Unsteady Characteristics of Sediment Transport Under Non-harmonic Waves

AbstractSediment transport under waves is one of the key dynamic processes of coastal sediment motion. Previous studies for this issue are mainly based on linear wave theory and quasi-steady simplification. However, waves in real circumstance are always irregular, generally with a certain degree of asymmetry and/or velocity-leaning especially in shallow water. It is envisaged that sediment movement under non-harmonic waves is different from sinusoidal waves. Based on large eddy simulation of turbulent flows in wave boundary layer, a modified method is proposed to calculate sediment transport rate under non-harmonic waves. It is further used to explore the influences of flow acceleration and the phase lead between the free stream velocity and bed shear stress on sediment transport rate in different phases of one wave cycle for forth-leaning. The net transport rate is found to increase with the degree of asymmetry and velocity-leaning index. Both the acceleration and the phase lead have a great influence on average transport rate in each phase

Experiment Study on Local Scouring Depth around Pile Permeable Spur Dikes

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Experimental Study on the Characteristics of Three-Dimensional Flow Structures with Changing Condition in Bifurcation Area

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Experimental Investigation on the Vertical Distribution of Cohesive Sediment Concentration in Weak Dynamical Flow

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Investigation of Flocculation Characteristics in the Yangtze Estuary

The dynamic process of flocculation is crucial for the transport and fate of cohesive sediment and adherent nutrients, heavy metals and pollutants etc. In order to improve the understanding of sediment flocculation dynamics in the estuary, field surveys in the Yangtze Estuary and laboratory experiments with natural mixed sediment were conducted. In-situ observations showed that the mean floc diameters (DM) ranged from 14 to 95 μm, and there were significant temporal and vertical fluctuations within a tidal cycle and between spring-neap cycles. Both high and low slack waters had greater DM, and neap tide’s average floc size was determined to be 57% larger than spring tide. The fractal dimension of flocs in the YE was primarily between 1.5 and 2.1, and effective density of flocs declined as floc size increased. According to experimental findings, DM in the 7 PSU saltwater first increased with rising shear rate G below a threshold of G = 20–30 s−1, then decreased with additional increases in G. Turbulent shear rate plays a crucial role in altering floc structure. Flocs formed in large shear forces were more compacted and had higher fractal dimensions. These studies contribute to the understanding of fine sediment dynamics, and facilitate the researches on reservoir, port and waterway sedimentation and pollutant transportation etc

Influence of turbid flood water release on sediment deposition and phosphorus distribution in the bed sediment of the Three Gorges Reservoir, China

Excessive phosphorus (P) loading was identified as an urgent problem during the post-Three Gorges Reservoir (TGR) period. Turbid water with high suspended sediment loads has been periodically released during the flood season to mitigate sediment deposition in the TGR, but limited attention has been paid to its effect on the distribution of P in bed sediment within the reservoir. In this study, field surveys, historical monitoring data related to sediment deposition, and physiochemical properties and the fractional P content in the mainstream surface sediment and representative column sediment, were used to investigate the effect of turbid flood water release on P distribution in bed sediment. The results revealed that turbid flood water release could discharge approximately 20% of the suspended sediment inflow entering the TGR. Additionally, both the particle size of the inflow sediment and suspended sediment flux tended to decline, and the deposited sediment volume tended to constantly increase in the TGR at a rate of 0.117 billion tonnes per year between 2004 and 2016. The median particle size (MPS) was larger for surface sediment obtained in the flood season than for that obtained in the dry season, and the MPS tended to increase with an increase in the sediment depth from 0 to 20 cm. The total phosphorus (TP) content in sediment ranged from 2.6% to 17.5% lower in the flood water releasing period than in the non-flood water storing period. However, no consistent variation was detected for the vertical distribution of P fraction in the top 20 cm of bed sediment. Compared with lakes with slow deposition rates, the TGR showed a rapid sedimentation rate of >1.0 m/y, which mostly resulted in the uniform distribution of the surface sediment P fraction

Highly stretchable conductor inspired by compliant mechanism

Flexible and stretchable conductors have invaluable applications in multiple domains, such as sensors, displays, and electronic skins. The stable conductance exhibited by conductors when subjected to diverse forms of deformation, such as tensile stress, curvature, or torsion, represents a fundamental characteristic. Attaining high conductivity and stretchability simultaneously in conductive materials is a formidable challenge, owing to inherent constraints in materials found in nature. To overcome this problem, an innovative approach of structurally designing conductors using existing materials to achieve high deformability and stretchability, i.e. stretchable conductors inspired by a compliant mechanism is proposed in this paper. Thus, a novel stretchable conductor inspired by flexible mechanisms is introduced. Unlike stretchable conductors based on Kirigami structures, the stretchable conductor based on flexible mechanisms can achieve large in‐plane deformation within the material's strength limit. The concept and design process of the highly deformable stretchable conductor inspired by flexible mechanisms are presented in this paper. Experimental results show that the resistance change ratio of the conductor remains within 0.05% during the 0–200% strain process. The consistency and durability of the conductor during stretching deformation are also confirmed through 500 repetitions of the test. Additionally, the experiments with the electric motor and light‐emitting diode (LED) light confirm the conductor's ability to maintain a stable current

Omecamtiv mecarbil in chronic heart failure with reduced ejection fraction, GALACTIC‐HF: baseline characteristics and comparison with contemporary clinical trials

Aims: The safety and efficacy of the novel selective cardiac myosin activator, omecamtiv mecarbil, in patients with heart failure with reduced ejection fraction (HFrEF) is tested in the Global Approach to Lowering Adverse Cardiac outcomes Through Improving Contractility in Heart Failure (GALACTIC‐HF) trial. Here we describe the baseline characteristics of participants in GALACTIC‐HF and how these compare with other contemporary trials. Methods and Results: Adults with established HFrEF, New York Heart Association functional class (NYHA) ≥ II, EF ≤35%, elevated natriuretic peptides and either current hospitalization for HF or history of hospitalization/ emergency department visit for HF within a year were randomized to either placebo or omecamtiv mecarbil (pharmacokinetic‐guided dosing: 25, 37.5 or 50 mg bid). 8256 patients [male (79%), non‐white (22%), mean age 65 years] were enrolled with a mean EF 27%, ischemic etiology in 54%, NYHA II 53% and III/IV 47%, and median NT‐proBNP 1971 pg/mL. HF therapies at baseline were among the most effectively employed in contemporary HF trials. GALACTIC‐HF randomized patients representative of recent HF registries and trials with substantial numbers of patients also having characteristics understudied in previous trials including more from North America (n = 1386), enrolled as inpatients (n = 2084), systolic blood pressure < 100 mmHg (n = 1127), estimated glomerular filtration rate < 30 mL/min/1.73 m2 (n = 528), and treated with sacubitril‐valsartan at baseline (n = 1594). Conclusions: GALACTIC‐HF enrolled a well‐treated, high‐risk population from both inpatient and outpatient settings, which will provide a definitive evaluation of the efficacy and safety of this novel therapy, as well as informing its potential future implementation

Editorial: Dams and wetland biodiversity: Impacts and mitigating measures

To meet energy, water and transportation needs, an incredible amount of dams have been constructed around the world. For example, only in the Yangtze River's watershed of China, over 50,000 dams were built since 1950 (Nilsson et al., 2005; Wu et al., 2019). Dams could contribute to energy and water supply, and flood protection, but they also affect aquatic ecosystems by alteration of hydrologic regime and fragmentation (Barbarossa et al., 2020). While about 50% of the river around the world is currently changed by dam, this percentage is expected to increase to 93% because of the pending construction of about 3,700 major hydropower dams (Grill et al., 2015).To meet energy, water and transportation needs, an incredible amount of dams have been constructed around the world. For example, only in the Yangtze River's watershed of China, over 50,000 dams were built since 1950 (Nilsson et al., 2005; Wu et al., 2019). Dams could contribute to energy and water supply, and flood protection, but they also affect aquatic ecosystems by alteration of hydrologic regime and fragmentation (Barbarossa et al., 2020). While about 50% of the river around the world is currently changed by dam, this percentage is expected to increase to 93% because of the pending construction of about 3,700 major hydropower dams (Grill et al., 2015).HW was financially supported by the Natural Science Foundation of Hunan Province (2021JJ40601) and the Scientific Research Foundation of Hunan Provincial Education Department (20B005).HW was financially supported by the Natural Science Foundation of Hunan Province (2021JJ40601) and the Scientific Research Foundation of Hunan Provincial Education Department (20B005)

General suzuki coupling of heteroaryl bromides by using Tri-tert-butylphosphine as a supporting ligand

A general procedure for the fast Suzuki coupling of major families of heteroaryl bromides was realized by using Pd(OAc)2/PtBu3 as the catalyst. Many couplings were finished within minutes at room temperature in n-butanol. Different from previous studies, three typical heteroaryl bromides were systematically examined in couplings of various heteroaryl and aryl boronic acids