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Phase field simulation of interatomic potentials for double phase competition during early stage precipitation
WeiPing Dong,YongXin Wang,Kun Yang,Zheng Chen,YanLi Lu
Chinese Science Bulletin , 2011, DOI: 10.1007/s11434-011-4407-1
Abstract: Phase field model was employed to study the variations of interatomic potentials of Ni3Al (L12 phase) and Ni3V (DO22 phase) as a function of temperature and concentration. The long-range order (LRO) parameter related interatomic potentials equations formulated by Khachaturyan were utilized to establish the inversion equations for L12 and DO22 phases, with which interatomic potentials could be calculated. The interatomic potentials of Ni-Al and Ni-V exhibited approximately linear increases and decreases, individually, with enhanced Al concentration. Substituting the inverted interatomic potentials into the microscopic phase field equations led to three cases of precipitation sequence: the DO22 phase preceded L12 phase precipitating at the interatomic potentials of Ni-V > Ni-Al; the vice cases; and two phases precipitated simultaneously at interatomic potentials of Ni-V and Ni-Al were equal.
A phase field study for influence of elastic energy on L10→L12 transient ordering in Ni75Al17Zn8
Yan Zhao,Zheng Chen,YongXin Wang,MingYi Zhang,Jing Zhang
Chinese Science Bulletin , 2010, DOI: 10.1007/s11434-009-3740-0
Abstract: The influence of the elastic energy on L10→L12 transient ordering transformation was investigated by microscopic phase field method. It is found that there are three stages experienced in atomic ordering: solute clustering+L10 short range ordering → L10 long range ordering → L12 long range ordering. Before the formation of the high ordered L12 phase, it has firstly taken place the transformation from matrix to L10 phase, and then held the L10→ L12 secondary transformation. Elastic energy is proved to take little effect on the stage of short range ordering, but as the elastic energy is multiplied, it obviously shortened the course of the solute clustering, and speeded up the proceeding of the L10 long range ordering transition. Accordingly, the increased elastic energy also strengthens the single crystalline directionality of L10 phase projecting on 2D plane and makes the ordered degree of Al and Zn atoms enhanced. With the temperature elevation, Al’s and Zn’s ordered degree decreased in L10 phase.
Simulation of Microstructure Evolution of Ni75Al2.9V22.1 Alloy with Progressive Aging Mechanisms
Yongsheng LI,Zheng CHEN,Qingbo LAI,Yongxin WANG,
材料科学技术学报 , 2008,
Abstract:
Vitreous Incarceration in Patients Undergoing Second 20-Gauge Pars Plana Vitrectomy for Recurrent Retinal Detachment
Yongxin Zheng,Haotian Lin,Wen Liu,Dandan Wang
ISRN Ophthalmology , 2011, DOI: 10.5402/2011/456191
Abstract:
Reasoning with Ontology Model Based on Jena  [PDF]
Jing WU, Yongxin HUANG
Intelligent Information Management (IIM) , 2009, DOI: 10.4236/iim.2009.11005
Abstract: As the core of knowledge representation, reasoning plays an important role in the Semantic Web. In this paper, introduce Description Logic as the theoretical foundation of reasoning in the Semantic Web and OWL which needs to be expressive enough for representing knowledge and computationally tractable for inference of large-scale applications. Then construct an ontology model depicted with OWL by protégé and Jena API , and also prove the validity of reasoning with the model.
Microscopic Phase-field Simulation of Competition Mechanism Between L12 and D022 Structure in Ni-Cr-Al Alloy
Zhong CHU,Zheng CHEN,Yongxin WANG,Yanli LU,Yongsheng LI,
Zhong,CHU,Zheng,CHEN,Yongxin,WANG,Yanli,LU,Yongsheng,LI
材料科学技术学报 , 2006,
Abstract: Simulations are performed on temporal evolution of atom morphology and ordering parameters of Ni-14.5Cr-16.5 Al alloy during early precipitation process at different temperatures based on microscopic phase-field theory; the relationship between precipitation sequence and mechanism of L12 and D022 structure and precipitation temperature are illuminated. The nonstoichiometric ordered L12 phases appear first with congruent ordering spinodal decomposition mechanism which is then followed by precipitation of D022 phases at ordering domain boundaries of L12 phases by spinodal decomposition mechanism at 1073 K and 1223 K. The nonstoichiometric L12 phases transform to stoichiometric ordering phases gradually. The incubation period of L12 and D022 phases is shorter at 1073 K than that 1223 K, and growth speed is higher at 1073 K. At 1373 K, L12 and D022 phases appear simultaneously by non-classical nucleation and growth mechanism. After that the particles of D022 phases diminish and disappear gradually; L12 phases grow and single L12 phases are remained at last.
Genistein Inhibition of Topoisomerase IIα Expression Participated by Sp1 and Sp3 in HeLa Cell
Najing Zhou,Yunli Yan,Wenling Li,Yanling Wang,Lifen Zheng,Shuo Han,Yongxin Yan,Yunzhi Li
International Journal of Molecular Sciences , 2009, DOI: 10.3390/ijms10073255
Abstract: Genistein (4′, 5, 7-trihydroxyisoflavone) is an isoflavone compound obtained from plants that has potential applications in cancer therapy. However, the molecular mechanism of the action of genistein on cancer cell apoptosis is not well known. In this study, we investigated the effect of genistein on topoisomerase II-α (Topo IIα), an important protein involved in the processes of DNA replication and cell proliferation. The results revealed that inhibition of Topo IIα expression through the regulation of Specificity protein 1 and Specificity protein 3 may be one of the reasons for genistein’s induction of HeLa cell apoptosis.
A MICROSCOPIC PHASE–FIELD STUDY FOR THE INFLUENCE OF ORDERING ENERGY ON Cr SUBSTITUTION BEHAVIOR IN Ni75Al15Cr10 ALLOY
ZHAO Yan,CHEN Zheng,WANG Yongxin,HUO Jinliang,ZHANG Lipeng,ZHANG Mingyi,
金属学报 , 2009,
Abstract: The microscopic phase–field model based on long range order (LRO) method was proposed to study Cr substitution behavior in Ni75Al15Cr10 alloy aged at 1073 K. This has been demonstrated by short range order (SRO) methods and experiments such as pseudo–potential, Monte Carlo method and Rutherford back scattering analysis (RBS). Adding ±4 meV to the ordering energy of Ni–Al, Ni–Cr and Al–Cr in 1st—4th nearest–neighborhoods is used to describe the influence of potential field on substitution. On the analysis of atomic images, the order parameters and Cr occupation probabilities, results show that there are coexisted Ni–Al anti–site and Cr substitution for Ni and Al in L12 ordered phase, and Cr substitution occurs much more often than Ni–Al anti–site. As the ordering energies of Ni–Al and Ni–Cr in 1st and 3rd nearest–neighborhoods increase, there is a more increasing tendency of substitution of Cr for Al than for Ni. For the 2nd and 4th nearest–neighborhoods, the ordering energy makes the tendency of substitution of Cr for Ni increase. Otherwise, with the 1st and 3rd nearest–neighborhoods ordering energies of Al–Cr increasing, the tendency of substitution of Cr increases for Ni but decreases for Al, which is opposite to the cases for the 2nd and 4th nearest–neighborhoods.
Retrogression Mechanisms Simulations of Al--Li Alloys
Al-Li合金回归机制的计算机模拟
JIANG Zhihua,WANG Yongxin,CHEN Zheng,
江志华,王永欣,陈 铮
金属学报 , 2004,
Abstract: The dissolution kinetics ordered precipitations in a disordered matrix during retrogression heat treatment was investigated on atomic scale using computer simulations based on microscopic diffusion equations (Langevin equation) with the discrete format. The evolutions of atomic pictures and order parameter profiles with time were analyzed, and the retrogression mechanisms of Al--Li alloys were further studied. In the course of retrogression, it is firstly proved that the evolutions phase in a disordered matrix is in the order; and then the retrogression of alloys at metastable field tends to the anti--process of the phase precipitation of alloys at unstable field, while retrogression of alloys at unstable field tend to the anti--process of the phase precipitation of alloys at metastable field.
MICROSCOPIC PHASE–FIELD METHOD SIMULATION FOR THE IN SITU TRANSFORMATION OF L10 PHASE AND L12 PHASE STRUCTURE
MIAO Shufang,CHEN Zheng,WANG Yongxin,XU Cong,MA Rui,ZHANG Mingyi,
金属学报 , 2009,
Abstract: As a Ni3Al precipitation strengthening alloy, Ni–Cr–Al alloy is one of typical structural materials applied in high temperatures. Much work has been done concerning its structure transformation from fcc to L12 during the process of ordering and phase separation. However, the study so far we know on the phase transformation in very early precipitation stage, especially on the phase transformation of unstable pre–precipitation phase, was not yet sufficient. Microscopic phase–filed method is used for describing the temporal and spatial evolution of atomic site in lattice. This method is employed to study the pre–precipitation during the structure transformation from fcc to L12 in Ni80Al13Cr7 alloy in this paper. The relationship between the occupation probability changes in Al and Cr atoms on (100) and (200) planes respectively and structure evolution of Ni3(Al, Cr) will be inveatigated. The simulation results demonstrate that at in very early aging stage, the composition order parameters of Al and Cr atoms keep unchange on both (100) and (200) planes. However their long range order parameters are equal in these two planes and gradually increase with aging time until the first in situ transformation by congruent ordering at that time the L10 pre–precipitation phase with low long range order is formed. By prolonging aging time, their long range order parameters continue increase once they attain to the respective certain values, the composition order parameters and the long range order parameters of Al and Cr atoms on (100) plane become increasing rapidly but those on (200) plane decreasing quickly, The second in situ transformation occurs and the L10 is gradually transformed into L12.
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