Search

As a prerequisite and foundation for studying the evolution mechanism of river channels, an in-depth understanding of the cross-sectional morphology adjustment is required. As a starting point, it is crucial to systematically summarize and generalize the research findings on channel morphological adjustment obtained to date, particularly in the context of the significant changes in the water and sediment conditions of large rivers that have occurred worldwide. This paper provides a comprehensive review of the research findings on the three following aspects of the Lower Yellow River: the transverse distribution of overbank flow velocity, the transverse distribution of suspended sediment concentration, and the morphological adjustment of the river cross-section. There are various equations available to predict the lateral depth–average flow velocity distribution. These equations are classified into the two following categories: empirical and theoretical formulas. Theoretical formulas are obtained through consideration of the cross-sectional morphology, accounting for inertial force terms caused by secondary flow, and momentum transfer between the main channel and its floodplain. Similarly, empirical equations and theoretical formulas for sediment concentration transverse distribution are also summarized, given the different influencing factors and assumptions. We also discuss the morphological adjustment of river cross-sections based on the analysis of measured data, mathematical model calculation, and the physical model test. In particular, we propose the idea of revealing channel cross-section morphology evolution mechanisms from the theoretical level of water and sediment movement and distribution. This review aims to enhance understanding of overbank flow, sediment transport, and channel morphology in the Lower Yellow River and may also serve to some extent as a reference for the evolution and management of channels in other rivers. [ABSTRACT FROM AUTHOR]

As a prerequisite and foundation for studying the evolution mechanism of river channels, an in-depth understanding of the cross-sectional morphology adjustment is required. As a starting point, it is crucial to systematically summarize and generalize the research findings on channel morphological adjustment obtained to date, particularly in the context of the significant changes in the water and sediment conditions of large rivers that have occurred worldwide. This paper provides a comprehensive review of the research findings on the three following aspects of the Lower Yellow River: the transverse distribution of overbank flow velocity, the transverse distribution of suspended sediment concentration, and the morphological adjustment of the river cross-section. There are various equations available to predict the lateral depth–average flow velocity distribution. These equations are classified into the two following categories: empirical and theoretical formulas. Theoretical formulas are obtained through consideration of the cross-sectional morphology, accounting for inertial force terms caused by secondary flow, and momentum transfer between the main channel and its floodplain. Similarly, empirical equations and theoretical formulas for sediment concentration transverse distribution are also summarized, given the different influencing factors and assumptions. We also discuss the morphological adjustment of river cross-sections based on the analysis of measured data, mathematical model calculation, and the physical model test. In particular, we propose the idea of revealing channel cross-section morphology evolution mechanisms from the theoretical level of water and sediment movement and distribution. This review aims to enhance understanding of overbank flow, sediment transport, and channel morphology in the Lower Yellow River and may also serve to some extent as a reference for the evolution and management of channels in other rivers.

Copyright of China Rural Water & Hydropower is the property of China Rural Water & Hydropower Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Plant root growth is inhibited markedly by aluminium (Al) even at micromolar concentration and Al is mainly accumulated in plant roots outer layer cell walls. But the underlying reason for this asymmetric transverse distribution is unknown. In this study, two wheat (Triticum aestivum L.) genotypes ET8 and ES8 differing in Al resistance were investigated by hydroculture. The Al-tolerant ET8 expressed a higher root elongation rate (RER) than Al-sensitive ES8 under Al stress. Morphological examination showed symptoms such as root surface ruptures were observed in ET8 and ES8, with ES8 being more obvious. The cation exchange capacity (CEC) values of root tips of ES8 under different Al concentrations are higher than those of ET8. The sensitive genotype ES8 accumulated more Al than ET8 in plant apical root tips as well as cell walls. Under 48 h Al exposure, the root cell wall pectin concentration was increased with a higher magnitude in ES8 than in ET8. The functional groups on ET8 and ES8 roots outer layer and inner cells were investigated by Fourier transform infrared spectrometry (FTIR) under Al stress. The FTIR spectra of selected examined areas showed that the characteristic absorption peaks were located at 1692, 2920, and 3380 cm−1. The outer layer cells had stronger peaks than inner cells at wavenumber 1680–1740 cm−1, indicating root outer layer cells contain more carboxyls in both ET8 and ES8. The results demonstrate that Al transverse distribution on plants apical root cross section is likely influenced by functional groups such as negatively charged carboxylic acid.

The worn-out nozzles of field sprayers cause agricultural treatment to be uneven and therefore ineffective. Spray nozzles are consumable elements of the field sprayer that are subject to inspection and in the event of their excessive wear should be replaced with new ones to ensure the proper execution of agricultural treatment. The aim of the study is to propose, using operational research methods, an expert methodology allowing further operation of worn-out and often expensive sprayer nozzles, including standard, universal, anti-drift, or ejector nozzles. The previous attempts, performed with the use of the random computer optimisation method, did not guarantee a global solution in the entire population of all possible permutations without repetitions of 24 worn-out nozzles (for a field boom with a width of 12 m) or even estimating approximation to this solution. The process of measuring the wear of nozzles, the simulation of the entire virtual field boom, and the permutation algorithm proposed here allow you to specify a suboptimal solution of an NP-hard problem separately for each sprayer, i.e., to indicate in a very short time such a permutation out of 24! ≈ 6.20448 × 10+23 permutations of nozzles with variable degrees of wear, which is close to the optimal permutation of used nozzles on the field sprayer boom, in terms of the coefficient of variation. The use of expert methodology allows for reducing the operating costs of sprayers by using a relatively cheap automated expert service instead of the costly purchase of a set of new nozzles for field sprayers. Many areas of application of this methodology have been indicated. [ABSTRACT FROM AUTHOR]

The construction of a river regulation project has changed the cross-sectional shape of a river and significantly impacted the evolution of the river regime. In this paper, an asymmetry index was proposed to characterize the changes in the shape of the river cross-section and the distribution of water and sediment factors. According to the transverse distribution formula of the river section and water and sediment factors, the asymmetry of the cross-sectional shape as well as water and sediment factors along with the transverse distribution in the wandering reach of the lower Yellow River before and after the construction project was calculated, respectively. The results showed that the cross-sectional shape of the river channel before and after the building was asymmetric, and the cross-sectional shape of the river channel after the construction was more asymmetric than that of the free development channel without engineering constraints; at the same time, under the action of a limited control boundary, the asymmetry of cross-section flow velocity and sediment concentration and other water and sediment factors along the transverse distribution were more prominent, the flow velocity and sediment concentration along the transverse distribution increased, the river flow was more concentrated, and the sediment transport capacity of the channel improved significantly under a large flow (5000 m3/s). This study revealed the positive effect of river regulation projects on the river regime evolution of the wandering river and provided new ideas for the study of river regime evolution. [ABSTRACT FROM AUTHOR]

A series of simulations with different heat release rates (HRRs) are conducted in a full-scale horseshoe-shaped tunnel model. Thermocouples are arranged in 21 cross-sections of the tunnel to obtain entire temperature field. The prediction formulas of the ceiling maximum temperature and the longitudinal temperature attenuation beneath the ceiling are obtained, which are consistent with the model of Albert and Gong. It is found that the dimensionless transverse temperature rise distribution under the semicircular ceiling conforms to the Boltzmann curve, but the coefficients of the fitting formula are different for the near field zone and the far field zone. Transverse temperature distribution in the sidewall part can be regarded as constant, which is equal to the temperature at the bottom of semicircular ceiling in most engineering applications. A prediction model is established to estimate the temperature of each position of tunnel structure. It provides a more accurate and detailed temperature field prediction method for tunnel fire prevention and structural damage research.

Copyright of Atatürk University Journal of Agricultural Faculty is the property of Ataturk University Coordinatorship of Scientific Journals and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The construction of a river regulation project has changed the cross-sectional shape of a river and significantly impacted the evolution of the river regime. In this paper, an asymmetry index was proposed to characterize the changes in the shape of the river cross-section and the distribution of water and sediment factors. According to the transverse distribution formula of the river section and water and sediment factors, the asymmetry of the cross-sectional shape as well as water and sediment factors along with the transverse distribution in the wandering reach of the lower Yellow River before and after the construction project was calculated, respectively. The results showed that the cross-sectional shape of the river channel before and after the building was asymmetric, and the cross-sectional shape of the river channel after the construction was more asymmetric than that of the free development channel without engineering constraints; at the same time, under the action of a limited control boundary, the asymmetry of cross-section flow velocity and sediment concentration and other water and sediment factors along the transverse distribution were more prominent, the flow velocity and sediment concentration along the transverse distribution increased, the river flow was more concentrated, and the sediment transport capacity of the channel improved significantly under a large flow (5000 m3/s). This study revealed the positive effect of river regulation projects on the river regime evolution of the wandering river and provided new ideas for the study of river regime evolution.

The worn-out nozzles of field sprayers cause agricultural treatment to be uneven and therefore ineffective. Spray nozzles are consumable elements of the field sprayer that are subject to inspection and in the event of their excessive wear should be replaced with new ones to ensure the proper execution of agricultural treatment. The aim of the study is to propose, using operational research methods, an expert methodology allowing further operation of worn-out and often expensive sprayer nozzles, including standard, universal, anti-drift, or ejector nozzles. The previous attempts, performed with the use of the random computer optimisation method, did not guarantee a global solution in the entire population of all possible permutations without repetitions of 24 worn-out nozzles (for a field boom with a width of 12 m) or even estimating approximation to this solution. The process of measuring the wear of nozzles, the simulation of the entire virtual field boom, and the permutation algorithm proposed here allow you to specify a suboptimal solution of an NP-hard problem separately for each sprayer, i.e., to indicate in a very short time such a permutation out of 24! ≈ 6.20448 × 10+23 permutations of nozzles with variable degrees of wear, which is close to the optimal permutation of used nozzles on the field sprayer boom, in terms of the coefficient of variation. The use of expert methodology allows for reducing the operating costs of sprayers by using a relatively cheap automated expert service instead of the costly purchase of a set of new nozzles for field sprayers. Many areas of application of this methodology have been indicated.

The sediment-laden floodplain flood is affected by beach vegetation and the shape of curved compound channels. The laws of water and sediment exchange and deposition distribution in beach troughs are very complex and play a significant role in the formation and development of secondary suspended rivers, the adjustment of beach horizontal gradients, and even the evolution of flood control situations. This study used a combination of experimental simulations and theoretical research to carry out a generalized model test of floodplain flood evolution, analyzing the transverse distribution characteristics of sediment-laden flow and sediment factors in a curved compound channel under the conditions of beach vegetation, proposing a theoretical model of transverse distribution of velocity and sediment concentration that is based on the momentum equation considering the inertial force of the lateral secondary flow and river curvature. The results showed the following: (1) The model test results for floodplain flood in the compound channel with curved vegetation showed that the main stream was not only concentrated in the main channel but also appeared near the foot of the left and right bank levees and formed flood discharge along the embankment, as the beach siltation was mainly concentrated in the beach lip; (2) The arrangement of full vegetation on the beach had a uniform effect on the velocity distribution of the beach, which can reduce the phenomenon of excessive velocity at the foot of the beach and increase the velocity effect in the main channel; and (3) Through five numerical examples, the lateral velocity distribution model of a curved compound channel with beach vegetation was tested and, in general, the analysis model was consistent with the experimental results. The research results will provide a theoretical basis for river management and have great significance for enriching the basic theory of water and sediment movement and promoting the integration of hydraulics, river dynamics, and ecology.

• In multi-joist TCCs, transverse distribution of midspan moments differs strongly from that of support reactions. • Novel instrumentation used to back-calculate midspan moment sharing from tests. • Expanded steel mesh plate showed good stiffness and ductility as a shear connector. The critical T-sections of multi-joist timber-concrete composite (TCC) floors must be designed at ultimate for support shear force and midspan moment, both of which are influenced by transverse sharing, but to different extents. Prior experimental work has investigated only support reaction sharing and only up to serviceability loads. The present experimental study builds on that status quo by quantifying also moment sharing, via strain gauge layouts at quarter-span and midspan, along with reaction sharing via load cells at the supports of a multi-joist TCC specimen, over the entire load range up to failure. Use of steel mesh connectors bonded into hardwood laminated veneer lumber joists, and near geometric resemblance to a real building TCC floor recently built in London, were novel features of the specimen. The results show that midspan moment and reaction sharing both vary nonlinearly with load, but in distinctly different ways from each other (with up to almost 20% difference observed between them), in the progression between the uncracked, cracked and connection ductility regimes. In this approach reliable assessment of moment sharing depends on the quality of the recorded strains. Accordingly, the strain data were shown to be of high quality by converting these data to internal stress resultants that were then found to satisfy longitudinal equilibrium. It is concluded that this strain gauge layout is useful for future work aimed at building a database of transverse sharing of moments in TCCs. [ABSTRACT FROM AUTHOR]

Copyright of China Pulp & Paper is the property of China Pulp & Paper Magazines Publisher and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Plant root growth is inhibited markedly by aluminium (Al) even at micromolar concentration and Al is mainly accumulated in plant roots outer layer cell walls. But the underlying reason for this asymmetric transverse distribution is unknown. In this study, two wheat (Triticum aestivum L.) genotypes ET8 and ES8 differing in Al resistance were investigated by hydroculture. The Al-tolerant ET8 expressed a higher root elongation rate (RER) than Al-sensitive ES8 under Al stress. Morphological examination showed symptoms such as root surface ruptures were observed in ET8 and ES8, with ES8 being more obvious. The cation exchange capacity (CEC) values of root tips of ES8 under different Al concentrations are higher than those of ET8. The sensitive genotype ES8 accumulated more Al than ET8 in plant apical root tips as well as cell walls. Under 48 h Al exposure, the root cell wall pectin concentration was increased with a higher magnitude in ES8 than in ET8. The functional groups on ET8 and ES8 roots outer layer and inner cells were investigated by Fourier transform infrared spectrometry (FTIR) under Al stress. The FTIR spectra of selected examined areas showed that the characteristic absorption peaks were located at 1692, 2920, and 3380 cm−1. The outer layer cells had stronger peaks than inner cells at wavenumber 1680–1740 cm−1, indicating root outer layer cells contain more carboxyls in both ET8 and ES8. The results demonstrate that Al transverse distribution on plants apical root cross section is likely influenced by functional groups such as negatively charged carboxylic acid. [Display omitted] • Al tolerant wheat genotype ET8 had a lower CEC than its Al-sensitive counterpart ES8. • Al was mainly accumulated in root cell walls for both genotypes. • Pectin concentrations of both genotypes were increased with different magnitudes. • More negative charged functional groups were at root outer layer cells surface. • Different number of functional groups is responsible for Al asymmetric distribution. [ABSTRACT FROM AUTHOR]

River ice often forms in the cold regions of northern hemisphere which can lead to ice jams (or ice dams). Water level can be significantly raised due to ice jams. As a consequence, disastrous ice flooding may be resulted, such as the ice jam flooding in the Nechako River in Prince George in winter 2007-2008. In the present study, the equations describing the ice jam thickness in the transverse direction are derived. The impact of the secondary vortex is considered while the cohesive force within ice cubes is neglected in the model. The relationship between the parameter β and the total water depth is established based on the assumption that all other variables except the velocities are kept constant on the same cross section. By using the parameter β and the developed equations, the ice jam thickness in the transverse direction can be predicted. The developed model is used to simulate the ice jam thickness in the transverse direction at the Hequ Reach of the Yellow River in China. The simulated ice jam thicknesses agree well with the field measurements on different cross sections. [ABSTRACT FROM AUTHOR]

Numerical analysis is presented for the characteristic parameters of centered-inclined coupling slot in rectangular waveguides, taking into account the transverse distribution of the electric field across the slot aperture. Integral equations are formulated based on dyadic Green's function theories and solved using the method of moments. Trigonometric basis functions are adopted. It is found that the method will converge with up to ten basis functions. The characteristic parameters can be easily obtained for different slot sizes. Resonant length and resonant resistance of the coupling slots are calculated. It is shown that the calculated results have very high accuracy, compared with simulated results obtained from commercial software. Therefore, it can be effectively applied in the synthesis of antenna arrays. Effects of the transverse distribution on calculating resonant parameters of the coupling slot are also analyzed. The results show that if the transverse distribution of the electric field is neglected, the calculated error tends to become larger when the slot gets wider or thinner. [ABSTRACT FROM AUTHOR]

Abstract: The axial and transverse solid distribution of a cohesive powder in flighted rotary kilns was calculated from an original method based on the lifter discharge law previously determined, geometrical calculations and supplementary measurements (in particular the fall velocity of the powder at high temperature). At a given axial position, the quantity of powder falling through the gas, the total quantity of flighted powder as well as the quantity remaining in the bulk are thus calculated; the axial bed depth profile is obtained from the Saeman–Kramers–Afacan model. [Copyright &y& Elsevier]

• Dynamic response signals showed relatively larger magnitudes in saturated condition than those in dry condition. • Pore water pressure was sensitive to vehicle speed compared with vehicle load. • Vehicle wheels of front and rear axles generated pore water pressure with obvious different magnitudes. • Tread pattern of vehicle wheel would affect the transverse distribution of dynamic pore water pressure. • Prediction model of positive pore water pressure taken both vehicle load and speed into account was proposed. Asphalt pavement exhibits different dynamic responses to vehicle loading in saturated conditions and in dry conditions. It is essential to directly conduct field full-scale tests to systematically investigate comprehensive influence of water on dynamic response of asphalt pavement. However, real vehicles which were often applied in field tests might result in a certain deviation in dynamic responses measured from each field loading test due to the inevitable influence of the driver's subjective operation and the tread pattern on vehicle wheel. This study adopted the full-scale accelerated loading test system to comprehensively characterize dynamic response of asphalt pavement in both dry and saturated conditions based on the strict control of loading vehicle's path. The results indicated that dynamic responses showed relatively larger magnitudes in saturated condition than those in dry condition. Strain and stress respectively showed slowly increasing and decreasing trends with the increase of vehicle load and speed correspondingly. Pore water pressure was apparently sensitive to vehicle speed compared with vehicle load. Pore water pressure generated by the front axle wheels showed obviously larger magnitudes than those produced by the rear axle wheels due to the change in thickness of surface runoff. The transverse distribution of pore water pressure obtained from both field tests and numerical simulation exhibited consistent variation trends. Decline degree of pore water pressure magnitudes was obtained at 86.1% for the two adjacent testing points with a distance of 100 mm under the vehicle wheel, which proved the great influence of the tread pattern of vehicle wheel on the transverse distribution of dynamic pore water pressure. A prediction model of positive pore water pressure that considered vehicle load and speed was proposed. [ABSTRACT FROM AUTHOR]

• Multi-joist timber-concrete composites of various connection layouts were tested to failure. • Both moment and reaction sharing were inferred across the full loading range. • Cracking transformed support reaction sharing by a factor of up to 1.60. • Connection yield transformed bending moment sharing by a factor of up to 1.62. • Nonlinear FE models reliably predict load response and help elucidate TCC mechanics. This paper uses tests backed up by nonlinear FE analysis for parametric study of transverse load sharing in large-scale timber-concrete composite (TCC) specimens, each comprising multiple hardwood LVL joists fastened to a single concrete slab via bonded-in, ductile steel mesh connectors. The study for the first time compares midspan moment sharing with support reaction sharing across the full range of behaviour up to failure for two distinct connection layouts, and it highlights the relative influences of connector yield and concrete cracking on the nonlinear load sharing characteristics. For the specific examples of this study, the results show that while cracking had little effect on transverse distribution of midspan moments, it did change the transverse distribution of support reactions by a factor of up to 1.60. Conversely, connection yield had little effect on transverse support reaction distribution, but it changed the transverse distribution of midspan moments by a factor of up to 1.62. Further, the test-verified FE analyses revealed that an inadvertent 20% drop in concrete tensile strength observed in the tests exacerbated support reaction sharing by up to 12.5%. These numbers approach or exceed the safety factors used in design. Wider studies are needed to determine practical bounds for these load sharing effects and to develop user-friendly means of allowing for these effects in design. [ABSTRACT FROM AUTHOR]

The sediment-laden floodplain flood is affected by beach vegetation and the shape of curved compound channels. The laws of water and sediment exchange and deposition distribution in beach troughs are very complex and play a significant role in the formation and development of secondary suspended rivers, the adjustment of beach horizontal gradients, and even the evolution of flood control situations. This study used a combination of experimental simulations and theoretical research to carry out a generalized model test of floodplain flood evolution, analyzing the transverse distribution characteristics of sediment-laden flow and sediment factors in a curved compound channel under the conditions of beach vegetation, proposing a theoretical model of transverse distribution of velocity and sediment concentration that is based on the momentum equation considering the inertial force of the lateral secondary flow and river curvature. The results showed the following: (1) The model test results for floodplain flood in the compound channel with curved vegetation showed that the main stream was not only concentrated in the main channel but also appeared near the foot of the left and right bank levees and formed flood discharge along the embankment, as the beach siltation was mainly concentrated in the beach lip; (2) The arrangement of full vegetation on the beach had a uniform effect on the velocity distribution of the beach, which can reduce the phenomenon of excessive velocity at the foot of the beach and increase the velocity effect in the main channel; and (3) Through five numerical examples, the lateral velocity distribution model of a curved compound channel with beach vegetation was tested and, in general, the analysis model was consistent with the experimental results. The research results will provide a theoretical basis for river management and have great significance for enriching the basic theory of water and sediment movement and promoting the integration of hydraulics, river dynamics, and ecology. [ABSTRACT FROM AUTHOR]

A nomenclature for the organization of biological membranes is proposed. The terms primary (composition), secondary (transverse and lateral distribution), tertiary (membrane stacking/unstacking), and quaternary (membrane-membrane- cell-cell interactions) levels of organization are used by analogy with protein structure, but at each level the membrane organization is more complex and dynamic than protein structure. - [ABSTRACT FROM AUTHOR]

• Standing and jumping tests on building TCC floor with partially prefab connections. • Recorded strains reveal neutral axes consistent with outstanding composite action. • High moment sharing between adjacent TCC T-sections when load along one joist. • Dynamic amplification factors up to 2.38 observed for moments under floor loads. • Grillage analysis & test data show moment sharing influenced by span end restraint. Timber-concrete composites (TCCs) are structurally efficient, low carbon floor systems that can be prefabricated to accelerate in-situ construction. The timber-concrete connectors and their immediately surrounding volumes of concrete together perform important orthogonal structural functions. Longitudinally, they enable slab - joist composite action, thereby improving vertical distribution of bending stresses within each TCC T-section. Transversely, they enable continuity of the slab across the joists, thereby influencing transverse distribution of moments in the TCC. This paper reports field tests to characterise such orthogonal action. Human static and dynamic loads were applied, within the timber-framed Kantor Centre of Excellence building in London, to the newly constructed TCC floor comprising precast concrete planks fastened via partially prefabricated connections to multiple beech LVL joists. Strains recorded from multiple levels on the joists indicate TCC neutral axis heights consistent with almost full composite action, implying excellent vertical distribution capability. Back-calculations from these strains show significant transverse distribution of midspan moments, with 64% and 14% of the loaded T-section's moment developing at one and two T-sections away respectively. The test results further reveal dynamic amplification factors up to 2.38 on peak moments. Moreover, the test results linked to grillage analyses suggest that transverse distribution of midspan moments may be influenced by partial restraint at the supports. It is concluded that the partially prefabricated connections possess excellent orthogonal distribution characteristics. [ABSTRACT FROM AUTHOR]