Modeling Of Growth Processes Research Articles

Prediction of Soybean Growth and Development Using Artificial Neural Network and Statistical Models

To develop predictive models using a simple and effective modeling technique, field experiments were conducted at the Delta Research and Extension Center in Stoneville, Mississippi (33°25′ N, 90°55′ W) under irrigated conditions. The models were constructed using 4 years of field data (1998 to 2001), and validated with a fifth year of data (2002). Potential factors affecting stages of soybean growth and development were considered for developing the models. Affecting factors, such as weeds, insects, diseases, and drought stresses, were controlled optimally to simplify the modeling procedures. In addition, stepwise regression (SR) analysis, artificial neural networks (ANN), and interpolation approaches were used to construct the models. The modelling of soybean growth and development processes was separated into 2 distinct periods: vegetative growth stage (V-stage) and reproductive growth stage (R-stage). The models included 10 V-stages (up to V8) and 8 R-stages. In the V-stage models, planting date (PD) and mean relative time-span from planting to a particular stage were the only significant parameters, whereas in R-stage models, PD and maturity group (MG) were significant. The models obtained accurate predictions when only using PD, MG, and mean relative time-span from planting to a particular stage. The ANN method provides the greatest accuracy in predicting phenological events, indicating that the ANN method can be effectively applied in crop modeling.

Electrocrystallization of palladium from Pd(NH3)4Cl2 bath on stainless steel 316L

Electrochemical deposition of palladium from 0.04 M Pd(NH3)4Cl2, NH4Cl, and NH4OH bath (pH = 10) on stainless steel electrode was studied by voltammetry, chronopotentiometry, and chronoamperometry. Crossovers in cyclic voltammograms demonstrate that the deposition of palladium proceed via a nucleation/growth mechanism. Chronopotentiograms indicate that palladium reduction is not controlled by diffusion and Sand’s law is not obeyed. In the early stage of the deposition, two-dimensional (2D) nucleation and growth proceeding through instantaneous and a multitude of progressive steps followed the initial double layer charging. The processes are manifested as broad maxima in chronoamperogram and after which the current transient terminates to a plateau. Non-linear fitting methods were applied to obtain the kinetic parameters in the light of Bewick, Fleischmann, and Thirsk theory for 2D and Armstrong, Fleischmann, and Thirsk model for 3D nucleation and growth process.

Stochastic modeling of the growth process

In this paper we estimate the upper boundary of the number of trees in the selection stand determined for harvesting in a future. At the same time we showed that the present resource of the number of trees in selection stand is sustained. This is achieved by stochastic modeling of the number of trees and the number of felled trees and by solving the partial differential equation. The same problem is solved in the papers, Mitrovic (Stochastic modeling of the number of trees and the number of felled trees in selection stands, YUJOR, vol 14(1), pp 57–64, 2004; Stochastic modeling of the number of felled trees in selection stands, Computational and Applied Mathematics, vol 24(2), pp 285–292, 2005). In this paper the modified mathematical model is represented.

Homogeneity of solution-grown single crystals: A theoretical analysis

Using mathematical modeling of crystal growth processes, we have analyzed the chemical homogeneity of single crystals grown from solution by conventional techniques. The results indicate that all of these techniques are, in principle, unsuitable for the growth of homogeneous single crystals. A mathematical model has been developed for a continuous isothermal growth process which insures constant solution growth conditions and chemical homogeneity of the growing crystal. The key conditions of a continuous isothermal growth process have been formulated which insure an intended uniform distribution of intentional and unintentional impurities in the bulk of the growing single crystal.

Regularization of state-constrained elliptic optimal control problems with nonlocal radiation interface conditions

A state-constrained optimal control problem with nonlocal radiation interface conditions arising from the modeling of crystal growth processes is considered. The problem is approximated by a Moreau-Yosida type regularization. Optimality conditions for the regularized problem are derived and the convergence of the regularized problems is shown. In the last part of the paper, some numerical results are presented.

Development of the chorioallantoic placenta in Octodon degus—a model for growth processes in caviomorph rodents?

The degu Octodon degus is one of the very few members of caviomorph or hystricognath Rodentia that possesses a simply arranged chorioallantoic placenta without advanced lobulation. Therefore this species was used as a model to study regional development and growth processes of the placenta, based on the examination of 20 individuals by light and electron microscopy as well as by using markers for proliferation, trophoblast and endometrial stroma. The results were interpreted by comparison with other hystricognaths in the light of their evolutionary history. It was found that trophoblast derived from the trophospongium is essential for extension of the placenta including the labyrinth: extensive proliferation is restricted to trophoblast cells at the outer margin of the placenta and along internally directed, finger-tip like protrusions of fetal mesenchyme towards the labyrinth. This kind of placental development is regarded as part of the stem species pattern of hystricognaths, evolved more than 40 million years ago. It is indicated for the first time that the replenishment of the syncytiotrophoblast is similar to corresponding processes in the human placenta. In conclusion, the degu is a useful model for placental growth dynamics, particularly because of its simply arranged placental architecture, and may also serve as an animal model in comparison to human pregnancies.

The Guinea Pig Placenta: Model of Placental Growth Dynamics

Placental growth dynamics are an important, but poorly understood aspect of placentation for which suitable animal models are lacking. Although the guinea pig is recognised as a valuable model for human pregnancy, its suitability for this purpose is not apparent, since the developmental and evolutionary processes that led to its lobulated placenta are not fully understood. Therefore, a study on immunohistochemistry has been undertaken, including the antibody mib-1 against protein Ki-67 as a proliferation marker. It was found that cellular trophoblast derived from the placental margin is the major centre of proliferation, supported by a moderate number of proliferating cells inside the labyrinth. In contrast to the ancestral condition of caviomorph rodents, the evolution of significant placental lobulation requires the latter source of proliferation. The distribution pattern of proliferating trophoblast cells revealed for the guinea pig strongly resembles the distribution in the human placenta in that (a) evenly distributed, moderate numbers of cells occur within the exchange area and (b) focal accumulations of proliferating trophoblast cells are present along the fetal mesenchymal border and appear to serve as a growth zone for appositional growth of new exchange tissues. Thus, the guinea pig appears to be an appropriate animal model for placental growth processes in human pregnancies.

Interwell coupling effect in Si/SiGe quantum wells grown by ultra high vacuum chemical vapor deposition

Si/Si0.66Ge0.34coupled quantum well (CQW) structures with different barrier thickness of 40, 4 and 2 nm were grown on Si substrates using an ultra high vacuum chemical vapor deposition (UHV-CVD) system. The samples were characterized using high resolution x-ray diffraction (HRXRD), cross-sectional transmission electron microscopy (XTEM) and photoluminescence (PL) spectroscopy. Blue shift in PL peak energy due to interwell coupling was observed in the CQWs following increase in the Si barrier thickness. The Si/SiGe heterostructure growth process and theoretical band structure model was validated by comparing the energy of the no-phonon peak calculated by the 6 + 2-bandk·pmethod with experimental PL data. Close agreement between theoretical calculations and experimental data was obtained.

Noncontact measurement of thermal conductivity of liquid silicon in a static magnetic field

Thermal conductivity of liquid silicon is indispensable for numerical modeling of silicon crystal growth processes and for elucidating electron transport phenomena in high-temperature liquids. However, crucial obstacles render measurement of thermal conductivity difficult: convection and contamination from contact materials. In this study, the authors developed a noncontact measurement of thermal conductivity of liquid silicon using electromagnetic levitation in a static magnetic field. Convection in the levitated silicon becomes negligible above 2T. The determined thermal conductivity shows that the electron contribution is dominant for thermal transport in liquid silicon at temperatures of 1750–2050K.

Modelling of group-III nitride MOVPE in the closed coupled showerhead reactor and Planetary Reactor ®

The modelling and subsequent experimental validation of nitride growth processes in commercial, production scale multi-wafer reactors is investigated with focus on group-III nitride compounds GaN and InGaN. The paper also deals with the development of group-III nitride growth processes at elevated process pressures, highlighting the effects of gas-phase nucleation phenomena on the growth efficiency of GaN. In addition, the latest hardware and process improvements to the Planetary Reactor ® technology are presented, with focus on the development using a modelling approach, of a new gas injector design for III-nitride growth. Subsequent experimental validation of the new injector design, and its flexibility to changing process regimes for GaN and InGaN will be demonstrated for the 42×2″ Planetary Reactor ®.

Modeling of Grain Growth Using Voronoi Discretization and Natural Neighbor Interpolants

Modeling of material interface evolution in grain growth of polycrystalline materials poses considerable challenges in both finite element and meshfree methods. This paper presents a Voronoi discretization in conjunction with the natural neighbor interpolants for the effective approximation of field variables with evolving interface jump conditions and topological changes of grain structures in stressed grain growth. A new algorithm for Delaunay triangulation applicable to arbitrary grain geometries is employed, and natural neighbor interpolants that provide derivative discontinuity across the material interfaces are constructed. The proposed method is applied to the modeling of grain growth processes of polycrystalline material that exhibits complex topological changes in the grain structures.

Formula omitted] for microlithography applications: Modeling, simulation and optimization of the crystal growth process

Optimization is the ultimate goal of numerical modeling of crystal growth processes. We present the most important physical phenomena to establish a numerical process model for an industrial vertical gradient freeze (VGF) process of barium fluoride ( BaF 2 ). After reviewing the governing equations we describe an adaptive finite element approach for a phase change problem with internal radiation. We describe an interface to a commercial software package for industrial crystal growth processes to define a numerical process model in a highly automatized way. In this way we can apply an external optimization algorithm to our process model. We use a modified quasi-Newton method to propose an improvement of an industrial VGF growth process of BaF 2 .

Numerical study of small accelerations influence on composition uniformity of a growing crystal

The result of mathematical modeling of crystal growth process for real flight conditions of an automatic FOTON spacecraft is given. As the input data for the calculations, the results of low-frequency accelerations measurements on FOTON-8–FOTON-12 spacecrafts are used. Process of directional crystallization of Ge from melt in a cylindrical ampoule in three-dimensional formulation is considered. For solution of the heat and mass transfer equations the Chebyshev pseudo-spectral method is used, for solution of the momentum equation the method of finite differences is accepted. The results of the calculations show that in the melt a convective flow of the complex form arises, which changes permanently. At growth of doped crystals this weak flow makes an impact on mass transfer in the melt and defines a rather complex picture of the dopant distribution in the growing crystal; it results in macro-inhomogeneity of the crystal properties.

Tumor growth models to generate pathologies for surgical training simulators

Many virtual reality based surgical training simulators have been presented in the last few years. These systems promise to alleviate the lack of realistic training possibilities common to minimally invasive procedures. Virtual reality allows for riskless training on a wide range of findings in a condensed period of time. We investigated different methods for the generation of tumor models suitable for surgical training simulators. The goal of our research is a high fidelity hysteroscopy simulator which provides an individual surgical scene for every training. Emphasis was placed on the modeling of growth processes leading to the generation of macroscopically realistic findings of the most common pathologies in hysteroscopy, namely polyps and myomas found in the uterine cavity. Both a cellular automaton and a particle based tumor growth model are presented and discussed.

Effects of Cross-Correlation Colour Noises on Tumour GrowthProcess

We present a tumour cell growth process model including a multiplicativecoloured noise and an additive coloured noise correlated. How the noisecross-correlation intensity λ and correlation time τ canaffect the steady state properties of tumour cell growth model arediscussed by solving an approximative Fokker–Planck equation. It isfound that the increase of noise correlation time τ can cause thetumour cell number increasing, but the increase of multiplicative noiseintensity can cause the tumour cell number extinction. We also find thatthe increase of cross-correlation intensity λ in the case of 0<λ<1 can cause the tumour cell number extinction, whereasincrease of cross-correlation intensity λ in the case ofλ<0 can cause the tumour cell number increasing.

Layered growth modelling of epitaxial growth processes for SiC polytypes

Epitaxial growth processes for SiC polytypes in which a SiC substrate is employed arestudied using a layered growth model. The corresponding phase diagrams of epitaxialgrowth processes are given. First-principles calculations are used to determine theparameters in the layered growth model. The layered growth phase diagrams show thatwhen the rearrangement of atoms in one surface Si–C bilayer is allowed, the 3C-SiCstructure is formed. When the rearrangement of atoms in two surface Si–C bilayers isallowed, the 4H-SiC structure is formed. When the rearrangement of atoms in more thantwo surface Si–C bilayers, excepting the case of five surface Si–C bilayers, is allowed, the6H-SiC structure is formed, which is also shown to be the ground state structure.When the rearrangement of atoms in five surface Si–C bilayers is allowed, the15R-SiC structure is formed. Thus the 3C-SiC phase would grow epitaxially at lowtemperature, the 4H-SiC phase would grow epitaxially at intermediate temperature andthe 6H-SiC or 15R-SiC phases would grow epitaxially at higher temperature.

Stochastinių logistinių augimo modelių parametrų įvertinimas maksimalaus tikėtinumo metodu

A three alternative stochastic logistic growth models (exponential, Verhulst, Gompertz) are used for modelling of growth processes. The aim of this paper is to develop stochastic growth curves for all three stochastic growth models. Estimates of parameters of the stochastic growth models are performed by the maximum likelihood procedure with the local linearization method. The Milshtein discrete time approximation for the solutions of stochastic differential equations is applied.

Cellular Automation Approach to Model Aircraft Corrosion Pit Damage Growth

The pitting corrosion damage growth in aircraft aluminum is investigated. The main objective is to develop a corrosion pit damage growth process model using the local rules governing the electrochemical reactions and simulate them as a discrete dynamic system using cellular automata approach. The results of corrosion damage growth obtained from simulation are compared qualitatively as well as quantitatively to the experimental data obtained from Center for Materials Diagnostics at the University of Dayton Research Institute, Dayton, Ohio. The effect of various electrochemical parameters on the damage growth are obtained from the simulation are presented and discussed. The results presented illustrate the new approach using cellular automata to model pit damage growth in aircraft aluminum materials. The simulation program is developed in JAVA environment for ease of portability and usability.

Nonlinear Finite Element Modeling of Delamination Crack Growth Process between Belts of a Radial Tire

A radial tire is a very complex structure made from rubber elastomers and fiber rubber composite materials. During its use, a delamination crack growth between belts can occur, which obviously affects its durability and life. In the present paper, a new numerical model of the delamination crack growth in complex structures is presented. The model can reveal the crack growth dependence on the relative size of energy release rates at the left and right crack tips and the interfacial material property. The crack growth model, the Irwin’s virtual crack close technique and finite element analysis method are together used in simulating numerically the growth process of the delamination crack between belts of a radial tire. The numerical results show that the crack growth model proposed in the present paper can more really characterize the complexity of the delamination crack growth process in complex composite structures.

Increasing length scale of quantitative phase field modeling of concurrent growth and coarsening processes

We present an approach for increasing the length scale of quantitative phase field modeling of concurrent growth and coarsening processes with neither growth nor coarsening kinetics altered. We modify locally the free energy hump between the two equilibrium phases, which determines interface thickness, while keeping the driving forces for growth and coarsening unchanged. The approach is applied to precipitate growth and coarsening in a binary Ni–Al alloy.