Discrete Bars Research Articles

Depositional and sequence stratigraphic model of transgressive shelf sandstone: The Late Cretaceous Tocito Sandstone, San Juan Bain, New Mexico, U.S.A.

ABSTRACT There has long been debate about the origin of long, linear, isolated shallow marine sandstones. In the 1980s these were routinely interpreted as wave- or tide-modulated shelf sandstones. With the advent of sequence stratigraphy, many of these sandstones were reinterpreted as top-truncated forced-regressive to lowstand delta or shoreface, inviting the question regarding whether the concept of a shelf sandstones remain a viable depositional model. More recent syntheses demonstrate that shelf sands tend to be derived by reworking of underlying sediment through transgressive erosion and show varying levels of detachment and reworking into discrete ridges and bars by wave and tidal processes as they become more evolved. The Late Cretaceous Tocito Sandstone in the Western Interior Seaway, which overlies the regressive Gallup Formation, is a candidate for a transgressive shelf sandstone. In this study, we present detailed facies analysis, based on sedimentological sections measured from well-exposed outcrops of the Tocito Sandstone and its related stratigraphic units in northwest New Mexico, USA. With high-resolution sequence stratigraphic control, facies analysis, detrital-zircon anatomy, and petrographic analysis are integrated to investigate the sequence stratigraphic evolution and depositional processes of the Tocito Sandstone. Detrital zircons indicate that the Tocito, Torrivio, and Gallup deposits are derived from different source areas, and therefore imply separate sequence stratigraphic origins. The Tocito Sandstone is interpreted to have been deposited as shelf sand ridges in retrogradational estuarine to drowned-barrier-system environments with tidal and wave influence, characterized by intense bioturbation. The Tocito was deposited in an overall transgressive systems tract and sourced from reworking of the underlying Torrivio and Gallup units through processes of transgressive erosion.

Cracking analysis of plane stress reinforced concrete structures

This article presents the numerical analysis’ results of reinforced concrete elements subjected to plane stress in early cracking stage. The elements are modelled by a concrete two-dimensional matrix, discrete reinforcement bars and bond-slip elements. The aim of this study is to investigate the behaviour of RC structures before and after the formation of the first cracks to understand the influence on the crack spacing and width of bar orientation with respect to the crack direction, bar spacing and diameter and presence of shear stresses on the crack. Discrete crack non-linear analysis of elements with reinforcement both orthogonal and skew to the crack directions are performed. The interaction between concrete and steel is ensured by a non-linear bond slip law at the interfaces between the two materials. The crack spacing obtained numerically are compared with the ones calculated using different design codes. The analysis of models with different reinforcement geometries allows individuating and discussing the main factors governing two-dimensional plane stress concrete cracking behaviour.

Multiple behavioral contexts of a melanized tail display in a desert lizard

AbstractConspicuous color displays in animals are often studied in the context of how they communicate an individual's reproductive value, ability to escape capture, or overall health. The study of sexual dichromatism often focuses on the evolution of male display traits balanced between detectability and mate acquisition, representing constraints stemming from both natural and sexual selection. Melanistic coloration and melanin color patterns play important roles in both intraspecific and interspecific signaling in animals; as melanin serves multiple purposes in organismal biology, the evolution of melanin‐based visual displays might not be restricted to a single behavioral or ecological context. Here, we examine the behavioral contexts of the conspicuous melanin‐based tail display in the greater earless lizard (Cophosaurus texanus), asking if this melanized tail pattern is associated with (a) female association preference of males varying in the concentration of melanin, (b) individual locomotor performance capacity, and (c) thermal ecology. We found the amount of tail melanin is linked with both locomotor performance and female association preference, with greater concentrations of melanin predicting the evolution of faster performance capacities and females preferring males with more discrete melanin bars. We found limited support that differences in melanin are linked with thermoregulation or thermal ecology. Overall, we find that multiple behavioral contexts shape the evolution of this melanized display trait. We conclude that behavioral constraints stemming from both natural and sexual selection can interact synergistically to favor the evolution and expression of a melanistic visual display, even in potentially costly ecological contexts.

Experimental Verification of Same Simple Equilibrium Models of Masonry Shear Walls

This paper contains theoretical fundamentals of strut and tie models, used in unreinforced horizontal shear walls. Depending on support conditions and wall loading, we can distinguish models with discrete bars when point load is applied to the wall (type I model) or with continuous bars (type II model) when load is uniformly distributed at the wall boundary. The main part of this paper compares calculated results with the own tests on horizontal shear walls made of solid brick, silicate elements and autoclaved aerated concrete. The tests were performed in Poland. The model required some modifications due to specific load and static diagram.

Efficiency of glass-fiber reinforced-polymer (GFRP) discrete hoops and bars in concrete columns under combined axial and flexural loads

Abstract Discrete hoop reinforcement is preferable over continuous spiral reinforcement due to ease of construction in bridge applications. This research presents the experimental results of full-scale circular concrete columns reinforced with glass-fiber-reinforced-polymer (GFRP) bars and confined with GFRP discrete hoops subjected to combined axial compression loads and bending moments. The findings of the experimental work were integrated with a theoretical analysis based on the strain computability and force equilibrium to extend the parametric study. The lowest and highest bounds of the mechanical properties of GFRP reinforcement along with concrete strength and reinforcement ratio were employed. Sets of axial force–bending moment ( P-M ) interaction diagrams and indicative guide charts are introduced, and recommendations drawn. The compressive-strength contribution of GFRP reinforcement is reviewed and discussed. The results reveal that the GFRP bars developed compression and tension strains up to −0.003 and 0.008 at peak loads and up to −0.015 and 0.0135 at failure on the compression and tension sides, respectively. The confinement provided by GFRP discrete hoops (9.5 mm) spaced at 80 mm prevented the buckling of longitudinal GFRP bars up to and even past the peak load until failure occurred. Based on the experimental and theoretical results, the minimum GFRP longitudinal reinforcement ratio was found to be 1% in order to prevent tension failure (GFRP-bar rupture), provided that the mechanical properties comply with the limits of the available codes and standard.

Evaluation of the Side Lobe Level Properties of 1-3 and 2-2 Piezocomposite Sonar Transducers with Printed Triangular Shape Electrodes in Comparison to a Convention Transducer Comprising of six PZT Bars with Analogue Network

In a sonar line array the side lobes in the horizontal direction are controlled (reduced) using signal processing, while in the vertical direction are determined by the transducer design. Conventionally, this is done by using a transducer comprising discrete PZT bars spaced vertically and an analogue electronics network to apply different amplitudes to the bars. In this paper we present such a transducer comprising six PZT bars with its analogue network to produce a triangular shading (-24dB main / side lobe level) and compare its performance to transducers made of 1-3 and 2-2 piezocomposite materials with printed triangular shape electrodes. All transducers were designed to operate between 400kHz and 450kHz. The measured receiving frequency response and polar directivity responses of the three transducers (including networks) will be presented and compared to the theoretical simulations. The results obtained showed significant improvement to the main lobe to side lobe ratio with both 1-3 and 2-2 piezoelectric based transducers. The transducers made with 1-3 piezocomposite material also achieved higher receiving response level. The fabrication of the 1-3 and 2-2 piezocomposite transducers with the printed electrodes also proved to be simpler and more cost effective.

Sensitivity, persistence and resolution of the geomorphological record of valley-floor floods in an alpine glacier-fed catchment, Leirdalen, Jotunheimen, southern Norway

Coarse-grained flood deposits, including 52 discrete berms, bars, terraces, splays and sheets, were investigated along a 6.6 km stretch of the Leira river, in a catchment containing several alpine glaciers. These landforms were mapped, characterized in terms of clast size and reconstructed hydrological parameters, and dated using several techniques with differing temporal range and resolution. High-resolution lichenometric dating indicated that 60–65% of the deposits date from the 20th century whereas 5.7% are 300–600 years old. In contrast, low-resolution Schmidt-hammer exposure-age dating (SHD) indicated that 85% of deposits have an age <500 years whereas 13.5% are older deposits with age estimates of 1000–6000 years. Simple indicators of soil development and vegetation succession demonstrated extensive recent disturbance of most surfaces by floods. Optically stimulated luminescence (OSL) and radiocarbon dating of fine-grained flood layers and buried palaeosols confirmed the existence of flood deposits spanning the whole of the Holocene. Apparent discrepancies between dating techniques are explained by a complex pattern of overwashing and reworking, which is related to height of flood deposits above the active river channel, and downstream patterns of disturbance associated especially with tributary confluences. While, in general, these deposits are of low persistence and most are highly sensitive to disturbance, some elements of the valley-floor landscape have persisted throughout the Holocene. Comparison of this fragmentary geomorphological record of floods with the historical flood record shows that the surviving deposits are sensitive to recent multidecadal-scale glacier and climatic variations.

Building Information Modeling–Based Analysis to Minimize Waste Rate of Structural Reinforcement

AbstractBuilding information modeling (BIM) is an emerging tool in architecture/engineering/construction (A/E/C) industry that is used to design, document, and enhance communication among all the project stakeholders. Trim loss of rebar can be minimized with the use of discrete bars. To achieve this goal, a model to analyze reinforced concrete structure with one-dimensional (1D) cutting waste-optimization technique, integrated with BIM, is proposed. Building information modeling is selected as the hub in communicating project information among diverse design teams. This process permits project teams to utilize BIM models to simulate architectural and structural design requirements, and compare results speedily to make necessary changes in the designs to minimize rebar waste. The BIM rebar optimization analysis approach also supports cost-effective decision making during the design process. The proposed approach was validated with a two-story reinforced concrete structure, and the results indicated a high ...

Septins AspA and AspC Are Important for Normal Development and Limit the Emergence of New Growth Foci in the Multicellular Fungus Aspergillus nidulans

Septins are cytoskeletal proteins found in fungi, animals, and microsporidia, where they form multiseptin complexes that act as scaffolds recruiting and organizing other proteins to ensure normal cell division and development. Here we characterize the septins AspA and AspC in the multicellular, filamentous fungus Aspergillus nidulans. Mutants with deletions of aspA, aspC, or both aspA and aspC show early and increased germ tube and branch emergence, abnormal septation, and disorganized conidiophores. Strains in which the native aspA has been replaced with a single copy of aspA-GFP driven by the native septin promoter or in which aspC has been replaced with a single copy of aspC-GFP driven by the native promoter show wild-type phenotypes. AspA-GFP and AspC-GFP show identical localization patterns as discrete spots or bars in dormant and expanding conidia, as rings at forming septa and at the bases of emerging germ tubes and branches, and as punctate spots and filaments in the cytoplasm and at the cell cortex. In conidiophores, AspA-GFP and AspC-GFP localize as diffuse bands or rings at the bases of emerging layers and conidial chains and as discrete spots or bars in newly formed conidia. AspA-GFP forms abnormal structures in DeltaaspC strains while AspC-GFP does not localize in DeltaaspA strains. Our results suggest that AspA and AspC interact with each other and are important for normal development, especially for preventing the inappropriate emergence of germ tubes and branches. This is the first report of a septin limiting the emergence of new growth foci in any organism.

Blocking temperature in nanocrystalline systems with “alloy-like” ferromagnetic–antiferromagnetic heterogeneous morphology

A modified Monte Carlo Metropolis method is performed to simulate the blocking temperature (TB) in an “alloy-like” ferromagnetic(FM)x–antiferromagnetic(AFM)1−x heterogeneous system with geometrical frustration. It is found that the blocking temperature, at which the field-cooled (FC) and zero-field-cooled (ZFC) magnetization curves are splitting, changes little for x≤0.5 initially, then decreases obviously with the increase in x. Some discrete error bars emerge for large x owing to the superparamagnetic or agglomerate behavior of the small antiferromagnet. Using a thermal fluctuation model, an analytic expression for TB as a function of x is obtained. By calculating the curves of temperature derivative of the difference between FC and ZFC magnetizations and analyzing the distribution of energy barriers, we interpret the dependence of TB on different proportions of ferromagnetic phase in detail.

On the solution of multi-point constraints – Application to FE analysis of reinforced concrete structures

The paper presents an efficient way of implementing general multi-point constraint conditions in a finite element solver. The proposed method of applying and processing the multi-point constraints on the primary unknown variables of finite element method is computationally efficient and memory economical, because all constrained degrees of freedoms (DOFs) are already eliminated during the assembly of the global stiffness matrix and right-hand side vectors. The adopted concept has a wide range of use, and several of its possibilities are discussed. At the end of the paper, sample analyses of reinforced concrete structures are presented that demonstrate the advantages of the developed form for modelling discrete reinforcement bars in non-linear FE calculation in engineering practice.

Algorithms for Reducing the Waste Rate of Reinforcement Bars

Loss of rebars can be minimized with minimum use of discrete bars in market length. In order to achieve this goal, the accurate and detailed information of rebars is extracted, followed by both rapid and efficient bar combination. No paper has dealt directly with the reduction of rebar waste rates, although many researches have proposed indirect approaches to enhance productivity, constructability, safety and quality in the process of concrete reinforcement work. This paper, therefore, was prepared with the aim of developing algorithms to supply rebars required to minimize material waste during cutting and bending of discrete bars in rebar shops. At the same time, this study presented an automatic rebar detailing concept, a logical process of rebar combination with pertinent algorithms and binary search algorithm for bar data to implement the proposed topic. The effectiveness of the suggested algorithms was validated by case studies.

Elimination of Saturation Effects in Sensorless Position-Controlled Induction Motors

Owing to the variable magnetic coupling between the stator windings and the discrete rotor bars of an induction motor, a quasicontinuous rotor position signal can be acquired by instantaneous measurement of the total leakage inductance of the three stator phases. The signals are sampled in synchronism with the regular commutations of the pulsewidth-modulation process, thus making the injection of additional high-frequency carriers obsolete. The acquired position signal exhibits high spatial resolution and high dynamic bandwidth. Magnetic saturation also influences the total leakage inductances and, hence, constitutes a disturbance for position identification. This paper presents a detailed analysis of the saturation effects and proposes methods to eliminate their undesired impact on the position signal. Experimental results of closed-loop sensorless position control at full load and high dynamic performance are presented.

Reinforcement-bar manufacture: From design to optimized production

An integrated system which automates the design and manufacture of rebars (reinforcement bars) is described. The system has four modules: Design, data extraction, production planning and an NC production. The rebar design process can be accomplished using customized semi-automated functions in a graphic system, or by conventional computer aided design. The data extraction module automatically extracts the data needed for manufacturing from the graphic design database. This rebar data is analysed to create an optimal rebar manufacturing plan, and convert it into a series of control programmes which can be automatically transferred to the rebar manufacturing machines. Thus all the manual data manipulation stages of traditional rebar design and production (detailing, documentation, data extraction, etc.) are avoided, reducing the potential for errors, and saving data input costs. The optimized production planning results in reduction of material scrap on machines which use discrete bars as raw material. The automatic creation and transfer of the rebar programme to the machine controller saves considerable set-up time between different production batches. Consequently, the integrated CAD/ CAM system described here leads to cost reduction together with increased quality.

Simulation of hygral crack growth in concrete repair systems

In this paper, results of numerical simulations of a repaired concrete structure are presented. A repair layer of mortar was cast on top of a substrate of old concrete. The repair mortar was staturated with water, and allowed to dry at the top surface. The moisture distribution was determined using the finite element code DIANA. The moisture gradients lead to shrinkage cracking. Using the smeared crack model available in DIANA, and from the effect of decreasing the thickness of the overlay of repair mortar (from 60 to 15 mm), and by decreasing the bond strength between repair mortar and substrate from 3 to 1 MPa, it is shown that the number of hygral shrinkage cracks depends largely on the thickness of the repair layer. Moreover, in analyses with high interfacial strength, the cracks were found to propagate into the substrate. However, at lower bond strength, debonding was observed. The analyses show that hygral strains may cause severe damage in a repaired concrete system. Problems may decrease when the overlay thickness increases or when the bond between substrate and overlay is improved. In addition, applying reinforcement in the repair layer, either as discrete bars or as distributed fibres, may decrease the spacing and width of the shrinkage cracks, thereby reducing the probability of delamination. The numerical programme is shown to be a viable tool for damage analyses not only under mechanical load, but also under hygral gradients (and thermal gradients).

Early Proterozoic gold placers of the Moeda Formation within the Gandarela Syncline, Minas Gerais, Brazil

Gold-bearing placer conglomerates, dated between 2.2 and 2.8 Ga, have been identified at the base of the Moeda Formation in the Gandarela syncline. Intensive investigation of outcrop and underground exposures, both old and new, and borehole intersections around the western and southern margin of the syncline, has defined a paleoenvironment consisting of an upland fluvial drainage system in the north, leading southward to an alluvial fan and braided plain depository. Heavy mineral concentrates, composed predominantly of coarse rounded pyrite, are concentrated in the matrix of cobble conglomerates that occur in the form of discrete bars and sheets. The mineralogy and geochemistry of the ore closely resembles that of Witwatersrand placers as does the composition of the gold. Gold concentrations are equal to those of the average Witwatersrand gold deposit and therefore these deposits may make a significant contribution to Brazil9s future gold production.

Optimization of rectangular transmission gratings: Applications to new monochromator design

In this paper we examine the conditions under which a rectangular grating may have its zeroth order of diffracted light completely suppressed, yielding approximately 41% output efficiency into each first order. We show that the higher orders will always be present in any grating with discrete bars, and thus that the above condition is also optimal in an important sense. Other equally important optimization conditions are discussed and practical consequences in terms of new monochromator design are presented.

Discrete bars, conductive heat transfer and elasticity

An arithmetic, energy conserving formulation of n-body interaction is applied to discrete models of heat transfer and elasticity. Computer examples are given for discrete bar models.

Steel Plate Analysis by Finite Elements

The finite element method is becoming a popular as well as practical way of analyzing plates, shells, and related structures. The technique of modeling an elastic structure into an assemblage of discrete bars or sections and interconnecting these elements by a finite number of joints or nodal points is not new. The growth and development of the finite element method has been greatly enhanced by the high speed digital computer and matrix methods in structural mechanics. Extended finite element formulation is being carried on to increase the potential of this method in the areas of plasticity, vibration, and three-dimensional stress applications. Although continuous investigation is being undertaken, it might be in order to review the basic finite element formulation and provide a simplified method of evaluation for the practicing engineer.