Synchronous Tree Research Articles

Relating structure and power: Comonadic semantics for computational resources

AbstractCombinatorial games are widely used in finite model theory, constraint satisfaction, modal logic and concurrency theory to characterize logical equivalences between structures. In particular, Ehrenfeucht–Fraïssé games, pebble games and bisimulation games play a central role. We show how each of these types of games can be described in terms of an indexed family of comonads on the category of relational structures and homomorphisms. The index $k$ is a resource parameter that bounds the degree of access to the underlying structure. The coKleisli categories for these comonads can be used to give syntax-free characterizations of a wide range of important logical equivalences. Moreover, the coalgebras for these indexed comonads can be used to characterize key combinatorial parameters: tree depth for the Ehrenfeucht–Fraïssé comonad, tree width for the pebbling comonad and synchronization tree depth for the modal unfolding comonad. These results pave the way for systematic connections between two major branches of the field of logic in computer science, which hitherto have been almost disjoint: categorical semantics and finite and algorithmic model theory.

Reconfigurable Superconducting FFT Processor Using Bit-Slice Block Share Processing Unit

We have proposed a reconfigurable high speed and very economical Rapid Single Flux Quantum (RSFQ) superconducting logic design based on the Fast Fourier Transform (FFT) Processor. We have designed a 256 – point FFT processor with the help of a bit-slicing block sharing unit. RSFQ is one of the superconducting device logics comprises of Josephson Junction. The computation complexity of this superconducting FFT is less when the number of points increased. We have proposed three different designs depending on the split radix FFT, the bit-serial radix 2 FFT, and the mixed radix FFT algorithms. The proposed design will slice the 256 – point FFT into eight 32 – point FFT each and each 32 – point FFT is divided into eight 4 – point FFT each for the reduction in hardware cost. For complex multiplication, the computation complexity of our design will be less than N/2 Log2 N for the radix 2 algorithm based on the Block share processing Unit (BSPU) and further, it is reduced for split radix & mixed radix algorithms based on BSPU based RSFQ logic. Due to this, the speed of the processor is improvised compared to general FFT algorithm based semiconductor technology. we have computed and calculated the latency at 10 GHz for our designs. The main aim of this proposed design is to reduce the complex computation time and better performance of the processor with less hardware cost. This proposed design can furthermore continue to several N2 – point by using synchronous clock tree.

A Minimum-Skew Clock Tree Synthesis Algorithm for Single Flux Quantum Logic Circuits

This article presents a synchronous minimum-skew clock tree synthesis algorithm for single flux quantum circuits considering splitter delays and placement blockages. The proposed methodology improves the state-of-the-art by accounting for splitter delays and creating a fully balanced clock tree structure in which the number of clock splitters from the clock source to all the sink nodes is identical. Additionally, a mixed integer linear programming based algorithm is presented that removes the overlaps among the clock splitters and placed cells (i.e., placement blockages) and minimizes the clock skew, simultaneously. Using the proposed method, the average clock skew for 17 benchmark circuits is 4.6 ps, improving the state-of-the-art algorithm by $\text{70}{\%}$ . Finally, a clock tree synthesis algorithm for imbalanced topologies is presented that reduces the clock skew and the number of clock splitters in the clock network by $\text{56}{\%}$ and $\text{37}{\%}$ , respectively, compared with a fully balanced clock tree solution.

Effects of extreme drought and wet events for tree mortality: Insights from tree‐ring width and carbon isotope ratio in a Siberian larch forest

AbstractRecent studies suggest that forest vulnerability to tree mortality has increased as a result of extreme climate events such as severe drought and heavy rain. However, little is known about the mortality processes, particularly when they are induced by heavy rain. A dendroecological analysis was conducted on living and dead trees in a Siberian larch forest using the chronologies of 30 years of radial growth and carbon isotope (Δ13C) discrimination. The analysis demonstrates the relationship between heavy rain and larch tree mortality. Radial growth and Δ13C patterns in dead trees at a wet subsite diverged from those of living trees only during the heavy rain period in 2005–2007. On the other hand, the radial growth and Δ13C patterns in dead trees at the dry subsite diverged from those of living trees after severe drought events in 1998 and in 2002–2003. At the wet subsite, the heavy rain was intense enough to push the larch trees past their mortality threshold, whereas previous drought conditions also contributed to tree mortality at the dry subsite. Our results demonstrated that the process of larch tree mortality differs with site‐specific topographical soil moisture conditions, even when synchronous tree death occurs in a specific year of climatic extremes.

Evaluation of Different Pooling Methods to Establish a Multi-Century δ18O Chronology for Paleoclimate Reconstruction

To develop multi-century stable isotope chronologies from tree rings, pooling techniques are applied to reduce laboratory costs and time. However, pooling of wood samples from different trees may have adverse effects on the signal amplitude in the final isotope chronology. We tested different pooling approaches to identify the method that is most cost-efficient, without compromising the ability of the final chronology to reflect long-term climate variability as well as climatic extreme years. As test material, we used δ18O data from juniper trees (Juniperus polycarpus) from Northern Iran. We compared inter-tree and shifted 5-year blocks serial pooling of stable isotope series from 5 individual trees and addition of one single series to a shifted serial pooled chronology. The inter-tree pooled chronology showed the strongest climate sensitivity and most synchronous δ18O variations with the individual tree ring analyses, while the shifted block chronologies showed a marked decline in high-frequency signals and no correlations with climate variables of the growth year. Combinations of block-pooled and single isotope series compensated the high-frequency decline but added tree-individual climatic signals. Therefore, we recommend pooling calendar synchronous tree rings from individual trees as a viable alternative to individual-tree isotope measurements for robust paleoclimate reconstructions.

Dendrochronological reconstruction of fire history in coniferous forests in the Monarch Butterfly Biosphere Reserve, Mexico

BackgroundSome have proposed that fire return intervals lengthen with elevation in montane tropical coniferous forests, such as those found in central Mexico. This would generate patterns of synchronous tree establishment in higher elevation forests dominated by Abies sp. Mill., and patterns of continuous tree establishment in lower elevation forests dominated by Pinus sp. L. However, it is common to find codominant stands of both genera at intermediate elevations. The Monarch Butterfly Biosphere Reserve (MBBR) is located in this region, and is covered by Abies religiosa (Kunth) Schltdl. & Cham-dominant forest, A. religiosa–Pinus pseudostrobus Lindley-codominant forest, and P. pseudostrobus-dominant forest. Despite the ecological importance of the MBBR’s coniferous forests, little is known about their fire return intervals, including their relationship with climate, and their effects on tree establishment patterns according to the elevational range proposed above. In this study, using dendrochronological techniques, we reconstructed the historical fire return intervals for each forest type, evaluated their relationship with droughts and with the El Niño Southern Oscillation (ENSO), and assessed the effect of fire return intervals on tree establishment patterns. A total of 110 cross-sections were obtained, from 23 sites across the MBBR.ResultsThe fire chronology covered the period between 1925 and 2015. Fire return intervals averaged two years in stands dominated by A. religiosa, by P. pseudostrobus, and codominated by both species, regardless of elevation. No fire-free periods were detected, even after the establishment of the reserve in 2000. Fire frequency was not associated with periods of drought and ENSO. There was no relationship between fire return intervals and patterns of tree establishment, which was continuous in all three forest types.ConclusionsOur results suggest that coniferous forests of the MBBR have historically experienced frequent fires that are unrelated to climate and tree establishment. This may be evidence that natural fire regimes in these coniferous forests have been drastically altered by human activities. Although these frequent low-severity fires could adversely affect tree regeneration, and eventually decrease the integrity of the overwintering habitat of the Monarch Butterfly, the continuous tree regeneration observed suggests that these effects have not yet taken place.

Bisimulation and Hennessy-Milner Logic for Generalized Synchronization Trees

In this work, we develop a generalization of Hennessy-Milner Logic (HML) for Generalized Synchronization Trees (GSTs) that we call Generalized Hennessy Milner Logic (GHML). Importantly, this logic suggests a strong relationship between (weak) bisimulation for GSTs and ordinary bisimulation for Synchronization Trees (STs). We demonstrate that this relationship can be used to define the GST analog for image-finiteness of STs. Furthermore, we demonstrate that certain maximal Hennessy-Milner classes of STs have counterparts in maximal Hennessy-Milner classes of GSTs with respect to GST weak bisimulation. We also exhibit some interesting characteristics of these maximal Hennessy-Milner classes of GSTs.

Towards more precise rewriting approximations

To check a system, some verification techniques consider a set of terms I that represents the initial configurations of the system, and a rewrite system R that represents the system behavior. To check that no undesirable configuration is reached, they compute an over-approximation of the set of descendants (successors) issued from I by R, expressed by a tree language. Some techniques have been presented using regular tree languages, and more recently using non-regular languages to get better approximations: using context-free tree languages [1] on the one hand, using synchronized tree languages [2] on the other hand. In this paper, we merge these two approaches to get even better approximations: we compute an over-approximation of the descendants, using synchronized-context-free tree languages expressed by logic programs. We give several examples for which our procedure computes the descendants in an exact way, unlike former techniques.

Synchronous cholangiocarcinoma and gallbladder cancer: A rare presentation

Introduction: Synchronous biliary tree and gallbladder cancers are rarely encountered and reported in the literature. In this article, we report an extremely rare presentation of a patient with distal common hepatic duct (CHD), proximal common bile duct (CBD) and gallbladder cancer associated with anomalous pancreaticobiliary duct junction (APBDJ) as primary tumors. Case Report: A 40-year-old male referred to us with RUQ pain, fever, jaundice and pruritis since two weeks. PET-CT showed hypermetabolic polypoid mass in the fundus of gallbladder and a periportal node. ERCP was done but guide wire could not be passed beyond mid CBD. The findings were neoplastic mass in fundus of the gallbladder with pericholedochal lymphadenopathy. There was another neoplastic mass in the CBD. An extended cholecystectomy with extrahepatic CBD excision with a pancreaticoduodenectomy with radical lymphadenectomy was performed. Intra-operative ultrasonography was done to rule out other lesions in the pancreas and liver. Histopathological examination revealed well differentiated adenocarcinoma of gallbladder and adenocarcinoma of proximal CBD and distal CHD, stagging pT2 pN0 pMx. Conclusion: Synchronous extra hepatic and gallbladder tumors are extremely rare, their etiopathogenesis has not been properly understood and defined. Biliary cancers with PBM are thought to develop multicentrally, due to the effect of pancreatic juice reflux on the mucosa of the biliary tract.

The Power of Weighted Regularity-Preserving Multi Bottom-Up Tree Transducers

The expressive power of regularity-preserving [Formula: see text]-free weighted linear multi bottom-up tree transducers is investigated. These models have very attractive theoretical and algorithmic properties, but (especially in the weighted setting) their expressive power is not well understood. Despite the regularity-preserving restriction, their power still exceeds that of composition chains of [Formula: see text]-free weighted linear extended top-down tree transducers with regular look-ahead. The latter devices are a natural super-class of weighted synchronous tree substitution grammars, which are commonly used in syntax-based statistical machine translation. In particular, the linguistically motivated discontinuous transformation of topicalization can be modeled by such multi bottom-up tree transducers, whereas the mentioned composition chains cannot implement it. On the negative side, the inverse of topicalization cannot be implemented by any such multi bottom-up tree transducer, which confirms their bottom-up nature (and non-closure under inverses). An interesting, promising, and widely applicable proof technique is used to prove these statements.

TRAINING TREE ADJOINING GRAMMARS WITH HUGE TEXT CORPUS USING SPARK MAP REDUCE

Tree adjoining grammars (TAGs) are mildly context sensitive formalisms used mainly in modelling natural languages. Usage and research on these psycho linguistic formalisms have been erratic in the past decade, due to its demanding construction and difficulty to parse. However, they represent promising future for formalism based NLP in multilingual scenarios. In this paper we demonstrate basic synchronous Tree adjoining grammar for English-Tamil language pair that can be used readily for machine translation. We have also developed a multithreaded chart parser that gives ambiguous deep structures and a par dependency structure known as TAG derivation. Furthermore we then focus on a model for training this TAG for each language using a large corpus of text through a map reduce frequency count model in spark and estimation of various probabilistic parameters for the grammar trees thereafter; these parameters can be used to perform statistical parsing on the trained grammar.

CompPhy: a web-based collaborative platform for comparing phylogenies.

BackgroundCollaborative tools are of great help in conducting projects involving distant workers. Recent web technologies have helped to build such tools for jointly editing office documents and scientific data, yet none are available for handling phylogenies. Though a large number of studies and projects in evolutionary biology and systematics involve collaborations between scientists of different institutes, current tree comparison visualization software and websites are directed toward single-user access. Moreover, tree comparison functionalities are dispersed between different software that mainly focus on high level single tree visualization but to the detriment of basic tree comparison features.ResultsThe web platform presented here, named CompPhy, intends to fill this gap by allowing collaborative work on phylogenies and by gathering simple advanced tools dedicated to tree comparison. It offers functionalities for tree edition, tree comparison, supertree inference and data management in a collaborative environment. The latter aspect is a specific feature of the platform, allowing people located in different places to work together at the same time on a common project. CompPhy thus proposes shared tree visualization, both synchronous and asynchronous tree manipulation, data exchange/storage, as well as facilities to keep track of the progress of analyses in working sessions. Specific advanced comparison tools are also available, such as consensus and supertree inference, or automated branch swaps of compared trees. As projects can be readily created and shared, CompPhy is also a tool that can be used easily to interact with students in a educational setting, either in the classroom or for assignments.ConclusionsCompPhy is the first web platform devoted to the comparison of phylogenetic trees allowing real-time distant collaboration on a phylogenetic/phylogenomic project. This application can be accessed freely with a recent browser at the following page of the ATGC bioinformatics platform: http://www.atgc-montpellier.fr/compphy/.

Novel Model of Wireless Sensor with Indoor Positioning Algorithm and Time Synchronization Protocol

This paper describes the positioning based on ZigBee network, and it provides location indoor information and node state alarm information. Wireless sensor indoor positioning system consists of 3 types nodes: the coordinator node, reference node and blind. Time synchronization protocol is an efficient synchronization technology star network structure, synchronization to the gateway node as a starting point, each cluster head node synchronization tree network structure. The paper presents novel model of wireless sensor indoor positioning algorithm and time synchronization protocol. Experiments show that the design of indoor positioning system can meet requirement function and performance of nodes positioning system.

Axiomatizing weighted synchronization trees and weighted bisimilarity

We consider regular synchronization trees weighted over a semiring and provide sound and complete axiomatizations of these trees and their weighted bisimulation equivalence classes. We prove that they can be both axiomatized by a finite number of identities relatively to the general axioms of the fixed point operation captured by the notion of iteration theories. We present infinite equational and finite quasi-equational axiomatizations.

Unsupervised Tree Induction for Tree-based Translation

In current research, most tree-based translation models are built directly from parse trees. In this study, we go in another direction and build a translation model with an unsupervised tree structure derived from a novel non-parametric Bayesian model. In the model, we utilize synchronous tree substitution grammars (STSG) to capture the bilingual mapping between language pairs. To train the model efficiently, we develop a Gibbs sampler with three novel Gibbs operators. The sampler is capable of exploring the infinite space of tree structures by performing local changes on the tree nodes. Experimental results show that the string-to-tree translation system using our Bayesian tree structures significantly outperforms the strong baseline string-to-tree system using parse trees.

A Connection Between Concurrency and Language Theory

We show that three fixed point structures equipped with (sequential) composition, a sum operation, and a fixed point operation share the same valid equations. These are the theories of (context-free) languages, (regular) tree languages, and simulation equivalence classes of (regular) synchronization trees (or processes). The results reveal a close relationship between classical language theory and process algebra.

Syntax-Based Translation With Bilingually Lexicalized Synchronous Tree Substitution Grammars

Syntax-based models can significantly improve the translation performance due to their grammatical modeling on one or both language side(s). However, the translation rules such as the non-lexical rule “ VP→(x <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> x <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> ,VP:x <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> PP:x <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> )” in string-to-tree models do not consider any lexicalized information on the source or target side. The rule is so generalized that any subtree rooted at VP can substitute for the nonterminal VP:x <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> . Because rules containing nonterminals are frequently used when generating the target-side tree structures, there is a risk that rules of this type will potentially be severely misused in decoding due to a lack of lexicalization guidance. In this article, inspired by lexicalized PCFG, which is widely used in monolingual parsing, we propose to upgrade the STSG (synchronous tree substitution grammars)-based syntax translation model with bilingually lexicalized STSG. Using the string-to-tree translation model as a case study, we present generative and discriminative models to integrate lexicalized STSG into the translation model. Both small- and large-scale experiments on Chinese-to-English translation demonstrate that the proposed lexicalized STSG can provide superior rule selection in decoding and substantially improve the translation quality.

Annotation System for the Construction of Synchronous Grammar Tree Alignment Relationships

The construction of syntactic tree structures is vital to different Natural Language Processing applications. In the meanwhile, the use of monolingual or bilingual structures directly affects the quality of Machine Translation systems. However, manually annotated syntactic tree structures are not only considered as a time consuming task but also a very expensive work, and automatic construction approaches cannot always guarantee the quality of the syntactic trees. In this paper, a system for annotating and constructing synchronous grammar tree structures in a semi-automatic way is proposed. The system is built in the Web environment with a graphical display for users to review and modify alignment relationships between nodes of the tree and strings or trees of the other language. The core part relies on the parsing of Constraint Synchronous Grammar, and consists of several modules in establishing alignments at different levels between the languages, including relationships between syntactic tree and strings of the other language, and bilingual tree alignments. Moreover, it provides import functions in obtaining monolingual skeletal bracketing syntactic tree and Translation Corresponding Tree structures for the creation of synchronous rules in order to have wider applicability.

Using synchronous tree adjoining grammar to model the typology of bound variable pronouns

This article presents a novel analysis of bound variable anaphora using Synchronous Tree Adjoining Grammar (STAG), a pairing of a Tree Adjoining Grammar (TAG) for syntax and a TAG for semantics. While a bound variable pronoun can occur at a distance from its binder, as in ‘Every girli believes that shei is intelligent’, languages vary, though in a limited way, as to how near or far from its binder a bound variable should be. As any dependency between two syntactic objects must be localized to a single predicate domain in TAG, modelling bound variable anaphora in syntax and semantics poses an interesting challenge for STAG. In our analysis, bound variable pronouns are represented as Multi-Component sets in both syntax and semantics, composing in delayed tree-local derivations. This allows us to not only account for variable binding at a distance, but it also allows us to define a single derivational parameter with which observed patterns of bound variable locality can be modelled, ruling out unobserved patterns, while capturing the range of interpretive possibilities for bound variable pronouns across languages.

Scale-dependence of aboveground carbon accumulation in secondary forests of Panama: A test of the intermediate peak hypothesis

Accumulation of aboveground carbon is one of the most important services provided by tropical secondary forests—a land-cover type that is increasing in importance globally. Carbon accumulates rapidly for the first 20years of succession, but few studies have considered forests older than 20years, and the available data do not yield a consistent pattern. Two alternative hypotheses have been proposed: (1) an asymptotic increase, with the highest carbon stocks occurring in the oldest stands, and (2) an intermediate peak, caused by roughly synchronous tree maturity (and thus high carbon stocks) after which time treefall gaps cause carbon stocks to regress. Here we revisited a well-studied tropical moist forest chronosequence in Barro Colorado Nature Monument, Central Panama, consisting of 35, 55, 85, and 115-year-old stands, as well as old-growth stands, to determine whether past evidence for the intermediate peak hypothesis was influenced by the spatial limitations of the field plots used to assess forest structure. We used airborne LiDAR (light detection and ranging) to measure carbon stocks at the scale of the original transects (0.16ha), in surrounding forest of the same age (up to 20ha), and at a landscape scale incorporating thousands of hectares not previously measured. We also compared forest structure as measured in three dimensions by LiDAR, considering vertical and horizontal variation in canopy organization, as well as the abundance of treefall gaps. Our results suggested a strong scale-dependence of aboveground carbon accumulation, supporting the intermediate peak hypothesis at the fine scale of the 0.16-ha transects, but an asymptotic model at the landscape scale incorporating thousands of hectares. Further analyses of forest structure suggest that both the limitations of small plots and intrinsic scaling of forest structure and carbon dynamics account for the scale-dependence of aboveground carbon accumulation in this secondary forest matrix.