A total coloring of a graph G with colors 1, 2, ..., t is called a cyclically interval total t-coloring if all colors are used, and the edges incident to each vertex v∈V(G) together with v are colored by (dG(v)+1) co...A total coloring of a graph G with colors 1, 2, ..., t is called a cyclically interval total t-coloring if all colors are used, and the edges incident to each vertex v∈V(G) together with v are colored by (dG(v)+1) consecutive colors modulo t, where dG(v) is the degree of the vertex v in G. The one point union ?of k-copies of cycle Cn is the graph obtained by taking v as a common vertex such that any two distinct cycles? and? are edge disjoint and do not have any vertex in common except v. In this paper, we study the cyclically interval total colorings of , where n≥3 and k≥2.展开更多
A total coloring of a graph G is a functionsuch that no adjacent vertices, edges, and no incident vertices and edges obtain the same color. A k-interval is a set of k consecutive integers. A cyclically interval total ...A total coloring of a graph G is a functionsuch that no adjacent vertices, edges, and no incident vertices and edges obtain the same color. A k-interval is a set of k consecutive integers. A cyclically interval total t-coloring of a graph G is a total coloring a of G with colors 1,2,...,t, such that at least one vertex or edge of G is colored by i,i=1,2,...,t, and for any, the set is a -interval, or is a -interval, where dG(x) is the degree of the vertex x in G. In this paper, we study the cyclically interval total colorings of cycles and middle graphs of cycles.展开更多
The characteristics and microstructural changes of cyclic softening in hot-working die steels 5CrNiMo and 5Cr2NiMoVSi were studied under strain controlled low-cycle fatigue.The re- sults show that the cyclic softening...The characteristics and microstructural changes of cyclic softening in hot-working die steels 5CrNiMo and 5Cr2NiMoVSi were studied under strain controlled low-cycle fatigue.The re- sults show that the cyclic softening is featured in both steels hardened in different conditions under the strain controlled amplitude range of Δε_t/2=0.6-1.8×10^(-2).The softening effect mainly occurs in some initial cycles and the stress amplitude varies slightly in the sequential cycles,i.e.the softening effect is minified.No obvious stress saturation phenomenon was ob- served during the whole cyclic deformation.The TEM analysis shows that the cyclic softening is related to heterogenity of plastic deformation.The softening of the tested steels is caused by the formation of the dislocation cell structure with low density and low internal stress,and by the fragmentation and redissolution of fine carbides into matrix.展开更多
A proper edge t-coloring of a graph G is a coloring of its edges with colors 1,2,???,t such that all colors are used, and no two adjacent edges receive the same color. A cyclically interval t-coloring of a graph G is ...A proper edge t-coloring of a graph G is a coloring of its edges with colors 1,2,???,t such that all colors are used, and no two adjacent edges receive the same color. A cyclically interval t-coloring of a graph G is a proper edge t-coloring of G such that for each its vertex x, either the set of colors used on edges incident to x or the set of colors not used on edges incident to x forms an interval of integers. For an arbitrary simple cycle, all possible values of t are found, for which the graph has a cyclically interval t-coloring.展开更多
The prediction of fatigue life of metallic alloys is justly accepted as one of the most important phenomena in the field of metallurgical and mechanical engineering.At elevated temperatures,oxidation of the surfaces h...The prediction of fatigue life of metallic alloys is justly accepted as one of the most important phenomena in the field of metallurgical and mechanical engineering.At elevated temperatures,oxidation of the surfaces has an effective role in the fatigue strength and ductility of the alloys.In the present work,the effect of prior cyclic oxidation on the high temperature low cycle fatigue(HTLCF)properties of nickel-based superalloy Rene®80 has been assessed in the uncoated state and in the Pt-aluminide(Pt-Al)coated condition at 930℃.To apply cyclic oxidation,simulation of engine thermal exposure was carried out by exposing coated and uncoated fatigue specimens in the burner rig(120 cycles at 1100℃).The cyclic oxidation procedure led to a changing in the coating microstructure from the dual-phase(ξ-PtAl_(2)+β-(Ni,Pt)Al)to single phase(β-(Ni,Pt)Al).Results of HTLCF tests showed an improvement in the HTLCF life around 11.5%in the unexposed coated specimen(pre-cyclic oxidation)as compared to unexposed bare specimen,while this rise for exposed coated specimen(post-cyclic oxidation)was only 5%.Although a mixed mode fracture morphology(ductile and brittle)was observed on the fracture surfaces of failed specimens,the wider regions of brittle fracture belonged to exposed coated/uncoated ones.展开更多
The constitutive equation under the low-cycle fatigue （LCF） was discussed, and a two-dimensional （2-D） model for simulating fatigue crack extension was put forward in order to propose a new cyclic J-integral. The ...The constitutive equation under the low-cycle fatigue （LCF） was discussed, and a two-dimensional （2-D） model for simulating fatigue crack extension was put forward in order to propose a new cyclic J-integral. The definition, primary characteristics, physical interpretations and numerical evaluation of the new parameter were investigated in detail. Moreover, the new cyclic J-integral for LCF behaviors was validated by the compact tension （CT） specimens. Results show that the calculated values of the new parameter can correlate well with LCF crack growth rate, during constant-amplitude loading. In addition, the phenomenon of fatigue retardation was explained through the viewpoint of energy based on the concept of the new parameter.展开更多
In chloroplast, there were two pathways involved in the cyclic electron flow around photosystem 1 （PS 1）. One was the NADH dehydrogenase （NDH）-dependent flow and the other was the ferredoxin quinone reductase-depe...In chloroplast, there were two pathways involved in the cyclic electron flow around photosystem 1 （PS 1）. One was the NADH dehydrogenase （NDH）-dependent flow and the other was the ferredoxin quinone reductase-dependent flow. It was proposed that the NDH-dependent cyclic electron flow around PSI was related to the xanthophyll cycle-dependent non-photochemical quenching （NPQ） at chilling temperature under low irradiance （CL）. The function of the chloroplastic cyclic electron flow around PS 1 was examined by comparing sweet pepper （Capsicum annuum L.） control with its antimycin A （AA）-fed leaves upon exposure to CL stress. During CL stress, the maximum photochemical efficiency of PS2 （Fv/Fm） decreased markedly in both controls and AA-fed leaves, and P700＋ was also lower in AA-fed leaves than in controls. These results implied that cyclic electron flow around PS 1 functioned to protect the photosynthetic apparatus from CL stress. Under such stress, NPQ and PS2-driven electron transport rate were different between AA-fed leaves and controls. The lower NPQ in AA-fed leaves might be related to an inefficient proton gradient across thylakoid membranes （ApH） because of inhibiting cyclic electron flow around PS 1 under CL stress.展开更多
Fatigue failure is a main failure mode for magnesium and other alloys. It is beneficial for fatigue design and fatigue life improvement to investigate the low cycle fatigue behavior of magnesium alloys. In order to in...Fatigue failure is a main failure mode for magnesium and other alloys. It is beneficial for fatigue design and fatigue life improvement to investigate the low cycle fatigue behavior of magnesium alloys. In order to investigate the low cycle fatigue behavior of die cast Mg-AI-Mn-Ce magnesium alloy, the strain controlled fatigue experiments were performed at room temperature and fatigue fracture surfaces of specimens were observed with scanning election microscopy for the alloys under die-cast and aged states. Cyclic stress response curves, strain amplitude versus reversals to failure curve, total strain amplitude versus fatigue life curves and cyclic stress-strain curves of Mg-AI-Mn-Ce alloys were analyzed. The results show that the Mg-AI-Mn-Ce alloys under die-cast （F） and aged （T5） states exhibit cyclic strain hardening under the applied total strain amplitudes, and aging treatment could greatly increase the cyclic stress amplitudes of die cast Mg-AI-Mn-Ce alloys. The relationships between the plastic strain amplitude, the elastic strain amplitude and reversals to failure of Mg-AI-Mn-Ce magnesium alloy under different treatment states could be described by Coffin-Manson and Basquin equations, respectively. Observations on the fatigue fracture surface of specimens reveal that the fatigue cracks initiate on the surface of specimens and propagate transgranularly.展开更多
Fatigue failure is one of the main failure forms of Al-Si-Cu-Mg aluminum alloys. To feature their mechanical aspect of fatigue behavior, the low-cycle fatigue behavior of permanent mold cast and die-cast AI-Si- Cu-Mg ...Fatigue failure is one of the main failure forms of Al-Si-Cu-Mg aluminum alloys. To feature their mechanical aspect of fatigue behavior, the low-cycle fatigue behavior of permanent mold cast and die-cast AI-Si- Cu-Mg alloys at room temperature was investigated. The experimental results show that both permanent mold cast and die-cast AI-Si-Cu-Mg alloys mainly exhibit cyclic strain hardening. At the same total strain amplitude, the diecast AI-Si-Cu-Mg alloy shows higher cyclic deformation resistance and longer fatigue life than does the permanent mold cast AI-Si-Cu-Mg alloy. The relationship between both elastic and plastic strain amplitudes with reversals to failure shows a monotonic linear behavior, and can be described by the Basquin and Coffin-Manson equations, respectively.展开更多
An investigation was conducted to examine the low cycle symmetric push-pull fatigue behaviour of the Cr-Mn-N dual-phase stainless steel.Two groups of specimens,A and B, were used,they were solution treated at 1050 and...An investigation was conducted to examine the low cycle symmetric push-pull fatigue behaviour of the Cr-Mn-N dual-phase stainless steel.Two groups of specimens,A and B, were used,they were solution treated at 1050 and 1250℃,respectively.The.fatigue life of group A is almost twice as long as that of group B under the same total strain amplitude.The energy loss during the fatigue tests and the mophology of the fracture surfaces have been stu- died and discussed.展开更多
文摘A total coloring of a graph G with colors 1, 2, ..., t is called a cyclically interval total t-coloring if all colors are used, and the edges incident to each vertex v∈V(G) together with v are colored by (dG(v)+1) consecutive colors modulo t, where dG(v) is the degree of the vertex v in G. The one point union ?of k-copies of cycle Cn is the graph obtained by taking v as a common vertex such that any two distinct cycles? and? are edge disjoint and do not have any vertex in common except v. In this paper, we study the cyclically interval total colorings of , where n≥3 and k≥2.
文摘A total coloring of a graph G is a functionsuch that no adjacent vertices, edges, and no incident vertices and edges obtain the same color. A k-interval is a set of k consecutive integers. A cyclically interval total t-coloring of a graph G is a total coloring a of G with colors 1,2,...,t, such that at least one vertex or edge of G is colored by i,i=1,2,...,t, and for any, the set is a -interval, or is a -interval, where dG(x) is the degree of the vertex x in G. In this paper, we study the cyclically interval total colorings of cycles and middle graphs of cycles.
文摘The characteristics and microstructural changes of cyclic softening in hot-working die steels 5CrNiMo and 5Cr2NiMoVSi were studied under strain controlled low-cycle fatigue.The re- sults show that the cyclic softening is featured in both steels hardened in different conditions under the strain controlled amplitude range of Δε_t/2=0.6-1.8×10^(-2).The softening effect mainly occurs in some initial cycles and the stress amplitude varies slightly in the sequential cycles,i.e.the softening effect is minified.No obvious stress saturation phenomenon was ob- served during the whole cyclic deformation.The TEM analysis shows that the cyclic softening is related to heterogenity of plastic deformation.The softening of the tested steels is caused by the formation of the dislocation cell structure with low density and low internal stress,and by the fragmentation and redissolution of fine carbides into matrix.
文摘A proper edge t-coloring of a graph G is a coloring of its edges with colors 1,2,???,t such that all colors are used, and no two adjacent edges receive the same color. A cyclically interval t-coloring of a graph G is a proper edge t-coloring of G such that for each its vertex x, either the set of colors used on edges incident to x or the set of colors not used on edges incident to x forms an interval of integers. For an arbitrary simple cycle, all possible values of t are found, for which the graph has a cyclically interval t-coloring.
文摘The prediction of fatigue life of metallic alloys is justly accepted as one of the most important phenomena in the field of metallurgical and mechanical engineering.At elevated temperatures,oxidation of the surfaces has an effective role in the fatigue strength and ductility of the alloys.In the present work,the effect of prior cyclic oxidation on the high temperature low cycle fatigue(HTLCF)properties of nickel-based superalloy Rene®80 has been assessed in the uncoated state and in the Pt-aluminide(Pt-Al)coated condition at 930℃.To apply cyclic oxidation,simulation of engine thermal exposure was carried out by exposing coated and uncoated fatigue specimens in the burner rig(120 cycles at 1100℃).The cyclic oxidation procedure led to a changing in the coating microstructure from the dual-phase(ξ-PtAl_(2)+β-(Ni,Pt)Al)to single phase(β-(Ni,Pt)Al).Results of HTLCF tests showed an improvement in the HTLCF life around 11.5%in the unexposed coated specimen(pre-cyclic oxidation)as compared to unexposed bare specimen,while this rise for exposed coated specimen(post-cyclic oxidation)was only 5%.Although a mixed mode fracture morphology(ductile and brittle)was observed on the fracture surfaces of failed specimens,the wider regions of brittle fracture belonged to exposed coated/uncoated ones.
基金Project supported by the Municipal Key Subject Program of Shanghai (No.Y0103)
文摘The constitutive equation under the low-cycle fatigue （LCF） was discussed, and a two-dimensional （2-D） model for simulating fatigue crack extension was put forward in order to propose a new cyclic J-integral. The definition, primary characteristics, physical interpretations and numerical evaluation of the new parameter were investigated in detail. Moreover, the new cyclic J-integral for LCF behaviors was validated by the compact tension （CT） specimens. Results show that the calculated values of the new parameter can correlate well with LCF crack growth rate, during constant-amplitude loading. In addition, the phenomenon of fatigue retardation was explained through the viewpoint of energy based on the concept of the new parameter.
基金supported by the National Natural Science Foundation of China(30571126)the Scientific Research Encouragement Foundation for 0utstanding Young and Middle Scientist of Shandong Province(2005BS06003)the open project from Key Laboratory of Crop Biology of Shandong Province,China.
文摘In chloroplast, there were two pathways involved in the cyclic electron flow around photosystem 1 （PS 1）. One was the NADH dehydrogenase （NDH）-dependent flow and the other was the ferredoxin quinone reductase-dependent flow. It was proposed that the NDH-dependent cyclic electron flow around PSI was related to the xanthophyll cycle-dependent non-photochemical quenching （NPQ） at chilling temperature under low irradiance （CL）. The function of the chloroplastic cyclic electron flow around PS 1 was examined by comparing sweet pepper （Capsicum annuum L.） control with its antimycin A （AA）-fed leaves upon exposure to CL stress. During CL stress, the maximum photochemical efficiency of PS2 （Fv/Fm） decreased markedly in both controls and AA-fed leaves, and P700＋ was also lower in AA-fed leaves than in controls. These results implied that cyclic electron flow around PS 1 functioned to protect the photosynthetic apparatus from CL stress. Under such stress, NPQ and PS2-driven electron transport rate were different between AA-fed leaves and controls. The lower NPQ in AA-fed leaves might be related to an inefficient proton gradient across thylakoid membranes （ApH） because of inhibiting cyclic electron flow around PS 1 under CL stress.
基金financially supported by the Science and Technology Research Project of Liaoning Province Education Department(L2012038)
文摘Fatigue failure is a main failure mode for magnesium and other alloys. It is beneficial for fatigue design and fatigue life improvement to investigate the low cycle fatigue behavior of magnesium alloys. In order to investigate the low cycle fatigue behavior of die cast Mg-AI-Mn-Ce magnesium alloy, the strain controlled fatigue experiments were performed at room temperature and fatigue fracture surfaces of specimens were observed with scanning election microscopy for the alloys under die-cast and aged states. Cyclic stress response curves, strain amplitude versus reversals to failure curve, total strain amplitude versus fatigue life curves and cyclic stress-strain curves of Mg-AI-Mn-Ce alloys were analyzed. The results show that the Mg-AI-Mn-Ce alloys under die-cast （F） and aged （T5） states exhibit cyclic strain hardening under the applied total strain amplitudes, and aging treatment could greatly increase the cyclic stress amplitudes of die cast Mg-AI-Mn-Ce alloys. The relationships between the plastic strain amplitude, the elastic strain amplitude and reversals to failure of Mg-AI-Mn-Ce magnesium alloy under different treatment states could be described by Coffin-Manson and Basquin equations, respectively. Observations on the fatigue fracture surface of specimens reveal that the fatigue cracks initiate on the surface of specimens and propagate transgranularly.
文摘Fatigue failure is one of the main failure forms of Al-Si-Cu-Mg aluminum alloys. To feature their mechanical aspect of fatigue behavior, the low-cycle fatigue behavior of permanent mold cast and die-cast AI-Si- Cu-Mg alloys at room temperature was investigated. The experimental results show that both permanent mold cast and die-cast AI-Si-Cu-Mg alloys mainly exhibit cyclic strain hardening. At the same total strain amplitude, the diecast AI-Si-Cu-Mg alloy shows higher cyclic deformation resistance and longer fatigue life than does the permanent mold cast AI-Si-Cu-Mg alloy. The relationship between both elastic and plastic strain amplitudes with reversals to failure shows a monotonic linear behavior, and can be described by the Basquin and Coffin-Manson equations, respectively.
文摘An investigation was conducted to examine the low cycle symmetric push-pull fatigue behaviour of the Cr-Mn-N dual-phase stainless steel.Two groups of specimens,A and B, were used,they were solution treated at 1050 and 1250℃,respectively.The.fatigue life of group A is almost twice as long as that of group B under the same total strain amplitude.The energy loss during the fatigue tests and the mophology of the fracture surfaces have been stu- died and discussed.
基金supported by National Natural Science Foundation of China,China(No.52101138)Natural Science Foundation of Hubei Province,China(No.2020CFB259)+7 种基金Shenzhen Science and Technology Program,China(No.JCYJ20220530160813032)State Key Lab of Advanced Metals and Materials,China(No.2020-Z01)State Key Laboratory for Mechanical Behavior of Materials,China(No.20202205)Guangdong Basic and Applied Basic Research Foundation,China(Nos.2020A1515110531,2021A1515111122)State Key Laboratory of Materials Processing and Die&Mold Technology,Huazhong University of Science and Technology,China(No.P2021-021)support from the National Natural Science Foundation of China(No.12004294)National Youth Talents Programsupport by Center for Alloy Innovation and Design(CAID)and HPC platform of Xi’an Jiaotong University。
