A New Metric for Grey-Scale Image Comparison

Error measures can be used to numerically assess the differences between two images. Much work has been done on binary error measures, but little on objective metrics for grey-scale images. In our discussion here we introduce a new grey-scale measure, ^g, aiming to improve upon the most common grey-scale error measure, the root-mean-square error. Our new measure is an extension of the authors' recently developed binary error measure, ^b, not only in structure, but also having both a theoretical and intuitive basis. We consider the similarities between ^b and ^g when tested in practice on binary images, and present results comparing ^g to the root-mean-squared error and the Sobolev norm for various binary and grey-scale images. There are no previous examples where the last of these measures, the Sobolev norm, has been implemented for this purpose.     

Logical Comparison of Inconsistent Perspectives using Scoring Functions

The language for describing inconsistency is underdeveloped. If a database (a set of formulae) is inconsistent, there is usually no qualification of that inconsistency. Yet, it would seem useful to be able to say how inconsistent a database is, or to say whether one database is more inconsistent than another database. In this paper, we provide a more general characterization of inconsistency in terms of a scoring function for each database . A scoring function S is from the power set of into the natural numbers defined so that S() gives the number of minimally inconsistent subsets of that would be eliminated if the subset was removed from . This characterization offers an expressive and succinct means for articulating, in general terms, the nature of inconsistency in a set of formulae. We then compare databases using their scoring functions. This gives an intuitive ordering relation over databases that we can describe as more inconsistent than. These techniques are potentially useful in a wide range of problems including monitoring progress in negotiations between a number of participants, and in comparing heterogeneous sources of information.     

An Experimental Analysis of Simple, Distributed Vertex Coloring Algorithms

We perform an extensive experimental evaluation of very simple, distributed, randomized algorithms for ( + 1) and so-called Brooks–Vizing vertex colorings, i.e., colorings using considerably fewer than colors (here denotes the maximum degree of the graph). We consider variants of algorithms known from the literature, boosting them with a distributed independent set computation. Our study clearly determines the relative performance of the algorithms with respect to the number of communication rounds and the number of colors. The results are confirmed by all the experiments and instance families. The empirical evidence shows that some algorithms use very few rounds and are rather effective, thus being amenable to be used in practice.     

Design sensitivity analysis and optimization of nonlinear dynamic response for a motorcycle driving on a half-sine bump road

This paper analyses the design sensitivity of a suspension system with material and geometric nonlinearities for a motorcycle structure. The main procedures include nonlinear structural analysis, formulation of the problem with nonlinear dynamic response, design sensitivity analysis, and optimization. The incremental finite element method is used in structural analysis. The stiffness and damping parameters of the suspension system are considered as design variables. The maximum amplitude of nonlinear transient response at the seat is taken as the objective function during the optimization simulation. A more realistic finite element model for the motorcycle structure with elasto-damping elements of different material models is presented. A comparison is made of the optimum designs with and without geometric nonlinear response and is discussed.Nomenclature A amplitude of the excitation function - a ₀,a ₁ time integration constants for the Newmark method - ^t+t C _s secant viscous damping matrix at timet+t - ^t C _T tangent viscous damping matrix at timet - C linear part of ^t C _T - D _i ⁰ initial value of thei-th design variable - D _i instanenous value of thei-th design variables - ^t+t F^(t–1) total internal force vector at the end of iteration (i–1) and timet+t - ^t+t F _(NL) ^(i–1) nonlinear part of ^t+t F^(i–1) - f frequency of the excitation function - ^t+t K _s secant stiffness matrix at timet+t - ^t K _T tangent stiffness matrix at timet - K linear part of ^t K _T - effective stiffness matrix at timet - L distance between the wheel centres - M constant mass matrix - m _T number of solution time steps - NC number of constraint equations - Q nonlinear dynamic equilibrium equation of the structural system - ^t+t R external applied load vector at timet+t - t _e active time interval for the excitation function - ^t U displacement vector of the finite element assemblage at timet - velocity of the finite element assemblage at timet - ^t Ü acceleration vector of the finite element assemblage at timet - ^t+t U ⁽ⁱ⁾ displacement vector of the finite element assemblage at the end of iterationi and timet+t - velocity vector of the finite element assemblage at the end of iterationi and timet+t - ^t+t Ü⁽ⁱ⁾ acceleration vector of the finite element assemblage at the end of iterationi and timet+t - U ⁽ⁱ⁾ vector of displacement increments from the end of iteration (i–1) to the end of iterationi at timet+t - V driving speed of motorcycle - x vector of design variable - () quantities of variation - ₀ objective function - _i i-th constraint equation     

On characterizations of recursively enumerable languages

Summary Geffert has shown that earch recursively enumerable languageL over can be expressed in the formL{h(x) ^–1 g(x)x in ⁺} ^* where is an alphabet andg, h is a pair of morphisms. Our purpose is to give a simple proof for Geffert's result and then sharpen it into the form where both of the morphisms are nonerasing. In our method we modify constructions used in a representation of recursively enumerable languages in terms of equality sets and in a characterization of simple transducers in terms of morphisms. As direct consequences, we get the undecidability of the Post correspondence problem and various representations ofL. For instance,L =(L ₀) ^* whereL ₀ is a minimal linear language and is the Dyck reductiona, A.     

Geometrical stiffness and sensitivity matrices for optimization of semi-rigid steel frameworks

A geometrical stiffness matrix for a flexibly-connected member is developed for the analysis and design of semirigid framed structures when geometrical non-linearity (P — effects and other second-order effects) must be considered. A fixity factor defining the rigidity of a connection relative to the attached member is introduced to model different types of member connectivity. The sensitivities of the geometrical stiffness matrix with respect to the fixity factor are developed with a view to conducting structural optimization. As an example of optimum design, a semi-rigid steel framework is presented along with discussion of the necessity of considering second-order effects.Presented at NATO ASI Optimization of Large Structural Systems, Berchtesgaden, Germany, Sept. 23 – Oct. 4, 1991     

On improving the accuracy of the Hough transform

The subject of this paper is very high precision parameter estimation using the Hough transform. We identify various problems that adversely affect the accuracy of the Hough transform and propose a new, high accuracy method that consists of smoothing the Hough arrayH(, ) prior to finding its peak location and interpolating about this peak to find a final sub-bucket peak. We also investigate the effect of the quantizations and ofH(, ) on the final accuracy. We consider in detail the case of finding the parameters of a straight line. Using extensive simulation and a number of experiments on calibrated targets, we compare the accuracy of the method with results from the standard Hough transform method of taking the quantized peak coordinates, with results from taking the centroid about the peak, and with results from least squares fitting. The largest set of simulations cover a range of line lengths and Gaussian zero-mean noise distributions. This noise model is ideally suited to the least squares method, and yet the results from the method compare favorably. Compared to the centroid or to standard Hough estimates, the results are significantly better—for the standard Hough estimates by a factor of 3 to 10. In addition, the simulations show that as and are increased (i.e., made coarser), the sub-bucket interpolation maintains a high level of accuracy. Experiments using real images are also described, and in these the new method has errors smaller by a factor of 3 or more compared to the standard Hough estimates.     

On structured perturbations for two classes of linear infinite-dimensional systems

This paper considers two classes of infinite-dimensional systems described by an abstract differential equationx (t) = (A + BC)x(t),x(0) =x ₀, on a Hilbert space, whereA, B, C are linear, possibly unbounded operators and is an unknown, linear, bounded perturbation. The two classes of systems are defined in terms of properties imposed on the triple (A, B, C). It is proved that for every the perturbed system (A + EF, B, C) inherits all the properties of the unperturbed system {A, B, C}) if (A, E, F) and {A, B, F} are in the same class.     

Dualities between alternative semantics for logic programming and nonmonotonic reasoning

The Gelfond-Lifschitz operator associated with a logic program (and likewise the operator associated with default theories by Reiter) exhibits oscillating behavior. In the case of logic programs, there is always at least one finite, nonempty collection of Herbrand interpretations around which the Gelfond-Lifschitz operator bounces around. The same phenomenon occurs with default logic when Reiter's operator is considered. Based on this, a stable class semantics and extension class semantics has been proposed. The main advantage of this semantics was that it was defined for all logic programs (and default theories), and that this definition was modelled using the standard operators existing in the literature such as Reiter's operator. In this paper our primary aim is to prove that there is a very interestingduality between stable class theory and the well-founded semantics for logic programming. In the stable class semantics, classes that were minimal with respect to Smyth's power-domain ordering were selected. We show that the well-founded semantics precisely corresponds to a class that is minimal w.r.t. Hoare's power domain ordering: the well-known dual of Smyth's ordering. Besides this elegant duality, this immediately suggests how to define a well-founded semantics for default logic in such a way that the dualities that hold for logic programming continue to hold for default theories. We show how the same technique may be applied to strong autoepistemic logic: the logic of strong expansions proposed by Marek and Truszczynski.     

A refinement of the low and high hierarchies

Based on the - and -classes of the polynomial-time hierarchy, Schöning [S1], [S3]introduced low and high hierarchies within NP Several classes of sets have been located in the bottom few levels of these hierarchies [S1], [S3], [KS], [BB], [BS2], [AH]. Most results placing sets in the -levels of the low hierarchy are related to sparse sets, and the proof techniques employed involve deterministic enumeration of sparse sets. Balcàzaret al. [BBS]and Allender and Hemachandra [AH] introduced extended low hierarchies, involving sets outside of NP, based on the - and gD-classes of the polynomial-time hierarchy. Several classes of sets have been located in the -levels of these hierarchies as well, and once again most such results involve sparse sets.In this paper we introduce a refinement of the low and high hierarchies and of the extended low hierarchies. Our refinement is based on the -classes of the polynomial-time hierarchy. We show that almost all of the classes of sets that are known to belong to the -levels of the low and extended low hierarchies actually belong to the newly defined -levels of these hierarchies. Our proofs use Kadin's [K1]technique of computing the census of a sparse set first, followed by a nondeterministic enumeration of the set. This leads to the sharper lowness results.We also consider the optimality of these new lowness results. For sets in the -levels of the low hierarchy we have oracle results indicating that substantially stronger results are not possible through use of Kadin's technique. For sets in the -classes of the extended low hierarchy we have tight absolute lower bounds; that is, lower bounds without oracles. These bounds are slightly stronger than similar bounds appearing in [AH].This work was supported in part by NSF Grant CCR-8909071. The second author's current address is Networking Software Division, IBM Research, Triangle Park, NC 27709, USA.     

Customer-Oriented Finite Perturbation Analysis for Queueing Networks

We consider queueing networks for which the performance measureJ ( ) depends on a parameter , which can be a service time parameter or a buffer size, and we are interested in sensitivity analysis of J ( ) with respect to . We introduce a new method, called customer-oriented finite perturbation analysis (CFPA), which predicts J ( + ) for an arbitrary, finite perturbation from a simulation experiment at . CFPA can estimate the entire performance function (by using a finite number of chosen points and fitting a least-squares approximating polynomial to the observation) within one simulation experiment. We obtain CFPA by reformulating finite perturbation analysis (FPA) for customers. The main difference between FPA and CFPA is that the former calculates the sensitivities of timing epochs of events, such as external arrivals or service time completions, while the latter yields sensitivities of departure epochs of customers. We give sufficient conditions for unbiasedness of CFPA. Numerical examples show the efficiency of the method. In particular, we address sensitivity analysis with respect to buffer sizes and thereby give a solution to the problem for which perturbation analysis was originally built.     

Comparative complexity of the representation of languages by probabilistic automata

We analyze the effect of the degree of isolation of a cut point on the number of states P(U, ) of a probabilistic automaton representing the language U. We give an example of a language Uⁿ consisting of words of length n such that there exist numbers < for which P(Uⁿ, )/P(Uⁿ, )0 as n.Translated from Kibernetika, No. 3, pp. 21–25, May–June, 1989.     

Query answering via cooperative data inference

This paper proposes the use of accessible information (data/knowledge) to infer inaccessible data in a distributed database system. Inference rules are extracted from databases by means of knowledge discovery techniques. These rules can derive inaccessible data due to a site failure or network partition in a distributed system. Such query answering requires combining incomplete and partial information from multiple sources. The derived answer may be exact or approximate. Our inference process involves two phases to reason with reconstructed information. One phase involves using local rules to infer inaccessible data. A second phase involves merging information from different sites. We shall call such reasoning processes cooperative data inference. Since the derived answer may be incomplete, new algebraic tools are developed for supporting operations on incomplete information. A weak criterion called toleration is introduced for evaluating the inferred results. The conditions that assure the correctness of combining partial results, known as sound inference paths, are developed. A solution is presented for terminating an iterative reasoning process on derived data from multiple knowledge sources. The proposed approach has been implemented on a cooperative distributed database testbed, CoBase, at UCLA. The experimental results validate the feasibility of this proposed concept and can significantly improve the availability of distributed knowledge base/database systems.List of notation Mapping - --< Logical implication - = Symbolic equality - ==< Inference path - Satisfaction - Toleration - Undefined (does not exist) - Variable-null (may or may not exist) - ^* Subtuple relationship - ^* s-membership - s-containment - Open subtuple - Open s-membership - Open s-containment - _P Open base - P Program - I Interpretation - DIP Data inference program - t Tuples - R Relations - Ø Empty interpretation - Open s-union - Open s-interpretation - Set of mapping from the set of objects to the set of closed objects - W Set of attributes - _W Set of sound inference paths on the set of attributes W - Set of relational schemas in a DB that satisfy MVD - ⁺ Range closure of W wrt      

Logic programming and Σ-programming

We consider the main similarities and dissimilarities between logic programming and -programming. Particular emphasis is placed on efficient implementation of -programs. Algorithms that translate logic programs into -programs and back are given.Translated from Kibernetika, No. 1, pp. 67–72, January–February, 1989.     

From Conditional Events to Conditional Measures: A New Axiomatic Approach

Our starting point is a definition of conditional event EH which differs from many seemingly similar ones adopted in the relevant literature since 1935, starting with de Finetti. In fact, if we do not assign the same third value u (undetermined) to all conditional events, but make it depend on EH, it turns out that this function t(EH) can be taken as a general conditional uncertainty measure, and we get (through a suitable – in a sense, compulsory – choice of the relevant operations among conditional events) the natural axioms for many different (besides probability) conditional measures.     

Convergence of MUSCL Relaxing Schemes to the Relaxed Schemes for Conservation Laws with Stiff Source Terms

We consider the convergence and stability property of MUSCL relaxing schemes applied to conservation laws with stiff source terms. The maximum principle for the numerical schemes will be established. It will be also shown that the MUSCL relaxing schemes are uniformly l ¹- and TV-stable in the sense that they are bounded by a constant independent of the relaxation parameter , the Lipschitz constant of the stiff source term and the time step t. The Lipschitz constant of the l ¹ continuity in time for the MUSCL relaxing schemes is shown to be independent of and t. The convergence of the relaxing schemes to the corresponding MUSCL relaxed schemes is then established.     

Optimal shape design for contact problems

A new optimization problem of controlling the contact pressurep is presented. We seek the minimum of the maximum contact pressurep _max under the following conditions: (a) the contact pressure should satisfy the inequalityp 0 as well as the controlling condition = v(x) p _max –p(x) 0, wherev(x) is the controller function; (b) the gapd between two bodies should be positive or zerod 0 after deformation; (c) at any possible contact point the conditionpd = 0 should be satisfied and the body that is capable of rigid body motion should be in equilibrium.If the gapd = d(p, h) is a linear function of both the pressurep and the contour changeh, then the optimization problem is a linear programming problem of restricted basis exchange. Three algorithms are presented for the solution of this problem. Finally, numerical examples will demonstrate the controlling technique for the shape optimization problem of a roller bearing.     

Architecture and Environment for Enabling Interactive Grids

Traditional use of grid computing allows a user to submit batch jobs in a grid environment. We believe, next generation grids will extend the application domain to include interactive graphical sessions. We term such grids Interactive Grids. In this paper, we describe some of the challenges involved in building Interactive Grids. These include fine grain access control, performance QoS guarantees, dynamic account management, scheduling, and user data management. We present the key architectural concepts in building Interactive Grids viz. hierarchical sessions, hierarchical admission control, hierarchical agents, classes of dynamic accounts, application profiling, user data management, scheduling for interactive sessions, persistent environment settings, and exporting remote desktop. We also describe IGENV, an environment for enabling interactive grids. IGENV consists of GISH –Grid Interactive Shell, Controlled Desktop, SAC –Session Admission Control module, GMMA –Grid Monitoring and Management Agents, and Policy Engine. We also present our testbed implementation for Interactive Grids using and extending Globus Toolkit 2.0 for the Grid middleware infrastructure, and VNC as the remote display technology.     

Causal delivery of messages with real-time data in unreliable networks

Causal order states that for any process the order in which it is delivered messages cannot violate the happened-before relation of the corresponding sendings. Such a communication abstraction has been defined for reliable distributed systems in which data of application messages have unlimited time validity. In this paper we extend the notion of causal order to cope with unreliable communication networks in which messages have real-time delivery constraints. In particular, we assume that messages have a limited time validity, , after which their data can no longer be used by the application, and that some of them can be lost by the communication network. This new abstraction, called -causal order, requires to deliver as many messages as possible within their validity time in such a way that these deliveries respect causal order. Two efficient implementations are proposed in the case of one-to-one and broadcast communication. Examples of distributed multimedia real-time applications, in which scheduling messages deliveries respecting -causal order is a crucial point for the quality of the service, are given.     

On the valuedness of finite transducers

Summary We investigate the valuedness of finite transducers in connection with their inner structure. We show: The valuedness of a finite-valued nondeterministic generalized sequential machine (NGSM) M with n states and output alphabet is at most the maximum of (1-1/#) · (2 ^k ₁ · k ₃ ) ⁿ · n ⁿ ·# ^{n 3 ·k} ₄ / ³ and 1/#·(2 ^k ₂ ·k ₃ ·(1+k ₄ )) ⁿ ·n ⁿ where k ₁6.25 and k ₂11.89 are constants and k ₃1 and k ₄0 are local structural parameters of M. There are two simple criteria which characterize the infinite valuedness of an NGSM. By these criteria, it is decidable in polynomial time whether or not an NGSM is infinite-valued. In both cases, # > 1 and # = 1, the above upper bound for the valuedness is almost optimal. By reduction, all results can be easily generalized to normalized finite transducers.