The precipitation kinetics of 2519 A aluminum alloy after different cold rolling reductions before aging was investigated by hardness test and differential scanning calorimetry（DSC）. The activation energy was calcul...The precipitation kinetics of 2519 A aluminum alloy after different cold rolling reductions before aging was investigated by hardness test and differential scanning calorimetry（DSC）. The activation energy was calculated according to DSC curves using single heating rate method. The microstructures of as-rolled and peak-aged alloys were observed by transmission electron microscopy（TEM）. The result shows that the age hardenability reduces and the activation energy rises with increasing the reduction from 7% to 40%. Nonuniform dislocations are found in as-rolled alloy and inhomogeneous distribution of θ′ phase is revealed in peak-aged alloy when the reduction is 15%. The inhomogeneous distribution of θ′ phase may be related to the age hardenability reducing and activation energy rising.展开更多
The effect of Ru on γ＇ precipitation behavior and evolution in single crystal superalloys with different Ru contents were investigated by scanning electron microscopy with energy dispersive spectroscopy,3D atomic pr...The effect of Ru on γ＇ precipitation behavior and evolution in single crystal superalloys with different Ru contents were investigated by scanning electron microscopy with energy dispersive spectroscopy,3D atomic probing,differential scanning calorimetry.The results show that the solvus of the γ＇ phase decreases gradually with increasing Ru content in the alloys by casting or by the same solution and aging treatments,the alloy with a larger Ru content yields a smaller γ＇ phase.The addition of Ru increases the growth rate and coarsening rate of the γ＇ phase.Ru mainly distributes in the γ phase,which causes more Re and Mo partition into the γ＇ phase,increasing the absolute value of mismatch and the rafting rate of the γ＇ phase.展开更多
The mechanical properties and microstructure of Al-Cu-Li alloy sheets subjected to cryorolling(-100 ° C,-190 ℃) or hot rolling(400 ℃) and subsequent aging at 160 ℃ for different times were investigated. The dy...The mechanical properties and microstructure of Al-Cu-Li alloy sheets subjected to cryorolling(-100 ° C,-190 ℃) or hot rolling(400 ℃) and subsequent aging at 160 ℃ for different times were investigated. The dynamic precipitation and dislocation characterizations were examined via transmission electron microscopy and X-ray diffraction. The grain morphologies and the fracture-surface morphologies were studied via optical microscopy and scanning electron microscopy. Samples subjected to cryorolling followed by aging exhibited relatively high dislocation densities and a large number of precipitates compared with hot-rolled samples. The samples cryorolled at-190 ℃ and then aged for 15 h presented the highest ultimate tensile strength(586 MPa), while the alloy processed via hot rolling followed by 10 h aging exhibited the highest uniform elongation rate(11.5%). The size of precipitates increased with the aging time, which has significant effects on the interaction mechanism between dislocations and precipitates. Bowing is the main interaction method between the deformation-induced dislocations and coarsened precipitates during tensile tests, leading to the decline of the mechanical properties of the alloy during overaging. These interesting findings can provide significant insights into the development of materials possessing both excellent strength and high ductility.展开更多
The evolution of Ti3Ni4 precipitates in Ti49.2Ni50.8 alloy during equal channel angular pressing(ECAP) and intermediate annealing was investigated by transmission electron microscopy. The solution-treated Ti49.2Ni50.8...The evolution of Ti3Ni4 precipitates in Ti49.2Ni50.8 alloy during equal channel angular pressing(ECAP) and intermediate annealing was investigated by transmission electron microscopy. The solution-treated Ti49.2Ni50.8 alloy was aged at 450 ℃ for 10 to 60 min to obtain Ti3Ni4 precipitates ranging from 37 to 75 nm. After ECAP at 450 ℃ for one pass, Ti3Ni4 precipitates introduced by aging for 10 and 30 min totally dissolve into the matrix;however, those produced by aging for 60 min become smaller. The critical size of Ti3Ni4 precipitates to totally dissolve into matrix is determined to be in the range of 37-68 nm. The dislocation density of ECAP-processed samples depends on the initial size of Ti3Ni4 precipitates after aging. With increasing the duration of initial aging from 10 to 60 min, the dislocation density firstly increases and then decreases.展开更多
The peer review policy of the World Journal of Gastroenterology （WJG） states that all articles received are subjected to peer review. Normally, three experts are invited to review each article. Decision for acceptan...The peer review policy of the World Journal of Gastroenterology （WJG） states that all articles received are subjected to peer review. Normally, three experts are invited to review each article. Decision for acceptance is made only when at least two experts recommend. Otherwise, the article is rejected. This is to ensure that high standards are maintained and the work is original. In medical sciences, there is a tendency for work to be incremental, ideas being developed gradually, with major breakthroughs being relatively rare. Consequently there tends to be significant overlap in which a field already investigated is researched from a different angle or using alternative methods.展开更多
The Enhanced Variable Rate Codec (EVRC) is a standard for the Speech Service Option 3 for Wideband Spread Spectrum Digital System, which has been employed in both IS-95 cellular systems and ANSI J-STC-008 PCS (Persona...The Enhanced Variable Rate Codec (EVRC) is a standard for the Speech Service Option 3 for Wideband Spread Spectrum Digital System, which has been employed in both IS-95 cellular systems and ANSI J-STC-008 PCS (Personal Communications Systems). This paper investigated the combination of turbo codes with Unequal Error Protection (UEP) and 16-QAM modulation for EVRC codec of Rate 1 to get power and bandwidth efficient coding scheme. The results show that the UEP system outperforms the Equal Error Protection (EEP) one by 1.45 dB at BER of 10 -5.展开更多
The harsh space radiation environment compromises the reliability of an on-board switching fabric by leading to cross-point and switching element(SE)faults.Different from traditional faulttolerant switching fabrics on...The harsh space radiation environment compromises the reliability of an on-board switching fabric by leading to cross-point and switching element(SE)faults.Different from traditional faulttolerant switching fabrics only taking crosspoint faults into account,a novel Input and Output Parallel Clos network,referred to as the(p_1,p_2)-IOPClos,is proposed to tolerate both cross-point and SE faults.In the(p_1,p_2)-IOPClos,there are p_1 and p_2 expanded parallel switching planes in the input and output stages,respectively.The multiple input/output switching planes are interconnected through the middle stage to provide multiple paths in each stage by which the network throughput can be increased remarkably.Furthermore,the network reliability of the(p_1,p_2)-IOPClos under the above both kinds of faults is analyzed.The corresponding implementation cost is also presented along with the network size.Both theoretical analysis and numerical results indicate that the(p_1,p_2)-IOPClos outperforms traditional Clos-type networks at reliability,while has less implementation cost than the multi-plane Clos network.展开更多
According to Chinese medicine,the atlantoaxial joint is a composite joint composed of tendons and bones,and the stability of the joint depends on the‘tendon-bone balance’involving tendons,ligaments,atlas and axis.Mu...According to Chinese medicine,the atlantoaxial joint is a composite joint composed of tendons and bones,and the stability of the joint depends on the‘tendon-bone balance’involving tendons,ligaments,atlas and axis.Multiple causes of‘tendon off-position,joint subluxation’will lead to joint‘tendon-bone imbalance’,which will evolve into atlantoaxial subluxation(AAS),endangering human health.Chinese therapeutic massage(tuina)is a very effective treatment for AAS in adults,but conventional manipulations are prone to ineffectiveness or accidents due to neglect of the causal relationship of the‘tendon-bone imbalance’and inappropriate manipulations.Compared with conventional manipulations,the rational choice of modified manipulations under the guidance of‘tendon-bone balance’theory is more effective and less risky,and more worthy of clinical promotion.From the‘tendon-bone balance’theory,we considered the shortcomings of conventional manipulations,and introduced several modified manipulations that have their own strengths in‘tendon smoothing’and‘bone setting’,in order to provide new ideas for treatment of AAS in adults.展开更多
A dynamic model is established for an offset-disc rotor system with a mechanical gear coupling, which takes into consideration the nonlinear restoring force of rotor support and the effect of coupling misalignment. Pe...A dynamic model is established for an offset-disc rotor system with a mechanical gear coupling, which takes into consideration the nonlinear restoring force of rotor support and the effect of coupling misalignment. Periodic solutions are obtained through harmonic balance method with alternating frequency/time domain(HB-AFT) technique, and then compared with the results of numerical simulation. Good agreement confirms the feasibility of HB-AFT scheme. Moreover, the Floquet theory is adopted to analyze motion stability of the system when rotor runs at different speed intervals. A simple strategy to determine the monodromy matrix is introduced and two ways towards unstability are found for periodic solutions: the period doubling bifurcation and the secondary Hopf bifurcation. The results obtained will contribute to the global response analysis and dynamic optimal design of rotor systems.展开更多
基金Project(2012CB619500)supported by the National Basic Research Program of China
文摘The precipitation kinetics of 2519 A aluminum alloy after different cold rolling reductions before aging was investigated by hardness test and differential scanning calorimetry（DSC）. The activation energy was calculated according to DSC curves using single heating rate method. The microstructures of as-rolled and peak-aged alloys were observed by transmission electron microscopy（TEM）. The result shows that the age hardenability reduces and the activation energy rises with increasing the reduction from 7% to 40%. Nonuniform dislocations are found in as-rolled alloy and inhomogeneous distribution of θ′ phase is revealed in peak-aged alloy when the reduction is 15%. The inhomogeneous distribution of θ′ phase may be related to the age hardenability reducing and activation energy rising.
基金Project(U1037601) supported by the National Natural Science Foundation of China
文摘The effect of Ru on γ＇ precipitation behavior and evolution in single crystal superalloys with different Ru contents were investigated by scanning electron microscopy with energy dispersive spectroscopy,3D atomic probing,differential scanning calorimetry.The results show that the solvus of the γ＇ phase decreases gradually with increasing Ru content in the alloys by casting or by the same solution and aging treatments,the alloy with a larger Ru content yields a smaller γ＇ phase.The addition of Ru increases the growth rate and coarsening rate of the γ＇ phase.Ru mainly distributes in the γ phase,which causes more Re and Mo partition into the γ＇ phase,increasing the absolute value of mismatch and the rafting rate of the γ＇ phase.
基金Project(2019YFB2006500) supported by the National Key Research and Development Program,ChinaProject(51674303) supported by the National Natural Science Foundation of China+3 种基金Project(2020GK2032) supported by Hunan High-tech Industry Science and Technology Innovation Leading Plan,ChinaProject (2018RS3015) supported by the Huxiang High-level Talent Gathering Project of Hunan Province,ChinaProject(2017YFA0700700) supported by the Ministry of Science&Technology of ChinaProject(2019CX006) supported by Innovation Driven Program of Central South University,China。
文摘The mechanical properties and microstructure of Al-Cu-Li alloy sheets subjected to cryorolling(-100 ° C,-190 ℃) or hot rolling(400 ℃) and subsequent aging at 160 ℃ for different times were investigated. The dynamic precipitation and dislocation characterizations were examined via transmission electron microscopy and X-ray diffraction. The grain morphologies and the fracture-surface morphologies were studied via optical microscopy and scanning electron microscopy. Samples subjected to cryorolling followed by aging exhibited relatively high dislocation densities and a large number of precipitates compared with hot-rolled samples. The samples cryorolled at-190 ℃ and then aged for 15 h presented the highest ultimate tensile strength(586 MPa), while the alloy processed via hot rolling followed by 10 h aging exhibited the highest uniform elongation rate(11.5%). The size of precipitates increased with the aging time, which has significant effects on the interaction mechanism between dislocations and precipitates. Bowing is the main interaction method between the deformation-induced dislocations and coarsened precipitates during tensile tests, leading to the decline of the mechanical properties of the alloy during overaging. These interesting findings can provide significant insights into the development of materials possessing both excellent strength and high ductility.
基金financial supports from the National Natural Science Foundation of China (51671064)the National Key R&D Program of China (2017YFE0123500)。
文摘The evolution of Ti3Ni4 precipitates in Ti49.2Ni50.8 alloy during equal channel angular pressing(ECAP) and intermediate annealing was investigated by transmission electron microscopy. The solution-treated Ti49.2Ni50.8 alloy was aged at 450 ℃ for 10 to 60 min to obtain Ti3Ni4 precipitates ranging from 37 to 75 nm. After ECAP at 450 ℃ for one pass, Ti3Ni4 precipitates introduced by aging for 10 and 30 min totally dissolve into the matrix;however, those produced by aging for 60 min become smaller. The critical size of Ti3Ni4 precipitates to totally dissolve into matrix is determined to be in the range of 37-68 nm. The dislocation density of ECAP-processed samples depends on the initial size of Ti3Ni4 precipitates after aging. With increasing the duration of initial aging from 10 to 60 min, the dislocation density firstly increases and then decreases.
文摘The peer review policy of the World Journal of Gastroenterology （WJG） states that all articles received are subjected to peer review. Normally, three experts are invited to review each article. Decision for acceptance is made only when at least two experts recommend. Otherwise, the article is rejected. This is to ensure that high standards are maintained and the work is original. In medical sciences, there is a tendency for work to be incremental, ideas being developed gradually, with major breakthroughs being relatively rare. Consequently there tends to be significant overlap in which a field already investigated is researched from a different angle or using alternative methods.
基金National Natural Science Foundation ofChina( No.6972 5 0 0 1)
文摘The Enhanced Variable Rate Codec (EVRC) is a standard for the Speech Service Option 3 for Wideband Spread Spectrum Digital System, which has been employed in both IS-95 cellular systems and ANSI J-STC-008 PCS (Personal Communications Systems). This paper investigated the combination of turbo codes with Unequal Error Protection (UEP) and 16-QAM modulation for EVRC codec of Rate 1 to get power and bandwidth efficient coding scheme. The results show that the UEP system outperforms the Equal Error Protection (EEP) one by 1.45 dB at BER of 10 -5.
基金supported by the National Natural Science Foundation of China(91338108,91438206)
文摘The harsh space radiation environment compromises the reliability of an on-board switching fabric by leading to cross-point and switching element(SE)faults.Different from traditional faulttolerant switching fabrics only taking crosspoint faults into account,a novel Input and Output Parallel Clos network,referred to as the(p_1,p_2)-IOPClos,is proposed to tolerate both cross-point and SE faults.In the(p_1,p_2)-IOPClos,there are p_1 and p_2 expanded parallel switching planes in the input and output stages,respectively.The multiple input/output switching planes are interconnected through the middle stage to provide multiple paths in each stage by which the network throughput can be increased remarkably.Furthermore,the network reliability of the(p_1,p_2)-IOPClos under the above both kinds of faults is analyzed.The corresponding implementation cost is also presented along with the network size.Both theoretical analysis and numerical results indicate that the(p_1,p_2)-IOPClos outperforms traditional Clos-type networks at reliability,while has less implementation cost than the multi-plane Clos network.
文摘According to Chinese medicine,the atlantoaxial joint is a composite joint composed of tendons and bones,and the stability of the joint depends on the‘tendon-bone balance’involving tendons,ligaments,atlas and axis.Multiple causes of‘tendon off-position,joint subluxation’will lead to joint‘tendon-bone imbalance’,which will evolve into atlantoaxial subluxation(AAS),endangering human health.Chinese therapeutic massage(tuina)is a very effective treatment for AAS in adults,but conventional manipulations are prone to ineffectiveness or accidents due to neglect of the causal relationship of the‘tendon-bone imbalance’and inappropriate manipulations.Compared with conventional manipulations,the rational choice of modified manipulations under the guidance of‘tendon-bone balance’theory is more effective and less risky,and more worthy of clinical promotion.From the‘tendon-bone balance’theory,we considered the shortcomings of conventional manipulations,and introduced several modified manipulations that have their own strengths in‘tendon smoothing’and‘bone setting’,in order to provide new ideas for treatment of AAS in adults.
基金supported by the National Basic Research Program of China("973" Project)(Grant No.2015CB057400)the National Natural Science Foundation of China(Grant No.11302058)
文摘A dynamic model is established for an offset-disc rotor system with a mechanical gear coupling, which takes into consideration the nonlinear restoring force of rotor support and the effect of coupling misalignment. Periodic solutions are obtained through harmonic balance method with alternating frequency/time domain(HB-AFT) technique, and then compared with the results of numerical simulation. Good agreement confirms the feasibility of HB-AFT scheme. Moreover, the Floquet theory is adopted to analyze motion stability of the system when rotor runs at different speed intervals. A simple strategy to determine the monodromy matrix is introduced and two ways towards unstability are found for periodic solutions: the period doubling bifurcation and the secondary Hopf bifurcation. The results obtained will contribute to the global response analysis and dynamic optimal design of rotor systems.
