Ultrasonic transducers using electron-irradiated vinylidene fluoride-trifluoroethylene copolymers

Single-element, planar transducers have been fabricated using electron-irradiated poly(vinylidene fluoride-trifluoroethylene) 80/20 mol% copolymers with different electron dosage. Electrical field-induced strain response of copolymer film with 100 Mrad dosage has been studied at 5 kHz and the electrostrictive coefficient was calculated. The transmitting response of the air-backing and epoxy-backing transducers was evaluated with the application of high DC bias voltages. Clear ultrasonic amplitudes and high frequency spectrum (>20 MHz) were observed when driven from a standard ultrasonic voltage source through a decoupling circuit. It has also showed that larger generation of ultrasonic waves will be induced under high DC bias field, which is due to the increase of induced d(33) piezoelectric coefficient. Two different polar bias voltages, positive and negative, were applied to the transducers and inverse waveforms were received, which was coincident with the theoretical analysis of the strain response of electrostrictive film.     

Absolute potassium cation affinities (PCAs) in the gas phase

The potassium cation affinities (PCAs) of 136 ligands (20 classes) in the gas phase were established by hybrid density functional theory calculations (B3-LYP with the 6-311+G(3df,2p) basis set). For these 136 ligands, 70 experimental values are available for comparison. Except for five specific PCA values-those of phenylalanine, cytosine, guanine, adenine (kinetic-method measurement), and Me(2)SO (by high-pressure mass spectrometric equilibrium measurement)-our theoretical estimates and the experimental affinities are in excellent agreement (mean absolute deviation (MAD) of 4.5 kJ mol(-1)). Comparisons with previously reported theoretical PCAs are also made. The effect of substituents on the modes of binding and the PCAs of unsubstituted parent ligands are discussed. Linear relations between Li+/Na+ and K+ affinities suggest that for the wide range of ligands studied here, the nature of binding between the cations and a given ligand is similar, and this allows the estimation of PCAs from known Li+ and/or Na+ affinities. Furthermore, empirical equations relating the PCAs of ligands with their dipole moments, polarizabilities (or molecular weights), and the number of binding sites were established. Such equations offer a simple method for estimating the PCAs of ligands not included in the present study.     

Synthesis of a hexaalkoxybenzo[b]triphenylene mesogen

The synthesis of the first mesogenic hexaalkoxybenzo[b]triphenylene derivative is reported; this compound exhibits a broad columnar liquid crystal phase at temperatures only slightly above room temperature.     

Compact 21-W 2-mum intracavity optical parametric oscillator

We report on an intracavity optical parametric oscillator (OPO) placed within a compact diode-pumped Nd:YALO laser cavity. This OPO utilizes a pair of KTP crystals, which are diffusion bonded together in a walk-off-compensated configuration. We have generated up to 21.4 W of 2-mum radiation, operating in a few-kilohertz range.     

Integrated scheduling of handling equipment at automated container terminals

To improve the productivities of an automated container terminal, it is important to schedule different types of handling equipment in an integrated way. A mixed-integer programming model, which considers various constraints related to the integrated operations between different types of handling equipment, is formulated. A heuristic algorithm, called multi-layer genetic algorithm (MLGA) is developed with a view to overcome the computation difficulty for solving the mathematical model. A numerical experimentation is carried out in order to evaluate the performance of the algorithm.     

Self-Affine Sets and Graph-Directed Systems

   Abstract. A self-affine set in R ⁿ is a compact set T with A(T)= ∪ _{d∈ D} (T+d) where A is an expanding n× n matrix with integer entries and D ={d ₁ , d ₂ ,···, d _N } ⊂ Z ⁿ is an N -digit set. For the case N = | det(A)| the set T has been studied in great detail in the context of self-affine tiles. Our main interest in this paper is to consider the case N > | det(A)| , but the theorems and proofs apply to all the N . The self-affine sets arise naturally in fractal geometry and, moreover, they are the support of the scaling functions in wavelet theory. The main difficulty in studying such sets is that the pieces T+d, d∈ D, overlap and it is harder to trace the iteration. For this we construct a new graph-directed system to determine whether such a set T will have a nonvoid interior, and to use the system to calculate the dimension of T or its boundary (if T ^o ≠  ). By using this setup we also show that the Lebesgue measure of such T is a rational number, in contrast to the case where, for a self-affine tile, it is an integer.     

Contractive projections on Banach algebras

In this paper, we explore the properties of projections of norm one on general Banach algebras, in particular the relation with conditional expectations for algebras which arise in harmonic analysis.