Latent information is difficult to get from the text in speech synthesis.Studies show that features from speech can get more information to help text encoding.In the field of speech encoding,a lot of work has been con...Latent information is difficult to get from the text in speech synthesis.Studies show that features from speech can get more information to help text encoding.In the field of speech encoding,a lot of work has been conducted on two aspects.The first aspect is to encode speech frame by frame.The second aspect is to encode the whole speech to a vector.But the scale in these aspects is fixed.So,encoding speech with an adjustable scale for more latent information is worthy of investigation.But current alignment approaches only support frame-by-frame encoding and speech-to-vector encoding.It remains a challenge to propose a new alignment approach to support adjustable scale speech encoding.This paper presents the dynamic speech encoder with a new alignment approach in conjunction with frame-by-frame encoding and speech-to-vector encoding.The speech feature fromourmodel achieves three functions.First,the speech feature can reconstruct the origin speech while the length of the speech feature is equal to the text length.Second,our model can get text embedding fromspeech,and the encoded speech feature is similar to the text embedding result.Finally,it can transfer the style of synthesis speech and make it more similar to the given reference speech.展开更多
Online advertising has gained much attention on various platforms as a hugely lucrative market.In promoting content and advertisements in real life,the acquisition of user target actions is usually a multi-step proces...Online advertising has gained much attention on various platforms as a hugely lucrative market.In promoting content and advertisements in real life,the acquisition of user target actions is usually a multi-step process,such as impres-sion→click→conversion,which means the process from the delivery of the recommended item to the user’s click to the final conversion.Due to data sparsity or sample selection bias,it is difficult for the trained model to achieve the business goal of the target campaign.Multi-task learning,a classical solution to this pro-blem,aims to generalize better on the original task given several related tasks by exploiting the knowledge between tasks to share the same feature and label space.Adaptively learned task relations bring better performance to make full use of the correlation between tasks.We train a general model capable of captur-ing the relationships between various tasks on all existing active tasks from a meta-learning perspective.In addition,this paper proposes a Multi-task Attention Network(MAN)to identify commonalities and differences between tasks in the feature space.The model performance is improved by explicitly learning the stacking of task relationships in the label space.To illustrate the effectiveness of our method,experiments are conducted on Alibaba Click and Conversion Pre-diction(Ali-CCP)dataset.Experimental results show that the method outperforms the state-of-the-art multi-task learning methods.展开更多
Biological soil crusts （BSCs） are capable of modifying nutrient availability to favor the establishment of biogeochemical cycles. Microbial activities serve as critical roles for both carbon and nutrient transformat...Biological soil crusts （BSCs） are capable of modifying nutrient availability to favor the establishment of biogeochemical cycles. Microbial activities serve as critical roles for both carbon and nutrient transformation in BSCs. However, little is known about microbial activities and physical-chemical properties of BSCs in the Gurbantunggut Desert, Xinjiang, China. In the present research, a sampling line with 1-m wide and 20-m long was set up in each of five typical interdune areas selected randomly in the Gurbantunggut Desert. Within each sampling line, samples of bare sand sheet, algal crusts, lichen crusts and moss crusts were randomly collected at the depth of 0-2 cm. Varia- tions of microalgal biomass, microbial biomass, enzyme activities and soil physical-chemical properties in different succession of BSCs were analyzed. The relationships between microalgal biomass, microbial biomass, enzymatic activities and soil physical-chemical properties were explored by stepwise regression. Our results indicate that micro- algal biomass, microbial biomass and most of enzyme activities increased as the BSCs developed and their highest values occurred in lichen or moss crusts. Except for total K, the contents of most soil nutrients （organic C, total N, total P, available N, available P and available K） were the lowest in the bare sand sheet and significantly increased with the BSCs development, reaching their highest values in moss crusts. However, pH values significantly decreased as the BSCs developed. Significant and positive correlations were observed between chlorophyll a and microbial biomass C. Total P and N were positively associated with chlorophyll a and microbial biomass C, whereas there was a significant and negative correlation between microbial biomass and available P. The growth of cyanobacteria and microorganism contributed C and N in the soil, which offered substrates for enzyme activities thus increasing enzyme activities. Probably, improvement in enzyme activities increased soil fertility and promoted the growth of cyanobacteria, eukary- otic algae and heterotrophic microorganism, with the accelerating succession of BSCs. The present research found that microalgal-microbial biomass and enzyme activities played important roles on the contents of nutrients in the successional stages of BSCs and helped us to understand developmental mechanism in the succession of BSCs.展开更多
The high temperature creep behavior of carbon nanotube(CNT)/alumina was mediated by the surface chemical functionalization used for synthesis of composite powders. Non-covalent functionalized carbon nanotubes make com...The high temperature creep behavior of carbon nanotube(CNT)/alumina was mediated by the surface chemical functionalization used for synthesis of composite powders. Non-covalent functionalized carbon nanotubes make composites ductile, but covalent approach leads composites that are creep-resistant. Oxygen vacancy mechanism is proposed to account for this mediation effect in this communication.展开更多
A novel class of high-entropy rare-earth metal diborodicarbide(Y_(0.2)5 Yb_(0.25)Dy_(0.25)Er_(0.25))B_(2)C_(2)(HE-REB_(2)C_(2))ceramics was successfully fabricated using the in-situ reactive spark plasma sintering(SPS...A novel class of high-entropy rare-earth metal diborodicarbide(Y_(0.2)5 Yb_(0.25)Dy_(0.25)Er_(0.25))B_(2)C_(2)(HE-REB_(2)C_(2))ceramics was successfully fabricated using the in-situ reactive spark plasma sintering(SPS)technology for the first time.Single solid solution with a typical tetragonal structure was formed,having a homogeneous distribution of four rare-earth elements,such as Y,Yb,Dy,and Er.Coefficients of thermal expansion(CTEs)along the a and c directions(aa and ac)were determined to be 4.18 and 16.06μK^(-1),respectively.Thermal expansion anisotropy of the as-obtained HE-REB_(2)C_(2)was attributed to anisotropy of the crystal structure of HE-REB_(2)C_(2).The thermal conductivity(k)of HE-REB_(2)C_(2)was 9.2±0.09 W·m^(-1)·K^(-1),which was lower than that of YB_(2)C_(2)(19.2±0.07 W·m^(-1)·K^(-1)),DyB_(2)C_(2)(11.90.06 W·m^(-1)·K^(-1)),and ErB_(2)C_(2)(12.10.03 W·m^(-1)·K^(-1)),due to high-entropy effect and sluggish diffusion effect of high-entropy ceramics(HECs).Furthermore,Vickers hardness of HE-REB_(2)C_(2)was slightly higher than that of REB_(2)C_(2)owing to the solid solution hardening mechanism of HECs.Typical nano-laminated fracture morphologies,such as kink boundaries,delamination,and slipping were observed at the tip of Vickers indents,suggesting ductile behavior of HE-REB_(2)C_(2).This newly investigated class of ductile HE-REB_(2)C_(2)ceramics expanded the family of HECs to diboridcarbide compounds,which can lead to more research works on high-entropy rare-earth diboridcarbides in the near future.展开更多
High strength SiC whisker-reinforced Ti3SiC2 composites(SiCw/Ti3SiC2)with an improved thermal conductivity and mechanical properties were fabricated by spark plasma sintering.The bending strength of 10 wt%SiCw/Ti3SiC2...High strength SiC whisker-reinforced Ti3SiC2 composites(SiCw/Ti3SiC2)with an improved thermal conductivity and mechanical properties were fabricated by spark plasma sintering.The bending strength of 10 wt%SiCw/Ti3SiC2 was 635 MPa,which was approximately 50%higher than that of the monolithic Ti3SiC2(428 MPa).The Vickers hardness and thermal conductivity(k)also increased by 36%and 25%,respectively,from the monolithic Ti3SiC2 by the incorporation of 10 wt%SiCw.This remarkable improvement both in mechanical and thermal properties was attributed to the fine-grained uniform composite microstructure along with the effects of incorporated SiCw.The SiCw/Ti3SiC2 can be a feasible candidate for the in-core structural application in nuclear reactors due to the excellent mechanical and thermal properties.展开更多
The SiC/Al4SiC4 composites with the improved mechanical properties and thermal conductivity were fabricated by the in-situ reaction of polycarbosilane(PCS)and Al powders using spark plasma sintering.The addition of 5 ...The SiC/Al4SiC4 composites with the improved mechanical properties and thermal conductivity were fabricated by the in-situ reaction of polycarbosilane(PCS)and Al powders using spark plasma sintering.The addition of 5 wt%yttrium(Y)sintering additive was useful to obtain fully dense samples after sintering at a relatively low temperature of 1650℃,due to the formation of a liquid phase during sintering.The average particle size of the in-situ formed SiC was^300 nm.The fracture toughness(4.9 MPa·m1/2),Vickers hardness(16.3 GPa),and thermal conductivity(15.8 W/(m·K))of the SiC/Al4SiC4 composite sintered at 1650℃were significantly higher than the hardness(13.2 GPa),fracture toughness(2.16 MPa·m1/2),and thermal conductivity(7.8 W/(m·K))of the monolithic Al4SiC4 ceramics.The improved mechanical and thermal properties of the composites were attributed to the high density,fine grain size,as well as the optimized grain boundary structure of the SiC/Al4SiC4 composites.展开更多
A nano-laminated Y_(3)Si_(2)C_(2) ceramic material was successfully synthesized via an in situ reaction between YH_(2)and SiC using spark plasma sintering technology.A MAX phase-like ternary layered structure of Y_(3)...A nano-laminated Y_(3)Si_(2)C_(2) ceramic material was successfully synthesized via an in situ reaction between YH_(2)and SiC using spark plasma sintering technology.A MAX phase-like ternary layered structure of Y_(3)Si_(2)C_(2) was observed at the atomic-scale by high resolution transmission electron microscopy.The lattice parameters calculated from both X-ray diffraction and selected area electron diffraction patterns are in good agreement with the reported theoretical results.The nano-laminated fracture of kink boundaries,delamination,and slipping were observed at the tip of the Vickers indents.The elastic modulus and Vickers hardness of Y_(3)Si_(2)C_(2) ceramics(with 5.5 wt%Y_(2)O_(3)) sintered at 1500℃were 156 and 6.4 GPa,respectively.The corresponding values of thermal and electrical conductivity were 13.7 W·m^(-1)·K^(-1) and 6.3×10^(5)S·m^(-1),respectively.展开更多
Unsteady flow in the hub endwall region has long been a hot topic in the turbomachinery community.However important it is to the performance of the whole engine,the coherent unsteady flow phenomena are still not well ...Unsteady flow in the hub endwall region has long been a hot topic in the turbomachinery community.However important it is to the performance of the whole engine,the coherent unsteady flow phenomena are still not well understood.In this paper,the complex flow field in the hub endwall of a cantilevered compressor cascade has been investigated through numerical approach.The predicted results were validated by experimental data.To highlight the dominant flow structures among irregular and chaotic motions of various vortices,a Dynamic Mode Decomposition(DMD)method was utilized.The results show that there exist three dominant periodic flow structures:the oscillation of the leakage vortex,a circumferential migration of a Breakdown Induced Vortex(BIV)and the fluctuation of the passage vortex.These three coherent structures all together form a self-sustained closed loop which accounts for the flow unsteadiness of the studied cascade.During this process,the BIV plays a key role in inducing the flow unsteadiness.Only if the BIV is strong enough to affect the passage vortex,the flow unsteadiness occurs.This study expands current knowledge base of flow unsteadiness in a compressor environment,and shows the efficacy of the DMD method for revealing the origin of flow unsteadiness.展开更多
A novel Y_(3)Si_(2)C_(2)material was synthesized at a relatively low temperature(900℃)using a molten salt method for the first time,and subsequently used as the joining material for carbon fiber reinforced SiC(Cf/SiC...A novel Y_(3)Si_(2)C_(2)material was synthesized at a relatively low temperature(900℃)using a molten salt method for the first time,and subsequently used as the joining material for carbon fiber reinforced SiC(Cf/SiC)composites.The sound near-seamless joints with no obvious remaining interlayer were obtained at 1600℃using an electric field-assisted sintering technique(FAST).During joining,a liquid phase was formed by the eutectic reaction among Y_(3)Si_(2)C_(2),γ(Y–C)phase,and SiC,followed by the precipitation of SiC particles.The presence of the liquid promoted the sintering of newly formed SiC particles,leading to their complete consolidation with the Cf/SiC matrix.On the other hand,the excess of the liquid was pushed away from the joining area under the effect of a uniaxial pressure of 30 MPa,leading to the formation of the near-seamless joints.The highest shear strength(Ä)of 17.2±2.9 MPa was obtained after being joined at 1600℃for 10 min.The failure of the joints occurred in the Cf/SiC matrix,indicating that the interface was stronger than that of the Cf/SiC matrix.The formation of a near-seamless joint minimizes the mismatch of thermal expansion coefficients and also irradiation-induced swelling,suggesting that the proposed joining strategy can be potentially applied to SiC-based ceramic matrix composites(CMCs)for extreme environmental applications.展开更多
Maternal sodium butyrate(SB)intake has important effects on offspring growth and development.This study aimed to investigate the impacts of maternal SB supplementation during gestation and lactation on fatty acid comp...Maternal sodium butyrate(SB)intake has important effects on offspring growth and development.This study aimed to investigate the impacts of maternal SB supplementation during gestation and lactation on fatty acid composition and lipid metabolism in the offspring skeletal muscle of pigs.Twenty sows(Yorkshire,parity 2 to 3)were assigned to the control group(diets without SB,n=10)and SB group(diets with 0.1%SB,n=10).The results showed maternal SB supplementation throughout gestation and lactation increased(P<0.05)body weight of offspring piglets at weaning.The concentrations of triglyceride in plasma and milk were enhanced(P<0.05).Maternal SB induced(P<0.05)lipid accumulation with increased expression of peroxisome proliferator activated receptorγ(PPARγ)by enrichment of the acetylation of H3 acetylation K27(H3 K27)in offspring skeletal muscle.Meanwhile,the concentrations of C18:2 n-6,C18:3 n-3,total polyunsaturated fatty acid(PUFA),n-6 PUFA and n-3 PUFA decreased(P<0.05)in skeletal muscle of weaning piglets derived from SB sows.Together,these results showed that maternal SB supplementation could influence offspring growth performance,lipid metabolism and fatty acid composition of the skeletal muscle.展开更多
基金supported by National Key R&D Program of China (2020AAA0107901).
文摘Latent information is difficult to get from the text in speech synthesis.Studies show that features from speech can get more information to help text encoding.In the field of speech encoding,a lot of work has been conducted on two aspects.The first aspect is to encode speech frame by frame.The second aspect is to encode the whole speech to a vector.But the scale in these aspects is fixed.So,encoding speech with an adjustable scale for more latent information is worthy of investigation.But current alignment approaches only support frame-by-frame encoding and speech-to-vector encoding.It remains a challenge to propose a new alignment approach to support adjustable scale speech encoding.This paper presents the dynamic speech encoder with a new alignment approach in conjunction with frame-by-frame encoding and speech-to-vector encoding.The speech feature fromourmodel achieves three functions.First,the speech feature can reconstruct the origin speech while the length of the speech feature is equal to the text length.Second,our model can get text embedding fromspeech,and the encoded speech feature is similar to the text embedding result.Finally,it can transfer the style of synthesis speech and make it more similar to the given reference speech.
基金Our work was supported by the research project of Yunnan University(Grant No.2021Y274)Natural Science Foundation of China(Grant No.61862064).
文摘Online advertising has gained much attention on various platforms as a hugely lucrative market.In promoting content and advertisements in real life,the acquisition of user target actions is usually a multi-step process,such as impres-sion→click→conversion,which means the process from the delivery of the recommended item to the user’s click to the final conversion.Due to data sparsity or sample selection bias,it is difficult for the trained model to achieve the business goal of the target campaign.Multi-task learning,a classical solution to this pro-blem,aims to generalize better on the original task given several related tasks by exploiting the knowledge between tasks to share the same feature and label space.Adaptively learned task relations bring better performance to make full use of the correlation between tasks.We train a general model capable of captur-ing the relationships between various tasks on all existing active tasks from a meta-learning perspective.In addition,this paper proposes a Multi-task Attention Network(MAN)to identify commonalities and differences between tasks in the feature space.The model performance is improved by explicitly learning the stacking of task relationships in the label space.To illustrate the effectiveness of our method,experiments are conducted on Alibaba Click and Conversion Pre-diction(Ali-CCP)dataset.Experimental results show that the method outperforms the state-of-the-art multi-task learning methods.
基金financially supported by the National Natural Science Foundation of China (41071041, U1203301)the West Light Foundation of Chinese Academy of Sciences (RCPY201101)
文摘Biological soil crusts （BSCs） are capable of modifying nutrient availability to favor the establishment of biogeochemical cycles. Microbial activities serve as critical roles for both carbon and nutrient transformation in BSCs. However, little is known about microbial activities and physical-chemical properties of BSCs in the Gurbantunggut Desert, Xinjiang, China. In the present research, a sampling line with 1-m wide and 20-m long was set up in each of five typical interdune areas selected randomly in the Gurbantunggut Desert. Within each sampling line, samples of bare sand sheet, algal crusts, lichen crusts and moss crusts were randomly collected at the depth of 0-2 cm. Varia- tions of microalgal biomass, microbial biomass, enzyme activities and soil physical-chemical properties in different succession of BSCs were analyzed. The relationships between microalgal biomass, microbial biomass, enzymatic activities and soil physical-chemical properties were explored by stepwise regression. Our results indicate that micro- algal biomass, microbial biomass and most of enzyme activities increased as the BSCs developed and their highest values occurred in lichen or moss crusts. Except for total K, the contents of most soil nutrients （organic C, total N, total P, available N, available P and available K） were the lowest in the bare sand sheet and significantly increased with the BSCs development, reaching their highest values in moss crusts. However, pH values significantly decreased as the BSCs developed. Significant and positive correlations were observed between chlorophyll a and microbial biomass C. Total P and N were positively associated with chlorophyll a and microbial biomass C, whereas there was a significant and negative correlation between microbial biomass and available P. The growth of cyanobacteria and microorganism contributed C and N in the soil, which offered substrates for enzyme activities thus increasing enzyme activities. Probably, improvement in enzyme activities increased soil fertility and promoted the growth of cyanobacteria, eukary- otic algae and heterotrophic microorganism, with the accelerating succession of BSCs. The present research found that microalgal-microbial biomass and enzyme activities played important roles on the contents of nutrients in the successional stages of BSCs and helped us to understand developmental mechanism in the succession of BSCs.
基金supported by grants from ‘hundred Talents Programme’ of The Chinese Academy of Sciences (KJCX2-EW-H06)Qianjiang excellent project (2011R10020) and Zhejiang NSF (Y4ll0376)+2 种基金National Natural Science Foundation of China (Grant No. 51172248)State Key Laboratory of Porous Metal Materials (PMM-SKL-1-2013)NSF-CMMI (grant number CMMI-0700272)
文摘The high temperature creep behavior of carbon nanotube(CNT)/alumina was mediated by the surface chemical functionalization used for synthesis of composite powders. Non-covalent functionalized carbon nanotubes make composites ductile, but covalent approach leads composites that are creep-resistant. Oxygen vacancy mechanism is proposed to account for this mediation effect in this communication.
基金supported by the National Natural Science Foundation of China(Grant Nos.12275337 and 11975296)the Natural Science Foundation of Ningbo City(Grant No.2021J199)+1 种基金We would like to recognize the support from the Ningbo 3315 Innovative Teams Program,China(Grant No.2019A-14-C)Thanks for the financial support of Advanced Energy Science and Technology Guangdong Laboratory(Grant No.HND20TDTHGC00).
文摘A novel class of high-entropy rare-earth metal diborodicarbide(Y_(0.2)5 Yb_(0.25)Dy_(0.25)Er_(0.25))B_(2)C_(2)(HE-REB_(2)C_(2))ceramics was successfully fabricated using the in-situ reactive spark plasma sintering(SPS)technology for the first time.Single solid solution with a typical tetragonal structure was formed,having a homogeneous distribution of four rare-earth elements,such as Y,Yb,Dy,and Er.Coefficients of thermal expansion(CTEs)along the a and c directions(aa and ac)were determined to be 4.18 and 16.06μK^(-1),respectively.Thermal expansion anisotropy of the as-obtained HE-REB_(2)C_(2)was attributed to anisotropy of the crystal structure of HE-REB_(2)C_(2).The thermal conductivity(k)of HE-REB_(2)C_(2)was 9.2±0.09 W·m^(-1)·K^(-1),which was lower than that of YB_(2)C_(2)(19.2±0.07 W·m^(-1)·K^(-1)),DyB_(2)C_(2)(11.90.06 W·m^(-1)·K^(-1)),and ErB_(2)C_(2)(12.10.03 W·m^(-1)·K^(-1)),due to high-entropy effect and sluggish diffusion effect of high-entropy ceramics(HECs).Furthermore,Vickers hardness of HE-REB_(2)C_(2)was slightly higher than that of REB_(2)C_(2)owing to the solid solution hardening mechanism of HECs.Typical nano-laminated fracture morphologies,such as kink boundaries,delamination,and slipping were observed at the tip of Vickers indents,suggesting ductile behavior of HE-REB_(2)C_(2).This newly investigated class of ductile HE-REB_(2)C_(2)ceramics expanded the family of HECs to diboridcarbide compounds,which can lead to more research works on high-entropy rare-earth diboridcarbides in the near future.
基金This study was supported by the National Natural Science Foundation of China(Grant Nos.11975296 and 51811540402)the Natural Science Foundation of Ningbo City(Grant No.2018A610001)the Korea Ministry of Education(NRF-2018K2A9A2A06018203).
文摘High strength SiC whisker-reinforced Ti3SiC2 composites(SiCw/Ti3SiC2)with an improved thermal conductivity and mechanical properties were fabricated by spark plasma sintering.The bending strength of 10 wt%SiCw/Ti3SiC2 was 635 MPa,which was approximately 50%higher than that of the monolithic Ti3SiC2(428 MPa).The Vickers hardness and thermal conductivity(k)also increased by 36%and 25%,respectively,from the monolithic Ti3SiC2 by the incorporation of 10 wt%SiCw.This remarkable improvement both in mechanical and thermal properties was attributed to the fine-grained uniform composite microstructure along with the effects of incorporated SiCw.The SiCw/Ti3SiC2 can be a feasible candidate for the in-core structural application in nuclear reactors due to the excellent mechanical and thermal properties.
基金This study was supported by the National Natural Science Foundation of China(Grant Nos.11975296 and 51811540402)the Natural Science Foundation of Ningbo City(Grant No.2018A610001).This work was also supported by the Slovak Research and Development Agency under the contract No.APVV-SK-CN-2017-0040.Peter TATARKO gratefully acknowledges the financial support of the project APVV-17-0328.
文摘The SiC/Al4SiC4 composites with the improved mechanical properties and thermal conductivity were fabricated by the in-situ reaction of polycarbosilane(PCS)and Al powders using spark plasma sintering.The addition of 5 wt%yttrium(Y)sintering additive was useful to obtain fully dense samples after sintering at a relatively low temperature of 1650℃,due to the formation of a liquid phase during sintering.The average particle size of the in-situ formed SiC was^300 nm.The fracture toughness(4.9 MPa·m1/2),Vickers hardness(16.3 GPa),and thermal conductivity(15.8 W/(m·K))of the SiC/Al4SiC4 composite sintered at 1650℃were significantly higher than the hardness(13.2 GPa),fracture toughness(2.16 MPa·m1/2),and thermal conductivity(7.8 W/(m·K))of the monolithic Al4SiC4 ceramics.The improved mechanical and thermal properties of the composites were attributed to the high density,fine grain size,as well as the optimized grain boundary structure of the SiC/Al4SiC4 composites.
基金the support from the Ningbo 3315 Innovative Teams Program,China(Grant No.2019A-14-C)This study was supported by the National Natural Science Foundation of China(Grant Nos.11975296 and 51811540402).
文摘A nano-laminated Y_(3)Si_(2)C_(2) ceramic material was successfully synthesized via an in situ reaction between YH_(2)and SiC using spark plasma sintering technology.A MAX phase-like ternary layered structure of Y_(3)Si_(2)C_(2) was observed at the atomic-scale by high resolution transmission electron microscopy.The lattice parameters calculated from both X-ray diffraction and selected area electron diffraction patterns are in good agreement with the reported theoretical results.The nano-laminated fracture of kink boundaries,delamination,and slipping were observed at the tip of the Vickers indents.The elastic modulus and Vickers hardness of Y_(3)Si_(2)C_(2) ceramics(with 5.5 wt%Y_(2)O_(3)) sintered at 1500℃were 156 and 6.4 GPa,respectively.The corresponding values of thermal and electrical conductivity were 13.7 W·m^(-1)·K^(-1) and 6.3×10^(5)S·m^(-1),respectively.
基金supports of National Natural Science Foundation of China(Nos.51790512,52176045)the National Major Science and technology Project of China(No.J2017-Ⅱ-0010-0024)the Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University,China(No.CX201911)。
文摘Unsteady flow in the hub endwall region has long been a hot topic in the turbomachinery community.However important it is to the performance of the whole engine,the coherent unsteady flow phenomena are still not well understood.In this paper,the complex flow field in the hub endwall of a cantilevered compressor cascade has been investigated through numerical approach.The predicted results were validated by experimental data.To highlight the dominant flow structures among irregular and chaotic motions of various vortices,a Dynamic Mode Decomposition(DMD)method was utilized.The results show that there exist three dominant periodic flow structures:the oscillation of the leakage vortex,a circumferential migration of a Breakdown Induced Vortex(BIV)and the fluctuation of the passage vortex.These three coherent structures all together form a self-sustained closed loop which accounts for the flow unsteadiness of the studied cascade.During this process,the BIV plays a key role in inducing the flow unsteadiness.Only if the BIV is strong enough to affect the passage vortex,the flow unsteadiness occurs.This study expands current knowledge base of flow unsteadiness in a compressor environment,and shows the efficacy of the DMD method for revealing the origin of flow unsteadiness.
基金This study was supported by the National Natural Science Foundation of China(Grant No.11975296)the Natural Science Foundation of Ningbo City(Grant No.2021J199)+3 种基金We would like to recognize the support from the Ningbo 3315 Innovative Teams Program,China(Grant No.2019A-14-C)Peter TATARKO gratefully acknowledges the financial support of the project APVV-17-0328this study was performed as part of the implementation of the project“Building-up Centre for advanced materials application of the Slovak Academy of Sciences”and ITMS project(Grant No.313021T081)supported by the Research&Innovation Operational Programme funded by the ERDF.
文摘A novel Y_(3)Si_(2)C_(2)material was synthesized at a relatively low temperature(900℃)using a molten salt method for the first time,and subsequently used as the joining material for carbon fiber reinforced SiC(Cf/SiC)composites.The sound near-seamless joints with no obvious remaining interlayer were obtained at 1600℃using an electric field-assisted sintering technique(FAST).During joining,a liquid phase was formed by the eutectic reaction among Y_(3)Si_(2)C_(2),γ(Y–C)phase,and SiC,followed by the precipitation of SiC particles.The presence of the liquid promoted the sintering of newly formed SiC particles,leading to their complete consolidation with the Cf/SiC matrix.On the other hand,the excess of the liquid was pushed away from the joining area under the effect of a uniaxial pressure of 30 MPa,leading to the formation of the near-seamless joints.The highest shear strength(Ä)of 17.2±2.9 MPa was obtained after being joined at 1600℃for 10 min.The failure of the joints occurred in the Cf/SiC matrix,indicating that the interface was stronger than that of the Cf/SiC matrix.The formation of a near-seamless joint minimizes the mismatch of thermal expansion coefficients and also irradiation-induced swelling,suggesting that the proposed joining strategy can be potentially applied to SiC-based ceramic matrix composites(CMCs)for extreme environmental applications.
基金supported by the National Key Research and Development Program of China(2016YFD0500502)the National Natural Science Foundation of China(31772696)。
文摘Maternal sodium butyrate(SB)intake has important effects on offspring growth and development.This study aimed to investigate the impacts of maternal SB supplementation during gestation and lactation on fatty acid composition and lipid metabolism in the offspring skeletal muscle of pigs.Twenty sows(Yorkshire,parity 2 to 3)were assigned to the control group(diets without SB,n=10)and SB group(diets with 0.1%SB,n=10).The results showed maternal SB supplementation throughout gestation and lactation increased(P<0.05)body weight of offspring piglets at weaning.The concentrations of triglyceride in plasma and milk were enhanced(P<0.05).Maternal SB induced(P<0.05)lipid accumulation with increased expression of peroxisome proliferator activated receptorγ(PPARγ)by enrichment of the acetylation of H3 acetylation K27(H3 K27)in offspring skeletal muscle.Meanwhile,the concentrations of C18:2 n-6,C18:3 n-3,total polyunsaturated fatty acid(PUFA),n-6 PUFA and n-3 PUFA decreased(P<0.05)in skeletal muscle of weaning piglets derived from SB sows.Together,these results showed that maternal SB supplementation could influence offspring growth performance,lipid metabolism and fatty acid composition of the skeletal muscle.
