Phase-change optical recording: Past, present, future

We discuss specific features of Te-based compounds that made them the best materials for the phase-change data storage. It is demonstrated that the phase-change recording is due to a switch of Ge atoms between octahedral and tetrahedral symmetry positions within the Te face-centered cubic lattice. It is this nature of the transition that makes the Te-based media fast and stable. The driving force for this transition is also discussed. The chapter is concluded by introduction of a concept of the super-resolution near-field structure (super-RENS) disc that allows to reduce a bit size well below the diffraction limit and makes 100 GB/disc storage a reality.     

Highly Efficient Orange and Green Solid‐State Light‐Emitting Electrochemical Cells Based on Cationic IrIII Complexes with Enhanced Steric Hindrance

Highly efficient orange and green emission from single‐layered solid‐state light‐emitting electrochemical cells based on cationic transition‐metal complexes [Ir(ppy)₂sb]PF₆ and [Ir(dFppy)₂sb]PF₆ (where ppy is 2‐phenylpyridine, dFppy is 2‐(2,4‐difluorophenyl)pyridine, and sb is 4,5‐diaza‐9,9′‐spirobifluorene) is reported. Photoluminescence measurements show highly retained quantum yields for [Ir(ppy)₂sb]PF₆ and [Ir(dFppy)₂ sb]PF₆ in neat films (compared with quantum yields of these complexes dispersed in m‐bis(N‐carbazolyl)benzene films). The spiroconfigured sb ligands effectively enhance the steric hindrance of the complexes and reduce the self‐quenching effect. The devices that use single‐layered neat films of [Ir(ppy)₂sb]PF₆ and [Ir(dFppy)₂sb]PF₆ achieve high peak external quantum efficiencies and power efficiencies of 7.1 % and 22.6 lm W^–1) at 2.5 V, and 7.1 % and 26.2 lm W^–1 at 2.8 V, respectively. These efficiencies are among the highest reported for solid‐state light‐emitting electrochemical cells, and indicate that cationic transition‐metal complexes containing ligands with good steric hindrance are excellent candidates for highly efficient solid‐state electrochemical cells.     

The structure and properties of a Cr<Subscript>3</Subscript>C<Subscript>2</Subscript>-Ni coating deposited by a high-velocity plasma jet onto a copper substrate

Chromium carbide-nickel coatings were deposited onto a technical grade copper substrate by means of a high-velocity plasma jet of a plasmatron operating in specially selected regimes. An analysis of the coatings showed evidence of the formation of a Ni-based solid solution, a complex chromium carbide (Cr₇C₃), and an fcc crystal phase with a lattice parameter of 3.614 Å. The surface of the coatings exhibits a characteristic relief resulting from a dynamic interaction between melted and fused particles of the initial powder. The local hardness on some areas of the surface and in depth of the coating reaches 66±4.5 HRC, while the coating adhesion strength varies from 25 to 300 MPa.     

Multiple perspectives of rejected, neglected, and accepted children: Relation between sociometric status and behavioral characteristics.

Hypothesized, on the basis of findings from several studies, that rejected children are more disruptive, aggressive, and socially inappropriate than are their classmates. Three groups of 39 rejected, 29 neglected, and 39 accepted children were randomly selected from 282 boys and 210 girls who were identified separately on the basis of sociometric scores for 492 children in Grades 3–6. The 3 groups were compared using multiple analysis of variance (MANOVA) on measures from 4 domains: peer behavioral attributions, teacher ratings, analog assertiveness task, and self-evaluation. Rejected Ss were clearly distinguished from their same-sex neglected and accepted classmates and were described by teachers and peers as aggressive, disruptive and inattentive. Neglected Ss were only marginally discriminable from same-sex accepted children. Neither neglected nor rejected Ss were differentiated from accepted Ss with respect to observed assertiveness and self-ratings of shyness, unhappiness, and feeling unaccepted. The results replicate previous findings for rejected children. Currently, there is not sufficient justification to consider the group of socially neglected children as a clinical category. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An adaptive descent method for non-linear viscoplasticity

A forming model based on a viscoplastic flow formulation is derived which includes the effects of small elastic strains. A significant feature of the formulation is its reliance on the dominant inelastic material characteristics in the formation of the stiffness matrix for large strain problems. The resultant non-linear system of equations is solved by an adaptive descent method which combines the rapid convergence of Newton's method near the solution with the robustness of a method of successive approximations. The use of the adaptive descent method effectively extends the viscoplastic flow formulations into the nearly rate-insensitive range of behaviours exhibited, for example, by metals at low temperature, where slow convergence of the non-linear solution algorithm has traditionally hampered their use.     

Flexure control using piezostack actuators: design and implementation

In this paper, the application of high control authority piezostack actuators (PSAs) for active vibration control of large-scale flexible structures is studied. The idea is to add PSAs at appropriate locations of a flexible structure in order to strengthen its stiffness characteristics. In this regard, a flexible link of a macro-micro manipulator system actuated with PSAs is considered. The design of a mechanism for converting the force produced by a PSA to a bending moment is presented and a model for a system consisting of a flexible beam and a PSA is obtained. To this end, the solution of the governing partial differential equation with nonhomogeneous boundary conditions is obtained. Using singular value decomposition of the controllability Grammian of the system, optimum values for actuator parameters are obtained. The experimental results confirm that the suggested method can open up new possibilities in active vibration control of large-scale structures that require a large amount of control authority.     

Nucleation of Gas Bubbles in Extrusion Foaming of High-Pressure Polyethylene

The nucleation of gas bubbles in extrusion foaming of high-pressure polyethylene is considered. Experiments show that undissolved gas microbubbles in the solution being foamed can have a significant effect on the number density of pores in the foam. A simple model for estimating the number density of supercritical nuclei is proposed. The effect of the time of mixing of gas and polymer in the extruder, the talc concentration, and the geometric characteristics of the nozzle on the number density of pores in the foam is analyzed.