An analytical method to investigate the morphological evolution of the cellular mi-crostructure is explored and proposed. The method is essentially based on the Es-helby 's micromechanics theory, and it is extende...An analytical method to investigate the morphological evolution of the cellular mi-crostructure is explored and proposed. The method is essentially based on the Es-helby 's micromechanics theory, and it is extended so as to be applied for a material system containing inclusions with high volume fraction, by employing the average stress field approximation by Mori and Tanaka. The proposed method enables us to discuss a stable shape of precipitate in the material system, which must be influenced by many factors: e.g., volume fraction of precipitate; Young's modulus ratio and lattice misfit between matrix and precipitate; external stress field in multiaxial state; and heterogeneity of plastic strain between matrix and precipitate. A series of numerical calculations were summarized on stable shape maps. The application of the method to predict the γ' rafting in superalloys during creep showed that the heterogeneity of plastic strain between matrix and precipitates may play a significant role in the shape stability of the precipitate. Furthermore, it was shown that the method was successfully applied to estimate the morphology of the cellular microstructure formed in CMSX-4 single crystal Ni-based superalloy.展开更多
A new numerical model is developed using a Cellular Automata (CA) method to study the liquid-phase dissolution behavior of gap-filler powder particles in interlayer powder mixture during transient liquid phase (TLP) b...A new numerical model is developed using a Cellular Automata (CA) method to study the liquid-phase dissolution behavior of gap-filler powder particles in interlayer powder mixture during transient liquid phase (TLP) bonding process. The model prediction of microstructural evolution in TLP joint between single crystal substrates show that formation of misoriented stray-grains results from incomplete liquation of the gap-filler powder particles. In contrast to what is generally assumed and reported, numerical calculations coupled with experimental verification show that under properly selected process parameters, complete melting of the gap-filler powder particles is possible. This is imperative to prevent the formation of misoriented stray-grains and maintain single crystallinity during TLP bonding of single crystal materials. The dependence of complete melting of the gap-filler particles on salient TLP bonding parameters are analyzed and discussed.展开更多
This paper deals with the technology of computer graphics and its application in ana-lyzing complex nonlinear proceas. We have investigated metal crystallization, which is a complexnonlinear process and is difficult t...This paper deals with the technology of computer graphics and its application in ana-lyzing complex nonlinear proceas. We have investigated metal crystallization, which is a complexnonlinear process and is difficult to analyze by using the conventional numerical rnethod to estab-lish a complete and accurate mathematical modcl. Based on the principles of metal crystallizationand Cellular Automata algorithm, the author separated, in time and space, the process ofccystailization into periodically growing airays, so that the simulation of metal crystallization isrealized.展开更多
It is clarified by experimental examination and theoretical analysis that the transformation of crystal moorphology of the eutectic Al-Cu alloy composite-in-situ seems to be judged by not only the constitutional super...It is clarified by experimental examination and theoretical analysis that the transformation of crystal moorphology of the eutectic Al-Cu alloy composite-in-situ seems to be judged by not only the constitutional supercooling proposed in previous literatures but also the supercooling due to the effect of curved surfaces at the solidifying from.The greater entropy of fusion and the tendency to faceted face are important features of the non-metallic phase,which may con- tribute to the leading,role of the phase during solidification.It might be the change of leading phase that changes the morphology of crystals.展开更多
Dinoflagellates nuclei allow for liquid crystalline characterization without core histones. In this study, nuclei were isolated from the athecate Karenia dinoflagellate species with minimum destruction to their native...Dinoflagellates nuclei allow for liquid crystalline characterization without core histones. In this study, nuclei were isolated from the athecate Karenia dinoflagellate species with minimum destruction to their native structure during preparation procedures. The liquid crystalline nuclei were studied by microscopy techniques of Metripol birefringence microscopy, Confocal Laser Scanning Microscopy (CLSM) and synchrotron radiation-based hard X-ray Microscopy with computed tomography, respectively. The 3D reconstruction techniques of hard X-ray tomography and CLSM were also discussed. The important biophysical parameters of the interspaces between chromosomes, nuclear surface areas and chromosome-occupied volumes were calculated from a 3D rendering of a reconstructed nucleus. The results of calculated average chromosomal DNA concentration of dinoflagellate was consistent with the concentration which can spontaneously assemble into the cholesteric liquid crystal phase in vitro.展开更多
A novel approach to modelling phase-transition processes in phase change materials used for optical and electrical data storage applications is presented. The model is based on a cellular automaton （CA） approach to ...A novel approach to modelling phase-transition processes in phase change materials used for optical and electrical data storage applications is presented. The model is based on a cellular automaton （CA） approach to predict crystallization behaviour that is linked to thermal and electrical simulations to enable the study of the data writing and erasing processes. The CA approach is shown to be able to predict the evolution of the microstructure during the rapid heating and cooling cycles pertinent to data storage technology, and maps crystallization behaviour on the nanoscale. A simple example based on possible future nonvolatile phase-change random access solid-state memory is presented.展开更多
There are some different opinions on the formation of striped migmatite. Many striped migmatites are distributed around the plutonic rocks in the core of hot dome in nature. This shows that the pressure of intrusive r...There are some different opinions on the formation of striped migmatite. Many striped migmatites are distributed around the plutonic rocks in the core of hot dome in nature. This shows that the pressure of intrusive rocks to wall rocks must play an important role in the formation of stripes. This paper, at first, discusses the effects of directional pressure (i. e. compressive stress from intrusive rock to wall rock) on particle migration and crystallization, and the physical mechanism of Ostwald maturation and its adjusting effect in crystalline growth. And then, on the basic principles of physics and chemistry, we lay down the stochastic evolutional rules of the formation of crystal nucleus, diffusion, crystallization and dissolution of leucosome (melt) particles; and,neglecting other restrictive conditions, we build an idealizedly simplified two-dimensional model of stochastic cellular automaton for the recrystallization of metamorphic rock under directional pressure, and realize it by writing a program of Windows on PC. Theoretical analyses and computer simulations show that, at the beginning, the free particles of leucosome are initially even distributed in the system and form many crystal nucleus ; then, the anisotropies of diffusion, crystallization and dissolution caused by the directional pressure together with the mechanisms of Ostwald maturation can make the nucleus successively grow to form lenses, unevenly disconnected stripes, and layer-stripe structure, which correspond to low, medium and high grades of metamorphism and migmatization, respectively; that is, the effect of the pressure of intrusive rock to wall rock alone can form streaked structure in migmatite. Moreover, cellular automaton, adopted in this paper, is a kind of discrete and local grid dynamic model, and is extremely suitable for simulating the evolution of spatiotemporal structure of real systems and analyzing micro-mechanism creating complex macro-phenomenon. We believe that cellular automata will have broad applications in the geosciences which is full of complicated natural phenomena.展开更多
基金supported by the Ministry of Education,Japan,as Grant-in-Aid for Scientific Research(No.12650072 and 15360046)are greatly acknowledged
文摘An analytical method to investigate the morphological evolution of the cellular mi-crostructure is explored and proposed. The method is essentially based on the Es-helby 's micromechanics theory, and it is extended so as to be applied for a material system containing inclusions with high volume fraction, by employing the average stress field approximation by Mori and Tanaka. The proposed method enables us to discuss a stable shape of precipitate in the material system, which must be influenced by many factors: e.g., volume fraction of precipitate; Young's modulus ratio and lattice misfit between matrix and precipitate; external stress field in multiaxial state; and heterogeneity of plastic strain between matrix and precipitate. A series of numerical calculations were summarized on stable shape maps. The application of the method to predict the γ' rafting in superalloys during creep showed that the heterogeneity of plastic strain between matrix and precipitates may play a significant role in the shape stability of the precipitate. Furthermore, it was shown that the method was successfully applied to estimate the morphology of the cellular microstructure formed in CMSX-4 single crystal Ni-based superalloy.
文摘A new numerical model is developed using a Cellular Automata (CA) method to study the liquid-phase dissolution behavior of gap-filler powder particles in interlayer powder mixture during transient liquid phase (TLP) bonding process. The model prediction of microstructural evolution in TLP joint between single crystal substrates show that formation of misoriented stray-grains results from incomplete liquation of the gap-filler powder particles. In contrast to what is generally assumed and reported, numerical calculations coupled with experimental verification show that under properly selected process parameters, complete melting of the gap-filler powder particles is possible. This is imperative to prevent the formation of misoriented stray-grains and maintain single crystallinity during TLP bonding of single crystal materials. The dependence of complete melting of the gap-filler particles on salient TLP bonding parameters are analyzed and discussed.
文摘This paper deals with the technology of computer graphics and its application in ana-lyzing complex nonlinear proceas. We have investigated metal crystallization, which is a complexnonlinear process and is difficult to analyze by using the conventional numerical rnethod to estab-lish a complete and accurate mathematical modcl. Based on the principles of metal crystallizationand Cellular Automata algorithm, the author separated, in time and space, the process ofccystailization into periodically growing airays, so that the simulation of metal crystallization isrealized.
文摘It is clarified by experimental examination and theoretical analysis that the transformation of crystal moorphology of the eutectic Al-Cu alloy composite-in-situ seems to be judged by not only the constitutional supercooling proposed in previous literatures but also the supercooling due to the effect of curved surfaces at the solidifying from.The greater entropy of fusion and the tendency to faceted face are important features of the non-metallic phase,which may con- tribute to the leading,role of the phase during solidification.It might be the change of leading phase that changes the morphology of crystals.
文摘Dinoflagellates nuclei allow for liquid crystalline characterization without core histones. In this study, nuclei were isolated from the athecate Karenia dinoflagellate species with minimum destruction to their native structure during preparation procedures. The liquid crystalline nuclei were studied by microscopy techniques of Metripol birefringence microscopy, Confocal Laser Scanning Microscopy (CLSM) and synchrotron radiation-based hard X-ray Microscopy with computed tomography, respectively. The 3D reconstruction techniques of hard X-ray tomography and CLSM were also discussed. The important biophysical parameters of the interspaces between chromosomes, nuclear surface areas and chromosome-occupied volumes were calculated from a 3D rendering of a reconstructed nucleus. The results of calculated average chromosomal DNA concentration of dinoflagellate was consistent with the concentration which can spontaneously assemble into the cholesteric liquid crystal phase in vitro.
基金The authors acknowledge the support of the EU Framework 5 programme in supporting this work un-der the auspices of the PC-RAM project (IST-2001-32557).
文摘A novel approach to modelling phase-transition processes in phase change materials used for optical and electrical data storage applications is presented. The model is based on a cellular automaton （CA） approach to predict crystallization behaviour that is linked to thermal and electrical simulations to enable the study of the data writing and erasing processes. The CA approach is shown to be able to predict the evolution of the microstructure during the rapid heating and cooling cycles pertinent to data storage technology, and maps crystallization behaviour on the nanoscale. A simple example based on possible future nonvolatile phase-change random access solid-state memory is presented.
文摘There are some different opinions on the formation of striped migmatite. Many striped migmatites are distributed around the plutonic rocks in the core of hot dome in nature. This shows that the pressure of intrusive rocks to wall rocks must play an important role in the formation of stripes. This paper, at first, discusses the effects of directional pressure (i. e. compressive stress from intrusive rock to wall rock) on particle migration and crystallization, and the physical mechanism of Ostwald maturation and its adjusting effect in crystalline growth. And then, on the basic principles of physics and chemistry, we lay down the stochastic evolutional rules of the formation of crystal nucleus, diffusion, crystallization and dissolution of leucosome (melt) particles; and,neglecting other restrictive conditions, we build an idealizedly simplified two-dimensional model of stochastic cellular automaton for the recrystallization of metamorphic rock under directional pressure, and realize it by writing a program of Windows on PC. Theoretical analyses and computer simulations show that, at the beginning, the free particles of leucosome are initially even distributed in the system and form many crystal nucleus ; then, the anisotropies of diffusion, crystallization and dissolution caused by the directional pressure together with the mechanisms of Ostwald maturation can make the nucleus successively grow to form lenses, unevenly disconnected stripes, and layer-stripe structure, which correspond to low, medium and high grades of metamorphism and migmatization, respectively; that is, the effect of the pressure of intrusive rock to wall rock alone can form streaked structure in migmatite. Moreover, cellular automaton, adopted in this paper, is a kind of discrete and local grid dynamic model, and is extremely suitable for simulating the evolution of spatiotemporal structure of real systems and analyzing micro-mechanism creating complex macro-phenomenon. We believe that cellular automata will have broad applications in the geosciences which is full of complicated natural phenomena.
