Sequence Of Paths Research Articles

A graph theoretical approach to quantitative structure-activity relationship

The graph theoretical approach considered consists of the characterization of molecular forms by selected graph (structural) invariants followed by a detailed comparison of the derived “mathematical” representations for the molecules. In earlier work sequences of integers representing the number of paths of different length have been used. Here we continue to explore the potential of path sequences for characterization of molecules and their activity by using suitably weighted paths and examining the influence of the variations in the parameterization associated with heteroatoms. As an illustration we have reconsidered a collection of aminodihydroxytetralins, which are structurally related to dopamine and exhibit dopaminergic activity. In particular, we made a sensitivity study concerned with the influence of bonds of different types (i.e., aromatic C—C bonds, aliphatic C—C bonds, as well as C—O and O—N bonds).

Graph theoretical study of structural similarity in benzomorphans

The existing mathematical models for quantitative structure-activity relationships are normally used to search for additivities of constituent components which contribute to the structure of compounds of interest. Here a distinctive scheme in which we quantify the degree of structural similarity of molecular compounds of interest is considered. The result of our analysis is a numerical index of similarity (or dissimilarity) which can be used for ranking and ordering compounds. The similarity index is derived from comparisons of path sequences in molecular skeletons (that is, sequences of the number of paths of different lengths) as the fundamental graph invariants. Applications to quantitative structure-activity studies follow from the hypothesis that molecules of similar pharmacological activity resemble one another. An examination of the structure-activity relationships among benzomorphins has been selected to illustrate the approach. Among the benzomorphins considered, a few have been selected as standards, and others are “tested” for the degree of skeletal similarity to see if the derived ranking agrees with the experimentally observed properties of these narcotic analgeties. The results support the premise and justify further investigations using the scheme outlined.

Strain path and work-hardening behavior of brass

Plastic straining in metal forming usually includes changes of strain path, which are frequently not taken into account in the analysis of forming processes. Moreover, strain path change can significantly affect the mechanical behavior and microstructural evolution of the material. For this reason, a combination of several simple loading test sequences is an effective way to investigate the dislocation microstructure of sheet metals under such forming conditions. Pure tension and rolling strain paths and rolling–tension strain path sequences were performed on brass sheets. A study of mechanical behavior and microstructural evolution during the simple and the complex strain paths was carried out, within a wide range of strain values. The appearance and development of deformation twinning was evident. It was shown that strain path change promotes the onset of premature twinning. The work-hardening behavior is discussed in terms of the twinning and dislocation microstructure evolution, as revealed by transmission electron microscopy.

Lagrangian Relaxation Based Inter-Layer Signal Via Assignment for 3-D ICs

Three-dimensional integrated circuits (3-D ICs), i.e., stacked dies, can alleviate the interconnect problem coming with the decreasing feature size and increasing integration density, and promise a solution to heterogenous integration. The vertical connection, which is generally implemented by the through-the-silicon via, is a key technology for 3-D ICs. In this paper, given 3-D circuit placement or floorplan results with white space reserved between blocks for inter-layer interconnections, we proposed methods for assigning inter-layer signal via locations. Introducing a grid structure on the chip, the inter-layer via assignment of two-layer chips can be optimally solved by a convex-cost max-flow formulation with signal via congestion optimized. As for 3-D ICs with three or more layers, the inter-layer signal via assignment is modeled as an integral min-cost multi-commodity flow problem, which is solved by a heuristic method based on the lagrangian relaxation. Relaxing the capacity constraints in the grids, we transfer the min-cost multi-commodity flow problem to a sequence of lagrangian sub-problems, which are solved by finding a sequence of shortest paths. The complexity of solving a lagrangian sub-problem is $O(n_{nt}n_g^2)$, where nnt is the number of nets and ng is the number of grids on one chip layer. The experimental results demonstrated the effectiveness of the method.

Planning Among Movable Obstacles with Artificial Constraints

In this paper we present artificial constraints as a method for guiding heuristic search in the computationally challenging domain of motion planning among movable obstacles. The robot is permitted to manipulate unspecified obstacles in order to create space for a path. A plan is an ordered sequence of paths for robot motion and object manipulation. We show that under monotone assumptions, anticipating future manipulation paths results in constraints on both the choice of objects and their placements at earlier stages in the plan. We present an algorithm that uses this observation to incrementally reduce the search space and quickly find solutions to previously unsolved classes of movable obstacle problems. Our planner is developed for arbitrary robot geometry and kinematics. It is presented with an implementa tion for the domain of navigation among movable obstacles.

Repeated signaling games

I analyze a class of repeated signaling games in which the informed player's type is persistent and the history of actions is perfectly observable. In this context, a large class of possibly complex sequences of signals can be supported as the separating equilibrium actions of the “strong type” of the informed player. I characterize the set of such sequences. I also characterize the sequences of signals in least cost separating equilibria (LCSE) of these games. In doing this, I introduce a state variable that can be interpreted as a measure of reputation. This gives the optimization problem characterizing the LCSE a recursive structure. I show that, in general, the equilibrium path sequences of signals have a simple structure. The shapes of the optimal sequences depend critically on the relative concavities of the payoff functions of different types, which measure the relative preferences towards payoff smoothing.

Surf"s Up: The Project Management Process

The web sites presented here provide information about project management. This includes information about tools and techniques such as earned value assessment, critical chain evaluation, critical path sequence analysis, risk control, quality auditing, and best practices for communicating with collocated or virtual teams. Also, they address training options and benefits of professional certification.

On the pebbling threshold of paths and the pebbling threshold spectrum

A configuration of pebbles on the vertices of a graph is solvable if one can place a pebble on any given root vertex via a sequence of pebbling steps. A function is a pebbling threshold for a sequence of graphs if a randomly chosen configuration of asymptotically more pebbles is almost surely solvable, while one of asymptotically fewer pebbles is almost surely not. In this paper we tighten the gap between the upper and lower bounds for the pebbling threshold for the sequence of paths in the multiset model. We also find the pebbling threshold for the sequence of paths in the binomial model. Finally, we show that the spectrum of pebbling thresholds for graph sequences in the multiset model spans the entire range from n 1 / 2 to n, answering a question of Czygrinow, Eaton, Hurlbert and Kayll. What the spectrum looks like above n remains unknown.

Sheet Hemming with Rolling Tools: Analysis and Optimization of the Part Quality

The present paper is the continuation of a research conducted on hemming operations by using rolling tools. Sheet hemming is a joining operation widely used in automotive industry when it is necessary to join two sheet parts (such as the engine hood or the door panels with their internal frame) by plastic deformation of the edge of the outer part. The whole process is characterised by a 90° sheet flanging, a pre-hemming (up to approximately 135°) and the final hemming where the outer sheet edge is bended up to 180° clamping the inner sheet. Hemming processes are normally performed using rigid dies in series production and manually in pre-series and small batch production, due to the high cost of the dies. Nowadays, rollers moved by robots are becoming an interesting alternative to the manual operations especially when flexible productions are required. Even if the process time is higher, this solution can help in minimizing set-up times and costs. The required equipments are a support and a blocking system for the sheets together with the rollers mounted on a CNC machine or on a robot. The production flexibility is guaranteed by changing the 3D tool path using a CAD/CAM system. Authors are dealing with this technique having conducted many experiments studying the influence of the hemming process parameters such as flange geometry (edge height, fillet radius), distance of the inner panel from the flange, tool path sequence, along straight paths on steel sheets. The goal of the present research is to study the material behaviour and the produced parts quality when working on aluminium sheets. In particular, both experimental tests and simulations will be carried out in order to optimize the process.

Experimental investigation of the intermediates of isooctane during ignition

AbstractDirect measurements of intermediates of ignition are challenging experimental objectives, yet such measurements are critical for understanding fuel decomposition and oxidation pathways. In the current work, a new gas‐sampling system is used to provide quantitative discrete measurements of 30 hydrocarbon and oxygenate species during rapid compression facility studies of isooctane ignition. Two target conditions and equivalence ratios (based on molar fuel to oxygen ratio) were studied (P = 5.2 atm, T = 1000 K, ϕ = 0.4 and P = 4.8 atm, T = 975 K, ϕ = 1.2). The results are compared with model predictions that use the detailed reaction mechanism developed by Curran et al. (Combust Flame 2002, 129, 253–280). In general, the model predictions are in excellent agreement with the experimental data, including several trace species. Isobutene (i‐C4H8) and propene (C3H6) were the major olefin species identified in the experiments. The results are consistent with an intermediate temperature reaction path sequence, where isooctane is consumed by H‐atom abstraction to yield isooctyl radicals that undergo β‐scission to form olefin and alkyl radical species. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 498–517, 2007

Allelic Association and Recombination Hotspots in the Mucin Gene (MUC) Complex on Chromosome 11p15.5

A family of four highly polymorphic genes encoding secreted gel forming mucins is located in the middle of a recombination rich region of the short arm of chromosome 11 (11p15.5; tel MUC6-MUC2-MUC5AC-MUC5B cen; approx. 400 kb). These genes are of interest as risk factors for inflammatory diseases of the epithelia, and we have for example reported association of a VNTR polymorphism of the major mucin domain of MUC2 with asthma, despite the fact that MUC2 is not a major respiratory mucin. To understand the significance of this and other mucin gene associations it is important to describe the patterns of linkage disequilibrium (LD) across this chromosomal region, which is still incomplete on HapMap and the UCSC Golden Path sequence. Our previous studies on the 40 core CEPH families provided direct evidence for several recombination events within the immediate region of the gene complex. This study examines these recombination events in more detail, and also the patterns of LD across the gene complex. We refine the location of the breakpoints, and the combined data suggest two probable recombination hotspots. Three breakpoints are located between MUC6 and MUC2: there is no association between MUC6 and MUC2, and the data collected here, combined with that publicly available, maps a hotspot to a region of 4 kb. The other recombinants map between MUC2 and intron 8 of MUC5B. Relatively strong LD is detected between MUC2 and MUC5AC, and although 10/70 of the chromosomes tested shared a common haplotype, which extends from MUC2 to MUC5B, statistically significant association was not detected between MUC2 and the markers tested in MUC5B. We discuss the possibility that the previously reported association between MUC2 and asthma is most likely attributable to association with functional variation in MUC5AC, which encodes one of the two major mucins expressed in both healthy and diseased airways.

Good rough path sequences and applications to anticipating stochastic calculus

We consider anticipative Stratonovich stochastic differential equations driven by some stochastic process lifted to a rough path. Neither adaptedness of initial point and vector fields nor commuting conditions between vector field is assumed. Under a simple condition on the stochastic process, we show that the unique solution of the above SDE understood in the rough path sense is actually a Stratonovich solution. We then show that this condition is satisfied by the Brownian motion. As application, we obtain rather flexible results such as support theorems, large deviation principles and Wong--Zakai approximations for SDEs driven by Brownian motion along anticipating vectorfields. In particular, this unifies many results on anticipative SDEs.

Online linear optimization and adaptive routing

This paper studies an online linear optimization problem generalizing the multi-armed bandit problem. Motivated primarily by the task of designing adaptive routing algorithms for overlay networks, we present two randomized online algorithms for selecting a sequence of routing paths in a network with unknown edge delays varying adversarially over time. In contrast with earlier work on this problem, we assume that the only feedback after choosing such a path is the total end-to-end delay of the selected path. We present two algorithms whose regret is sublinear in the number of trials and polynomial in the size of the network. The first of these algorithms generalizes to solve any online linear optimization problem, given an oracle for optimizing linear functions over the set of strategies; our work may thus be interpreted as a general-purpose reduction from offline to online linear optimization. A key element of this algorithm is the notion of a barycentric spanner, a special type of basis for the vector space of strategies which allows any feasible strategy to be expressed as a linear combination of basis vectors using bounded coefficients. We also present a second algorithm for the online shortest path problem, which solves the problem using a chain of online decision oracles, one at each node of the graph. This has several advantages over the online linear optimization approach. First, it is effective against an adaptive adversary, whereas our linear optimization algorithm assumes an oblivious adversary. Second, even in the case of an oblivious adversary, the second algorithm performs slightly better than the first, as measured by their additive regret.

Quiver Poisson algebras

Inner Poisson algebras on a given associative algebra are introduced and characterized, which gives a way of constructing non-commutative Poisson structures. Applying these to the finite-dimensional path algebras k Q → , together with the decomposition into indecomposable Lie ideals of the standard Poisson structure on k Q → , we classify all the inner Poisson structures on k Q → , which turn out to be the piecewise standard Poisson algebras. We also determine all the finite quivers Q → without oriented cycles such that k Q → admits outer Poisson structures: these are exactly the finite quivers without oriented cycles such that there exist two non-trivial paths α and β lying in a reduced closed walk, which cannot be connected by a sequence of non-trivial paths.

Interference-free toolpath generation using enveloping element for five-axis machining of spatial cam

This paper presents an interference-free toolpath generating method for five-axis machining of a spatial cam. The notion of the proposed method is that the cutting tool is confined within the meshing element and the motion of the cutting tool follows the meshing element so that collision problem can be avoided. Based on the envelope theory, homogeneous coordinate transformation and differential geometry, the cutter location using the conical end mill is derived and the cutting path sequences with the minimum lead in and lead out are planned. Curvatures of the cam surface and the cutting tool are evaluated to offer the criterion for interference checking. To ensure the machining accuracy, the scallop height is used as a basis for generating appropriate toolpaths. The cutting simulations with solid model are performed to verify the proposed toolpath generation method. The proposed methodology can be used to automate the programming of tool paths for five-axis machining of spatial cam.

An optimized modular neural network controller based on environment classification and selective sensor usage for mobile robot reactive navigation

A new approach to the design of a neural network (NN) based navigator is proposed in which the mobile robot travels to a pre-defined goal position safely and efficiently without any prior map of the environment. This navigator can be optimized for any user-defined objective function through the use of an evolutionary algorithm. The motivation of this research is to develop an efficient methodology for general goal-directed navigation in generic indoor environments as opposed to learning specialized primitive behaviors in a limited environment. To this end, a modular NN has been employed to achieve the necessary generalization capability across a variety of indoor environments. Herein, each NN module takes charge of navigating in a specialized local environment, which is the result of decomposing the whole path into a sequence of local paths through clustering of all the possible environments. We verify the efficacy of the proposed algorithm over a variety of both simulated and real unstructured indoor environments using our autonomous mobile robot platform.

Interdiffusion Kinetics in the Mo<SUB>5</SUB>SiB<SUB>2</SUB> (T<SUB>2</SUB>) Phase

Diffusion couples based on Mo2B and Mo5Si3 were used to determine the diffusion kinetics of T2 phase development and the relative diffusivities controlling the kinetics. Annealing the Mo2B/Mo5Si3 diffusion couple above 1600 °C yielded an initial diffusion path sequence of Mo2B/T2/Mo3Si/Mo5Si3, which was subsequently transformed to Mo2B/T2/(Mo3Si+Mo5Si3)/Mo5Si3 by shrinkage of the Mo3Si phase upon long-term annealing. The T2 phase developed from Mo2B and during the growth of the T2 phase, Si and B atom movements were driven by the Si concentration gradient. The activation energy for Si interdiffusion in the T2 phase was evaluated to be 355 kJ/mole compared with about 300 kJ/mole for Mo5Si3 in both Mo/Si and MoSi2/T2 diffusion couples. The larger activation energy is mainly responsible for the 103 lower diffusivity for Si in the T2 phase compared with Mo5Si3. The relatively slow diffusion in the T2 phase is consistent with the enhanced creep resistance exhibited by T2 phase microstructures.

Interdiffusion kinetics in the Mo5SiB2 (T2) phase

Diffusion couples based on Mo2B and Mo5Si3 were used to determine the diffusion kinetics of T2 phase development and the relative diffusivities controlling the kinetics. Annealing the Mo2B/Mo5Si3 diffusion couple above 1600 °C yielded an initial diffusion path sequence of Mo2B/T2/Mo3Si/Mo5Si3, which was subsequently transformed to Mo2B/T2/(Mo3Si+Mo5Si3)/Mo5Si3 by shrinkage of the Mo3Si phase upon long-term annealing. The T2 phase developed from Mo2B and during the growth of the T2 phase, Si and B atom movements were driven by the Si concentration gradient. The activation energy for Si interdiffusion in the T2 phase was evaluated to be 355 kJ/mole compared with about 300 kJ/mole for Mo5Si3 in both Mo/Si and MoSi2/T2 diffusion couples. The larger activation energy is mainly responsible for the 103 lower diffusivity for Si in the T2 phase compared with Mo5Si3. The relatively slow diffusion in the T2 phase is consistent with the enhanced creep resistance exhibited by T2 phase microstructures.

Multiaxial fatigue behavior of Ni-based superalloy GH4169 at 650 °C

The fatigue behavior of a Ni-based superalloy GH4169 was investigated using thin tubular specimens under multiaxial loading at 650 °C. Fatigue testing included multiaxial constant amplitude loading and variable amplitude block loading. The test results showed that the characteristics of cyclic hardening or softening depended on the strain loading paths, the sequence of the loading paths, and the loading parameters. Additional hardening due to non-proportional cyclic loading was still present at 650 °C, which caused the fatigue life to decrease. The sequence of the loading paths has an obvious influence on fatigue life, as shown by the increase in loading strain amplitude. Creep effect was observed in the multiaxial fatigue process at high temperature, and an increase in the number of cycles gradually strengthened the creep effect. Fractography showed intergranular fracture phenomena, which reflects the fatigue–creep behavior under non-proportional cyclic loading at high temperature.

Strain path change effect on dislocation microstructure of multicrystalline copper sheets

In this study, coarse-grained copper sheets were subjected to tension–rolling and rolling–tension strain path sequences. In both cases, two different types of strain path change were studied: the tensile and rolling directions were parallel and normal to each other. TEM observations of deformed samples showed the typical dislocation structures for the prestraining paths in tension and rolling. Special microband features, not observed during prestrain, were found during the second strain path, whatever the sequence and type of strain path change. The microstructure observed during reloading is discussed in terms of the sequence and type of strain path change, parallel or normal. The frequency of appearance of microbands is discussed in terms of the activity of new slip systems, i.e. not active during the prestrain path and connected with the number of the active slip systems after reloading. The results from this study, obtained for coarse-grained multicrystalline copper sheets, are compared with previous ones for fine and medium-grained copper.