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In order to effectively address the potential hazards associated with the construction of Phase II of the YE Water Supply Project’s KS tunnel in Xinjiang, this study employs the WBS-RBS (Work Breakdown Structure and Risk Breakdown Structure) method for risk identification. This approach aims to identify various risks that may arise during TBM (Tunnel Boring Machine) construction. To prevent incomplete risk factor identification resulting from subjective judgment, a risk index system is established based on the identification results. Subsequently, a matter-element extension model is utilized to quantify the risk factors within this index system, and comprehensive weights are determined using variable weight theory to assess construction risk levels. Importance analysis of each index is then conducted to identify those with significant impact on risk evaluation outcomes. Finally, by comparing actual engineering cases with other risk evaluation models, this paper verifies the reliability of its constructed risk assessment model and proposes measures for controlling potential risks based on these evaluations. The paper provides a clear definition of safety risks encountered during TBM construction and conducts comprehensive risk assessments as a valuable reference for research related to the tunnel boring machine construction period in tunnel engineering.

In order to solve the problem of the poor adaptability of the TBM digging process to changes in geological conditions, a new TBM digging model is proposed. An ensemble learning prediction model based on XGBoost, combined with Optuna for hyperparameter optimization, enables the real-time identification of surrounding rock grades. Firstly, an original dataset was established based on the TBM tunneling parameters under different surrounding rock grades based on the KS tunnel. Subsequently, the RF–RFECV was employed for feature selection and six features were selected as the optimal feature subset according to the importance measure of random forest features and used to construct the XGBoost identification model. Furthermore, the Optuna framework was utilized to optimize the hyperparameters of XGBoost and validated by applying the established TBM dataset of the KS Tunnel. In order to verify the applicability and efficiency of the proposed model in surrounding rock grade identification, the prediction results of five commonly used machine learning models, Optuna–XGBoost, Random Forest (RF), Gradient Boosting Decision Tree (GBDT), Decision Tree (DT), XGBoost, and PSO–XGBoost, were compared and analyzed. The main conclusions are as follows: the feature selection method based on RF–RFECV improved the accuracy by 8.26%. Among the optimal feature subset, T was the most essential feature for the model’s input, while PR was the least important. The Optuna–XGBoost model proposed in this paper had higher accuracy (0.9833), precision (0.9803), recall (0.9813), and F1 score (0.9807) than other models and could be used as an effective means for the lithological identification of surrounding rock grade.

High evaporation in plain reservoirs in arid regions exacerbates water shortages. Investigations have established that floating elements assembled modular with maximum coverage on the water surface, such as floating balls, can effectively mitigate ineffective water evaporation. Nevertheless, the employment of floating balls to achieve maximum coverage of the water surface may pose a threat to aquatic life and the initial investment is substantial. Thus, this study employs floating balls for partial coverage of the water surface, intending to examine the impact of altering the coverage rate of the floating balls on the efficiency of evaporation inhibition, energy balance, and water quality. To achieve this goal, we established five sets of evaporators on the top of the reservoir dam, each with a surface area of 1.13 m2 and a depth of 0.8 m. These evaporators were covered with varying percentages of black high-density polyethylene floating balls with a diameter of 0.1 m, including 0%, 18.74%, 37.49%, 56.23%, and 74.98% coverage. The results show that the evaporation inhibition rate is less than the coverage rate. The solar radiation flux is decoupled on the evaporation surface, and the change of coverage ratio affects the size, transfer direction, and relative proportion of each component of the energy balance. With the increase of coverage, more radiation flux is converted into sensible heat flux, which increases the Bowen ratio. The water surface covered by the floating balls has a particular effect on improving the water quality. With the increase in coverage rate, the concentration of chlorophyll, nutrient salt, and suspended solids decreased significantly, and the impact on dissolved oxygen in the water was less. Finally, the economic viability of varying coverage ratios of floating balls was also confirmed. Currently, there is a paucity of reservoir-scale studies, and the effect of floating balls on evaporation and energy balance in the flowing water of actual reservoirs needs further investigation.

Spin-orbit interaction (SOI) of light has attracted enormous interest for its potential applications in controlling light at nanoscale and holds promise for future optical information technology and optoelectronics. In particular, the transverse spin in evanescent waves is regarded as distinct manifestation of SOI and an emerging candidate for miniaturizing optoelectronic circuits. However, further application has been hampered by the inability to conveniently generate light field with configurable transverse spin. Here, we present a simple method to generate free-space light field with arbitrary transverse spin utilizing vector beam interference and numerically demonstrate the configurable spin orbital coupling in nanophotonic waveguide. Chiral waveguide with excellent extinction ratio up to 42 dB is achieved in our simulation. The propagating direction of guided mode can be fully controlled via tuning the ellipticity of transverse spin. The device is compatible with existing integrated nanophotonic devices and may find valuable applications in future optical information processing and optical communication technology.

The interfacial friction characteristics of composite geomembranes have a significant impact on the stability of engineering structures. To comprehensively analyze the interfacial friction properties of composite geomembranes and cushion materials, the effects of shear material, roughness, shear rate, and test temperature were studied through laboratory direct shear friction tests. The results show the improved interface friction performance of the composite geomembranes and granular material. With the increase in the particle size of the test material, the friction angle of the plastic film surface decreased, and the friction angle of the cloth interface increased. The rougher the mortar surface, the greater the interfacial friction angle. The faster the shear rate, the larger the interfacial friction angle. The higher the test temperature, the smaller the interfacial friction angle. The research results provide a theoretical basis for the design of anti-seepage forms of dam bodies, and serve as a reference for engineering designers in evaluating the stability of dam slopes.

(1) Background: In arid and semi-arid reservoirs, water surface evaporation is the main method of water dissipation in order to inhibit the evaporation of water and enhance economic efficiency. The evaporation inhibition rate of water-piled PV at different times of the year is derived from the anti-evaporation test of water-piled PV, and a new idea is proposed for water conservation in plains reservoirs in arid areas. (2) Methods: The test was conducted by dividing the area into groups A and B, with and without PV panel shading. In situ observation and numerical calculation were used to measure the atmosphere’s temperatures, test group, and PV module. The saturated water vapor pressure difference was then calculated according to Dalton’s principle to analyze the economic benefits of water saving. (3) Results: Based on the test results, it was found that the shading of PV panels had a cooling effect on the water body, the PV module, and the atmosphere. Group A showed a 44.2% decrease in the saturation water vapor pressure difference compared to Group B. The maximum evaporation suppression rate of 40.2% was observed in July, while the minimum rate of 12.2% was observed in January. The average evaporation suppression rate for the entire year was 29.2%. By utilizing the annual water savings for agricultural irrigation, it is possible to cover 38 hm2 of land and generate a revenue of 39,000 CNY. (4) Conclusions: The photovoltaic water cover can effectively reduce water evaporation and generate economic benefits.

In this paper, a multiobjective optimization method considering both time limit and cost of lean cemented overtopped cofferdam diversion scheme as objectives is proposed. In the multiobjective optimization method, the main constraint condition is the reliability of the construction period, which also considers the design specification, dam site rainfall, construction capacity, and other constraint conditions. Pareto solutions with the diameter of the diversion tunnel and the height of cofferdam as parameters are obtained using perturbation weight method. Finally, the optimal scheme was obtained according to the importance of the critical node project period and its free time difference. The case study showed that the cost is low, the construction period is reasonable, and the results are consistent with the expert decision system in this model. The Monte Carlo method was used to simulate the construction of lean cemented cofferdam. The study shows that the construction speed of lean cemented cofferdam is slow under frequent rainfall condition. The lower limit of construction speed of key projects greatly affects the scheme. Increasing construction equipment redundancy is an important way to increase construction speed. The free float time difference of cofferdam construction is the key point of scheme decision.

In-depth analysis of the characteristics of water and sedimentary changes at the confluence of the upper reaches of Weigan River and Heizi River is the prerequisite and basis for studying the future water and sedimentary situation in the Kizil Reservoir. This article analyzes the trend, mutation point and periodicity of the water and sedimentary sequence with multi-methods. The double cumulative curve method and the attenuation analysis method were used to analyze the impact of precipitation and human activities on runoff and sedimentary transport, and other influencing factors were qualitatively analyzed also. The results showed that: (1) In the past 60 years, Kizil Reservoir's runoff and sedimentary transport have shown an upward trend; the mutation point of the reservoirs' runoff was in 1994; the annual runoff had a periodicity of 7, 13, and 28 years; the annual sedimentary transport had a periodicity of 4, 12, and 26 years. (2) The impact of precipitation and human activities on runoff were 485.37% and −385.37%, respectively; the impact of precipitation on sedimentary transport was first high and then low, while the impact of human activities on sedimentary transport was first low and then high. Solar activities, ENSO, underlying surface changes and glacier snow melt also contributes to water-sediment changes to some extent. HIGHLIGHTS Various analytical methods were used to analyze the changing trends and mutation points, and comprehensively determined the results.; The ensemble empirical mode decomposition (EEMD) method was used to accurately analyze the periodicity of runoff and sedimentary transport.; The quantitative and qualitative systematic analysis of the factors which affect water and sedimentary changes were carried out.;

The extent of reservoir sedimentation is an important index related to the functional operation of reservoirs. Therefore, it is vital to accurately conduct sedimentary assessment. In this paper, the analytic hierarchy process was used to determine subjective weights, gray correlation analysis and entropy weight method were used to determine objective weights. The combination weights obtained using optimized combination weighting method based on genetic algorithm were more suitable for the comprehensive analysis of the impact of reservoir sedimentation. This was then used to constructed a multi-level fuzzy comprehensive evaluation model based on improved cloud model. A reservoir was selected as the study object, and its sedimentation impact level was evaluated: the numerical characteristics of the stratus cloud of the comment on the impact of the reservoir sedimentation were (0.6372, 0.0664, 0.0795). The results showed that the reservoir sedimentation is considered as severe influence, and the sedimentation has become a major problem that needed to be solved urgently. The results of this paper could provide insight for reservoir research domestically and abroad. Furthermore, it could also enable managers to more accurately grasp the severity of reservoir sedimentation. HIGHLIGHTS The combination of the cloud model and genetic algorithm in computing was used to study and evaluate the influence of reservoir sedimentation. The calculation result was proved to be much accurate than that of the traditional method, and is more in line with the actual purpose of the project.; The multi-level fuzzy comprehensive evaluation model was constructed based on the improved cloud model for the sole purpose of analyzing the influence of sedimentation on reservoir function.; The improved combination weighting method based on genetic algorithm was used to solve the combination weight issues.;

Rock mass conditions are extremely sensitive to tunnel boring machine (TBM) tunneling. Therefore, establishing a surrounding rock excavatability (SRE) classification system applicable to TBM tunnels. Accurately and intelligently identifying excavatability grades can also facilitate efficient TBM tunneling and intelligent construction. Specific excavation and penetration rates were used to evaluate SRE. Their correlations with geological and tunneling parameters were explored using the field data from two water conveyance tunnels in China with different lithologies. A high-precision empirical SRE classification system was constructed using TOPSIS for multi-objective decision-making, and it was verified using engineering cases. An intelligent identification model for SRE grades in the stable phase of a TBM excavation cycle was established using 12,382 TBM rock-breaking datasets and deep forest models. Ten characteristic parameters, e.g., total thrust, were selected as model input features. Hyperparameter optimization was achieved using the grid search method. Deep forest was compared with decision tree, random forest, support vector classifier, and deep neural network. The contribution of the model’s features was measured using random forest. The main conclusions are as follows: the proposed SRE classification method is feasible and matches well with the actual excavation. In the intelligent identification of SRE classification, the accuracy and F1 scores when using deep forest were 96.33% and 0.9581, respectively. Deep forest exhibited better grade identification performance than the four models. Among the ten input features, penetration is the most important feature for the model’s input, while the top shield cylinder rod’s chamber pressure is the least important. The findings can provide some references for SRE classification and prediction and intelligent TBM control.

Current research on the evaporation inhibition effect of polyethylene (PE) floats has been relatively comprehensive, and the cost is relatively high when it is arranged in remote mountainous areas. In order to find a more economical anti-evaporation material, five kinds of solid expanded polystyrene (EPS) floating balls with different diameters of 10 mm, 40 mm, 80 mm, 120 mm and 150 mm were selected to study the evaporation suppression efficiency (ESE) of EPS floating balls on the evaporation of reservoir water surfaces in arid areas. The outdoor evaporator test and the wind wave test in the reservoir area were carried out. Combined with various meteorological data, the evaporation inhibition rates of EPS floating balls with different diameters during a non-freezing period were calculated. The durability, seepage prevention, wind resistance, frost resistance, aging resistance and other properties of EPS were observed under different climatic conditions. In the evaporator test, the relationship between the diameter of the floating balls and the ESE was not a single function. The ESE of floating balls with a diameter of 40 mm was the highest, at 76.31%. In the wind wave test in the reservoir area, the ESE of the 10 mm floating balls was the lowest, at 34.79%, and the ESEs of the other four diameters of EPS floating balls were above 85% and positively related to the diameter of the floating balls. The test further improved the selection scheme for the diameter of the anti-evaporation floating balls, provided a reference for the practical application of EPS floating balls in future water-saving projects in the reservoir area, and enriched the content of water-saving projects for plain reservoirs in arid areas.

In order to study the bearing safety and influencing factors of the support structures of hydraulic tunnels in cold regions under the action of low-temperature frost heave, a mechanical model of the support structure and surrounding rock was established. Taking a hydraulic tunnel of a hydropower station in Xinjiang as the research object, a combination of field measurement and a numerical simulation method was adopted to study the bearing safety of the support structure during a period of freezing weather. Based on this model, the effects of different thermal expansion coefficients, temperature differences, and surrounding rock porosity on the bearing safety of the support structure in the low-temperature region were studied. From the calculation results, it was concluded that the simulation results of the numerical model established by using the mechanical model in this paper were in good agreement with the actual measurement results of the project. The circumferential freezing and compressive stresses at the arch waist of the supporting structure of the project were the largest, and significant plastic strain was generated near the arch waist. The displacement at the arch of the supporting structure was the largest, while the weak points were at the arch waist and arch top of the supporting structure. The coefficient of thermal expansion, greater temperature difference, and increased porosity of the surrounding rock all led to an increase in the rock freezing and swelling force to varying degrees, thus reducing the load-bearing safety of the supporting structure. The research results could provide a theoretical basis and a reliable mechanical and numerical simulation model for establishing the bearing safety of tunnels in the cold region.

In nonlinear optical systems, the optical superposition principle breaks down. The system’s response (including electric polarization, current density, etc) is not proportional to the stimulus it receives. Over the past half century, nonlinear optics has grown from an individual frequency doubling experiment into a broad academic field. The nonlinear optics has not only brought new physics and phenomena, but also has become an enabling technology for numerous areas that are vital to our lives, such as communications, health, advanced manufacturing, et al . This Roadmap surveys some of the recent emerging fields of the nonlinear optics, with a special attention to studies in China. Each section provides an overview of the current and future challenges within a part of the field, highlighting the most exciting opportunities for future research and developments.

To explore the development process of the plastic zone of hydraulic tunnels and the mechanical characteristics of the support structure in a high ground temperature environment during construction period, methods, including theoretical analysis, numerical calculation, field monitoring test, etc., are used to analyze the generation and formation process of the plastic zone of surrounding rocks in the hydraulic tunnel under high ground temperature environment. The evolution law of mechanical characteristics of the support structure in surrounding rocks is studied. The development process and shape of the plastic zone in the tunnel under various high ground temperatures are simulated. The results show that after the excavation of the high ground temperature hydraulic tunnel, the plastic zone first appears at the arch waist in a crescent pattern, then extends to both sides and the spandrel, and connects with the plastic zone in the arch crown, forming a pattern of circle or butterfly. A higher initial temperature of the surrounding rock indicates a larger range and plastic strain of the plastic zone in the surrounding rock. At the same time, the plastic zone is easier to appear at the spandrel and arch foot and develop to the depth of the surrounding rock. The higher is the initial temperature of the surrounding rock, the greater will be the axial force and bending moment of supported shotcrete, the more obviously the bending moment of arch abutment and arch foot will grow, the greater will be the axial force value of the bolt and the farther the neutral point will be from the tunnel wall. While strengthening the arch waist, the support of the arch shoulder and arch foot should also be strengthened at a high temperature.

Abstract Birefringence-involved phase matching is demonstrated to be a novel mechanism to generate transform limited solitary pulses in an ultrafast mode-locking fiber laser cavity with normal dispersion.

Abstract Broadband light trapping and field localization is highly desired in enhanced light-matter interaction, especially in harmonic generations. However, due to the limited resonant bandwidth, most periodic plasmonic nanostructures cannot cover both fundamental excitation wavelength and harmonic generation wavelength simultaneously. Therefore, most previously reported plasmonic nonlinear optical processes are low in conversion efficiency. Here, we report a strong enhancement of second harmonic generation based on a three-layered super absorbing metasurface structure consisting of a dielectric spacer layer sandwiched by an array of random metallic nanoantennas and a metal ground plate. Intriguingly, the strong light trapping band (e.g. >80%) was realized throughout the entire visible to near-infrared spectral regime (i.e., from 435 nm to 1100 nm), enabling plasmonically enhanced surface harmonic generation and frequency mixing across a broad range of excitation wavelengths, which cannot be achieved with narrow band periodic plasmonic structures. By introducing hybrid random antenna arrays with small metallic nanoparticles and ultra-thin nonlinear optical films (e.g. TiO2) into the nanogaps, the nonlinear optical process can be further enhanced. This broadband light-trapping metastructure shows its potential as a building block for emerging nonlinear optical meta-atoms.

Stimulated emission depletion nanoscopy and its derivatives based on saturation induced competition effects have become an indispensable tool for studying cellular events and their dynamics in living conditions. The successful implementation of these techniques heavily relies on the competition between excitation induced spontaneous emission and stimulated emission from fluorescent dyes. The use of two laser beams at different wavelengths perplexes the optical system and the high intensity saturation beam inevitably introduces detrimental photobleaching effects. Harnessing the emerging saturation scattering of plasmonic nanoparticles, here, we demonstrate a novel fluorescence-free single-wavelength super-resolution imaging technique using gold nanoparticles. A lateral resolution of 101.2 nm (

Tunnel water inrush is complex, fuzzy, and random, and it is affected by many factors, such as hydrology, geology, and construction. However, few papers have considered the impact of dynamic monitoring on water inrush in previous research. In this study, considering geological, hydrological, and construction factors, as well as dynamic monitoring, a new multi-index evaluation method is proposed to analyze the risk of tunnel water inrush based on the normal cloud model. A new weight algorithm combining analytic hierarchy process and entropy method is used to calculate the index weight. The certainty degree of each evaluation index belonging to the corresponding cloud can be obtained by the cloud model theory. The final level of tunnel water inrush is determined via the synthetic certainty degree. The proposed method is applied to analyze the risk of water inrush in the SS (Shuang-san) tunnel constructed by a tunnel boring machine in the arid area of Northwest China. The evaluation results are not only basically identical to the results calculated by the ideal point and gray relation projection methods, but also agree well with the actual excavation results. This demonstrates that this new risk assessment method of water inrush has high accuracy and feasibility. Simultaneously, it also provides a new research idea to analyze the probability of tunnel water inrush and can provide a reference for related projects.

Investigating coherent acoustic vibrations in nanostructured materials provides fundamental insights into optomechanical responses and microscopic energy flow. Extensive measurements of vibrational dynamics have been performed for a wide variety of nanoparticles and nanoparticle assemblies. However, virtually all of them show that only the dilation modes are launched after laser excitations, and the acoustic bending and torsional motions, which are commonly observed in photoexcited chemical bonds, are absent. Unambiguous identification and refined characterization of these "missing" modes have been a long-standing issue. In this report, we investigated the acoustic vibrational dynamics of individual Au nanoprisms on free-standing graphene substrates using an ultrafast high-sensitivity dark-field imaging approach in four-dimensional transmission electron microscopy. Following optical excitations, we observed low-frequency multiple-mode oscillations and higher superposition amplitudes at nanoprism corners and edges on the subnanoparticle level. In combination with finite-element simulations, we determined that these vibrational modes correspond to out-of-plane bending and torsional motions, superimposed by an overall tilting effect of the nanoprisms. The launch and relaxation processes of these modes are highly pertinent to substrate effects and nanoparticle geometries. These findings contribute to the fundamental understanding about acoustic dynamics of individual nanostructures and their interaction with substrates. [ABSTRACT FROM AUTHOR]