A metal-semiconductor composite with the interracial shells is investigated theoretically for the large linear mag- netoresistance effect of high doping Ag2＋δ Se and Ag2＋δ te materials. The magnetoresistance （MR...A metal-semiconductor composite with the interracial shells is investigated theoretically for the large linear mag- netoresistance effect of high doping Ag2＋δ Se and Ag2＋δ te materials. The magnetoresistance （MR） of composites is a function of the magnetic field, temperature, the conductivities of two phases without magnetic field, and the thickness and conductivity of the interracial shells. The MR increases with the increase of the magnetic field and with the decrease of temperature, and no saturation is found even under the high magnetic field. Moreover, it is interestingly found that the interracial shell is an important factor for the MR of the composites. The MR increases with the thickness and the conductivity of the interfacial shells. Lastly, the theoretical results on the MR are compared with the experimental data. It is found that the value of the MR of the composite with the interfacial shell is larger than that without the interfacial shell.展开更多
The two-dimensional infiltration experiment was carried out by means of digital image technology.The evolution process of the wetting body was described.The wetted front distance and the time show a very significant p...The two-dimensional infiltration experiment was carried out by means of digital image technology.The evolution process of the wetting body was described.The wetted front distance and the time show a very significant power function relationship.The horizontal wetted distance is larger than the vertical wetted distance in the initial stage.Then,the vertical distance of the wetted body gradually approaches to the horizontal distance.The infiltration distance decreases as the content of fine particles increases.The wetted front migration rate curve shows a three-stage change law,and it increases with the increase of coarse particle content.The directional velocity ratio is defined.The initial value of horizontal infiltration rate is larger than that of vertical one,and then the vertical infiltration rate is gradually close to the horizontal value.The empirical relationship between the characteristic particle size and the stable infiltration rate is established,which provides a theoretical basis for the prediction of the stable infiltration rate in in-situ leaching.展开更多
A global two-dimensional zonally averaged chemistry model is developed to study the chemi-cal composition of atmosphere. The region of the model is from 90°S to 90°N and from the ground to the altitude of 20...A global two-dimensional zonally averaged chemistry model is developed to study the chemi-cal composition of atmosphere. The region of the model is from 90°S to 90°N and from the ground to the altitude of 20 km with a resolution of 5° x 1 km. The wind field is residual circulation calcu-lated from diabatic rate. 34 species and 104 chemical and photochemical reactions are considered in the model. The sources of CH4, CO and NOx, which are divided into seasonal sources and non-seasonal sources, are parameterized as a function of latitude and time. The chemical composi-tion of atmosphere was simulated with emission level of CH4, CO and NOx in 1990. The results are compared with observations and other model results, showing that the model is successful to simu-late the atmospheric chemical composition and distribution of CH4. Key words Global two-dimensional chemistry model - Atmospheric composition - Emission This work was supported by the State Key Program for basic research “ Climate Dynamics and Cli-mate Prediction Theory” (Pandeng-yu-21).The authors would like to express their thanks to the National Oceanic and Atmospheric Administration (NOAA), Climate Monitoring and Diagnostics Laboratory (CMDL), Carbon Cycle Group for providing the observational data of CO and CH4.展开更多
A novel multi-point sensing scheme to improve the signal-to-noise ratio(SNR),temperature measurement range of the fiber Bragg grating(FBG)sensors is proposed.The new sensing scheme adopted a composite coding technique...A novel multi-point sensing scheme to improve the signal-to-noise ratio(SNR),temperature measurement range of the fiber Bragg grating(FBG)sensors is proposed.The new sensing scheme adopted a composite coding technique based on Simplex codes and Golay codes and time division multiplexing technique to enhance the performance of the sensing system.Simulation results,in good agreement with the theory,confirmed that the maximum SNR enhancement of the sensor system employing composite coding based on 15-bit Simplex codes and 16-bit Golay codes was approximately 6.01 dB in comparison to the conventional single pulse case.展开更多
Metal halide perovskite nanocrystals(NCs)exhibit impressive optical and electronic properties,making them an important class of functional materials with promising applications in solar cells,light emitting diodes(LED...Metal halide perovskite nanocrystals(NCs)exhibit impressive optical and electronic properties,making them an important class of functional materials with promising applications in solar cells,light emitting diodes(LEDs),photodetectors,and photocatalysts.In addition to the widely studied 0-dimensional(0 D)metal halide perovskite NCs,such as nanocubes,low dimensional perovskites,such as 2 D all-inorganic perovskite(AIP)NCs,subsist with directionally relevant quantum confinement.These anisotropic NCs have the propensity to exhibit interesting optoelectronic properties that are exceedingly difficult to introduce into 0 D systems,yet as of late are largely unexplored.In this review,we discuss the recent synthetic progress of 2 D all-inorganic metal halide perovskite NCs with ABX3 structure.Specifically,we highlight the discrete composition control of the cations(A and B sites)and anions(X site)by dopant incorporation and alloying in 2 D metal halide perovskite NCs.We will also discuss more complex perovskite crystal structures,such as Ruddlesden-Popper double perovskites,and compare these materials to 0 D perovskite systems.Ultimately,our work culminates in the future interests and perspectives of this field with a focus on the wide applicability of 2 D systems and the large variance in structure capable with discrete compositional tuning.展开更多
According to a mathematical model which describes the curing process of composites constructed from continuous fiber-reinforced, thermosetting resin matrix prepreg materials, and the consolidation of the composites, t...According to a mathematical model which describes the curing process of composites constructed from continuous fiber-reinforced, thermosetting resin matrix prepreg materials, and the consolidation of the composites, the solution method to the model is made and a computer code is developed, which for flat-plate composites cured by a specified cure cycle, provides the variation of temperature distribution, the cure reaction process in the resin, the resin flow and fibers stress inside the composite, the void variation and the residual stress distribution.展开更多
The preferred internal oxidation of aluminum in Cu Al alloy was used to obtain in situ Al 2O 3/Cu composites. The reinforcement particles were mainly γ Al 2O 3, some θ Al 2O 3 and a little α Al 2O 3. Thermodynamics...The preferred internal oxidation of aluminum in Cu Al alloy was used to obtain in situ Al 2O 3/Cu composites. The reinforcement particles were mainly γ Al 2O 3, some θ Al 2O 3 and a little α Al 2O 3. Thermodynamics analyses show that the chemical reactions are 3Cu 2O+2Al=6Cu+Al 2O 3 or 3CuO+2Al=3Cu+Al 2O 3. A related equilibrium diagram was drawn. The experiments and investigation show that the formation rate of Al 2O 3 was controlled by the diffusion of oxygen in matrix.展开更多
An in situ synthesized TiC particle reinforced composite layer on Ti6Al4V were fabricated by laser induced reaction of the pre placed mixed powders of Ti and Cr 3C 2. The microstructure of the composite layer was stro...An in situ synthesized TiC particle reinforced composite layer on Ti6Al4V were fabricated by laser induced reaction of the pre placed mixed powders of Ti and Cr 3C 2. The microstructure of the composite layer was strongly related to the composition of original powders and also the laser processing parameters. Under certain processing parameters, the matrix of the composite layer was transferred from dual α + β to single phase β with increasing Cr 3C 2 content in the original powder mixture. The TiC particles were fine and uniformly dispersed in the matrix. Furthermore, the fine TiC particles show excellent compatibility with the matrix, thus offering good wear performance.展开更多
In recent years, graphene has been widely employed in the field of metal corrosion protection owing to its outstanding impermeability and chemical stability, with examples of such metal protection including pure graph...In recent years, graphene has been widely employed in the field of metal corrosion protection owing to its outstanding impermeability and chemical stability, with examples of such metal protection including pure graphene coatings and graphene-based composite coatings. But the conductive graphene could promote the electrochemical reaction at the interface and accelerate the corrosion of metal substrates. More emerging graphene-like 2D nanosheets are attracting research attention for the application of metal anticorrosion, because of their barrier properties and poor conductivity, mainly including boron nitride(BN),molybdenum disulfide(MoS_(2)), zirconium phosphate(ZrP), and titanium carbide(MXene). In this review,the application of these graphene-like 2D nanosheets to metal protection is comprehensively reviewed.First, the general preparation methods of 2D nanosheets are briefly introduced. Second, surface functionalization of 2D nanosheets, including covalent and non-covalent modification, is described in detail.Third, the anticorrosion performance and optimization measures of pure 2D nanosheets coatings are summarized. Next, the protection performance, anticorrosive mechanism, and optimizations of 2D nanosheets composite coatings are presented. Finally, the future development of 2D nanosheets-based anticorrosive coatings has been prospected, and the challenges in the industrial application are discussed.展开更多
The behavior of ceramic particles at the solid/liquid interface and the distribution of particles in metallic matrix composites was studied with a zone unidirectional solidification method. Two kinds of partice disper...The behavior of ceramic particles at the solid/liquid interface and the distribution of particles in metallic matrix composites was studied with a zone unidirectional solidification method. Two kinds of partice dispersed composites, Al 2O 3P /Al 12.6%Si Sr and Al 2O 3P /Al 12.6%Si Sr Ca containing Al 2O 3 particles in volume fraction 2%～5% were used. In the Al 2O 3P /Al Si Sr composites, the particles were pushed by the solidifying front, and did not uniformly distribute in the solid. But in the Al 2O 3P /Al Si Sr Ca composites, the particles were engulfed by the solidifying front and uniformly distributed in the solid. The particles engulfing into the solid was realized only by Sr and Ca addition at the same time. As the interfacial energy between solid and particle was decreased in this case, the Al 2O 3 particles acted as the substrates of heterogeneous nucleation for the Si phases, which made the particles to be engulfed.展开更多
For higher efficiency and precision manufacturing,more and more attentions are focused on the surface roughness and residual stress of machined parts to obtain a good fatigue life.At present,the in-situ TiB_2/7050 Al ...For higher efficiency and precision manufacturing,more and more attentions are focused on the surface roughness and residual stress of machined parts to obtain a good fatigue life.At present,the in-situ TiB_2/7050 Al metal matrix composites are widely researched due to its attractive properties such as low density,good wear resistance and improved strength.It is of great significance to investigate the machined surface roughness,residual stress and fatigue life for higher efficiency and precision manufacturing of this new kind material.In this study,the surface roughness including two-dimensional and three-dimensional roughness,residual stress and fatigue life of milling in-situ TiB_2/7050 Al metal matrix composites were analyzed.It was found from comparative investigation that the three-dimensional surface roughness would be more appropriate to represent the machined surface profile of milling particle reinforced metal matrix composites.The cutting temperature played a great role on the residual stress.However,the effect of increasing cutting force could slow down the transformation from compressive stress to tensile stress under 270°C.An exponential relationship between three-dimensional roughness and fatigue life was established and the main fracture mechanism was brittle fracture with observation of obvious shellfish veins,river pattern veins and wave shaped veins in fracture surface.展开更多
Let Ф（u ×v, k, Aa, Ac） be the largest possible number of codewords among all two- dimensional （u ×v, k, λa, λc） optical orthogonal codes. A 2-D （u× v, k, λa, λ）-OOC with Ф（u× v, k, λ...Let Ф（u ×v, k, Aa, Ac） be the largest possible number of codewords among all two- dimensional （u ×v, k, λa, λc） optical orthogonal codes. A 2-D （u× v, k, λa, λ）-OOC with Ф（u× v, k, λa, λc） codewords is said to be maximum. In this paper, the number of codewords of a maximum 2-D （u × v, 4, 1, 3）-OOC has been determined.展开更多
After describing the characteristics of programming paradigm, this paper introduces the approach of code component composition reuse in detail, proposes and discusses viewpoint that code component composition reuse is...After describing the characteristics of programming paradigm, this paper introduces the approach of code component composition reuse in detail, proposes and discusses viewpoint that code component composition reuse is a kind of new programming paradigm. This paper also specifies the characteristics of this new programming paradigm in detail, and points out some issues that must be resolved for using this new programming paradigm.展开更多
As the complexity of space exploration missions augments,how to enhance the overall performance of communication,ranging or other functions has become a challengeable problem.Considering the integration of communicati...As the complexity of space exploration missions augments,how to enhance the overall performance of communication,ranging or other functions has become a challengeable problem.Considering the integration of communication and ranging,we present a bit-level composite signal for simultaneous ranging and communication.In this composite method,through a specially designed mapping scheme using low-weight codewords,the information sequence is converted to a sparse sequence which is then superimposed on the ranging code.For ranging,the correlation characteristics of the ranging code component can be maintained to calculate the transmitter-receiver distance.For communications,the sparse sequence can be extracted without interference by eliminating the ranging code component.Simulation results show that the proposed composite signal can support communication and ranging simultaneously with limited sacrifice of ranging performance,and the performance loss of ranging can be controlled and minimized by lowering the density of information sequences using different sparsification encoding methods.展开更多
A room-temperature electrodeposition method with an organic electrolyte was developed to fabricate a HNO3-pretreated graphene paper Cu(GP'-Cu)composite.To improve the interfacial bonding of GP'-Cu composite,ma...A room-temperature electrodeposition method with an organic electrolyte was developed to fabricate a HNO3-pretreated graphene paper Cu(GP'-Cu)composite.To improve the interfacial bonding of GP'-Cu composite,magnetron sputtering technology was used to create a"sandwich"structural gradient GP'-Cu composite.The selection of the intermediate transition layer metal was based on two-dimensional disregistry.Scanning electron microscopy,X-ray photoelectron spectroscopy,and other analytical methods confirmed that the addition of an intermediate transition metal(Cr,Ni)layer reduced the gap distance and enhanced the interfacial bonding of the GP'and Cu deposited layers.The GP'-Ni-Cu composite exhibited the largest increase in tensile strength and conductivity.In addition,it had the highest thermal diffusivity and elongation at break among the GP'-Cu,GP'-Cr-Cu and GP'-Ni-Cu composites.展开更多
The manufacturing of three-dimensional textile preforms used for composites started to re-ceive much attention in the last decade.The major barriers to accelerating the transition from thelamination of two-dimensional...The manufacturing of three-dimensional textile preforms used for composites started to re-ceive much attention in the last decade.The major barriers to accelerating the transition from thelamination of two-dimensional fabrics to manufacturing integral three-dimensional near-netshaped textile preforms are high cost and database deficiency.To reduce the cost of weaving three-dimensional preforms,and make full use of the potential of conventional looms,a rig was designedwhich can convert two-dimensional woven fabric to particular three-dimensional preforms wherethe yarn is orientated in the directions of maximum stress.展开更多
A mathematical model is made which describes the curing process of composites constructed from continuous fiber-reinforced, thermosetting resin matrix prepreg materials, and the consolidation of the composite is devel...A mathematical model is made which describes the curing process of composites constructed from continuous fiber-reinforced, thermosetting resin matrix prepreg materials, and the consolidation of the composite is developed. The model provides the variation of temperature distribution, the cure reaction process in the resin, the resin flow and fibers stress inside the composite, and the void variation and the residual stress distribution. It can be used to illustrate the mechanism of curing process and optimize the cure cycle of composite material in order to ensure the quality of a product.展开更多
In distributed computing environment,workflow technologies have been continuously developed.Recently,there is an attempt to apply these technologies to context-aware services in ubiquitous computing environment.The mi...In distributed computing environment,workflow technologies have been continuously developed.Recently,there is an attempt to apply these technologies to context-aware services in ubiquitous computing environment.The middleware,which offers services in such environments,should support the automation services suited for the user using various types of situational information around the user.In this paper,based on context-aware workflow language(CAWL),we propose a CAWL based composite workflow handler for supporting composite workflow services,which can integrate more than two service flows and handle them.The test results shows that the proposed CAWL handler can provide the user with the composite workflow services to cope with various demands on a basis of a scenario document founded on CAWL.展开更多
在一些修船企业建立的修船结算系统和电子价格库中,人工匹配结算编码步骤易出错且耗时长,直接影响结算效率。为解决该问题,提出一种基于多特征融合的修船结算编码智能匹配复合模型。采用来自变换器的双向编码器表示(Bidirectional Encod...在一些修船企业建立的修船结算系统和电子价格库中,人工匹配结算编码步骤易出错且耗时长,直接影响结算效率。为解决该问题,提出一种基于多特征融合的修船结算编码智能匹配复合模型。采用来自变换器的双向编码器表示(Bidirectional Encoder Representations from Transformers,BERT)模型将工程内容文本表示为词向量,采用卷积神经网络(Convolutional Neural Network,CNN)模型提取文本的局部特征,采用双向长短期记忆网络结合注意力机制(Bidirectional Long Short-Term Memory with Attention Mechanism,BiLSTM-Attention)模型提取上下文特征,得到对应的结算编码。试验结果表明,所提出的复合模型在整体准确率方面实现显著提升,充分证明该复合模型在处理复杂文本分类任务中的优势。展开更多
基金Supported by the China Postdoctoral Science Foundation under Grant No 2014MM551868the Science and Technology Development Guidance Program of Qingdao under Grant No KJZD-13-35-JCH
文摘A metal-semiconductor composite with the interracial shells is investigated theoretically for the large linear mag- netoresistance effect of high doping Ag2＋δ Se and Ag2＋δ te materials. The magnetoresistance （MR） of composites is a function of the magnetic field, temperature, the conductivities of two phases without magnetic field, and the thickness and conductivity of the interracial shells. The MR increases with the increase of the magnetic field and with the decrease of temperature, and no saturation is found even under the high magnetic field. Moreover, it is interestingly found that the interracial shell is an important factor for the MR of the composites. The MR increases with the thickness and the conductivity of the interfacial shells. Lastly, the theoretical results on the MR are compared with the experimental data. It is found that the value of the MR of the composite with the interfacial shell is larger than that without the interfacial shell.
基金Projects(51764014,11902127)supported by the National Natural Science Foundation of ChinaProject(201810407004)supported by the National Undergraduate Innovation Training Program of ChinaProject(GJJ180457)supported by Jiangxi Education Department,China。
文摘The two-dimensional infiltration experiment was carried out by means of digital image technology.The evolution process of the wetting body was described.The wetted front distance and the time show a very significant power function relationship.The horizontal wetted distance is larger than the vertical wetted distance in the initial stage.Then,the vertical distance of the wetted body gradually approaches to the horizontal distance.The infiltration distance decreases as the content of fine particles increases.The wetted front migration rate curve shows a three-stage change law,and it increases with the increase of coarse particle content.The directional velocity ratio is defined.The initial value of horizontal infiltration rate is larger than that of vertical one,and then the vertical infiltration rate is gradually close to the horizontal value.The empirical relationship between the characteristic particle size and the stable infiltration rate is established,which provides a theoretical basis for the prediction of the stable infiltration rate in in-situ leaching.
文摘A global two-dimensional zonally averaged chemistry model is developed to study the chemi-cal composition of atmosphere. The region of the model is from 90°S to 90°N and from the ground to the altitude of 20 km with a resolution of 5° x 1 km. The wind field is residual circulation calcu-lated from diabatic rate. 34 species and 104 chemical and photochemical reactions are considered in the model. The sources of CH4, CO and NOx, which are divided into seasonal sources and non-seasonal sources, are parameterized as a function of latitude and time. The chemical composi-tion of atmosphere was simulated with emission level of CH4, CO and NOx in 1990. The results are compared with observations and other model results, showing that the model is successful to simu-late the atmospheric chemical composition and distribution of CH4. Key words Global two-dimensional chemistry model - Atmospheric composition - Emission This work was supported by the State Key Program for basic research “ Climate Dynamics and Cli-mate Prediction Theory” (Pandeng-yu-21).The authors would like to express their thanks to the National Oceanic and Atmospheric Administration (NOAA), Climate Monitoring and Diagnostics Laboratory (CMDL), Carbon Cycle Group for providing the observational data of CO and CH4.
基金Graduate Project Foundation of Shanghai Polytechnic University,China(No.A01GY18F022)
文摘A novel multi-point sensing scheme to improve the signal-to-noise ratio(SNR),temperature measurement range of the fiber Bragg grating(FBG)sensors is proposed.The new sensing scheme adopted a composite coding technique based on Simplex codes and Golay codes and time division multiplexing technique to enhance the performance of the sensing system.Simulation results,in good agreement with the theory,confirmed that the maximum SNR enhancement of the sensor system employing composite coding based on 15-bit Simplex codes and 16-bit Golay codes was approximately 6.01 dB in comparison to the conventional single pulse case.
基金support from Syracuse University under the Collaboration for Unprecedented Success and Excellence(CUSE)Grant(SD-10-2020)ACS Petroleum Research Fund under Award Number 59861-DNI5NSF CAREER under Award Number CHE-1944978。
文摘Metal halide perovskite nanocrystals(NCs)exhibit impressive optical and electronic properties,making them an important class of functional materials with promising applications in solar cells,light emitting diodes(LEDs),photodetectors,and photocatalysts.In addition to the widely studied 0-dimensional(0 D)metal halide perovskite NCs,such as nanocubes,low dimensional perovskites,such as 2 D all-inorganic perovskite(AIP)NCs,subsist with directionally relevant quantum confinement.These anisotropic NCs have the propensity to exhibit interesting optoelectronic properties that are exceedingly difficult to introduce into 0 D systems,yet as of late are largely unexplored.In this review,we discuss the recent synthetic progress of 2 D all-inorganic metal halide perovskite NCs with ABX3 structure.Specifically,we highlight the discrete composition control of the cations(A and B sites)and anions(X site)by dopant incorporation and alloying in 2 D metal halide perovskite NCs.We will also discuss more complex perovskite crystal structures,such as Ruddlesden-Popper double perovskites,and compare these materials to 0 D perovskite systems.Ultimately,our work culminates in the future interests and perspectives of this field with a focus on the wide applicability of 2 D systems and the large variance in structure capable with discrete compositional tuning.
文摘According to a mathematical model which describes the curing process of composites constructed from continuous fiber-reinforced, thermosetting resin matrix prepreg materials, and the consolidation of the composites, the solution method to the model is made and a computer code is developed, which for flat-plate composites cured by a specified cure cycle, provides the variation of temperature distribution, the cure reaction process in the resin, the resin flow and fibers stress inside the composite, the void variation and the residual stress distribution.
文摘The preferred internal oxidation of aluminum in Cu Al alloy was used to obtain in situ Al 2O 3/Cu composites. The reinforcement particles were mainly γ Al 2O 3, some θ Al 2O 3 and a little α Al 2O 3. Thermodynamics analyses show that the chemical reactions are 3Cu 2O+2Al=6Cu+Al 2O 3 or 3CuO+2Al=3Cu+Al 2O 3. A related equilibrium diagram was drawn. The experiments and investigation show that the formation rate of Al 2O 3 was controlled by the diffusion of oxygen in matrix.
文摘An in situ synthesized TiC particle reinforced composite layer on Ti6Al4V were fabricated by laser induced reaction of the pre placed mixed powders of Ti and Cr 3C 2. The microstructure of the composite layer was strongly related to the composition of original powders and also the laser processing parameters. Under certain processing parameters, the matrix of the composite layer was transferred from dual α + β to single phase β with increasing Cr 3C 2 content in the original powder mixture. The TiC particles were fine and uniformly dispersed in the matrix. Furthermore, the fine TiC particles show excellent compatibility with the matrix, thus offering good wear performance.
基金financially supported by the National Natural Science Foundation of China(No.51973231)Guangdong Basic and Applied Basic Research Foundation(Nos.2021A1515012449,2019A1515010743)+1 种基金the Fundamental Research Funds for the Central Universities,Sun Yat-sen University(No.20lgzd17)Open Project from State Key Laboratory of Inorganic Synthesis and Preparative Chemistry(No.2020-31)。
文摘In recent years, graphene has been widely employed in the field of metal corrosion protection owing to its outstanding impermeability and chemical stability, with examples of such metal protection including pure graphene coatings and graphene-based composite coatings. But the conductive graphene could promote the electrochemical reaction at the interface and accelerate the corrosion of metal substrates. More emerging graphene-like 2D nanosheets are attracting research attention for the application of metal anticorrosion, because of their barrier properties and poor conductivity, mainly including boron nitride(BN),molybdenum disulfide(MoS_(2)), zirconium phosphate(ZrP), and titanium carbide(MXene). In this review,the application of these graphene-like 2D nanosheets to metal protection is comprehensively reviewed.First, the general preparation methods of 2D nanosheets are briefly introduced. Second, surface functionalization of 2D nanosheets, including covalent and non-covalent modification, is described in detail.Third, the anticorrosion performance and optimization measures of pure 2D nanosheets coatings are summarized. Next, the protection performance, anticorrosive mechanism, and optimizations of 2D nanosheets composite coatings are presented. Finally, the future development of 2D nanosheets-based anticorrosive coatings has been prospected, and the challenges in the industrial application are discussed.
文摘The behavior of ceramic particles at the solid/liquid interface and the distribution of particles in metallic matrix composites was studied with a zone unidirectional solidification method. Two kinds of partice dispersed composites, Al 2O 3P /Al 12.6%Si Sr and Al 2O 3P /Al 12.6%Si Sr Ca containing Al 2O 3 particles in volume fraction 2%～5% were used. In the Al 2O 3P /Al Si Sr composites, the particles were pushed by the solidifying front, and did not uniformly distribute in the solid. But in the Al 2O 3P /Al Si Sr Ca composites, the particles were engulfed by the solidifying front and uniformly distributed in the solid. The particles engulfing into the solid was realized only by Sr and Ca addition at the same time. As the interfacial energy between solid and particle was decreased in this case, the Al 2O 3 particles acted as the substrates of heterogeneous nucleation for the Si phases, which made the particles to be engulfed.
基金National Natural Science Foundation of China(No.51775443)National Science and Technology Major Project of China(No.2017-VII-00150111)。
文摘For higher efficiency and precision manufacturing,more and more attentions are focused on the surface roughness and residual stress of machined parts to obtain a good fatigue life.At present,the in-situ TiB_2/7050 Al metal matrix composites are widely researched due to its attractive properties such as low density,good wear resistance and improved strength.It is of great significance to investigate the machined surface roughness,residual stress and fatigue life for higher efficiency and precision manufacturing of this new kind material.In this study,the surface roughness including two-dimensional and three-dimensional roughness,residual stress and fatigue life of milling in-situ TiB_2/7050 Al metal matrix composites were analyzed.It was found from comparative investigation that the three-dimensional surface roughness would be more appropriate to represent the machined surface profile of milling particle reinforced metal matrix composites.The cutting temperature played a great role on the residual stress.However,the effect of increasing cutting force could slow down the transformation from compressive stress to tensile stress under 270°C.An exponential relationship between three-dimensional roughness and fatigue life was established and the main fracture mechanism was brittle fracture with observation of obvious shellfish veins,river pattern veins and wave shaped veins in fracture surface.
基金Supported by the National Natural Science Foundation of China(61071221,10831002)
文摘Let Ф（u ×v, k, Aa, Ac） be the largest possible number of codewords among all two- dimensional （u ×v, k, λa, λc） optical orthogonal codes. A 2-D （u× v, k, λa, λ）-OOC with Ф（u× v, k, λa, λc） codewords is said to be maximum. In this paper, the number of codewords of a maximum 2-D （u × v, 4, 1, 3）-OOC has been determined.
文摘After describing the characteristics of programming paradigm, this paper introduces the approach of code component composition reuse in detail, proposes and discusses viewpoint that code component composition reuse is a kind of new programming paradigm. This paper also specifies the characteristics of this new programming paradigm in detail, and points out some issues that must be resolved for using this new programming paradigm.
基金This work was supported in part by National Natural Science Foundation of China(61671324)the Director’s Funding from Pilot National Laboratory for Marine Science and Technology(Qingdao)(QNLM201712)Zhan Xu was supported in part by National Natural Science Foundation of China(61620106001).
文摘As the complexity of space exploration missions augments,how to enhance the overall performance of communication,ranging or other functions has become a challengeable problem.Considering the integration of communication and ranging,we present a bit-level composite signal for simultaneous ranging and communication.In this composite method,through a specially designed mapping scheme using low-weight codewords,the information sequence is converted to a sparse sequence which is then superimposed on the ranging code.For ranging,the correlation characteristics of the ranging code component can be maintained to calculate the transmitter-receiver distance.For communications,the sparse sequence can be extracted without interference by eliminating the ranging code component.Simulation results show that the proposed composite signal can support communication and ranging simultaneously with limited sacrifice of ranging performance,and the performance loss of ranging can be controlled and minimized by lowering the density of information sequences using different sparsification encoding methods.
基金Key Laboratory of Particle Acceleration Physics&Technology,Institute of High Energy Physics,Chinese Academy of Sciences(JSQ2022KF01 and JSQ2020ZZ05)National Natural Science Foundation of China(12035017)+2 种基金Youth Innovation Promotion Association CAS(2019016)National Natural Science Foundation of China Youth Project(No.51704021)Fundamental Scientific Research Business Expenses of Central Universities(FRF-IDRY-20-015,FRF-TP-20-004A3,FRF-TP-19-030A2,and FRF-TP-16-079A1)are greatly appreciated.
文摘A room-temperature electrodeposition method with an organic electrolyte was developed to fabricate a HNO3-pretreated graphene paper Cu(GP'-Cu)composite.To improve the interfacial bonding of GP'-Cu composite,magnetron sputtering technology was used to create a"sandwich"structural gradient GP'-Cu composite.The selection of the intermediate transition layer metal was based on two-dimensional disregistry.Scanning electron microscopy,X-ray photoelectron spectroscopy,and other analytical methods confirmed that the addition of an intermediate transition metal(Cr,Ni)layer reduced the gap distance and enhanced the interfacial bonding of the GP'and Cu deposited layers.The GP'-Ni-Cu composite exhibited the largest increase in tensile strength and conductivity.In addition,it had the highest thermal diffusivity and elongation at break among the GP'-Cu,GP'-Cr-Cu and GP'-Ni-Cu composites.
文摘The manufacturing of three-dimensional textile preforms used for composites started to re-ceive much attention in the last decade.The major barriers to accelerating the transition from thelamination of two-dimensional fabrics to manufacturing integral three-dimensional near-netshaped textile preforms are high cost and database deficiency.To reduce the cost of weaving three-dimensional preforms,and make full use of the potential of conventional looms,a rig was designedwhich can convert two-dimensional woven fabric to particular three-dimensional preforms wherethe yarn is orientated in the directions of maximum stress.
文摘A mathematical model is made which describes the curing process of composites constructed from continuous fiber-reinforced, thermosetting resin matrix prepreg materials, and the consolidation of the composite is developed. The model provides the variation of temperature distribution, the cure reaction process in the resin, the resin flow and fibers stress inside the composite, and the void variation and the residual stress distribution. It can be used to illustrate the mechanism of curing process and optimize the cure cycle of composite material in order to ensure the quality of a product.
基金The MSIP(Ministry of Science,ICT&Future Planning),Korea,under the ITRC(Information Technology Research Center)support program(NIPA-2013-H0301-13-2006)supervised by the NIPA(National IT Industry Promotion Agency)
文摘In distributed computing environment,workflow technologies have been continuously developed.Recently,there is an attempt to apply these technologies to context-aware services in ubiquitous computing environment.The middleware,which offers services in such environments,should support the automation services suited for the user using various types of situational information around the user.In this paper,based on context-aware workflow language(CAWL),we propose a CAWL based composite workflow handler for supporting composite workflow services,which can integrate more than two service flows and handle them.The test results shows that the proposed CAWL handler can provide the user with the composite workflow services to cope with various demands on a basis of a scenario document founded on CAWL.
文摘在一些修船企业建立的修船结算系统和电子价格库中,人工匹配结算编码步骤易出错且耗时长,直接影响结算效率。为解决该问题,提出一种基于多特征融合的修船结算编码智能匹配复合模型。采用来自变换器的双向编码器表示(Bidirectional Encoder Representations from Transformers,BERT)模型将工程内容文本表示为词向量,采用卷积神经网络(Convolutional Neural Network,CNN)模型提取文本的局部特征,采用双向长短期记忆网络结合注意力机制(Bidirectional Long Short-Term Memory with Attention Mechanism,BiLSTM-Attention)模型提取上下文特征,得到对应的结算编码。试验结果表明,所提出的复合模型在整体准确率方面实现显著提升,充分证明该复合模型在处理复杂文本分类任务中的优势。
