The effects of cyclic stress loading on the microstructual evolution and tensile properties of a medium-carbon super- bainitic steel were investigated. Experimental results show that the cyclic stress can induce the c...The effects of cyclic stress loading on the microstructual evolution and tensile properties of a medium-carbon super- bainitic steel were investigated. Experimental results show that the cyclic stress can induce the carbon gathering in austenite and phase transformation from film-like retained austenite to twin martensite, which will obviously enhance the tensile strength and the product of tensile strength and ductility. The higher the bainitic transformation temperature, the lower the transformation rate of the retained austenite. The amount and thickness of the film-like retained austenite play an important role during the cyclic stress induced phase transformation.展开更多
A general method was described to synthesize a highly hydrophobic cyclic peptide,cyclo[LWLWLWLWLQ]where underlines indicate D-configuration of the amino acid,by a two-step solid-phase/solution synthesis strategy.The l...A general method was described to synthesize a highly hydrophobic cyclic peptide,cyclo[LWLWLWLWLQ]where underlines indicate D-configuration of the amino acid,by a two-step solid-phase/solution synthesis strategy.The linear decapeptide was assembled by standard Boc chemistry on solid-phase and subsequently cyclized in solution with high efficiency and reproducibility. In subsequent purification by semi-preparative HPLC,50%(v/v) DMF/H_2O was employed as the solvent to overcome the difficulty of solubilization...展开更多
Low cycle fatigue tests under plastic strain control were carried out with a dual-phase steel containing 23 Vol.-％ martensite. Specimens hardened rapidly at first few cycles followed by a slight softening to saturati...Low cycle fatigue tests under plastic strain control were carried out with a dual-phase steel containing 23 Vol.-％ martensite. Specimens hardened rapidly at first few cycles followed by a slight softening to saturation stages when cycled at higher strain amplitudes, whereas at lower strain amplitudes the specimens presented continually hardening for a long time until saturation. TEM examination of the saturation dislocation structures show that clusters, parallel walls and cells were found at low, medium and high strain amplitude, respectively. It also has been found that the martensite/ferrite interfaces did not affect the dislocation structures signi- ficantly when a specimen was fatigued at lower strain amplitude. However, the dislocation struc- ture adjacent to the two-phase boundary is dif- ferent to some extent from that in the remote regions in the ferrite when a higher strain amplitude is applied.展开更多
Based on the assumption that a representative element of apearlitic steel is an aggregate of numerous spherical pearliticcolonies with randomly distributed orientations, and that each colonyis com- posed of many paral...Based on the assumption that a representative element of apearlitic steel is an aggregate of numerous spherical pearliticcolonies with randomly distributed orientations, and that each colonyis com- posed of many parallel fine lamellas of ferrite andcementite, a description for the dual-phase pearlitic steel isobtained by making use of a microstructure-based constitutiveequation for a single dual-phase pearlitic colony and the Hill'sself-consistent scheme. The elastoplastic response of dual-phasepearlitic steel BS11 subjected to asymmetrically cyclic loading isanalyzed, and a comparison with the experimental results showssatisfacto- ry agreement. The non-proportional cyclic plasticity ofBS11 is also analyzed, in which stress develops along a semi-circlein a biaxial tension/compression and shear stress plane, as istypically experienced by the sur- face elements in rolling andsliding contact.展开更多
Carboxycoumsrins were synthesized via the solid phase synthesis conviently. The resin bound cyclic malonic ester reacted with o-methoxy or o-hydroxybenzaldehydes. Then cyclization was processed under H2SO4 to afford...Carboxycoumsrins were synthesized via the solid phase synthesis conviently. The resin bound cyclic malonic ester reacted with o-methoxy or o-hydroxybenzaldehydes. Then cyclization was processed under H2SO4 to afford the products in excellent purities and yields.展开更多
Modulation recognition becomes unreliable at low signal-to-noise ratio(SNR)over fading channel.A novel method is proposed to recognize the digital modulated signals with frequency and phase offsets over multi-path fad...Modulation recognition becomes unreliable at low signal-to-noise ratio(SNR)over fading channel.A novel method is proposed to recognize the digital modulated signals with frequency and phase offsets over multi-path fading channels in this paper.This method can overcome the effects of phase offset,Gaussian noise and multi-path fading.To achieve this,firstly,the characteristic parameters search is constructed based on the cyclostationarity of received signals,to overcome the phase offset,Gaussian white noise,and influence caused by multi-path fading.Then,the carrier frequency of the received signal is estimated,and the maximum characteristic parameter is searched around the integer multiple carriers and their vicinities.Finally,the modulation types of the received signal with frequency and phase offsets are classified using decision thresholds.Simulation results demonstrate that the performance of the proposed method is better than the traditional methods when SNR is over 5dB,and that the proposed method is robust to frequency and phase offsets over multipath channels.展开更多
Bacterial flagellar filaments can undergo a polymorphic phase transition in both vitro and vivo environments. Each bacterial flagellar filament has 12 different helical forms which are macroscopically represented by d...Bacterial flagellar filaments can undergo a polymorphic phase transition in both vitro and vivo environments. Each bacterial flagellar filament has 12 different helical forms which are macroscopically represented by different pitch lengths and helix radii. For external mechanical force induced filament phase transitions, there is so far only one experiment performed by Hotani in 1982, who showed a very beautiful cyclic phase transition phenomenon in his experiment on isolated flagellar filaments. In the present paper, we give a detailed mechanical analysis on Hotani＇s experiments. Through theoretical computations, we obtained a phase transition rule based on the phase transition mechanism. The theoretical analysis provides a foundation facilitating the establishment of phase transition theory for bacterial flagellar filaments.展开更多
Globularαphases can significantly improve the ductility of titanium alloys.Cyclic heat treatment(CHT)has been proved to be an effective way to induce the formation of globularαphases inα+βtitanium alloy Ti-6Al-4V ...Globularαphases can significantly improve the ductility of titanium alloys.Cyclic heat treatment(CHT)has been proved to be an effective way to induce the formation of globularαphases inα+βtitanium alloy Ti-6Al-4V fabricated by laser aided additive manufacturing(LAAM).However,there is no prior research reporting methods for obtaining globularαphases in LAAM-built near-αtitanium alloys.This work investigated the cyclic heat treatment(CHT)procedures suitable for the LAAM-built near-αtitanium alloy Ti-6Al-2Sn-4Zr-2Mo(Ti6242)to attain the globularαphases.The results show that 980℃ is the most suitable upper temperature limit for CHT.However,it is difficult to achieve a high volume fraction of the globularαphases in the LAAM-built Ti6242 alloys through CHT,which is ascribed to the low composition gradient caused by moreα-stabilizing elements and fewerβ-stabilizing elements.The as-built sample demonstrated elongation of 6.3%,which is lower than the AMS 4919J standard(elongation≥10%).After 980℃ CHT and 980℃ CHT with solution heat-treatment,the formation of the globularαphases significantly increased the elongation to 13.5%and 12.9%,respectively.Although the mechanical strength is reduced after heat-treatment,the room-temperature tensile properties still exceed the AMS 4919J standard.Fractography examination showed that the as-built sample exhibited a mixed brittle and ductile fracture behavior,while the 980℃ CHT and 980℃ CHT with solution heat-treated samples displayed ductile fracture.展开更多
Resin-bound cyclic malonic ester l reacted with aryl isothiocynate, then was treated with bromine, followed by cleavage from the resin under perchloric acid to give benzothiazoles 4.
A new high dynamic synchronization algorithm using cyclic spectral density was presented according to the theories of cyclic spectral density and its anti-interface and anti-noise properties.The closed forms of freque...A new high dynamic synchronization algorithm using cyclic spectral density was presented according to the theories of cyclic spectral density and its anti-interface and anti-noise properties.The closed forms of frequency error and phase error were obtained,and their performances were analyzed.The in-phase signal throw costas loop was normalized to obtain a cosine signal.Cyclic spectral density of the cosine signal of was computed to obtain the frequency error and the phase error and then results were put into NCO to synchronize.Finally,the performance of the presented algorithms was compared with the conventional algorithms by virtue of simulations,and the simulation results proved the correctness and the superiority of the new algorithms.展开更多
Owing to the special layer-by-layer deposition process of directed energy deposition(DED),columnar coarse grains,produced by cyclic reheating with intrinsic directional heat flow along the building direc-tion,are diff...Owing to the special layer-by-layer deposition process of directed energy deposition(DED),columnar coarse grains,produced by cyclic reheating with intrinsic directional heat flow along the building direc-tion,are difficult to avoid.These grains result in strong anisotropic characteristics with poor mechanical properties,which restrict the application of DED products.This work proposes a novel fabrication strat-egy based on the cyclic-phase-transformation behavior,which can reduce the anisotropy and improve the mechanical properties of DED-printed stainless steel.Using this fabrication strategy,316 L powder(austenitic stainless steel)and 17-4PH powder(martensitic stainless steel)were mixed in different mass ratios to fabricate five types of DED-printed stainless steels.Among the five samples,P70(mixture of 70 wt%17-4PH powder and 30 wt%316 L powder)showed the weakest anisotropy and the best mechanical properties,which can be attributed to the cyclic phase transformation under cyclic reheating treatment and the transformation-induced plasticity(TRIP)effect over a wide range of strains,respectively.Com-pared with the pure 316 L printed material,the tensile test results of P70 showed that the yield strength(YS)and ultimate tensile strength(UTS)increased by 35.4%and 34.5%,respectively,whereas the uniform elongation(UE)and total elongation(TE)were improved by 63.9%and 31.4%,respectively.In addition,the strength-ductility balance(UTS×UE)increased by as much as 120.4%.The proposed fabrication strategy is expected to reduce the anisotropy in other materials that undergo cyclic-phase-transformation phe-nomena during additive manufacturing.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51171030 and 51604034)the Scientific and Technological Planning Project of Jilin Province,China(Grant No.20150520030JH)the Scientific and Technological Research Fund of Jilin Provincial Education Department during the Twelfth Five-year Plan Period,China(Grant No.2015-95)
文摘The effects of cyclic stress loading on the microstructual evolution and tensile properties of a medium-carbon super- bainitic steel were investigated. Experimental results show that the cyclic stress can induce the carbon gathering in austenite and phase transformation from film-like retained austenite to twin martensite, which will obviously enhance the tensile strength and the product of tensile strength and ductility. The higher the bainitic transformation temperature, the lower the transformation rate of the retained austenite. The amount and thickness of the film-like retained austenite play an important role during the cyclic stress induced phase transformation.
基金supported by National Natural Science Foundation(No.30672546)Shanghai Municipal Committee of S & T(No.0652nm013)National Key Basic Research Program of China(No.2007CB935800)
文摘A general method was described to synthesize a highly hydrophobic cyclic peptide,cyclo[LWLWLWLWLQ]where underlines indicate D-configuration of the amino acid,by a two-step solid-phase/solution synthesis strategy.The linear decapeptide was assembled by standard Boc chemistry on solid-phase and subsequently cyclized in solution with high efficiency and reproducibility. In subsequent purification by semi-preparative HPLC,50%(v/v) DMF/H_2O was employed as the solvent to overcome the difficulty of solubilization...
文摘Low cycle fatigue tests under plastic strain control were carried out with a dual-phase steel containing 23 Vol.-％ martensite. Specimens hardened rapidly at first few cycles followed by a slight softening to saturation stages when cycled at higher strain amplitudes, whereas at lower strain amplitudes the specimens presented continually hardening for a long time until saturation. TEM examination of the saturation dislocation structures show that clusters, parallel walls and cells were found at low, medium and high strain amplitude, respectively. It also has been found that the martensite/ferrite interfaces did not affect the dislocation structures signi- ficantly when a specimen was fatigued at lower strain amplitude. However, the dislocation struc- ture adjacent to the two-phase boundary is dif- ferent to some extent from that in the remote regions in the ferrite when a higher strain amplitude is applied.
基金the National Natural Science Foundation of China (No.19872079)the Fund of the Ministry of Education of China.
文摘Based on the assumption that a representative element of apearlitic steel is an aggregate of numerous spherical pearliticcolonies with randomly distributed orientations, and that each colonyis com- posed of many parallel fine lamellas of ferrite andcementite, a description for the dual-phase pearlitic steel isobtained by making use of a microstructure-based constitutiveequation for a single dual-phase pearlitic colony and the Hill'sself-consistent scheme. The elastoplastic response of dual-phasepearlitic steel BS11 subjected to asymmetrically cyclic loading isanalyzed, and a comparison with the experimental results showssatisfacto- ry agreement. The non-proportional cyclic plasticity ofBS11 is also analyzed, in which stress develops along a semi-circlein a biaxial tension/compression and shear stress plane, as istypically experienced by the sur- face elements in rolling andsliding contact.
基金Project.20072032 was supported by the National Natural Science Foundation of China.
文摘Carboxycoumsrins were synthesized via the solid phase synthesis conviently. The resin bound cyclic malonic ester reacted with o-methoxy or o-hydroxybenzaldehydes. Then cyclization was processed under H2SO4 to afford the products in excellent purities and yields.
基金supported by the National Natural Science Foundation of China under Grant 62071364 and 62231027in part by the Key Research and Development Program of Shaanxi under Grant 2023-YBGY-249+1 种基金in part by the Key Research and Development Program of Guangxi under Grant 2022AB46002in part by the Fundamental Research Funds for the Central Universities under Grant KYFZ23001.
文摘Modulation recognition becomes unreliable at low signal-to-noise ratio(SNR)over fading channel.A novel method is proposed to recognize the digital modulated signals with frequency and phase offsets over multi-path fading channels in this paper.This method can overcome the effects of phase offset,Gaussian noise and multi-path fading.To achieve this,firstly,the characteristic parameters search is constructed based on the cyclostationarity of received signals,to overcome the phase offset,Gaussian white noise,and influence caused by multi-path fading.Then,the carrier frequency of the received signal is estimated,and the maximum characteristic parameter is searched around the integer multiple carriers and their vicinities.Finally,the modulation types of the received signal with frequency and phase offsets are classified using decision thresholds.Simulation results demonstrate that the performance of the proposed method is better than the traditional methods when SNR is over 5dB,and that the proposed method is robust to frequency and phase offsets over multipath channels.
基金supported by the Hong Kong University of Science and Technology and the National Natural Science Foundation of China (10902013)
文摘Bacterial flagellar filaments can undergo a polymorphic phase transition in both vitro and vivo environments. Each bacterial flagellar filament has 12 different helical forms which are macroscopically represented by different pitch lengths and helix radii. For external mechanical force induced filament phase transitions, there is so far only one experiment performed by Hotani in 1982, who showed a very beautiful cyclic phase transition phenomenon in his experiment on isolated flagellar filaments. In the present paper, we give a detailed mechanical analysis on Hotani＇s experiments. Through theoretical computations, we obtained a phase transition rule based on the phase transition mechanism. The theoretical analysis provides a foundation facilitating the establishment of phase transition theory for bacterial flagellar filaments.
基金supported by Agency for Science,Technology and Research(A∗Star),the Republic of Singapore,under the IAF-PP program‘Integrated large format hybrid manufacturing using wire-fed and powder-blown technology for LAAM process’(Grant No:A1893a0031).
文摘Globularαphases can significantly improve the ductility of titanium alloys.Cyclic heat treatment(CHT)has been proved to be an effective way to induce the formation of globularαphases inα+βtitanium alloy Ti-6Al-4V fabricated by laser aided additive manufacturing(LAAM).However,there is no prior research reporting methods for obtaining globularαphases in LAAM-built near-αtitanium alloys.This work investigated the cyclic heat treatment(CHT)procedures suitable for the LAAM-built near-αtitanium alloy Ti-6Al-2Sn-4Zr-2Mo(Ti6242)to attain the globularαphases.The results show that 980℃ is the most suitable upper temperature limit for CHT.However,it is difficult to achieve a high volume fraction of the globularαphases in the LAAM-built Ti6242 alloys through CHT,which is ascribed to the low composition gradient caused by moreα-stabilizing elements and fewerβ-stabilizing elements.The as-built sample demonstrated elongation of 6.3%,which is lower than the AMS 4919J standard(elongation≥10%).After 980℃ CHT and 980℃ CHT with solution heat-treatment,the formation of the globularαphases significantly increased the elongation to 13.5%and 12.9%,respectively.Although the mechanical strength is reduced after heat-treatment,the room-temperature tensile properties still exceed the AMS 4919J standard.Fractography examination showed that the as-built sample exhibited a mixed brittle and ductile fracture behavior,while the 980℃ CHT and 980℃ CHT with solution heat-treated samples displayed ductile fracture.
基金the National Natural Science Foundation of China(Project No.20072032)
文摘Resin-bound cyclic malonic ester l reacted with aryl isothiocynate, then was treated with bromine, followed by cleavage from the resin under perchloric acid to give benzothiazoles 4.
基金Sponsored by the National Basic Research Program (Grant No. 2007CB310601)the High Technology Research and Development Program of China(Grant No. 2007AA12Z338)
文摘A new high dynamic synchronization algorithm using cyclic spectral density was presented according to the theories of cyclic spectral density and its anti-interface and anti-noise properties.The closed forms of frequency error and phase error were obtained,and their performances were analyzed.The in-phase signal throw costas loop was normalized to obtain a cosine signal.Cyclic spectral density of the cosine signal of was computed to obtain the frequency error and the phase error and then results were put into NCO to synchronize.Finally,the performance of the presented algorithms was compared with the conventional algorithms by virtue of simulations,and the simulation results proved the correctness and the superiority of the new algorithms.
基金the support of the Key Program of National Natural Science Foundation of China(Grant No.52235005)the Natural Science Foundation of Hunan Province,China(Grant No.2023JJ30137).
文摘Owing to the special layer-by-layer deposition process of directed energy deposition(DED),columnar coarse grains,produced by cyclic reheating with intrinsic directional heat flow along the building direc-tion,are difficult to avoid.These grains result in strong anisotropic characteristics with poor mechanical properties,which restrict the application of DED products.This work proposes a novel fabrication strat-egy based on the cyclic-phase-transformation behavior,which can reduce the anisotropy and improve the mechanical properties of DED-printed stainless steel.Using this fabrication strategy,316 L powder(austenitic stainless steel)and 17-4PH powder(martensitic stainless steel)were mixed in different mass ratios to fabricate five types of DED-printed stainless steels.Among the five samples,P70(mixture of 70 wt%17-4PH powder and 30 wt%316 L powder)showed the weakest anisotropy and the best mechanical properties,which can be attributed to the cyclic phase transformation under cyclic reheating treatment and the transformation-induced plasticity(TRIP)effect over a wide range of strains,respectively.Com-pared with the pure 316 L printed material,the tensile test results of P70 showed that the yield strength(YS)and ultimate tensile strength(UTS)increased by 35.4%and 34.5%,respectively,whereas the uniform elongation(UE)and total elongation(TE)were improved by 63.9%and 31.4%,respectively.In addition,the strength-ductility balance(UTS×UE)increased by as much as 120.4%.The proposed fabrication strategy is expected to reduce the anisotropy in other materials that undergo cyclic-phase-transformation phe-nomena during additive manufacturing.
