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Artykuły w czasopismach na temat "Bounded BFS"
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Hernández, Carlos, Jorge A. Baier i Roberto Asín. "Time-Bounded Best-First Search for Reversible and Non-reversible Search Graphs". Journal of Artificial Intelligence Research 56 (6.08.2016): 547–71. http://dx.doi.org/10.1613/jair.5073.
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Time-Bounded A* is a real-time, single-agent, deterministic search algorithm that expands states of a graph in the same order as A* does, but that unlike A* interleaves search and action execution. Known to outperform state-of-the-art real-time search algorithms based on Korf's Learning Real-Time A* (LRTA*) in some benchmarks, it has not been studied in detail and is sometimes not considered as a ``true'' real-time search algorithm since it fails in non-reversible problems even it the goal is still reachable from the current state. In this paper we propose and study Time-Bounded Best-First Search (TB(BFS)) a straightforward generalization of the time-bounded approach to any best-first search algorithm. Furthermore, we propose Restarting Time-Bounded Weighted A* (TB_R(WA*)), an algorithm that deals more adequately with non-reversible search graphs, eliminating ``backtracking moves'' and incorporating search restarts and heuristic learning. In non-reversible problems we prove that TB(BFS) terminates and we deduce cost bounds for the solutions returned by Time-Bounded Weighted A* (TB(WA*)), an instance of TB(BFS). Furthermore, we prove TB_R(WA*), under reasonable conditions, terminates. We evaluate TB(WA) in both grid pathfinding and the 15-puzzle. In addition, we evaluate TB_R(WA*) on the racetrack problem. We compare our algorithms to LSS-LRTWA*, a variant of LRTA* that can exploit lookahead search and a weighted heuristic. A general observation is that the performance of both TB(WA*) and TB_R(WA*) improves as the weight parameter is increased. In addition, our time-bounded algorithms almost always outperform LSS-LRTWA* by a significant margin.
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Hernandez, Carlos, Roberto Asin i Jorge Baier. "Time-Bounded Best-First Search". Proceedings of the International Symposium on Combinatorial Search 5, nr 1 (1.09.2021): 97–104. http://dx.doi.org/10.1609/socs.v5i1.18325.
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Time-Bounded A* (TBA*) is a single-agent deterministic search algorithm that expands states of a graph in the same order as A* does, but that unlike A* interleaves search and action execution. Although the idea underlying TBA* can be generalized to other single-agent deterministic search algorithms, little is known about the impact on performance that would result from using algorithms other than A*. In this paper we propose Time-Bounded Best-First Search (TB-BFS) a generalization of the time-bounded approach to any best-first search algorithm. Furthermore, we propose restarting strategies that allow TB-BFS to solve search problems in dynamic environments. In static environments, we prove that the resulting framework allows agents to always find a solution if such a solution exists, and prove cost bounds for the solutions returned by Time-Bounded Weighted A* (TB-WA*). We evaluate the performance of TB-WA* and Time-Bounded Greedy Best-First Search (TB-GBFS). We show that in pathfinding applications in static domains, TB-WA* and TB-GBFS are not only faster than TBA* but also find significantly better solutions in terms of cost. In the context of videogame pathfinding, TB-WA* and TB-GBFS perform fewer undesired movements than TBA*. Restarting TB-WA* was also evaluated in dynamic pathfinding random maps, where we also observed improved performance compared to restarting TBA*. Our experimental results seem consistent with theoretical bounds.
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Qiu, Agen, Zhiran Zhang, Xinlin Qian i Wangjun He. "Error-bounded and Number-bounded Approximate Spatial Query for Interactive Visualization". Open Geosciences 10, nr 1 (18.09.2018): 491–503. http://dx.doi.org/10.1515/geo-2018-0039.
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AbstractIn the big data era, an enormous amount of spatial and spatiotemporal data are generated every day. However, spatial query result sets that satisfy a query condition are very large, sometimes over hundreds or thousands of terabytes. Interactive visualization of big geospatial data calls for continuous query requests, and large query results prevent visual efficiency. Furthermore, traditional methods based on random sampling or line simplification are not suitable for spatial data visualization with bounded errors and bound vertex numbers. In this paper, we propose a vertex sampling method—the Balanced Douglas Peucker (B-DP) algorithm—to build hierarchical structures, where the order and weights of vertices are preserved in binary trees. Then, we develop query processing algorithms with bounded errors and bounded numbers, where the vertices are retrieved by binary trees’ breadth-first-searching (BFS) with a maximum-error-first (MEF) queue. Finally, we conduct an experimental study with OpenStreetMap (OSM) data to determine the effectiveness of our query method in interactive visualization. The results show that the proposed approach can markedly reduce the query results’ size and maintain high accuracy, and its performance is robust against the data volume.
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Rivera, N., L. Illanes, J. A. Baier i C. Hernandez. "Reconnection with the Ideal Tree: A New Approach to Real-Time Search". Journal of Artificial Intelligence Research 50 (5.06.2014): 235–64. http://dx.doi.org/10.1613/jair.4292.
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Many applications, ranging from video games to dynamic robotics, require solving single-agent, deterministic search problems in partially known environments under very tight time constraints. Real-Time Heuristic Search (RTHS) algorithms are specifically designed for those applications. As a subroutine, most of them invoke a standard, but bounded, search algorithm that searches for the goal. In this paper we present FRIT, a simple approach for single-agent deterministic search problems under tight constraints and partially known environments that unlike traditional RTHS does not search for the goal but rather searches for a path that connects the current state with a so-called ideal tree T . When the agent observes that an arc in the tree cannot be traversed in the actual environment, it removes such an arc from T and then carries out a reconnection search whose objective is to find a path between the current state and any node in T . The reconnection search is done using an algorithm that is passed as a parameter to FRIT. If such a parameter is an RTHS algorithm, then the resulting algorithm can be an RTHS algorithm. We show, in addition, that FRIT may be fed with a (bounded) complete blind-search algorithm. We evaluate our approach over grid pathfinding benchmarks including game maps and mazes. Our results show that FRIT, used with RTAA*, a standard RTHS algorithm, outperforms RTAA* significantly; by one order of magnitude under tight time constraints. In addition, FRIT(daRTAA*) substantially outperforms daRTAA*, a state-of-the-art RTHS algorithm, usually obtaining solutions 50% cheaper on average when performing the same search effort. Finally, FRIT(BFS), i.e., FRIT using breadth-first-search, obtains best-quality solutions when time is limited compared to Adaptive A* and Repeated A*. Finally we show that Bug2, a pathfinding-specific navigation algorithm, outperforms FRIT(BFS) when planning time is extremely limited, but when given more time, the situation reverses.
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Pont-Vílchez, A., F. X. Trias, A. Gorobets i A. Oliva. "Direct numerical simulation of backward-facing step flow at and expansion ratio 2". Journal of Fluid Mechanics 863 (24.01.2019): 341–63. http://dx.doi.org/10.1017/jfm.2018.1000.
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Backward-facing step (BFS) constitutes a canonical configuration to study wall-bounded flows subject to massive expansions produced by abrupt changes in geometry. Recirculation flow regions are common in this type of flow, driving the separated flow to its downstream reattachment. Consequently, strong adverse pressure gradients arise through this process, feeding flow instabilities. Therefore, both phenomena are strongly correlated as the recirculation bubble shape defines how the flow is expanded, and how the pressure rises. In an incompressible flow, this shape depends on the Reynolds value and the expansion ratio. The influence of these two variables on the bubble length is widely studied, presenting an asymptotic behaviour when both parameters are beyond a certain threshold. This is the usual operating point of many practical applications, such as in aeronautical and environmental engineering. Several numerical and experimental studies have been carried out regarding this topic. The existing simulations considering cases beyond the above-mentioned threshold have only been achieved through turbulence modelling, whereas direct numerical simulations (DNS) have been performed only at low Reynolds numbers. Hence, despite the great importance of achieving this threshold, there is a lack of reliable numerical data to assess the accuracy of turbulence models. In this context, a DNS of an incompressible flow over a BFS is presented in this paper, considering a friction Reynolds number ($Re_{\unicode[STIX]{x1D70F}}$) of 395 at the inflow and an expansion ratio 2. Finally, the elongation of the Kelvin–Helmholtz instabilities along the shear layer is also studied.
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Davis, Kevin A., Oleg Lomakin i Michael J. Pesavento. "Response Properties of Single Units in the Dorsal Nucleus of the Lateral Lemniscus of Decerebrate Cats". Journal of Neurophysiology 98, nr 3 (wrzesień 2007): 1475–88. http://dx.doi.org/10.1152/jn.00451.2007.
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The dorsal nucleus of the lateral lemniscus (DNLL) receives afferent inputs from many brain stem nuclei and, in turn, is a major source of inhibitory inputs to the inferior colliculus (IC). The goal of this study was to characterize the monaural and binaural response properties of neurons in the DNLL of unanesthetized decerebrate cat. Monaural responses were classified according to the patterns of excitation and inhibition observed in contralateral and ipsilateral frequency response maps. Binaural classification was based on unit sensitivity to interaural level differences. The results show that units in the DNLL can be grouped into three distinct types. Type v units produce contralateral response maps that show a wide V-shaped excitatory area and no inhibition. These units receive ipsilateral excitation and exhibit binaural facilitation. The contralateral maps of type i units show a more restricted I-shaped region of excitation that is flanked by inhibition. Type o maps display an O-shaped island of excitation at low stimulus levels that is bounded by inhibition at higher levels. Both type i and type o units receive ipsilateral inhibition and exhibit binaural inhibition. Units that produce type v maps have a low best frequency (BF), whereas type i and type o units have high BFs. Type v and type i units give monotonic rate-level responses for both BF tones and broadband noise. Type o units are inhibited by tones at high levels, but are excited by high-level noise. These results show that the DNLL can exert strong, differential effects in the IC.
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Ramachandran, Ramnarayan, Kevin A. Davis i Bradford J. May. "Single-Unit Responses in the Inferior Colliculus of Decerebrate Cats I. Classification Based on Frequency Response Maps". Journal of Neurophysiology 82, nr 1 (1.07.1999): 152–63. http://dx.doi.org/10.1152/jn.1999.82.1.152.
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This study proposes a classification system for neurons in the central nucleus of the inferior colliculus (ICC) that is based on excitation and inhibition patterns of single-unit responses in decerebrate cats. The decerebrate preparation allowed extensive characterization of physiological response types without the confounding effects of anesthesia. The tone-driven discharge rates of individual units were measured across a range of frequencies and levels to map excitatory and inhibitory response areas for contralateral monaural stimulation. The resulting frequency response maps can be grouped into the following three populations: type V maps exhibit a wide V-shaped excitatory area and no inhibition; type I maps show a more restricted I-shaped region of excitation that is flanked by inhibition at lower and higher frequencies; and type O maps display an O-shaped island of excitation at low stimulus levels that is bounded by inhibition at higher levels. Units that produce a type V map typically have a low best frequency (BF: the most sensitive frequency), a low rate of spontaneous activity, and monotonic rate-level functions for both BF tones and broadband noise. Type I and type O units have BFs that span the cat’s range of audible frequencies and high rates of spontaneous activity. Like type V units, type I units are excited by BF tones and noise at all levels, but their rate-level functions may become nonmonotonic at high levels. Type O units are inhibited by BF tones and noise at high levels. The existence of distinct response types is consistent with a conceptual model in which the unit types receive dominant inputs from different sources and shows that these functionally segregated pathways are specialized to play complementary roles in the processing of auditory information.
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Clarey, J. C., P. Barone, W. A. Irons, F. K. Samson i T. J. Imig. "Comparison of noise and tone azimuth tuning of neurons in cat primary auditory cortex and medical geniculate body". Journal of Neurophysiology 74, nr 3 (1.09.1995): 961–80. http://dx.doi.org/10.1152/jn.1995.74.3.961.
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1. A comparison of the azimuth tuning of single neurons to broadband noise and to best frequency (BF) tone bursts was made in primary auditory cortex (AI: n = 173) and the medial geniculate body (MGB: n = 52) of barbiturate-anesthetized cats. Observations were largely restricted to cells located within the tonotopically organized divisions of the MGB (i.e., the ventral nucleus and the lateral division of the posterior nuclear group) and the middle layers of AI. All cells studied had BFs > or = 4 kHz. 2. The responses of each cell to sounds presented from seven frontal azimuthal locations (-90 to +90 degrees in 30 degrees steps; 0 degree elevation) and at five sound pressure levels (SPLs: 0-80 dB or 5-85 dB in 20-dB steps) provided an azimuth-level data set. Responses were averaged over SPL to obtain an azimuth function, and a number of features of this function were used to describe azimuth tuning to noise and to tone stimulation. Azimuth function modulation was used to assess azimuth sensitivity, and cells were categorized as sensitive or insensitive depending on whether modulation was > or = 75% or < 75% of maximum, respectively. The majority (88%) of cells in the sample were azimuth sensitive to noise stimulation, and statistical analyses were restricted to these cells, which are presumably best suited to encode sound source azimuth. Azimuth selectivity was assessed by a preferred azimuth range (PAR) over which azimuth function values exceeded 75% (PAR75) or 50% of maximum response. Cells were categorized according to the location and extent of their noise PARs. Unbounded cells had laterally located PARs that extended to the lateral pole (+/- 90 degrees); bounded cells had PARs that were contained entirely within the frontal hemifield, and a subset of these had PARs centered on the midline (+/- 15 degrees). A final group of cells exhibited multipeaked azimuth functions to noise stimulation. 3. Azimuth functions to noise were generally more selective and/or more sensitive than those to tones. Statistical analyses showed that these differences were significant for cells in each azimuth function category, and for the thalamic and cortical samples. With the exception of multipeaked cells, responsiveness to noise was significantly lower than that to tones in all categories, and for the thalamic and cortical samples.(ABSTRACT TRUNCATED AT 400 WORDS)
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Detomi, Eloisa, Marta Morigi i Pavel Shumyatsky. "BFC-theorems for higher commutator subgroups". Quarterly Journal of Mathematics 70, nr 3 (28.12.2018): 849–58. http://dx.doi.org/10.1093/qmath/hay068.
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Abstract A BFC-group is a group in which all conjugacy classes are finite with bounded size. In 1954, B. H. Neumann discovered that if G is a BFC-group then the derived group G′ is finite. Let w=w(x1,…,xn) be a multilinear commutator. We study groups in which the conjugacy classes containing w-values are finite of bounded order. Let G be a group and let w(G) be the verbal subgroup of G generated by all w-values. We prove that if |xG|≤m for every w-value x, then the derived subgroup of w(G) is finite of order bounded by a function of m and n. If |xw(G)|≤m for every w-value x, then [w(w(G)),w(G)] is finite of order bounded by a function of m and n.
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Alon, Noga, Yossi Azar i Mark Berlin. "The Price of Bounded Preemption". ACM Transactions on Parallel Computing 8, nr 1 (kwiecień 2021): 1–21. http://dx.doi.org/10.1145/3434377.
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In this article we provide a tight bound for the price of preemption for scheduling jobs on a single machine (or multiple machines). The input consists of a set of jobs to be scheduled and of an integer parameter k ≥ 1. Each job has a release time, deadline, length (also called processing time), and value associated with it. The goal is to feasibly schedule a subset of the jobs so that their total value is maximal; while preemption of a job is permitted, a job may be preempted no more than k times. The price of preemption is the worst possible (i.e., largest) ratio of the optimal non-bounded-preemptive scheduling to the optimal k -bounded-preemptive scheduling. Our results show that allowing at most k preemptions suffices to guarantee a Θ(min {log k +1 n , log k +1 P }) fraction of the total value achieved when the number of preemptions is unrestricted (where n is the number of the jobs and P the ratio of the maximal length to the minimal length), giving us an upper bound for the price; a specific scenario serves to prove the tightness of this bound. We further show that when no preemptions are permitted at all (i.e., k =0), the price is Θ (min { n , log P }). As part of the proof, we introduce the notion of the Bounded-Degree Ancestor-Free Sub-Forest (BAS) . We investigate the problem of computing the maximal-value BAS of a given forest and give a tight bound for the loss factor, which is Θ(log k +1 n ) as well, where n is the size of the original forest and k is the bound on the degree of the sub-forest.
Rozprawy doktorskie na temat "Bounded BFS"
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Smith, Timothy D. Tomasini Nathan. "Profiles of Bowl Championship Series (BCS) bowl bound teams from 1998 through 2004". Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2006. http://dc.lib.unc.edu/u?/etd,122.
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Thesis (M.A.)--University of North Carolina at Chapel Hill, 2006.Title from electronic title page (viewed Oct. 10, 2007). "... in partial fulfillment of the requirements for the degree of Master of Arts in the Department of Exercise and Sport Science (Sport Administration)." Discipline: Exercise and Sports Science; Department/School: Exercise and Sport Science.
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Raja, Ravi. "Boolean Functional Synthesis using Gated Continuous Logic Networks". Thesis, 2022. https://etd.iisc.ac.in/handle/2005/5918.
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Boolean Functional Synthesis (BFS) is a well-known challenging problem in the domain of automated program synthesis from logical specifications. This problem aims to synthesize a Boolean function that is correct-by-construction with respect to the declared specification; this specification symbolically relates the inputs and outputs of the function to be synthesized. Since Boolean functions are the basic building blocks of modern digital systems, BFS has applications in a wide range of areas, including QBF-SAT solving, circuit repair and debugging. This has motivated the community to develop practically efficient algorithms for synthesizing compact Boolean functions, which is a non-trivial endeavor. However, to the best of our knowledge, current techniques are unable to specify a bound on the Boolean function size during synthesis. Specifying a bound on the size of the formula offers flexibility in synthesizing minimal-sized Boolean functions.
Learning Boolean functions from logical specifications using neural networks is a difficult problem as it requires the network to represent Boolean functions. Boolean functions are discrete functions and consequently, non-differentiable. Thus, learning a Boolean function directly using traditional neural networks is not possible. Recently Ryan et al proposed the Gated Continuous Logic Network (GCLN) model that builds on Fuzzy Logic to represent Boolean and linear integer operator, in the context of learning invariants for programs. In this work, we investigate the use of the GCLN model to synthesize solutions to the BFS problem. Our model lets us bound the number of clauses used in the synthesized Boolean function.
We implement this approach in our tool BNSynth (for Bounded Neural Synthesis) which also uses sampling and counter-example-guided techniques to synthesize Boolean functions. We validate our hypothesis that this system can learn smaller functions as compared to a state-of-the-art tool over custom benchmarks and LUT-based benchmarks from the ISCAS85 benchmark suite. We observe a 15.8X average improvement in formula size by the number of clauses for these benchmarks. This empirically shows that our system can synthesize smaller Boolean functions compared to the state-of-the-art.
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Ethamakula, Bharath Kumar. "Asymptotic Lower Bound for Quasi Transitive Codes over Cubic Finite Fields". Thesis, 2015. http://etd.iisc.ac.in/handle/2005/3821.
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Algebraic geometric codes were first introduced by V.D.Goppa . They were well recognized and developed by Tsfasman, Vladut and Zink because they have parameters better than Gilbert-Varshmov bound and thus giving rise to Tsfasman Vladut-Zink bound. While the codes given by Ihara, Tsfasman, Vladut and Zink have complicated construction, Garcia and Stichtenoth on the other hand gave an explicit construction of codes attaining Tsfasman-Vlasut-Zink bound using the terminology of function fields. In coding theory one of the challenging problem is to find a sequence of cyclic codes that are asymptotically good. While this has not been achieved, Stichtenoth generalized cyclic codes to transitive codes and constructed a sequence of asymptotically good transitive codes on algebraic function fields over quadratic finite fields that attain Tsfasman-Vladut-Zink bound.
In the case of cubic finite fields, Bezerra, Garcia and Stichtenoth constructed a tower of function fields over cubic finite fields whose limit attains a lower bound and the codes constructed over this tower turns out to be asymptotically good attaining a positive lower bound. Bassa used this tower and constructed quasi transitive codes which are a generalization of transitive codes and proved that they are also asymptotically good and attain the same positive lower bound. Later Bassa, Garcia and Stichtenoth constructed a new tower of function fields over cubic finite fields whose structure is less complicated compared to that of Bezerra, Garcia and Stichtenoths' and proved that codes constructed over it also attain the same positive lower bound. In this work along the lines of Bassa and Stichtenoth we construct quasi transitive codes over the tower given by Bassa, Garcia and Stichtenoth and prove that these quasi transitive codes are also asymptotically good and also attain the same lower bound.
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Ethamakula, Bharath Kumar. "Asymptotic Lower Bound for Quasi Transitive Codes over Cubic Finite Fields". Thesis, 2015. http://etd.iisc.ernet.in/2005/3821.
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Algebraic geometric codes were first introduced by V.D.Goppa . They were well recognized and developed by Tsfasman, Vladut and Zink because they have parameters better than Gilbert-Varshmov bound and thus giving rise to Tsfasman Vladut-Zink bound. While the codes given by Ihara, Tsfasman, Vladut and Zink have complicated construction, Garcia and Stichtenoth on the other hand gave an explicit construction of codes attaining Tsfasman-Vlasut-Zink bound using the terminology of function fields. In coding theory one of the challenging problem is to find a sequence of cyclic codes that are asymptotically good. While this has not been achieved, Stichtenoth generalized cyclic codes to transitive codes and constructed a sequence of asymptotically good transitive codes on algebraic function fields over quadratic finite fields that attain Tsfasman-Vladut-Zink bound.
In the case of cubic finite fields, Bezerra, Garcia and Stichtenoth constructed a tower of function fields over cubic finite fields whose limit attains a lower bound and the codes constructed over this tower turns out to be asymptotically good attaining a positive lower bound. Bassa used this tower and constructed quasi transitive codes which are a generalization of transitive codes and proved that they are also asymptotically good and attain the same positive lower bound. Later Bassa, Garcia and Stichtenoth constructed a new tower of function fields over cubic finite fields whose structure is less complicated compared to that of Bezerra, Garcia and Stichtenoths' and proved that codes constructed over it also attain the same positive lower bound. In this work along the lines of Bassa and Stichtenoth we construct quasi transitive codes over the tower given by Bassa, Garcia and Stichtenoth and prove that these quasi transitive codes are also asymptotically good and also attain the same lower bound.
Książki na temat "Bounded BFS"
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Cohan, Steven. Imaginary Hollywood. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780190865788.003.0003.
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This chapter examines the back-and-forth shifts in how backstudios have imagined Hollywood as the glamorous site of film production. It first looks at how Hollywood is imagined in early backstudios as a specific locale on or near Hollywood Boulevard and accessible by motor car or bus. This view gets complicated by Hollywood’s also being exemplified by the bounded studio compound, with its restrictiveness and regulation, personified by the guard at the front gate. Finally, by the 1940s, when a studio setting becomes synonymous with Hollywood regardless of its location in the Los Angeles area, Hollywood is rendered as a state of mind. It provides a principle of inclusion and exclusion, its mystique and industrial infrastructure protecting those within its orbit and, at the same time, exposing the marginality and vulnerability of those kept out. The multiple examples cited here range from Show People (1928) through La La Land (2016).
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Maggiore, Michele. Gravitational Waves. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198570899.001.0001.
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A comprehensive and detailed account of the physics of gravitational waves and their role in astrophysics and cosmology. The part on astrophysical sources of gravitational waves includes chapters on GWs from supernovae, neutron stars (neutron star normal modes, CFS instability, r-modes), black-hole perturbation theory (Regge-Wheeler and Zerilli equations, Teukoslky equation for rotating BHs, quasi-normal modes) coalescing compact binaries (effective one-body formalism, numerical relativity), discovery of gravitational waves at the advanced LIGO interferometers (discoveries of GW150914, GW151226, tests of general relativity, astrophysical implications), supermassive black holes (supermassive black-hole binaries, EMRI, relevance for LISA and pulsar timing arrays). The part on gravitational waves and cosmology include discussions of FRW cosmology, cosmological perturbation theory (helicity decomposition, scalar and tensor perturbations, Bardeen variables, power spectra, transfer functions for scalar and tensor modes), the effects of GWs on the Cosmic Microwave Background (ISW effect, CMB polarization, E and B modes), inflation (amplification of vacuum fluctuations, quantum fields in curved space, generation of scalar and tensor perturbations, Mukhanov-Sasaki equation,reheating, preheating), stochastic backgrounds of cosmological origin (phase transitions, cosmic strings, alternatives to inflation, bounds on primordial GWs) and search of stochastic backgrounds with Pulsar Timing Arrays (PTA).
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Horing, Norman J. Morgenstern. Superfluidity and Superconductivity. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198791942.003.0013.
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Chapter 13 addresses Bose condensation in superfluids (and superconductors), which involves the field operator ψ having a c-number component (<ψ(x,t)>≠0), challenging number conservation. The nonlinear Gross-Pitaevskii equation is derived for this condensate wave function<ψ>=ψ−ψ˜, facilitating identification of the coherence length and the core region of vortex motion. The noncondensate Green’s function G˜1(1,1′)=−i<(ψ˜(1)ψ˜+(1′))+> and the nonvanishing anomalous correlation function F˜∗(2,1′)=−i<(ψ˜+(2)ψ˜+(1′))+> describe the dynamics and elementary excitations of the non-condensate states and are discussed in conjunction with Landau’s criterion for viscosity. Associated concepts of off-diagonal long-range order and the interpretation of <ψ> as a superfluid order parameter are also introduced. Anderson’s Bose-condensed state, as a phase-coherent wave packet superposition of number states, resolves issues of number conservation. Superconductivity involves bound Cooper pairs of electrons capable of Bose condensation and superfluid behavior. Correspondingly, the two-particle Green’s function has a term involving a product of anomalous bound-Cooper-pair condensate wave functions of the type F(1,2)=−i<(ψ(1)ψ(2))+>≠0, such that G2(1,2;1′,2′)=F(1,2)F+(1′,2′)+G˜2(1,2;1′,2′). Here, G˜2 describes the dynamics/excitations of the non-superfluid-condensate states, while nonvanishing F,F+ represent a phase-coherent wave packet superposition of Cooper-pair number states and off-diagonal long range order. Employing this form of G2 in the G1-equation couples the condensed state with the non-condensate excitations. Taken jointly with the dynamical equation for F(1,2), this leads to the Gorkov equations, encompassing the Bardeen–Cooper–Schrieffer (BCS) energy gap, critical temperature, and Bogoliubov-de Gennes eigenfunction Bogoliubons. Superconductor thermodynamics and critical magnetic field are discussed. For a weak magnetic field, the Gorkov-equations lead to Ginzburg–Landau theory and a nonlinear Schrödinger-like equation for the pair wave function and the associated supercurrent, along with identification of the Cooper pair density. Furthermore, Chapter 13 addresses the apparent lack of gauge invariance of London theory with an elegant variational analysis involving re-gauging the potentials, yielding a manifestly gauge invariant generalization of the London equation. Consistency with the equation of continuity implies the existence of Anderson’s acoustic normal mode, which is supplanted by the plasmon for Coulomb interaction. Type II superconductors and the penetration (and interaction) of quantized magnetic flux lines are also discussed. Finally, Chapter 13 addresses Josephson tunneling between superconductors.
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Benestad, Rasmus. Climate in the Barents Region. Oxford University Press, 2018. http://dx.doi.org/10.1093/acrefore/9780190228620.013.655.
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The Barents Sea is a region of the Arctic Ocean named after one of its first known explorers (1594–1597), Willem Barentsz from the Netherlands, although there are accounts of earlier explorations: the Norwegian seafarer Ottar rounded the northern tip of Europe and explored the Barents and White Seas between 870 and 890 ce, a journey followed by a number of Norsemen; Pomors hunted seals and walruses in the region; and Novgorodian merchants engaged in the fur trade. These seafarers were probably the first to accumulate knowledge about the nature of sea ice in the Barents region; however, scientific expeditions and the exploration of the climate of the region had to wait until the invention and employment of scientific instruments such as the thermometer and barometer. Most of the early exploration involved mapping the land and the sea ice and making geographical observations. There were also many unsuccessful attempts to use the Northeast Passage to reach the Bering Strait. The first scientific expeditions involved F. P. Litke (1821±1824), P. K. Pakhtusov (1834±1835), A. K. Tsivol’ka (1837±1839), and Henrik Mohn (1876–1878), who recorded oceanographic, ice, and meteorological conditions.The scientific study of the Barents region and its climate has been spearheaded by a number of campaigns. There were four generations of the International Polar Year (IPY): 1882–1883, 1932–1933, 1957–1958, and 2007–2008. A British polar campaign was launched in July 1945 with Antarctic operations administered by the Colonial Office, renamed as the Falkland Islands Dependencies Survey (FIDS); it included a scientific bureau by 1950. It was rebranded as the British Antarctic Survey (BAS) in 1962 (British Antarctic Survey History leaflet). While BAS had its initial emphasis on the Antarctic, it has also been involved in science projects in the Barents region. The most dedicated mission to the Arctic and the Barents region has been the Arctic Monitoring and Assessment Programme (AMAP), which has commissioned a series of reports on the Arctic climate: the Arctic Climate Impact Assessment (ACIA) report, the Snow Water Ice and Permafrost in the Arctic (SWIPA) report, and the Adaptive Actions in a Changing Arctic (AACA) report.The climate of the Barents Sea is strongly influenced by the warm waters from the Norwegian current bringing heat from the subtropical North Atlantic. The region is 10°C–15°C warmer than the average temperature on the same latitude, and a large part of the Barents Sea is open water even in winter. It is roughly bounded by the Svalbard archipelago, northern Fennoscandia, the Kanin Peninsula, Kolguyev Island, Novaya Zemlya, and Franz Josef Land, and is a shallow ocean basin which constrains physical processes such as currents and convection. To the west, the Greenland Sea forms a buffer region with some of the strongest temperature gradients on earth between Iceland and Greenland. The combination of a strong temperature gradient and westerlies influences air pressure, wind patterns, and storm tracks. The strong temperature contrast between sea ice and open water in the northern part sets the stage for polar lows, as well as heat and moisture exchange between ocean and atmosphere. Glaciers on the Arctic islands generate icebergs, which may drift in the Barents Sea subject to wind and ocean currents.The land encircling the Barents Sea includes regions with permafrost and tundra. Precipitation comes mainly from synoptic storms and weather fronts; it falls as snow in the winter and rain in the summer. The land area is snow-covered in winter, and rivers in the region drain the rainwater and meltwater into the Barents Sea. Pronounced natural variations in the seasonal weather statistics can be linked to variations in the polar jet stream and Rossby waves, which result in a clustering of storm activity, blocking high-pressure systems. The Barents region is subject to rapid climate change due to a “polar amplification,” and observations from Svalbard suggest that the past warming trend ranks among the strongest recorded on earth. The regional change is reinforced by a number of feedback effects, such as receding sea-ice cover and influx of mild moist air from the south.
Części książek na temat "Bounded BFS"
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Havlena, Vojtěch, Ondřej Lengál i Barbora Šmahlíková. "Sky Is Not the Limit". W Tools and Algorithms for the Construction and Analysis of Systems, 118–36. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-99527-0_7.
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AbstractWe propose several heuristics for mitigating one of the main causes of combinatorial explosion in rank-based complementation of Büchi automata (BAs): unnecessarily high bounds on the ranks of states. First, we identify elevator automata, which is a large class of BAs (generalizing semi-deterministic BAs), occurring often in practice, where ranks of states are bounded according to the structure of strongly connected components. The bounds for elevator automata also carry over to general BAs that contain elevator automata as a sub-structure. Second, we introduce two techniques for refining bounds on the ranks of BA states using data-flow analysis of the automaton. We implement out techniques as an extension of the tool Ranker for BA complementation and show that they indeed greatly prune the generated state space, obtaining significantly better results and outperforming other state-of-the-art tools on a large set of benchmarks.
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Majumdar, Rupak, i Zilong Wang. "Bbs: A Phase-Bounded Model Checker for Asynchronous Programs". W Computer Aided Verification, 496–503. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-21690-4_33.
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Baldoni, Roberto, Silvia Bonomi i Amir Soltani Nezhad. "An Algorithm for Implementing BFT Registers in Distributed Systems with Bounded Churn". W Lecture Notes in Computer Science, 32–46. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-24550-3_5.
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Havlena, Vojtěch, Ondřej Lengál, Yong Li, Barbora Šmahlíková i Andrea Turrini. "Modular Mix-and-Match Complementation of Büchi Automata". W Tools and Algorithms for the Construction and Analysis of Systems, 249–70. Cham: Springer Nature Switzerland, 2023. http://dx.doi.org/10.1007/978-3-031-30823-9_13.
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AbstractComplementation of nondeterministic Büchi automata (BAs) is an important problem in automata theory with numerous applications in formal verification, such as termination analysis of programs, model checking, or in decision procedures of some logics. We build on ideas from a recent work on BA determinization by Li et al. and propose a new modular algorithm for BA complementation. Our algorithm allows to combine several BA complementation procedures together, with one procedure for a subset of the BA’s strongly connected components (SCCs). In this way, one can exploit the structure of particular SCCs (such as when they are inherently weak or deterministic) and use more efficient specialized algorithms, regardless of the structure of the whole BA. We give a general framework into which partial complementation procedures can be plugged in, and its instantiation with several algorithms. The framework can, in general, produce a complement with an Emerson-Lei acceptance condition, which can often be more compact. Using the algorithm, we were able to establish an exponentially better new upper bound of $$\mathcal {O}(4^n)$$ O ( 4 n ) for complementation of the recently introduced class of elevator automata. We implemented the algorithm in a prototype and performed a comprehensive set of experiments on a large set of benchmarks, showing that our framework complements well the state of the art and that it can serve as a basis for future efficient BA complementation and inclusion checking algorithms.
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James, Patrick. "Behavioral Political Science". W The Oxford Handbook of Behavioral Political Science, C20.P1—C20.T1. Oxford University Press, 2022. http://dx.doi.org/10.1093/oxfordhb/9780190634131.013.20.
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Abstract Behavioral political science (BPS) is a research enterprise with many accomplishments in place already, such as rigorous concept formation and a wide range of theories that have performed well under various kinds of testing. This chapter, which evaluates the contents of the present volume, unfolds in eight sections. The first section provides an overview of how assessment of BPS will be carried out. Sections two through five review the accomplishments of the major sectors in the present volume: a) bounded rationality and heuristics, b) theories, c) attitudes, and d) methods. The sixth section introduces systemism, a graphic approach toward representation of cause and effect. The seventh section applies systemism in an effort to assemble the contributions from sectors a through d into a visual representation of cause and effect for BPS. An eighth and final section reflects on what has been achieved.
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Mintz, Alex, i Lesley G. Terris. "Introduction". W The Oxford Handbook of Behavioral Political Science, C1.P1—C1.S6. Oxford University Press, 2022. http://dx.doi.org/10.1093/oxfordhb/9780190634131.013.1.
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Abstract Behavioral political science (BPS) is a new approach to political science that is rooted in the belief that concepts, models, and research approaches from different disciplines (such as psychology, economics, communication) can deepen one’s understanding of political behavior and political decision-making (Mintz et al 2021). In recent years, a significant body of literature based in the behavioral approach has emerged, enriching the ways by which a wide range of cognitive, emotional, and motivational factors impact actors’ thinking processes and behavior choices in different strategic, political, and other social settings. This introduction discusses the BPS approach and the ability of behavioral-oriented research to explain many of the phenomena that deviate from the traditional rational choice models that have dominated the field for decades. It presents the chapters included in the four sections of the handbook: bounded rationality and heuristics, theoretical approaches, attitudes, and BPS research methods.
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"Invariant Measure". W Boundedness and Self-Organized Semantics: Theory and Applications, 88–107. IGI Global, 2013. http://dx.doi.org/10.4018/978-1-4666-2202-9.ch005.
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Bounded randomness of mass/energy exchange rates neither presuppose nor selects any specific time scale, thresholds of stability included. Nonetheless, the boundedness of the rates sets certain non-physical correlations among successive increments and thus justifies formation of “sub-walks” on the finest scale. Further, the “U-turns” at the thresholds of stability set certain correlations on the biggest possible scale of a relevant variable. The major question now is how the balance between the universal correlations, set by the “U-turns,” and those of the specific “sub-walks,” set by the bounded randomness, shapes the structure of a BIS that represents the evolutionary pattern of a relevant variable. It is proven that this issue is inherently related to another universal property of complex systems behavior that is power law distributions. It is demonstrated that power law distributions acquire novel understanding in the setting of boundedness: they appear as universal criterion for hierarchical structuring implemented under boundedness.
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"Time Series Invariants under Boundedness". W Boundedness and Self-Organized Semantics: Theory and Applications, 1–28. IGI Global, 2013. http://dx.doi.org/10.4018/978-1-4666-2202-9.ch001.
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It is proven that every zero-mean bounded irregular sequence (BIS) has three invariants, i.e. characteristics which stay the same when the environmental statistics changes. The existence of such invariants answers the question how far they ensure certainty of the obtained knowledge and the range of predictability of stable complex systems behavior in a positive way. The certainty of our knowledge is put to test by the lack of global rule for response makes impossible to adjust a priori the corresponding recording equipment to a long run. Then, it is to be expected that the recorded time series does not match the corresponding signal in a uniform way since the record is subject to local distortion which is generally non-linear and acts non-homogeneously on the recording. In turn, this poses the fundamental question whether it is ever possible to establish and/or predict the properties and the future behavior of the complex systems.
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"Believing Black Students Are College Bound". W No BS (Bad Stats), 107–19. Brill | Sense, 2019. http://dx.doi.org/10.1163/9789004397040_012.
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Minard, Pete. "The Transformation of Fish Acclimatization". W All Things Harmless, Useful, and Ornamental, 121–32. University of North Carolina Press, 2019. http://dx.doi.org/10.5149/northcarolina/9781469651613.003.0009.
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In this chapter, the early twentieth century study of acclimatization in Victoria further explores fish acclimatization and the decentralization of regional fish acclimatization societies; it also recognizes aquaculture as a solution for declining fish stocks. Organizations such as Geelong and Western District Fish Acclimatising Society (GWDFAS), Ballarat Fish Acclimatisation Society (BFAS), and scientist Sir Samuel Wilson, supported fish acclimatization with interest in breeding, protection of fish, and restoring damaged fisheries. A new generation of fisheries scientists like William Saville-Kent documented their experiences and discovered how to professionally manage fisheries. With innovations like these, the emerging Australian nation was inextricably bound to introduced species and environmental change to feed and understand itself, while also constrained by and aware of past mistakes.
Streszczenia konferencji na temat "Bounded BFS"
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Velikorodny, A., G. Duck i P. Oshkai. "Experimental Investigation of Flow Over a Backward-Facing Step in Proximity to a Flexible Wall". W ASME 2009 Pressure Vessels and Piping Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/pvp2009-77266.
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Turbulent flow between a flexible wall and a solid surface containing a backward-facing step (BFS) was investigated using digital particle image velocimetry (PIV) and high-speed photography. Motivation for this study stems from paper manufacturing industry, where high-speed, wall-bounded jets of air are employed in air clamp devices to precisely position moving sheets of paper at the specified locations with respect to other equipment. In the current investigation, stationary sheet of paper under tension was positioned in proximity to the BFS. The incoming air flow emerged from a planar nozzle that was located in the solid wall upstream of the BFS. Curvature of the nozzle wall resulted in a favorable pressure gradient condition. As a result, the flow upstream of the BFS was attached to the solid wall due to the Coanda effect. Flows corresponding to two values of the Reynolds number (3000 and 3600) based on the step height and the maximum flow velocity at the step location were characterized in terms of patterns of instantaneous and time-averaged velocity, out-of-plane vorticity, streamline topology, and turbulence statistics. In addition, paper sheet oscillation was characterized using high-speed photography. Frequencies of the natural vibration modes of the flexible wall (paper sheet) were well separated from the hydrodynamic frequencies corresponding to the oscillations of the shear layer downstream of the BFS, which resulted in the absence of resonance in the system and low characteristic amplitudes of the paper sheet oscillation. In the time-averaged sense, interaction between the separated flow downstream of the BFS and the flexible wall (paper sheet) resulted in deformation of the paper sheet and formation of diverging channel geometry between the sheet and the solid wall. As the inflow velocity increased, the paper sheet was pulled closer to the surface of the air clamp, which resulted in increased confinement of the incoming Coanda jet. The flow reattachment length calculated on the basis of time-averaged flow patterns increased with the increasing Reynolds number.
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Cohen, Liron, Matias Greco, Hang Ma, Carlos Hernandez, Ariel Felner, T. K. Satish Kumar i Sven Koenig. "Anytime Focal Search with Applications". W Twenty-Seventh International Joint Conference on Artificial Intelligence {IJCAI-18}. California: International Joint Conferences on Artificial Intelligence Organization, 2018. http://dx.doi.org/10.24963/ijcai.2018/199.
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Focal search (FS) is a bounded-suboptimal search (BSS) variant of A*. Like A*, it uses an open list whose states are sorted in increasing order of their f-values. Unlike A*, it also uses a focal list containing all states from the open list whose f-values are no larger than a suboptimality factor times the smallest f-value in the open list. In this paper, we develop an anytime version of FS, called anytime FS (AFS), that is useful when deliberation time is limited. AFS finds a "good" solution quickly and refines it to better and better solutions if time allows. It does this refinement efficiently by reusing previous search efforts. On the theoretical side, we show that AFS is bounded suboptimal and that anytime potential search (ATPS/ANA*), a state-of-the-art anytime bounded-cost search (BCS) variant of A*, is a special case of AFS. In doing so, we bridge the gap between anytime search algorithms based on BSS and BCS. We also identify different properties of priority functions, used to sort the focal list, that may allow for efficient reuse of previous search efforts. On the experimental side, we demonstrate the usefulness of AFS for solving hard combinatorial problems, such as the generalized covering traveling salesman problem and the multi-agent pathfinding problem.
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Holen, Peter, i Boris Thorvald. "Aspects on Roll and Bounce Damping for Heavy Vehicles". W International Truck & Bus Meeting & Exhibition. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 2002. http://dx.doi.org/10.4271/2002-01-3060.
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Bonneau, L., T. Kawano, T. Watanabe i S. Chiba. "Direct and semidirect radiative capture of nucleons with Hartree-Fock-BCS bound states". W International Conference on Nuclear Data for Science and Technology. Les Ulis, France: EDP Sciences, 2007. http://dx.doi.org/10.1051/ndata:07310.
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Wacker, Randy. "Fastener Preload Guidance Methodology for ASME B16.5 Welding Neck Flanges". W ASME 2008 Pressure Vessels and Piping Conference. ASMEDC, 2008. http://dx.doi.org/10.1115/pvp2008-61410.
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Various resources have long been available from which bolted flange connection (BFC) preload guidance can be chosen. These range from Rules of Thumb gleaned from experience, to tables and charts based on average gasket stress, to parametric generalizations derived from the results of limited finite element analyses. Because the primary components of a BFC (flange, fastener and gasket) interact with one another to respond as a single system, and the system is unique to the conditions that define it, guidance based on these specific conditions will improve the accuracy of preload solutions and generate data to show the relative strengths and weaknesses of a given BFC. This paper presents a methodology that sets practical stress limits on a collection of commonly used ASME B16.5 welding neck flange components and then uses finite element analysis to solve the condition of preload that results in one or more limits being satisfied. Each preload solution is unique to the properties and geometries that define it and includes the effects of three design conditions. Fastener stress solutions include both the tension and bending components. This shows that yielding can initiate at relatively low values of preload when flange rotation is significant. Charts are created to show solution trends. This simplifies the task of identifying the component that sets the upper bound for a given solution. It also provides the basis to compare similar component combinations.
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Alshuwaikhat, Ali, Ghadah Albalawi, Laila Alshammasi i Yacine Meridji. "A Data-Driven Model for Bound Fluid Prediction in Carbonate Reservoirs". W Middle East Oil, Gas and Geosciences Show. SPE, 2023. http://dx.doi.org/10.2118/213304-ms.
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Abstract The objective of this paper is to develop a machine learning workflow in order to replicate the Nuclear Magnetic Resonance (NMR) bound fluid volumes utilizing triple-combo data. The developed model is to overcome the logging operations challenges and to enhance the petrophysical formation evaluation in carbonate reservoirs and most importantly a proper completion design to avoid free water bearing zones (Dodge et al 1998). The presented data-driven model is based on artificial intelligence (AI) and data mining techniques. In order to select the required data input, many logging parameters were investigated and several iterations with different sets of parameters were attempted to identify those with the most impact on bound fluid volume prediction. Henceforth, the iteration with the lowest root mean square error (RMSE) is to be selected. The model was trained, calibrated and validated to accurately predict the NMR bound fluid volume. The main purpose of this study is to draw attention to the capabilities of the artificial intelligence techniques to provide logging responses with excellent match compared to the measured logs in the event that operational complexities or budget constraints arise. Several wells with excellent data quality were selected from the same field to build and test the RF (Random Forest) model. 56% of the wells were used for training and the remaining 44% were kept for blind tests. During the modeling process, several iterations were attempted to identify what was really driving the BFV prediction, the best model was chosen based on the lowest RMSE (Root Mean Square Error). The model statistics indicated the combination of resistivity, density, neutron, GR, produced the best model with lowest RMSE = 0.78 pu (porosity units). The model was later deployed to the remaining blind test wells, the results were of excellent accuracy when compared to the measured log data with error difference way below the acceptable industry standard of 1 pu. With accurate BFV prediction, free water zones can now be identified and avoided during completion. This methodology will help operators reduce risk, maximize production without straining their budget to acquire NMR logs in every horizontal development well, or even attempt formation tester samples unnecessarily. Implementing this new machine learning methodology will help in increasing the confidence in petrophysical analysis and reservoir management decisions, as well as optimizing the logging runs. This results in cost savings without compromising the quality of the formation evaluation, in addition to minimizing the carbon footprint associated with unnecessary operations.
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Li, Haoxin, i Fang Cheng. "Design and synthesis of a novel albumin-bound PTX liposome system". W International Conference on Biomedical and Intelligent Systems (IC-BIS 2022), redaktor Ahmed El-Hashash. SPIE, 2022. http://dx.doi.org/10.1117/12.2660283.
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Ashwathi, R. "Investigation on Strength Properties of Concrete using Steel Slag as a Partial Replacement for Fine Aggregate". W Sustainable Materials and Smart Practices. Materials Research Forum LLC, 2022. http://dx.doi.org/10.21741/9781644901953-44.
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Abstract. The economic and ecological performance of normal concrete can be increased by modulating fine aggregate content with a series of combinations of steel slag which possess different physical and chemical behaviour based on its cooling method, heating processes. Many research shows that magnetic separating of steel slag increases its efficiency towards integrating with clinker by 50% compared to integrating of clinker with non-magnetically separated steel slag. It has proved to be an impressive replacement material in concrete surfaces where high skid resistance is essential. Steel slag produced in various types of furnaces have different characteristic nature, blast furnace slag (BFS) has hydraulic and cement properties when used in water-bound macadam roads and also in flexible and rigid pavements. Issue in steel slag is energy consumed in its production and transportation where it is utilized, if energy consumed in slag grinding/magnetic separation is high when compared to cement calcining and grinding, then it would not be economical in replacement criteria. This study exhibit mechanical properties of concrete with partial replacement of fine aggregate with steel slag in distinct proportions. The optimum amount of replacement in fine aggregate is found to be 20% giving a strength increment of 8% in the compressive strength category. In split tensile and flexural strength criteria strength increment of 7.5% and 40.625% is observed. There are many practical implications of steel slag in the construction industry, road constructions, and clinker substitutes as granulated BF slag, water treatment plants, evidently many researches have proved slag as productive coarse aggregates replacement.
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Ang, Daniel, George Abraham, Novalia Sidik, Krystalina Sim, Thomas Ford, Colin Berry i Stephen Hoole. "40 Comparing pressure-bound coronary flow reserve versus thermodilution-derived coronary flow reserve". W British Cardiovascular Society Annual Conference, ‘Future-proofing Cardiology for the next 10 years’, 5–7 June 2023. BMJ Publishing Group Ltd and British Cardiovascular Society, 2023. http://dx.doi.org/10.1136/heartjnl-2023-bcs.40.
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Coster, J. E., N. Stander i J. A. Snyman. "Trust Region Augmented Lagrangian Methods With Secant Hessian Updating Applied to Structural Optimization". W ASME 1996 Design Engineering Technical Conferences and Computers in Engineering Conference. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/96-detc/dac-1461.
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Abstract The problem of determining the optimal sizing design of truss structures is considered. An augmented Lagrangian optimization algorithm which uses a quadratic penalty term is formulated. The implementation uses a first-order Lagrange multiplier update and a strategy for progressively increasing the accuracy with which the bound constrained minimizations are performed. The allowed constraint violation is also progressively decreased but at a slower rate so as to prevent ill-conditioning due to large penalty values. Individual constraint penalties are used and only the penalties of the worst violated constraints are increased. The scheme is globally convergent. The bound constrained minimizations are performed using the SBMIN algorithm where a sophisticated trust-region strategy is employed. The Hessian of the augmented Lagrangian function is approximated using partitioned secant updating. Each function contributing to the Lagrangian is individually approximated by a secant update and the augmented Lagrangian Hessian is formed by appropriate accumulation. The performance of the algorithm is evaluated for a number of different secant updates on standard explicit and truss sizing optimization problems. The results show the formulation to be superior to other implementations of augmented Lagrangian methods reported in the literature and that, under certain conditions, the method approaches the performance of the state-of-the-art SQP and SAM methods. Of the secant updates, the symmetric rank one update is superior to the other updates including the BFGS scheme. It is suggested that the individual function, secant updating employed may be usefully applied in contexts where structural analysis and optimization are performed simultaneously, as in the simultaneous analysis and design method. In such cases the functions are partially separable and the associated Hessians are of low rank.
Raporty organizacyjne na temat "Bounded BFS"
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L51635 Optimizing Techniques for CTOD Testing of Girth Welds in Linepipe. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), luty 1991. http://dx.doi.org/10.55274/r0010414.
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Appendix A of the sixteenth edition of API Standard 1104 allows relaxation of the flaw acceptance criteria, as defined in the standard, provided that specified minimum fracture toughness values are achieved (Ref.1). The fracture toughness is measured using the crack tip opening displacement (CTOD) test procedure as described in BS 5762 published by the British Standards Institute. In allowing relaxed defect acceptance criteria, the achievement of a specified CTOD value ensures that the flaws in girth welds will remain stable during installation and service. Thus, despite the presence of flaws, the pipeline can be operated safely without risk of unstable fracture, e.g. brittle fracture. However, to ensure that this is the case, it is vital that the testing procedure be designed to identify and quantify the lowest toughness region. If this is not done, there is a risk that the flaw will sample low toughness material and initiate an unstable fracture leading to failure of the girth weld. This report describes a research program to investigate various notching techniques with the objective of determining the most appropriate method of selecting the notch location for CTOD specimens notched into the HAZ region of pipeline girth welds. It was found that for the weld samples studied in this investigation, the API 1104 Appendix A method of conducting HAZ CTOD tests can produce scattered results and does not necessarily guarantee lower bound estimates of toughness. Of the various notching techniques studied, specimens notched at the intersection of the fusion boundary with the specimen mid-thickness produced the most consistent results.