Homogeneous Cell Structure Research Articles

Neural Network Model for Preformed-Foam Cellular Concrete

Cellular concrete (CC) is a lightweight material consisting of portland cement paste or mortar with a homogeneous void or cell structure created by introducing air or gas in the form of small bubbles during the mixing process. A major concern with CC production is achieving product consistency and predictability of performance. CC producers have generated much experimental data over the years, but the analysis of such data using traditional statistical tools has not produced reliable predictive models. This research studies the use of artificial neural networks (ANN) to predict the performance of CC mixtures. The ANN method can capture complex interactions among input/output variables in a system without any prior knowledge of the nature of these interactions and without having to explicitly assume a model form, which is generated by the data points themselves. The database assembled, the selection and training process of the ANN model, and its validation are described. Results show that production yield, foamed and unfoamed density, and compressive strength of CC mixtures can be predicted much more accurately using the ANN method compared to existing parametric methods.

Microstructure of rapidly solidified Al7.5Cu2.5Fe

A rapidly solidified aluminium alloy of nominal composition 7.5 wt.% Cu and 2.5 wt.% Fe was investigated by transmission electron microscopy. The material was seen to have a fine, homogeneous cell structure with a high dislocation density within the cells. Interconnected particles of the iron-rich AlFeCu-type quasi-crystalline (QC) phase were found to exist on cell boundaries, coexisting with a low fraction of the tetragonal body-centered θ-Al 2Cu phase. Indications are found that the QC particles are connected through 3-fold axes. The QC is found to accomodate nearly all Fe in the alloy. An in situ heat treatment at 300 °C caused precipitation and growth of the θ-Al 2Cu phase. The Cu contents in matrix and in the QC phase were seen to decrease. No transformation or growth of the QC phase could be observed. No other phase except for the QC phase was found to contain iron in the alloy. Weak orientation relationships between the QC phase and the θ phase and between the two phases and the aluminium matrix have been found.

Determination of extracellular/intracellular fluid ratios from magnetic resonance images: Accuracy, feasibility, and implementation

This study determines the accuracy and feasibility of using localized spin-lattice (T1) relaxation time measurements from magnetic resonance (MR) images to follow changes in extracellular/intracellular fluid ratios in defined subvolumes of living tissue. A red blood cell suspension was used as a test system and a simple two-compartment model incorporating fast exchange was found to suffice for the conversion of T1 values to volume ratios. The technique requires the addition of gadolinium-DTPA to the model system to selectively enhance relaxation in the extracellular fluid space. No detectable amount of gadolinium-DTPA was found to enter the intracellular fluid space, and all magnetization decay plots obtained from both intracellular constituents and complete RBC suspensions consisted of a single exponential. Both of these results are compatible with assumptions underlying our physical model. The NMR-determined fluid ratio values were compared to those measured via the microhematocrit technique. Partial saturation image-mode determinations are strongly correlated to microhematocrit data (R2 = 0.945) and indicate that localized cell volume changes may be followed with a sensitivity of +/- 2.2%. These values compare favorably with those produced when nonimaging inversion-recovery techniques are used to determine the MR hematocrit (R2 = 0.962, sensitivity = +/- 1.1%). This technique, with modification, should be applicable to the comparison of ratios of extracellular/intracellular fluid volumes in structurally complex tissues where small subvolumes of homogeneous cell structure could be examined.

Random Displacement Processes in Morphogenesis Models

The morphogenesis - an origin of the highly complicated tissue with a clear differentiation between individual parts and stable geometrical forms from a simple homogeneous cell structure. The cell displacement is an essential part of the morphogenesis. In the paper the random nature of the morphogenesis displacement is supposed. Random sets are used for the description of these displacements. The ultimate end - to study the random geometry of morphogenesis displacements, abstracting from the concrete nature of a force giving rise to this displacement. Set probabilistic regulations of the local displacement of cells depend on a geometrical location of a small number of neibours. The random set of the local displacement is defined by means of the set characteristics, such as the average measure set, the base and the kernel. The probabilistic set model of morphogenesis displacements is obtained as a result. Through the use of this model the analysis of different control problems of the morphogenesis is possible. The computation of the constructed model in the computer shows that simple changes of local regulations reduce to the generation of various global tissue structure.