Ni/TiAl composite brazed joints could significantly reduce the aircraft’s weight.However,low interfacial adhesion,coarse and brittle-hard intermetallic compounds(IMCs)seriously limited the application of Ni/TiAl comp...Ni/TiAl composite brazed joints could significantly reduce the aircraft’s weight.However,low interfacial adhesion,coarse and brittle-hard intermetallic compounds(IMCs)seriously limited the application of Ni/TiAl composite joints in the next generation of aerospace applications.So enhanced K4169/TiAl composite joints were investigated by vacuum brazed with(Ni_(53.33)Cr_(20)B_(16.67)Si_(10)/Zr_(25)Ti_(18.75)Ta_(12.5)Ni_(25)Cu_(18.75))composite filler metal(CFM)designed based on cluster-plus-glue-atom model.The shear strength of the joint reached 485 MPa,comparable to the 491 MPa of TiAl substrate.The flat and brittle-hard diffusion reaction layer between Zones I and II was eliminated,simultaneously generating CrB4 dispersion strengthening due to the CFM developed with the interfacial solid-liquid space-time hysteresis effect.In Zones II and III,IMCs all transformed into Niss(Cr,Fe)_([0–88]),Niss(Ti,Al)_([004]),and Niss(Zr,Si)_([11–2])of circular and oval shapes through isothermal solidification.Meanwhile,the residual stresses and hardness were distributed in reticulated cladding characteristics.Thereby,lattice distortion led to solid solution strengthening and increased plastic toughness through crack termination and bridging mechanisms,which inhibited dislocations from plugging and crack propagation.Various interfaces in ZoneⅣwere regulated into semi-and coherent interfaces.Ni3(Ti,Al)/(Ni,Ti,Al)and(Ni,Ti,Al)/AlNi_(2)Ti were composed of higher interfacial bonding energy(2.771 J/m^(2),2.547 J/m^(2))and Ni-Ni covalent bonds.Interfacial covalent bonding and large interfacial bonding energy coupling strengthened Zone IV.Consequently,cracks initiated at the(Ni,Ti,Al)[013]/Ti3Al_([010])and expanded rapidly into TiAl substrate.Therefore,applying this method to design CFMs and regulate the phase,grain morphology,and interface’s fine structure could provide new pathways for dissimilar hard-to-join metals.展开更多
This study was done to evaluate the nugget zone(NZ)corrosion behavior of dissimilar copper/brass joints welded by friction stir lap welding(FSLW)in a solution of 0.015 mol/L borax(pH 9.3).To this end,dissimilar copper...This study was done to evaluate the nugget zone(NZ)corrosion behavior of dissimilar copper/brass joints welded by friction stir lap welding(FSLW)in a solution of 0.015 mol/L borax(pH 9.3).To this end,dissimilar copper/brass plates were welded with two dissimilar heat inputs(low and high)during the welding procedure.The high and low heat inputs were conducted with 710 r/min,16 mm/min and 450 r/min,25 mm/min,respectively.Using open circuit potential(OCP)measurements,electrochemical impedance spectroscopy(EIS)and Tafel polarization tests,the electrochemical behavior of the specimens in borate buffer solution was assessed.With the help of scanning electron microscope(SEM),the morphology of welded specimen surfaces was examined after immersion in the test solution.According to the results,the NZ grain size and resistance improvement reduced due to the nugget zone corrosion with a decreased heat input.The results obtained from Tafel polarization and EIS indicated the improved corrosion behavior of the welded specimen NZ with a decrease in the heat input during the welding process unlike the copper and brass metals.Furthermore,an increased heat input during the welding process shows a reduction in the conditions for forming the passive films with higher protection behavior.展开更多
In this paper, the eigen function expansions of displacements and stresses of bi-metal laminates with interface cracks are obtained. Furthermore, the stress intensity factors are determined by the variational method t...In this paper, the eigen function expansions of displacements and stresses of bi-metal laminates with interface cracks are obtained. Furthermore, the stress intensity factors are determined by the variational method to satisfy the boundary conditions and there are only line integrals in the variational equations due to the previous satisfaction of all basic equations. The computations show that this method of solution has the advantages of rapid convergency and time-saving. The results obtained by this method for homogeneous material agree with the known ones very well.展开更多
Based on the time differences of arrival(TDOA) and frequency differences of arrival(FDOA) measurements of the given planar stationary radiation source, the joint TDOA/FDOA location algorithm which solves the location ...Based on the time differences of arrival(TDOA) and frequency differences of arrival(FDOA) measurements of the given planar stationary radiation source, the joint TDOA/FDOA location algorithm which solves the location of the target directly is proposed. Compared with weighted least squares(WLS) methods,the proposed algorithm is also suitable for well-posed conditions,and gets rid of the dependence on the constraints of Earth's surface. First of all, the solution formulas are expressed by the radial range. Then substitute it into the equation of the radial range to figure out the radial range between the target and the reference station. Finally use the solution expression of the target location to estimate the location of the target accurately. The proposed algorithm solves the problem that WLS methods have a large positioning error when the number of observation stations is not over-determined. Simulation results show the effectiveness of the proposed algorithm, including effectively increasing the positioning accuracy and reducing the number of observatories.展开更多
A numerical scheme for the nonlinear behavior of structure under wind excitation is investigated. With the white noise filter of turbulent-wind fluctuations, the nonlinear motion equation of structures subjected to wi...A numerical scheme for the nonlinear behavior of structure under wind excitation is investigated. With the white noise filter of turbulent-wind fluctuations, the nonlinear motion equation of structures subjected to wind load was modeled as the Ito＇ s stochastic differential equation. The state vector associated with such a model is a diffusion process. A continuous linearization strategy in the time-domain was adopted. Based on the solution series of its stochastic linearization equations, the formal probabilistic density of the structure response was developed by the path integral technique. It is shown by the numerical example of a guyed mast that compared with the frequency-domain method and the time-domain nonlinear analysis, the proposed approach is highlighted by high accuracy and effectiveness. The influence of the structure non-linearity on the dynamic reliability assessment is also analyzed in the example.展开更多
Waterproof performance of gaskets between segments is the focus of shield tunnels.This paper proposed an analytical method for determining seepage characteristics at tunnel-gasketed joints based on the hydraulic fract...Waterproof performance of gaskets between segments is the focus of shield tunnels.This paper proposed an analytical method for determining seepage characteristics at tunnel-gasketed joints based on the hydraulic fracturing theories.First,the mathematical model was established,and the seepage governing equation and boundary conditions were obtained.Second,three dimensionless parameters were introduced for simplifying the expressions,and the seepage governing equations were normalized.Third,analytical expressions were derived for the interface opening and liquid pressure.Moreover,the influencing factors of seepage process at the gasketed interface were analyzed.Parametric analyses revealed that,in the normalized criterion of liquid viscosity,the liquid tip coordinate was influenced by the degree of negative pressure in the liquid lag region,which was related to the initial contact stress.The coordinate of the liquid tip affected the liquid pressure distribution and the interface opening,which were analyzed under different liquid tip coordinate conditions.Finally,under two limit states,comparative analysis showed that the results of the variation trend of the proposed method agree well with those of previous research.Overall,the proposed analytical method provides a novel solution for the design of the waterproof in shield tunnels.展开更多
For the joint time difference of arrival（TDOA） and angle of arrival（AOA） location scene,two methods are proposed based on the rectangular coordinates and the polar coordinates,respectively.The problem is solved pe...For the joint time difference of arrival（TDOA） and angle of arrival（AOA） location scene,two methods are proposed based on the rectangular coordinates and the polar coordinates,respectively.The problem is solved perfectly by calculating the target position with the joint TDOA and AOA location.On the condition of rectangular coordinates,first of all,it figures out the radial range between target and reference stations,then calculates the location of the target.In the case of polar coordinates,first of all,it figures out the azimuth between target and reference stations,then figures out the radial range between target and reference stations,finally obtains the location of the target.Simultaneously,simulation analyses show that the theoretical analysis is correct,and the proposed methods also provide the application of the joint TDOA and AOA location algorithm with the theoretical basis.展开更多
A new analytical study on stresses around a post-tensioned anchor in rocks with two perpendicular joint sets is presented. The assumptions of orthotropic elastic rock with plane strain conditions are made in derivatio...A new analytical study on stresses around a post-tensioned anchor in rocks with two perpendicular joint sets is presented. The assumptions of orthotropic elastic rock with plane strain conditions are made in derivation of the formulations. A tri-linear bond-slip constitutive law is used for modeling the tendon-grout interface behavior and debonding of this interface. The bearing plate width is also considered in the analysis. The obtained solutions are in the integral forms and numerical techniques that have been used for evaluation. In the illustrative example given, the major principal stress is compressive in the anchor free zone and compressive stress concentrations of 815 k Pa and 727 k Pa(for the anchor load of 300 k N) are observed under the bearing plate and the bond length proximal end, respectively. However, large values of tensile stresses with the maximum of-434 k Pa are formed at the bond length distal end. The results obtained using the proposed solution are compared very those of numerical method(FEM).展开更多
TiAl intermetallic could be used to replace Ni-based alloy in assemblies to generate excellent specific strength.A(Ti,Zr)-Ni-based amorphous filler metal Ti_(21.25)Zr_(25)Ni_(25)Cu_(18.75)(at.%)was designed using a cl...TiAl intermetallic could be used to replace Ni-based alloy in assemblies to generate excellent specific strength.A(Ti,Zr)-Ni-based amorphous filler metal Ti_(21.25)Zr_(25)Ni_(25)Cu_(18.75)(at.%)was designed using a cluster-plus-glue-atom model to successfully vacuum braze K4169 and TiAl bimetallic assemblies.At various brazing temperatures and holding time,the quantitative relationships between lattice distortion,grain boundary,dislocation density,and hardness,elastic modulus,shear strength of the joints were investigated.Meanwhile,the fracture mechanism of the joints was revealed.The brazed seam mainly consisted of solid diffusion reaction layers(ZonesⅠandⅢ)and filler metal residue zone(ZoneⅡ).When the brazing temperature increased to 1030℃,grain refinement occurred in the brazed seam.ZoneⅠwas primarily composed of(Ni)ss[0-11]+TiNi[011]/(Cr,Fe,Ni)ss[0-11]/(Ti,Zr)Ni[0-1-1]+(Cr,Fe,Ni)ss[0-11].The(Ti,Zr)(Ni,Cu)[001]and(Ti,Zr)(Ni,Cu)[101]intermetallic compound-based solid solutions were formed in ZoneⅡ.And the lattice distortion of(Ti,Zr)(Ni,Cu)[101]and(Ti,Zr)(Ni,Cu)[001]was 32.05%and 14.82%,respectively.As a result,the proportion of low angle grain boundaries(LAGBs)and deformed grains in ZoneⅡrose to 38.6%and 38.7%.In ZonesⅠandⅢ,the proportion of LAGBs reduced to 8%and 3.4%,respectively.As the holding time increased,the long-range diffusion of Al in ZoneⅡcaused the(Ti,Zr)(Ni,Cu)[001]with cubic structure to transform into(Ti,Zr)(Ni,Cu,Al)[00-1]with hexagonal crystal system structure,where the lattice distortion was 4.42%and 10.49%for a and c.At 1030℃/10 min,the average geometrically nec-essary dislocation densities(GNDs)in ZonesⅠ,ⅡandⅢwere 9.87×10^(14)m^(-2),8.55×10^(14)m^(-2)and 11.4×10^(14)m^(-2),respectively.Therefore,the shear strength of joints reached 322 MPa due to the lattice distortion,dislocation strengthening and fine grain strengthening.Meanwhile,the plastic and brittle hard phases were generated in ZoneⅡand displayed a mechanical interlocking structure that contributed to the performance of the joint.Both(Ti,Zr)(Ni,Cu)[001]and(Ti,Zr)(Ni,Cu)[101]in ZoneⅡformed along differ-ent low-index cleavage planes during transgranular fracture.The cracks initiated in this region extended to the interface between Zones I andⅡand exhibited bimodal grain characteristics.展开更多
药物不良事件信息往往以非结构化自由文本的形式分散于多元数据源中,其语义表达具有高维稀疏性,难以捕捉其跨模态语义关联,导致关键信息提取的精确率失衡,进而影响不良事件监测预警的准确性。研究提出基于知识图谱与自然语言处理(Natura...药物不良事件信息往往以非结构化自由文本的形式分散于多元数据源中,其语义表达具有高维稀疏性,难以捕捉其跨模态语义关联,导致关键信息提取的精确率失衡,进而影响不良事件监测预警的准确性。研究提出基于知识图谱与自然语言处理(Natural Language Processing,NLP)的药物不良事件监测预警方法。方法采用MEARank模型,整合NLP工具、预训练语言模型及定制化算法,通过关联性评分与位置正则化算法实现病程记录中药物、症状等关键词的精准提取。提取的关键词与结构化医学知识库中的不良事件报告相结合,构建药物不良事件知识图谱,并利用TransE模型进行知识图谱嵌入,获得实体和关系的低维向量表示。基于医疗专家经验构建的贝叶斯网络模型将知识图谱中的实体与关系转化为联合概率求解问题,实现药物不良事件风险等级的动态评估与预警。实验表明:上述方法构建的知识图谱平均倒数排名(MRR)达到0.9,TransE模型仅需40次迭代即可收敛,能够实现风险等级的精细化评估与准确预警,为临床用药安全提供可靠的技术支持。展开更多
考虑到铝合金自冲铆接头裂纹对静力学特性的影响,采用退火处理工艺对2024铝合金基板先进行热处理再铆接,并用固溶处理和时效处理工艺对多组2024铝合金和6061铝合金自冲铆试件进行热处理,结合拉伸试验和扫描电子显微镜(scanning electron...考虑到铝合金自冲铆接头裂纹对静力学特性的影响,采用退火处理工艺对2024铝合金基板先进行热处理再铆接,并用固溶处理和时效处理工艺对多组2024铝合金和6061铝合金自冲铆试件进行热处理,结合拉伸试验和扫描电子显微镜(scanning electron microscopy,SEM)表征不同热处理工艺后的接头裂纹和力学性能,并探究失效形式演变机制.结果表明,2024铝合金基板进行退火处理后再铆接能有效改善接头底部裂纹.固溶+人工时效处理使接头载荷显著提高23.97%,固溶+自然时效处理使接头载荷显著提高20.29%,可作为提高接头载荷的热处理工艺.受不同热处理工艺影响,6061铝合金接头失效形式从上板断裂转变为上板断裂+铆钉部分拉脱,再到上板断裂+铆钉全部拉脱,2024铝合金接头失效形式由上板断裂向上板断裂+铆钉部分拉脱转变,从单一失效形式变为混合失效形式分散了应力,延缓了裂纹扩展,提高了安全性.断裂机制由韧性断裂或脆性断裂到韧-脆混合断裂,固溶+时效处理使接头兼具一定的韧性和强度,具有广泛的适应性.展开更多
随着可再生能源渗透率持续提升及可调机组容量增加,其参与电力市场竞价交易正在逐步成为重要趋势。为深入分析区域电力市场中新能源发电商(renewable energy generators,REG)与传统发电商(conventional power generators,CPG)之间的竞...随着可再生能源渗透率持续提升及可调机组容量增加,其参与电力市场竞价交易正在逐步成为重要趋势。为深入分析区域电力市场中新能源发电商(renewable energy generators,REG)与传统发电商(conventional power generators,CPG)之间的竞争博弈行为,提出了一种多领导者-单跟随者(multiple leadersone follower,MLOF)纳什-斯塔克尔伯格(nash-stackelberg,NS)博弈模型。上层基于绿证交易机制构建了新能源与传统发电商联合参与电能量及辅助服务市场的投标报价策略模型,下层为电力-备用-平衡联合市场出清模型,确定市场出清结果及价格信号。在此基础上,基于高效分布式算法对复杂博弈模型进行求解,以提升计算效率并保护各方数据隐私。仿真分析表明,所提模型能够有效提升新能源发电商的市场收益,增强其在多主体竞争中的博弈能力。展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.52275314 and 52075074).
文摘Ni/TiAl composite brazed joints could significantly reduce the aircraft’s weight.However,low interfacial adhesion,coarse and brittle-hard intermetallic compounds(IMCs)seriously limited the application of Ni/TiAl composite joints in the next generation of aerospace applications.So enhanced K4169/TiAl composite joints were investigated by vacuum brazed with(Ni_(53.33)Cr_(20)B_(16.67)Si_(10)/Zr_(25)Ti_(18.75)Ta_(12.5)Ni_(25)Cu_(18.75))composite filler metal(CFM)designed based on cluster-plus-glue-atom model.The shear strength of the joint reached 485 MPa,comparable to the 491 MPa of TiAl substrate.The flat and brittle-hard diffusion reaction layer between Zones I and II was eliminated,simultaneously generating CrB4 dispersion strengthening due to the CFM developed with the interfacial solid-liquid space-time hysteresis effect.In Zones II and III,IMCs all transformed into Niss(Cr,Fe)_([0–88]),Niss(Ti,Al)_([004]),and Niss(Zr,Si)_([11–2])of circular and oval shapes through isothermal solidification.Meanwhile,the residual stresses and hardness were distributed in reticulated cladding characteristics.Thereby,lattice distortion led to solid solution strengthening and increased plastic toughness through crack termination and bridging mechanisms,which inhibited dislocations from plugging and crack propagation.Various interfaces in ZoneⅣwere regulated into semi-and coherent interfaces.Ni3(Ti,Al)/(Ni,Ti,Al)and(Ni,Ti,Al)/AlNi_(2)Ti were composed of higher interfacial bonding energy(2.771 J/m^(2),2.547 J/m^(2))and Ni-Ni covalent bonds.Interfacial covalent bonding and large interfacial bonding energy coupling strengthened Zone IV.Consequently,cracks initiated at the(Ni,Ti,Al)[013]/Ti3Al_([010])and expanded rapidly into TiAl substrate.Therefore,applying this method to design CFMs and regulate the phase,grain morphology,and interface’s fine structure could provide new pathways for dissimilar hard-to-join metals.
文摘This study was done to evaluate the nugget zone(NZ)corrosion behavior of dissimilar copper/brass joints welded by friction stir lap welding(FSLW)in a solution of 0.015 mol/L borax(pH 9.3).To this end,dissimilar copper/brass plates were welded with two dissimilar heat inputs(low and high)during the welding procedure.The high and low heat inputs were conducted with 710 r/min,16 mm/min and 450 r/min,25 mm/min,respectively.Using open circuit potential(OCP)measurements,electrochemical impedance spectroscopy(EIS)and Tafel polarization tests,the electrochemical behavior of the specimens in borate buffer solution was assessed.With the help of scanning electron microscope(SEM),the morphology of welded specimen surfaces was examined after immersion in the test solution.According to the results,the NZ grain size and resistance improvement reduced due to the nugget zone corrosion with a decreased heat input.The results obtained from Tafel polarization and EIS indicated the improved corrosion behavior of the welded specimen NZ with a decrease in the heat input during the welding process unlike the copper and brass metals.Furthermore,an increased heat input during the welding process shows a reduction in the conditions for forming the passive films with higher protection behavior.
文摘In this paper, the eigen function expansions of displacements and stresses of bi-metal laminates with interface cracks are obtained. Furthermore, the stress intensity factors are determined by the variational method to satisfy the boundary conditions and there are only line integrals in the variational equations due to the previous satisfaction of all basic equations. The computations show that this method of solution has the advantages of rapid convergency and time-saving. The results obtained by this method for homogeneous material agree with the known ones very well.
基金supported by the National Natural Science Foundation of China(6140236561271300)the 13th Five-Year Weaponry PreResearch Project。
文摘Based on the time differences of arrival(TDOA) and frequency differences of arrival(FDOA) measurements of the given planar stationary radiation source, the joint TDOA/FDOA location algorithm which solves the location of the target directly is proposed. Compared with weighted least squares(WLS) methods,the proposed algorithm is also suitable for well-posed conditions,and gets rid of the dependence on the constraints of Earth's surface. First of all, the solution formulas are expressed by the radial range. Then substitute it into the equation of the radial range to figure out the radial range between the target and the reference station. Finally use the solution expression of the target location to estimate the location of the target accurately. The proposed algorithm solves the problem that WLS methods have a large positioning error when the number of observation stations is not over-determined. Simulation results show the effectiveness of the proposed algorithm, including effectively increasing the positioning accuracy and reducing the number of observatories.
文摘A numerical scheme for the nonlinear behavior of structure under wind excitation is investigated. With the white noise filter of turbulent-wind fluctuations, the nonlinear motion equation of structures subjected to wind load was modeled as the Ito＇ s stochastic differential equation. The state vector associated with such a model is a diffusion process. A continuous linearization strategy in the time-domain was adopted. Based on the solution series of its stochastic linearization equations, the formal probabilistic density of the structure response was developed by the path integral technique. It is shown by the numerical example of a guyed mast that compared with the frequency-domain method and the time-domain nonlinear analysis, the proposed approach is highlighted by high accuracy and effectiveness. The influence of the structure non-linearity on the dynamic reliability assessment is also analyzed in the example.
基金Project(52278421)supported by the National Natural Science Foundation of ChinaProject(2024ZZTS0754)supported by the Fundamental Research Funds for the Central Universities of Central South University,China+2 种基金Project(2023CXQD067)supported by the Central South University Innovation-Driven Research Programme,ChinaProject(2022QNRC001)supported by Young Elite Scientists Sponsorship Program by CASTProject(2023TJ-N24)supported by the Youth Talent Program by China Railway Society and the Hunan Provincial Science and Technology Promotion Talent Project。
文摘Waterproof performance of gaskets between segments is the focus of shield tunnels.This paper proposed an analytical method for determining seepage characteristics at tunnel-gasketed joints based on the hydraulic fracturing theories.First,the mathematical model was established,and the seepage governing equation and boundary conditions were obtained.Second,three dimensionless parameters were introduced for simplifying the expressions,and the seepage governing equations were normalized.Third,analytical expressions were derived for the interface opening and liquid pressure.Moreover,the influencing factors of seepage process at the gasketed interface were analyzed.Parametric analyses revealed that,in the normalized criterion of liquid viscosity,the liquid tip coordinate was influenced by the degree of negative pressure in the liquid lag region,which was related to the initial contact stress.The coordinate of the liquid tip affected the liquid pressure distribution and the interface opening,which were analyzed under different liquid tip coordinate conditions.Finally,under two limit states,comparative analysis showed that the results of the variation trend of the proposed method agree well with those of previous research.Overall,the proposed analytical method provides a novel solution for the design of the waterproof in shield tunnels.
基金supported by the National Natural Science Foundation of China(6107210761271300)+4 种基金the Shaanxi Industry Surmount Foundation(2012K06-12)the Arm and Equipment Pre-research Foundationthe Fundamental Research Funds for the Central Universities of China(K0551302006K5051202045K50511020024)
文摘For the joint time difference of arrival（TDOA） and angle of arrival（AOA） location scene,two methods are proposed based on the rectangular coordinates and the polar coordinates,respectively.The problem is solved perfectly by calculating the target position with the joint TDOA and AOA location.On the condition of rectangular coordinates,first of all,it figures out the radial range between target and reference stations,then calculates the location of the target.In the case of polar coordinates,first of all,it figures out the azimuth between target and reference stations,then figures out the radial range between target and reference stations,finally obtains the location of the target.Simultaneously,simulation analyses show that the theoretical analysis is correct,and the proposed methods also provide the application of the joint TDOA and AOA location algorithm with the theoretical basis.
文摘A new analytical study on stresses around a post-tensioned anchor in rocks with two perpendicular joint sets is presented. The assumptions of orthotropic elastic rock with plane strain conditions are made in derivation of the formulations. A tri-linear bond-slip constitutive law is used for modeling the tendon-grout interface behavior and debonding of this interface. The bearing plate width is also considered in the analysis. The obtained solutions are in the integral forms and numerical techniques that have been used for evaluation. In the illustrative example given, the major principal stress is compressive in the anchor free zone and compressive stress concentrations of 815 k Pa and 727 k Pa(for the anchor load of 300 k N) are observed under the bearing plate and the bond length proximal end, respectively. However, large values of tensile stresses with the maximum of-434 k Pa are formed at the bond length distal end. The results obtained using the proposed solution are compared very those of numerical method(FEM).
基金supported by the National Natural Science Foundation of China(Nos.52275314 and 52075074).
文摘TiAl intermetallic could be used to replace Ni-based alloy in assemblies to generate excellent specific strength.A(Ti,Zr)-Ni-based amorphous filler metal Ti_(21.25)Zr_(25)Ni_(25)Cu_(18.75)(at.%)was designed using a cluster-plus-glue-atom model to successfully vacuum braze K4169 and TiAl bimetallic assemblies.At various brazing temperatures and holding time,the quantitative relationships between lattice distortion,grain boundary,dislocation density,and hardness,elastic modulus,shear strength of the joints were investigated.Meanwhile,the fracture mechanism of the joints was revealed.The brazed seam mainly consisted of solid diffusion reaction layers(ZonesⅠandⅢ)and filler metal residue zone(ZoneⅡ).When the brazing temperature increased to 1030℃,grain refinement occurred in the brazed seam.ZoneⅠwas primarily composed of(Ni)ss[0-11]+TiNi[011]/(Cr,Fe,Ni)ss[0-11]/(Ti,Zr)Ni[0-1-1]+(Cr,Fe,Ni)ss[0-11].The(Ti,Zr)(Ni,Cu)[001]and(Ti,Zr)(Ni,Cu)[101]intermetallic compound-based solid solutions were formed in ZoneⅡ.And the lattice distortion of(Ti,Zr)(Ni,Cu)[101]and(Ti,Zr)(Ni,Cu)[001]was 32.05%and 14.82%,respectively.As a result,the proportion of low angle grain boundaries(LAGBs)and deformed grains in ZoneⅡrose to 38.6%and 38.7%.In ZonesⅠandⅢ,the proportion of LAGBs reduced to 8%and 3.4%,respectively.As the holding time increased,the long-range diffusion of Al in ZoneⅡcaused the(Ti,Zr)(Ni,Cu)[001]with cubic structure to transform into(Ti,Zr)(Ni,Cu,Al)[00-1]with hexagonal crystal system structure,where the lattice distortion was 4.42%and 10.49%for a and c.At 1030℃/10 min,the average geometrically nec-essary dislocation densities(GNDs)in ZonesⅠ,ⅡandⅢwere 9.87×10^(14)m^(-2),8.55×10^(14)m^(-2)and 11.4×10^(14)m^(-2),respectively.Therefore,the shear strength of joints reached 322 MPa due to the lattice distortion,dislocation strengthening and fine grain strengthening.Meanwhile,the plastic and brittle hard phases were generated in ZoneⅡand displayed a mechanical interlocking structure that contributed to the performance of the joint.Both(Ti,Zr)(Ni,Cu)[001]and(Ti,Zr)(Ni,Cu)[101]in ZoneⅡformed along differ-ent low-index cleavage planes during transgranular fracture.The cracks initiated in this region extended to the interface between Zones I andⅡand exhibited bimodal grain characteristics.
文摘药物不良事件信息往往以非结构化自由文本的形式分散于多元数据源中,其语义表达具有高维稀疏性,难以捕捉其跨模态语义关联,导致关键信息提取的精确率失衡,进而影响不良事件监测预警的准确性。研究提出基于知识图谱与自然语言处理(Natural Language Processing,NLP)的药物不良事件监测预警方法。方法采用MEARank模型,整合NLP工具、预训练语言模型及定制化算法,通过关联性评分与位置正则化算法实现病程记录中药物、症状等关键词的精准提取。提取的关键词与结构化医学知识库中的不良事件报告相结合,构建药物不良事件知识图谱,并利用TransE模型进行知识图谱嵌入,获得实体和关系的低维向量表示。基于医疗专家经验构建的贝叶斯网络模型将知识图谱中的实体与关系转化为联合概率求解问题,实现药物不良事件风险等级的动态评估与预警。实验表明:上述方法构建的知识图谱平均倒数排名(MRR)达到0.9,TransE模型仅需40次迭代即可收敛,能够实现风险等级的精细化评估与准确预警,为临床用药安全提供可靠的技术支持。
文摘考虑到铝合金自冲铆接头裂纹对静力学特性的影响,采用退火处理工艺对2024铝合金基板先进行热处理再铆接,并用固溶处理和时效处理工艺对多组2024铝合金和6061铝合金自冲铆试件进行热处理,结合拉伸试验和扫描电子显微镜(scanning electron microscopy,SEM)表征不同热处理工艺后的接头裂纹和力学性能,并探究失效形式演变机制.结果表明,2024铝合金基板进行退火处理后再铆接能有效改善接头底部裂纹.固溶+人工时效处理使接头载荷显著提高23.97%,固溶+自然时效处理使接头载荷显著提高20.29%,可作为提高接头载荷的热处理工艺.受不同热处理工艺影响,6061铝合金接头失效形式从上板断裂转变为上板断裂+铆钉部分拉脱,再到上板断裂+铆钉全部拉脱,2024铝合金接头失效形式由上板断裂向上板断裂+铆钉部分拉脱转变,从单一失效形式变为混合失效形式分散了应力,延缓了裂纹扩展,提高了安全性.断裂机制由韧性断裂或脆性断裂到韧-脆混合断裂,固溶+时效处理使接头兼具一定的韧性和强度,具有广泛的适应性.
文摘随着可再生能源渗透率持续提升及可调机组容量增加,其参与电力市场竞价交易正在逐步成为重要趋势。为深入分析区域电力市场中新能源发电商(renewable energy generators,REG)与传统发电商(conventional power generators,CPG)之间的竞争博弈行为,提出了一种多领导者-单跟随者(multiple leadersone follower,MLOF)纳什-斯塔克尔伯格(nash-stackelberg,NS)博弈模型。上层基于绿证交易机制构建了新能源与传统发电商联合参与电能量及辅助服务市场的投标报价策略模型,下层为电力-备用-平衡联合市场出清模型,确定市场出清结果及价格信号。在此基础上,基于高效分布式算法对复杂博弈模型进行求解,以提升计算效率并保护各方数据隐私。仿真分析表明,所提模型能够有效提升新能源发电商的市场收益,增强其在多主体竞争中的博弈能力。
