Erratum to:On the Downshift of Wave Frequency for Bragg Resonance[China Ocean Engineering,2022,36(1),76-85.https://doi.org/10.1007/s13344-022-0006-y]

In the original publication of the article(Peng et al.2022),under the section‘Comparisons with experiments and direct numerical simulations’,Fig.4 was not included.The figure is given below:Reference Peng,J.,Tao.,A.F.,Fan,J.,Zheng,J.H.and Liu,Y.M.,2022.On the downshift of wave frequency for Bragg resonance,China Ocean Engineering,36(1),76-85.

Experimental investigation into the salinity effect on the physicomechanical properties of carbonate saline soil

For engineering structures with saline soil as a filling material,such as channel slope,road subgrade,etc.,the rich soluble salt in the soil is an important potential factor affecting their safety performance.This study examines the Atterberg limits,shear strength,and compressibility of carbonate saline soil samples with different NaHCO3 contents in Northeast China.The mechanism underlying the influence of salt content on soil macroscopic properties was investigated based on a volumetric flask test,a mercury intrusion porosimetry(MIP)test,and a scanning electron microscopic(SEM)test.The results demonstrated that when NaHCO3 contents were lower than the threshold value of 1.5%,the bound water film adsorbed on the surface of clay particles thickened continuously,and correspondingly,the Atterberg limits and plasticity index increased rapidly as the increase of sodium ion content.Meanwhile,the bonding force between particles was weakened,the dispersion of large aggregates was enhanced,and the soil structure became looser.Macroscopically,the compressibility increased and the shear strength(mainly cohesion)decreased by 28.64%.However,when the NaHCO3 content exceeded the threshold value of 1.5%,the salt gradually approached solubility and filled the pores between particles in the form of crystals,resulting in a decrease in soil porosity.The cementation effect generated by salt crystals increased the bonding force between soil particles,leading to a decrease in plasticity index and an improvement in soil mechanical properties.Moreover,this work provides valuable suggestions and theoretical guidance for the scientific utilization of carbonate saline soil in backfill engineering projects.

Contract Mechanism of Water Environment Regulation for Small and Medium Sized Enterprises Based on Optimal Control Theory

The small and scattered enterprise pattern in the county economy has formed numerous sporadic pollution sources, hindering the centralized treatment of the water environment, increasing the cost and difficulty of treatment. How enterprises can make reasonable decisions on their water environment behavior based on the external environment and their own factors is of great significance for scientifically and effectively designing water environment regulation mechanisms. Based on optimal control theory, this study investigates the design of contractual mechanisms for water environmental regulation for small and medium-sized enterprises. The enterprise is regarded as an independent economic entity that can adopt optimal control strategies to maximize its own interests. Based on the participation of multiple subjects including the government, enterprises, and the public, an optimal control strategy model for enterprises under contractual water environmental regulation is constructed using optimal control theory, and a method for calculating the amount of unit pollutant penalties is derived. The water pollutant treatment cost data of a paper company is selected to conduct empirical numerical analysis on the model. The results show that the increase in the probability of government regulation and public participation, as well as the decrease in local government protection for enterprises, can achieve the same regulatory effect while reducing the number of administrative penalties per unit. Finally, the implementation process of contractual water environmental regulation for small and medium-sized enterprises is designed.

Erratum to “Contract Mechanism of Water Environment Regulation for Small and Medium Sized Enterprises Based on Optimal Control Theory” [Journal of Water Resource and Protection Vol.16 No.7 2024]

The original online version of this article (Zhao, S., Gu, H.B., Xue, L.F., Wang, D.S. and Huang, B. (2024) Contract Mechanism of Water Environment Regu-lation for Small and Medium Sized Enterprises Based on Optimal Control Theory. Journal of Water Resource and Protection, 16, 538-556. https://doi.org/10.4236/jwarp.2024.167030) unfortunately contains a mis-take. The second institution is “China Renewable Energy Engineering Insti-tute, Beijing, China”, not “China Renewable Engineering Institute, Beijing, China”.

Recent advances in high slope reinforcement in China: Case studies

This paper reviews a number of engineering technologies and workmanships for addressing the challenging issues concerning possible landslides in large-scale slope reinforcement projects in China.It includes:(1) the multi-point anchored piles with a depth of 64 m in the Jietai Temple rehabilitation project,(2) soil nailing strengthened by driven pipe grouting technique covering an area of530 m × 100 m(length × height) in the Xiluodu hydropower project,(3) the cantilever piles extending vertically from the slope toe to stabilize a 300 m high slope at the Xiaowan hydropower station,(4) a new and simple workmanship for building a pile with cross-sectional area of 20 m × 5 m in the Hongjiadu hydropower station,and(5) comprehensive reinforcement scheme proposed for excavation of a 530 m high slope in Jinping I hydropower station.These new technologies can provide valuable experiences for reinforcement of high slopes of similar projects in China and other regions and countries with similar geological conditions.

Overview of hydro–wind–solar power complementation development in China

1Introduction Hydropower generation in China started over a century ago, greatly contributing to their economic and social development. Wind power and photovoltaic (PV) power generation began on a large scale in the 21st century.

LA-ICP-MS in situ analyses of the pyrites in Dongyang gold deposit,Southeast China:Implications to the gold mineralization

The Dongyang gold deposit is a newly discovered epithermal deposit in Fujian Province,Southeast China,along the Circum-Pacific metallogenic belt.Herewith,the authors present mineralogical,scanning electron microscope,and laser ablation inductively coupled clasma mass spectrometry analysis to reveal the relations between Au and Te,As,S,Fe,etc.,and discuss the gold precipitation process.The pyrites in this deposit are Fe-deficient,and are enriched in Te and As.The authors infer that As was mainly in form of As-complexes,and Te-Au-Ag inclusions/solid solution also exsits in the Py I.Along with the depletion of Te and As,they were less active chemically in the Py II,and Au may be incorporated into As-rich and Fe-deficient surface sites by chemisorption onto As-rich growth surfaces.Because of the incorporation of new fluid,Te and As became the most active chemically in the Py III,which was the main elements precipitation stage,and As dominantly substituted for S in the lattice of pyrite,due to the more reducing condition.The authors propose Au was in form of invisible gold,and the incorporation of gold can be considered as post-pyrite event,while the Au-bearing minerals were result of post incorporation of gold in arsenian pyrite.

Leading-edge technologies in hydropower development in China

After the implementation of the Reform and Opening-up Policy for a period of 40 years, the exploitation of Chin a's hydropower resources developed significa ntly. Through vast amounts of scie ntific and tech no logical research and construction practices, China has accumulated abundant engineering experience with respect to the construction technologies required for 300-meter-high concrete arch dams, 200-meter-high roller-compacted concrete gravity dams, 200-meter-high concrete face rockfill dams, 250?meter?high earth core rockfill dams, large-flow discharge and energy dissipation, huge underground cavern group constructions, complicated foundation treatments for high earth and rockfill dams and high and steep slope reinforceme nts. These series of tech no logies have now reached an inter national leadi ng level. In the near future, these technical improvements will likely have broader application prospects and make greater contributions toward hydropower development both in China and across the world.

Geomorphic effect of debris-flow sediments on the Min River,Wenchuan Earthquake region,western China

Coseismic landslides and subsequent mobilization of sediment greatly aggravated the landscape evolution and river sedimentation after the Wenchuan earthquake.The debris-flow alluvial fan and river morphological index was combined to describe quantitatively the effects of debris-flow sediment on the river characteristics in Longmen Mountains.The section of the Min River from the urban area of the Wenchuan county to the epicenter,the Yingxiu town in this county,was selected as the study area.We identified 27 river-blocking debrisflows(5 partial-,7 semi-,7 over semi-,and 5 fullyblocking degrees)in the study area via remote sensing interpretation and field survey.Based on this,the response of river longitudinal profile and curvature to debris-flow sediment was qualitatively and quantitatively analyzed.The results show that the channel gradient has decreased due to debris-flow aggradation,while two marked peaks in the river steepness index(ksn,represents the relative steepness degree of the channel)changed from 585 m0.9 to 732 m0.9 in zone 1,from 362 m0.9 to 513 m0.9 in zone 2.Moreover,the main channel has undergone substantial lateral migration with channel width decreased and river curvature increased.The temporal and spatial variation between river morphological characteristics and debris-flow sediments in short-term provides insights into the internal dynamic role of mass wasting processes in river morphology,which could be served as useful information for natural hazards management to prevent the river from being blocked by episodically debris flows after the earthquake.

Flume Experiment Investigation on Propagation Characteristics of Tidal Bore in A Curved Channel

Tidal bore is a special and intensive form of flow movement induced by tidal effect in estuary areas, which has complex characteristics of profile, propagation and flow velocity. Although it has been widely studied for the generation mechanism, propagation features and influencing factors, the curved channel will complicate the characteristics of tidal bore propagation, which need further investigation compared with straight channel. In this study, the flume experiments for both undular and breaking bores’ propagation in curved channel are performed to measure the freesurface elevation and flow velocity by ultrasonic sensors and ADV respectively. The propagation characteristics,including tidal bore height, cross-section surface gradient, tidal bore propagation celerity, and flow velocity are obtained for both sides of the curved channel. And three bore intensities are set for each type of tidal bores. The freesurface gradients are consistently enlarged in high-curvature section for undular and breaking bores, but have distinct behaviors in low-curvature section. The spatial distributions of tidal bore propagation celerity and flow velocity are compared between concave and convex banks. This work will provide experimental reference for engineering design of beach and seawall protection, erosion reduction and siltation promotion in estuary areas with the existence of tidal bores.

Study on integrated development and hybrid operation mode of nuclear power plant and pumped-storage power station

The nuclear power plant is suitable for base-load operation, while the pumped-storage unit mainly gives play to capacity benefit in the electric power system;hence, the integrated development and hybrid operation mode of the two can better meet the needs of the electric power system. This article first presents an analysis of the necessity and superiority of such mode, then explains its meaning and analyzes the working routes. Finally, it proposes the business modes as follows: low price pumping water electricity plus nuclear power in the near term;nuclear power shifted to pumped storage power participating in market competition in the middle term;and, in the long term, nuclear power shifted to pumped storage power as primary and serving as an electric power system when needed.

Economic feasibility of large-scale hydro–solar hybrid power including long distance transmission

Solar PV is expected to become the most cost-competitive renewable energy owing to the rapidly decreasing cost of the system. On the other hand, hydropower is a high-quality and reliable regulating power source that can be bundled with solar PV to improve the economic feasibility of long-distance transmitted power. In this paper, a quantification model is established taking into account the regulating capacity of the reservoir, the characteristics of solar generation, and cost of hydro and solar PV with long-distance transmission based on the installed capacity ratio of hydro–solar hybrid power. Results indicate that for hydropower stations with high regulating capacity and generation factor of approximately 0.5, a hydro–solar installed capacity ratio of 1:1 will yield overall optimal economic performance, whereas for hydropower stations with daily regulating capacity reservoir and capacity factor of approximately 0.65, the optimal hydro–solar installed capacity ratio is approximately 1:0.3. In addition, the accuracy of the approach used in this study is verified through operation simulation of a hydro–solar hybrid system including ultra high-voltage direct current(UHVDC) transmission using two case studies in Africa.

On the Downshift of Wave Frequency for Bragg Resonance

For surface gravity waves propagating over a horizontal bottom that consists of a patch of sinusoidal ripples,strong wave reflection occurs under the Bragg resonance condition.The critical wave frequency,at which the peak reflection coefficient is obtained,has been observed in both physical experiments and direct numerical simulations to be downshifted from the well-known theoretical prediction.It has long been speculated that the downshift may be attributed to higher-order rippled bottom and free-surface boundary effects,but the intrinsic mechanism remains unclear.By a regular perturbation analysis,we derive the theoretical solution of frequency downshift due to third-order nonlinear effects of both bottom and free-surface boundaries.It is found that the bottom nonlinearity plays the dominant role in frequency downshift while the free-surface nonlinearity actually causes frequency upshift.The frequency downshift/upshift has a quadratic dependence in the bottom/free-surface steepness.Polychromatic bottom leads to a larger frequency downshift relative to the monochromatic bottom.In addition,direct numerical simulations based on the high-order spectral method are conducted to validate the present theory.The theoretical solution of frequency downshift compares well with the numerical simulations and available experimental data.

Simulation of three-dimensional tension-induced cracks based on cracking potential function-incorporated extended finite element method

In the finite element method,the numerical simulation of three-dimensional crack propagation is relatively rare,and it is often realized by commercial programs.In addition to the geometric complexity,the determination of the cracking direction constitutes a great challenge.In most cases,the local stress state provides the fundamental criterion to judge the presence of cracks and the direction of crack propagation.However,in the case of three-dimensional analysis,the coordination relationship between grid elements due to occurrence of cracks becomes a difficult problem for this method.In this paper,based on the extended finite element method,the stress-related function field is introduced into the calculation domain,and then the boundary value problem of the function is solved.Subsequently,the envelope surface of all propagation directions can be obtained at one time.At last,the possible surface can be selected as the direction of crack development.Based on the aforementioned procedure,such method greatly reduces the programming complexity of tracking the crack propagation.As a suitable method for simulating tension-induced failure,it can simulate multiple cracks simultaneously.

Pixel-level crack segmentation of tunnel lining segments based on an encoder–decoder network

Regular detection and repair for lining cracks are necessary to guarantee the safety and stability of tunnels.The development of computer vision has greatly promoted structural health monitoring.This study proposes a novel encoder–decoder structure,CrackRecNet,for semantic segmentation of lining segment cracks by integrating improved VGG-19 into the U-Net architecture.An image acquisition equipment is designed based on a camera,3-dimensional printing(3DP)bracket and two laser rangefinders.A tunnel concrete structure crack(TCSC)image data set,containing images collected from a double-shield tunnel boring machines(TBM)tunnel in China,was established.Through data preprocessing operations,such as brightness adjustment,pixel resolution adjustment,flipping,splitting and annotation,2880 image samples with pixel resolution of 448×448 were prepared.The model was implemented by Pytorch in PyCharm processed with 4 NVIDIA TITAN V GPUs.In the experiments,the proposed CrackRecNet showed better prediction performance than U-Net,TernausNet,and ResU-Net.This paper also discusses GPU parallel acceleration effect and the crack maximum width quantification.

Contact theory

Contacts between two general blocks are the fundamental problem for discontinuous analysis. There are different contact points in different block positions, and there may have infinite contact point pairs in the same block position. In this paper, a new concept of an entrance block for solving the contacts between two general blocks is introduced. The boundary of an entrance block is a contact cover system. Contact covers may consist of contact vectors, edges, angles or polygons. Each contact cover defines a contact point and all closed-contact points define the movements, rotations and deformations of all blocks as in real cases. Given a reference point, the concept of entrance block simplifies the contact computation in the following ways.(1) The shortest distance between two blocks can be computed by the shortest distance between the reference point and the surface of the entrance block.(2) As the reference point outside the entrance block moves onto the surface of entrance block, the first entrance takes place. This first entrance point on the entrance block surface defines the contact points and related contact locations.(3) If the reference point is already inside the entrance block, it will exit the entrance block along the shortest path. The corresponding shortest exit point on the entrance block surface defines the contact points and related contact locations. All blocks and angles here are defined by inequality equations. Algebraic operations on blocks and angles are described here. Since the blocks and angles are point sets with infinite points, the geometric computations are difficult, and therefore the geometric computations are performed by related algebraic operations.

Cascading dam breach process simulation using a coupled modeling platform

This study evaluates the possibility of a cascade failure by developing a coupled breach-modeling platform based on onedimensional flow modeling of the river channel, flood propagation, regulation process of reservoir fluctuation, overtopping with breaching, and wave damping downstream. A hyperbolic model of the DB-IWHR was embedded into the platform to simulate the dam breaching process. Five breach models and software were used to calculate the Tangjiashan barrier lake breaching. The results of a sensitivity study were then compared with the measured data. The peak flow and the time of occurrence were confirmed to be predictable with a reasonable accuracy if the input values were within ranges appropriate for the model. The approach was applied to a case involving two layout planning schemes for a cascade of rock-filled dams under extreme operating conditions. The probability of the failure of a key control cascade downstream caused by a continuous cascade breach upstream was simulated. Moreover, measures to prevent the transmission of risk by advance warnings were investigated. The proposed methodology and the discharge capacity measures provide guidelines to assess the risk to a cascade of dams under extreme operating conditions and offer support for the design criteria of unusual discharge structures for very large dams.

Study of risk acceptance criteria for dams

This paper discusses the methods of establishing risk criteria for dams and reviews the application of dam risk criteria for individuals and societies in different countries or districts. Given the conditions in China and considering the public safety and acceptance of dam risk, historical dam break data and current design standards, individual and societal risk criteria for dams are proposed. The tolerable dam risk criteria for individuals should be set to 10-5-10-7 per annum based on project scale, for ex- ample, approximately 1.0xl0 7 per annum, which corresponds to a reliability index of 4.2 based on a 100-year lifespan for a first-class or large project. The societal limit for risk tolerance for dams should be set to approximately 10-3-10-5 per annum, corresponding to the fatality range from 1 to 100 and be horizontally extended to 1000, and F-N curves are proposed. It was also found that the reliability indices of Chinese Standard （GB 50199-2013） and Eurocodel （2002） are different, but they have the same level of safety measured by the annual probability of failure. The research results have significance for establishing dam risk criteria.