Molecular correlations in sheared thermotropic copolyesters showing banded textures

Banded textures produced in a thermotropic liquid crystal polymer by shearing between glass slides are examined by using both transmission electron and polarized light microscopy. The periodic variation in director orientation about the shear axis, as measured by light microscopy, is shown to be distinctly different from that indicated by electron diffraction. Measurements of birefringence and observation of Zernicke phase contrast indicate periodic variations in optical properties of the polymer, in step with the bands. Such effects are accounted for in terms of a synchronous rotation of the planar aromatic groups about the molecular chain axes. Evidence for an out-of-plane component of molecular orientation is also presented.     

Single- and multiobjective evolutionary optimization assisted by Gaussian random field metamodels

This paper presents and analyzes in detail an efficient search method based on evolutionary algorithms (EA) assisted by local Gaussian random field metamodels (GRFM). It is created for the use in optimization problems with one (or many) computationally expensive evaluation function(s). The role of GRFM is to predict objective function values for new candidate solutions by exploiting information recorded during previous evaluations. Moreover, GRFM are able to provide estimates of the confidence of their predictions. Predictions and their confidence intervals predicted by GRFM are used by the metamodel assisted EA. It selects the promising members in each generation and carries out exact, costly evaluations only for them. The extensive use of the uncertainty information of predictions for screening the candidate solutions makes it possible to significantly reduce the computational cost of singleand multiobjective EA. This is adequately demonstrated in this paper by means of mathematical test cases and a multipoint airfoil design in aerodynamics.     

International Working Group on Assurance Cases (for Security)

Critical systems are aptly named - from electric power to water and gas to the telephone system and the Internet, they're all critical to some aspect of our daily lives. We're a networked society and as such, it's important to both know whether critical systems are trustworthy and be able to communicate, review, and debate the level of trust achieved in them. In the safety domain, explicit safety cases are increasingly required by law, regulations, and standards. In this article, we outline what a small, international group of experts, spanning various disciplines in safety, security, reliability, and critical infrastructure, been doing with the International Working Group on Assurance Cases (for Security), what we hope to achieve, and where we go next.     

A concise process technology for 3-D suspended radio frequency micro-inductors on silicon substrate

In this letter, a concise process technology is proposed for the first time to enable the fabrication of good quality three-dimensional (3-D) suspended radio frequency (RF) micro-inductors on bulk silicon, without utilizing the lithography process on sidewall and trench-bottom patterning. Samples were fabricated to demonstrate the applicability of the proposed process technology.     

Security issues for downloaded code in mobile phones

'Software defined radio' (SDR) is a technology that will appear in future generations of mobile phones, i.e. following the third-generation mobile phone technology that is currently being defined and developed. Early versions of 'pragmatic' SDR will allow the terminal to be reconfigured at any level of its protocol stack. Ultimately, the 'pure' SDR technology will allow a mobile phone or terminal to have its air interface software configured or reconfigured by other software (or software parameters) that have been downloaded to the terminal, e.g. over the air, or from a remote server via the Internet and one's personal computer (PC). A number of security issues arise with downloaded code that implements the air interface functions, and these may not be obvious simply from looking at the way PC software is updated on-line today. This paper starts with an outline of the code that allows a mobile phone to operate over a particular air interface. This sets the baseline for a discussion of the security issues surrounding the change of this code from one that is fixed and downloaded once only, to code that is reconfigurable during the life of a product.     

Simulation of the submerged energy nozzle-mold water model system using laser-optical and computational fluid dynamics methods

The present work describes quantitative digital particle image velocimetry measurements of a full-scale water model of a thin slab mold. Different casting speeds and two submerged entry nozzles with one and two outlet ports have been investigated. The flow pattern of the single-port nozzle shows a counterclockwise-rotating double vortex that is nearly steady-state but leads to high stationary surface waves. The flow jets out of the two-port nozzle oscillate and produce a transient flow pattern with low wave amplitudes. The amplitudes for the one-port nozzle show a linear variation with the volumetric flow rate. The experimental results lead to a good interpretation of the flow phenomena and are used to validate steady-state numerical simulations with the commercial program, CFX, on the basis of the Reynolds equations. To describe anisotropic turbulence effects, the Reynolds stress model (RSM) is used for the flat single-port nozzle and the standard k-ɛ model for the mold flow. The calculated mean velocities and wave amplitudes, predicted from pressure distribution at the water surface, are generally in the consensus of the experimental data. An erratum to this article is available at .     

Deformation behavior of HCP Ti-Al alloy single crystals

Single crystals of Ti-Al alloys containing 1.4, 2.9, 5, and 6.6 pct Al (by weight) were oriented for 〈a〉 slip on either basal or prism planes or loaded parallel along the c-axis to enforce a nonbasal deformation mode. Most of the tests were conducted in compression and at temperatures between 77 and 1000 K. Trace analysis of prepolished surfaces enabled identification of the twin or slip systems primarily responsible for deformation. Increasing the deformation temperature, Al content, or both, acted to inhibit secondary twin and slip systems, thereby increasing the tendency toward strain accommodation by a single slip system having the highest resolved stress. In the crystals oriented for basal slip, transitions from twinning to multiple slip and, finally, to basal slip occurred with increasing temperature in the lower-Al-content alloys, whereas for Ti-6.6 pct Al, only basal slip was observed at all temperatures tested. A comparison of the critically resolved shear stress (CRSS) values for basal and prism slip as a function of Al content shows that prism slip is favored at room temperature in pure Ti, but the stress to activate these two systems becomes essentially equal in the Ti-6.6 pct Al crystals over a wide range of temperatures. Compression tests on crystals oriented so that the load was applied parallel to the c-axis showed extensive twinning in lower Al concentrations and 〈c+a〉 slip at higher Al concentrations, with a mixture of 〈c+a〉 slip and twinning at intermediate compositions. A few tests also were conducted in tension, with the load applied parallel to the c-axis. In these cases, twinning was observed, and the resolved shear for plastic deformation by twinning was much lower that that for 〈c+a〉 slip observed in compression loading. This article is based on a presentation made in the symposium entitled “Defect Properties and Mechanical Behavior of HCP Metals and Alloys” at the TMS Annual Meeting, February 11–15, 2001, in New Orleans, Louisiana, under the auspices of the following ASM committees: Materials Science and Critical Technology Sector, Structural Materials Division, Electronic, Magnetic & Photonic Materials Division, Chemistry & Physics of Materials Committee, Joint Nuclear Materials Committee, and Titanium Committee.