Typical Intersection Research Articles

AIR QUALITY ASSESSMENT AT A CONGESTED URBAN INTERSECTION

The deficient transportation system of Beirut results in significant economic losses for the city and causes severe traffic congestion in the urban areas. Proposals have been made for grade separations at some of the worst congested intersections. The major concern at these intersections is air quality which greatly depends on the geometric configuration of an intersection. The air quality impact assessment at a typical intersection is presented and potential mitigation strategies for air quality management in urban areas are addressed. Air quality measurements were conducted at representative locations to define existing pollution exposure levels. Also performed were mathematical simulations for several scenarios, both with and without grade separations, changes in vehicle mix, and level of service. By comparing simulated exposure levels with air quality standards, assessment of air quality impact was obtained.

INTERSECTION MANAGEMENT: AIR QUALITY IMPACTS

This paper presents an air quality impact assessment at a typical intersection in Beirut where a grade separation is proposed. Computer simulations were conducted to define concentration in the air of selected pollutants. Simulations were performed for worst case scenarios including with and without grade separations and changes in vehicle mix. The assessment of the impact significance of air emissions was then conducted by comparing the predicted pollutants concentrations with baseline air quality levels and relevant air quality standards with the objective of optimizing the intersection management in terms of minimal air quality impacts.

INTERSECTION MANAGEMENT: NOISE IMPACTS

Urban areas of Beirut suffer severe traffic congestion because of a deficient transportation system resulting in economic losses and adverse environmental impacts. Grade separations are proposed at several intersections to minimize this problem. Noise levels, which highly depend on the geometric configuration of an intersection, are a major environmental concern. This paper presents a noise impact assessment at a typical intersection where a grade separation is proposed. For this purpose, field measurements were conducted to define current noise exposure levels and calibrate a noise emission model. Simulations were performed for several scenarios including with and without grade separations, changes in vehicle mix, type of pavement used and level-of-service. The assessment of the impact significance of noise emissions was then conducted by comparing the predicted noise exposure levels with baseline noise levels and relevant noise exposure standards with the objective of optimizing the intersection management in terms of minimal noise impacts.

Recursive estimation based on the equality-constrained optimization for intersection origin–destination matrices

A fast constrained recursive identification (CRI) algorithm is proposed to estimate intersection origin–destination (O–D) matrices dynamically. The basic idea of the CRI algorithm is to estimate intersection O–D matrices based on equality-constrained optimization and then to adjust them by Bell’s correction ( Bell, 1991a. The estimation of origin–destination matrices by constrained generalized least squares. Transporation Research 25B, 13–22; Bell, 1991b. The real-time estimation of origin–destination flows in the presence of platoon dispersion. Transportation Research 25B, 115–125.) for inequality constraints. Numerical results show that the accuracy of estimates by the CRI algorithm is fairly good—the solutions obtained by the CRI are optimal in majority of the cases, while the computational efforts are very limited—increment mainly lies on the evaluation of an inverse for an m× m matrix ( m=4 for a typical intersection) compared with the ordinary recursive least squares method. These results mean that a properly designed recursive algorithm can indeed avoid iterative procedure in each time step to obtain highly accurate on-line estimates for intersection O–D matrices. Therefore, the CRI algorithm with its reasonable balance between accuracy and computational simplicity is very suitable for practical use.

Typical Intersections of Continuous Functions with Monotone Functions

Typical Intersections of Continuous Functions with Monotone Functions

Typical intersections of continuous functions with monotone functions

For each parameter Φ \Phi a typical continuous function intersects every monotone function in a ( Φ ) (\Phi ) -uniformly symmetrically porous set.

Petrogenesis of a Proterozoic nickel-sulfide-komatiite association; the Katiniq Sill, Ungava, Quebec

Other| April 01, 1982 Petrogenesis of a Proterozoic nickel-sulfide-komatiite association; the Katiniq Sill, Ungava, Quebec Stephen J. Barnes; Stephen J. Barnes Univ. Toronto, Dep. Geol., Toronto, ON, Canada Search for other works by this author on: GSW Google Scholar C. J. A. Coats; C. J. A. Coats Search for other works by this author on: GSW Google Scholar Anthony J. Naldrett Anthony J. Naldrett Search for other works by this author on: GSW Google Scholar Author and Article Information Stephen J. Barnes Univ. Toronto, Dep. Geol., Toronto, ON, Canada C. J. A. Coats Anthony J. Naldrett Publisher: Society of Economic Geologists First Online: 02 Mar 2017 Online ISSN: 1554-0774 Print ISSN: 0361-0128 GeoRef, Copyright 2006, American Geological Institute. Abstract, Copyright, Society of Economic Geologists Economic Geology (1982) 77 (2): 413–429. https://doi.org/10.2113/econgeo.77.2.413 Article history First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Stephen J. Barnes, C. J. A. Coats, Anthony J. Naldrett; Petrogenesis of a Proterozoic nickel-sulfide-komatiite association; the Katiniq Sill, Ungava, Quebec. Economic Geology 1982;; 77 (2): 413–429. doi: https://doi.org/10.2113/econgeo.77.2.413 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyEconomic Geology Search Advanced Search Abstract The Katiniq nickel deposit is an example of an association of magmatic Fe-Ni-Cu sulfides with komatiitic volcanism, in the Cape Smith-Wakeham Bay foldbelt in northern Quebec. The deposit is unusual because of its Proterozoic age in contrast to the Archcan ages of most other deposits of this type, and is of interest in view of the relatively low degree of deformation and metamorphism to which it has been subjected.Nickel sulfide mineralization occurs within the Katiniq sill, an olivine-rich subvolcanic intrusive lens up to 150 m thick. The sill consists of a number of olivine-rich intrusive units, each characterized by a concentric zonation in olivine content from a maximum in the core to minimums at the margins. This zonation is attributed to a mechanism whereby the sill behaved as an open channel, forming part of a subvolcanic feeder system. Magma flowing through the channel carried a progressively higher proportion of intratelluric olivine phenocrysts with time, while crystallization of earlier, less olivine-rich material occurred inward from the margins. Flowage eventually became choked off as the channel became clogged with olivine.Sulfide mineralization occurs dominantly at or close to the base of the sill and shows a marked correspondence with irregularities in the footwall topography. Typical intersections consist of massive ore at the base, succeeded upward by net-textured ore and disseminated sulfides. These observations indicate a primary magmatic origin for the sulfides.The average composition of the liquid portion of the magma-olivine suspension intruded into the sill was that of a pyroxenitic komatiite, having an MgO content of about 19 percent. The chemical variations within the volcanic rocks overlying the sill are consistent with the derivation of these rocks from a liquid of this composition by low-pressure fractionation of olivine.The mean Ni/Cu ratio of the Katiniq sulfides is 4.3, close to that predicted for a sulfide liquid in equilibrium with a magma of the above composition. Massive sulfides may show significantly higher Ni/Cu ratios than net-textured and disseminated types, a discrepancy which is attributed to hydrothermal remobilization of Cu.Concentrations of precious metals, particularly Pt and Pd, are unusually high in the Katiniq sulfides; this may be partially due to higher concentrations of these elements in the parent silicate magma but is thought to be largely the consequence of equilibration of the sulfide liquid with very large volumes of silicate magma. Accumulation of immiscible sulfide liquid droplets in the sill probably occurred over a period of time when large volumes of silicate magma were flowing through the sill and subsequently on toward the surface. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Petrogenesis of a Proterozoic nickel-sulfide-komatiite association; the Katiniq Sill, Ungava, Quebec

The Katiniq nickel deposit is an example of an association of magmatic Fe-Ni-Cu sulfides with komatiitic volcanism, in the Cape Smith-Wakeham Bay foldbelt in northern Quebec. The deposit is unusual because of its Proterozoic age in contrast to the Archcan ages of most other deposits of this type, and is of interest in view of the relatively low degree of deformation and metamorphism to which it has been subjected.Nickel sulfide mineralization occurs within the Katiniq sill, an olivine-rich subvolcanic intrusive lens up to 150 m thick. The sill consists of a number of olivine-rich intrusive units, each characterized by a concentric zonation in olivine content from a maximum in the core to minimums at the margins. This zonation is attributed to a mechanism whereby the sill behaved as an open channel, forming part of a subvolcanic feeder system. Magma flowing through the channel carried a progressively higher proportion of intratelluric olivine phenocrysts with time, while crystallization of earlier, less olivine-rich material occurred inward from the margins. Flowage eventually became choked off as the channel became clogged with olivine.Sulfide mineralization occurs dominantly at or close to the base of the sill and shows a marked correspondence with irregularities in the footwall topography. Typical intersections consist of massive ore at the base, succeeded upward by net-textured ore and disseminated sulfides. These observations indicate a primary magmatic origin for the sulfides.The average composition of the liquid portion of the magma-olivine suspension intruded into the sill was that of a pyroxenitic komatiite, having an MgO content of about 19 percent. The chemical variations within the volcanic rocks overlying the sill are consistent with the derivation of these rocks from a liquid of this composition by low-pressure fractionation of olivine.The mean Ni/Cu ratio of the Katiniq sulfides is 4.3, close to that predicted for a sulfide liquid in equilibrium with a magma of the above composition. Massive sulfides may show significantly higher Ni/Cu ratios than net-textured and disseminated types, a discrepancy which is attributed to hydrothermal remobilization of Cu.Concentrations of precious metals, particularly Pt and Pd, are unusually high in the Katiniq sulfides; this may be partially due to higher concentrations of these elements in the parent silicate magma but is thought to be largely the consequence of equilibration of the sulfide liquid with very large volumes of silicate magma. Accumulation of immiscible sulfide liquid droplets in the sill probably occurred over a period of time when large volumes of silicate magma were flowing through the sill and subsequently on toward the surface.

Rectilinear leads and internal motions in the ice pack of the western Arctic Ocean

Large-scale (100 km) rectilinear lead patterns are a common feature of the Arctic Ocean ice cover. We show that many of the characteristics of these patterns can be explained by analogy with rock mechanics. In particular, the existence of two intersecting lead sets, the typical intersection angles of 28°, and the observed relative shearing motions are consistent with faulting associated with semibrittle failure. Further support for this explanation has been obtained by using NOAA and Landsat satellite imagery over an approximately 100-km-square area of the Beaufort Sea. These provide coverage of 2 days of ice deformation prior to the formation of a lead at 14° to the axis of compression. Strains of 4% over the 2-day period are within the range attributed to rock distortion preceding semibrittle failure. Finally, we suggest that the range from brittle to plastic type behavior is feasible within the Arctic Ocean sea ice, depending upon the applied rate of strain and/or the ambient confining pressures.

Geometrical Approach to Torque Free Motion of a Rigid Body Having Internal Energy Dissipation

A geometrical approach, which differs from the classical Poinsot solution, is developed for the moment free motion of a rigid body in order to discuss the case when energy is dissipated internally. Conservation of angular momentum and conservation of energy are used, respectively, to construct two surfaces, a sphere S and an ellipsoid E, which always intersect along a closed curve C; some typical intersections are shown. The motion of the body is such that the lip of the angular momentum vector remains on a curve C. Although less complete than Poinsot solution, this geometrical description provides a check on some classical results and is particularly useful in characterizing the motion when the angular momentum is kept constant while the energy decreases; then the sphere S remains the same while the ellipsoid E shrinks. The final state, corresponding to the minimum possible energy configuration, is a pure rotation about the principal axis of maximum inertia. Many interesting problems (e.g., the rotational stability of artificial satellites, the axial alignment of asteroids, and the damping of the Chandler wobble for the Earth and pulsars) are discussed in the context of this solution.