Lateral Bars Research Articles

Let the river erode! Enabling lateral migration increases geomorphic unit diversity.

River restoration practice frequently employs conservative designs that create and maintain prescribed, static morphology. Such approaches ignore an emerging understanding of resilient river systems that typically adjust their morphology in response to hydrologic, vegetative and sediment supply changes. As such, using increased dynamism as a restoration design objective will arguably yield more diverse and productive habitats, better managed expectations, and more self-sustaining outcomes. Here, we answer the following question: does restoring lateral migration in a channelised river that was once a wandering gravel-bed river, result in more diverse in-channel geomorphology? We acquired pre- and post-restoration topographic surveys on a segment of the Allt Lorgy, Scotland to quantify morphodynamics and systematically map geomorphic units, using Geomorphic Unit Tool (GUT) software. GUT implements topographic definitions to discriminate between a taxonomy of fluvial landforms that have been developed from an extension of the River Styles framework, using 3-tiered hierarchy: (1) differentiation based on stage or elevation relative to channel; (2) classification of form based on shape (mound, bowl, trough, saddle, plane, wall); and (3) mapping geomorphic units based on attributes (e.g., position and orientation). Results showed restoration increased geomorphic unit diversity, with the Shannon Diversity Index increasing from 1.40 pre-restoration (2012) to 2.04 (2014) and 2.05 (2016) after restoration. Channel widening, due to bank erosion, caused aerial coverage of in-channel geomorphic units to increase 23% after restoration and 6% further in the two-years following restoration. Once bank protection was removed, allowing bank erosion yieled a local supply of sediment to enable the formation and maintenance of lateral and point bars, riffles and diagonal bar complexes, and instream wood created structurally-forced pools and riffles. The methodology used systematically quantifies how geomorphic unit diversity increases when a river is given back its freedom space. The framework allows for testing restoration design hypotheses in post-project appraisal.

Reform and exploration of computer aided design and Analysis Course under the background of “new engineering”

In response to the requirements of new engineering construction and reform, the new experimental teaching mode of the comprehensive practice link of computer-aided engineering analysis course was explored, and the “finite element analysis of the lateral stabilizer bar of new energy bus” was introduced into the comprehensive practice of the course to train students’ autonomy learning ability. At the same time, it has improved students’ scientific research and teamwork ability, and used project-based teaching as a link to open up the separation between undergraduate teaching and postgraduate teaching, cultivated students’ ability to continue learning, strengthened the combination of theoretical knowledge and engineering application, and improved student in solving the ability of the problem. It provides a reference for the curriculum reform under the background of “new engineering”.

Reach‐scale changes in channel geometry and dynamics due to the coastal backwater effect: the lower Trinity River, Texas

AbstractIn this paper we use multiple field surveys spanning several decades to systematically evaluate the geomorphic consequences of a change in flow hydraulics from uniform flow to backwater flow for the lower Trinity River in east Texas, USA. Spatial changes in lateral migration rate, channel geometry, and point bar size correspond to two distinct geomorphic zones. Within the upstream uniform flow reach, the river channel is defined by fully developed point bars and a high rate of lateral channel migration. This zone transitions where the median channel bottom elevation drops below sea level. At this point flow is affected by the backwater influence of the Trinity Bay water surface elevation, as opposed to being bed slope control dominated. The change in hydraulics within the backwater zone is reflected in the channel morphology, which is characterized by smaller point bars, narrower and more symmetrical cross‐sectional channel geometry, lower channel migration rates, and little to no bend deformation or cutoffs. Studying the connection between channel geometry, river bend kinematics, sediment transport, and fluid mechanics in each zone provides a deeper understanding of the relationship between channel shape and river mechanics. © 2019 John Wiley & Sons, Ltd.

Development and Early-Age Performance of an Innovative Prestressed Precast Concrete Pavement

Use of precast concrete pavement (PCP) for rapid construction of roads has gained high popularity in the last decade. In this technology, precast pavement panels are cast in a precast yard, transported to the construction site, placed on a prepared subbase, and connected using dowel bars. This paper describes one such application, reported for the first time in India. Planning, analysis, design, construction, and testing of a 24-m road length was discussed. An empirical equation was developed to obtain the stresses induced in the panel. It also includes an innovative load transfer mechanism (LTM) using a lateral dowel bar arrangement instead of the commonly used longitudinal dowel bar arrangement. This LTM is easier to implement, helps to maintain good riding quality, provides faster construction speed, and does not compromise the load transfer efficiency (LTE). The load transfer efficiency of the newly developed LTM was found to be 97% 6 months after placement of the panels.

Morphological variation and asymmetrical development in the skull of Styracosaurus albertensis

The ceratopsid Styracosaurus albertensis is an important component of the herbivorous dinosaur fauna preserved in the Campanian-aged Dinosaur Park Formation in Alberta, Canada. A new skull (UALVP55900) exhibits previously unobserved variability and asymmetry in this species. As in the type, the right lateral parietal bar bears seven epiossifications, but the left parietal bar has eight. Epiossifications p3‒p6 are asymmetrical with respect to size, orientation, and position relative to the midline. A re-evaluation of variation in Styracosaurus that includes this skull expands the morphological range of the taxon to incorporate Rubeosaurus ovatus, requiring the synonymy of the latter with the former. Unlike the type, both p1 and p2 epiossifications of UALVP 55900 are large. Epiossification p1 is procurved, and p2 is medially curved. These features converge on the morphology considered diagnostic for Centrosaurus. This observation, in combination with their sequential stratigraphic relationship and geographic overlap might suggest that Centrosaurus and Styracosaurus form an anagenic series, but the stratigraphic placement of skulls exhibiting putative transitional morphologies does not support this hypothesis.

Calculated Potential Bedload Versus Real Transported Sands along the Guadiana River Estuary (Spain–Portugal)

The Guadiana estuary is a coastal system located in the southwest of the Iberian Peninsula and is the natural border between Portugal and Spain. It is a rock-bounded estuary which extends along more than 40 km and is characterized by a semidiurnal mesotidal regime. This paper represents an approach to the bedload transport across two flow sections located in the fluvial and marine domains. In the fluvial profile, the most frequent bedform is the plane bed. In the marine area the bed of the deep channel is composed of well-sorted sand, while a lateral bar displays partially cohesive sediments with dominant fine sands in a matrix of clayey silts. Data were acquired during spring and neap tides. Near-bottom water velocities were registered by an acoustic Doppler current profiler (ADCP). Density and bed rugosity were determined in sediment samples. These data were employed using Bagnold’s equation (1963) to quantify the potential bedload (Qb). Further, real bedload values (Sb) were obtained by using Poliakoff traps. The comparison of the results of Qb under both ebb and flood conditions demonstrated a clear river-to-sea net transport in both sectors. The values of Sb were lower than those of Qb in every condition. The sand input across the fluvial estuary cannot supply the potential bedload in the lower domain of the channel, thereby causing a deficit that explains this lack of agreement between potential and real transport.

Coarse sediment storage and connectivity and off-highway vehicle use, Board Camp Creek, Arkansas

Upper Board Camp Creek (BCC) in western Arkansas drains the Wolf Pen Gap (WPG) Trail Complex, a designated Off-Highway Vehicle (OHV) area in use since the 1990s. The mixed bedrock-alluvial channel is quite active, with extensive bars and eroding banks present within the higher-order, main-valley channels. This study was conducted to determine the relative magnitudes of sediment storage and production within the channel, and whether geomorphic changes are synchronous with establishment and increasing OHV use levels on the trail system. Fourteen geomorphically active reaches within the main-valley channels, representing the range of conditions of BCC within the WPG complex, were examined in detail. All sites had significant alluvial storage in the form of point, lateral, or mid-channel bars dominated by cobble and gravel. Sediment storage volumes ranged from 140 to nearly 10,000 m3 per kilometer of channel, with a mean of about 3400. Eleven of 14 reaches also had actively eroding banks. Ten reaches (71%) exhibited net sediment storage. Two are possible net sources, and two may be in approximate steady state (storage ≈ erosion). The imbalance between local bank erosion sources and in-channel storage, and the evidence of activity and mobility of most of the bars indicates a connected system, with coarse sediment mobile during banktop flow events, and no evidence of sediment starvation. Finer (<8 mm) sediment from the trail system does not seem to be accumulating in the stream, suggesting that most is either sequestered before reaching BCC Creek, transported downstream, or deposited on floodplains during overbank flow. Many of the channel bars predate the trail complex, and most are active. This suggests that these features constitute mainly transient storage and are an inherent feature of the channel. At only two reaches could geomorphic changes be confidently attributed to the trail system. Like many streams, BCC has an active channel, independent of the WPG trail system. These results highlight the difficulty of attributing fluvial change to specific causes or forcings in active fluvial systems.

Identification of second-gradient elastic materials from planar hexagonal lattices. Part I: Analytical derivation of equivalent constitutive tensors

A second-gradient elastic (SGE) material is identified as the homogeneous solid equivalent to a periodic planar lattice characterized by a hexagonal unit cell, which is made up of three different linear elastic bars ordered in a way that the hexagonal symmetry is preserved and hinged at each node, so that the lattice bars are subject to pure axial strain while bending is excluded. Closed form-expressions for the identified non-local constitutive parameters are obtained by imposing the elastic energy equivalence between the lattice and the continuum solid, under remote displacement conditions having a dominant quadratic component. In order to generate equilibrated stresses, in the absence of body forces, the applied remote displacement has to be constrained, thus leading to the identification in a ‘condensed’ form of a higher-order solid, so that imposition of further constraints becomes necessary to fully quantify the equivalent continuum. The identified SGE material reduces to an equivalent Cauchy material only in the limit of vanishing side length of hexagonal unit cell. The analysis of positive definiteness and symmetry of the equivalent constitutive tensors, the derivation of the second-gradient elastic properties from those of the higher-order solid in the ‘condensed’ definition, and a numerical validation of the identification scheme are deferred to Part II of this study.

A Decoupling Design with T-Shape Structure for the Aluminum Nitride Gyroscope.

This paper reports a novel design for the decoupling of microelectromechanical systems (MEMS) gyroscopes. The MEMS gyroscope is based on piezoelectric aluminum nitride (AlN) film, and the main structure is a mass hung by T-shape beams. A pair of parallel drive electrodes are symmetrically placed on the surface of the vertical bar for driving the oscillating mass. A serpentine sense electrode is placed on the lateral bar. When the gyroscope is oscillating in drive mode, charges with equal quantity and opposite sign will be polarized and distributed symmetrically along the lateral bar. These charges neutralize each other at the sense electrode. Therefore, no coupling signals can be detected from the sense electrode. This design can realize the decoupling between the drive mode and sense mode. In this work, the T-shape decoupled structure was designed as the key component of an AlN piezoelectric gyroscope and the whole structure was simulated by COMSOL Multiphysics 5.2a. The working principle of the decoupling is described in detail. Electrical properties were characterized by the dynamic signal analyzer. According to the test results, the drive mode and the sense mode are decoupled. The coefficient of orthogonal coupling is 1.55%.

Dynamics Study of Straddle-Type Monorail Vehicle With Single-Axle Bogies-Based Full-Scale Rigid-Flexible Coupling Dynamic Model

The longitudinal drawbar and the lateral stabilizer bar of straddle-type monorail vehicle with the single-axle bogies have relatively long structure size. The multibar system leads to deformation during the driving process due to impact loads, even leads to influence on the dynamic characteristic of the hauling mechanism as well as the riding comfort of the whole vehicle. To evaluate the dynamic behavior of straddle-type monorail vehicle with single-axle bogies accurately, a full-scale rigid-flexible coupling multibody dynamics method is proposed based on multibody dynamics and finite element (FE) theory. The modal synthesis method is adopted to establish flexible multibody dynamics of the single-axle bogies. And then rigid-flexible coupling dynamic model of the straddle-type monorail vehicle is established with the ADAMS software. The validity of the full-scale model is verified. Finally, the influences of vehicle velocity, passenger mass, curve radius and the number of axles on dynamic characteristics are discussed.

Polarization of Pochhammer–Chree Waves: Axisymmetric Longitudinal Modes

Exact solutions to the Pochhammer–Chree equation describing harmonic wave propagation in an elastic cylindrical bar are analyzed. For the first time, spectral analysis of the matrix of dispersion equation is performed for axisymmetric longitudinal modes. Analytic expressions for wave polarization are derived. For the fundamental axisymmetric longitudinal mode, polarization coefficients of the corresponding waves at the bar surface are determined and frequency dependent variations of the coefficients are analyzed. It is found that, when the phase velocity of the fundamental axisymmetric longitudinal mode coincides with the velocity of transverse waves, all the displacement components determined at the lateral bar surface simultaneously vanish, which is significant for acoustic waveguide design.

안정바와 측면봉 사용에 따른 샤워배변 휠체어의 강도 및 강성 해석

안정바와 측면봉 사용에 따른 샤워배변 휠체어의 강도 및 강성 해석

Research on separation mechanism of waste palladium catalyst in a structure-optimized compound dry separator based on DEM-CFD

Recovery of precious metals from waste catalysts is necessary. The compound dry separator provides a new method for the recycling of waste catalysts with special morphology. The bed surface structure was modified in consideration of the unique properties of spent palladium catalyst in petrochemical industry. The solid-fluid coupling method (DEM-CFD) was used to study the distribution of airflow on the bed surface and the motion characteristics of particle swarm with different combinations of properties. The results showed that the best size of the apertures of bed surface was 2 mm and the optimum installation angle (β) of the lattice bars on bed surface was 50°. The velocity of air flow was small in the backplane region, but relatively large in the region far away from the backplane. And so was the case with dynamic pressure. The dynamic pressure was the largest in the central wind apertures and decreased gradually along the upward direction. The key factor influencing the distribution and movement of the aggregate on the bed surface was the shape of particles, while the effect of density was relatively weak. The separation efficiency (Ef) in numerical simulation was 99.83%, which coincided with the actual experimental result (99.57%).

Enhancements on strength of body structure due to bake hardening effect on hot stamping steel

Body structure projects are designed to develop lightweight structures, which result in low fuel consumption and emissions for internal combustion engines and longer battery life in the case of electric vehicles. The structures need to be lightweight but also strong in order to provide maximum safety to the occupants. These premises have led to the development of special materials such as the hot stamping steels. The most used steel in this process, quenched 22MnB5, also exhibits the bake hardening effect: its yield stress increases after being exposed at temperatures close to 200 °C (typical heat treatment of paint lines in the automotive industry). The aim of this study was to verify the improvement in the mechanical strength of a body structure due to the bake hardening effect to which the hot-stamped steel components were submitted. Samples of annealed 22MnB5 steel were submitted to tensile and chemical analysis. A second group of the same steel was subjected to an additional heat treatment in a laboratory furnace simulating the heating that occurs in the body paint line. Subsequently, the same tests were performed with the samples from the first group. Tensile tests evidenced the increase of 6.5% in the yield stress of the samples that suffered the bake hardening effect. The stress-strain diagram curves were used as the input to the side crash simulation program. The simulations demonstrated that the body structure whose hot-stamped parts were subjected the bake hardening effect had a 2% reduction in side crash intrusion compared to body structure where the parts did not suffer this effect. In the case of the lateral protection bar test, the bake hardening effect provided a 5% increase in the maximum bending load.

Morphodynamics of the Qiantang Estuary, China: Controls of river flood events and tidal bores

The importance of seasonal variations in river discharge on the morphological development of estuaries has been recognized in recent years, yet in situ observations about such variations are rare. Here we report a long-term dataset of bathymetry in the middle reach of the Qiantang Estuary, China, characterized by the presence of a large inner bar. Moreover, a hydrographic survey was carried out in the Yanguan reach where one of the largest tidal bores in the world occurs, covering a spring-neap tidal cycle in 2015. Meanwhile, detailed seasonal bathymetric data together with daily river discharges of 2015 were collected. The bed morphology shows strong seasonal and inter-annual variations. During the high flow season, the river flow erodes the bed and transports a large amount of sediments seaward. A good power-law relationship exists between the high river discharge and the channel volume at the upper estuary. Flood tides dominate under usual river flow condition. In particular, the tidal bore during spring and intermediate tides is characterized by large current velocity and high suspended sediment concentration, and transports a large amount of sediment landward. Over a year, a dynamic morphological equilibrium can be maintained. Moreover, the estuary has also been significantly influenced by the large-scale embankment in recent decades, constraining the lateral thalweg migration, bank erosion and point bar deposition, which usually occur in natural sinuous estuaries.

Muscle activation during fast walking with two types of foot orthoses in participants with cavus feet

The aim of this study was to quantify the effects of foot orthoses (FOs) with and without a lateral bar on muscle activity of participants with cavus feet. Fifteen participants were recruited from the Université du Québec à Trois-Rivières students and podiatry clinic. The muscle activity of the tibialis anterior, fibularis longus, gastrocnemius lateralis and medialis, vastus medialis and lateralis, biceps femoris and gluteus medius were recorded during fast walking under two experimental conditions (FOs with and without a lateral bar) and a control condition (shoes). Experimentations were completed after a one-month adaptation period to each experimental condition. The root mean square of the electromyography (EMG) data was analyzed. To compare the effects between conditions, a curve analysis was performed using one-dimensional statistical parametric mapping. The main result of this study was an increased gastrocnemius lateralis muscle activity (maximum mean difference: +28%) during the propulsion phase of gait (44–46%) when participants wore FOs compared to the control condition. This result will help researchers and clinicians better understand the FOs’ EMG effects of individuals with cavus feet. As FOs are mainly prescribed for symptomatic patients, future studies should assess their effects on individuals suffering of a pathology, such as Achilles tendinopathy.

The effect of material density on load rate sensitivity in nonlinear viscoelastic material models

This work presents the results of a numerical sensitivity analysis of material density on crack propagation in nonlinear viscoelastic softening material models. Two basic material models are analyzed: Maxwell and Kelvin material models, under the loading with changing rate (slow or fast impact loading). The material is discretized as a lattice model, and the analysis is performed on simple examples consisting of several lattice bars. The mathematical description is based on the theory of dynamical systems, i.e., it is a system of nonlinear differential equations for Kelvin, and a system of nonlinear differential-algebraic equations for Maxwell material model. Sensitivity of displacements on mass and load rate accompanies the analysis.

Facemask performance during maxillary protraction: a finite element analysis (FEA) evaluation of load and stress distribution on Delaire facemask

BackgroundTo evaluate load and stress distribution on Delaire facemask (FM) during maxillary protraction in class III growing patients by means of finite element analysis (FEA). A three-dimensional geometry of a Delaire FM was reconstructed from the original CAD 3D prototype, using software package (ANSYS 5.7). FM presented forehead and chin supports and stainless steel framework characterized by two lateral vertical bars connected to a crossbar with two pawls for elastic attachment. Two traction intensities (7.8 and 9.8 N) were applied on the FM pawls along three different downward inclined directions with respect to the occlusal plane (0°, 30°, or 50°, respectively). Resulting stresses and deformations were then tested through the von Mises yield criterion in order to underline the FM wear performance.ResultsThe analysis showed that higher stresses and deformations are mostly related to axial forces of 9.8 N rather than 7.8 N. Stresses also progressively increased with increasing downward force inclinations (0°, 30°, and 50° with respect to the occlusal plane). The overall tensions were inferior to the limit of the elastic behavior (yield point) characterizing the material they are applied on. Thus, the FM structure absorbed the load applied with an elastic deformation of the lateral and horizontal bars.ConclusionsResulting stresses and deformations were directly proportional to protraction load amounts and to increasing downward inclination of forces. In all tested conditions, protraction forces were not able to determine plastic deformation on FM structure compromising its performance and efficiency.

Effect of lateral single bar knee orthoses in correction of genu varum in nutritional rickets

Genu varum (bowlegs) is a common paediatric deformity of knee presenting as physiological variation in growth pattern. Rickets lead to more pathological bowing if occurs during the phase of physiological bowing. Apart from vitamin D restoration orthotic management doesn’t form a part of standard treatment protocol for deformities due to rickets. It is a prospective & interventional randomised comparative study conducted at department of Physical Medicine & Rehabilitation at A.I.I.P.M.R. Mumbai. Patients presenting with clinical features of rickets with bilateral genu varum were screened. Sixty participants were enrolled in the study based on inclusion & exclusion criteria and divided into 2 groups (30 each) by lottery system. Group 1 received Stoss therapy for vitamin D restoration & bilateral lateral single bar knee orthosis. Group 2 received Stoss therapy only. Participants were assessed at initial visit and 2nd, 4th & 6th month after initiation of treatment with biochemical parameters, intercondylar distance (ICD) & radiographic tibio-femoral angle. Statistically significant decrease observed in intercondylar distance & tibio-femoral angle in both groups in subsequent follow-ups. Percentage change in intercondylar distance (58.75 vs. 56.59, P = 0.457) & tibio-femoral angle (right 56.74 vs. 55.49, P = 0.599; left 60.7 vs. 59.38, P = 0.666) at the end of 3rd follow-up on comparing both groups was statistically insignificant. Vitamin D restoration by Stoss therapy can be effectively used in treatment of genu varum in nutritional rickets with or without lateral single bar knee orthoses.

Changing Pattern of Channel Morphology of Alaknanda River in Srinagar Valley (Garhwal Himalaya), India

The Alaknanda River is the most significant parental river of Ganga and forms an 11.5 km long and 2.5 km wide valley, locally known as the Srinagar Valley. The purpose of the present study is to highlight the recent landform changes in the Alaknanda channel course after the Kedarnath disaster, 2013. The Kedarnath flood completely changed the channel morphology of the Alaknanda river. The river changed its course at Srikot, SSB and Sriyantra Tapu with lower terraces being silted by sands at Ranihat, SSB, Bhaktiyana and Sriyantra Tapu. A new depositional terrace also formed opposite to Sriyantra Tapu. New lateral channel bars, braided channels, back swamp, rapids, pools and river souls were identified in the channel course of the river. Shifting of the channel course at Chauras still remains a serious problem for the Garhwal University Chauras Campus. About 2–5 m silt was deposited on the lower terrace at SSB, and ITI. The Srikot river bed was appended to 4.60 m. Shifting of channel course remains a serious threat to the Srinagar valley. Urbanization, sand and boulders mining, construction of dam, hydrological canal, road and settlements are the prominent example of anthropogenic activities which affect the shifting channel.