Showing papers by "University of Waterloo published in 1988"
01 Feb 1988-Graphical Models \/graphical Models and Image Processing \/computer Vision, Graphics, and Image Processing
TL;DR: This paper presents a survey of thresholding techniques and attempts to evaluate the performance of some automatic global thresholding methods using the criterion functions such as uniformity and shape measures.
Abstract: In digital image processing, thresholding is a well-known technique for image segmentation. Because of its wide applicability to other areas of the digital image processing, quite a number of thresholding methods have been proposed over the years. In this paper, we present a survey of thresholding techniques and update the earlier survey work by Weszka (Comput. Vision Graphics & Image Process 7, 1978 , 259–265) and Fu and Mu (Pattern Recognit. 13, 1981 , 3–16). We attempt to evaluate the performance of some automatic global thresholding methods using the criterion functions such as uniformity and shape measures. The evaluation is based on some real world images.
2,771 citations
Book•
01 Jan 1988TL;DR: In this paper, a general formulation of buoyancy-induced fluid flows is presented, including external Vertical Thermally Induced Flows and Vertical Axisymmetric Flows.
Abstract: Contents: Introduction.- General Formulation of Buoyancy-Induced Flows.- External Vertical Thermally Induced Flows.- Vertical Axisymmetric Flows.- Other Than Vertical Flows.- Combined Mass and Thermal Transport.- Unsteady External Flows.- Effects of Variable Fluid Properties.- Transport in Cold Pure and Saline Water.- Mixed Convection.- Instability, Transition and Turbulence.- Turbulent Free-Boundary Buoyant Flows.- Unstably Stratified Fluid Layers.- Transport in Enclosures and Partial Enclosures.- Transport in Saturated Porous Media.- Non-Newtonian Transport.- Some Other Aspects.- Nomenclature.- Appendixes.- Additional References.- Author Index to Additional References.- Author Index.- Subject Index.
1,105 citations
TL;DR: A simple logical framework for default reasoning by treating defaults as predefined possible hypotheses is presented, and it is shown how this idea subsumes the intuition behind Reiter's default logic.
790 citations
01 Jun 1988
TL;DR: This work presents a method of localizing the effect of refinement through the use of overlays, which are hierarchically controlled subdivisions, and introduces two editing techniques that are effective when using overlays.
Abstract: Refinement is usually advocated as a means of gaining finer control over a spline curve or surface during editing. For curves, refinement is a local process. It permits the change of control vertices and subsequent editing of the detail in one region of the curve while leaving control vertices in other regions unaffected. For tensor-product surfaces, however, refinement is not local in the sense that it causes control vertices far from a region of interest to change as well as changing the control vertices that influence the region. However, with some care and understanding it is possible to restrict the influence of refinement to the locality at which an editing effect is desired. We present a method of localizing the effect of refinement through the use of overlays, which are hierarchically controlled subdivisions. We also introduce two editing techniques that are effective when using overlays: one is direct surface manipulation through the use of edit points and the other is offset referencing of control vertices.
774 citations
TL;DR: The extensor muscles about the knee played a dominant role in progression from one step to the next in both modes coupled with the ankle plantar flexors, and the total lower limb extensor pattern, called the support moment, was highly correlated between subjects and to level walking.
676 citations
TL;DR: The proposed approach provides a general conceptual/methodological framework for using the dissociation paradigm in studies directed at establishing unconscious processes through comparisons of the relative sensitivity of comparable direct and indirect indexes of perception.
Abstract: Many studies directed at demonstrating perception without awareness have relied on the dissociation paradigm. Although the logic underlying this paradigm is relatively straightforward, definitive results have been elusive in the absence of any general consensus as to what constitutes an adequate measure of awareness. We propose an alternative approach that involves comparisons of the relative sensitivity of comparable direct and indirect indexes of perception. The only assumption required by the proposed approach is that the sensitivity of direct discriminations to relevant conscious information is greater than or equal to the sensitivity of comparable indirect discriminations. The proposed approach is illustrated through an evaluation of Avant and Thieman’s (1985) recent claim that an indirect measure of perception based on judgments of apparent visual duration provides a more sensitive indicator of perception than does a direct measure based on forced-choice recognition. Contrary to this claim, when direct and indirect indexes are measured under comparable conditions, an indirect measure based on judgments of perceived duration provides a less sensitive index of perceptual processing than do comparable direct measures. The proposed approach provides a general conceptual/methodological framework for using the dissociation paradigm in studies directed at establishing unconscious processes.
572 citations
TL;DR: Sagittal plane biomechanical and EMG analyses from eight below knee (B/K) amputee trials demonstrate considerably modified motor patterns from the residual muscles at the hip and knee as discussed by the authors.
512 citations
TL;DR: Vesicles are very important in many different areas of science and technology and serve as delivery vehicles for drugs, genetic material, enzymes and other (macro)molecules into living cells and through other hydrophobic barriers in pharmacology, medicine, genetic engineering, cosmetic industry and food industry.
Abstract: Phospholipid molecules exhibit amphiphilic properties and therefore they aggregate either in their crystalline state or in polar solvents into ordered structures with typical lyotropic liquid crystalline symmetries (de Gennes, 1974). At high lipid concentrations in water these are predominantly lamellar phases (Luzzati, 1968), while in aqueous solutions phospholipid molecules normally form self-closed spherical or oval structures where one or several phospholipid bilayers entrap(s) part of the solvent in its/their interior (Bangham & Home, 1964; Papahadjopoulos, 1978). In the case of one bilayer separating the internal and external solvent these structures are called, with respect to their size, small or large unilamellar vesicles (SUV and LUV, respectively) while the term multilamellar vesicles (MLV) is used in the case of many bilayers entrapping some of the solvent. The terms giant vesicle (GV) and large or small oligolamellar vesicles (LOV, SOV) are also used for very large vesicles and structures where several bilayers surround the entrapped solvent. Sometimes, especially in the case of technological applications, the term liposome is a homonym for SUV, LUV and MLV while in the older literature terms liposome and MLV are often synonyms. Vesicles are very important in many different areas of science and technology. In basic research they serve as models for cell membranes and their fusion, transport studies and investigations of membrane proteins that can be reconstituted in vesicles (i.e. 'proteoliposomes'). They also serve as delivery vehicles for drugs, genetic material, enzymes and other (macro)molecules into living cells and through other hydrophobic barriers in pharmacology, medicine, genetic engineering, cosmetic industry and food industry (Gregoriadis, 1984). They are also used as
477 citations
TL;DR: A cutting plane algorithm is designed based on a partial characterization of the cut polytope and used to solve max-cut problems on graphs with up to 1,600 nodes.
Abstract: We study the problem of finding ground states of spin glasses with exterior magnetic field, and the problem of minimizing the number of vias holes on a printed circuit board, or contacts on a chip subject to pin preassignments and layer preferences. The former problem comes up in solid-state physics, and the latter in very-large-scale-integrated VLSI circuit design and in printed circuit board design. Both problems can be reduced to the max-cut problem in graphs. Based on a partial characterization of the cut polytope, we design a cutting plane algorithm and report on computational experience with it. Our method has been used to solve max-cut problems on graphs with up to 1,600 nodes.
424 citations
TL;DR: A fluorescent staining procedure to detect suberin, lignin and callose in plants has been developed and greatly improves on previous methods for visualizing Casparian bands in root exodermal and endodermal cells.
Abstract: A fluorescent staining procedure to detect suberin, lignin and callose in plants has been developed. This procedure greatly improves on previous methods for visualizing Casparian bands in root exodermal and endodermal cells, and performs equally well on a variety of other plant tissues. Berberine was selected as the most suitable replacement forChelidonium majus root extract after comparing the staining properties of the extract with those of four of its constituent alkaloids. Aniline blue counterstaining efficiently quenched unwanted background fluorescence and nonspecific berberine staining, while providing a fluorochrome for callose. When used with multichambered holders which allow simultaneous processing of freehand sections, this efficient staining procedure facilitates morphological studies involving large numbers of samples.
TL;DR: In this article, a general framework for process controllers that rely upon a model to approximate plant behavior is presented, which is illustrated with a number of examples to highlight the utility of such an approach.
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TL;DR: The architecture and performance of systems that use a broadcast channel to deliver information to a community of users are discussed, and existing scheduling algorithms are described and their mean-response-time performance evaluated.
Abstract: The architecture and performance of systems that use a broadcast channel to deliver information to a community of users are discussed. Information is organized into units called pages, and at any instant of time, two or more users may request the same page. Broadcast delivery is attractive for such an environment because a single transmission of a page will satisfy all pending requests for that page. Three alternative architectures for broadcast information delivery systems are considered. They are one-way broadcast, two-way interaction, and hybrid one-way broadcast/two-way interaction. An important design issue is the scheduling of page transmissions such that the user response time is minimized. For each architecture, existing scheduling algorithms are described, and their mean-response-time performance evaluated. Properties of scheduling algorithms that yield optimal mean response time are discussed. A comparative discussion of the performance differences of the three architectures is also provided. >
TL;DR: The kinetic behavior of pyrite oxidation in carbonate-buffered solution was investigated in the laboratory as mentioned in this paper, where the initial rate of oxidation was found to be a linear function of surface area.
TL;DR: It is shown that, when the strict complementarily condition holds, the proposed algorithms reduce to an unconstrained calculation after finitely many iterations, allowing a fast asymptotic rate of convergence.
Abstract: This paper extends the known excellent global convergence properties of trust region algorithms for unconstrained optimization to the case where bounds on the variables are present. Weak conditions on the accuracy of the Hessian approximations are considered. It is also shown that, when the strict complementarily condition holds, the proposed algorithms reduce to an unconstrained calculation after finitely many iterations, allowing a fast asymptotic rate of convergence.
TL;DR: In this paper, a micromechanical analysis of plane granular assemblies of discs with a range of diameters, and interacting according to linear contact force-interparticle compliance relationships is presented.
Abstract: The paper presents a micromechanical analysis of plane granular assemblies of discs with a range of diameters, and interacting according to linear contact force-interparticle compliance relationships. Contacts are assumed to be fixed and indestructible. Macroscopically, the system is described in terms of a two-dimensional analogue of generalized Hooke’s law. Explicit expressions for elastic constants in terms of microstructure are derived for dense isotropic assemblies. It is shown that Poisson’s ratio for dense systems depends on the ratio of tangential to normal contact stiffnesses. The derived expression for Poisson’s ratio is verified by numerically simulating plane assemblies comprising 1000 particles. The effect of density on Poisson’s ratio is investigated using numerical simulations. The theory of dense plane systems is extended to dense three-dimensional systems comprising spheres. Finally, it is shown that Poisson’s result ν=1/4 is recovered for spherical particles with central interactions.
TL;DR: In this article, a kinetically based prediction model for the production of organic liquids from the flash pyrolysis of biomass is proposed, where wood or other biomass is decomposed according to two parallel reactions yielding liquid tar and ( gas + char) The tar is then further react by secondary homogeneous reactions to form mainly gas as a product.
Abstract: A kinetically based prediction model for the production of organic liquids from the flash pyrolysis of biomass is proposed. Wood or other biomass is assumed to be decomposed according to two parallel reactions yielding liquid tar and ( gas + char) The tar is then assumed to further react by secondary homogeneous reactions to form mainly gas as a product The model provides a very good agreement with the experimental results obtained using a pilot plant fluidized bed pyrolysis reactor The proposed model is shown to be able to predict the organic liquid yield as a function of the operating parameters of the process, within the optimal conditions for maximizing the tar yields, and the reaction rate constants compare reasonably well with those reported in the literature
TL;DR: In this article, the problem of determining the best sequence of insertion operations is formulated as a type of directed postman problem and an algorithm is developed for the problem that yields an optimal solution under certain conditions and approximate solutions, with a constant performance bound, when these conditions are relaxed.
Abstract: Manufacturability of printed circuit boards is a fertile area for operations researchers to aid in productivity improvements for the electronics industry. A class of such problems is described, and a particular problem that arises from an application to a middle sized electronics firm is modeled and solved. The specific problem to determine the best sequence of insertion operations is formulated as a type of directed postman problem. An algorithm is developed for the problem that yields an optimal solution under certain conditions and approximate solutions, with a constant performance bound, when these conditions are relaxed.
TL;DR: In this paper, an energy balance over an air-lifts loop is used to obtain a theoretical equation for the prediction of liquid circulation velocity in those devices and the resulting equation is shown to satisfactorily describe most of the available liquid circulation data (13 different air-lift reactors) for a large range of reactor operating scales (0.06-1.06 m3 liquid volumes) including measurements on two pilot scale vessels.
TL;DR: A stochastic-demand version of the single-stage lot-sizing problem with time-varying demand is formulated, incorporating a service-level constraint on the probability of a stockout and the static uncertainty strategy is shown to be the most straightforward to modify and "roll along" as new demands become known.
Abstract: We formulate a stochastic-demand version of the single-stage lot-sizing problem with time-varying demand, incorporating a service-level constraint on the probability of a stockout. Three strategies are studied. The "static uncertainty" strategy, in which lot-sizing decisions for every period must be made at the beginning of period 1, is shown to yield an equivalent deterministic problem with time-varying demands for which optimal or good heuristic solutions exist. The procedure by which this equivalent problem is obtained is computationally simple.
The "dynamic uncertainty" strategy allows subsequent lot sizes to be chosen on the basis of demands that have become known at a later point in time. The "static-dynamic" uncertainty approach combines features of the above two strategies and yields an equivalent linear program for any given order schedule. Relationships are suggested between these strategies and various aspects of rolling horizon production planning.
Arguments are given that in such an environment, the static uncertainty strategy is the most straightforward to modify and "roll along" as new demands become known. Good results are found when this procedure is applied to some 300-period stochastic-demand problems using rolling horizons of between 2 and 12 periods in length.
TL;DR: In this article, the relative phase and amplitude of two simultaneously applied lasers of frequency ω 1 and ω 3 = 3ω 1 was used to control product yields in photodissociation.
TL;DR: In this paper, a supply-side definition of the tourism industry is proposed, based on recognizing two tiers of tourism businesses: a tier composed of businesses that serve exclusively tourists and a tier consisting of businesses serving a mix of tourists and local residents.
TL;DR: This paper describes the principles that control gamut mapping and some details on monitor and printer calibration, and a brief description of how digital halftone screens for offset printing are prepared.
Abstract: Principles and techniques useful for calibrated color reproduction are defined. These results are derived from a project to take digital images designed on a variety of different color monitors and accurately reproduce them in a journal using digital offset printing. Most of the images printed were reproduced without access to the image as viewed in its original form; the color specification was derived entirely from calorimetric specification. The techniques described here are not specific to offset printing and can be applied equally well to other digital color devices.The reproduction system described is calibrated using CIE tristimulus values. An image is represented as a set of three-dimensional points, and the color output device as a three-dimensional solid surrounding the set of all reproducible colors for that device, called its gamut. The shapes of the monitor and the printer gamuts are very different, so it is necessary to transform the image points to fit into the destination gamut, a process we call gamut mapping. This paper describes the principles that control gamut mapping. Included also are some details on monitor and printer calibration, and a brief description of how digital halftone screens for offset printing are prepared.
TL;DR: In this article, the effect of commonality on safety stocks in a simple inventory model was investigated and the results were not all intuitive, while utilizing commonality is beneficial, nothing general can be said about the resulting change in the components' stock levels.
Abstract: This paper extends recent results of Baker et al. Baker, K. R., M. J. Magazine, H. L. W. Nuttle. 1986. The effect of commonality on safety stocks in a simple inventory model. Management Sci.32 982-988. in understanding the impact of component commonality on stocking levels under service level constraints. A model is formulated for an arbitrary number of products with general joint demand distribution. The results obtained are not all intuitive. While utilizing commonality is beneficial, nothing general can be said about the resulting change in the components' stock levels. When the cost structure is of a particular simple form, though, some interesting general patterns do emerge. We also discuss the case of using a service-level measure where rationing of common components might be required, and characterize the implied rationing rule.
TL;DR: In this paper, Csikszentmihalyi's flow construct has been suggested as a useful model for describing and operationalizing leisure experiences and data collected during the daily lives of older adults with the Experi...
Abstract: Csikszentmihalyi's flow construct has been suggested as a useful model for describing and operationalizing leisure experiences. Data collected during the daily lives of older adults with the Experi...
TL;DR: This paper investigated whether computer-mediated communication enhances users' private self-awareness, while lowering their public selfawareness, and found that subjects using computer-mediation reported significantly higher levels of acute private self awareness, and marginally lower levels of public self awareness.
TL;DR: An approach to estimation for certain 'difficult' situations associated with retrospective or incomplete prospective observation is presented and a pseudo-likelihood which enables the simple analysis of some sampling procedures is introduced.
Abstract: Data related to life histories of individuals can be obtained in many different ways, and the usefulness of multi-state models for statistical analysis is generally highly dependent on the type and nature of the data. In this paper, we focus on this, and present an approach to estimation for certain 'difficult' situations associated with retrospective or incomplete prospective observation. The paper begins with the identification of some problem areas in the analysis of data on life history processes. We discuss maximum likelihood estimation in some simple contexts and introduce a pseudo-likelihood which enables the simple analysis of some sampling procedures. This approach is illustrated on standard retrospective and case-cohort designs.
TL;DR: In this article, a general class of solutions for a homogeneous, spatially isotropic five-dimensional Kaluza-Klein theory with variable rest mass was obtained, which generalize in the algebraic and physical sense the previously found solutions in the literature.
Abstract: A general class of solutions is obtained for a homogeneous, spatially isotropic five-dimensional (5D) Kaluza-Klein theory with variable rest mass. These solutions generalize in the algebraic and physical sense the previously found solutions in the literature. The 4D spacetime sections of the solutions reduce to the Minkowski metric, K=0 Robertson-Walker metric with the equation of statep=np (p=pressure,n=constant sound speed,ρ=energy density), and to the Robertson-Walker spacetime with “steady-state” metric. Some of the solutions, in different limits, show compactification of the fifth dimension. Some extensions of the model are discussed.
TL;DR: Protein contents of crude extracts from plant and animal tissues can be rapidly assayed using a Coomassie blue dye-binding procedure combined with scanning densitometry, providing measurements of protein concentration below 100 and 200 ng, respectively.
Patent•
01 Jul 1988TL;DR: In this article, a copolymer of a conjugated diene is hydrogenated in the presence of a first ligand compound-containing RhH complex, a second ligand compounds (which may be the same as, or different from, the first), and a solvent for the copolymers, catalyst and second compound.
Abstract: A copolymer of a conjugated diene is hydrogenated in the presence of a first ligand compound-containing RhH complex, a second ligand compound (which may be the same as, or different from, the first), and a solvent for the copolymer, catalyst and second ligand compound. The process may be conducted as a homogeneous solution hydrogenation, or in the form of an aqueous emulsion.