This research investigates the problem of robust resource allocation for a large class of systems operating on periodically updated data sets under an imposed quality of service (QoS) constraint. Such systems are expected to function in... more
This research investigates the problem of robust resource allocation for a large class of systems operating on periodically updated data sets under an imposed quality of service (QoS) constraint. Such systems are expected to function in an environment replete with uncertainty where the workload is likely to fluctuate substantially. Determining a resource allocation that accounts for this uncertainty in a way that can provide a probabilistic guarantee that a given level of QoS is achieved is an important research problem. First, this paper defines a methodology for quantifiably determining a resource allocation's ability to satisfy QoS constraint in the midst of uncertainty in system parameters. Uncertainty in system parameters and its impact on system performance are modeled stochastically. Second, the established stochastic model is employed to develop greedy resource allocation heuristics. Finally, the utility of the proposed stochastic robustness metric and the performance of the heuristics are evaluated in a simulated environment that replicates a heterogeneous cluster-based radar system.
In this lecture we give a self-contained introduction to the theory of lattices in Euclidean vector spaces. We reinterpret a large class of lattice basis reduction algorithms by using the concept of a "flag". In our reformulation, lattice... more
In this lecture we give a self-contained introduction to the theory of lattices in Euclidean vector spaces. We reinterpret a large class of lattice basis reduction algorithms by using the concept of a "flag". In our reformulation, lattice basis reduction algorithms are more appropriately called "flag reduction" algorithms. We address a problem that arises when one attempts to find a particularly good flag for a given lattice.
This article develops a framework that combines the economics behind the structural modeling of sovereign credit risk, corporate capital structure, and the equilibrium modeling of international asset pricing. The default decisions of the... more
This article develops a framework that combines the economics behind the structural modeling of sovereign credit risk, corporate capital structure, and the equilibrium modeling of international asset pricing. The default decisions of the sovereign and the firm are derived optimally and embedded in a two-country, two-good consumption-based asset-pricing model with a representative risk-averse agent for each country. The foreign exchange market acts as the main channel through which shocks are transmitted internationally. This framework can explain (i) the first two moments of international equity returns; (ii) the co-movement across returns on equity, corporate debt, and sovereign debt, in addition to co-movement in international equity return volatilities; and (iii) the negative relationship between equity return volatility in developed economies and sovereign credit risk in emerging economies. A structural test using the general methods of moments provides strong support for the model. In particular, the risk of a sovereign default crisis is highly relevant in the explanation of the dynamics of international equity returns.
The paper presents a method, called the method of verification by invisible invariants, for the automatic verification of a large class of parameterized systems. The method is based on the automatic calculation of candidate inductive... more
The paper presents a method, called the method of verification by invisible invariants, for the automatic verification of a large class of parameterized systems. The method is based on the automatic calculation of candidate inductive assertions and checking for their inductiveness, using symbolic model-checking techniques for both tasks. First, we show how to use model-checking techniques over finite (and small) instances of the parameterized system in order to derive candidates for invariant assertions. Next, we show that the premises of the standard deductive inv rule for proving invariance properties can be automatically resolved by finite-state (bdd-based) methods with no need for interactive theorem proving. Combining the automatic computation of invariants with the automatic resolution of the VCs (verification conditions) yields a (necessarily) incomplete but fully automatic sound method for verifying large classes of parameterized systems. The generated invariants can be transferred to the VC-validation phase without ever been examined by the user, which explains why we refer to them as "invisible". The efficacy of the method is demonstrated by automatic verification of diverse parameterized systems in a fully automatic and efficient manner.
A unified approach to analyzing search algorithms is presented. Each algorithm is characterized by the types of random problems that it can solve rapidly. The results are displayed in a way that clearly indicabes the strengths and... more
A unified approach to analyzing search algorithms is presented. Each algorithm is characterized by the types of random problems that it can solve rapidly. The results are displayed in a way that clearly indicabes the strengths and weaknesses of each algorithm. In this paper we describe a unified approach to analyzing search algorithms, one that indicates the strengths and weaknesses
This article presents a proposal for a didactic unit designed for young mid-lower class and lower-class adults, who live in a vulnerable community located in Porto Alegre. The didactic unit is part of a dissertation project, that aims at... more
This article presents a proposal for a didactic unit designed for young mid-lower class and lower-class adults, who live in a vulnerable community located in Porto Alegre. The didactic unit is part of a dissertation project, that aims at developing a course addressed to the needs and interests of the community members. The proposal is framed on studies about collaborative learning, popular education, language variation, discourse genres, and task-based learning. The main objective of the proposal is to recognize the possible different variations among speakers of the same language. In language teaching, it is considered fundamental to raise awareness about language manifestations that are different from the standard, as well as to understand the cultural aspects involving linguistic phenomena. Grounded on the students’ realities, the discussion on the variations in the English language is proposed starting from the same phenomenon in the Portuguese language.
Hindman and Leader first introduced the notion of Central sets near zero for dense subsemigroups of ((0,∞),+) and proved a powerful combinatorial theorem about such sets. Using the algebraic structure of the Stone-C̆ech compactification,... more
Hindman and Leader first introduced the notion of Central sets near zero for dense subsemigroups of ((0,∞),+) and proved a powerful combinatorial theorem about such sets. Using the algebraic structure of the Stone-C̆ech compactification, Bayatmanesh and Tootkabani generalized and extended this combinatorial theorem to the central theorem near zero. Algebraically one can define quasi-central set near zero for dense subsemigroup of ((0,∞),+), and they also satisfy the conclusion of central sets theorem near zero. In a dense subsemigroup of ((0,∞),+), C-sets near zero are the sets, which satisfies the conclusions of the central sets theorem near zero. Like discrete case, we shall produce dynamical characterizations of these combinatorically rich sets near zero.
A generalization of Arıkan's polar code construction using transformations of the form G ⊗n where G is an ℓ × ℓ matrix is considered. It is shown that a large class of such transformations polarize symmetric binary-input memoryless... more
A generalization of Arıkan's polar code construction using transformations of the form G ⊗n where G is an ℓ × ℓ matrix is considered. It is shown that a large class of such transformations polarize symmetric binary-input memoryless channels. Necessary and sufficient conditions are given for these transformations to ensure channel polarization.
Let D(n) be the maximal determinant for n × n {±1}-matrices, and R(n) = D(n)/n n/2 be the ratio of D(n) to the Hadamard upper bound. Using the probabilistic method, we prove new lower bounds on D(n) and R(n) in terms of d = nh, where h is... more
Let D(n) be the maximal determinant for n × n {±1}-matrices, and R(n) = D(n)/n n/2 be the ratio of D(n) to the Hadamard upper bound. Using the probabilistic method, we prove new lower bounds on D(n) and R(n) in terms of d = nh, where h is the order of a Hadamard matrix and h is maximal subject to h ≤ n. For example, By a recent result of Livinskyi, d 2 /h 1/2 → 0 as n → ∞, so the second bound is close to (πe/2) -d/2 for large n. Previous lower bounds tended to zero as n → ∞ with d fixed, except in the cases d ∈ {0, 1}. For d ≥ 2, our bounds are better for all sufficiently large n. If the Hadamard conjecture is true, then d ≤ 3, so the first bound above shows that R(n) is bounded below by a positive constant (πe/2) -3/2 > 0.1133.
This paper focuses on the relation between the fixed point property for continuous mappings and a discrete lion and man game played in a strongly convex domain. Our main result states that in locally compact geodesic spaces, the... more
This paper focuses on the relation between the fixed point property for continuous mappings and a discrete lion and man game played in a strongly convex domain. Our main result states that in locally compact geodesic spaces, the compactness of the domain is equivalent to its fixed point property, as well as to the success of the lion. The common link among these properties involves the existence of different types of rays, which we also discuss.
Inclusion of negation into logic programs is considered traditionally to be painful as the incorporation of full logic negation tends to super-exponen tial time complexity of the prover. Therefore the alternative approaches to negation in... more
Inclusion of negation into logic programs is considered traditionally to be painful as the incorporation of full logic negation tends to super-exponen tial time complexity of the prover. Therefore the alternative approaches to negation in logic programs are studied and among them, the procedural negation as failure sounds to be the most successful and the most widely used. However, with the spread of Constraint Logic Programming (CLP), a different approach called constructive negation becomes more popular. The reasons for acceptance of constructive negation are the preservation of the advantages of the negation as failure, i.e., efficiency and handling special features of the language, and, at the same time, while removing the main drawbacks, i.e., handling ground negative subgoals and usage as a test only. In this paper we present a constructive approach to negation in logic programs. We concentrate on implementation aspects of constructive negation here, i.e., on the design of CLP...
We study the rational homotopy types of classifying spaces of automorphism groups of smooth simply connected manifolds of dimension at least five. We give dg Lie algebra models for the homotopy automorphisms and the block diffeomorphisms... more
We study the rational homotopy types of classifying spaces of automorphism groups of smooth simply connected manifolds of dimension at least five. We give dg Lie algebra models for the homotopy automorphisms and the block diffeomorphisms of such manifolds. Moreover, we use these models to calculate the rational cohomology of the classifying spaces of the homotopy automorphisms and block diffeomorphisms of the manifold # g S d ×S d relative to an embedded disk as g → ∞. The answer is expressed in terms of stable cohomology of arithmetic groups and invariant Lie algebra cohomology. Through an extension of Kontsevich's work on graph complexes, we relate our results to the (unstable) homology of automorphisms of free groups with boundaries. I − → B Diff ∂ (M) J − → B aut ∂ (M). Let aut ∂,• (M) denote the connected component of aut ∂ (M) that contains the identity, and write Diff ∂,• (M) for the subgroup of block diffeomorphisms homotopic
In this paper, we will start the discussion with the refinable generators of the shift invariant (SI) spaces in L 2 (R) that possess the largest possible regularities and required vanishing moments. For the pseudo-scaling generators, the... more
In this paper, we will start the discussion with the refinable generators of the shift invariant (SI) spaces in L 2 (R) that possess the largest possible regularities and required vanishing moments. For the pseudo-scaling generators, the corresponding MRA frame wavelets with certain regularities are constructed. In addition, the stability of the refinable SI spaces and the corresponding complementary spaces, biorthogonality of the SI spaces, and the approximation property of the spaces are also discussed.
The compactification from the 11-dimensional Horava-Witten orbifold to 5dimensional heterotic M-theory on a Schoen Calabi-Yau threefold is reviewed, as is the specific SU (4) vector bundle leading to the "heterotic standard model" in the... more
The compactification from the 11-dimensional Horava-Witten orbifold to 5dimensional heterotic M-theory on a Schoen Calabi-Yau threefold is reviewed, as is the specific SU (4) vector bundle leading to the "heterotic standard model" in the observable sector. A generic formalism for a consistent hidden sector gauge bundle, within the context of strongly coupled heterotic M-theory, is presented. Anomaly cancellation and the associated bulk space 5-branes are discussed in this context. The further compactification to a 4-dimensional effective field theory on a linearized BPS double domain wall is then presented to order κ 4/3 11. Specifically, the generic constraints required for anomaly cancellation and by the linearized domain wall solution, as well as restrictions imposed by the necessity to have positive squared gauge couplings to order κ 4/3 11 are presented in detail. Finally, the expression for the Fayet-Iliopoulos term associated with any anomalous U (1) gauge connection is presented and its role in N = 1 spontaneous supersymmetry breaking in the low energy effective theory is discussed.
Recent developments in macroeconomic theory emphasize that transient economic fluctuations can arise as responses to changes in long run factors-in particular, technological improvements-rather than short run factors. This contrasts with... more
Recent developments in macroeconomic theory emphasize that transient economic fluctuations can arise as responses to changes in long run factors-in particular, technological improvements-rather than short run factors. This contrasts with the view that short run fluctuations and shifts in long run trends are largely unrelated. We examine empirically the effect of shifts in stochastic trends that are common to several macroeconomic series. Using a linear time series model related to a VAR, we consider first a system with ONP, consumption and investment with a single common stochstic trend; we then examine this system augmented by money and prices and an additional stochastic trend. Our results suggest that movements in the "real" stochastic trend account for one-half to two-thirds of the variation in postwar U.S. GNP.
Income convergence across countries turns on whether technological knowledge spillovers are global or local. I estimate the amount of spillovers from R&D expenditures on a geographic basis, using a new data set which encompasses most of... more
Income convergence across countries turns on whether technological knowledge spillovers are global or local. I estimate the amount of spillovers from R&D expenditures on a geographic basis, using a new data set which encompasses most of the world's innovative activity between 1970 and 1995. I find that technology is to a substantial degree local, not global, as the benefits from spillovers are declining with distance. The distance at which the amount of spillovers is halved is about 1,200 kilometers. I also find that over time, technological knowledge has become considerably more global. Moreover, language skills are important for spillover diffusion.
A general formulation for the spectral noise S& of random linear resistor networks of arbitrary topology is given. General calculational methods based on Tellegen's theorem are illustrated for oneand two-probe configurations. For... more
A general formulation for the spectral noise S& of random linear resistor networks of arbitrary topology is given. General calculational methods based on Tellegen's theorem are illustrated for oneand two-probe configurations. For self-similar networks, we show the existence of a new exponent b, member of a whole new hierarchy of exponents characterizing the size dependence of the normalized noise spectrum W~-S~/8. b is shown to lie between the fractal dimension d and the resistance exponent-Pt.. b has been calculated for a large class of fractal structures: Sierpinski gaskets, X lattices, von Koch structures, etc. For percolating systems, W& is investigated for p &p, as well as for p &p,. In particular, an anomalous increase of the noise at p~p, is obtained. A finite-size-scaling function is proposed, and the corresponding exponent b is calculated in mean-field theory. I. INTRODUCTION. Statistical self-similarity is emerging as an important concept underlying the behavior of disordered systems. In percolation clusters, for example, the fractal dimension has been identified first; it was immediately realized, however, that this quantity and the correlation-length exponent did not suffice for a characterization of all the physical properties of these clusters. Alexander and Orbach and Rammal and Toulouse introduced the spectral dimension d to describe the spectrum of the Laplacian operator which appears in a large variety of linear physical problems. The geometrical property which most influences the spectral dimension is the number of closed loops of the fractal. It is an intrinsic geometrical property" independent of the embedding Euclidean space. Another such intrinsic property is the recently iptroduced ' spreading dimension d. Intuitively, it is plausible that an infinite number of exponents must be used to
Darcy’s law is a spatial equation expressing the first-order theory of fluid filtration within a porous medium, stating that the filtration velocity w w is linearly related, through the permeability tensor k (function of fluid viscosity... more
Darcy’s law is a spatial equation expressing the first-order theory of fluid filtration within a porous medium, stating that the filtration velocity w w is linearly related, through the permeability tensor k (function of fluid viscosity and fluid volumetric fraction), to the force density hh, given by the sum of the negative of the difference between the pressure gradient gradp and the body force rfT ff (rfT is the true mass density of the fluid, and ff is usually gravity) to which the fluid is subjected. In the formulation employed in this study, the filtration velocity (or specific discharge) w is obtained by multiplying the fluid-to-solid relative velocity vvf vs by the fluid volumetric fraction ff , and reads w w = ff (vvf vvs) = kh = kk(gradp rfT f): (1) The pressure gradient gradp and the body force f are spatial covectors fields, valued in the cotangent space T ?
This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with... more
This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright
We investigate microlocal properties of partial differential operators with generalized functions as coefficients. The main result is an extension of a corresponding (microlocalized) distribution theoretic result on operators with smooth... more
We investigate microlocal properties of partial differential operators with generalized functions as coefficients. The main result is an extension of a corresponding (microlocalized) distribution theoretic result on operators with smooth hypoelliptic symbols. Methodological novelties and technical refinements appear embedded into classical strategies of proof in order to cope with most delicate interferences by non-smooth lower order terms. We include simplified conditions which are applicable in special cases of interest.
Feedback problems consist of removing a minimal number ofvertices of a directed or undirected graph in order to make it acyclic. The problem is known to be NPcomplete. In this paper we consider the variant on undirected graphs. The... more
Feedback problems consist of removing a minimal number ofvertices of a directed or undirected graph in order to make it acyclic. The problem is known to be NPcomplete. In this paper we consider the variant on undirected graphs. The polyhedral structure of the Feedback V ertex Set polytope is studied. We prove that this polytope is full dimensional and show that some inequalities are facet de ning. We describe a new large class of valid constraints, the subset inequalities. A branch-and-cut algorithm for the exact solution of the problem is then outlined, and separation algorithms for the inequalities studied in the paper are proposed. A Local Search heuristic is described next. Finally we create a library of 1400 random generated instances with the geometric structure suggested by the applications, and we computationally compare the two algorithmic approaches on our library.
As institutions of higher education turn more to online and remote learning, the ability of faculty to provide actionable feedback to students remains a critical responsibility of effective instructors. Based on a review of research on... more
As institutions of higher education turn more to online and remote learning, the ability of faculty to provide actionable feedback to students remains a critical responsibility of effective instructors. Based on a review of research on the significance of feedback to student learning and a review of online courses over the past several semesters, it was determined that there are significant differences in the timeliness, methods, frequency, and quality of feedback given to students. The variability noted can alter the impact on student learning. Based on their experience as online instructors the writers suggest best practices for providing feedback that that have proven successful in practice
We prove existence of finitely many ergodic equilibrium states for a large class of non-uniformly expanding local homeomorphisms on compact manifolds and Hölder continuous potentials with not very large oscillation. No Markov structure is... more
We prove existence of finitely many ergodic equilibrium states for a large class of non-uniformly expanding local homeomorphisms on compact manifolds and Hölder continuous potentials with not very large oscillation. No Markov structure is assumed. If the transformation is topologically mixing there is a unique equilibrium state, it is exact and satisfies a non-uniform Gibbs property. Under mild additional assumptions we also prove that the equilibrium states vary continuously with the dynamics and the potentials (statistical stability) and are also stable under stochastic perturbations of the transformation.