Microstructural stability and creep properties of die casting Mg–4Al–4RE magnesium alloy

The AE44 (Mg–4Al–4RE) alloy was prepared by a hot-chamber die casting method. The microstructure, microstructural stability and creep properties at 175 °C were investigated. The microstructure was analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and the Rietveld method. The results show that die cast AE44 magnesium alloy consists of α-Mg, Al₁₁RE₃, Al₂RE and Al_2.12RE_0.88 phases. The Al₁₁RE₃ phase is thermally stable at 175 °C whereas the metastable Al_2.12RE_0.88 phase undergoes a transition into the equilibrium Al₂RE phase. The alloy investigated is characterized by good creep properties at temperatures of 175 °C and 200 °C.     

Formation of mesoglobules in aqueous media from thermo-sensitive poly(ethoxytriethyleneglycol acrylate)

A series of six poly(ethoxytriethyleneglycol acrylate) (PETEGA) homopolymers were synthesized by atom transfer radical polymerization, reversible addition-fragmentation transfer polymerization, and anionic polymerization in order to cover a molecular weight range from 7,000 to 40,000 Da. The polymers exhibited a lower critical solution temperature (LCST) behavior in water, which was observed by the occurrence of a cloud point (CP) at around 35 °C. The transmittance of visible light versus temperature dependence overlapped during the cooling and the heating cycles, showing almost a complete lack of hysteresis. Moreover, instead of the occurrence of an uncontrolled macroscopic phase separation, stable colloidal aggregates (mesoglobules) of narrow distribution in particle size were formed in water at temperatures above the LCST of PETEGA at 1 g L⁻¹ solutions. The dimensions of the mesoglobules ranged from 91 to 235 nm, and particle size was not influenced by the molecular weight of PETEGA. Temperature changes caused considerable variations of the mesoglobules dimensions, which were smaller at higher temperatures. The addition of an anionic surfactant simultaneously increased the CP values by 4–6 °C and lowered the dimensions of the mesoglobules.     

Technical foundations for noninvasive assessment of changes in the width of the subarachnoid space with near-infrared transillumination-backscattering sounding (NIR-TBSS)

This paper presents technical foundations for a new technique of near-infrared transillumination-backscattering sounding, which is designed to enable noninvasive detection and monitoring of changes in the width of the subarachnoid space (SAS) and magnitude of cerebrovascular pulsation in humans. The key novelty of the technique is elimination of influence of blood flow in the scalp on the signals received from two infrared sensors-proximal and distal. A dedicated digital algorithm is used to estimate on line the ratio of the powers of received signals, referred to as two-sensor distal-to-proximal received power quotient, TQ (t). The propagation duct for NIR radiation reaching the distal sensor is the SAS filled with translucent cerebrospinal fluid. Information on slow fluctuations of the average width of the SAS is contained in the slow-variable part of the TQ (t), called the subcardiac component, and in TQ itself. Variations in frequency and magnitude of faster oscillations of the width of that space around the baseline value, dependent on cerebrovascular pulsation, are reflected in instantaneous frequency and envelope of the fast-variable component. Frequency and magnitude of the cerebrovascular pulsation depend on the action of the heart, so this fast-variable component is referred to as the cardiac component.     

ATR artificial brain project: 2004 progress report

This article presents the key assumptions and current status of the ATR Artificial Brain Project being undertaken to create Volitron, a device equipped with circuitry that enables the emergence of thought. Such thought would be recognized from Volitron's specific communication behaviors. The project consists of three complementary themes: psychodynamic architecture, brain-specific evolvable hardware, and the management of brain-building. The psychodynamic architecture is designed to develop automatically, driven by “pleasure” coming from discharges of tension gathered in special tension-accumulating devices. Tension-discharging patterns come first of all from the robot's interactions with its care giver/provider. For the dedicated hardware, we developed qcellular-automata (qCA), in which groups of uniform logic primitives (q-cells) serve as spike-train-processing units, as well as pulsed para-neural networks (PPNN) that can be evolved, using fuzzified signals and a genetic algorithm combined with hill climbing, and converted into qCA. The psychodynamic ideas were tested using three robots: Neko, equipped with a pleasure-driven associator, Miao, equipped with MemeStorms (a special working memory in which conflicting ideas fight for access to the long-term memory and actuators), and Miao+, whose brain is equipped with a growing neural network. This work was presented in part at the 9th International Symposium on Artificial Life and Robotics, Oita, Japan, January 28–30, 2004     

Pitch Detection Enhancement Employing Music Prediction

Pitch detection methods are widely used for extracting musical data from digital signals. A review of those methods is presented in the paper. Since musical signals may contain noise and distortion, detection results can be erroneous. In this paper a new method employing music prediction to support pitch determination is introduced. This method was developed in order to override disadvantages of standard pitch detection algorithms. The new approach utilizes signal segmentation and pitch prediction based on musical knowledge extraction employing artificial neural networks. Signal segmentation allows for estimating the pitch for a single note as a whole, therefore suppressing errors in transient and decay phases. Pitch prediction helps correcting pitch estimation errors by tracking musical context of the analyzed signal. As it was shown in the experimental results, pitch estimation errors may be reduced by using both signal segmentation and music prediction techniques.     

Electronic structure and nonlinear optical properties of model push-pull polyenes with modified indanone groups: a theoretical investigation

Several model polyenes with modified indanone groups were studied by means of density functional theory (DFT) B3LYP/6-31G*, ab initio HF/3-21G* and semiempirical AM1 methods. We investigated the effect of several substituents upon the relationship between the structure, spatial distribution of the highest occupied and the lowest unoccupied pi-MOs, a concept of the global softness and the global hardness as well as both linear and nonlinear polarizabilities for the set of pi-electron chromophores represented by the short-chain model polyene (butadiene) carrying out p-methoxyphenyl group on the one end and several modified indanone groups on the opposite end of the molecule. As probing endocyclic groups used to modify the structure of indanone the following substituents: > CH2; > C=O; > SO2, > C=CH(NO2) and > C=C(CN)2 were selected. The cubic relationship between the polarizability and the global softness was found. The highest polarizabilities (alpha, beta, gamma) are predicted for the derivatives with > C=C(CN)2 group. It was found that the value of beta depends mainly on the difference between dipole moments in the excited and ground states of the molecules. In the case of > SO2 group the results of AMI calculations significantly deviate from relationships found for other derivatives. Experimental IR and Raman spectra of newly synthesized indandione derivative of cinnamaldehyde were compared with computed ones.     

Optical Properties of Doped Antiferromagnets

We investigate the consequences of an incommensurate magnetic order in doped La_2–x Sr _x CuO₄ using dynamical mean-field theory for the effective single-band model. The high-energy optical transitions are due to high-energy excitations across large Mott–Hubbard gap, while low-energy excitations involve a pseudogap induced by the local spin order. The latter lead to a strong drop in the scattering rate at low , in qualitative agreement with the experimental data.     

Fracture toughness of structural components: influence of constraint

In this paper, in- and out-of-plane constraint are considered in the process of fracture toughness determination. A three parameter approach—J_IC, Q and T_z is utilized. The plane strain fracture toughness J_IC must be determined experimentally according to valid standards. It is the only quantity measured experimentally except for the classical uniaxial stress-strain curve determined for the material tested. Two additional parameters should be computed numerically using 2D and 3D FE analysis for the structural member which is actually analyzed. The T_z function is the generalized Poisson's ratio for elastic–plastic materials. The general model proposed allows for fracture toughness determination in two cases—when one fracture mechanism dominates the fracture process or two or more mechanisms are active simultaneously. To apply the model the fracture toughness for the particular fracture mechanisms should be known. In the paper simple models to determine these quantities are proposed both for cleavage and ductile fracture. In the latter case a distinction is made between fracture mechanisms along the shear lips and in the central part of the specimen.     

ON THE COMPOSITION-DEPENDENT INTERACTION PARAMETERS IN EQUATIONS OF STATE

Composition-dependent interaction parameters have been applied to the calculation of vapor-liquid equilibria (VLE) in mixtures containing components of different chemical nature. Binary VLE have been correlated and ternary VLE have been predicted from binary data using five different mixing rules. Binary data can be accurately correlated for systems with moderate deviations from ideality using mixing rules with two binary parameters. For very strongly nonideal mixtures three binary parameters are needed. For the prediction of ternary VLE from binary information only the mixing rules of Panagiotopoulos and Reid (1986) and Schwartzentruber et al. (1987) are reliable. For most systems the quality of predicting ternary data is comparable to the quality of correlating binary data. Significant deviations are noted only for strongly nonideal systems close to phase separation. In these cases it is recommended to use models incorporating association in an explicit form. KEYWORDS Equations of state Mixing rules Multicomponent Vapor-liquid equilibria.