Deformation prediction model of concrete face rockfill dams based on an improved random forest model

The unique structure and complex deformation characteristics of concrete face rockfill dams(CFRDs)create safety monitoring challenges.This study developed an improved random forest(IRF)model for dam health monitoring modeling by replacing the decision tree in the random forest(RF)model with a novel M5'model tree algorithm.The factors affecting dam deformation were preliminarily selected using the statistical model,and the grey relational degree theory was utilized to reduce the dimensions of model input variables.Finally,a deformation prediction model of CFRDs was established using the IRF model.The ten-fold cross-validation method was used to quantitatively analyze the parameters affecting the IRF algorithm.The performance of the established model was verified using data from three specific measurement points on the Jishixia dam and compared with other dam deformation prediction models.At point ES-10,the performance evaluation indices of the IRF model were superior to those of the M5'model tree and RF models and the classical support vector regression(SVR)and back propagation(BP)neural network models,indicating the satisfactory performance of the IRF model.The IRF model also outperformed the SVR and BP models in settlement prediction at points ES2-8 and ES4-10,demonstrating its strong anti-interference and generalization capabilities.This study has developed a novel method for forecasting and analyzing dam settlements with practical significance.Moreover,the established IRF model can also provide guidance for modeling health monitoring of other structures.

不同微波作用模式下深部巷道砂岩的破坏行为和能量演化特征

有效破碎硬岩和预防并控制岩爆灾害是深部高地应力区施工的两个关键问题,也是确保深部工程安全高效施工的两条最重要的途径。本文以微波作用下坚硬砂岩的致裂弱化为出发点,以单次微波辐照处理的持续时间为变量,同时结合力学测试和声发射监测方法,论证了微波作用对防治岩爆灾害的可能性。结果表明,在微波作用下,坚硬砂岩的裂纹损伤应力占比从77%下降到62%;耗散能占比从6%增加到20%,基于能量的脆性指数从0.94下降到0.72;声发射监测结果表明,经微波作用后,砂岩的平静期从总时间的56.2%和59.6%大幅缩短至11.5%和8.6%。在本试验中,1 kW微波作用时长的阈值为2 min,超过该阈值时,岩石就会受到不可逆损伤。本研究可为深部高地应力区高效、安全破岩提供必要的理论支持和技术指导。

Wind-speed forecasting model based on DBN-Elman combined with improved PSO-HHT

Random and fluctuating wind speeds make it difficult to stabilize the wind-power output,which complicates the execution of wind-farm control systems and increases the response frequency.In this study,a novel prediction model for ultrashort-term wind-speed prediction in wind farms is developed by combining a deep belief network,the Elman neural network,and the Hilbert-Huang transform modified using an improved particle swarm optimization algorithm.The experimental results show that the prediction results of the proposed deep neural network is better than that of shallow neural networks.Although the complexity of the model is high,the accuracy of wind-speed prediction and stability are also high.The proposed model effectively improves the accuracy of ultrashort-term wind-speed forecasting in wind farms.

Influence of repeated freeze-thaw on dynamic modulus and damping ratio properties of silty sand

Under repeated freezing and thawing in deep seasonal frozen regions, the stability and strength of the soil are imposed in the form of large uneven settlement, instability and strength reduction, which affect the normal operation of railway lines. This study is to obtain the influencing rules of freeze-thaw on the dynamic properties （dynamic strain, confining pressure and compactness） of silty sand. Based on an amount of inner tests, the dynamic modulus and damping ratio properties of silty soil subjected to repeated freeze-thaw cycles were deeply researched and analyzed. The results are as follows： At the same dynamic strain, the relationship of dynamic stress and freeze-thaw cycles presents negative cor- relation, and the relationship of dynamic stress, confining pressure and compactness present positive correlation. The dynamic modulus double decreases while the damping ratio double increases with incremental increase in dynamic strain. The dynamic modulus sharply decreases while the damping ratio increases with incremental increase in freeze-thaw cycles, and then the changes level off after six freeze-thaw cycles. The dynamic modulus increases while the damping ratio decreases as the confining pressure and compactness increase at the same strain level.

Building a More Sustainable Chinese Loess Plateau

The Chinese Loess Plateau,a region of remarkable ecological and economic value,grapples with significant water management challenges due to its distinctive geology and climate.This perspective offers a short review of the eco-environmental protection measures undertaken in the Loess Plateau,underscoring the transformative impacts of initiatives such as the“Grain for Green”project.However,it also highlights the enduring challenges,including land degradation,water resources issues,socio-economic inequities,and the implications of climate change.Particularly,water management emerges as a pivotal issue with far-reaching repercussions for soil conservation,biodiversity,and human livelihoods.The paper concludes by proposing future actions,emphasizing the necessity for policy modifications,novel initiatives,and research to tackle these challenges and foster sustainable development in the Loess Plateau.The insights gained from this region could offer invaluable lessons for other regions confronted with similar challenges,thereby contributing to global efforts to mitigate desertification and champion sustainable development.

Morphogenesis and Molecular Phylogeny of a Marine Urostylid Ciliate Apokeronopsis wrighti(Protista, Ciliophora, Hypotrichia)

Hypotrichs are one of the highly differentiated ciliated lineages which play important roles in ecological, environmental,evolutionary and basic biological studies. In the present study, we investigated the living characteristics, infraciliature, nuclear apparatus, ontogenesis and phylogenetic position of a marine hypotrichous ciliate, Apokeronopsis wrighti Long et al., 2008, which was isolated from coastal waters in Shenzhen, China. The new isolate resembles the type population in terms of morphological characteristics, morphometrics, and SSU rRNA gene sequence that is with a 99.7% similarity. Ontogenesis of A. wrighti is characterized by oral primordium for the proter as well as marginal and dorsal kineties anlagen in both filial products formed de novo, and the cirral row arranged along the paroral and endoral arises from several anterior frontoventral-transverse cirral streaks. Phylogenetic analyses based on SSU and concatenated gene data suggest that five species of Apokeronopsis form a monophyletic clade, and the genus Apokeronopsis is closely related to Thigmokeronopsis and Metaurostylopsis.

Large-scale toppling slope under water level fluctuation of reservoir:A case of Yunnan Province,China

Landslides induced by reservoir inundation are common in Southwest China,negatively influencing hydropower stations.TheWunonglong hydropower station dam was constructed in the upper reaches of the Lancang River,accordingly causing the water level at the Lajinshengu slope to increase by 30 m.A tension crack with a visible depth of 8 m was observed in the upper sector of the Lajinshengu slope after reservoir impoundment for 170 d.In the following days,numerous cracks appeared on the surface of the slope,and the maximum displacement of the slope reached 3.22 m.Then,a large-scale active deformation body within the Lajinshengu slope formed with an area of 2.62×10^(5)m^(2)and a volume of 1.65×10^(7)m^(3).Detailed field investigations,on-site monitoring,and centrifugal model tests were carried out to analyze the surface features,deformation characteristics,and failure mechanism of the Lajinshengu slope.The results show that the slope is an ancient landslide,divided into two parts(i.e.zone A and zone B)by the gully.Zone B is a traction landslide caused by the displacement of zone A.The longterm inundation weakens the soft rock at the slope foot,intensifying the toppling of bedrock and consequently triggering the sliding of the overburden in zone A.The failure mode of the Lajinshengu slope is a typical case of toppling-sliding failure,and the underlying rock toppling drives the overlying sliding.In addition,early identification methods for toppling deformation covered by overburdened soil were proposed based on monitoring data and deformation signs.

大规模风电场对草地碳循环的影响

Deployment of wind energy is an essential renewable energy source that mitigates climate change and reduces air pollution[1].Over the last several decades,wind energy development has increased worldwide,expanding from~20 to~900 GW(gigawatt)during 2001–2022[1].

Impacts of cadmium addition on the alteration of microbial community and transport of antibiotic resistance genes in oxytetracycline contaminated soil

The large-scale development in livestock feed industry has increased the chances of antibiotics and heavy metals contamination in the soil.The fate of antibiotic resistance genes(ARGs)and microbial community in heavy metals and antibiotic contaminated soil is still unclear.In this study,we investigated the effect of cadmium(Cd)addition on the transport of ARGs,microbial community and human pathogenic bacteria in oxytetracycline(OTC)contaminated soil.Results showed that the addition of OTC significantly increased the abundance of ARGs and intI1 in the soil and lettuce tissues.The addition of Cd to OTC treated soil further increased the abundance and translocation of ARGs and intI1.Moreover,Cd promoted the transfer of potential human pathogenic bacteria(HPB)into lettuce tissues.Compared with O10 treatment,the addition of Cd decreased the concentration of OTC in soil and lettuce tissue,but slightly increased the fresh weight of lettuce tissues.Redundancy analysis indicated that bacterial community succession is a major factor in ARGs variation.Network analysis indicated that the main host bacteria of ARGs were mainly derived from Proteobacteria.Correlation analysis showed that intI1 was significantly correlated with tetG,tetC,sul1,sul2,erm X,and ermQ.Meanwhile,potential HPB(Clostridium,and Burkholderia)was significantly correlated with intI1 and eight ARGs(tetG,tetC,tetW,tetX,sul1,sul2,ermX,and ermQ.).The findings of this study suggest that the addition of heavy metals to agricultural fields must be considered in order to reduce the transfer of ARGs in the soil and crops.

Theoretical and experimental advances on heat transfer and flow characteristics of metal foams

Open cell metal foam can be applied to greatly improve thermal performance of heat sink and heat exchanger,so that it has been widely used in the fields of thermal(or heat)control system of aerospace vehicle and energy utilization system and become a very important topic for research in the aerospace thermophysics field,and more and more attentions have been attracted.The optimal design of metal foam heat transfer devices is based on the understanding the flow and heat transfer characteristics in metal foam.This article reviews some recent progresses of theoretical and experimental researches on heat transfer enhancement and flow characteristics of metal foam.We found that the pore cell simplification models of metal foams generally fall into four categories,among which the most commonly used cell model is Kelivin model.Some exploratory works performed by the current authors are also introduced,such as the effect of boundary conditions on the heat transfer enhancement;the theoretical modelling of interfacial convective heat transfer taking into account heat conduction between foam ligaments;and the flow characteristics under relatively high velocity.The analytical results show that the flow characteristics of metal foam at relatively high speed are completely different from those at low speed,a further thorough study of the heat transfer and flow characteristics of metal foam is necessarily required.In this paper,two types of partial filling techniques are discussed.The heat transfer performance of partially filled tubes was evaluated by both the performance evaluation criteria and the performance evaluation plot of enhanced heat transfer techniques oriented for energy-saving.The results show that the filling type of metal foam have a significant impact on its heat transfer enhancement performance.Therefore,the filling method of metal foam should be further studied,in order to optimize the thermophysical properties of heat transfer devices.

A review on thermal application of metal foam

Heat exchangers embedded with metal foam are drawing increasing attention in the thermal application field,due to the performance of low density,large ratio of surface area to volume as well as high thermal conductivity. In these applications,compact heat exchanger,solar thermal facilities and thermal energy storage are the three core components. This paper focuses on the lasted advances in thermal applications,presenting a review of theoretical and experimental progress over metal foam in thermal application. The empirical and theoretical models for pressure drop,heat transfer coefficient and performance evaluation criteria of compact heat exchangers with metal foam are reviewed and discussed,especially different optimized configurations.There is a trade-off between heat transfer enhancement and increase of pressure drop. Some exploratory work performed by present authors are also introduced. The manufacturing,heat transfer and flow characteristics of tube bundle wrapped with metal foam are taken into account for optimization of heat exchanger. It is confirmed that the conversion mechanism of heat transfer is carried out that heat conduction is the dominative term at high dimension permeability. The correlations of heat transfer rate and pressure drop for staggered and single row tube bundle wrapped with metal foam are concluded,respectively. The effects of different bonding methods are revealed for point-contact in metal foam and base tube. The powder-sintering method can provide a stable and minimum-thickness bonding layer. Various types of solar thermal facilities utilized metal foam to improve the energy conversion efficiency from solar radiant energy to thermal energy are also reviewed and discussed,including solar collector for intermediate-low temperature utilization and solar receiver for high temperature utilization. The Last but not least,existing and future metal foam thermal application stations are overviewed.

A graphics processing unit-based robust numerical model for solute transport driven by torrential flow condition

Solute transport simulations are important in water pollution events.This paper introduces a finite volume Godunovtype model for solving a 4×4 matrix form of the hyperbolic conservation laws consisting of 2D shallow water equations and transport equations.The model adopts the Harten-Lax-van Leer-contact(HLLC)-approximate Riemann solution to calculate the cell interface fluxes.It can deal well with the changes in the dry and wet interfaces in an actual complex terrain,and it has a strong shock-wave capturing ability.Using monotonic upstream-centred scheme for conservation laws(MUSCL)linear reconstruction with finite slope and the Runge-Kutta time integration method can achieve second-order accuracy.At the same time,the introduction of graphics processing unit(GPU)-accelerated computing technology greatly increases the computing speed.The model is validated against multiple benchmarks,and the results are in good agreement with analytical solutions and other published numerical predictions.The third test case uses the GPU and central processing unit(CPU)calculation models which take 3.865 s and 13.865 s,respectively,indicating that the GPU calculation model can increase the calculation speed by 3.6 times.In the fourth test case,comparing the numerical model calculated by GPU with the traditional numerical model calculated by CPU,the calculation efficiencies of the numerical model calculated by GPU under different resolution grids are 9.8–44.6 times higher than those by CPU.Therefore,it has better potential than previous models for large-scale simulation of solute transport in water pollution incidents.It can provide a reliable theoretical basis and strong data support in the rapid assessment and early warning of water pollution accidents.

A non-uniform grid approach for high-resolution flood inundation simulation based on GPUs

In view of the frequent occurrence of floods due to climate change, and the fact that a large calculation domain, with complex land types, is required for solving the problem of the flood simulations, this paper proposes an optimized non-uniform grid model combined with a high-resolution model based on the graphics processing unit (GPU) acceleration to simulate the surface water flow process. For the grid division, the topographic gradient change is taken as the control variable and different optimization criteria are designed according to different land types. In the numerical model, the Godunov-type method is adopted for the spatial discretization, the TVD-MUSUL and Runge-Kutta methods are used to improve the model’s spatial and temporal calculation accuracies, and the simulation time is reduced by leveraging the GPU acceleration. The model is applied to ideal and actual case studies. The results show that the numerical model based on a non-uniform grid enjoys a good stability. In the simulation of the urban inundation, approximately 40%–50% of the urban average topographic gradient change to be covered is taken as the threshold for the non-uniform grid division, and the calculation efficiency and accuracy can be optimized. In this case, the calculation efficiency of the non-uniform grid based on the optimized parameters is 2–3 times of that of the uniform grid, and the approach can be adopted for the actual flood simulation in large-scale areas.

Correlation Analysis of Transient Heat Transfer Characteristics for Air Precooling Aggregate

In dam works, air precooling of aggregate is a common and effective method to avoid temperature cracks in concrete structure. In order to offer a reliable design theory for the air precooling process to avoid unreasonable energy consumption, the transient heat transfer characteristics of the aggregate are intensively analyzed. The combined structure of the aggregate and the interstitial space in the hopper is treated as a porous structure, and the space-average method is used to simulate the transient heat transfer process. Simulation results show that size of the hopper and the average air velocity in the cross section have great influence on the transient heat transfer process of the aggregate, while the porosity in the range of 0.4-0.5 has little influence. Nomograms are abstracted from simulation results, and then correlations of the compared excess temperature are precisely fitted to predict the air precooling transient heat transfer process of the aggregate.