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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.
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Asperó, David. "A maximal bounded forcing axiom". Journal of Symbolic Logic 67, nr 1 (marzec 2002): 130–42. http://dx.doi.org/10.2178/jsl/1190150034.
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AbstractAfter presenting a general setting in which to look at forcing axioms, we give a hierarchy of generalized bounded forcing axioms that correspond level by level, in consistency strength, with the members of a natural hierarchy of large cardinals below a Mahlo. We give a general construction of models of generalized bounded forcing axioms. Then we consider the bounded forcing axiom for a class of partially ordered sets Γ1 such that, letting Γ0 be the class of all stationary-set-preserving partially ordered sets, one can prove the following:(a) Γ0 ⊆ Γ1,(b) Γ0 = Γ1 if and only if NSω1 is ℵ1-dense.(c) If P ∉ Γ1, then BFA({P}) fails.We call the bounded forcing axiom for Γ1Maximal Bounded Forcing Axiom (MBFA). Finally we prove MBFA consistent relative to the consistency of an inaccessible Σ2-correct cardinal which is a limit of strongly compact cardinals.
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Ibrahim, Ahmad Asrul, Khairuddin Khalid, Hussain Shareef i Nor Azwan Mohamed Kamari. "A Bounded Exhaustive Search Technique for Optimal Phasor Measurement Unit Placement in Power Grids". Symmetry 12, nr 12 (7.12.2020): 2021. http://dx.doi.org/10.3390/sym12122021.
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This paper proposes a technique to determine the possible optimal placement of the phasor measurement unit (PMU) in power grids for normal operating conditions. All possible combinations of PMU placement, including infeasible combinations, are typically considered in finding the optimal solution, which could be a massive search space. An integer search algorithm called the bounded search technique is introduced to reduce the search space in solving a minimum number of PMU allocations whilst maintaining full system observability. The proposed technique is based on connectivity and symmetry constraints that can be derived from the observability matrix. As the technique is coupled with the exhaustive technique, the technique is called the bounded exhaustive search (BES) technique. Several IEEE test systems, namely, IEEE 9-bus, IEEE 14-bus, IEEE 24-bus and IEEE 30-bus, are considered to showcase the performance of the proposed technique. An initial Monte Carlo simulation was carried out to evaluate the capability of the bounded search technique in providing a smaller feasible search space. The effectiveness of the BES technique in terms of computational time is compared with the existing exhaustive technique. Results demonstrate that the search space can be reduced tremendously, and the computational burden can be eased, when finding the optimal PMU placement in power grids.
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Labuda, Iwo. "On functions that are $BDS$-integrable over convexly bounded vector measures". Functiones et Approximatio Commentarii Mathematici 50, nr 1 (marzec 2014): 151–59. http://dx.doi.org/10.7169/facm/2014.50.1.4.
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Mohammadi Hassanabadi, A., i Akbar Rhemtulla. "Criteria for Commutativity in Large Groups". Canadian Mathematical Bulletin 41, nr 1 (1.03.1998): 65–70. http://dx.doi.org/10.4153/cmb-1998-010-0.
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AbstractIn this paper we prove the following:1.Let m ≥ 2, n ≥ 1 be integers and let G be a group such that (XY)n = (YX)n for all subsets X, Y of size m in G. Thena)G is abelian or a BFC-group of finite exponent bounded by a function of m and n.b)If m ≥ n then G is abelian or |G| is bounded by a function of m and n.2.The only non-abelian group G such that (XY)2 = (YX)2 for all subsets X, Y of size 2 in G is the quaternion group of order 8.3.Let m, n be positive integers and G a group such that for all subsets Xi of size m in G. Then G is n-permutable or |G| is bounded by a function of m and n.
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Givler, R. C., i S. A. Altobelli. "A determination of the effective viscosity for the Brinkman–Forchheimer flow model". Journal of Fluid Mechanics 258 (10.01.1994): 355–70. http://dx.doi.org/10.1017/s0022112094003368.
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The effective viscosity μe for the Brinkman–Forchheimer flow (BFF) model has been determined experimentally for steady flow through a wall-bounded porous medium. Nuclear magnetic resonance (NMR) techniques were used to measure non-invasively the ensemble-average velocity profile of water flowing through a tube filled with an open-cell rigid foam of high porosity (ϕ = 0.972). By comparing these data with the BFF model, for which all remaining parameters were measured independently, it was determined that μe = (7.5+3.4−2.4)μf, where μf was the viscosity of the fluid. The Reynolds number, based upon the square root of the permeability, was 17.
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Perfetto, Luca, i Gabriele D’Antona. "Experimental Results of Partial Discharge Localization in Bounded Domains". Sensors 21, nr 3 (30.01.2021): 935. http://dx.doi.org/10.3390/s21030935.
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This work presents a novel diagnostic method to localize Partial Discharges (PDs) inside Medium Voltage (MV) and High Voltage (HV) equipment. The method is well suited for that equipment presenting a bounded domain with fixed Boundary Conditions (BCs) such as Oil-Filled Power Transformers (OFPTs), Air Insulated Switchgears (AISs), Gas Insulated Switchgears (GISs) or Gas Insulated Transmission Lines (GILs). It is based on Electromagnetic (EM) measurements which are used to reconstruct the EM field produced by the PD and localize the PD itself. The reconstruction and localization tasks are based on the eigenfunctions series expansion method which intrinsically accounts for the physical information of the propagation phenomenon. This fact makes the proposed diagnostic method very robust and accurate even in real and complex scenarios. The promising experimental results, obtained in two different test cases, confirmed the ability and powerfulness of the proposed PD localization method.
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Dixon, Martyn R., i Leonid A. Kurdachenko. "GROUPS WITH THE MAXIMAL CONDITION ON NON-BFC SUBGROUPS. II". Proceedings of the Edinburgh Mathematical Society 45, nr 3 (październik 2002): 513–22. http://dx.doi.org/10.1017/s0013091501001043.
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AbstractA group $G$ is called a group with boundedly finite conjugacy classes (or a BFC-group) if $G$ is finite-by-abelian. A group $G$ satisfies the maximal condition on non-BFC-subgroups if every ascending chain of non-BFC-subgroups terminates in finitely many steps. In this paper the authors obtain the structure of finitely generated soluble-by-finite groups with the maximal condition on non-BFC subgroups.AMS 2000 Mathematics subject classification: Primary 20E15. Secondary 20F16; 20F24
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Ojha, Bhuwan Prasad. "A Review of the Tsirleson's Space Norm". Nepali Mathematical Sciences Report 39, nr 2 (31.12.2022): 79–84. http://dx.doi.org/10.3126/nmsr.v39i2.51697.
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In most cases, the space of all sequences converging to zero or the space of bounded sequences is always embedded in complete normed linear spaces. This concept, however, was modified by B.S. Tsirelson by constructing reflexive complete normed linear spaces with monotone unconditional Schauder basis without embedded copies of sequences converging to zero or the space of bounded sequence. In this article, a relation with any four non-negative integers has been proved, and this concept is used to prove the triangle inequality of a slightly different Tsirelson’s type of norm in the space of all real sequences with finite support. Furthermore, all properties of the norm have been studied for a different type of norm function in the space of real sequences with finite support.
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DETOMI, ELOISA, GURAM DONADZE, MARTA MORIGI i PAVEL SHUMYATSKY. "ON FINITE-BY-NILPOTENT GROUPS". Glasgow Mathematical Journal 63, nr 1 (20.12.2019): 54–58. http://dx.doi.org/10.1017/s0017089519000508.
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AbstarctLet γn = [x1,…,xn] be the nth lower central word. Denote by Xn the set of γn -values in a group G and suppose that there is a number m such that $|{g^{{X_n}}}| \le m$ for each g ∈ G. We prove that γn+1(G) has finite (m, n) -bounded order. This generalizes the much-celebrated theorem of B. H. Neumann that says that the commutator subgroup of a BFC-group is finite.
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Navarro, A., i E. R. de los Rios. "Compact solution for a multizone BCS crack model with bounded or unbounded end conditions". Philosophical Magazine A 57, nr 1 (czerwiec 1988): 43–50. http://dx.doi.org/10.1080/01418618808204498.
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Tezcan, I. Egemen, i Tamer Bas¸ar. "Disturbance Attenuating Adaptive Controllers for Parametric Strict Feedback Nonlinear Systems With Output Measurements". Journal of Dynamic Systems, Measurement, and Control 121, nr 1 (1.03.1999): 48–57. http://dx.doi.org/10.1115/1.2802441.
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We present a systematic procedure for designing H∞-optimal adaptive controllers for a class of single-input single-output parametric strict-feedback nonlinear systems that are in the output-feedback form. The uncertain nonlinear system is minimum phase with a known relative degree and known sign of the high-frequency gain. We use soft projection on the parameter estimates to keep them bounded in the absence of persistent excitations. The objective is to obtain disturbance attenuating output-feedback controllers which will track a smooth bounded trajectory and keep all closed-loop signals bounded in the presence of exogenous disturbances. Two recent papers (Pan and Bas¸ar, 1996a; Marino and Tomei, 1995) addressed a similar problem with full state information, using two different approaches, and obtained asymptotically tracking and disturbance-attenuating adaptive controllers. Here, we extend these results to the output measurement case for a class of minimum phase nonlinear systems where the nonlinearities depend only on the measured output. It is shown that arbitrarily small disturbance attenuation levels can be obtained at the expense of increased control effort. The backstepping methodology, cost-to-come function based H∞ -filtering and singular perturbations analysis constitute the framework of our robust adaptive control design scheme.
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Yang, Hua, i James R. Wright. "A Method for Mass Harvesting Islets (Brockmann Bodies) from Teleost Fish". Cell Transplantation 4, nr 6 (listopad 1995): 621–28. http://dx.doi.org/10.1177/096368979500400612.
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In certain species of fish, the insulin-producing tissue is uniquely located in separate structures called Brockmann bodies (BBs). Tilapia BBs have been shown to be a simple and inexpensive source of islet cells for xenotransplantation research. Each donor tilapia contains roughly 12-15 BBs, measuring from 0.3 to 5.0 mm in maximum dimension, in a triangular region of adipose tissue bounded by the liver, stomach, and spleen/gallbladder. At present, the larger BBs (usually 2-4) are harvested by microdissecting these “BB regions” using jeweler's forceps and microvascular scissors while being visualized with the aid of a dissecting microscope. It is a simple but time-consuming task that would not be applicable for harvesting massive amounts of BB tissue for large animal studies. Therefore, we have developed an easier and more efficient method of harvesting BBs based on a standard enzymatic method for isolating human adipocytes. BB regions are harvested from donor fish and pooled into a 50 mL plastic tube containing collagenase Type II (3 mg/mL) in Hank's balanced salt solution (HBSS); the tube is then placed in a 37°C waterbath/shaker for roughly 15 min. The exact length of the digestion interval is determined by visual inspection of the tube to determine whether the BBs have been liberated. The digestion is then stopped by adding excess cold HBSS. The adipocytes float while the BBs and residual connective tissue (i.e., a few blood vessels, nerves, and bile ducts) form a pellet. The pellet is washed several times in HBSS and then placed in a culture dish. The BBs are easily handpicked with a siliconized pipette. Based on functional data and DNA content, this new method roughly doubles or triples our yield of BB tissue per donor fish. To determine whether BBs harvested in this manner functioned in a manner similar to those harvested by microdissection, we performed a series of transplants using mass-harvested BBs. Long-term normoglycemia was achieved in streptozotocin-diabetic nude mice and mean graft survival time was not altered in streptozotocin-diabetic euthymic balb/c mice. However, the total weight of donor fish required per recipient was decreased by 50% in both strains.
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Beresford, Andrew. "Abjection, Marriage, and the Burrowing Worm: The Body as Bounded System in the Dança general de la Muerte". Bulletin of Hispanic Studies 91, nr 8 (styczeń 2014): 965–80. http://dx.doi.org/10.3828/bhs.2014.62.
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Lu, Ma, Liu, Wu i Chen. "A Triple Checked Partial Ambiguity Resolution for GPS/BDS RTK Positioning". Sensors 19, nr 22 (18.11.2019): 5034. http://dx.doi.org/10.3390/s19225034.
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Reliable and accurate carrier phase ambiguity resolution is the key to high-precision Global Navigation Satellite System (GNSS) positioning and application. With the fast development of modern GNSS, the increased number of satellites and ambiguities makes it hard to fix all ambiguities completely and correctly. The partial ambiguity fixing technique, which selects a suitable subset of high-dimensional ambiguities to fix, is beneficial for improving the fixed success rate and reliability of ambiguity resolution. In this contribution, the bootstrapping success rate, bounded fixed-failure ratio test, and the new defined baseline precision defect are used for the selection of the ambiguity subset. Then a model and data dual-driven partial ambiguity resolution method is proposed with the above three checks imposed on it, which is named the Triple Checked Partial Ambiguity Resolution (TC-PAR). The comprehensive performance of TC-PAR compared to the full-fixed LAMBDA method is also analyzed based on several criteria including the fixed rate, the fixed success rate and correct fixed rate of ambiguity as well as the precision defect and RMS of the baseline solution. The results show that TC-PAR could significantly improve the fixed success rate of ambiguity, and it has a comparable baseline precision to the LAMBDA method, both of which are at centimeter level after ambiguities are fixed.
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Steel, Chad M. S. "Web-Based Child Pornography". International Journal of Digital Crime and Forensics 1, nr 4 (październik 2009): 58–69. http://dx.doi.org/10.4018/jdcf.2009062405.
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While the supply of child pornography through the World Wide Web has been frequently speculated upon, the demand has not adequately been explored. Quantification and qualification of the demand provides forensic examiners a behavioral basis for determining the sophistication of individual seeking child pornography. Additionally, the research assists an examiner in searching for and presenting the evidence of child pornography browsing. The overall search engine demand for child pornography is bounded as being between .19 and .49%, depending on the inclusion of ambiguous phrases, with the top search for child pornography being “lolita bbs”. Unlike peer-to-peer networks, however, the top child pornography related query ranks only as the 198th most popular query overall. The queries on search engines appear to be decreasing as well, and the techniques employed are becoming less reliant direct links to content.
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Victor French, J., i Mohamed Rakha. "Flat Mite Control on Texas Citrus, 1993". Arthropod Management Tests 19, nr 1 (1.01.1994): 45. http://dx.doi.org/10.1093/amt/19.1.45a.
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Abstract The experimental acaricides, BAS 300 111 and AC 303,630, were compared to labeled acaricides and insecticides and NR 440 spray oil for efficacy against FM. Treatments were randomly assigned to single tree plots and replicated 4 times in an 8-yr-old commercial grapefruit grove on 15 × 28 ft spacing. Each treatment was bounded on all sides by an unsprayed tree to minimize crosscontamination. Treatment sprays were applied on 30 Aug to foliar runoff (ca. 2 gal/tree) utilizing a Hypro 5200 portable high pressure handgun sprayer equipped with a D-5 nozzle and operating at 200 psi. At each sample date, 6 fruit per replicate were randomly picked from the interior tree canopy and removed to the laboratory. Fruit were examined under a binocular microscope at 20X and all live FM counted and recorded.
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Klose, Jens. "Exchange rate movements in the presence of the zero lower bound". Banks and Bank Systems 12, nr 1 (24.03.2017): 82–87. http://dx.doi.org/10.21511/bbs.12(1).2017.10.
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Exchange rates are expected to adjust according to the stance of monetary policies, which are in normal times differences in interest rates set by the central banks. This interest rate parity does, however, no longer hold if central banks approach the zero lower bound on interest rates and switch to measures of quantitative easing. Therefore, the author estimates exchange rate changes based on the different stance of the monetary base, which is an indicator of differing monetary policies in the countries. The results reveal that indeed exchange rates movements in the Dollar-Euro-Rate can be explained by differences in the monetary base, since the zero lower bound has become binding. However, the influence depends crucially on whether the monetary base is increased or decreased and whether the other central bank is also expanding or reducing its balance sheet at the same time. Keywords: monetary base, exchange rate, Fed, ECB. JEL Classification: E52, E58, F42
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Švorčík, Václav, Zdeňka Kolská, Jakub Siegel i Petr Slepička. "“Short” Dithiol and Au Nanoparticles Grafting on Plasma Treated Polyethyleneterephthalate". Journal of Nano Research 25 (październik 2013): 40–48. http://dx.doi.org/10.4028/www.scientific.net/jnanor.25.40.
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Surface of polyethyleneterephthalate (PET) was modified by plasma discharge and subsequently grafted with dithiol (4,4-bifenyldithiol, BFD)) to create thiol (-SH) groups on polymer surface. This short dithiol is expected to be fixed via one of-SH groups to radicals created by the plasma treatment on the PET surface. Free-SH groups are allowed to interact with Au nanoparticles. Xray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared Spectroscopy (FTIR) and Electrokinetic Analysis (EA, zeta potential) were used for the characterization of surface chemistry of the modified PET. Surface morphology and roughness of the samples were studied by Atomic Force Microscopy (AFM).The results from XPS, FTIR, EA and AFM show that the Au nanoparticles are grafted on modified surface in the case of bifenyldithiol pretreatment. The rigid molecule of biphenyldithiol is bounded via only one-SH group to the modified PET surface and the second one remains free for the consecutive chemical reaction with Au nanoparticle. The gold nanoparticles are distributed relatively homogenously over the polymer surface.
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Moskvin, A. S., i Yu D. Panov. "Phase separation in high-T c cuprates". Journal of Physics: Conference Series 2164, nr 1 (1.03.2022): 012014. http://dx.doi.org/10.1088/1742-6596/2164/1/012014.
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Abstract We develop a minimal non-BCS model for the CuO2 planes with the on-site Hilbert space reduced to only three effective valence centers CuO4 with different charge, conventional spin, and orbital symmetry, combined in a charge triplet, to describe the low-energy electron structure and the phase states of HTSC cuprates. Using the S = 1 pseudospin algebra we introduce an effective spin-pseudospin Hamiltonian which takes into account local and nonlocal correlations, one- and two-particle transport, and spin exchange. The T-n phase diagrams of the complete spin-pseudospin model for the CuO2 planes were reproduced by means of a site-dependent variational approach within effective field approximation typical for spin-magnetic systems. Limiting ourselves to two-sublattice approximation and nn-couplings we arrived at several Néel-like phases in CuO2 planes for parent and doped systems with a single nonzero local order parameter: antiferromagnetic insulator, charge order, glueless d-wave Bose superfluid phase, and unusual metallic phase. However, the Maxwell’s construction shows the global minimum of free energy is realized for phase separated states which are bounded by the third-order phase transition line T*(n), which is believed to be responsible for the onset of the pseudogap phenomenon.
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Delizia, Costantino, Pavel Shumyatsky i Antonio Tortora. "On semiconcise words". Journal of Group Theory 23, nr 4 (1.07.2020): 629–39. http://dx.doi.org/10.1515/jgth-2019-0107.
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AbstractLet w be a group-word. For a group G, let {G_{w}} denote the set of all w-values in G and {w(G)} the verbal subgroup of G corresponding to w. The word w is semiconcise if the subgroup {[w(G),G]} is finite whenever {G_{w}} is finite. The group G is an {\mathrm{FC}(w)}-group if the set of conjugates {x^{G_{w}}} is finite for all {x\in G}. We prove that if w is a semiconcise word and G is an {\mathrm{FC}(w)}-group, then the subgroup {[w(G),G]} is {\mathrm{FC}}-embedded in G, that is, the intersection {C_{G}(x)\cap[w(G),G]} has finite index in {[w(G),G]} for all {x\in G}. A similar result holds for {\mathrm{BFC}(w)}-groups, that are groups in which the sets {x^{G_{w}}} are boundedly finite. We also show that this is no longer true if w is not semiconcise.
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Yormirzoev, Mirzobobo, Ramona Teuber i Tongzhe Li. "Food quality vs food patriotism". British Food Journal 121, nr 2 (4.02.2019): 371–85. http://dx.doi.org/10.1108/bfj-02-2018-0088.
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Purpose The purpose of this paper is to investigate the role of perceived food quality and consumer ethnocentrism and potential trade-offs between these two concepts in Russian consumers’ food purchase decisions after the implementation of the Russian import ban. Design/methodology/approach Survey data were collected via in-person interviews in the City of Perm, which is one of the largest and most industrial cities in Russia. A double-bounded dichotomous-choice contingent valuation model is utilized to estimate willingness to pay (WTP) and to analyze factors that affect consumers’ choice. Findings The results suggest that most respondents do not consider domestically produced cheese as a risky product in terms of food safety but simply of lower quality than imported cheese. However, the average respondent’s WTP discount for domestic cheese compared to imported cheese is 8 percent, which is relatively small. This corresponds to participants’ opinion that buying domestic cheese is the right thing to do since it supports Russian farmers and producers. The results indicate further that with increasing education and income levels, individuals are less likely to prefer domestically produced cheese for either economic or quality reasons. This effect is stronger for the quality preference. Research limitations/implications The results indicate that if the Russian government aims at expanding the domestic food market further, more attention needs to be paid to ensuring the quality of domestic food products in order to increase consumer acceptance and WTP. Originality/value This is the first study providing empirical evidence on Russian consumers’ attitudes and perceptions of domestically vs imported food products after the implementation of the Russian import ban, which can be considered as an external policy shock.
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DELIZIA, COSTANTINO, PAVEL SHUMYATSKY i ANTONIO TORTORA. "ON GROUPS WITH FINITE CONJUGACY CLASSES IN A VERBAL SUBGROUP". Bulletin of the Australian Mathematical Society 96, nr 3 (8.06.2017): 429–37. http://dx.doi.org/10.1017/s0004972717000442.
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Let $w$ be a group-word. For a group $G$, let $G_{w}$ denote the set of all $w$-values in $G$ and let $w(G)$ denote the verbal subgroup of $G$ corresponding to $w$. The group $G$ is an $FC(w)$-group if the set of conjugates $x^{G_{w}}$ is finite for all $x\in G$. It is known that if $w$ is a concise word, then $G$ is an $FC(w)$-group if and only if $w(G)$ is $FC$-embedded in $G$, that is, the conjugacy class $x^{w(G)}$ is finite for all $x\in G$. There are examples showing that this is no longer true if $w$ is not concise. In the present paper, for an arbitrary word $w$, we show that if $G$ is an $FC(w)$-group, then the commutator subgroup $w(G)^{\prime }$ is $FC$-embedded in $G$. We also establish the analogous result for $BFC(w)$-groups, that is, groups in which the sets $x^{G_{w}}$ are boundedly finite.
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Li, Chenguang, Junfei Bai, Zhifeng Gao i Jiangyuan Fu. "Willingness to pay for “taste of Europe”: geographical origin labeling controversy in China". British Food Journal 119, nr 8 (7.08.2017): 1897–914. http://dx.doi.org/10.1108/bfj-11-2016-0580.
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Purpose Continuing economic growth in emerging markets offers large market opportunities to producers and marketers worldwide; however, market failures due to asymmetric information are often seen when high-quality products enter these “new markets” where recognition rates among consumers are low. The use of “geographical origin” labels as quality signals to overcome asymmetric information problem plays an important role. The purpose of this paper is to compare consumers’ perception and willingness to pay (WTP) for different levels of geographic origin labels to provide insights to the strategic use of origin labels in emerging markets. Design/methodology/approach A consumer survey on geographic labeling for imported dairy products was carried out in Beijing, China in May 2015. Under the “products of European Union (EU)” range, the authors used “product of Ireland” as a case study for the country-specific origin label. Information on consumer demographic, dairy consumption, safety perceptions, knowledge on Ireland and Irish products, as well as WTP for different geographic labeling and product attributes were collected from 307 face-to-face interviews. WTP was elicited using double-bounded contingent valuation method, and estimated with maximum log-likelihood function. Findings The authors found that consumers are willing to pay premium prices for both of these geographical origin indicators, but the EU label had slightly higher WTP results. However, the controversial situation is that although the EU label has a better chance than the country-specific label in signaling premium quality to Chinese consumers, EU labeling at its best signals an average quality across the EU counties. For premium products with above average quality, using generic EU labeling has a potential drawback to the establishment of product differentiation. Originality/value This study is the first to evaluate Chinese consumers’ WTP for EU generic origin label for dairy products in comparison to country-specific origin label. Findings of the study have immediate policy and marketing implications in emerging markets.
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Vasilyeva, Maria A., Yuri A. Gusev, Valery G. Shtyrlin i Yury N. Osin. "The Percolation Phenomenon and Fractal Dimension of Natural Silicates". Defect and Diffusion Forum 365 (lipiec 2015): 128–35. http://dx.doi.org/10.4028/www.scientific.net/ddf.365.128.
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Many physical effects, such asdcconductivity and percolation, depend on the morphology of the silicate structure and its relationship to adsorbed water. These effects play an important role in numerous technological applications, in geology, oil-extracting industry, and other practical fields. In this study, all the samples: natural montmorillonite, kaolinite, and сlinoptilolite with different exchangeable cations in their structures, – were stored in ambient air humidity. The investigation was carried by using two separate techniques, namely Dielectric Spectroscopy and a fractal analysis of electron micrographs. The aims of this work were to analyze the complex relaxation behavior of the relaxation process in temperature range –70°C ÷ +70°C and to determine the fractal dimensions of silicates from the dielectric response at percolation. Dielectric measurements in the frequency range of 1 Hz ÷ 1 MHz were performed using a BDS 80 Dielectric Spectrometer based on an Alpha Impedance Analyzer (Novocontrol). The micrographs were analyzed using a special Matlab based program. The analysis of aspects of the dielectric relaxation spectra related to percolation was used for the determination of the numerical characteristics of geometric heterogeneity of natural silicates. The percolation temperatures of the studied samples were determined. The percolation phenomenon in the silicates is related to the transfer of the electric excitation within the developed network of open pores due to the migration of protons and ions along the surface of connected pores on the outer surfaces of the granules. The analysis of these processes allows one to extract the fractal dimensions associated with the migration of charge carriers within the porous medium. Fractal dimensions of the silicates calculated in two ways: from dielectric spectroscopy study and from fractal analysis of the micrographs, – are in good agreement with each other. It was demonstrated that conventional method of the spatial fractal dimension determination using fractal analysis of electron micrographs leads to overestimation in the case of spatial fractal bounded by a surface fractal. The dielectric spectroscopy method is free from such overestimation.
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SCHNEIDER, T., i H. KELLER. "EXTREME TYPE II SUPERCONDUCTORS: UNIVERSAL PROPERTIES AND TRENDS". International Journal of Modern Physics B 08, nr 05 (28.02.1994): 487–528. http://dx.doi.org/10.1142/s021797929400021x.
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We review and analyze experiment results of the specific heat, the muon–spin rotation (μSR) relaxation rate and the fluctuation contributions to the magnetization and dc conductivity of extreme type II superconductors from the point of view of critical phenomena. Our estimates of critical exponents and amplitudes, the measured scaling behavior, the consistencies with the universal relations between the critical amplitudes and the decrease of the transition temperature (T c ) with decreasing thickness, which corresponds to a dimensional crossover from 3d and 2d xy critical behavior, provide considerable evidence for a three-dimensional xy critical point. The estimated volume of the critical correlation length amplitudes turns out to be comparable to that in super-fluid Helium and is several orders of magnitude smaller than in BCS superconductors. Moreover, motivated by the Uemura plot, which relates the measured T c to the zero temperature μSR relaxation rate, and by the hyperuniversal relation between T c and critical amplitudes of the London penetration depth and phase correlation length, we propose a simple "universal" scaling ansatz, where the plot of the rescaled transition temperature versus rescaled μSR relaxation rate should fall on a single parabola. Our analysis of the μSR data reveals excellent agreement with this scaling ansatz for a large class of cuprate and Chevrel-phase superconductors. The resulting dependence of T c on the zero-temperature "condensate density" is then used to explore universal trends in the pressure (α) and isotope (β) coefficients. In good agreement with experiment we find that α and β fall into common T c -α and T c -β regions, respectively, forming two branches, one for systems with positive and the other for compounds with negative pressure or isotope coefficient. The two branches merge at the maximum T c where the coefficients vanish and the magnitude of the coefficients increases with decreasing T c . The "universal" scaling ansatz also implies that the critical amplitudes of the penetration depth and phase correlation length are related to the zero temperature condensate density. This quantity is also related to the hole concentration. Finally we discuss the temperature dependence of the penetration depth. μSR measurements indicate that for various cuprates the temperature dependence for 0 < T < T c appears to be bounded by the two-fluid model and the dilute charged Bose gas behaviors, respectively. Consistent with the dependence of T c on the zero temperature condensate density, compounds with high T c 's turn out to be closer to two-fluid behavior, while compounds with decreasing T c and in turn with lower condensate density clearly reveal the crossover to the dilute gas limit. These trends combined with T → 0 point uniquely to Bose condensation of interacting and weakly charged pairs as the mechanism that drives the transition.
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"Polynomial-Time Algorithm for Learning Optimal BFS-Consistent Dynamic Bayesian Networks". Entropy 20, nr 4 (12.04.2018): 274. http://dx.doi.org/10.3390/e20040274.
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Dynamic Bayesian networks (DBN) are powerful probabilistic representations that model stochastic processes. They consist of a prior network, representing the distribution over the initial variables, and a set of transition networks, representing the transition distribution between variables over time. It was shown that learning complex transition networks, considering both intra- and inter-slice connections, is NP-hard. Therefore, the community has searched for the largest subclass of DBNs for which there is an efficient learning algorithm. We introduce a new polynomial-time algorithm for learning optimal DBNs consistent with a breadth-first search (BFS) order, named bcDBN. The proposed algorithm considers the set of networks such that each transition network has a bounded in-degree, allowing for p edges from past time slices (inter-slice connections) and k edges from the current time slice (intra-slice connections) consistent with the BFS order induced by the optimal tree-augmented network (tDBN). This approach increases exponentially, in the number of variables, the search space of the state-of-the-art tDBN algorithm. Concerning worst-case time complexity, given a Markov lag m, a set of n random variables ranging over r values, and a set of observations of N individuals over T time steps, the bcDBN algorithm is linear in N, T and m; polynomial in n and r; and exponential in p and k. We assess the bcDBN algorithm on simulated data against tDBN, revealing that it performs well throughout different experiments.
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"Implicit Landmark Path Indexing for Bounded Label Constrained Reachable Paths". International Journal of Recent Technology and Engineering 8, nr 4 (30.11.2019): 10660–69. http://dx.doi.org/10.35940/ijrte.d4273.118419.
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In today’s Big Data era, a graph is an essential tool that models the semi-structured or unstructured data. Graph reachability with vertex or edge constraints is one of the basic queries to extract useful information from the graph data. From the graph reachability with constraints, we obtained the information about the existence of a path between the given two vertices satisfying the vertex or edge constraints. The problem of Label Constraint Reachability (LCR) found the existence of a path between the two given vertices such that the edge-labels along the path are the subset of the given edge-label constraint. We extended the LCR queries by considering weighted directed graphs and proposed a novel technique of finding paths for LCR queries bounded by path weight. We termed these paths as bounded label constrained reachable paths (BLCRP). We extended the landmark path indexing technique [1] by incorporating the implicit paths which satisfy the user constraints but need not satisfy the minimality of edge label sets. We solved the BLCRP by using the extended landmark path indexing and BFS based query processing. We addressed the following challenges through our proposed technique of implicit landmark path indexing in the problem of BLCRP that included (1) the need to handle exponential number of edge label combinations with an additional total path weight constraint, and (2) the need to discover a technique that finds exact reachable paths between the given vertices. This problem could be applied to real network scenarios like road networks, social networks, and proteinprotein interaction networks. Our experiments and statistical analysis revealed the accuracy and efficiency of the proposed approach tested on synthetic and real datasets.
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Ivanov, Igor P., i Francisco Vazão. "Yet another lesson on the stability conditions in multi-Higgs potentials". Journal of High Energy Physics 2020, nr 11 (listopad 2020). http://dx.doi.org/10.1007/jhep11(2020)104.
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Abstract We discuss a rather common but often unnoticed pitfall which arises when deriving the bounded-from-below (BFB) conditions in multi-Higgs models with softly broken global symmetries. Namely, necessary and sufficient BFB conditions derived for the case with an exact symmetry can be ruined by introducing soft symmetry breaking terms. Using S4 and A4-symmetric three-Higgs-doublet models as an example, we argue that all published necessary and sufficient BFB conditions, even those which are correct for the exactly symmetric case, are no longer sufficient if soft symmetry breaking is added. Using the geometric formalism, we derive the exact necessary and sufficient BFB conditions for the 3HDM with the symmetry group S4, either exact or softly broken, and review the situation for the A4-symmetric case.
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Carrolo, Sergio, Jorge C. Romão i João P. Silva. "Conditions for global minimum in the $$A_4$$ symmetric 3HDM". European Physical Journal C 82, nr 8 (26.08.2022). http://dx.doi.org/10.1140/epjc/s10052-022-10712-3.
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AbstractThere has been a great interest in three Higgs doublet models (3HDM) symmetric under an exact $$A_4$$ A 4 symmetry. We provide the complete analytic necessary and sufficient conditions for a point to be the global minimum along the neutral directions in such models, discussing many of the subtleties involved. We also present a number of numerical examples, to highlight those issues. We then turn to the directions which break electric charge, presenting a safe analytical sufficient condition for bounded from below (BFB) potentials. Based on extensive numerical simulations, we discuss one conjecture on BFB along charge breaking directions.
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Frank, Mariana, Chayan Majumdar, Poulose Poulose, Supriya Senapati i Urjit A. Yajnik. "Vacuum structure of Alternative Left-Right Model". Journal of High Energy Physics 2022, nr 3 (marzec 2022). http://dx.doi.org/10.1007/jhep03(2022)065.
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Abstract We investigate an Alternative Left-Right Model (ALRM) with SU(2)L as well as SU(2)R gauge groups, but unlike the traditional left-right symmetric models (LRSM) is not symmetric under the exchange of the fermion content. Interestingly, it can be embedded in E6, while its low energy Higgs structure resembles the LRSM, involving Higgs doublets χL,R and one Higgs bidoublet Φ. We analyze the scalar potential and the vacuum structure of the theory analytically to ensure the stability of scalar potential via bounded from below (BFB) and copositivity criteria, accompanied by a numerical study. We establish the necessary criteria for electric charge-preserving vacua, yielding constraints on various coupling parameters of the theory. Finally we obtain constraints on the parameters of the model from collider data on the masses of the Higgs scalars.
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Wang, Jianfeng, Zhiyong Zhou i Jun Yu. "Error bounds of block sparse signal recovery based on q-ratio block constrained minimal singular values". EURASIP Journal on Advances in Signal Processing 2019, nr 1 (27.11.2019). http://dx.doi.org/10.1186/s13634-019-0653-1.
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AbstractIn this paper, we introduce the q-ratio block constrained minimal singular values (BCMSV) as a new measure of measurement matrix in compressive sensing of block sparse/compressive signals and present an algorithm for computing this new measure. Both the mixed ℓ2/ℓq and the mixed ℓ2/ℓ1 norms of the reconstruction errors for stable and robust recovery using block basis pursuit (BBP), the block Dantzig selector (BDS), and the group lasso in terms of the q-ratio BCMSV are investigated. We establish a sufficient condition based on the q-ratio block sparsity for the exact recovery from the noise-free BBP and developed a convex-concave procedure to solve the corresponding non-convex problem in the condition. Furthermore, we prove that for sub-Gaussian random matrices, the q-ratio BCMSV is bounded away from zero with high probability when the number of measurements is reasonably large. Numerical experiments are implemented to illustrate the theoretical results. In addition, we demonstrate that the q-ratio BCMSV-based error bounds are tighter than the block-restricted isotropic constant-based bounds.
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Medková, Dagmar. "One Navier’s problem for the Brinkman system". ANNALI DELL'UNIVERSITA' DI FERRARA, 25.02.2023. http://dx.doi.org/10.1007/s11565-023-00458-5.
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AbstractIn this paper we study the Brinkman system and the Darcy-Forchheimer-Brinkman system with the boundary condition of the Navier’s type $$ {\textbf{u}}_{{\mathbf {\mathcal {T}}}} = {\textbf{g}}_{{\mathbf {\mathcal {T}}}} $$ u T = g T , $$\rho =h$$ ρ = h on $$\partial \Omega $$ ∂ Ω for a bounded planar domain $$\Omega $$ Ω with connected boundary. Solutions are looked for in the Sobolev spaces $$W^{s+1,q}(\Omega ,{\mathbb R}^2)\times W^{s,q}(\Omega )$$ W s + 1 , q ( Ω , R 2 ) × W s , q ( Ω ) and in the Besov spaces $$B_{s+1}^{p,r}(\Omega ,{\mathbb R}^2)\times B_s^{q,r}(\Omega )$$ B s + 1 p , r ( Ω , R 2 ) × B s q , r ( Ω ) . Classical solutions are from the spaces $${\mathcal C}^{k+1,\gamma }(\overline{\Omega },{\mathbb R}^2) \times {\mathcal C}^{k,\gamma }(\overline{\Omega })$$ C k + 1 , γ ( Ω ¯ , R 2 ) × C k , γ ( Ω ¯ ) . For the Brinkman system we show the unique solvability of the problem. Then we study the Navier problem for the Darcy-Forchheimer-Brinkman system and small boundary conditions.
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Yu, Pei, Weihua Zhang, Barbara Dietz i Liang Huang. "Quantum signatures of chaos in relativistic quantumbilliards with shapes of circle- and ellipse-sectors". Journal of Physics A: Mathematical and Theoretical, 19.04.2022. http://dx.doi.org/10.1088/1751-8121/ac6840.
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Abstract According to the Berry-Tabor conjecture, the spectral properties of typical nonrelativistic quantum systems with an integrable classical counterpart agree with those of Poissonian random numbers. We investigate to what extend it applies to relativistic neutrino billiards (NBs) consisting of a spin-1/2 particle confined to a bounded planar domain by imposing suitable boundary conditions (BCs). In distinction to nonrelativistic quantum billiards (QBs), NBs do not have a well-defined classical counterpart. However, the peaks in the length spectra, that is, the modulus of the Fourier transform of the spectral density from wave number to length, of NBs are just like for QBs at the lengths of periodic orbits of the classical billiard (CB). This implies that there must be a connection between NBs and the dynamic of the CB. We demonstrate that NBs with shapes of circle- and ellipse-sectors with an integrable classical dynamic, obtained by cutting the circle and ellipse NB along symmetry lines, have no common eigenstates with the latter and that, indeed, their spectral properties can be similar to those of classically chaotic QBs. These features orginate from the intermingling of symmetries of the spinor components and the discontinuity in the BCs leading to contradictory conditional equations at corners connecting curved and straight boundary parts. To corroborate the necessity of the curved boundary part in order to generate GOE- like behavior, we furthermore consider the right-angled triangle NB constructed by halving the equilateral-triangle NB along a symmetry axis. For an understanding of these findings in terms of purely classical quantities we use the semiclassical approach recently developed for massive NBs, and Poincaré-Husimi distributions of the eigenstates in classical phase space. The results indicate, that in the ultrarelativistic limit these NBs do not show the behavior expected for classically chaotic QBs.
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Lai, Jonathan K., Elia Merzari i Yassin A. Hassan. "Large Eddy Simulation of the Flow Behavior in a Simplified Helical Coil Steam Generator". Journal of Fluids Engineering 141, nr 2 (29.06.2018). http://dx.doi.org/10.1115/1.4040464.
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Large eddy simulation (LES) is conducted for the flow over the shell side of a helical coil steam generator (HCSG) heat exchanger. Simulations are conducted on a simplified experimental test section that represents a one-column region of the helical coils using half-rods. Although the rods are wall-bounded, the flow still exhibits the turbulent characteristics and fluctuations from vortex shedding that one would expect from crossflow around a cylinder. The spectral element, computational fluid dynamics (CFD) code Nek5000, is used to capture the physics, and the results are compared with particle image velocimetry (PIV) measurements. In order to ensure that the turbulence is resolved, analysis is conducted by using the Taylor length scales and normalized wall distance. Sensitivity to the inlet boundary conditions (BCs) and the spatial discretization for different polynomial order solutions are also studied, finding only minor differences between each case. Pressure drop and velocity statistics show reasonable agreement with PIV. Proper orthogonal decomposition (POD) analysis reveals that the primary modes are similar between experiment and simulation, although the LES predicts higher turbulent kinetic energy than does PIV. Overall, the study establishes the resolution and resources required in order to conduct a high-fidelity simulation over 12 helical rods.
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Mani, Karthik V., Angelo Cervone i Jean-Pierre Hickey. "Turbulence Modeling of Cavitating Flows in Liquid Rocket Turbopumps". Journal of Fluids Engineering 139, nr 1 (14.09.2016). http://dx.doi.org/10.1115/1.4034096.
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An accurate prediction of the performance characteristics of cavitating cryogenic turbopump inducers is essential for an increased reliance on numerical simulations in the early turbopump design stages of liquid rocket engines (LRE). This work focuses on the sensitivities related to the choice of turbulence models on the cavitation prediction in flow setups relevant to cryogenic turbopump inducers. To isolate the influence of the turbulence closure models for Reynolds-Averaged Navier–Stokes (RANS) equations, four canonical problems are abstracted and studied individually to separately consider cavitation occurring in flows with a bluff body pressure drop, adverse pressure gradient, blade passage contraction, and rotation. The choice of turbulence model plays a significant role in the prediction of the phase distribution in the flow. It was found that the sensitivity to the closure model depends on the choice of cavitation model itself; the barotropic equation of state (BES) cavitation models are far more sensitive to the turbulence closure than the transport-based models. The sensitivity of the turbulence model is also strongly dependent on the type of flow. For bounded cavitation flows (blade passage), stark variations in the cavitation topology are observed based on the selection of the turbulence model. For unbounded problems, the spread in the results due to the choice of turbulence models is similar to noncavitating, single-phase flow cases.
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Capoccia Giovannini, S., G. Camerini, L. Rossi, A. Rubartelli, F. Carlini, G. Longo, B. Drago, L. Epis i C. Stabilini. "V-041 ROBOTIC MONOLATERAL TAR FOR LATERAL INCISIONAL HERNIA IN PREVIOUS COLOSTOMY SITE". British Journal of Surgery 110, Supplement_2 (maj 2023). http://dx.doi.org/10.1093/bjs/znad080.274.
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Abstract Background Novitsky described the Transversus Abdominis Muscle release (TAR) extending the retromuscolar plane (RMP) improving the midline restoration (MR) with high morbidity. The robotic approach seems to have the same effectiveness reducing wound complications. Video's comment A 58-year-old male submitted to Hartmann procedure for acute diverticulitis, developed an incisional hernia (IH) (3cm width) on colostomy site, L2-W1 according to IH-EHS classification and an umbilical IH of 2cm width (EHS classification: M3-W1), after Hartmann reversal. We planned the abdominal wall repair with R-TAR by drawing on the skin the dimension of the mesh with an overlap of 7cm from the defect, helping us to orient the dissection using transfascial needles. After the pneumoperitoneum created and the lateral-right sided-docking of Da Vinci Xi, we incised the lateral edge of right posterior rectus sheet (PRS) and dissected the RMP. The incision of the medial edge of the PRS and the identification of the linea alba allows the crossing-over to the contralateral RMP. We reduced the umbilical IH and dissected completely the left RMP to the flank defect and the Neurovascular Boundles. We started the division of TA fibers and we dissected the preperitoneal plane beyond the IH sac and to the arcuate line. We closed the defects with a 0-vloc and the peritoneum with a 3/0-vloc both barbed. We implanted a 15×30 Progrip selfigripping mesh and we closed the peritoneal-flap with a 2/0-vloc barbed suture. The patient was discharged in 2 days and any complication were recorded after 30 days.
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M., El–Harbawi, Mustapha S., Idris A., Jameel A.T. i T. G. Chuah. "Linear Stability of Thin Liquid Film on Solid Surface Under Effect of Apolar and Polar Forces". Jurnal Teknologi, 20.01.2012. http://dx.doi.org/10.11113/jt.v39.469.
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Tenaga lebihan bebas Gibb per unit luas (ΔG) bagi suatu saput nipis yang tulen, tanpa cas pada satu sokongan hanya diterbitkan daripada interaksi antara molekul apolar (Lifshitz - van der Waals) dan polar (acid-bes). Interaksi polar dapat dinyatakan secara berasingan sebagai tekanan penghidratan, interaksi hidrofobik dan intekrasi asid-bes. Jumlah tenaga lebihan bebas Gibb per unit luas (ΔG) bagi satu saput nipis pada satu lapisan bergantung kepada ketebalan saput, dan angkali penyebaran apolar dan polar untuk sistem tersebut. Saput dimodelkan sebagai cecair Newtonian 2-dimensi dengan ketumpatan tetap, ρ, dan kelikatan, μ, mengalir di atas satu permukaan mengufuk. Ketebalan purata saput cecair, h0, dianggapkan cukup nipis supaya kesan graviti boleh diabaikan dan melambung atas oleh gas pasif dan menyambung secara lateral hingga infiniti (Model dua-dimensi). Daya badan yang disebut dalam persamaan Navier-Stokes adalah diubahsuaikan oleh kandungan interaksi antara molekul lebihan (daya apolar dan polar) antara saput bendalir dan permukaan pepejal bergantung kepada daya-daya apolar dan polar. Persamaan Navier-Stokes telah diubahsuai dengan keadaan sempadan berkaitan diselesaikan bawah kaedah pendekatan gelombong panjang untuk memperolehi persamaan perkembangan tak-linear bagi saput antara permukaan. Daya apolar dan polar telah didapati memainkan peranan pencirian atas saput nipis dan kesan utama pada sifat tenaga lebihan bebas, kadar penubuhan, kadar penubuhan maksimum, gelombong neutral, nombor gelombang yang dominan, jarak gelombong dominan dan masa memecah. Oleh demikian, teori linear adalah kurang sesuai untuk menyatakan kestabilan pencirian selaput. Kata kunci: Daya apolar, daya polar, kestabilan linear, kadar pertumbuhan, masa memecah The total excess free energy per unit area (ΔG) of a pure, uncharged thin film on a support is solely derived from the apolar (Lifshitz - van der Waals) and polar (acid-base) intermolecular interactions. Polar interactions are variously described as the hydration pressure, hydrophobic interaction and acid base interaction. The total free excess energy (per unit area) of a thin film on a substrate depends on the film thickness, and the apolar and polar spreading coefficients for the system. The film is modelled as a two-dimensional Newtonian liquid of constant density, ρ and viscosity, μ, flowing on a horizontal plane. The liquid film of mean thickness, h0, is assumed to be thin enough to neglect the gravity effect and bounded above by a passive gas and laterally extends to infinity (two-dimensional model). The body force term in the Navier-Stokes equation is modified by the inclusion of excess intermolecular interactions (apolar and polar forces) between fluid film and the solid surface owing to apolar and polar forces. The modified Navier-Stokes equation with associated boundary conditions is solved under long wave approximation method to obtain a nonlinear equation of evolution of the film interface. The apolar and polar forces were found to play the dominant role in characteristic of thin films and the main effect on the behavior of the excess free energy, growth rate, maximum growth rate, neutral wave, dominant wavenumber, dominant wavelength and rupture time. Hence, the linear theory is inadequate to describe the stability characteristics of films. Key words: Apolar force, polar force, linear stability, growth rate, rupture time