Dynamics of mechanical,acoustical, and electrical properties of epoxy‐amine compositions during cure

Dynamics of mechanical, acoustical, and electric properties is studied in the cure of three samples of polymeric compositions produced on the basis of epoxy oligomer with different content of the curing agent. The measurements were made in a parallel mode with an automated measuring complex. Variations in elastic modules, sound speed, attenuation coefficient, relaxation of the shear stress, electric resistance of the samples during the complete cure in the transition from a liquid into a glass state are considered. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Electrolytic Corrosion of Titanium Carbonitride Composites

The corrosion properties of TiCN, TiCN – AlN, and (TiCN – AlN) – (Fe – Cr) ceramics as well as those of the individual components TiN and TiC in a 3% NaCl solution have been investigated. The kinetics and the mechanism of anode dissolution of metals and oxidation of specimens have been studied by using polarization curves, chemical and x-ray phase analyses, Auger electron spectroscopy, and scanning electron microscopy (SEM). TiCN and TiCN – AlN composites have been found to be the most corrosion-resistant. The presence of a metallic binder in the titanium carbon nitride somewhat decreases the corrosion resistance of the ceramics. On the whole, however, the ceramics developed boast a significantly higher corrosion resistance than that of structural steel.     

Phenol degradation by Aureobasidium pullulans FE13 isolated from industrial effluents

The degradation of phenol (2-30 mM) by free cells and by alginate-immobilized cells of Aureobasidium pullulans FE13 isolated from stainless steel effluents was studied in batch cultures with saline solution not supplemented with nutrients or yeast extract. The rate at which the immobilized cells degrade phenol was similar to the rate at which the suspended cells could degrade phenol, for a concentration of up to 16 mM of phenol. The maximum phenol volumetric degradation rate for 16 mM phenol was found to be 18.35 mg l(-1)h(-1) in the assays with free cells and 20.45 mg l(-1)h(-1) in the assays with alginate-immobilized cells, 18 mM phenol and cellular concentration of 0.176 g/l. At concentrations higher than this, an inhibitory effect was observed, resulting in the lowering of the phenol degradation rates. The immobilization was detrimental to the catechol 1,2-dioxygenase activity. However, the immobilized cells remained viable for a longer period, increasing the efficiency of phenol degradation. The yeast showed catechol 1,2-dioxygenase activity only after growth in the phenol, which was induced at phenol concentrations as low as 0.05 mM and up to 25 mM at 45 h of incubation at 30 degrees C. Phenol concentrations higher than 6mM were inhibitory to the enzyme. Addition of glucose, lactate, succinate, and benzoate reduced the rate at which phenol is consumed by cells. Our results suggest that inoculants based on immobilized cells of A. pullulans FE13 has potential application in the biodegradation of phenol and possibly in the degradation of other related aromatic compounds.     

Critical incidents in counseling psychology professionals' and trainees' social justice orientation development.

Through a qualitative, critical incident research design, this study identified and defined critical incidents that cultivated a social justice orientation among counseling psychology doctoral students and professionals. Research questions included: (a) What incidents are critical in the development of a social justice orientation? (b) Of these incidents, which are most influential? (c) How do these incidents affect social justice orientation development? Thirty-six counseling psychology doctoral students and professionals, who demonstrated a commitment to social justice through scholarship and clinical practice, completed an online survey, which consisted of rank-order and open-ended items. Qualitative data were analyzed utilizing the constant comparative method. Analyses revealed five categories of critical incidents to which participants attributed their social justice orientation development. In addition, five themes were identified that categorized the ways in which critical incidents changed individuals. Analyses of rank-ordered items indicated that the categories of Exposure to Injustice and Influence of Significant Persons were most frequently ranked as the most influential critical incidents in the development of a social justice orientation. Implications of these results and future directions for education, training, and research are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the dynamics of a gyrostat on Lagrangian equilibria in the three body problem

In this paper, we consider the noncanonical Hamiltonian dynamics of a gyrostat in the three-body problem. By means of geometric-mechanics methods, we study the approximate Poisson dynamics that arises when we develop the potential of the system in series of Legendre and truncate this in an arbitrary order k. After reduction of the dynamics by means of the two symmetries of the system, the existence and number of equilibria that we denominate of Lagrangian type in analogy with classic results on the topic, are considered. Necessary and sufficient conditions are established for their existence in an approximate dynamics of order k, and explicit expressions of these equilibria are given; this being useful for the subsequent study of the stability of these equilibria. The number of Lagrangian equilibria is thoroughly studied in approximate dynamics of orders zero and one. The main result of this work indicates that the number of Lagrangian equilibria in an approximate dynamics of order k for k≥1 is independent of the order of truncation of the potential, if the gyrostat S ₀ is almost spherical. In relation to the stability of these equilibria, necessary and sufficient conditions are given for linear stability of Lagrangian equilibria when the gyrostat is almost spherical. The rotational Poisson dynamics of the gyrostat placed at an Lagrangian equilibrium is explored and the study of nonlinear stability conditions is considered. In this way, we generalize the classical results on equilibria of the three-body problem and many results provided by other authors using more classical techniques for the case of rigid bodies.     

Resource management in LEO satellite networks

To provide truly global coverage needed by increased Personal Communication Services (PCS), a new generation of mobile satellite networks has been proposed. These low Earth orbit (LEO) mobile satellite networks handle multimedia traffic and can be used for non-real-time as well as real-time service to remote areas. Due to the many handoffs, resource management and connection admission control are important tasks for fair bandwidth sharing and QoS guarantees. Because the total link capacity has to be divided among several carriers and given the limited buffer capacity of the ATM switch, resource management is vital. It ensures the ability of the network to provide users with their negotiated QoS while protecting the network and the end-systems from congestion. We introduced a simple connection admission control (CAC) priority policy based on the delay and cell loss requirements for the investigated types of traffic. We took into account the handoff status of the satellite beams involved. Thus, we propose an onboard buffer architecture with separated buffers for new calls and intra-satellite handoff calls. The priority scheme applied is as follows: highest priority is given to CBR, followed by rt-VBR, nrtVBR and ABR.     

Neural approach for temperature‐dependent modeling of GaN HEMTs

Gallium nitride high electron‐mobility transistors have gained much interest for high‐power and high‐temperature applications at high frequencies. Therefore, there is a need to have the dependence on the temperature included in their models. To meet this challenge, the present study presents a neural approach for extracting a multi‐bias model of a gallium nitride high electron‐mobility transistors including the dependence on the ambient temperature. Accuracy of the developed model is verified by comparing modeling results with measurements. Copyright © 2014 John Wiley & Sons, Ltd.