Increasing global concern about the environment is bringing regulatory （European directives） and consumer （＂green products＂） pressure on the electronics industry in Europe and Japan to reduce or completely elimi...Increasing global concern about the environment is bringing regulatory （European directives） and consumer （＂green products＂） pressure on the electronics industry in Europe and Japan to reduce or completely eliminate the use of lead （Pb） in products. Among all lead-free solder alloys, SnAgCu solder system, which has better thermo-mechanical properties compared with those of SnPb solder, is proven to be one of the promising candidates for electronic assembly. Previous work also revealed that adding a small amount of rare earth Ce into SnAgCu solder can visibly improve the properties and inhibit the excessive growth of the intermetallic compound layer. Thermal fatigue properties of SnAgCuCe soldered joints in QFP devices under thermal conditions have been investigated by finite element method and experiments. Based on creep model of low stress and high stress, corresponding creep subroutine was established for simulating the stress and strain response of SnAgCuCe soldered joint from -55 ℃ to 125 ℃, and fatigue life was calculated using creep fatigue life prediction equation. Moreover, thermal cycling experiments were conducted, the experimental results were found to be close to the simulated results. In addition, the tensile force of SnAgCuCe soldered joints decreased with increasing number of thermal cycles, and the fracture mechanism transformed from toughness fracture to brittle intergranular fracture. Moreover the tensile force changes and fracture microstructure evolution could benefit the quantitative evaluations of the mechanical performances of lead-free soldered joints under thermal cycling loadings.展开更多
SnAgCu solder system with the addition of rare earth Ce, which has better thermo-mechanical properties compared to those of SnPb solder, is regarded as one of the promising candidates for electronic assembly. Moreover...SnAgCu solder system with the addition of rare earth Ce, which has better thermo-mechanical properties compared to those of SnPb solder, is regarded as one of the promising candidates for electronic assembly. Moreover, the SnAgCuCe solder alloys can provide good quality joints with Cu substrates. However, there is few report of the constitutive model for SnAgCu solder bearing micro-amounts rare earth Ce. In this paper, the unified viscoplastic constitutive model, Anand equations, is used to represent the inelastic deformation behavior for SnAgCu and SnAgCuCe solders. In order to obtain the acquired data for the fitting of the material parameters of this unified model, a series of experiments of constant strain rate test were conducted under isothermal conditions at different temperatures. The Anand parameters of the constitutive equations for SnAgCu and SnAgCuCe solder were determined from separated constitutive relations and experimental results. Nonlinear least-square fitting was selected to determine the model constants. And the simulated results were then compared with experimental measurements of the stress-inelastic strain curves： excellent agreement was found. The model accurately predicted the overall trend of steady-state stress-strain behavior of SnAgCu and SnAgCuCe solders for the temperature ranges from 25℃ to 150 ℃, and the strain rate ranges from 0.01 s^-1 to 0.001 s ^-1. It is concluded that the Anand model can be applied for representing the inelastic deformation behavior of solders at high homologous temperature and can be recommended for finite element simulation of the stress-strain response of lead free soldered joints. Based on the Anand model, the investigations of thermo-mechanical of SnAgCu and SnAgCuCe soldered joints in fine pitch quad flat package by finite element code were done under thermal cyclic loading, it is found that the reliability of SnAgCu soldered joints can be improved remarkably with addition of rare earth Ce. The results may provide a theory guide for developing constitutive model for lead-free solders.展开更多
The Chinese-German Journal of Clinical Oncology is aninternational professional academiic periodical on on-cology,being co-edited by China and Germany.The Journal,with the authors from around world,especially from Chi...The Chinese-German Journal of Clinical Oncology is aninternational professional academiic periodical on on-cology,being co-edited by China and Germany.The Journal,with the authors from around world,especially from China,isdominated in introducing the clinical experience of diagnosisand treatment as well as leading scientific research achieve-ment in the tumor domain,in addition to report basic theoryresearches which help instruct the clinical practice of oncolo-gy and closely connect with the discipline.All the manu-scripts are published in English,quarterly issued both inter-nal and external,64-80 pages,big 16 opens domains,artpaper in offset printing,with lay-out by international cus-toms,unified issuing number:ISSN 0178-3351/CN/42-1654/R.展开更多
In view of the low interpretability of existing collaborative filtering recommendation algorithms and the difficulty of extracting information from content-based recommendation algorithms,we propose an efficient KGRS ...In view of the low interpretability of existing collaborative filtering recommendation algorithms and the difficulty of extracting information from content-based recommendation algorithms,we propose an efficient KGRS model.KGRS first obtains reasoning paths of knowledge graph and embeds the entities of paths into vectors based on knowledge representation learning TransD algorithm,then uses LSTM and soft attention mechanism to capture the semantic of each path reasoning,then uses convolution operation and pooling operation to distinguish the importance of different paths reasoning.Finally,through the full connection layer and sigmoid function to get the prediction ratings,and the items are sorted according to the prediction ratings to get the user’s recommendation list.KGRS is tested on the movielens-100k dataset.Compared with the related representative algorithm,including the state-of-the-art interpretable recommendation models RKGE and RippleNet,the experimental results show that KGRS has good recommendation interpretation and higher recommendation accuracy.展开更多
The Chinese-German Journal of Clinical Oncology isan international, professional, academic periodical on on-cology, co-edited by China and Germany. With the au-thors from around the world, especially from China, thejo...The Chinese-German Journal of Clinical Oncology isan international, professional, academic periodical on on-cology, co-edited by China and Germany. With the au-thors from around the world, especially from China, thejournal focuses on introducing clinical experience in diag-nosis and treatment and leading scientific research a-chievement in the tumor domain, in addition to reportingbasic theory research which help to teach the clinicalpractice of oncology and closely connect with the disci-pline. All manuscripts are published in English: the jour-nal is issued quarterly, with the International SerialStandard Number (ISSN) 1610-1979/CN/42-1654/R.展开更多
Extension multi-factorial evaluation method was used in water quality early-earning in Yincungang River based on MATLAB. The results showed that water quality in summer was safe,while that in other three seasons were ...Extension multi-factorial evaluation method was used in water quality early-earning in Yincungang River based on MATLAB. The results showed that water quality in summer was safe,while that in other three seasons were in pre-warning state with the order of winter > spring > autumn.展开更多
According to the characteristics of longan cultivated in the hill and mountain regions of Maoming City,this paper analyzed the economic benefit of the simplified cultivation techniques. With 15-year-old Chuliang longa...According to the characteristics of longan cultivated in the hill and mountain regions of Maoming City,this paper analyzed the economic benefit of the simplified cultivation techniques. With 15-year-old Chuliang longan trees as materials,the economic benefit of four kinds of simplified cultivation technologies was compared and analyzed. After nine years of continuous technological application,it was found that the input costs increased by 1. 62%,and the output profits increased by 56. 10%; in input costs,labor cost decreased by 41. 33%,pesticide cost decreased by 24. 19%,and fertilizer cost increased by 33. 57%.展开更多
This study investigated the characteristics of corrosion products formed on the contact and exposed re-gions of C1045 steel bolt and nut fasteners exposed to aqueous chloride environments.The corroded sur-face morphol...This study investigated the characteristics of corrosion products formed on the contact and exposed re-gions of C1045 steel bolt and nut fasteners exposed to aqueous chloride environments.The corroded sur-face morphology,rust compositions,and corrosion kinetics of the bolt specimen were studied by visual observation,optical microscopy(OM),scanning electron microscopy(SEM),X-Ray diffractometry(XRD),micro-Raman,electron probe micro-analyser(EPMA),and potentiodynamic polarization techniques.Re-sults obtained showed a variation in corrosion kinetics,morphology,and composition of the rust layer which were driven by differential aeration and concentration effects.Due to the availability of sufficient dissolved oxygen,the oxyhydroxide compound,lepidocrocite(γ-FeOOH)was detected in the outer rust layer in the exposed region,whereas the inner rust layer was composed of magnetite(Fe_(3)O_(4)).How-ever,the oxygen-deficient contact surface revealed the presence of akaganeite(β-FeOOH)and magnetite(Fe_(3)O_(4))as dominant oxide phases.The most stable phase,goethite(α-FeOOH)was also detected in the rust formed in both regions,though in significantly low amounts.Furthermore,owing to variation in environmental conditions,the amount and density of the rust layer varied in the different regions.The estimated corrosion stability values for the different regions revealed that the corrosion products formed on the steel surfaces were non-protective,suggesting the need for specific surface treatment as a protec-tive measure.展开更多
The paper analyzes and compares the phase margins of four active disturbance rejection control(ADRC)designs,which are based on different common-used extended state observers(ESOs)of various orders,for second-order sys...The paper analyzes and compares the phase margins of four active disturbance rejection control(ADRC)designs,which are based on different common-used extended state observers(ESOs)of various orders,for second-order systems.The quantitative results indicate that,besides good dynamic response,ADRC can guarantee enough phase margin.It is also proved that by decreasing the order of ESO,the phase margin can be increased.Furthermore,it is demonstrated that the phase margins of the ADRC-based systems can be almost uninfluenced by the uncertainties of the system parameters.Finally,the theoretical results are verified by both simulations and experiments on a motion control platform.展开更多
A new study provides a comprehensive molecular mechanism that controls interspecific incompatibility of self-incompatible(SI)plants in the Brassicaceae.This finding points to a potentially promising path to break inte...A new study provides a comprehensive molecular mechanism that controls interspecific incompatibility of self-incompatible(SI)plants in the Brassicaceae.This finding points to a potentially promising path to break interspecific barriers and achieve introgression of desirable traits into crops from distant species among SI crops in the Brassicaceae.展开更多
In plants,the stigma represents the initial site of pollenpistil communication and serves as a crucial location for rejection of incompatible pollen.In self-compatible(SC)plants,such as Arabidopsis thaliana from the B...In plants,the stigma represents the initial site of pollenpistil communication and serves as a crucial location for rejection of incompatible pollen.In self-compatible(SC)plants,such as Arabidopsis thaliana from the Brassicaceae family,pollen coat protein B(PCP-B)peptides were reported to compete with stigmatic RAPID ALKALINIZATION FACTOR 33(RALF33)peptides for binding to the FERONIA/ANJEA(FER/ANJ)receptors in the stigma to promote pollen hydration via inhibition of reactive oxygen species(ROS)production(Liu et al.2021).展开更多
In flowering plants,the two sperm cells are passive cargo transported into the ovule by pollen tubes (Zhang et al.,2017).Therefore,the precise guidance of pollen tubes is critical for successful double fertilization (...In flowering plants,the two sperm cells are passive cargo transported into the ovule by pollen tubes (Zhang et al.,2017).Therefore,the precise guidance of pollen tubes is critical for successful double fertilization (Dresselhaus and Franklin-Tong,2013).A series of male-female interactions are required to guarantee the spatiotemporal regulation of pollen tube guidance because during growth,pollen tubes continuously interact with different female tissues (Zhong et al.,2017;Zhong and Qu,2019).In the past two decades,there has been tremendous progress in elucidating the molecular mechanisms of pollen tube guidance regulation,mostly using Arabidopsis thaliana as a model system (Johnson et al.,2019).展开更多
In angiosperms, initiation of ovule enlargement represents the start of seed development, the molecular mechanism of which is not yet elucidated. It was previously reported that pollen tube contents, rather than doubl...In angiosperms, initiation of ovule enlargement represents the start of seed development, the molecular mechanism of which is not yet elucidated. It was previously reported that pollen tube contents, rather than double fertilization, can trigger ovule enlargement. However, it remains unclear whether the signal（s） to trigger the initiation of ovule enlargement are from the sperm cells or fromthe pollen tubes. Recently, we identified a mutant dropl- drop2-, which produces pollen tubes with no sperm cells. Taking advantage of this special genetic material, we conducted pollination assays, and found that the ovules pollinated with dropl- drop2- pollen could initiate the enlargement and exhibited significant enlarged sizes at 36h after pollination in comparison with those unpollinated ovules. However, the sizes of the ovules pollinated with drops- drop2- pollen are significantly smaller than those of the ovules pollinated with wildtype pollen. These results demonstrate that the pollen tube, rather than the sperm cells, release the signal to trigger the initiation of ovule enlargement, and that double fertilization is required for further enlargement of the seeds.展开更多
基金supported by Nanjing University of Aeronautics and Astronautics Doctoral Dissertation Innovation and Excellence Producing Foundation of China (Grant No. BCXJ09-07)Jiangsu Provincial General Colleges and Universities Postgraduate Scientific Research Innovative Plan of China (Grant No. CX09B_074Z)Jiangsu Provincial Six Kind Skilled Personnel Project of China (Grant No. 06-E-020)
文摘Increasing global concern about the environment is bringing regulatory （European directives） and consumer （＂green products＂） pressure on the electronics industry in Europe and Japan to reduce or completely eliminate the use of lead （Pb） in products. Among all lead-free solder alloys, SnAgCu solder system, which has better thermo-mechanical properties compared with those of SnPb solder, is proven to be one of the promising candidates for electronic assembly. Previous work also revealed that adding a small amount of rare earth Ce into SnAgCu solder can visibly improve the properties and inhibit the excessive growth of the intermetallic compound layer. Thermal fatigue properties of SnAgCuCe soldered joints in QFP devices under thermal conditions have been investigated by finite element method and experiments. Based on creep model of low stress and high stress, corresponding creep subroutine was established for simulating the stress and strain response of SnAgCuCe soldered joint from -55 ℃ to 125 ℃, and fatigue life was calculated using creep fatigue life prediction equation. Moreover, thermal cycling experiments were conducted, the experimental results were found to be close to the simulated results. In addition, the tensile force of SnAgCuCe soldered joints decreased with increasing number of thermal cycles, and the fracture mechanism transformed from toughness fracture to brittle intergranular fracture. Moreover the tensile force changes and fracture microstructure evolution could benefit the quantitative evaluations of the mechanical performances of lead-free soldered joints under thermal cycling loadings.
基金supported by Doctoral Dissertation Innovation and Excellence Producing Foundation of Nanjing University of Aeronautics and Astronautics,China(Grant No.BCXJ09-07)Jiangsu Provincial Six Kind Skilled Personnel Project of China(Grant No.06-E-020)Jiangsu General Colleges and Universities Postgraduate Scientific Research Innovative Plan of China(Grant No.CX09B_074Z)
文摘SnAgCu solder system with the addition of rare earth Ce, which has better thermo-mechanical properties compared to those of SnPb solder, is regarded as one of the promising candidates for electronic assembly. Moreover, the SnAgCuCe solder alloys can provide good quality joints with Cu substrates. However, there is few report of the constitutive model for SnAgCu solder bearing micro-amounts rare earth Ce. In this paper, the unified viscoplastic constitutive model, Anand equations, is used to represent the inelastic deformation behavior for SnAgCu and SnAgCuCe solders. In order to obtain the acquired data for the fitting of the material parameters of this unified model, a series of experiments of constant strain rate test were conducted under isothermal conditions at different temperatures. The Anand parameters of the constitutive equations for SnAgCu and SnAgCuCe solder were determined from separated constitutive relations and experimental results. Nonlinear least-square fitting was selected to determine the model constants. And the simulated results were then compared with experimental measurements of the stress-inelastic strain curves： excellent agreement was found. The model accurately predicted the overall trend of steady-state stress-strain behavior of SnAgCu and SnAgCuCe solders for the temperature ranges from 25℃ to 150 ℃, and the strain rate ranges from 0.01 s^-1 to 0.001 s ^-1. It is concluded that the Anand model can be applied for representing the inelastic deformation behavior of solders at high homologous temperature and can be recommended for finite element simulation of the stress-strain response of lead free soldered joints. Based on the Anand model, the investigations of thermo-mechanical of SnAgCu and SnAgCuCe soldered joints in fine pitch quad flat package by finite element code were done under thermal cyclic loading, it is found that the reliability of SnAgCu soldered joints can be improved remarkably with addition of rare earth Ce. The results may provide a theory guide for developing constitutive model for lead-free solders.
文摘The Chinese-German Journal of Clinical Oncology is aninternational professional academiic periodical on on-cology,being co-edited by China and Germany.The Journal,with the authors from around world,especially from China,isdominated in introducing the clinical experience of diagnosisand treatment as well as leading scientific research achieve-ment in the tumor domain,in addition to report basic theoryresearches which help instruct the clinical practice of oncolo-gy and closely connect with the discipline.All the manu-scripts are published in English,quarterly issued both inter-nal and external,64-80 pages,big 16 opens domains,artpaper in offset printing,with lay-out by international cus-toms,unified issuing number:ISSN 0178-3351/CN/42-1654/R.
基金supported by the National Science Foundation of China Grant No.61762092“Dynamic multi-objective requirement optimization based on transfer learning”,No.61762089+2 种基金“The key research of high order tensor decomposition in distributed environment”the Open Foundation of the Key Laboratory in Software Engineering of Yunnan Province,Grant No.2017SE204,”Research on extracting software feature models using transfer learning”.
文摘In view of the low interpretability of existing collaborative filtering recommendation algorithms and the difficulty of extracting information from content-based recommendation algorithms,we propose an efficient KGRS model.KGRS first obtains reasoning paths of knowledge graph and embeds the entities of paths into vectors based on knowledge representation learning TransD algorithm,then uses LSTM and soft attention mechanism to capture the semantic of each path reasoning,then uses convolution operation and pooling operation to distinguish the importance of different paths reasoning.Finally,through the full connection layer and sigmoid function to get the prediction ratings,and the items are sorted according to the prediction ratings to get the user’s recommendation list.KGRS is tested on the movielens-100k dataset.Compared with the related representative algorithm,including the state-of-the-art interpretable recommendation models RKGE and RippleNet,the experimental results show that KGRS has good recommendation interpretation and higher recommendation accuracy.
文摘The Chinese-German Journal of Clinical Oncology isan international, professional, academic periodical on on-cology, co-edited by China and Germany. With the au-thors from around the world, especially from China, thejournal focuses on introducing clinical experience in diag-nosis and treatment and leading scientific research a-chievement in the tumor domain, in addition to reportingbasic theory research which help to teach the clinicalpractice of oncology and closely connect with the disci-pline. All manuscripts are published in English: the jour-nal is issued quarterly, with the International SerialStandard Number (ISSN) 1610-1979/CN/42-1654/R.
基金Supported by Jiangsu Taihu Treatment Scientific Research Program(TH2010101)
文摘Extension multi-factorial evaluation method was used in water quality early-earning in Yincungang River based on MATLAB. The results showed that water quality in summer was safe,while that in other three seasons were in pre-warning state with the order of winter > spring > autumn.
基金Supported by Special Project of Modern Agricultural Industry Technology System Construction(CARS-33)Lingnan Fruit Innovation Team Project of Guangdong Provincial Modern Agricultural Industry Technology System(2016-LM1039)
文摘According to the characteristics of longan cultivated in the hill and mountain regions of Maoming City,this paper analyzed the economic benefit of the simplified cultivation techniques. With 15-year-old Chuliang longan trees as materials,the economic benefit of four kinds of simplified cultivation technologies was compared and analyzed. After nine years of continuous technological application,it was found that the input costs increased by 1. 62%,and the output profits increased by 56. 10%; in input costs,labor cost decreased by 41. 33%,pesticide cost decreased by 24. 19%,and fertilizer cost increased by 33. 57%.
基金This work was financially supported by the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2019193,KGFZD-135-19-02)the National Natural Science Foundation of China(No.51801219).Special appreciation to the CAS-TWAS Presidential Fellowship for sponsorship.
文摘This study investigated the characteristics of corrosion products formed on the contact and exposed re-gions of C1045 steel bolt and nut fasteners exposed to aqueous chloride environments.The corroded sur-face morphology,rust compositions,and corrosion kinetics of the bolt specimen were studied by visual observation,optical microscopy(OM),scanning electron microscopy(SEM),X-Ray diffractometry(XRD),micro-Raman,electron probe micro-analyser(EPMA),and potentiodynamic polarization techniques.Re-sults obtained showed a variation in corrosion kinetics,morphology,and composition of the rust layer which were driven by differential aeration and concentration effects.Due to the availability of sufficient dissolved oxygen,the oxyhydroxide compound,lepidocrocite(γ-FeOOH)was detected in the outer rust layer in the exposed region,whereas the inner rust layer was composed of magnetite(Fe_(3)O_(4)).How-ever,the oxygen-deficient contact surface revealed the presence of akaganeite(β-FeOOH)and magnetite(Fe_(3)O_(4))as dominant oxide phases.The most stable phase,goethite(α-FeOOH)was also detected in the rust formed in both regions,though in significantly low amounts.Furthermore,owing to variation in environmental conditions,the amount and density of the rust layer varied in the different regions.The estimated corrosion stability values for the different regions revealed that the corrosion products formed on the steel surfaces were non-protective,suggesting the need for specific surface treatment as a protec-tive measure.
基金This work was supported by the National Key R&D Program of China(No.2018YFA0703800)the National Natural Science Foundation of China(No.U20B2054).
文摘The paper analyzes and compares the phase margins of four active disturbance rejection control(ADRC)designs,which are based on different common-used extended state observers(ESOs)of various orders,for second-order systems.The quantitative results indicate that,besides good dynamic response,ADRC can guarantee enough phase margin.It is also proved that by decreasing the order of ESO,the phase margin can be increased.Furthermore,it is demonstrated that the phase margins of the ADRC-based systems can be almost uninfluenced by the uncertainties of the system parameters.Finally,the theoretical results are verified by both simulations and experiments on a motion control platform.
文摘A new study provides a comprehensive molecular mechanism that controls interspecific incompatibility of self-incompatible(SI)plants in the Brassicaceae.This finding points to a potentially promising path to break interspecific barriers and achieve introgression of desirable traits into crops from distant species among SI crops in the Brassicaceae.
基金Open access funding provided by Shanghai Jiao Tong Universitysupported by the National Natural Science Foundation of China(Grant No.31991202 and 31830004 to L.-J.Q.,and 32122014 to S.Z.)+1 种基金the Young Elite Scientists Sponsorship Program by China Association of Science&Technology(2019QNRC001 to S.Z.)L.-J.Q.is a New Cornerstone Investigator supported by the New Cornerstone Science Foundation.
文摘In plants,the stigma represents the initial site of pollenpistil communication and serves as a crucial location for rejection of incompatible pollen.In self-compatible(SC)plants,such as Arabidopsis thaliana from the Brassicaceae family,pollen coat protein B(PCP-B)peptides were reported to compete with stigmatic RAPID ALKALINIZATION FACTOR 33(RALF33)peptides for binding to the FERONIA/ANJEA(FER/ANJ)receptors in the stigma to promote pollen hydration via inhibition of reactive oxygen species(ROS)production(Liu et al.2021).
文摘In flowering plants,the two sperm cells are passive cargo transported into the ovule by pollen tubes (Zhang et al.,2017).Therefore,the precise guidance of pollen tubes is critical for successful double fertilization (Dresselhaus and Franklin-Tong,2013).A series of male-female interactions are required to guarantee the spatiotemporal regulation of pollen tube guidance because during growth,pollen tubes continuously interact with different female tissues (Zhong et al.,2017;Zhong and Qu,2019).In the past two decades,there has been tremendous progress in elucidating the molecular mechanisms of pollen tube guidance regulation,mostly using Arabidopsis thaliana as a model system (Johnson et al.,2019).
基金supported by National Natural Science Foundation of China(31620103903)partially by the 111 projectsupported by the Peking-Tsinghua Joint Center for Life Sciences
文摘In angiosperms, initiation of ovule enlargement represents the start of seed development, the molecular mechanism of which is not yet elucidated. It was previously reported that pollen tube contents, rather than double fertilization, can trigger ovule enlargement. However, it remains unclear whether the signal（s） to trigger the initiation of ovule enlargement are from the sperm cells or fromthe pollen tubes. Recently, we identified a mutant dropl- drop2-, which produces pollen tubes with no sperm cells. Taking advantage of this special genetic material, we conducted pollination assays, and found that the ovules pollinated with dropl- drop2- pollen could initiate the enlargement and exhibited significant enlarged sizes at 36h after pollination in comparison with those unpollinated ovules. However, the sizes of the ovules pollinated with drops- drop2- pollen are significantly smaller than those of the ovules pollinated with wildtype pollen. These results demonstrate that the pollen tube, rather than the sperm cells, release the signal to trigger the initiation of ovule enlargement, and that double fertilization is required for further enlargement of the seeds.
