Cryptographic properties of the single cycle T-function's output sequences are investigated.Bounds of autocorrelation functions of the kth coordinate sequence and bounds of state output sequence are calculated res...Cryptographic properties of the single cycle T-function's output sequences are investigated.Bounds of autocorrelation functions of the kth coordinate sequence and bounds of state output sequence are calculated respectively.The Maximum Sidelobe Ratio(MSR) of the kth coordinate sequence and the MSR of state output sequence are given respectively.The bounds of autocorrelation functions show that the values of autocorrelation functions are large when shifts are small.Comparisons of the autocorrelations between the state output sequence and coordinate output sequence are illustrated.The autocorrelation properties demonstrate that T-functions have cryptographic weaknesses and the illustration result shows coordinate output sequences have better autocorrelation than that of state output sequences.展开更多
In the original publication,incorrect version of Corresponding authors has been published.You-Yuan Huang and Bo Wang should be corresponding authors.The corrected Correspondingg authors are provided in this correction.
Four kinds of sequences generated by single cycle triangular function （T-function） are investigated to check the possibility for a single cycle T-function to be a cryptographic component in stream ciphers. Based on ...Four kinds of sequences generated by single cycle triangular function （T-function） are investigated to check the possibility for a single cycle T-function to be a cryptographic component in stream ciphers. Based on the special properties of single cycle T-function and an algorithm due to Wei, linear complexities of these four kinds of sequence are all acquired. The results show that single cycle T-function sequences have high linear complexity. Therefore, T-function satisfies the essential requirements being a basic component of stream cipher.展开更多
The second generation single crystal superalloy DD6 with 0.10%Hf and 0.34%Hf （in mass fraction） was subjected to high-cycle fatigue （HCF） loading at temperatures of 700 ℃ in ambient atmosphere. SEM was used to de...The second generation single crystal superalloy DD6 with 0.10%Hf and 0.34%Hf （in mass fraction） was subjected to high-cycle fatigue （HCF） loading at temperatures of 700 ℃ in ambient atmosphere. SEM was used to determine the initiation site and the failure mechanism. Evolution of the microstructure was investigated by TEM observation. The results show that fatigue limit of DD6 alloy with 0.34%Hf is a little smaller than that of the alloy with 0.10%Hf. The fatigue cracks initiated on the surface or near the surface of the specimens. The crack would propagate along { 111 } octahedral slip planes, rather than perpendicular to the loading axis of specimen. Typical fatigue striation formed in steady propagation of fatigue crack. The fracture mechanisms of the high cycle fatigue of DD6 alloys with 0.10%Hf and 0.34%Hf are quasi-cleavage fracture. Different types of dislocation structures were developed during high cycle fatigue deformation.展开更多
The low-cycle fatigue （LCF） behavior of a nickel-based single crystal superalloy with [001] orientation was studied at an intermediate temperature of T0℃ and a higher temperature of To ＋ 250℃ under a constant low...The low-cycle fatigue （LCF） behavior of a nickel-based single crystal superalloy with [001] orientation was studied at an intermediate temperature of T0℃ and a higher temperature of To ＋ 250℃ under a constant low strain rate of 10^-3 s^-1 in ambient atmosphere. The superalloy exhibited cyclic tension-compression asymmetry which is dependent on the temperature and applied strain amplitude. Analysis on the fracture surfaces showed that the surface and subsurface casting micropores were the major crack initiation sites. Interior Ta-rich carbides were frequently observed in all specimens. Two distinct types of fracture were suggested by fractogaphy. One type was characterized by Mode-I cracking with a microscopically rough surface at To ＋ 250℃. Whereas the other type at lower temperature T0℃ favored either one or several of the octahedral {111} planes, in contrast to the normal Mode-I growth mode typically observed at low loading frequencies （several Hz）. The failure mechanisms for two cracking modes are shearing of γ＇ precipitates together with the matrix at T0℃ and cracking confined in the matrix and the γ/γ＇interface at To - 250℃.展开更多
Samples of DD3 single crystal superalloy with different dimensions were cast in the directionally solidified furnace with high temperature gradient. The effect of cast dimension on the rotary bending high cycle fatig...Samples of DD3 single crystal superalloy with different dimensions were cast in the directionally solidified furnace with high temperature gradient. The effect of cast dimension on the rotary bending high cycle fatigue （HCF） properties of the alloy was investigated at 800 ℃ in ambient atmosphere. SEM was used to examine the fracture sur- face and fracture mechanism of the all.oy. The results show that the rotary bending HCF properties of the alloy de- creases with increasing cast dimension. The cast dimension has little effect on the HCF fracture mechanism of the al loy. The HCF fracture mechanism of the alloy with different cast dimensions is all quasi-cleavage fracture. The fa- tigue cracks initiated on the surface or near the surface of the specimens. The crack would propagate along { 111} oc- tahedral slip planes. Typical fatigue arc and striation formed on fatigue crack steady propagation. The degenera- tion of HCF properties is due to the increase of dendrite arm spacing and size of γ＇ phase particles and maximal microporosity.展开更多
Single thermal cycle simulation tests were carried out for X80 high strength steel pipes from three steel mills by a Gleeble 3500HS thermal simulation test machine,and coincidence degree of the thermal simulation curv...Single thermal cycle simulation tests were carried out for X80 high strength steel pipes from three steel mills by a Gleeble 3500HS thermal simulation test machine,and coincidence degree of the thermal simulation curve with the set curve under heat inputs of 6–30 kJ/cm was observed;The relationship between different heat inputs and microstructure,impact toughness and hardness of steel pipe CGHAZ(coarse grain heat affected zone)was studied by metallographic examination,impact test and hardness test.The results show that with the increase of heat input,original austenite grain size increases gradually,the lath bainite ratio decreases and the granular bainite ratio increases.The impact toughness of C steel pipe is lower than those of A and B steel pipe,and the impact toughness of CGHAZ from the three steel pipes show different trends:for A steel pipe CGHAZ,impact toughness increases first and then decreases,with the highest value of 270–320 J under 20–25 kJ/cm;for B steel pipe CGHAZ,impact toughness decreases slightly;for C steel pipe CGHAZ,impact toughness increases,with the highest value of 260–300 J under 25 kJ/cm.As the heat input increases,the hardness of three X80 steel pipes CGHAZ shows a decreasing trhighend,and C steel pipe has the largest decreasing range.展开更多
Low-cycle fatigue behaviors of Ni-base single crystal superalloys containing different Re contents have been investigated at 760℃. During heat treatment. Reretards γ phases coarsening and equalizes the distribution ...Low-cycle fatigue behaviors of Ni-base single crystal superalloys containing different Re contents have been investigated at 760℃. During heat treatment. Reretards γ phases coarsening and equalizes the distribution of γ' phases. As Re content increases, fatigue life increases and slip bands distribute more inhomogeneously. Moreover, adding Re not only reduces stacking fault energy of the matrix, but also promotes the element segregation to increase the lattice misfit. However, the larger lattice misfit does not lead to the formation of dislocation networks, but which activates dislocation movement and promotes dislocations cross-slip and climbing movement under high temperature and applied stress. On the other hand, with the addition of Re, cyclic deformation behaviors change from cyclic hardening to cyclic stability, mainly depending on a transformation of deformation mechanisms from slip bands cutting through γ and γ' phases to stacking faults shearing.展开更多
The influence of crystal orientations on the low-cycle fatigue(LCF) behavior of a 3Re-bearing Ni-based single-crystal superalloy at 980 °C has been investigated. It is found that the orientation dependence of the...The influence of crystal orientations on the low-cycle fatigue(LCF) behavior of a 3Re-bearing Ni-based single-crystal superalloy at 980 °C has been investigated. It is found that the orientation dependence of the fatigue life not only depends on the elastic modulus, but also the number of active slip planes and the plasticity of materials determine the LCF life,especially for the [011] and [111] specimens. The [011] and [111] specimens with better plasticity withstand relatively concentrated inelastic deformation caused by fewer active slip planes, compared to the [001] specimens resisting widespread deformation caused by a higher number of active slip planes. Additionally, fatigue fracture is also influenced by cyclic plastic deformation mechanisms of the alloy with crystal orientations, and the [001] specimens are plastically deformed by wave slip mechanism and fracture along the non-crystallographic plane, while the [011] and [111] specimens are plastically deformed by planar slip mechanism and fracture along the crystallographic planes. Moreover, casting pores,eutectics, inclusions and surface oxide layers not only initiate the crack, but also reduce the stress concentration around crack tips. Our results throw light upon the effect of inelastic strain on the LCF life and analyze the cyclic plastic deformation for the alloy with different orientations.展开更多
Low cycle fatigue behavior of a nickel-based single-crystal superalloy DD10 was investigated at 760 and 980 ℃ under different strain ranges. Results show that the fatigue life （Nf） of DD10 alloy exhibits different ...Low cycle fatigue behavior of a nickel-based single-crystal superalloy DD10 was investigated at 760 and 980 ℃ under different strain ranges. Results show that the fatigue life （Nf） of DD10 alloy exhibits different temperature dependence under various strain ranges. Under low strain range, the alloy exhibits a longer Nf at 760 ℃ than that at 980 ℃. However, under high strain range, a reverse result is obtained. This difference can be attributed to the change of dominant damage modes under various test conditions, which is manifested in different modes of crack initiation （crack nucleation and its early propagation）. At 760 ℃, the crack initiates at pores in subsurface due to local stress concentration. This process is mainly controlled by plastic amplitude and plastic property, but not affected by oxygen-induced damage before the crack propagates to the surface. At 980 ℃, the crack initiates at surface instead of pores due to the more homogeneous plastic deformation and the disharmony between the external oxidation layer and the bulk material when the strain amplitude is high. At that temperature, the process is mainly controlled by oxidation damage and strain amplitude simultaneously. Therefore, under high strain range, the crack initiation is much easier at 760 ℃ due to plastic deformation and the poor plasticity, while under low strain range obvious oxidation damage at 980℃ may accelerate the crack initiation.展开更多
TiO2 is a wide band gap semiconductor with important applications in photovoltaic cells. Vertically aligned Tit2 nanorod arrays （NRs） are grown on the fluorine-doped tin oxide （FTO） substrates by a multicycle hydr...TiO2 is a wide band gap semiconductor with important applications in photovoltaic cells. Vertically aligned Tit2 nanorod arrays （NRs） are grown on the fluorine-doped tin oxide （FTO） substrates by a multicycle hydrothermal synthesis process. The samples are characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, high-resolution transmission electron microscopy （HRTEM）, and selected-area electron diffraction （SAED）. It is found that dye-sensitized solar cells （DSSCs） assembled by the as-prepared Tit2 single-crystal NRs exhibit different trends under the condition of different nucleation and growth concentrations. Optimum cell performance is obtained with high nucleation concentration and low growth cycle concentration. The efficiency enhancement is mainly attributed to the improved specific surface area of the nanorod.展开更多
The paper studied the relationship between microstructure and shape recovery characteristics by using colored microstructure analysis under polarized light on the thermomechanical cycled CuAlNi single crystals. The tw...The paper studied the relationship between microstructure and shape recovery characteristics by using colored microstructure analysis under polarized light on the thermomechanical cycled CuAlNi single crystals. The two-way shape memory effect in quenched thin bar resulted from the preferential formation/extinction of martensite variant due to the internal quench stress, and the variant was formed at an angle of about 45 deg. with the tension direction ([001] of the βphase). Initial thermomechanical cycling under relatively low stress single variant stress-induced martensite was formed at an angle of 45 deg. with the tension and its morphology was a lath of parallel twins. More than one group of variants were formed after several training cycles and such variants also caused tilting of some thermally formed accommodated martensite. By overheating the trained sample containing stabilized multi-variants of stress-induced martensite, very coarse martensite structure with a strong asymmetry was produced, which caused the reverse two-way shape memory effect.展开更多
High-cycle rotating bending fatigue behavior of SRR99 nickel-base single crystal alloy at 700 and 900℃ was investigated. The fatigue strengths for 107 cycles are 350 and 335MPa at 700 and 900℃, respectively. T...High-cycle rotating bending fatigue behavior of SRR99 nickel-base single crystal alloy at 700 and 900℃ was investigated. The fatigue strengths for 107 cycles are 350 and 335MPa at 700 and 900℃, respectively. The total fatigue life becomes shorter when the temperature increases regardless of the loading stress and frequency. With the number of cycles decreasing, the difference in fatigue strength at the two temperatures becomes smaller. Typical fatigue rupture process including crack initiation site, crack propagation region and final rupture region exhibits at 700℃. The fracture surface is basically characterized by cleavage rupture at 900℃.展开更多
Ni-rich cathode materials will be primarily used as next-generation high-specific energy cathode materials in lithium-ion batteries.However,residual Li formation and cracking considerably restrict the wide application...Ni-rich cathode materials will be primarily used as next-generation high-specific energy cathode materials in lithium-ion batteries.However,residual Li formation and cracking considerably restrict the wide application of these materials.To address the issues related to cracking,micro-sized single-crystal cathode materials without internal grain boundaries are proposed.In this study,we constructed a thin LiBO_(2)layer on the single-crystal LiNi_(0.83)Co_(0.07)Mn_(0.10)O_(2)particles by solvent-free H_(3)BO_(3)modification.The residual Li on the material surface decreased by 14%through the reaction of LiOH/Li_(2)CO_(3)and H_(3)BO_(3).The coated materials exhibited higher initial Coulombic efficiency(88.44%),higher reversible capacity(213.4 mAh·g^(-1)at 0.1 C),and better cycling performance(91.31%retention over 50 cycles within 3.0-4.3 V at 1.0C)than the unmodified materials.Using the galvanostatic intermittent titration technique,electrochemical impedance spectroscopy(EIS),and inductively coupled plasma-optical emission spectroscopy(ICP-OES),we reveal the mechanism by which the electrochemical properties are improved upon H_(3)BO_(3)modification.The superior electrochemical performances are associated with increased Li+conductivity,lower charge transfer impedance,and suppressed transition metal dissolution.Therefore,this study demonstrates the importance of surface modification in obtaining Ni-rich single-crystal materials with enhanced performance.展开更多
Linked partitions were introduced by Dykema(Dykema K J. Multilinear function series and transforms in free probability theory. Adv. Math., 2005, 208(1):351–407) in the study of the unsymmetrized T-transform in free p...Linked partitions were introduced by Dykema(Dykema K J. Multilinear function series and transforms in free probability theory. Adv. Math., 2005, 208(1):351–407) in the study of the unsymmetrized T-transform in free probability theory.Permutation is one of the most classical combinatorial structures. According to the linear representation of linked partitions, Chen et al.(Chen W Y C, Wu S Y J, Yan C H. Linked partitions and linked cycles. European J. Combin., 2008, 29(6): 1408–1426) de?ned the concept of singly covered minimal elements. Let L(n, k) denote the set of linked partitions of [n] with k singly covered minimal elements and let P(n, k) denote the set of permutations of [n] with k cycles. In this paper, we mainly establish two bijections between L(n, k) and P(n, k). The two bijections from a different perspective show the one-to-one correspondence between the singly covered minimal elements in L(n, k) and the cycles in P(n, k).展开更多
AIM: To investigate the associations between the polymorphisms of cell cycle pathway genes and the risk of hepatocellular carcinoma(HCC). METHODS: We enrolled 1127 cases newly diagnosed with HCC from the Tumor Hospita...AIM: To investigate the associations between the polymorphisms of cell cycle pathway genes and the risk of hepatocellular carcinoma(HCC). METHODS: We enrolled 1127 cases newly diagnosed with HCC from the Tumor Hospital of Guangxi Medical University and 1200 non-tumor patients from the First Affiliated Hospital of Guangxi Medical University. General demographic characteristics, behavioral information, and hematological indices were collected by unified questionnaires. Genomic DNA was isolatedfrom peripheral venous blood using Phenol-Chloroform. The genotyping was performed using the Sequenom Mass ARRAY i PLEX genotyping method. The association between genetic polymorphisms and risk of HCC was shown by P-value and the odd ratio(OR) with 95% confidence interval(CI) using the unconditional logistic regression after adjusting for age, sex, nationality, smoking, drinking, family history of HCC, and hepatitis B virus(HBV) infection. Moreover, stratified analysis was conducted on the basis of the status of HBV infection, smoking, and alcohol drinking.RESULTS: The HCC risk was lower in patients with the MCM4 rs2305952 CC(OR = 0.22, 95%CI: 0.08-0.63, P = 0.01) and with the CHEK1 rs515255 TC, TT, TC/TT(OR = 0.73, 95%CI: 0.56-0.96, P = 0.02; OR = 0.67, 95%CI: 0.46-0.97, P = 0.04; OR = 0.72, 95%CI: 0.56-0.92, P = 0.01, respectively). Conversely, the HCC risk was higher in patients with the KAT2 B rs17006625 GG(OR = 1.64, 95%CI: 1.01-2.64, P = 0.04). In addition, the risk was markedly lower for those who were carriers of MCM4 rs2305952 CC and were also HBs Ag-positive and non-drinking and nonsmoking(P < 0.05, respectively) and for those who were carriers of CHEK1 rs515255 TC, TT, TC/TT and were also HBs Ag-negative and non-drinking(P < 0.05, respectively). Moreover, the risk was higher for those who were carriers of KAT2 B rs17006625 GG and were also HBs Ag-negative(P < 0.05).CONCLUSION: Of 12 cell cycle pathway genes, MCM4, CHEK1 and KAT2 B polymorphisms may be associated with the risk of HCC.展开更多
Uniaxial ratcheting behaviour and low cycle fatigue(LCF)failure mechanism of nickel-based single crystal superalloy DD6 with[001]orientation are investigated through the stresscontrolled LCF tests with stress ratio of...Uniaxial ratcheting behaviour and low cycle fatigue(LCF)failure mechanism of nickel-based single crystal superalloy DD6 with[001]orientation are investigated through the stresscontrolled LCF tests with stress ratio of-1.Then the deformation behaviour during the wholelifetime from the beginning of the experiment to the fracture of the specimen,as well as the fractographic/metallographic morphology,are compared with the strain-controlled LCF experimental results.Through the scanning electron microscope(SEM)observations,it is shown that the failure characteristics under stress-controlled LCF loading are similar with those under strain-controlled loading.Nevertheless,unlike strain-controlled LCF loading,even under fully reversed cycle loading for stress-controlled LCF,DD6 shows significant ratcheting behaviour due to the tensioncompression asymmetry.In addition,the LCF lifetimes under stress control are significantly shorter than the LCF lifetimes under strain control,and the culprit might be the detrimental effect of ratcheting strain on LCF lifetime.Based on these phenomena,an improved crystal plasticity constitutive model on the basis of slip-based Walker constitutive model is developed through modifying the kinematic hardening rule in order to overcome the inaccurate prediction of decelerating stageand stable stage of ratcheting behaviour.Furthermore,combining the continuum damage mechanics,a damage-coupled crystal plasticity constitutive model is proposed to reflect the damage behaviour of DD6 and the accelerating stage of ratcheting behaviour.The simulation results for the stress-controlled LCF deformation behaviour including the whole-lifetime ratcheting behaviour show good agreement with the experimental data.展开更多
Hard carbons(HCs)are recognized as the most mature and commercially promising anode materials for sodium-ion batteries.However,they still face the challenge of relatively suboptimal rate performance,which necessitates...Hard carbons(HCs)are recognized as the most mature and commercially promising anode materials for sodium-ion batteries.However,they still face the challenge of relatively suboptimal rate performance,which necessitates further improvements.In this study,we employ a dual strategy involving atomic-level cobalt(Co)doping and high-current formation cycling(FC)to effectively enhance the performance of hard carbon materials.The catalytic activity of Co atoms can not only modulate the intrinsic structure of hard carbon but also regulate the electrochemical reactions at the hard carbon-electrolyte interface.After FC process,the hard carbon surface rapidly forms a high-quality solid electrolyte interphase(SEI)film that is rich in inorganic components,exhibits uniformity and possesses an optimal density.These effectively mitigate the adverse effects of surface concentration polarization on Na storage behavior while enhancing the migration kinetics of Na^(+).The optimized Co-GC anode material demonstrates a remarkable Na storage capacity and fast-charging capability,maintaining a capacity of 229.63 mAh g^(−1)after 3000 cycles at a current density of 1.5 A g^(−1).This study highlights the significance and opportunities of regulating the interfacial environment for improving the electrochemical performance of HCs.展开更多
To explore the tensile property parameters in the structural design of bridge deck link slabs made by ecological high ductility cementitious composites (Eco-HDCC), the tensile properties of Eco-HDCC exposed to interac...To explore the tensile property parameters in the structural design of bridge deck link slabs made by ecological high ductility cementitious composites (Eco-HDCC), the tensile properties of Eco-HDCC exposed to interactive freeze-thaw-carbonation cycles and single carbonation cycles were studied. The carbonation front of Eco-HDCC was determined by X-ray diffraction and differential scanning calorimetry-thermal gravimetric methods. Results indicate that the carbonation front of Eco-HDCC after interaction tests is deeper than that of Eco-HDCC after single carbonation tests. In addition, the ultimate tensile strength for Eco-HDCC shows an increasing trend after the interaction of 1 to 5 cycles compared with that of virgin specimens, while the ultimate tensile strength decreases after the interaction of 10 to 15 cycles. For single carbonation tests, the ultimate tensile strength of Eco-HDCC increases as cycles increase. After being subjected to interaction and single carbonation environments, both the ultimate tensile strain and tensile strain energy of Eco-HDCC decrease as cycles increase, and the decrease degrees of Eco-HDCC after interaction cycles are larger than those of Eco-HDCC after single carbonation. For general consideration, the tensile stress-strain relationship of Eco-HDCC after the interaction of 15 cycles can be adopted in the design of bridge deck link slabs for the purpose of safety.展开更多
基金supported by National Natural Science Foundation of China under Grant No.60833008,60970119the Scientific Research Foundation of Education of Department of Shaanxi Provincial Government of China under Grant No.11JK0503+1 种基金Youth Science and Technology Foundation of Xi'an University of Architecture and Technology under Grant No.QN0831,QN1024Foundation of Guangxi Key Laboratory of Information and Communications under Grant No.20902
文摘Cryptographic properties of the single cycle T-function's output sequences are investigated.Bounds of autocorrelation functions of the kth coordinate sequence and bounds of state output sequence are calculated respectively.The Maximum Sidelobe Ratio(MSR) of the kth coordinate sequence and the MSR of state output sequence are given respectively.The bounds of autocorrelation functions show that the values of autocorrelation functions are large when shifts are small.Comparisons of the autocorrelations between the state output sequence and coordinate output sequence are illustrated.The autocorrelation properties demonstrate that T-functions have cryptographic weaknesses and the illustration result shows coordinate output sequences have better autocorrelation than that of state output sequences.
文摘In the original publication,incorrect version of Corresponding authors has been published.You-Yuan Huang and Bo Wang should be corresponding authors.The corrected Correspondingg authors are provided in this correction.
基金supported by the National Natural Science Foundation of China (60833008,60803149)the Scientific Research Foundation of Education Department of Shaanxi Provincial Government of China (11JK0503)the Youth Science and Technology Foundation of Xi’an University of Architecture and Technology (QN0831,QN1024)
文摘Four kinds of sequences generated by single cycle triangular function （T-function） are investigated to check the possibility for a single cycle T-function to be a cryptographic component in stream ciphers. Based on the special properties of single cycle T-function and an algorithm due to Wei, linear complexities of these four kinds of sequence are all acquired. The results show that single cycle T-function sequences have high linear complexity. Therefore, T-function satisfies the essential requirements being a basic component of stream cipher.
文摘The second generation single crystal superalloy DD6 with 0.10%Hf and 0.34%Hf （in mass fraction） was subjected to high-cycle fatigue （HCF） loading at temperatures of 700 ℃ in ambient atmosphere. SEM was used to determine the initiation site and the failure mechanism. Evolution of the microstructure was investigated by TEM observation. The results show that fatigue limit of DD6 alloy with 0.34%Hf is a little smaller than that of the alloy with 0.10%Hf. The fatigue cracks initiated on the surface or near the surface of the specimens. The crack would propagate along { 111 } octahedral slip planes, rather than perpendicular to the loading axis of specimen. Typical fatigue striation formed in steady propagation of fatigue crack. The fracture mechanisms of the high cycle fatigue of DD6 alloys with 0.10%Hf and 0.34%Hf are quasi-cleavage fracture. Different types of dislocation structures were developed during high cycle fatigue deformation.
基金supported by the National Natural Science Foundation of China(No.50371042).
文摘The low-cycle fatigue （LCF） behavior of a nickel-based single crystal superalloy with [001] orientation was studied at an intermediate temperature of T0℃ and a higher temperature of To ＋ 250℃ under a constant low strain rate of 10^-3 s^-1 in ambient atmosphere. The superalloy exhibited cyclic tension-compression asymmetry which is dependent on the temperature and applied strain amplitude. Analysis on the fracture surfaces showed that the surface and subsurface casting micropores were the major crack initiation sites. Interior Ta-rich carbides were frequently observed in all specimens. Two distinct types of fracture were suggested by fractogaphy. One type was characterized by Mode-I cracking with a microscopically rough surface at To ＋ 250℃. Whereas the other type at lower temperature T0℃ favored either one or several of the octahedral {111} planes, in contrast to the normal Mode-I growth mode typically observed at low loading frequencies （several Hz）. The failure mechanisms for two cracking modes are shearing of γ＇ precipitates together with the matrix at T0℃ and cracking confined in the matrix and the γ/γ＇interface at To - 250℃.
文摘Samples of DD3 single crystal superalloy with different dimensions were cast in the directionally solidified furnace with high temperature gradient. The effect of cast dimension on the rotary bending high cycle fatigue （HCF） properties of the alloy was investigated at 800 ℃ in ambient atmosphere. SEM was used to examine the fracture sur- face and fracture mechanism of the all.oy. The results show that the rotary bending HCF properties of the alloy de- creases with increasing cast dimension. The cast dimension has little effect on the HCF fracture mechanism of the al loy. The HCF fracture mechanism of the alloy with different cast dimensions is all quasi-cleavage fracture. The fa- tigue cracks initiated on the surface or near the surface of the specimens. The crack would propagate along { 111} oc- tahedral slip planes. Typical fatigue arc and striation formed on fatigue crack steady propagation. The degenera- tion of HCF properties is due to the increase of dendrite arm spacing and size of γ＇ phase particles and maximal microporosity.
基金supported by Science and Technology Research Project of Universities of Hebei Province(No.QN201.221)。
文摘Single thermal cycle simulation tests were carried out for X80 high strength steel pipes from three steel mills by a Gleeble 3500HS thermal simulation test machine,and coincidence degree of the thermal simulation curve with the set curve under heat inputs of 6–30 kJ/cm was observed;The relationship between different heat inputs and microstructure,impact toughness and hardness of steel pipe CGHAZ(coarse grain heat affected zone)was studied by metallographic examination,impact test and hardness test.The results show that with the increase of heat input,original austenite grain size increases gradually,the lath bainite ratio decreases and the granular bainite ratio increases.The impact toughness of C steel pipe is lower than those of A and B steel pipe,and the impact toughness of CGHAZ from the three steel pipes show different trends:for A steel pipe CGHAZ,impact toughness increases first and then decreases,with the highest value of 270–320 J under 20–25 kJ/cm;for B steel pipe CGHAZ,impact toughness decreases slightly;for C steel pipe CGHAZ,impact toughness increases,with the highest value of 260–300 J under 25 kJ/cm.As the heat input increases,the hardness of three X80 steel pipes CGHAZ shows a decreasing trhighend,and C steel pipe has the largest decreasing range.
基金supported financially by the National Natural Science Foundation of China (Nos. 51671188, 51571196 and 51601192)the Shenyang Science and Technology Project (No. 17-101-2-00)
文摘Low-cycle fatigue behaviors of Ni-base single crystal superalloys containing different Re contents have been investigated at 760℃. During heat treatment. Reretards γ phases coarsening and equalizes the distribution of γ' phases. As Re content increases, fatigue life increases and slip bands distribute more inhomogeneously. Moreover, adding Re not only reduces stacking fault energy of the matrix, but also promotes the element segregation to increase the lattice misfit. However, the larger lattice misfit does not lead to the formation of dislocation networks, but which activates dislocation movement and promotes dislocations cross-slip and climbing movement under high temperature and applied stress. On the other hand, with the addition of Re, cyclic deformation behaviors change from cyclic hardening to cyclic stability, mainly depending on a transformation of deformation mechanisms from slip bands cutting through γ and γ' phases to stacking faults shearing.
基金supported by the National Natural Science Foundation of China (Nos. 51571196, 51671188 and 5160119)Shenyang Science and Technology Project (No. 17-101-2-00)
文摘The influence of crystal orientations on the low-cycle fatigue(LCF) behavior of a 3Re-bearing Ni-based single-crystal superalloy at 980 °C has been investigated. It is found that the orientation dependence of the fatigue life not only depends on the elastic modulus, but also the number of active slip planes and the plasticity of materials determine the LCF life,especially for the [011] and [111] specimens. The [011] and [111] specimens with better plasticity withstand relatively concentrated inelastic deformation caused by fewer active slip planes, compared to the [001] specimens resisting widespread deformation caused by a higher number of active slip planes. Additionally, fatigue fracture is also influenced by cyclic plastic deformation mechanisms of the alloy with crystal orientations, and the [001] specimens are plastically deformed by wave slip mechanism and fracture along the non-crystallographic plane, while the [011] and [111] specimens are plastically deformed by planar slip mechanism and fracture along the crystallographic planes. Moreover, casting pores,eutectics, inclusions and surface oxide layers not only initiate the crack, but also reduce the stress concentration around crack tips. Our results throw light upon the effect of inelastic strain on the LCF life and analyze the cyclic plastic deformation for the alloy with different orientations.
基金financially supported by the National Basic Research Program of China (Nos. 2012AA03A511 and 2012AA03A513)the National Natural Science Foundation of China (Nos. 51101160 and 51171193)
文摘Low cycle fatigue behavior of a nickel-based single-crystal superalloy DD10 was investigated at 760 and 980 ℃ under different strain ranges. Results show that the fatigue life （Nf） of DD10 alloy exhibits different temperature dependence under various strain ranges. Under low strain range, the alloy exhibits a longer Nf at 760 ℃ than that at 980 ℃. However, under high strain range, a reverse result is obtained. This difference can be attributed to the change of dominant damage modes under various test conditions, which is manifested in different modes of crack initiation （crack nucleation and its early propagation）. At 760 ℃, the crack initiates at pores in subsurface due to local stress concentration. This process is mainly controlled by plastic amplitude and plastic property, but not affected by oxygen-induced damage before the crack propagates to the surface. At 980 ℃, the crack initiates at surface instead of pores due to the more homogeneous plastic deformation and the disharmony between the external oxidation layer and the bulk material when the strain amplitude is high. At that temperature, the process is mainly controlled by oxidation damage and strain amplitude simultaneously. Therefore, under high strain range, the crack initiation is much easier at 760 ℃ due to plastic deformation and the poor plasticity, while under low strain range obvious oxidation damage at 980℃ may accelerate the crack initiation.
基金Project supported by the Fundamental Research Funds for the Central Universities,China(Grant No.2013XK07)
文摘TiO2 is a wide band gap semiconductor with important applications in photovoltaic cells. Vertically aligned Tit2 nanorod arrays （NRs） are grown on the fluorine-doped tin oxide （FTO） substrates by a multicycle hydrothermal synthesis process. The samples are characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, high-resolution transmission electron microscopy （HRTEM）, and selected-area electron diffraction （SAED）. It is found that dye-sensitized solar cells （DSSCs） assembled by the as-prepared Tit2 single-crystal NRs exhibit different trends under the condition of different nucleation and growth concentrations. Optimum cell performance is obtained with high nucleation concentration and low growth cycle concentration. The efficiency enhancement is mainly attributed to the improved specific surface area of the nanorod.
文摘The paper studied the relationship between microstructure and shape recovery characteristics by using colored microstructure analysis under polarized light on the thermomechanical cycled CuAlNi single crystals. The two-way shape memory effect in quenched thin bar resulted from the preferential formation/extinction of martensite variant due to the internal quench stress, and the variant was formed at an angle of about 45 deg. with the tension direction ([001] of the βphase). Initial thermomechanical cycling under relatively low stress single variant stress-induced martensite was formed at an angle of 45 deg. with the tension and its morphology was a lath of parallel twins. More than one group of variants were formed after several training cycles and such variants also caused tilting of some thermally formed accommodated martensite. By overheating the trained sample containing stabilized multi-variants of stress-induced martensite, very coarse martensite structure with a strong asymmetry was produced, which caused the reverse two-way shape memory effect.
文摘High-cycle rotating bending fatigue behavior of SRR99 nickel-base single crystal alloy at 700 and 900℃ was investigated. The fatigue strengths for 107 cycles are 350 and 335MPa at 700 and 900℃, respectively. The total fatigue life becomes shorter when the temperature increases regardless of the loading stress and frequency. With the number of cycles decreasing, the difference in fatigue strength at the two temperatures becomes smaller. Typical fatigue rupture process including crack initiation site, crack propagation region and final rupture region exhibits at 700℃. The fracture surface is basically characterized by cleavage rupture at 900℃.
基金financially supported by China Postdoctoral Science Foundation(Nos.2021M690478 and 2021M700523)。
文摘Ni-rich cathode materials will be primarily used as next-generation high-specific energy cathode materials in lithium-ion batteries.However,residual Li formation and cracking considerably restrict the wide application of these materials.To address the issues related to cracking,micro-sized single-crystal cathode materials without internal grain boundaries are proposed.In this study,we constructed a thin LiBO_(2)layer on the single-crystal LiNi_(0.83)Co_(0.07)Mn_(0.10)O_(2)particles by solvent-free H_(3)BO_(3)modification.The residual Li on the material surface decreased by 14%through the reaction of LiOH/Li_(2)CO_(3)and H_(3)BO_(3).The coated materials exhibited higher initial Coulombic efficiency(88.44%),higher reversible capacity(213.4 mAh·g^(-1)at 0.1 C),and better cycling performance(91.31%retention over 50 cycles within 3.0-4.3 V at 1.0C)than the unmodified materials.Using the galvanostatic intermittent titration technique,electrochemical impedance spectroscopy(EIS),and inductively coupled plasma-optical emission spectroscopy(ICP-OES),we reveal the mechanism by which the electrochemical properties are improved upon H_(3)BO_(3)modification.The superior electrochemical performances are associated with increased Li+conductivity,lower charge transfer impedance,and suppressed transition metal dissolution.Therefore,this study demonstrates the importance of surface modification in obtaining Ni-rich single-crystal materials with enhanced performance.
基金The NSF(11601020,11501014) of China2017 Commercial Specialty Project(19005757053) of BTBU2018 Postgraduate Research Capacity Improvement Project(19008001491) of BTBU
文摘Linked partitions were introduced by Dykema(Dykema K J. Multilinear function series and transforms in free probability theory. Adv. Math., 2005, 208(1):351–407) in the study of the unsymmetrized T-transform in free probability theory.Permutation is one of the most classical combinatorial structures. According to the linear representation of linked partitions, Chen et al.(Chen W Y C, Wu S Y J, Yan C H. Linked partitions and linked cycles. European J. Combin., 2008, 29(6): 1408–1426) de?ned the concept of singly covered minimal elements. Let L(n, k) denote the set of linked partitions of [n] with k singly covered minimal elements and let P(n, k) denote the set of permutations of [n] with k cycles. In this paper, we mainly establish two bijections between L(n, k) and P(n, k). The two bijections from a different perspective show the one-to-one correspondence between the singly covered minimal elements in L(n, k) and the cycles in P(n, k).
基金Supported by National Natural Science Foundation of China,No.81360448Natural Science Foundation of Guangxi,No.2014GXNSFAA118139+1 种基金Fund of Key Laboratory of High Incidence-Tumor Prevention and Treatment(Guangxi Medical University),Ministry of Education,No.GK2015-ZZ03 and No.GK2014-ZZ03Guangxi Outstanding Teacher Training Project for Colleges
文摘AIM: To investigate the associations between the polymorphisms of cell cycle pathway genes and the risk of hepatocellular carcinoma(HCC). METHODS: We enrolled 1127 cases newly diagnosed with HCC from the Tumor Hospital of Guangxi Medical University and 1200 non-tumor patients from the First Affiliated Hospital of Guangxi Medical University. General demographic characteristics, behavioral information, and hematological indices were collected by unified questionnaires. Genomic DNA was isolatedfrom peripheral venous blood using Phenol-Chloroform. The genotyping was performed using the Sequenom Mass ARRAY i PLEX genotyping method. The association between genetic polymorphisms and risk of HCC was shown by P-value and the odd ratio(OR) with 95% confidence interval(CI) using the unconditional logistic regression after adjusting for age, sex, nationality, smoking, drinking, family history of HCC, and hepatitis B virus(HBV) infection. Moreover, stratified analysis was conducted on the basis of the status of HBV infection, smoking, and alcohol drinking.RESULTS: The HCC risk was lower in patients with the MCM4 rs2305952 CC(OR = 0.22, 95%CI: 0.08-0.63, P = 0.01) and with the CHEK1 rs515255 TC, TT, TC/TT(OR = 0.73, 95%CI: 0.56-0.96, P = 0.02; OR = 0.67, 95%CI: 0.46-0.97, P = 0.04; OR = 0.72, 95%CI: 0.56-0.92, P = 0.01, respectively). Conversely, the HCC risk was higher in patients with the KAT2 B rs17006625 GG(OR = 1.64, 95%CI: 1.01-2.64, P = 0.04). In addition, the risk was markedly lower for those who were carriers of MCM4 rs2305952 CC and were also HBs Ag-positive and non-drinking and nonsmoking(P < 0.05, respectively) and for those who were carriers of CHEK1 rs515255 TC, TT, TC/TT and were also HBs Ag-negative and non-drinking(P < 0.05, respectively). Moreover, the risk was higher for those who were carriers of KAT2 B rs17006625 GG and were also HBs Ag-negative(P < 0.05).CONCLUSION: Of 12 cell cycle pathway genes, MCM4, CHEK1 and KAT2 B polymorphisms may be associated with the risk of HCC.
基金financial support from National Natural Science Foundation of China(Nos.51875020,51675024 and 51811540406)National Science and Technology Major Project(No.2017-IV-0004-0041)+1 种基金Aviation Science Foundation of China(No.6141B090314)Academic Excellence Foundation of BUAA。
文摘Uniaxial ratcheting behaviour and low cycle fatigue(LCF)failure mechanism of nickel-based single crystal superalloy DD6 with[001]orientation are investigated through the stresscontrolled LCF tests with stress ratio of-1.Then the deformation behaviour during the wholelifetime from the beginning of the experiment to the fracture of the specimen,as well as the fractographic/metallographic morphology,are compared with the strain-controlled LCF experimental results.Through the scanning electron microscope(SEM)observations,it is shown that the failure characteristics under stress-controlled LCF loading are similar with those under strain-controlled loading.Nevertheless,unlike strain-controlled LCF loading,even under fully reversed cycle loading for stress-controlled LCF,DD6 shows significant ratcheting behaviour due to the tensioncompression asymmetry.In addition,the LCF lifetimes under stress control are significantly shorter than the LCF lifetimes under strain control,and the culprit might be the detrimental effect of ratcheting strain on LCF lifetime.Based on these phenomena,an improved crystal plasticity constitutive model on the basis of slip-based Walker constitutive model is developed through modifying the kinematic hardening rule in order to overcome the inaccurate prediction of decelerating stageand stable stage of ratcheting behaviour.Furthermore,combining the continuum damage mechanics,a damage-coupled crystal plasticity constitutive model is proposed to reflect the damage behaviour of DD6 and the accelerating stage of ratcheting behaviour.The simulation results for the stress-controlled LCF deformation behaviour including the whole-lifetime ratcheting behaviour show good agreement with the experimental data.
基金supported by the Science Fund for Distinguished Young Scholars of Hunan Province(2023JJ10060)Young Elite Scientists Sponsorship Program by CAST(2023QNRC001)+3 种基金the Science and Technology Innovation Program of Hunan Province(2022RC1078)the Scientific Research Fund of Hunan Provincial Education Department(23A0003)the Fundamental Research Funds for the Central Universities of Central South University(2025ZZTS0301)supported in part by the High Performance Computing Center of Central South University.
文摘Hard carbons(HCs)are recognized as the most mature and commercially promising anode materials for sodium-ion batteries.However,they still face the challenge of relatively suboptimal rate performance,which necessitates further improvements.In this study,we employ a dual strategy involving atomic-level cobalt(Co)doping and high-current formation cycling(FC)to effectively enhance the performance of hard carbon materials.The catalytic activity of Co atoms can not only modulate the intrinsic structure of hard carbon but also regulate the electrochemical reactions at the hard carbon-electrolyte interface.After FC process,the hard carbon surface rapidly forms a high-quality solid electrolyte interphase(SEI)film that is rich in inorganic components,exhibits uniformity and possesses an optimal density.These effectively mitigate the adverse effects of surface concentration polarization on Na storage behavior while enhancing the migration kinetics of Na^(+).The optimized Co-GC anode material demonstrates a remarkable Na storage capacity and fast-charging capability,maintaining a capacity of 229.63 mAh g^(−1)after 3000 cycles at a current density of 1.5 A g^(−1).This study highlights the significance and opportunities of regulating the interfacial environment for improving the electrochemical performance of HCs.
基金The National Natural Science Foundation of China(No.51778133)the National Basic Research Program of China(973Program)(No.2015CB655102)+1 种基金the Fundamental Research Funds for the Central Universities(No.3212009403)the China Railway Project(No.2017G007-C)
文摘To explore the tensile property parameters in the structural design of bridge deck link slabs made by ecological high ductility cementitious composites (Eco-HDCC), the tensile properties of Eco-HDCC exposed to interactive freeze-thaw-carbonation cycles and single carbonation cycles were studied. The carbonation front of Eco-HDCC was determined by X-ray diffraction and differential scanning calorimetry-thermal gravimetric methods. Results indicate that the carbonation front of Eco-HDCC after interaction tests is deeper than that of Eco-HDCC after single carbonation tests. In addition, the ultimate tensile strength for Eco-HDCC shows an increasing trend after the interaction of 1 to 5 cycles compared with that of virgin specimens, while the ultimate tensile strength decreases after the interaction of 10 to 15 cycles. For single carbonation tests, the ultimate tensile strength of Eco-HDCC increases as cycles increase. After being subjected to interaction and single carbonation environments, both the ultimate tensile strain and tensile strain energy of Eco-HDCC decrease as cycles increase, and the decrease degrees of Eco-HDCC after interaction cycles are larger than those of Eco-HDCC after single carbonation. For general consideration, the tensile stress-strain relationship of Eco-HDCC after the interaction of 15 cycles can be adopted in the design of bridge deck link slabs for the purpose of safety.
