Braided Type Research Articles

Paleoenvironment of Deposition of the Dupi Tila Formation, Lalmai Hills, Comilla, Bangladesh

Abstract The Dupi Tila Formation is composed of yellow to light brown medium to very fine moderately hard to loose sandstone, siltstone, silty clay, mudstone and shale with some conglomerates with clasts of petrified wood. The lithofacies of matrix supported conglomerate, trough cross bedded conglomerate, massive sandstone, trough cross bedded sandstone, planar cross bedded sandstone, ripple cross laminated sandstone-siltstone, flaser laminated sandstone-shale, lenticular laminated sandstone-siltstone-shale, parallel laminated sandstone-siltstone, wavy laminated shale, parallel laminated blue shale, and mudstone are delineated within this formation. Based on the grain size, sedimentary structures, water depth and genesis of individual facies, facies are grouped into three types of facies associations like (i) coarse-grained conglomerate facies association in relation to tractive current deposits of alluvial fan set up at the base of litho-succession (FAC), (ii) medium to fine-grained sandstone-siltstone-mudstone facies association or facies association in relation to strong tide (FAT) characterizing the middle part of litho-succession, (iii) very fine-grained sandstone-siltstone-mudstone facies association in relation to less frequent weak tide or heterolithic facies association (FAHL) characterizing upper part of litho-succession and shallow marine facies association (FASM) composing the uppermost litho-succession. Presence of gluconite indicates that the depositional environment was shallow to deep marine. The dominant paleoflow direction during the deposition of Dupi Tila Formation was toward southeast to southwestern direction. The rivers were of braided type at the piedmont alluvial depositional set up at the lower part, which later changed to estuarine–tidal flat type environmental set up in the middle part to upper part and paleo-environment was shallow marine in the uppermost part.

유사계의 역동성 감소가 지석천 충적하도의 지형변화에 미치는 영향

The present study aims to investigate the long-term channel morphological changes derived from channelization, embankment and levee construction works in unregulated fluvial channel of the Jiseock River. Analyses of aerial photographs taken past (Year 1966) and recent (Year 2002) showed the temporally remarkable changes in channel planform such as channel shape, bar migration, vegetation encroachment in bar. During the period, the natural single threading changed into braided types together with decreasing sinuosity by 9.2%, increasing vegetation occupied bar ranged 97% of total bars area. Because such channel morphological changes are closely similar to those in dam downstream channels, we assume that both/either flow regime alteration and/or sediment transport discontinuity may be critical for the fixed channel and spread of vegetated bars even in unregulated river without dam reservoir upstream. We found more reduced frequency and magnitude of flooding water level comparing with past, but no significant alteration of inter annual water level variation. Bed material has been coarsened by 4~5 times and the riverbed has been degraded in overall channel but aggraded locally in conjunction reach of tributaries. The results indicates that reduced sediment dynamics in fluvial channel which derived by bed material coarsening, river bed degradation and unbalanced sediment transport capacity between tributary and mainstem can be a causal factor to trigger channel morphological changes even in unregulated rivers.

Oscillatory solutions of fourth order conservative systems via the Conley index

In this paper we investigate periodic solutions of second order Lagrangian systems which oscillate around equilibrium points of center type. The main ingredients are the discretization of second order Lagrangian systems that satisfy the twist property and the theory of discrete braid invariants developed by Ghrist et al. (2003) [5]. The problem with applying this topological theory directly is that the braid types in our analysis are so-called improper. This implies that the braid invariants do not entirely depend on the topology: the relevant braid classes are non-isolating neighborhoods of the flow, so that their Conley index is not universal. In first part of this paper we develop the theory of the braid invariant for improper braid classes and in the second part this theory is applied to second order Lagrangian system and in particular to the Swift–Hohenberg equation.

Prediction of material properties of biaxial and triaxial braided textile composites

Biaxial and triaxial braided composites are modeled using finite element methods to predict effective material properties: for biaxial braids, diamond pattern (1/1), regular pattern (2/2), and Hercules pattern (3/3) are modeled, while for triaxial braids, a regular pattern (2/2) is modeled. A micromechanical approach is adopted to calculate material properties of the tows, which are critical compositions of braided composites. By applying periodical boundary conditions (PBC), four representative unit cells (RUC) in correspondence to the four types of braids are analyzed and compared. Subsequently, effective material properties are obtained with the braiding angle varying from 15° to 75° with an increment of 5°, from which the variation of the engineering constants with the braiding angle is studied. The prediction results are compared with the experimental values for two material systems, and good agreement is achieved.

Crushing Behaviors and Energy Absorption Efficiency of Hybrid Pultruded and ±45° Braided Tubes

A numerical and experimental investigation was carried out to evaluate the response and energy absorbing capacity of hybrid composite tubes made of unidirectional pultruded tube over wrapped with ±45° braided fiber-reinforced plastic (FRP). The numerical simulation characterized the crushing behaviors of these tubes subject to both quasi-static compression and axial dynamic impact loadings. Two types of FRP braids, that is, glass and carbon fibers braids were considered. Parametric studies were also conducted to examine the influence of the thickness and type of braid, as well as the loading conditions on the crushing behavior of the tubes. Due to its ease and controllability, quasi-static crushing tests were conducted to verify the numerical studies’ findings. Very good agreement was observed between the finite element simulation and experiments. It was observed that the presence of braids restrained the brittle crack propagation in pultruded tubes, thus reinforced the flexural behavior of the tube walls, and in turn improved their energy absorption capacity. Moreover, the hybrid tubes exhibited a more desirable, accordion type failure mode, therefore they are considered to be more suitable candidates as energy absorbing structural members in service conditions.

Using Multivariate Analyses to Assess Effects of Fluvial Type on Plant Species Distribution in a Mediterranean River

We propose a method to assess the distribution of plant assemblages along rivers delimiting homogeneous fluvial types using cluster analysis applied to morphological features, quantified with aerial photos and geographic information system software. A stratified random sampling design along the elevational gradient was used to analyze riparian plant species. Multivariate statistics were applied to detect patterns of variation in the species data, and among functional and ecological groups. Cluster analysis identified four fluvial types: headwater, low sinuosity, braided, and incised. Canonical Correspondence Analysis, INdicator SPecies ANalysis, and partial ordinations all suggested that fluvial types were characterized by well-defined indicator species. The differences found by Redundancy Analysis and non-parametric analysis of variance for functional and ecological groups also supported the fluvial type division, showing different distributional trends for annual and woody species, and the greatest ecological distance between braided and headwater types. Based on the ordination results, dividing fluvial types according to morphological features was justified by environmental and floristic differences, although plant species variability was only partially described. Our results illustrated that the fluvial type classification created using this methodology was consistent with natural plant species distribution patterns.

Channel patterns: Braided, anabranching, and single-thread

A new channel pattern classification is presented based on theoretically derived channel pattern discriminant functions. The thresholds are formulated as power laws that relate the critical slope associated with a change in channel pattern to dimensionless discharge and relative bank strength. One threshold demarcates the boundary between stable single-thread channels (both straight and meandering) and stable multiple-thread channels (anabranching). Another threshold separates anabranching from braided channels, where braided channels are considered to be fundamentally unstable. The exponents of the thresholds are nearly identical to that in the threshold equation originally proposed by Leopold and Wolman (1957), and the coefficients are quite similar as well. An analysis of their data set using our dimensionless approach reveals that no fundamental difference exists between meandering and straight patterns, and thus data from both types are grouped together under the more general heading of single-thread channels. Furthermore, we demonstrate that over a limited range of conditions, an unstable single-thread channel can form stable multiple-threads; but that for systems far from the threshold bounding the single-thread channels, the number of divisions required to produce stable anabranches grows geometrically: this motivates a separation of multiple-thread channels into anabranching and braided types. Our theoretical thresholds are then compared against several large data sets of field data, and the results broadly confirm our proposed thresholds.

東部南海トラフ海域のメタンハイドレート探査における堆積学的手法の適用

An integrated sedimentological workflow was applied to the methane-hydrate exploration project in the eastern Nankai Trough area, central Japan, as a useful tool to investigate the distributions and actual volume of methane hydrates. Since previous research revealed that most of the methane hydrates in the eastern Nankai Trough area occur in matrix pores of submarine-fan turbidite sandstones, the facies distribution of turbidite sandstones may be one of the important keys to evaluate the occurrence of methane hydrates. Accordingly, this study conducted a) core facies analysis, b) log facies analysis mainly using FMI, c) depositional sequence division, d) seismic facies analysis on the 2D/3D seismic sections, and e) seismic geomorphological analysis on the 3D seismic survey data to map submarine-fan turbidite facies distributions for 17 depositional sequence horizons in the targeted Pleistocene interval. The obtained facies maps reveal that submarine-fan depositional styles changed throughout Pleistocene from a braided channel type, through small radial fan, trough-fill fan, and muddy sheet fan types, to a channel-levee system type. As the next step, the facies maps of each depositional sequence were overlaid with bottom simulating reflector (BSR) distributions as a proxy of methane hydrates. The overlaid maps indicate that the BSRs occur on feeder channels, distributary channels, and proximal lobes of submarine fans, suggesting that methane hydrates selectively occur in coarser grained portions of a submarine fan. The facies maps were also used for calculation of average net-to-gross ratio of the methane hydrate occurrence zones, as the maps provide information on the spatial distributions of seismic facies class, which has individual value of net-to-gross ratio. Finally, this study analyzed reservoir-scale geologic bodies, such as depositional lobes and braided channels of a submarine fan, using 3D seismic survey data, and constructed a detailed geologic model for simulations of methane-hydrate generation and production.

Topological Entropy in a Parameter Range of the Standard Map

We combine the trellis method and the braid method, and by estimating the lower bounds of the topological entropy of the standard map for a certain parameter range, we follow the change of the topological entropy. The trellis in a tangency situation of the stable and unstable manifolds is constructed. Applying the trellis method to this trellis, the lower bound of topological entropy is calculated. There exist systems in which the trellis method can not be applicable. For such systems, we look for non-Birkhoff periodic orbits existent in the trellises, form braids from those periodic orbits, and estimate the topological entropy from their braid types. We perform these tasks for a sequence of trellises and numerically visualize the change in the topological entropy. In addition, we take particular sequence of connecting orbits to obtain homoclinic or heteroclinic orbits. As a natural extension, we assign topological entropy to these homoclinic and heteroclinic orbits. Subject Index: 030

シーケンス層序学手法による東部南海トラフエリアのメタンハイドレート含有海底扇状地タービダイト砂岩分布解析およびＢＳＲ分布との関連の検討

Since previous research revealed that most of the methane hydrates in the eastern Nankai Trough area occur in matrix pores of turbidite sandstones, the facies distribution of turbidite sandstones may be one of the important keys to evaluate the distributions and actual volume of methane hydrates in the eastern Nankai Trough area. This paper attempts to reconstruct depositional processes of submarine-fan turbidites, and examines the relationship between turbidite facies distributions and bottom simulating reflector (BSR) occurrence as a proxy of methane hydrate using sedimentologic and sequence stratigraphic methodology. First, 2D/3D seismic survey data and well data including cores and logs were used to identify turbidite facies, seismic facies, and depositional sequences. The targeted Plio-Pleistocene Kakegawa and Ogasa Groups can be divided into 17 depositional sequences, and include six seismic facies indicating submarine-fan elements and surrounding slope to basin-floor environments. Next, facies maps for each depositional sequence unit were created by plotting all information on seismic facies, 3D seismic geomorphology, and well facies data. The obtained facies maps reveal that 11 major submarine canyons functioned as positionally fixed sediment supply systems from main land Japan, along which submarine fans were formed in the forearc basins. Submarine-fan depositional styles changed through Plio-Pleistocene from a braided channel type, through small radial fan, trough-fill fan, and muddy sheet fan types, to a channel-levee system type. Finally, the facies maps of each depositional sequence were overlaid with the BSR distribution. The overlaid maps indicate that the BSRs occur on feeder channels, distributary channels, and proximal lobes of submarine fans, suggesting that methane hydrates selectively occur in coarser grained portions of a submarine fan. Because the lower part of the Kakegawa Group is mainly composed of braided channel-type submarine fan turbidites, the lower Kakegawa horizon serves one of the major horizons bearing methane hydrates in the eastern Nankai Trough area.

The forcing partial order on a family of braids forced by pseudo-Anosov 3-braids

Li-York theorem tells us that a period 3 orbit for a continuous map of the interval into itself implies the existence of a periodic orbit of ever y period. This paper concerns an analogue of the theorem for homeomorphisms of the 2-dimensional disk. In this case a periodic orbit is specified by a braid type and on the set of all braid types Boyland’s dynamical partial order can be defined. We de scribe the partial order on a family of braids and show that a period 3 orbit of pseudo-Anosov braid type implies the Smale-horseshoe map which is a factor possessing complicated chaotic dynamics.

PRELIMINARY APPROACH ON DEPOSITIONAL ENVIRONMENTAL OF THE UBERABA FORMATION (UPPER CRETACEOUS), PEIRÓPOLIS SITE, MINAS GERAIS STATE, BRAZIL: AN INTRODUCTION

The Coniacian-Santonian Uberaba Formation of Triângulo Mineiro region hás yielded a important paleofauna from fluvial and associated paleoenvironments. Although poor, fossil content are represented by invertebrates and vertebrates. The paleontological and geological data suggested that Uberaba Formation is characterized by a fluvial of a braided type.

The fluvial cycle at cold–warm–cold transitions in lowland regions: A refinement of theory

A previously established non-linear theory of river cyclicity as a response to climate change states that short phases of fluvial instability occur both at the transition from relatively warm (temperate) to cold (periglacial) and from relatively cold to warm periods. Such instability typically starts with vertical erosion, successively followed by sedimentary fill of the erosive scar. In spite of frequent confirmation of this theory by geomorphological reconstructions, a few problems arise. First, there are fewer incision phases than climatic transitions. Secondly, remnants of erosion at ‘cold–warm’ transitions are scarce, in contrast to obvious erosion relics at ‘warm–cold’ transitions. Furthermore, it appears that the incision style is strikingly different at both kinds of climatic transitions. Similarly, the long stable phases are also expressed in terms of different floodplain development in cold and warm periods. These arguments require a modification of the general non-linear theory. At the transition from relatively temperate to colder conditions, rivers transformed gradually from a regular, low-energy, single-channel course to a periodically high-energy, multi-channel type. The latter (braided) type is characterized by intense lateral movement, rather than by deep vertical erosion. This results in a well-expressed morphology of wide, extensive floodplains and terraces. In contrast, the linear and constrained, meandering channels incise with small width–depth ratio and build floodplains of limited lateral extent. Consequences are twofold: 1) the spatial limitation of the deeply incised, meandering valleys at the beginning of warm periods counts against their recognition; 2) relatively strong, lateral migration of the braided rivers removes most traces of previous (meandering) systems, which contrasts with the limited lateral activity of confined meandering channels. It means that in a ‘warm–cold–warm’ alternation generally only one phase of vertical erosion is preserved, the one that is caused by the high-energy, braided river at the start of the cold period.

Exceptional Self-Penetrating Networks Containing Unprecedented Quintuple-Stranded Molecular Braid, 9-Fold Meso Helices, and 17-Fold Interwoven Helices

Self-assembly of long V-shaped ligands and d10 metal salts in the presence of a linear bidentate ligand affords two unprecedented self-penetrating coordination networks {[Zn4(bptc)2(bpy)4].(C5H3N).4H2O}n (1) and {[Cd2(sdba)2(bpy)(H2O)2].2H2O}n (2) (bptc = 3,3',4,4'-benzophenonetetracarboxylate, sdba = 4,4'-sulfonyldibenzoate, bpy = 4,4'-bipyridine). Their structures were determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, X-ray powder diffraction, and TG analyses. 1 adopts a novel 3D framework containing three types of molecular braids, among which the quintuple-stranded molecular braid represents the highest-stranded molecular braid presently known for entangled systems. 2 is an uncommon self-penetrating 2D network containing pseudo-Borromean links and double-stranded helices. More interestingly, when the strong hydrogen bonds between layers are taken into account, the resulting net of 2 becomes an eight-connected 3D self-penetrating network with an unprecedented (421.67) topology, which represents the highest connected topology presently known in self-penetrating systems. Furthermore, the photoluminescent properties of 1 and 2 were studied.

Conjugacy Problem for Subgroups with Applications to Artin Groups and Braid Type Group

Let G be a group endowed with a solution to the conjugacy problem and with an algorithm which computes the centralizer in G of any element of G. Let H be a subgroup of G. We give some conditions on H, under which we provide a solution to the conjugacy problem in H. We apply our results to some Artin groups and braid type groups. In particular, we give solutions to the explicit conjugacy problem in the Artin groups of type and .

A numerical study on the axial crushing response of hybrid pultruded and ±45° braided tubes

Abstract A comprehensive numerical investigation was carried out to evaluate the response and energy absorbing capacity of hybrid composite tubes made of unidirectional pultruded tube over wrapped with ±45° braided fiber-reinforced plastic (FRP). The numerical simulation characterized the crushing behaviors of these tubes subject to both quasi-static compression and axial dynamic impact loadings. Two types of braided FRP, glass and carbon fibers, were considered. Parametric studies were also conducted to examine the influence of the tube’s length, thickness and type of braid, as well as the loading conditions on the crushing behavior of the tubes. It was observed that although the pultruded tube, which had the highest stiffness among the tubes considered, produced the highest magnitude of energy absorption capacity, it exhibited a non-symmetric failure mode followed by a longitudinal splitting. On the other hand, the hybrid tubes exhibited a more desirable, accordion type failure mode, therefore they are considered to be more suitable candidates as energy absorbing structural members in service conditions.

The sedimentology and alluvial architecture of the sandy braided South Saskatchewan River, Canada

AbstractGround penetrating radar (GPR) surveys of unit and compound braid bars in the sandy South Saskatchewan River, Canada, are used to test the influential facies model for sandy braided alluvium presented by Cant & Walker (1978). Four main radar facies are identified: (1) high‐angle (up to angle‐of‐repose) inclined reflections, interpreted as having formed at the margins of migrating bars; (2) discontinuous undular and/or trough‐shaped reflections, interpreted as cross‐strata associated with the migration of sinuous‐crested dunes; (3) low‐angle (< 6°) reflections, interpreted as formed by low‐amplitude dunes or unit bars as they migrate onto bar surfaces; and (4) reflections of variable dip bounded by a concave reflection, interpreted as being formed by the filling of channel scours, cross‐bar channels or depressions on the bar surface. The predominant vertical arrangement of facies is discontinuous trough‐shaped reflections at the channel base overlain by discontinuous undular reflections, overlain by low‐angle reflections that dominate the deposits near the bar surface. High‐angle inclined reflections are only found near the surface of unit bars, and are of relatively small‐scale (< 0·5 m), but can be found at a greater range of depths within compound bars. The GPR data show that a high spatial variability exists in the distribution of facies between different compound bars, with facies variability within a single bar being as pronounced as that between bars. Compound bars evolve as an amalgamation of unit bars and other compound bars, and comprise a facies distribution that is representative of the main bar types in the South Saskatchewan River. The GPR data are compared with the original model of Cant & Walker (1978) and reveal a much greater variability in the scale, proportion and distribution of facies than that presented by Cant & Walker (1978). Most notably, high‐angle inclined strata are over‐represented in the model of Cant and Walker, with many bars being dominated by the deposits of low‐ and high‐amplitude dunes. It is suggested that further GPR studies from a range of braided river types are required to properly quantify the full range of deposits. Only by moving away from traditional, highly generalized facies models can a greater understanding of braided river deposits and their controls be established.

モール状捕集システムによる海水ウラン捕集のコスト試算

モール状捕集システムによる海水ウラン捕集のコスト試算

Embeddings of a strange attractor into R3.

The algorithm for determining a global Poincaré section is applied to a previously studied dynamical system on R2 x S1 and a one-parameter family of embeddings of the strange attractor it generates into R3. We find that the topological properties of the attractor are embedding dependent to a limited extent. These embeddings rigidly preserve mechanism, which is a simple stretch and fold. The embeddings studied show three discrete topological degrees of freedom: parity, global torsion, and braid type of the genus-one torus bounding the embedded attractor.

BIFURCATIONS OF VORONOI DIAGRAMS AND ITS APPLICATION TO BRAID THEORY

We study bifurcations of Voronoi diagrams on the plane. The generic bifurcations of Voronoi diagrams for moving points are classified into four types. A braid has an associated family of Voronoi diagrams. If we admit only three types among four in the associated generic family of Voronoi diagrams, the braid type reduces to a braid with k half twists for some integer k.