Relative Lateral Position Research Articles

First-principles study of the interfacial adhesion betweenSiO2andMoSi2

Upon oxidation, a silica scale forms on $\mathrm{Mo}{\mathrm{Si}}_{2}$, a potential high-temperature coating material for metals. This silica scale protects $\mathrm{Mo}{\mathrm{Si}}_{2}$ against high-temperature corrosive gases or liquids. We use periodic density functional theory to examine the interface between $\mathrm{Si}{\mathrm{O}}_{2}$ and $\mathrm{Mo}{\mathrm{Si}}_{2}$. The interfacial bonding is localized, as evidenced by an adhesion energy that changes only slightly with the thickness of the $\mathrm{Si}{\mathrm{O}}_{2}$ layer. Moreover, the adhesion energy displays a relatively large $(0.40\phantom{\rule{0.3em}{0ex}}\mathrm{J}∕{\mathrm{m}}^{2})$ variation with the relative lateral position of the $\mathrm{Si}{\mathrm{O}}_{2}$ and $\mathrm{Mo}{\mathrm{Si}}_{2}$ lattices due to changes in $\mathrm{Si}\text{\ensuremath{-}}\mathrm{O}$ bonding across the interface. The most stable interfacial structure yields an ideal work of adhesion of $5.75\phantom{\rule{0.3em}{0ex}}\mathrm{J}∕{\mathrm{m}}^{2}$ within the local density approximation ($5.02\phantom{\rule{0.3em}{0ex}}\mathrm{J}∕{\mathrm{m}}^{2}$ within the generalized-gradient approximation) to electron exchange and correlation, indicating extremely strong adhesion. Local densities of states and electron density difference plots demonstrate that the interfacial $\mathrm{Si}\text{\ensuremath{-}}\mathrm{O}$ bonds are covalent in character. $\mathrm{Mo}\text{\ensuremath{-}}\mathrm{O}$ interactions are not found in the $\mathrm{Si}{\mathrm{O}}_{2}∕\mathrm{Mo}{\mathrm{Si}}_{2}$ interface investigated here. Our work predicts that the $\mathrm{Si}{\mathrm{O}}_{2}$ scale strongly adheres to $\mathrm{Mo}{\mathrm{Si}}_{2}$, and further supports the potential of $\mathrm{Mo}{\mathrm{Si}}_{2}$ as a high-temperature structural material and coating.

Lane-Based Network for Flow Analysis and Inventory Management of Transportation Networks

The widely accepted link–node centerline network model inhibits lane-based traffic analysis and inventory management, specifically the ability to represent the availability of lanes, individual lane properties, connectivity among parallel lanes and at turns, and lane movement restrictions. A lane-based network overcomes the limitations by maintaining lanes as independent topological objects and thus supports data management, decision making, and network analysis at the lane level. The data model for a lane-based network uses a directed graph approach in which a set of unidirectional lanes and nodes is used to model traffic flow connectivity. The model manages the continuous lateral connectivity between parallel lanes by specifying the relative lateral position of the lanes on their parent roadways. This approach provides an efficient way to maintain lane topology and eliminates the requirement of turntables. This paper presents the model along with guidelines for lane-based inventory management and strategies for discretizing continuous lateral connectivity between parallel lanes to enable the use of existing routing algorithms (e.g., Dijkstra's). Finally, the paper presents a practical implementation built on the linear location referencing system of a state department of transportation.

Lane-Based Network for Flow Analysis and Inventory Management of Transportation Networks

The widely accepted link-node centerline network model inhibits lanebased traffic analysis and inventory management, specifically the ability to represent the availability of lanes, individual lane properties, connectivity among parallel lanes and at turns, and lane movement restrictions. A lane-based network overcomes the limitations by maintaining lanes as independent topological objects and thus supports data management, decision making, and network analysis at the lane level. The data model for a lane-based network uses a directed graph approach in which a set of unidirectional lanes and nodes is used to model traffic flow connectivity. The model manages the continuous lateral connectivity between parallel lanes by specifying the relative lateral position of the lanes on their parent roadways. This approach provides an efficient way to maintain lane topology and eliminates the requirement of turntables. This paper presents the model along with guidelines for lane-based inventory management and strateg...

Viewing corridors as right parallelepipeds for vision-based vehicle localization

A approach to vision-based vehicle localization by viewing corridors as a combination of right parallelepipeds is proposed. The objective is to derive the orientation and lateral position of a vehicle in a right parallelepiped corridor. These two kinds of information are all that is needed for vehicles to navigate safely in a right parallelepiped corridor. This approach offers low hardware cost and simple computation. Only one camera mounted on the vehicle is needed, and analytical formulae are derived for computing the vehicle location. The information source is the corridor ceiling. Two orthogonal sets of parallel lines on the corridor ceiling are used to detect the vanishing line of the ceiling. An equation is developed to derive the vehicle orientation by utilizing the detected vanishing line. Also, based on the observation of the variation of image line slopes when the vehicle moves laterally, another equation is established to evaluate the relative lateral position of the vehicle by utilizing the line slope of the ceiling line pointing forward. Experiments have been conducted, and acceptable vehicle localization results have been obtained, to prove the feasibility of the proposed approach.

Properties of seismic fault zone waves and their utility for imaging low‐velocity structures

A two‐dimensional solution for the scalar wave equation in a model of two vertical layers between two quarter spaces is used to study properties of seismic waves in a laterally heterogeneous low‐velocity structure. The waves, referred to as seismic fault zone waves, include head waves, internal fault zone reflections, and trapped waves. The analysis aims to clarify the dependency of the waves on media velocities, media attenuation coefficients, layer widths, and source‐receiver geometry. Additional calculations with extreme low‐velocity layers provide examples that may be relevant for volcanic and geothermal domains. The interference patterns controlling seismic fault zone waves change with the number of internal reflections in the low‐velocity structure. This number increases with propagation distance along the structure, decreases with fault zone width, and increases (for given length scales) with the velocity contrast. The relative lateral position of the source within the low‐velocity layer modifies die length scales associated with internal reflections and influences the resulting interference pattern. Low values of Q affect considerably the dominant period and overall duration of the waves. Thus there are significant tradeoffs between propagation distance along the structure, fault zone width, velocity contrast, source location within the fault zone, and Q. The lateral and depth receiver coordinates determine the particular point where the interference pattern is sampled and observed motion is a strong function of both coordinates. The zone connecting sources generating fault zone waves and observation points with appreciable wave amplitude can be over an order of magnitude larger than the fault zone width. Calculations for cases with layer P wave velocity of ∼200 m s−1, modeling a vertical dike or crack with fluid and gas, show conspicuous persisting oscillations. The results resemble aspects of seismic data in volcanic domains. If these waves exist in observed records, their explicit recognition and modeling will help to separate source and structural effects and aid in the interpretation of volcano‐seismology signals. Although the tradeoffs in parameters governing seismic fault zone waves are significant, each variable has its own signature, and the parameters may be constrained by additional geophysical data. Simultaneous modeling of many waveforms with an appropriate solution can resolve the various parameters and provide a high‐resolution structural image.

Autonomous Lateral Control of Vehicles in an Automated Highway System

SUMMARY Lateral control of vehicles in IVHS requires the installation of on-board sensors as well as the installation of roadway hardware such as cables, magnets, etc. Existing control approaches in PATH require road curvature and vehicle lateral position (with respect to the center of the lane) information. Hence these approaches rely on roadway sensors to obtain relative lateral position. These methods will necessitate infrastructural changes to the highway. This paper introduces the concept of autonomous lateral control or auto-tracking. The method allows us to use only line-of-sight sensor information to effect vehicle control. We present a detailed vehicle model. Controllers have been proposed to demonstrate the effectiveness of the proposed auto-tracking scheme. We also examine the possibilities of using this method for lane change purposes in an automated highway system.

Petrology and stratigraphy of some texturally well preserved thin komatiites from Kambalda, Western Australia

AbstractArchaean komatiite volcanics at Kambalda, Western Australia have been metamorphosed to upper greenschist–lower amphibolite grade and have experienced intense though heterogeneously developed polyphase deformation. Despite this, preservation of igneous textural features is often good, particularly in areas which underwent only ‘static style’ metamorphism. Thin lavas from the Tripod Hill Member of the Kambalda Komatiite Formation over the western margin of the Hunt nickel shoot display textural elements and facies variations which are virtually identical to those found in fresher thin komatiite sequences in other Archaean greenstone belts. Four principal flow profile (facies) types are defined, comprising nine subtypes. These represent stages in a facies continuum, ranging from ‘mature’ profiles which comprise thick spinifex textured tops and close packed cumulate bases through to massive, jointed ‘immature’ profiles devoid of mesoscopic spinifex texture. The causes of textural diversity within and between profiles are many and complex. However, facies variations can be attributed mainly to the effects of lava velocity at the time of major heat loss, combined with relative lateral position within any flow. The most mature textural (and geochemical) profiles developed in parts of lavas which had become ponded prior to major heat loss, whereas the least evolved profiles developed along the lateral margins (levees) of moving lavas. The study area komatiites occur as alternating stacks of flows of similar type. This stratigraphy records temporal and spatial shifts in the locus of lava ponding over the western margin of the Hunt nickel shoot. Such shifts may have been caused by irregularities in the underlying volcanic topography and/or by synvolcanic faulting and subsidence.