Intersection Modeling for Highway Alignment Optimization

Abstract:   When optimizing a highway alignment, it is desirable to consider new and modified intersections along it. This article develops methods for locally optimizing intersections within highway alignment optimization processes. Design and operational characteristics for intersections are reviewed from the literature. The formulation considers the major costs that are sensitive to intersection characteristics. Genetic algorithms are used for optimal search. The proposed methods are implemented on an artificial study area and on a real one through the use of geographic information systems. The results show how the methods work for local optimization of intersections as well as for optimizing entire alignments. These methods can be used for improving search flexibility, thus allowing more effective intersections. They also provide a basis for extending the alignment optimization from single highways to networks .     

Learning prosthetic vision: a virtual-reality study.

Acceptance of prosthetic vision will be heavily dependent on the ability of recipients to form useful information from such vision. Training strategies to accelerate learning and maximize visual comprehension would need to be designed in the light of the factors affecting human learning under prosthetic vision. Some of these potential factors were examined in a visual acuity study using the Landolt C optotype under virtual-reality simulation of prosthetic vision. Fifteen normally sighted subjects were tested for 10-20 sessions. Potential learning factors were tested at p < 0.05 with regression models. Learning was most evident across-sessions, though 17% of sessions did express significant within-session trends. Learning was highly concentrated toward a critical range of optotype sizes, and subjects were less capable in identifying the closed optotype (a Landolt C with no gap, forming a closed annulus). Training for implant recipients should target these critical sizes and the closed optotype to extend the limit of visual comprehension. Although there was no evidence that image processing affected overall learning, subjects showed varying personal preferences.     

Image analysis for microelectronic retinal prosthesis

By way of extracellular, stimulating electrodes, a microelectronic retinal prosthesis aims to render discrete, luminous spots-so-called phosphenes-in the visual field, thereby providing a phosphene image (PI) as a rudimentary remediation of profound blindness. As part thereof, a digital camera, or some other photosensitive array, captures frames, frames are analyzed, and phosphenes are actuated accordingly by way of modulated charge injections. Here, we present a method that allows the assessment of image analysis schemes for integration with a prosthetic device, that is, the means of converting the captured image (high resolution) to modulated charge injections (low resolution). We use the mutual-information function to quantify the amount of information conveyed to the PI observer (device implantee), while accounting for the statistics of visual stimuli. We demonstrate an effective scheme involving overlapping, Gaussian kernels, and discuss extensions of the method to account for shortterm visual memory in observers, and their perceptual errors of omission and commission.     

The conductivity behaviour of gamma-irradiated PEO-LiX electrolytes. I

In an attempt to enhance the room temperature ionic conductivity of PEO-LiX films, samples have been exposed to gamma-irradiation at 78°C. The success with which cross-links have been introduced into the amorphous form has been evaluated from d.s.c. analysis and temperature-dependent conductivity data. Retardation of the recrystallisation event, associated with uncomplexed poly(ethylene oxide), does not occur over a range of total doses. Changes in overall conductivity levels for the PEO-LiCF₃SO₃ ([EO units]/[Li] = 9) system, indicate light cross-linking at 2.25 Mrad of exposure. However, higher doses result in a substantial amount of chain scission, leading eventually to poor mechanical properties. A similar study on PEO-LiClO₄ ([EO units]/[Li] = 20) confirms that the above route is an ineffective method to improve room temperature conductivity.     

Characterization of interfacial friction in coated sheet steels: influence of stamping process parameters and wear mechanisms

By means of a tensile strip testing system, the nature of interfacial friction in stamping operations were investigated for three different coated sheet steels. Friction coefficient measurements were taken at seventeen distinct operating conditions by varying the sheet strip coating material (lead and zinc), applied lubricant (oil-base lubricants and greases) and pin radii (10 and 20 mm). In addition to determining the friction coefficient, the surface roughnesses of the sheet strips were measured before and after the completion of each test. From the experimental results, several relationships were ascertained for the role of the microscopic wear in determining the character of interfacial friction during stamping processes.     

Cross wedge rolling failure mechanisms and industrial application

Cross wedge rolling (CWR) is an innovative metal forming technology with several well-documented benefits over other traditional manufacturing processes. Over the past several years, CWR technology has obtained overwhelming popularity within the United States, especially in the automotive industry. Based on the authors’ academic and industrial experience, recent development techniques for the CWR process are presented. Initially, the experimental and numerical research techniques for analyzing fundamental CWR failure mechanisms are presented with particular emphasis on the finite element method. This is followed by discussion on industrial implementation of cross wedge rolling system, including the required tooling manufacturing process and major supporting systems. Finally several industrial examples are presented to demonstrate feasibility and efficiency of the CWR process with the goal of removing hesitation of US manufacturers to adopt novel CWR technology.     

Conical slow wave antenna as a plasma source

A simple conical helix has been successfully employed as a slow wave structure to generate plasmas by electron cyclotron resonance heating (ECRH). The plasma is typical of plasmas created by 'Lisitano coil' sources, n approximately 10(10)-10(12) cm(-3) with T(e) approximately 2-20 eV. This source, however, is much simpler to fabricate. The ease of fabrication allows the user some flexibility in designing the source to fit a specific plasma physics experiment.