There are various discontinuities in geotechnical engineering problems, which can be roughly divided into two types: one is the discontinuities formed by various actions of rock and soil, such as ...joints, faults, fissures and shear failure surfaces in rock mass; The other is the contact surface between geotechnical structures such as various foundations, retaining structures, underground structures and geotechnical bodies. Therefore, we cannot ignore its existence in computation. At present, the finite element method and other numerical methods have been widely used to solve geotechnical engineering problems, but the solution of the above discontinuous deformation problems has not been well solved. In this paper, the constitutive model of rock and soil is established. Based on the theory of image processing technology, the common methods of dealing with discontinuous deformation problems in finite element method are pointed out, and the unreasonable points are pointed out. It is more reasonable to treat such problems as contact problems, because it can reflect the main characteristics of discontinuous deformation surface. Come on. The three-dimensional image of the constitutive model has three important functions: (1) it is helpful to enhance the theory of constitutive theory and lay a foundation for further mastery of the theory of constitutive theory; (2) Abstract constitutive theory is no longer just a bunch of boring formulas, which is helpful for beginners to improve their interest in learning the theory of constitutive theory. (3) Finally, a three-dimensional image constitutive model of rock and soil is established through experiments, and the program written by MATLAB is compared with the test results of conventional triaxial compression of rock and soil, which fully verifies the correctness and effectiveness of the constitutive model of rock and soil established in this paper.
For the first time, in the current work, a dynamic stability analysis of a tilted curved pipe in a supersonic airflow under thermal loading is presented. The heat-transfer continuum problem is used ...for simulating the thermal environment conditions. The tilted pipe is reinforced by carbon nanotube agglomerations (CNTAs). For simulating the displacement fields of the current structure, Quasi-2D refined high order shear deformation theory is studied. The verification segment is divided into two parts. In the first and second sections, the credibility of the results of this study are confirmed by the results extracted using COMSOL multiphysics software and published articles in the literature, respectively. The results show that Mach number, hydrodynamic pressure, temperature change, yaw angle, and geometry properties of the current structure have a significant impact on the frequency information of the tilted curved pipe reinforced by CNTAs in supersonic airflow. One of the presented results is that the effects from volume fraction of clusters in the representative value element, amount of CNTs located outside the clusters, and the highest value related to the volume fraction of the CNT, parameters on the supersonic airflow characteristics of the system are more considerable at the higher value of the length to radius ratio of the pipe.
Several researches about airflow distribution in a room generated by fabric air dispersion system (FADS) were reported, but details about the simulation in computer fluid dynamics (CFD) method were ...not elaborated. In present work The commercial software FLUENT with standard
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turbulence model is applied to predict air distribution in a room ventilated by FADS in penetration mode, where FADS is described with the porous media model based on the modified Forchheimer equation. And more details about the simulation are given. Flow visualization near the region of FADS is conducted using dry-ice as a smoking material. The distribution of indoor air velocity and temperature and draught rating (DR) around the ankle and neck level are predicted. The simulation well matches the corresponding experimental value and results of earlier work. Results showed that air is radially discharged out in the direction perpendicular to the spatial cambered porous fibre in lower velocity, and evenly distributed along its length direction when air is distributed by FADS in penetration mode. The velocity of indoor air is very low, and the vertical air temperature difference is small (less than 2 K). DR around the ankle and neck is immune to supply air flow rate and location, which is less than the comfort limit of ASHRAE Standard 55-2004. In addition, airflow pattern is greatly impacted by the location and strength of heat load.
Slope deformation and failure is an inevitable engineering problem in highway construction and operation in mountainous areas. Its essence is a continuous–discontinuous gradual failure process of ...slope under the action of unbalanced force. Slope deformation and failure mechanism is the basis and key content of its emergency treatment and comprehensive treatment. In this study, the continuous–discontinuous element method (CDEM) and finite difference method are used to analyze the deformation mechanism and support the effect of a scattered slope in the Biwei Expressway. The results showed that the change in the local geological environment caused by roadbed excavation leads to slope slippage along the surface and then pulls the upper rock mass gradually to produce slippage failure, resulting in the stability gradually decreasing. The mechanism is traction sliding–tensile cracking. The continuous–discontinuous element method can effectively simulate the formation process of the main and sub sliding planes during excavation and can better display the phenomenon of slope failure and gradual disintegration. The emergency disposal of the gravity anti-sliding retaining wall in front of the slope can effectively control further deformation and ensure temporary stability. In comprehensive treatment, step-type slope excavation, gravity anti-sliding retaining wall, and anchor frame beam are adopted to control the deformation and failure of slope and ensure long-term stability. The numerical simulation results are consistent with the actual results, which effectively explains the rationality of this study. The research results of this study can provide some reference for the emergency treatment and comprehensive treatment of slopes in mountainous areas and for the construction and operation of highways and other infrastructure in mountainous areas.
•The more the porosity, the lower the pressure inside FADS.•The higher the porosity, the poorer the uniformity of air velocity distribution.•The effect of fiber diameter is similar with the effect of ...porosity.•Increasing air flow rate aggravates the nonuniformity of air velocity distribution.•Results would help guide the optimum design of FADS in penetration mode.
Fabric air dispersion system (FADS), as a ventilation terminal, can help create a clean and comfortable indoor environment. Several studies mainly focused on the characteristics of airflow generated by FADS. However, the effects of the configurations on the airflow characteristics were rarely studied. Based on our pervious work, the effects of fiber porosity, fiber diameter and supply air flow rate on characteristics of air velocity and pressure inside FADS were numerically studied and the results were validated by experiments. It is shown that larger porosity or fiber diameter lead to lower pressure inside and poorer distribution of air velocity along the length direction of FADS. Higher supply air flow rate aggravates the non-uniformity of air velocity distribution, and increases the pressure inside. The combined effects of the three factors should be taken into consideration in order to achieve a uniform distribution of air velocity along the length direction and reduce fan energy consumption and noise level. Results of this study would be useful to guide the optimum design of FADS in penetration mode to expand its applications, especially in small enclosed spaces, where air quality, energy conservation and noise level are in high demand.
No existing diffuser models may be used to effectively describe the fabir air dispersion system (FADS), a new ventilation terminal made of ploymer. A porous media model was proposed to describe FADS ...in present work. And the corresonpongding mathematical model was developed for the airflow through FADS. The characteristics of airflow through FADS was predicted using the commercial software FLUENT with the standard
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ɛ turbulent model. The simulation results were well matched with the corresponding experimental value suggesting that it is feasible to describe FADS using the porous media model. Results showed that the air in the central zone flows forward with a decreasing velocity along the flow direction, and the air in the porous fibre eventually creeps out through its tiny-size holes at very low speed in the direction perpendicular to the porous fibre. The airflow close to the FADS is evenly distributed along the flow direction with a very low velocity. It is also concluded that the internal total pressure and dynamic pressure decrease slightly, while the internal static pressure increases slightly with a decaying increment along the flow direction of the FADS.
This innovative study develops a new analytical model to investigate the dynamic responses of asphalt pavements combined with attached mass-spring-damper systems under moving loads. Unlike existing ...methods that rely on finite element (FE) approximations, an exact solution for the coupled vibroacoustic behavior is proposed using first-order shear deformation plate theory (FSDPT), Hamilton's principle, and Fourier-Laplace transforms. The acoustic pressure is first predicted using Rayleigh integral analysis. Afterwards, the responses are transformed into the time domain using Durbin's numerical inverse Laplace transform strategy. The model utilizes Rayleigh integral analysis to generate innovative predictions of acoustic pressure and uses numerical inversion to accurately determine transient responses in the time domain. The suggested technique has been extensively validated against data from prior research and COMSOL Multiphysics® FE simulations, which confirms its correctness. Parametric analyses provide new insights into the effects of damper and spring coefficients, velocity, and loading frequency on the pavement's vibroacoustic behavior and the time-history response of the attached mass-spring-damper systems. Notably, the model offers fresh theoretical insights into the complex interplay between system parameters and the pavement's vibration and noise patterns.
•Higher excitation frequencies increase pavement and mass-spring-damper displacements.•Stiffer springs align mass-spring-damper displacement with pavement response.•Higher observation points reduce sound pressure due to wave spreading.•Sound pressure peaks when excitation matches system's natural frequency.
Coastal wetlands are located in the overland area between land and sea and play an important ecological role, but social and economic development and the acceleration of urbanization have resulted in ...the degradation of the ecological functions of coastal wetlands and serious pollution within the wetlands. The study of the spatial and temporal changes in the ecological environmental quality of coastal wetlands can suggest feasible response strategies for the ecological construction of coastal wetlands. This study uses RS and GIS technology, based on the PSR model, AHP method and InVEST model, to study the spatial and temporal changes in the ecological environmental quality of the Linghekou wetland and to propose early warning on future ecological and environmental conditions. The results show the following: (1) The natural wetland area decreased, the landscape fragmentation index increased and the wetland landscape showed a degradation trend between 2005 and 2020. (2) The composite indices for the evaluation of the ecological environmental quality of the Linghekou wetland in 2005, 2010, 2015 and 2020 were 0.473, 0.380, 0.353 and 0.378, respectively, with the ecological environmental quality declining from a sub-healthy state in 2005 to a sub-sick state in 2020, with increasing interference from human activities, increasing differentiation of the internal organization of the wetlands and degradation of ecological services. (3) The habitat quality of the Linghekou wetland has improved since 2015 due to the implementation of local conservation measures, but the habitats are still under strong pressure from anthropogenic disturbance. (4) The predicted results for 2025 and 2030 show that the ecological environmental quality of the Linghekou wetland will continue to deteriorate in the future, especially in the northwestern and central-eastern parts of the study area, where anthropogenic disturbance will continue to intensify and habitat degradation will become more severe in the future. This study provides a scientific reference for coastal wetland management and ecological construction, and also enriches the research results on coastal wetlands in the field of ecological and environmental assessment.
The regional fire protection plan is an important part of the city’s overall plan, which represents the deepening of the regional fire protection plan and the specific content of the city’s economic ...regional fire protection plan. Fire protection is an important part of national economic and social development, and it is also one of the indicators to measure the level of modern culture. Effective and practical fire protection planning can effectively prevent and reduce fire risks and protect the lives and property of the people, which is very important for social development. In order to optimize the regional fire model, this study uses a very objective fuzzy theory to analyze and discuss the research objects. In view of the large amount of fuzzy information in fuzzy optimization, fuzzy criterion recognition, and fuzzy grouping, based on the generalized fuzzy distance and fuzzy number, this paper proposes a multiobjective fuzzy theory-based comprehensive evaluation and optimization model of fire planning for major hazard sources. The results show that hotel fire risks tend to be higher, which is the focus of people’s attention. Among the fire hazards, wholesale, retail, and catering industries are the hardest hit areas, accounting for 66.3%, and some other industries are also disaster areas that need to be dealt with.
Environmental factors play an important role in contributing to intricate compositional dynamics and volatile metabolites in food fermentation. However, our understanding of which and how ...environmental factors affect volatile metabolites during sesame flavor-type baijiu fermentation is poor. Here, we examined the effects of environmental factors on the bacterial and fungal community to determine how changes in representative factors impact the microbial structure, diversity, and volatile metabolites in three fermentations. Results showed that bacterial community (ANOSIM: R = 0.79, P = 0.001), fungal community (ANOSIM: R = 0.65, P = 0.001), and volatile metabolites (ANOSIM: R = 0.84, P = 0.001) were significantly different in three fermentations. Acidity, ethanol, and moisture negatively impacted bacterial composition and diversity (P < 0.05). The fungal diversity and structure were positively and significantly affected by acidity (path coefficient, b = 0.54 for diversity, b = 0.35 for structure, P < 0.05). The fungal community rather than the bacterial community was the strongest driver of volatile metabolites. Fungal structure and diversity were equally important for the composition and content of volatile metabolites (structure: b = 0.50, diversity: b = 0.56, P < 0.05). 66 % of variations in volatile metabolites could be explained. Altogether these results indicated that acidity strongly drove volatile metabolites by modulating fungal structure and diversity. This work provides insights into managing volatile metabolites by regulating initial acidity in sesame flavor-type baijiu fermentation.
•Acidity impacted the structure and diversity of bacteria and fungi.•The fungal community was the strongest driver of metabolites.•Fungal structure and diversity were equally important for metabolic structure.•Acidity is a major environmental factor affecting metabolites.•Acidity strongly drove metabolites by modulating fungal structure and diversity.
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