arid region of northwestern China(ARNC),water resources are the most critical factor restricting socioeconomic development and influencing the stability of the area’s ecological systems.The region’s complex water system and unique hydrological cycle show distinctive characteristics.Moreover,the intensified hydrological cycle and extreme climatic and hydrological events resulting from global warming have led to increased uncertainty around water resources as well as heightened conflict between water supply and water demand.All of these factors are exerting growing pressures on the socioeconomic development and vulnerable ecological environment in the region.This research evaluates the impacts of climate change on water resources,hydrological processes,agricultural system,and desert ecosystems in the ARNC,and addresses some associated risks and challenges specific to this area.The temperature is rising at a rate of 0.31C per decade during 1961–2017 and hydrological processes are being significantly influenced by changes in glaciers,snow cover,and precipitation form,especially in the rivers recharged primarily by melt water.Ecosystems are also largely influenced by climate change,with the Normalized Difference Vegetation Index(NDVI)of natural vegetation exhibited an increasing trend prior to 1998,and then reversed in Xinjiang while the Hexi Corridor of Gansu showed the opposite trends.Furthermore,the desert-oasis transition zone showed a reduction in area due to the warming trend and the recent rapid expansion of irrigated area.Both the warming and intensified drought are threatening agriculture security.The present study could shed light on sustainable development in this region under climate change and provides scientific basis to the construction of the“Silk Road Economic Belt”.
基金Supported by Special Fund Project for Talent Development of Anhui Academy of Agricultural Sciences(17F0610)Discipline Construction Project of Anhui Academy of Agricultural Sciences(16A0618)Project of Hefei Comprehensive Experiment Station of China Sericulture Industry Technology System(CARS-22-SYZ09)
文摘This paper reviewed advances in researches on genetic diversity of Lepidoptera insects from chromosome polymorphism,protein polymorphism,and DNA polymorphism,and stated that DNA sequence variation will become main points of researches about genetic diversity.
基金the support of the French Agence Nationale de la Recherche(ANR),under grant ANR-21-CE08-0022(project ISANAMI)Junhui TANG is sponsored by the China Scholarship Council.
文摘This study proposes a novel strategy for the design of a new family of metastable Zr alloys.These al-loys offer improved mechanical properties for implants,particularly in applications where conventional stainless steels and Co-Cr alloys are currently used but lack suitability.The design approach is based on the controlled twinning-induced plasticity(TWIP)effect,significantly enhancing the ductility and strain-hardenability of the Zr alloys.In order to draw a“blueprint”for the compositional design of biomedical T WIP(Bio-T WIP)Zr alloys-using only non-toxic elements,the study combines D-electron phase stability calculations(specifically bond order(Bo)and mean d-orbital energy(Md))with a systematic experimental screening of active deformation mechanisms within the Zr-Nb-Sn alloy system.This research aids in ac-curately identifying the TWIP line,which signifies the mechanism shift between TWIP and classic slip as the primary deformation mechanism.To demonstrate the efficacy of the TWIP mechanism in enhancing mechanical properties,Zr-12Nb-2Sn,Zr-13Nb-1Sn,and Zr-14Nb-3Sn alloys are selected.Results indicate that the TWIP mechanism leads to a significant improvement of strain-hardening rate and a uniform elongation of∼20%in Zr-12Nb-2Sn,which displays both{332}<113>mechanical twinning and disloca-tion slip as the primary deformation mechanisms.Conversely,Zr-14Nb-3Sn exhibits the typical mechan-ical properties found in stable body-centered cubic(BCC)alloys,characterized by the sole occurrence of dislocation slip.Cell viability tests confirm the superior biocompatibility of Zr-Nb-based alloys with deformation twins on the surface,in line with existing literature.Based on the whole set of results,a comprehensive design diagram is proposed.
基金The National Key Research and Development Project under contract No.2017YFC1403400the National Key Research and Development Program of China under contract No.2016YFC1402501+2 种基金the National Natural Science Foundation of China under contract No.41806164the Open Fund Project of Key Laboratory of Marine Environmental Information Technology,Ministry of Natural Resourcesthe Shandong Joint Fund for Marine Science Research Centers under contract No.U1406401.
文摘Frontal upwelling is an important phenomenon in summer in the Yellow Sea(YS)and plays an essential role in the distribution of nutrients and biological species.In this paper,a three-dimensional hydrodynamic model is applied to investigate the characteristics and influencing factors of frontal upwelling in the YS.The results show that the strength and distribution of frontal upwelling are largely dependent on the topography and bottom temperature fronts.The frontal upwelling in the YS is stronger and narrower near the eastern coast than near the western coast due to the steeper shelf slope.Moreover,external forcings,such as the meridional wind speed and air temperature in summer and the air temperature in the preceding winter and spring,have certain influences on the strength of frontal upwelling.An increase in air temperature in the previous winter and spring weakens the frontal upwelling in summer;in contrast,an increase in air temperature in summer strengthens the frontal upwelling.When the southerly wind in summer increases,the upwelling intensifies in the western YS and weakens in the eastern YS.The air temperature influences the strength of upwelling by changing the baroclinicity in the frontal region.Furthermore,the meridional wind speed in summer affects frontal upwelling via Ekman pumping.
