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Copyright of Science Technology & Engineering is the property of Chinese Society of Technology Economics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The temperature and flow rate of coolant in the hot legs of pressurized water reactor (PWR) systems directly reflect the nuclear power and the heat transfer state of the reactor core, and are key parameters for reactor power control and safety protection. In order to comprehensively understand the distribution and evolution of the coolant flow-thermal coupling field in the upper plenum and hot leg of the Hualong One, and provide references for the measurement and control of core parameters, FEA (finite element analysis) method was employed in this paper to conduct CFD (computational fluid dynamics) numerical simulations of the coolant flow region in the upper plenum and hot legs. Firstly, a reasonably simplified 3D geometrical model of the upper plenum and hot legs of the Hualong One was established. Subsequently, the computational domain of the model was discretized into meshes and a mesh sensitivity analysis was performed. Finally, through calculations, a steady-state solution of non-isothermal coolant flow was obtained, with relative errors between flow rate, temperature and related design estimates and actual measured values all less than 2%. Analysis of the steady-state characteristics indicates that an uneven coolant temperature distribution at the inlet of the hot legs is caused by insufficient heat exchange between high and low temperature coolants near the vertical inner wall of the upper plenum, with a temperature difference between 14. 0 ℃ and 16. 3 ℃. As the coolant flows along the axial direction, both the temperature and flow distribution gradually become uniform and stable. Furthermore, the variation of the coolant temperature distribution is dominated by the flow of the low temperature coolant inside the hot legs. [ABSTRACT FROM AUTHOR]

In order to reduce the harm of dust and CO produced by tunnel blasting to the construction personnel, this paper puts forward an auxiliary ventilation method by adding the following portable gas exhaust device in the tunnel. In order to determine the effectiveness of the portable gas exhaust device, this paper simulated the application scene and application effect of the device based on the Numerical simulation software Fluent in Jiming Tunnel engineering, and obtained the tunnel flow field, dust and CO migration rule after the injection ventilation and the addition of the exhaust device. And the effect of the device on the flow field was verified, and the effect of the device on accelerating the discharge of dust and CO was verified. After the addition of the device, the change rule of CO concentration with time at five measuring points away from the palm surface was linearly fitted. The results show that: The addition of the following harmful gas exhaust device can effectively accelerate the discharge of dust and CO in the working area of the palm face. Within 120s of ventilation, the concentration of dust and CO in the same position after the addition of the device at the same time point is far lower than that under the pressure ventilation condition. After the addition of the device, the dust and CO concentration within 5m in front of the palm of 110-130s can be ventilated below the safe concentration. At the same time, the addition of the device will increase the disorder degree of the tunnel flow field to a certain extent. After the addition of the exhaust device, the change of CO concentration at the five measuring points in front of the palm of 30min of ventilation meets the single exponential function. Comparing the changes of dust and CO concentration before and after adding the portable harmful gas exhaust device, the effectiveness of the device was verified. [ABSTRACT FROM AUTHOR]

Coupled heat and moisture simulation of porous building materials has been widely used in building simulations. However, while underground buildings have received increasing attention with the scarcity of urban land, the related hygrothermal studies have received little attention, mainly because of the complex hygrothermal loads inside underground buildings and the large surrounding soil area included in the simulation. In order to accurately predict and optimize the hygrothermal performance of underground buildings and guide its hygrothermal simulation. By means of a scoping paper review, the theoretical approaches to heat and moisture transfer were reviewed. The results and deficiencies in the current stage of heat and moisture simulation of underground buildings from the perspectives of mathematical models, simulation tools, and boundary conditions were summarized. The results show that the challenges of coupled heat and moisture simulations for underground buildings lie in the uncertainty of soil composition and moisture, rainwater deposition and moisture migration on the soil surface, and the huge computational costs associated with large soil domains. The two-step approach, while simplifying the simulation, is not sufficient for hygrothermal simulations. There is a need to identify a recognized procedure / method to determine the exterior boundary conditions for underground envelopes to reduce the simulation complexity. [ABSTRACT FROM AUTHOR]

The drainage channel and water-conductivity drillholes were proposed to carry out the seepage prevention for the grottoes to solve a series of geological hazards, such as water seepage at the top grottoes and bad stability of foundation. The 3D high simulation geological model was established by ANSYS-FLAC 3D software, and the drilling on bedding rock slope simulation model was simulated by interface and fill command of FLAC 3D software, respectively. The effects of different schemes on rock stress, displacement and plastic zone were analyzed to select the best anti-seepage scheme based on theoretical analysis and numerical simulation on the condition of original rock stress. The results show that the adding water-drilling has the least damage to the rock slope and meets the requirements for drainage of precipitate water and groundwater. The stability of rock slope is mainly affected by the diversion hole near the outside of the mountain, the depth of borehole is no obvious effect on the deformation. The comprehensive rock mass reinforcement and treatment technology combined with mountain spray anchor net support and low-pressure grouting can improve the stability of mountain slope. This paper provides an effective and economic method for the similar drainage and interception diversion of rock slopes, internal structures and rock slope reinforcement. [ABSTRACT FROM AUTHOR]

End face caving has always been a major technical problem affecting safe and efficient mining of working face. In this paper, the elastic foundation beam theory is used to establish the differential equation of the end face roof deflection, and the PHASE 2D finite element software is used to establish the numerical model of the end face roof stability, and the influence of coal seam depth, support stiffness, coal body stiffness and other factors on the stability of the backfill mining face end face roof. The results show that :(1) the larger the mining depth or the smaller the hydraulic support stiffness, the more obvious the end face roof subsidence; When the foundation coefficient or elastic modulus of coal seam roof increases, the subsidence of the end face roof decreases, but the influence is limited. Considering the feasibility, improving the stiffness of hydraulic support can effectively control the deformation of working face roof, and reduce the risk of end face roof falling and coal wall sheet wall. (2) When the buried depth of coal seam increases from 200 m to 250 m and 300 m, the plastic zone width and abutment pressure in front of the working face increase significantly, and the maximum subsidence of the direct roof is 61 mm, 78 mm and 96 mm, respectively. (3) When the elastic modulus of coal seam increases from 2 500 MPa to 3 500 MPa and 4 500 MPa, the peak value of abutment pressure in front of working face increases slightly, and so does the width of coal plastic zone in front of working face. The amount of direct roof subsidence decreases slightly. (4) The field observation shows that the support resistance is small under the backfill mining condition, the ore pressure in the working face area is not obvious, and the roof subsidence is effectively controlled. [ABSTRACT FROM AUTHOR]

In cementing operations, oil well cement needs to be mixed with admixtures to improve its performance. The early wet mixing method has shortages of long mixing duration, serious waste of raw materials and heavy environmental pollution, thus pneumatic dry mixing technology has drawn more attention recently. In order to investigate the variation law of mixing uniformity of oil well cement and admixture in dry mixing and determine the optimal operating condition. In this paper, the mixing process of oil well cement particles and admixture particles in the mixing tank is numerically simulated by using FLUENT and Euler-Euler multiphase flow mode. The effects of inlet air velocity, air inlet number, materials loading sequence as well as particle properties on mixing were analyzed. The results show that when the air velocity is too low, oil well cement and admixture unevenly mix. On the contrary, when the air velocity is too large, there will be a concentrated distribution of the particles. For the given case, the optimal air velocity is 1m/s. Moreover, increasing the number of air inlets can not significantly improve the uniformity of particle mixing. When loading the materials, particles with the highest density should not be placed at the bottom layer. The mixing performance is significantly affected by particle density, while particle size has no marked influence on mixing efficacy. [ABSTRACT FROM AUTHOR]

In the actual mining process of open-pit mine, accurate prediction of water inflow at each stage is of great significance to mine safety production. In this paper, the Deziwa open-pit mine in the Democratic Republic of Congo (DRC) is taken as the center to establish the study area. Visual Modflow numerical simulation software is used to describe the boundary conditions and hydrogeological conditions of the study area and simulate the distribution of underground water flow field in the mining area and the surrounding environment. The prediction results show that the established model can better simulate the distribution of groundwater flow field in the study area, and the average water inflow in the third, sixth and tenth years of mining is 12 100 m3/d, 13 400 m3/d and 14 400 m3/d, respectively. At the same time, the groundwater inflow changes with the seasonal rainfall. The water inflow in wet season is about 1.5 times that in normal season, and about 2 times that in dry season. The quantitative analysis of the water inflow in each stage of the mining area can provide a certain scientific basis for the design of drainage in the mining area. [ABSTRACT FROM AUTHOR]

In horizontal or high-inclination well sections, the casing and logging tool usually have downward eccentricity due to gravity, which interferes with the measurement response of azimuthally acoustic bond tool (AABT). The azimuth of the cement channeling cannot be effectively distinguished by AABT under these circumstances. In this paper, the measurement responses of AABT under the conditions of tool eccentricity and casing eccentricity are numerically simulated by a three-dimensional finite difference algorithm. The relationship between the eccentricity distance and the amplitude of received waveform in each azimuth is analyzed, and an azimuth measurement correction method of the cement channeling is proposed. The numerical simulation results show that the tool eccentricity has a great influence on the measurement response of AABT, and it is difficult to directly obtain the azimuth of the cement channeling from the amplitude distribution curve of the first arrival. Based on the response characteristics of the eccentric tool in the free casing condition, the eccentricity effect of the tool can be corrected. The azimuth of the cement channeling can be accurately obtained from the corrected amplitude distribution curve of the first arrival. The influence of casing eccentricity on the measurement response of AABT is quite small and can usually be ignored. The work of this study lays a theoretical foundation for the processing of AABT actual data. [ABSTRACT FROM AUTHOR]

To study the mechanical properties and failure modes of corroded reinforced concrete beams under impact, this paper conducts impact tests on concrete beams by Fujikake et al. The validity of impact force time history curve, mid-span displacement time history curve and failure mode of the fine finite element model of reinforced concrete beam structure established by finite element software ANSYS/LS-DYNA was checked. Based on the verified finite element model, the influence of corrosion rate of reinforcement on the impact resistance of concrete beams was researched. The finite element analysis shows that The concrete spalling degree of concrete member under impact effect increases with the increase of steel corrosion rate. The higher the degree of steel corrosion, the more serious the concrete spalling. All the corroded RC beams at different impact heights exhibit flexural failure characteristics. Steel corrosion has a certain influence on the impact resistance of reinforced concrete members. At the same drop weight impact height, the peak impact force decreases with the increase of steel corrosion rate, and the mid-span displacement increases with the increase of steel corrosion rate. When the impact height is 3.0m, the peak value of impact force decreases to 17.9% and the mid-span displacement is 33.3% when the corrosion rate is 30.0%. [ABSTRACT FROM AUTHOR]

Blending a certain proportion of hydrogen into the natural gas and using the existing natural gas pipelines or pipe networks for transportation is considered to be an effective way of large-scale hydrogen delivery. Because the minimum ignition energy of hydrogen is far lower than that of natural gas, and the lower explosion limit of hydrogen is smaller than that of natural gas, it is more likely to cause explosion accidents after the leakage of hydrogen-enriched natural gas, resulting in serious accident consequences. In this paper, FLACS software is used to study the explosion accident of hydrogen-enriched natural gas in an indoor confined space, and the influence of hydrogen blending ratio, ignition point location, ventilation of computational domain and combustion degree on the accident characteristics and evolution law of hydrogen-enriched natural gas explosion is analyzed. The results show that the higher the hydrogen blending ratio is, the earlier the explosion occurs; The closer to the ignition point, the earlier the temperature and overpressure begin to change in the explosion process; The explosion power of hydrogen-enriched natural gas in the confined space is much greater than that in the open space; The higher the equivalence ratio is, the stronger the explosion power is. [ABSTRACT FROM AUTHOR]

Copyright of Science Technology & Engineering is the property of Chinese Society of Technology Economics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Science Technology & Engineering is the property of Chinese Society of Technology Economics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Science Technology & Engineering is the property of Chinese Society of Technology Economics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)