Dielectric and Structural Investigations of the System BaTiO3-BaHfO3

Dielectric measurements and X-ray diffraction studies were made in the system BaTiO₃-BaHfO₃ for polycrystalline specimens containing from 0 to 30 mole % BaHfO₃. The maximum in the dielectric constant for each composition in creased as the BaHfO₃ concentration was in creased to 16 mole % and then decreased with further BaHfO₃ additions. Room-temperature lattice constants and hysteresis loops were meas ured for all compositions. A partial solid-state phase diagram is suggested for the solid solution area of the system. The phase diagram and the dielectric behavior of the system up to 16 mole % BaHfO₃ are explained on the basis of Devonshire's thermodynamic theory. The ferroelectric-paraelectric transition in the composition containing 16 mole % BaHfO₃ was essentially of second order and occurred between a ferroelectric rhombohedral phase and a paraelectric cubic phase.     

The discrete-time maximum principle : a survey and some new results

In this paper we present a review of the development of the discrete maximum principle. In the presentation, the emphasis is on a geometrical interpretation. The crucial assumptions in the theory developed are pointed out, and the attempts to overcome the limitation in the resulting theorems ore exposed. Following the review, we present a new approach to optimization of the multi-stage optimization problems called the ’ upper boundary approach ’. The classical methods of solving this problem are shown to fit smoothly into the new approach. Moreover, using this approach a number of new results have been developed, among these a new generalized version of the discrete maximum principle. The new version does not require the assumption of directional convexity.     

On transmission zeros and zero directions of multivariable time-invariant linear systems with input-derivative control

The purpose of this paper is to investigate the problem of finding inputs which generate zero outputs in linear systems whose state equation contains the derivative of the input. The method developed makes use of the simplest matrix generalized inverse, the {1}-inverse.     

INTELLIGENT COMPUTER INTEGRATED MANUFACTURING (I-CIM): Research Perspectives

Abstract

Manufacturing automation has progressed through various stages from simple data transfer to the intelligence-intensive systems. The future of CIM relies heavily on intelligence-intensive systems because manufacturing is no longer confined to one local site and manufacturing systems have become complex because of their global nature. In this article, the authors study the future manufacturing environment as a collaborative effort. The essential characteristics-the requirements for integration from a process and communication perspective-are identified as are steps in the process requiring further study. Finally, Intelligent-Computer Integrated Manufacturing (I-CIM) scenarios are presented for specific problems.     

Visualization and quantification of vesicle trafficking on a three-dimensional cytoskeleton network in living cells

Recent progress in biology and microscopy has made it possible to acquire multidimensional data on rapid cellular activities. Unfortunately, the data analysis needed to describe the observed biological process still remains a major bottleneck. We here present a novel method of studying membrane trafficking by monitoring vesicular structures moving along a three-dimensional cytoskeleton network. It allows the dynamics of such structures to be qualitatively and quantitatively investigated. Our tracking method uses kymogram analysis to extract the consistent part of the temporal information and to allow the meaningful representation of vesicle dynamics. A fully automatic extension of this method, together with a statistical tool for dynamic comparisons, allows the precise analysis and comparison of overall speed distributions and directions. It can handle typical complex situations, such as a dense set of vesicles moving at various velocities, fusing and dissociating with each other or with other cell compartments. The overall approach has been characterized and validated on synthetic data. We chose the Rab6A protein, a GTPase involved in the regulation of intracellular membrane trafficking, as a molecular model. The application of our method to GFP-Rab6A stable cells acquired using fast four-dimensional deconvolution video-microscopy gives considerable cellular dynamic information unreachable using other techniques.     

A Superplastic Al-Li-Cu-Mg-Zr Powder Alloy with High Hardness and Modulus

Structure/property studies were made on an experimental Al-3.18% Li-4.29% Cu-1.17% Mg-0.18% Zr powder alloy, which is of the low density/high modulus type. Alloy powder was made by the P&W/GPD rapid solidification rate (RSR) process, canned, and extruded to bar. The density was 2.458 × 10⁶ g/m³. The material was solution-treated, and aged at 149°C (300°F), 171°C (340°F), and 193°C (380°F), using hardness tests to determine the aging curves. Testpieces solution-treated at 516°C (961°F) showed an average yield strength (0.2% offset) of 43.3 ksi (299 MPa) and ultimate tensile strength of 50.0 ksi (345 MPa), with 1% elongation, which increased to 73.0 ksi (503 MPa) and 73.1 ksi (504 MPa), respectively, with only 0.2% elongation, on peak aging at 193°C (380°F), with a modulus of elasticity of 11.4 × 10⁶ psi (78.3 GPa). Hardness values reached 90–92 R_B on aging at 149–193°C (300–380°F). The as-extruded alloy showed superplastic behavior at 400–500°C (752–932°F) with elongations of 80–185% on 25.6 mm, peaking at 450°C (842°F). An RSR Al-2.53% Li-2.82% Mn-0.02% Zr extruded alloy showed only 18–23% elongation at 400–500°C (752–932°F).     

Measurement of Convective Heat Transfer Coefficients During Food Freezing Processes

Any prediction of freezing time for a food product depends on accurate heat transfer coefficients. The purpose of this investigation was to examine experimental procedures for accurate determination of convective transfer coefficients during freezing of food products. Measurements of heat transfer coefficients during cooling of any acrylic transducer and ground beef with similar size and shape were conducted at air temperatures below initial freezing point of the product. The results indicate that accurate measurements of the coefficients can be achieved through nonlinear regression analysis of temperature histories within an acrylic transducer.