尖孢镰刀菌古巴专化型(Fusarium oxysporum f. sp. cubense,Foc)依据对寄主易感性分为4个不同的生理小种,其中4号生理小种(Foc4)几乎能危害目前所有栽培品种。为研究其SIX(secreted in xylem)蛋白编码基因SIX2和SIX6在Foc4对寄主差异性...尖孢镰刀菌古巴专化型(Fusarium oxysporum f. sp. cubense,Foc)依据对寄主易感性分为4个不同的生理小种,其中4号生理小种(Foc4)几乎能危害目前所有栽培品种。为研究其SIX(secreted in xylem)蛋白编码基因SIX2和SIX6在Foc4对寄主差异性选择中的作用,利用PEG介导的原生质体转化法将基于pCT74质粒框架构建的SIX2、SIX6基因敲除质粒分别转入Foc4 B2菌株,分别得到了SIX2和SIX6基因敲除突变体,然后分析敲除突变体与野生型的生物学特性差异。生物学研究结果表明:SIX2、SIX6基因的缺失突变体均呈现菌丝稀疏、生长速率减慢、产孢率降低、菌丝异核率增加,对渗透压、外源氧等外源胁迫更为敏感等特征。致病力分析实验发现ΔFoSIX2和ΔFoSIX6突变体的孢子在香蕉苗的幼嫩根部附着量减少,孢子根部定殖能力降低;ΔFoSIX2菌株基本上丧失了对巴西蕉的致病力,而对粉蕉仍有较强的致病能力;ΔFoSIX6菌株则对粉蕉苗、巴西香蕉苗盆栽致病力均呈极显著下降。依据生物学与致病力测定结果,推测Foc4中SIX6基因决定Foc4对寄主的致病力,而SIX2基因则决定Foc4对寄主的差异性选择能力。展开更多
Lightweight design is important for the Thermal Protection System(TPS) of hypersonic vehicles in that it protects the inner structure from severe heating environment. However, due to the existence of uncertainties in ...Lightweight design is important for the Thermal Protection System(TPS) of hypersonic vehicles in that it protects the inner structure from severe heating environment. However, due to the existence of uncertainties in material properties and geometry, it is imperative to incorporate uncertainty analysis into the design optimization to obtain reliable results. In this paper, a six sigma robust design optimization based on Successive Response Surface Method(SRSM) is established for the TPS to improve the reliability and robustness with considering the uncertainties. The uncertain parameters related to material properties and thicknesses of insulation layers are considered and characterized by random variables following normal distributions. By employing SRSM, the values of objective function and constraints are approximated by the response surfaces to reduce computational cost. The optimization is an iterative process with response surfaces updating to find the true optimal solution. The optimization of the nose cone of hypersonic vehicle cabin is provided as an example to illustrate the feasibility and effectiveness of the proposed method.展开更多
A 1∶2.5 scale tundish model was set up in laboratory for a six-strand billet continuous casting tundish with different configurations to investigate fluid flow characteristics under different operational conditions b...A 1∶2.5 scale tundish model was set up in laboratory for a six-strand billet continuous casting tundish with different configurations to investigate fluid flow characteristics under different operational conditions by measuring residence time distribution curves.It was found that minimum residence time,maximum concentration time and average residence time of the three strands on the same side of the tundish with the former configuration under normal operation,that is,six strands were open,were small and non-uniform and the tundish had large dead volume fraction.Vortexes easily formed on the liquid surface in the pouring zone of the tundish.The fluid flow characteristics in the tundish with the optimal turbulence inhibitor and baffles were improved and became less non-uniform among the strands.Vortexes were not found on the pouring zone surface in the optimal tundish.For non-normal operation,that is,one strand was close,it was important to choose which strand to be closed for maintaining flow characteristics of the rest two strands.It was found from this investigation that fluid flow characteristics in the optimal configuration tundish with closing strand 2 were better than those with closing strand 3 on the same side.展开更多
Improper flow control devices in a multi-strand tundish can cause some problems, for example, liquid steel cannot reach every nozzle at the same time and the liquid steel in nozzles far away from the entry zone has a ...Improper flow control devices in a multi-strand tundish can cause some problems, for example, liquid steel cannot reach every nozzle at the same time and the liquid steel in nozzles far away from the entry zone has a lower temperature. The water model experiment of a six-strand tundish of Tianjin Iron ＆ Steel Co. Ltd. was performed, a new ＂U＂ type baffle was obtained, and its parameters were defined by perpendicular analysis. The ＂U＂ baffle can not only improve those imperfections, but also prolong the residence time of nonmetallic inclusions, which is good for their flotation and separation.展开更多
Iterations in optimization and numerical simulation for the sheet metal forming process may lead to extensive computation. In addition, uncertainties in materials or processing parameters may have great influence on t...Iterations in optimization and numerical simulation for the sheet metal forming process may lead to extensive computation. In addition, uncertainties in materials or processing parameters may have great influence on the design quality. A six sigma optimization method is proposed, by combining the dual response surface method （DRSM） and six sigma philosophy, to save computation cost and improve reliability and robustness of parts. Using this method, statistical technology, including the design of experiment and analysis of variance, approximate model and six sigma philosophy are integrated together to achieve improved quality. Two sheet metal forming processes are provided as examples to illustrate the proposed method.展开更多
The accuracy of an articulated torque analysis influences the comprehensive performances of heavy-duty multi-legged robots. Currently, the extremal estimation method and some complex methods are employed to calculate ...The accuracy of an articulated torque analysis influences the comprehensive performances of heavy-duty multi-legged robots. Currently, the extremal estimation method and some complex methods are employed to calculate the articulated torques, which results in a large safety margin or a large number of calculations. To quickly obtain accurate articulated torques, an analysis method for the articulated torque is presented for an electrically driven heavy-duty six-legged robot. First, the rearmost leg that experiences the maximum normal contact force is confirmed when the robot transits a slope. Based on the ant-type and crab-type tripod gaits, the formulas of classical mechanics and MATLAB software are employed to theoretically analyze the relevant static torques of the joints. With the changes in the joint angles for the abductor joint, hip joint, and knee joint, variable tendency charts and extreme curves are obtained for the static articulated torques. Meanwhile, the maximum static articulated torques and the corresponding poses of the robot are also obtained. According to the poses of the robot under the maximum static articulated torques, ADAMS software is used to carry out a static simulation analysis. Based on the relevant simulation curves of the articulated torques, the maximum static articulated torques are acquired. A comparative analysis of the maximum static articulated torques shows that the theoretical calculation values are higher than the static simulation values, and the maximum error value is approximately 10%. The proposed method lays a foundation for quickly determining accurate articulated torques to develop heavy-duty six-legged robots.展开更多
Stewart platform(SP) is a promising choice for large component alignment, and interactive force measurements are a novel and significant approach for high-precision assemblies. The designed position and orientation(P&...Stewart platform(SP) is a promising choice for large component alignment, and interactive force measurements are a novel and significant approach for high-precision assemblies. The designed position and orientation(P&O) adjusting platform, based on an SP for force/torquedriven(F/T-driven) alignment, can dynamically measure interactive forces. This paper presents an analytical algorithm of measuring six-dimensional F/T based on the screw theory for accurate determination of external forces during alignment. Dynamic gravity deviations were taken into consideration and a compensation model was developed. The P&O number was optimized as well.Given the specific appearance of repeated six-dimensional F/T measurements, an approximate cone shape was used for spatial precision analysis. The magnitudes and directions of measured F/Ts can be evaluated by a set of standards, in terms of accuracy and repeatability. Experiments were also performed using a known applied load, and the proposed analytical algorithm was able to accurately predict the F/T. A comparison between precision analysis experiments with or without assembly fixtures was performed. Experimental results show that the measurement accuracy varies under different P&O sets and higher loads lead to poorer accuracy of dynamic gravity compensation. In addition, the preferable operation range has been discussed for high-precision assemblies with smaller deviations.展开更多
Alcoholic liver disease(ALD) is the second most common diagnosis among patients undergoing liver transplantation(LT).The recovery results of patients transplanted for ALD are often at least as good as those of patient...Alcoholic liver disease(ALD) is the second most common diagnosis among patients undergoing liver transplantation(LT).The recovery results of patients transplanted for ALD are often at least as good as those of patients transplanted for other diagnoses and better than those suffering from hepatitis C virus, cryptogenic cirrhosis, or hepatocellular carcinoma.Inthe case of medically non-responding patients with severe acute alcoholic hepatitis or acute-on chronic liver failure, the refusal of LT is often based on the lack of the required alcohol abstinence period of six months.The obligatory abidance of a period of abstinence as a transplant eligibility requirement for medically non-responding patients seems unfair and inhumane, since the majority of these patients will not survive the six-month abstinence period.Data from various studies have challenged the 6-mo rule, while excellent survival results of LT have been observed in selected patients with severe alcoholic hepatitis not responding to medical therapy.Patients with severe advanced ALD should have legal access to LT.The mere lack of pre-LT abstinence should not be an obstacle for being listed.展开更多
A six-axis force sensor with parallel 8/4-4 structure is introduced and its measurement principle is analyzed.Based on condition numbers of Jacobian matrix spectral norm of the sensor,the relationship between the forc...A six-axis force sensor with parallel 8/4-4 structure is introduced and its measurement principle is analyzed.Based on condition numbers of Jacobian matrix spectral norm of the sensor,the relationship between the force and moment isotropy and some structural parameters is deduced.Orthogonal test methods are used to determine the degree of primary and secondary factors that have significant effect on sensor characteristics.Furthermore,the relationship between each performance index and the structural parameters of the sensor is analyzed by the method of the atlas,which lays a foundation for structural optimization design of the force sensor.展开更多
Six基因家族进化高度保守,在脊椎动物个体发育中起着重要作用。但目前对其调控机制尚不完全清楚。在UCSC (The University of California Santa Cruz) Genome Browser的斑马鱼基因组数据库中发现, Six2a-Six3a基因簇周围存在一条长链非...Six基因家族进化高度保守,在脊椎动物个体发育中起着重要作用。但目前对其调控机制尚不完全清楚。在UCSC (The University of California Santa Cruz) Genome Browser的斑马鱼基因组数据库中发现, Six2a-Six3a基因簇周围存在一条长链非编码RNA——Six2a-OT。首先,利用反转录PCR (RT-PCR)结合测序证实了该RNA确实存在。然后,利用荧光半定量PCR (qPCR)和整胚原位杂交(whole-mount in situ hybridization, WISH)确定了其特异性的表达模式:Six2a-OT在卵巢中的表达远高于精巢;在受精卵和早期原肠胚中高表达,随后显著下降;受精后48 h (48 hpf)集中表达于耳囊(otic vesicle)、躯干中线(trunk midline)和鳃弓(branchial archs)。随后,进一步利用反义吗啡啉(morpholino)特异性阻断Six2a-OT剪接,观察到63%的48 hpf胚胎表现出躯干变短、侧弯,或心包积水,同时Six2a和Six3a的表达显著下降。以上结果表明:Six2a-OT作为母源性因子通过调节Six2a和Six3a的表达参与斑马鱼胚胎早期发育。这为揭示Six基因簇的表达调控机制提供了重要依据。展开更多
An Autler-Townes（AT） spectroscopy based on phase conjugate six-wave mixing（SWM） is proposed to detect AT doublet of high-lying state in a Doppler-broadened cascade four-level system.It is found that the SWM spectr...An Autler-Townes（AT） spectroscopy based on phase conjugate six-wave mixing（SWM） is proposed to detect AT doublet of high-lying state in a Doppler-broadened cascade four-level system.It is found that the SWM spectrum is dependent strongly on the ratios between the magnitudes of the wave vectors.We discuss how the Doppler broadening affects the SWM spectrum from a time-domain viewpoint and find that,due the atomic motion,the atomic polarizations acquire different phases for atoms with different velocities as time evolves.The Doppler free SWM spectrum can be obtained only when the atomic polarization can be rephasing again at certain time after the interactions of all the incident fields.展开更多
文摘尖孢镰刀菌古巴专化型(Fusarium oxysporum f. sp. cubense,Foc)依据对寄主易感性分为4个不同的生理小种,其中4号生理小种(Foc4)几乎能危害目前所有栽培品种。为研究其SIX(secreted in xylem)蛋白编码基因SIX2和SIX6在Foc4对寄主差异性选择中的作用,利用PEG介导的原生质体转化法将基于pCT74质粒框架构建的SIX2、SIX6基因敲除质粒分别转入Foc4 B2菌株,分别得到了SIX2和SIX6基因敲除突变体,然后分析敲除突变体与野生型的生物学特性差异。生物学研究结果表明:SIX2、SIX6基因的缺失突变体均呈现菌丝稀疏、生长速率减慢、产孢率降低、菌丝异核率增加,对渗透压、外源氧等外源胁迫更为敏感等特征。致病力分析实验发现ΔFoSIX2和ΔFoSIX6突变体的孢子在香蕉苗的幼嫩根部附着量减少,孢子根部定殖能力降低;ΔFoSIX2菌株基本上丧失了对巴西蕉的致病力,而对粉蕉仍有较强的致病能力;ΔFoSIX6菌株则对粉蕉苗、巴西香蕉苗盆栽致病力均呈极显著下降。依据生物学与致病力测定结果,推测Foc4中SIX6基因决定Foc4对寄主的致病力,而SIX2基因则决定Foc4对寄主的差异性选择能力。
基金supported by the National Key Research and Development Program of China (No. 2016YFB0200700)the National Nature Science Foundation of China (No. 11872089, No. 11572024, No. 11432002)Defence Industrial Technology Development Programs of China (No. JCKY2016601B001, No. JCKY2016204B101, No. JCKY2017601B001) for the financial supports
文摘Lightweight design is important for the Thermal Protection System(TPS) of hypersonic vehicles in that it protects the inner structure from severe heating environment. However, due to the existence of uncertainties in material properties and geometry, it is imperative to incorporate uncertainty analysis into the design optimization to obtain reliable results. In this paper, a six sigma robust design optimization based on Successive Response Surface Method(SRSM) is established for the TPS to improve the reliability and robustness with considering the uncertainties. The uncertain parameters related to material properties and thicknesses of insulation layers are considered and characterized by random variables following normal distributions. By employing SRSM, the values of objective function and constraints are approximated by the response surfaces to reduce computational cost. The optimization is an iterative process with response surfaces updating to find the true optimal solution. The optimization of the nose cone of hypersonic vehicle cabin is provided as an example to illustrate the feasibility and effectiveness of the proposed method.
基金Item Sponsored by National High Technology Research and Development Plan of China(2007AA04Z194)
文摘A 1∶2.5 scale tundish model was set up in laboratory for a six-strand billet continuous casting tundish with different configurations to investigate fluid flow characteristics under different operational conditions by measuring residence time distribution curves.It was found that minimum residence time,maximum concentration time and average residence time of the three strands on the same side of the tundish with the former configuration under normal operation,that is,six strands were open,were small and non-uniform and the tundish had large dead volume fraction.Vortexes easily formed on the liquid surface in the pouring zone of the tundish.The fluid flow characteristics in the tundish with the optimal turbulence inhibitor and baffles were improved and became less non-uniform among the strands.Vortexes were not found on the pouring zone surface in the optimal tundish.For non-normal operation,that is,one strand was close,it was important to choose which strand to be closed for maintaining flow characteristics of the rest two strands.It was found from this investigation that fluid flow characteristics in the optimal configuration tundish with closing strand 2 were better than those with closing strand 3 on the same side.
文摘Improper flow control devices in a multi-strand tundish can cause some problems, for example, liquid steel cannot reach every nozzle at the same time and the liquid steel in nozzles far away from the entry zone has a lower temperature. The water model experiment of a six-strand tundish of Tianjin Iron ＆ Steel Co. Ltd. was performed, a new ＂U＂ type baffle was obtained, and its parameters were defined by perpendicular analysis. The ＂U＂ baffle can not only improve those imperfections, but also prolong the residence time of nonmetallic inclusions, which is good for their flotation and separation.
基金This project is supported by National Natural Science Foundation of China (No.50475020).
文摘Iterations in optimization and numerical simulation for the sheet metal forming process may lead to extensive computation. In addition, uncertainties in materials or processing parameters may have great influence on the design quality. A six sigma optimization method is proposed, by combining the dual response surface method （DRSM） and six sigma philosophy, to save computation cost and improve reliability and robustness of parts. Using this method, statistical technology, including the design of experiment and analysis of variance, approximate model and six sigma philosophy are integrated together to achieve improved quality. Two sheet metal forming processes are provided as examples to illustrate the proposed method.
基金supported by National Basic Research Program of China(973 Program, Grant No. 2013CB035502)International Science and Technology Cooperation Project with Russia (Grant No. 2010DFR70270)+2 种基金National Natural Science Foundation of China (Grant No. 51275106)"111" Project (Grant No. B07018)Key Laboratory Opening Funding of Aerospace Mechanism and Control, China (Grant No. HIT. KLOF.2010057)
文摘The accuracy of an articulated torque analysis influences the comprehensive performances of heavy-duty multi-legged robots. Currently, the extremal estimation method and some complex methods are employed to calculate the articulated torques, which results in a large safety margin or a large number of calculations. To quickly obtain accurate articulated torques, an analysis method for the articulated torque is presented for an electrically driven heavy-duty six-legged robot. First, the rearmost leg that experiences the maximum normal contact force is confirmed when the robot transits a slope. Based on the ant-type and crab-type tripod gaits, the formulas of classical mechanics and MATLAB software are employed to theoretically analyze the relevant static torques of the joints. With the changes in the joint angles for the abductor joint, hip joint, and knee joint, variable tendency charts and extreme curves are obtained for the static articulated torques. Meanwhile, the maximum static articulated torques and the corresponding poses of the robot are also obtained. According to the poses of the robot under the maximum static articulated torques, ADAMS software is used to carry out a static simulation analysis. Based on the relevant simulation curves of the articulated torques, the maximum static articulated torques are acquired. A comparative analysis of the maximum static articulated torques shows that the theoretical calculation values are higher than the static simulation values, and the maximum error value is approximately 10%. The proposed method lays a foundation for quickly determining accurate articulated torques to develop heavy-duty six-legged robots.
基金co-supported by the National Defense Basic Scientific Research (No. A2120132007)the Fund of National Engineering and Research Center for Commercial Aircraft Manufacturing (No. SAMC14-JS-15-055)
文摘Stewart platform(SP) is a promising choice for large component alignment, and interactive force measurements are a novel and significant approach for high-precision assemblies. The designed position and orientation(P&O) adjusting platform, based on an SP for force/torquedriven(F/T-driven) alignment, can dynamically measure interactive forces. This paper presents an analytical algorithm of measuring six-dimensional F/T based on the screw theory for accurate determination of external forces during alignment. Dynamic gravity deviations were taken into consideration and a compensation model was developed. The P&O number was optimized as well.Given the specific appearance of repeated six-dimensional F/T measurements, an approximate cone shape was used for spatial precision analysis. The magnitudes and directions of measured F/Ts can be evaluated by a set of standards, in terms of accuracy and repeatability. Experiments were also performed using a known applied load, and the proposed analytical algorithm was able to accurately predict the F/T. A comparison between precision analysis experiments with or without assembly fixtures was performed. Experimental results show that the measurement accuracy varies under different P&O sets and higher loads lead to poorer accuracy of dynamic gravity compensation. In addition, the preferable operation range has been discussed for high-precision assemblies with smaller deviations.
文摘Alcoholic liver disease(ALD) is the second most common diagnosis among patients undergoing liver transplantation(LT).The recovery results of patients transplanted for ALD are often at least as good as those of patients transplanted for other diagnoses and better than those suffering from hepatitis C virus, cryptogenic cirrhosis, or hepatocellular carcinoma.Inthe case of medically non-responding patients with severe acute alcoholic hepatitis or acute-on chronic liver failure, the refusal of LT is often based on the lack of the required alcohol abstinence period of six months.The obligatory abidance of a period of abstinence as a transplant eligibility requirement for medically non-responding patients seems unfair and inhumane, since the majority of these patients will not survive the six-month abstinence period.Data from various studies have challenged the 6-mo rule, while excellent survival results of LT have been observed in selected patients with severe alcoholic hepatitis not responding to medical therapy.Patients with severe advanced ALD should have legal access to LT.The mere lack of pre-LT abstinence should not be an obstacle for being listed.
基金supported by the Open Foundation of Graduate Innovation Base(Laboratory)of Nanjing University of Aeronautics and Astronautics (No.kfjj20170512)the National Natural Science Foundation of China(No. 51175263)
文摘A six-axis force sensor with parallel 8/4-4 structure is introduced and its measurement principle is analyzed.Based on condition numbers of Jacobian matrix spectral norm of the sensor,the relationship between the force and moment isotropy and some structural parameters is deduced.Orthogonal test methods are used to determine the degree of primary and secondary factors that have significant effect on sensor characteristics.Furthermore,the relationship between each performance index and the structural parameters of the sensor is analyzed by the method of the atlas,which lays a foundation for structural optimization design of the force sensor.
文摘Six基因家族进化高度保守,在脊椎动物个体发育中起着重要作用。但目前对其调控机制尚不完全清楚。在UCSC (The University of California Santa Cruz) Genome Browser的斑马鱼基因组数据库中发现, Six2a-Six3a基因簇周围存在一条长链非编码RNA——Six2a-OT。首先,利用反转录PCR (RT-PCR)结合测序证实了该RNA确实存在。然后,利用荧光半定量PCR (qPCR)和整胚原位杂交(whole-mount in situ hybridization, WISH)确定了其特异性的表达模式:Six2a-OT在卵巢中的表达远高于精巢;在受精卵和早期原肠胚中高表达,随后显著下降;受精后48 h (48 hpf)集中表达于耳囊(otic vesicle)、躯干中线(trunk midline)和鳃弓(branchial archs)。随后,进一步利用反义吗啡啉(morpholino)特异性阻断Six2a-OT剪接,观察到63%的48 hpf胚胎表现出躯干变短、侧弯,或心包积水,同时Six2a和Six3a的表达显著下降。以上结果表明:Six2a-OT作为母源性因子通过调节Six2a和Six3a的表达参与斑马鱼胚胎早期发育。这为揭示Six基因簇的表达调控机制提供了重要依据。
基金Project supported by the National Basic Research Program of China(Grant No.2013CB922002)the National Natural Science Foundation of China(Grant Nos.11274376 and 61308011)the National High Technology Research and Development Program of China(Grant No.2011AA120102)
文摘An Autler-Townes（AT） spectroscopy based on phase conjugate six-wave mixing（SWM） is proposed to detect AT doublet of high-lying state in a Doppler-broadened cascade four-level system.It is found that the SWM spectrum is dependent strongly on the ratios between the magnitudes of the wave vectors.We discuss how the Doppler broadening affects the SWM spectrum from a time-domain viewpoint and find that,due the atomic motion,the atomic polarizations acquire different phases for atoms with different velocities as time evolves.The Doppler free SWM spectrum can be obtained only when the atomic polarization can be rephasing again at certain time after the interactions of all the incident fields.
