bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical analysis of the airflow around the Gyro-One autogyro
Authors: Czyż Z , Karpiński P , Skiba K , Siadkowska K
Published: February 2021

The paper presents the results of numerical tests of the aerodynamics of the Gyro-One unmanned autogyro model. The geometry of the research object was developed using reverse engineering and CAD software. The created solid model of the aircraft was entered into the Ansys Meshing to generate a mesh. The boundary conditions and turbulence model were defined with Ansys Fluent software. The calculated parameters include the aerodynamic forces and the pitching moment generated on individual elements calculated with the CFD method for the selected values of the angle of attack, the velocity and pressure distributions in the plane of symmetry, and the pressure distribution on the aircraft surface for the defined measurement points. The obtained results made it possible to analyse the flow around the research object and become an introduction to further research into a hybrid multi-rotor aircraft based on the autogyro design.
Simulation of flames and smoke spreading in an underground garage under different ventilation conditions
Authors: Guz L , Grzesik M , Guz E
Published: February 2021

Garages are significantly endangered by the formation and spread of fire. Additionally, some building equipment or installations located in a garage such as air outlets from ventilation installation could significantly deteriorate the fire situation. To determine the influence of the AHU (Air Handling Unit) outlet inside the garage on fire spreading, a simulation was carried out using the FDS (Fire Dynamic Simulator) in the PyroSim computer software. The investigated underground garage consists of 11 separated parking bays. The following conditions of a fire source were assumed: a car with a petrol engine, a fire area - 10 m2, a range of fire - 12 m, and a total power of fire - 4 kW. The simulations were carried out for two fire scenarios: 1) normal condition (AHU is disabled), and 2) airflow from an AHU outlet (5,200 m3/h). The results show a negative effect of an AHU on fire spreading. The temperature and the concentration of smoke during fire are 2-3 times higher than if an AHU operates. In both fire scenarios, the safe temperature for humans, i.e. 60°C at a height of 2 m above the floor level has been exceeded in less than 4 minutes.
Analysis of the impact of trailing-edge wing flaps on the aerodynamic characteristics and performance of the Diamond DA-20 aircraft
Authors: Smykla I , Kopeć I , Wolski M
Published: February 2021

One of the factors affecting the aerodynamics and performance of aircraft profiles are flaps. The work presents the influence of selected types of flaps on Diamond DA-20 properties. The aircraft aerodynamics is described in detail. Furthermore, the three types of steady flight are presented and the ways of calculating the basic performance of the airplane are taken into consideration. The techniques used to carry out the research are discussed, the conclusions are drawn and the final results are presented. The aim of this article was to analyse the influence of trailing-edge wing flaps on the aerodynamic characteristics and performance of the Diamond DA-20 aircraft. The research focused on the aircraft in smooth configuration and with four types of trailing-edge wing flaps: pop-up, split flap, single-slotted flap and double-slotted flap in 15° and 45° positions.
CFD investigation of the main rotor for an unmanned helicopter
Authors: Królak C , Czyż Z , Siadkowska K , Kliza R
Published: February 2021

The paper presents the CFD analysis of the main rotor of the unmanned helicopter model with a maximum take-off mass of up to 150 kg. The calculations were performed in ANSYS Fluent software. The results of the work are the relationship between the lift force generated by the main rotor as a function of the blade angle of attack. The results are presented for the three considered rotational speeds i.e. 1400, 1600, 1800 rpm. As the angles of the blades of attack increases, an increase in the rotor lift force, torque, and power requirement of the tested main rotor was observed. Additionally, the power required to drive a carrier rotor for the three speeds in question was calculated. Examined changes in the power requirement of the main rotor also showed a percentage increase when changing the α and increasing the rotational speed. The result based on the numerical calculations for three blades main rotor model were presented in tables and diagrams.
Dependence of the heat of combustion of coals on their degree of metamorphism
Authors: Fedorova N I , Mikhaylova E S , Ismagilov Z R
Published: February 2021

The purpose of burning any fuel is to obtain thermal energy, the amount of which is judged by the heat of combustion, their most important thermophysical characteristic. In the modern world, the use of coal as a fuel for the production of heat and electricity leads in terms of consumption. This paper presents the results of measuring the highest heat of combustion of coal in a calorimeter unit. The analysis of the data obtained showed that the value of the highest calorific value depends on the metamorphism stage of coals and their elemental composition.
Physicochemical properties of microcomponents of the Kuznetsk Basin coals
Authors: Fedorova N I , Mikhaylova E S , Ismagilov Z R
Published: February 2021

Coals are heterogeneous in nature, and they most often combine different amounts of three macerals-vitrinite, liptinite and inerinite. Vitrinite, which is responsible for the caking capacity of coal, solubility in organic solvents, mechanical properties, etc., is of decisive importance for the technological properties of coal raw materials. This paper presents the results of a study of vitrinite concentrates isolated from coal of the Kuznetsk coal basin. Using chemical and physicochemical methods of analysis (technical and elemental analyses, IR and 13C NMR spectroscopy, etc.), analytical data were obtained reflecting the change in the composition of their organic mass from the degree of coalification. It was found that with an increase in the stage of metamorphism in vitrinite concentrates, the yield of volatile substances (Vdaf) decreases, the carbon content increases from 82.2 to 88.5% and, accordingly, the content of oxygen and heteroatoms in the organic mass decreases from 11.8 to 6.2%.
Study of the chemical and technological properties of long-flame, long-flame-gas and gas coals of the Kuznetsk Basin
Authors: Fedorova N I , Mikhaylova E S , Gavrilyuk O M , Ismagilov Z R
Published: February 2021

The results of a study of the chemical and technological properties of low-metamorphosed coals of the Kuznetsk basin of long-flame (L), long-flame-gas (LG) and gas (G) technological grades. Coal samples are low-sulfur, medium-ash with a low ash basicity index, are characterized by a rather significant yield of semi-coking resin, gaseous and volatile substances. According to the established technological indicators, these coals can be recommended for energy and technological use, for example, in the process of semi-coking.
Study of the kinetic dependences of the glow and determination of the threshold characteristics of ignition of coals with different stages of metamorphism under the action of microsecond laser pulses
Authors: Kraft Ya V , Aduev B P , Nurmukhametov D R , Ismagilov Z R
Published: February 2021

In this work, the study of the kinetic dependences of the glow and determination of the threshold characteristics of the ignition of coal of grades long-flame, semi-lean caking, weakly caking, lean and anthracite under the action of microsecond laser pulses was carried out. For the aforementioned coals, three successive stages of ignition were found with characteristic Hcr
thresholds. The first stage of ignition is associated with the heating of the surface of coal particles and the ignition of microprotrusions; the duration of the glow practically repeats the duration of the laser pulse. The second stage of ignition is associated with the release and ignition of volatiles in a millisecond time interval; the third-with the ignition of a non-volatile residue, the glow duration reaches 120 ms. With an increase in the degree of coalification, almost constant values of the first ignition threshold Hcr(1) are found. For the studied coals, with an increase in the degree of coalification, a decrease in the second threshold Hcr<2) and an increase in the third ignition threshold Hcr
(3)are observed.
The optimization of preparation mode of metal-carbon catalysts for oxidative desulfurization of diesel fractions
Authors: Matus E V , Efimova O S , Popova A N , Nikitin A P , Sozinov S A , Ismagilov Z R
Published: February 2021

To create new nanosized catalysts for oxidative transformations of sulfur compounds of thiophene series, monometallic catalysts based on carbon nanotubes M/CNTs (M = Ce, Cu, Mo) were prepared with a variation of the synthesis method. The incipient wetness impregnation method, adsorption, and precipitation methods were applied for active component introduction onto CNTs. The effect of preparation mode on textural and structural characteristics of M/CNTs was investigated using a set of physicochemical methods (optical emission spectrometry with inductively coupled plasma, low-temperature nitrogen adsorption, X-ray phase analysis, Raman spectroscopy, and scanning electron microscopy). It was shown that precipitation and impregnation methods provide appropriate metal content in catalyst composition while adsorption is suitable for synthesizing samples with a low active component concentration. The kinds of active component species are similar (CeO2, Cu2O/Cu or MoO3/MoO2) but their distribution behavior and dispersion are controlled by the preparation mode. The using precipitation method for M/CNTs synthesis provides uniform distribution of the nanosized metal-containing particles on the carbon matrix surface.
Study of the porous structure of carbon sorbents based on Kuzbass coal at various stages of metamorphism
Authors: Zykov I. Yu. , Dudnikova Y. N. , Fedorova I.N. , Ismagilov R.Z. , Mikhaylova E. S.
Published: February 2021

The work is devoted to the investigation of the porous structure of carbon sorbents prepared on the basis of long-flame, gas, low-caking and lean coal of Kuzbass. Carbon sorbents were obtained by alkaline activation with potassium hydroxide at 800 °C and a KOH/coal (RKOH) ratio of 0.5 g/g. Using the method of low-temperature nitrogen adsorption (analyzer ASAP-2400), the values of the textural characteristics of carbon sorbents based on coal of different stages of metamorphism were determined: pore volume, micropore volume and specific surface area. It is shown that the carbon sorbents obtained in this work are predominantly microporous (more than 80% by volume). A carbon sorbent based on long-flame coal has the greatest texture characteristics; its specific surface area is 1220 m2/g and a pore volume of 0.54 cm3/g.
Prospects for the use of steam-piston engines to increase the economic attractiveness of environmentally friendly processes for the processing of copper-molybdenum concentrates of promising deposits in Kazakhstan
Authors: Dubinin V S , Stepanova T A , Shkarupa S O , Alekseevich M Y
Published: February 2021

The use of old metallurgical processes is accompanied by releasing process gas into the atmosphere because its subsequent processing is not possible. New technological processes using oxygen flash smelter make it possible to obtain a sufficient concentration of sulfur oxide in process gases for sulfuric acid commercial production. A necessary element of the new type of power plants is heat recovery boilers that generate steam that can be used to generate electricity, which will increase the economic efficiency of oxygen flash smelter plants. The article shows that it is practically impossible to use steam turbines to generate electricity from this steam, and the use of steam-piston engines is proposed.
Study of the features of brown coal by pétrographie analysis
Authors: Fedorova N I , Grabovaya N A , Ismagilov Z R , Mikhaylova E S
Published: February 2021

The paper presents the results of petrographic analysis of five samples of brown coals from the following deposits: Itatskoye, Munayskoye, Arkharo-Boguchanskoye, Kangalasskoye, Baganuur (Mongolia). It was found that the brown coal sample from the Itatskoye deposit (Ro, r = 0.388%) has the lowest vitrinite reflectance, while the brown coal from the Kangalasskoye deposit has the highest reflectance value (Ro, r = 0.490%). An increase in the genetic maturity of the studied samples is associated with a change in the technological properties of their organic matter. It is shown that with an increase in Ro, r, the carbon content (Cdaf) increases, the yield of volatiles decreases, as well as the atomic ratio of H/C and O/C. Visual analysis of polished sections made it possible to determine the maceral composition of the studied coals. The sample of brown coal from the Baganuur deposit (Mongolia) has the highest inertinite content (more than 60%), the sample of the Kangalasskoye deposit contains the largest amount of vitrinite group macerals (86%).
Phase transformations of the nanostructured iron-platinum system upon heating
Authors: Pugachev V M , Zakharov Yu A , Popova A N , Russakov D M , Zakharov N S
Published: February 2021

Joint reduction with hydrazine from aqueous solutions of precursors produced nanostructured powders of the Fe – Pt system in three characteristic phase regions. The samples were subjected to heat treatment in the range up to 800 ° C and characterized at all stages by X-ray diffraction and high-resolution electron microscopy; the elemental composition of the samples was refined by the method of optical emission spectroscopy with inductively coupled plasma. In the initially obtained samples, only a part of the substance is detected by diffraction-the largest, platinum-rich crystals with dimensions of about 10 nm (established from TEM images and broadening of diffraction lines). The fcc-type cubic lattice parameters and the composition of the observed crystals were estimated from the distances between the regular bands in TEM images, identified with atomic rows, based on the composition dependence of the bulk characteristics of mixed iron-platinum phases (according to ICDD databases). In the course of heating, the processes of phase transformation are traced in detail, the parameters of the resulting crystal structures of intermetallic compounds are fixed, and the mechanisms of these transformations are discussed. Based on the measured lattice parameters, the thermal expansion coefficients of some mixed phases are calculated and the phase compositions are estimated at different stages of heat treatment.
Dimethyl ether transformations over copper chromite/alumina catalysts in the packed bed and microstructured reactors: 1. Deep oxidation
Authors: Sukhova O B , Matus E V , Ismagilov I Z , Kerzhentsev M A
Published: February 2021

The deep oxidation of DME in a reactor with a supported catalyst and in a microreactor has been studied. Kinetic dependences of DME oxidation were obtained and comparative results are discussed.
Modeling the propagation of air blast waves in mine workings
Authors: Mazepa E E , Kusainov P I , Krainov A Yu , Lukashov O Yu
Published: February 2021

The article presents a physical and mathematical model of the propagation of air shock waves in the network of coal mine workings after an instant explosion of the methane-air mixture in a given area. An approach to the implementation of a method for solving problems on the propagation of air shock waves in a branched network of mine workings is presented, taking into account arbitrary angles of their conjugation. The results of calculating the propagation of air shock waves in the model networks of mine workings are presented.
Spiral-shaped scattered field from incident evanescent acoustic waves on a Mie Particle
Authors: Alhaïtz Ludovic , Baresch Diego , Brunet Thomas , Aristégui Christophe , Poncelet Olivier
Published: February 2021

We consider theoretically the scattering of an incident evanescent plane wave by a spherical particle. The scattering problem is treated in a classic way by applying the T-matrix formalism and the resulting field is expressed on the basis of the different vibration modes of the particle. Compared to the case of a homogeneous plane incident wave, additional azimuthal scattered modes are excited and their contribution provokes a symmetry breaking of the field. Importantly, if a mode is preferentially excited by choosing the corresponding reduced frequency, the scattered radiation exhibits a spiral structure. The scattered field has a rotating phase around the scatterer which comes from the formation of spiral scattered waves and this effect is accentuated by increasing the evanescence degree of the incident wave. These results could have important implications for the contactless manipulation of objects with acoustic radiation forces and torques.
Measurement of the ultrasonic diffusion coefficient in a resonant multiple scattering suspension
Authors: Delmotte Fanambinana , Brunet Thomas , Clisson Gérald , Leng Jacques
Published: February 2021

We report on frequency-resolved experimental measurements of the ultrasonic diffusivity in the MHz range. By means of robotics, we produced a highly monodisperse suspension made of soft metallic micro-beads randomly-dispersed in a water-based gel-matrix. The measured diffusion coefficient is shown to vary significantly with frequency by more than one order of magnitude that is probably due to the sharp scattering resonances of the metallic particles.
Applications of intensive HIFU simulation based on surrogate models using the CIVA HealthCare platform
Authors: Chatillon S. , Loyet R. , Brunel L. , Chavrier F. , Guillen N. , Le Berre S.
Published: February 2021

High Intensity Focused Ultrasound (HIFU) uses the energy of an ultrasonic beam to cause localized heating to alter or destroy the targeted tissues. Due to its limited collateral effects, this minimally invasive therapy is, in its field of application, an alternative to surgical treatments and is rapidly expanding in terms of both clinical research and industrial development. In this context, the use of simulation is a crucial element to reduce both the development time and prototype costs, as well as the number of preclinical and clinical experiments. To this aim, CEA-LIST has been developing the simulation platform, CIVA HealthCare in partnership with INSERM for several years, which uses optimized and validated modules for the simulation of a whole HIFU therapy protocol. However, multi-parametric studies for treatment optimisation (probe design, protocol definition, etc.), sensitivity analysis, and tissue characterisation are very time-consuming, since they involve many simulations. We propose an alternative solution of replacing the computationally expensive direct solver with a surrogate model built from a database of simulation results. The procedure breaks down into two stages First, the database is adaptively constructed to maximise the fidelity of the associated interpolator computed from the pairs (Input/Output) of the database. Then in the second step, the interpolator, also called surrogate model or metamodel, enables the generation of results in near real time for configurations covered by the range of the database. This procedure and its related tools have been implemented in CIVA-HealthCare. To highlight the potential offered by such intensive HIFU simulation based on surrogate models strategy, two applications are presented: The first concerns real-time pressure field computation, and the second is based on thermal simulations and deals with sensitivity analyses according to uncertainties in tissues parameters. Work supported by French Nation Research Agency (ANR SATURN -15-CE19-0016)
Optimum design for permittivity of dielectric absorbing materials
Authors: Wu Y P , Gao X , Cheng J X , Wen W W , Wang Q B , Zhu Z M
Published: February 2021

In the design of absorbing materials, investigating the ideal value range of electromagnetic parameters under given conditions and adjusting the electromagnetic parameters by existing materials to achieve the ideal range need are two important issues to be solved. Based on transmission line theory and Debye theory, numerical simulations are used to explore the ideal value range of various parameters of absorbing materials under different conditions as well as their selection laws. The Cole-Cole diagram based on combining theory and experiments was given for optimizing design of absorption performance. When the thickness and reflection attenuation rate of the material are presupposed, the real and imaginary parts of the corresponding ideal permittivity should form an approximately elliptic curve. When the permittivity of the material is in the elliptical region, the reflection attenuation rate is lower than its given value. Ellipses with lower reflection attenuation locate in ellipses with higher reflection attenuation, but the centers of the ellipses do not coincide. As the reflection attenuation rate decreases, the corresponding ellipse area shrinks sharply, and the range of electromagnetic parameters becomes rigorous.
Characterization of InSb nanopillars for field emission applications
Authors: Giubileo F , Faella E , Pelella A , Grillo A , Passacantando M , LaPierre R , Goosney C , Di Bartolomeo A
Published: February 2021

A piezoelectrically driven metallic nanoprobe is installed inside a scanning electron microscope to perform local characterization of the field emission properties of InSb nanopillars. The tip-shaped anode can be precisely positioned at sub-micron distances from the emitters to collect electrons from areas as small as 1μm2under the application of an external bias up to 100 V. Current-voltage characteristics are measured for cathode-anode separation down to 500 nm and are analyzed in the framework of the Fowler-Nordheim theory. We give estimation of performance parameters such as the field enhancement factor and the turn-on field and their dependence on the cathode-anode separation distance. We demonstrate the time stability of the emitted current for several minutes. Finally, we perform a finite element electrostatic simulation to calculate the electric field in proximity of the nanopillars and we evaluate the effective emitting area as well as the screening effect due to presence of other pillars in close vicinity. We show that InSb nanopillars are very stable emitters that allow current density as high as 104A/cm2and excellent time stability, crucial characteristics to envisage device exploitation.
The contribution of wildland fire emissions to deposition in the U S: implications for tree growth and survival in the Northwest
Authors: Koplitz Shannon N , Nolte Christopher G , Sabo Robert D , Clark Christopher M , Horn Kevin J , Thomas R Quinn , Newcomer-Johnson Tamara A
Published: February 2021

Ecosystems require access to key nutrients like nitrogen (N) and sulfur (S) to sustain growth and healthy function. However, excessive deposition can also damage ecosystems through nutrient imbalances, leading to changes in productivity and shifts in ecosystem structure. While wildland fires are a known source of atmospheric N and S, little has been done to examine the implications of wildland fire deposition for vulnerable ecosystems. We combine wildland fire emission estimates, atmospheric chemistry modeling, and forest inventory data to (a) quantify the contribution of wildland fire emissions to N and S deposition across the U S, and (b) assess the subsequent impacts on tree growth and survival rates in areas where impacts are likely meaningful based on the relative contribution of fire to total deposition. We estimate that wildland fires contributed 0.2 kg N ha−1 yr−1 and 0.04 kg S ha−1 yr−1 on average across the U S during 2008–2012, with maxima up to 1.4 kg N ha−1 yr−1 and 0.6 kg S ha−1 yr−1 in the Northwest representing over ∼30% of total deposition in some areas. Based on these fluxes, exceedances of S critical loads as a result of wildland fires are minimal, but exceedances for N may affect the survival and growth rates of 16 tree species across 4.2 million hectares, with the most concentrated impacts occurring in Oregon, northern California, and Idaho. Understanding the broader environmental impacts of wildland fires in the U S will inform future decision making related to both fire management and ecosystem services conservation.
Nitrogen -addition accelerates phosphorus cycling and changes phosphorus use strategy in a subtropical Moso bamboo forest
Authors: Li Quan , Lv Jianhua , Peng Changhui , Xiang Wenhua , Xiao Wenfa , Song Xinzhang
Published: February 2021

Ecosystem-level effects of increasing atmospheric nitrogen (N) deposition on the phosphorus (P) cycle and P use strategy are poorly understood. Here, we conducted a seven year N-addition experiment to comprehensively evaluate the effects of N deposition on P limitation, cycling, and use strategy in a subtropical Moso bamboo forest. N addition significantly increased foliar litterfall by 4.7%–21.7% and subsequent P return to the soil by 49.0%–70.1%. It also increased soil acidity, acid phosphatase activity, and soil microbial biomass P, which substantially contributed to a significantly increased soil P availability and largely alleviated the P limitation. This resulted in a significant decrease in the foliar P-resorption efficiency and the abundance and colonization of arbuscular mycorrhizal fungi. Our results indicate that N deposition can reduce plant internal cycling while enhancing ecosystem-scale cycling of P in Moso bamboo forests. This suggests a shift in P use from a ‘conservative consumption’ strategy to a ‘resource spending’ strategy. Our findings shed new light on N deposition effects on P cycle processes and P use strategy at the ecosystem scale under increasing atmospheric N deposition.
Static analysis of PC slab stiffened beam suspension bridge under temperature
Authors: Yang Minghu , chen Lu , Liu Yuancai
Published: February 2021

In view of the influence of temperature on the construction of PC slab stiffened beam suspension bridge, combined with the Moon Bay Bridge, the finite element software Midas Civil is used to conduct a static analysis of the Moon Bay Bridge under temperature. The calculation results can be similar to the bridge construction Provide reference, there is a certain reference significance.
Coupling of SWMM With 2D Hydrodynamic Model for Simulation of Sponge City Construction Scheme
Authors: Fan Yuyan , Wang Chengwen , Yu Haijun , Pan Junhao , Ouyang Zilu
Published: February 2021

Sponge city is a new urban stormwater management concept proposed by China to solve the urban water environment and security problems. The stormwater management model (SWMM) is one of the most commonly used urban stormwater and sponge city simulation models. SWMM is coupled with a two-dimensional hydrodynamic model based on the finite volume method to establish a coupled 1D and 2D hydrodynamic model in this research. The coupled model can simulate the drainage pipe network, sponge measures and flood inundation at the same time. A predictor-corrector method with good stability was used in the coupled model to ensure the non-negativity of the water volume of the 2D model cell. The sponge city construction scheme for a community in Beijing was simulated and analyzed using several design rainstorm processes with different return periods based on the proposed model. It is proved that the coupling model can be applied to sponge city construction problems and sponge measures can reduce the flood inundation and the load of drainage network system by simulating the drainage conditions and ground waterlogging before and after the reconstruction of the drainage community.
Borehole shear test and its application to saturated silty clay
Authors: Zhu Jianmin , Yu Yongtang , Huang Xiaowei , Zeng TAO , Zheng Jianguo
Published: February 2021

An improved borehole shear test (BST) instrument was utilized to obtain the shear strength index of the soil layer in-situ. The results show that the shear strength index of the saturated silty clay measured by the improved borehole shear apparatus has a good linear correlation with the normal pressure, and the correlation coefficient can be greater than 0.98. The testing results were also compared with those obtained by the direct shear test (DST) in the laboratory. It was found that when the soil layer has a depth of less than 8.75m, the difference in the internal friction angle by the BST and DST is small. The former is 8%–33% larger than the latter. The deviation in the cohesion is obvious, which ranges from 20% to 61%. For the soil layer deeper than 8.75m, the situation is different. The difference in the cohesion measured by the two methods is small, which ranges from 8% to 9%, while the difference in the internal friction angle is distinct, and reaches 62%–85%.
Hydraulic Coupling Numerical Simulation of Heterogeneous Rocks with Rrandom Defects
Authors: Yang Yachao , Cui Yongqiang , Song Daifu , Lu Keyu
Published: February 2021

As the research base damage and water inrush problem, this article obtains from the body micro units, on the basis of seepage of rock mass and rock mechanics theory, considering the heterogeneity of rock, and established the heterogeneity of rock containing random defects of mesoscopic scale on the seepage flow in heterogeneous model by means of FLAC3D simulation software built-in fish language from the model unit randomly in the unit ID number, total group as defects in the model group, while the rest of the unit as a complete set, the different group gives different mechanics parameter values, implement different defect degrees of homogenization model established The results show that the overall bearing capacity of rocks with high defect degree decreases obviously, and the failure of rocks precedes that of intact rocks.
Soil Hydrothermal balance in farmland system and its response to human activities
Authors: Dong Xin , Zhang Hengjia
Published: February 2021

The problem of soil hydrothermal balance in farmland system is an important issue to study the formation and change mechanism of farmland climate and microclimate. As an important part of terrestrial ecosystem, the farmland ecosystem has dynamic changes in soil moisture and heat. Due to its particularity, the farmland ecosystem is also a land type directly affected by human activities. This paper systematically summarized the importance of soil hydrothermal interactions in farmland systems, the law of water and heat balance in farmland system and the recent research on the coupling model of hydrothermal balance in farmland system at home and abroad. In addition, this paper also elaborated the research progress of the response of farmland water and heat balance to farmland irrigation, film mulching and other human activities, so as to provide a theoretical basis for the effective use of farmland water resources and the cultivation of high-quality crops in the future.
Study on Tensile Properties and Failure Modes of BFRC
Authors: He Jingjing , Shi Junping , Zhang Yong , Lu Haodan , Wang Haiting , Fan Lihao
Published: February 2021

The effects of basalt fiber volume fraction and fiber length on the tensile properties of concrete are studied by experiments. The mechanism of fiber improving the tensile failure mode of concrete is analyzed. The results show that the tensile properties of BFRC are significantly improved compared with the matrix concrete. The initial crack strength and yield strength increase significantly with the increase of fiber volume fraction, while the initial crack strain and yield strain increase significantly with the increase of fiber length. The roughness coefficient of BFRC fracture surface can be used as the index of fiber improving concrete tensile properties.
Study on suitability of basalt artificial aggregate in Cambodia
Authors: Ge Longjin , Du Bin , Jin Hongjie , Han Xinjie
Published: February 2021

Aggregate property directly affects concrete property. When natural aggregate sources are lacking, artificial aggregates should be considered. The strata in Cambodia are dominated by sedimentary rocks with weaker lithology, which are not suitable for artificial aggregate. The quality of gneiss and limestone is good, but the distribution area is small, so it is not suitable for mass mining. Basalt is widely distributed, and the rock strength is generally high. There are problems such as scattered distribution, poor uniformity, and large property changes. Suitability of basalt artificial aggregate is studied in combination with specific projects. Research works are from outside to inside, from shallower to deeper. Through general survey and primary selection of quarry, surveying and sampling, rock mineral identification and chemical composition analysis, rock physical mechanics test, alkali activity test and aggregate processing property and other analysis tests, its quality indicators and reserves are found out. Studies have shown that quality and reserves of aggregates in the survey yard can meet the needs of the project, mining and transportation are convenient, making it an ideal choice for concrete artificial aggregates. Research methods and results can be used as the reference for similar projects.
Constitutive relation of stiffened square CFST Columns
Authors: Xinzhi ZHENG , Shuang ZHENG , Yuanhong ZHANG
Published: February 2021

Using the constitutive model of a square CFST column with binding bars, the constrained mechanism of the stiffened square CFST columns is analyzed in great detail. The equivalent constitutive model under uniaxial compression is established for square CFST columns. The model is then used to describe the stress-strain curve process for concrete and to calculate the bearing capacity. Models of ten concrete-filled square steel tubular columns under axial compression specimens are created with constitutive relation. The results are compared with the axial compression test of an ordinary square CFST specimen column and stiffened square CFST specimens. Our results show that the bearing capacity and stress-strain curves under axial compression are consistent with the actual test measurements. Analysis can be applied to the square stiffened CFST columns, the square CFST columns with binding bars, and the ordinary square CFST columns.
Study on highway dynamic load vibration propagation characteristics in surrounding soil and influence control distance
Authors: Zhang Yuqi , Guo Xiaohong , Wang Ning , Qiao Maowei
Published: February 2021

The dynamic monitoring for the scene of the engineering vehicle dynamic load of the vibration was performed. By developing a subroutine of ABAQUS DLOAD to simulate the process of vehicle traffic, the characteristics of vehicle vibration transmission in soil was analyzed. Based on three different indicators: displacement, acceleration and vibration level, the influence of different speeds and different weights of the vehicle vibration on the surrounding soil and reasonable control distance was analyzed. This paper provides reference and guidance to avoid the influence of traffic dynamic load when designing and constructing.
Simulation and crack analysis of the whole process of a Roller Compacted Concrete dam during construction and operation
Authors: Ding Jianxin , Yang Qingzhou
Published: February 2021

The structural safety calibration is an essential problem of Roller Compacted Concrete (RCC) dams. Due to the simulation complexity of RCC dams and shortcomings of conventional methods, usually, the actual mechanics state cannot be obtained easily by the numerical methods. In this paper, a RCC gravity arch dam in Laos is taken for an example, the simulation program has been developed, and three-dimensional simulation analysis of the temperature field and stress-strain field of the whole process of RCC dam during construction and operation is carried out. The composite contact crack element is proposed to simulate the complicated mechanical behaviors of various kinds of joints and cracks. The research results show that the simulation results of the temperature field, the stress-strain field and cracking are close to the monitoring data, the space-time evolution of the temperature field and the stress-strain field of the RCC dam are obtained. The whole working state of the RCC dam is evaluated, and the causes of the dam cracks are revealed. The research results are adopted by the design institute, which is of great importance to ensure the engineering safety of design, construction, impoundment and operation.
Research on the Efficiency Path of Civil Construction Management Engineering Based on BIM Technology
Authors: Duan Rongrong
Published: February 2021

My country’s economic pillar industry is the civil construction industry. With the rapid development of our country, modern buildings have greatly increased the difficulty of construction project management due to complex construction techniques and long construction periods. Therefore, we must improve the traditional. In this way, the management model can better improve engineering efficiency. This article is based on the BIM technology of the civil construction management engineering efficiency path to study, the experiment uses the analytic hierarchy process to determine the weights, in order to evaluate the BIM technology of construction engineering safety management. Three local survey units were selected for the experiment, and the survey form was distributed to each unit according to the experimental procedures and requirements. When handing over the BIM model, it could give the acceptance conclusion of the model. Experimental data shows that the incidence of accidents at the entrance of the cave and the border is the highest, which is the most difficult point in construction safety management. Effective measures should be taken to reduce the occurrence of accidents. The experimental results show that the following problems in BIM application have led to a reduction in the efficiency of civil construction management engineering: 85% of BIM standards are unfamiliar, 79% of BIM technology costs are overused, BIM technology is poorly applied 82%, and BIM-related software is not applied. Mature accounted for 78%, and BIM related management methods accounted for 80%. The use of BIM technology can provide an effective way to improve the efficiency of construction project management. This article conducts in-depth research on BIM technology, hoping to make a meager effort in related fields.
Influence of Molding Methods on the Polymer Pervious Concrete
Authors: Li Wenqiang , Chen Fan , Ai Zubin , Zhang Chao , Wang Chao , Li Yue , Zhang Yankun
Published: February 2021

The influence of vibration molding method and manual poking molding method on strength and water permeability of polymer pervious cement concrete with water cement ratio of 0.27, 0.30 and 0.33 is studied. It is found that the compressive strength of vibration molding increases with the increasing of vibration time and the water permeability coefficient decreases. The strength of concrete with vibration molding is higher than that of manual poking molding, and the water permeability coefficient is lower. However, the water permeability coefficient with both molding methods is more than 0.5mm/s.
Analysis of the influence of lately excavated tunnel blasting on the vibration of early excavated tunnel in small-space tunnel
Authors: Luan Guitao , Wang Zhirui , Song Zhanping , Yu Haibao
Published: February 2021

In order to study the impact of the blasting construction of lately excavated tunnel of the large-section tunnel with small spacing on the early excavated tunnel, the propagation law of vibration velocity of initial support of early excavated tunnel under blasting load is analyzed by combining field test and numerical simulation based on the Mongol Road Tunnel of the Zamalong-Daotanghe Highway Reconstruction and Expansion Project in Qinghai Province; The results show that the radial vibration velocity in the initial support of early excavated tunnel is obviously greater than the vertical vibration velocity and tangential vibration velocity in the blasting construction of lately excavated tunnel with large section and small spacing. The radial vibration velocity of the blasting side of the tunnel is obviously greater than that of the back side, and the maximum is found at the arch waist of the blasting side. The peak value of the radial vibration velocity of the initial support of early excavated tunnel is the maximum at the same section position as the blasting excavation face, and gradually decreases with the increase of the blasting center distance. Compared with the vibration velocity of the initial support before and after the excavation face, the peak attenuation rate of the vibration velocity in front of the blasting excavation face is slightly less than that behind the excavation face.
Study on the effect of resistivity and meso-structure evaluation of alkali solution strengthening loess: A case study
Authors: Hu Wenle , Liu Hua , Wang Tiehang
Published: February 2021

For evaluating the structure and strength of loess effectively, a series of laboratory tests were performed to investigate and compare the pore meso-structural characteristics, the shear strength and the resistivity of natural loess and loess treated with alkali solutions under 4 different concentrations. Scanning electron microscope(SEM) method, direct shear tests, electrical resistivity tests, and X-ray diffraction analysis were used to detect the changing process in strength parameters, micro-structure, and mineral composition. The evolution result of shear strength index and stress-strain characteristics of loess were analyzed. Combined the SEM micro-structure analysis and X-ray diffraction technology, the microscopic mechanism of alkali solutions and loess interaction was revealed. The results of tests show that the curves of shear stress- displacement featured as strain-hardening, and the increasing of shear strength indexes with the increasing of alkali solutions concentration. Then the relationship between the shear strength index and resistivity was established. The SEM images of LTA specimens were used to quantify the structural parameters by Image Processing Techniques. The changes of multiple structural indicators of LTA such as directionality, abundance, circularity, fractal dimension, and the orientation probability entropy were revealed. The potential mechanism of LTA was revealed by the XRD and EDS tests from the perspectives of mineral composition and chemical element composition. The results of this study show that alkali-loess interaction was the main influence factor for the changes in the shear strength and meso-structure s. The results provide a valuable implication for the construction in the loess deposits.
Study on Signal Processing of IES of Tunnel Lining Based on Wavelet Analysis
Authors: Li Ruijun , Shi Yaqing
Published: February 2021

As we all know, high-speed rail is a very important business card in China, and the rapid development of high-speed rail is inseparable from the rapid development of tunnel construction, so tunnel construction has become very important. The quality of the tunnel lining directly affects the construction quality of the entire tunnel construction. This paper first introduces the use of IES, one of the most advanced testing methods for non-destructive testing, to achieve non-destructive testing the quality of tunnel lining. The signal is more or less affected by the surrounding environment and human factors, so In this paper, wavelet analysis is used to eliminate the signal noise in order to extract characteristic signals that better reflect the defects of tunnel lining and realize the intelligent diagnosis of the defects of tunnel lining.
Eccentric compressive behaviour of double steel-concrete shear wall constrained with ribs and bars
Authors: Xinzhi ZHENG , Shuang ZHENG , Songbiao LI
Published: February 2021

By adding ribs and bars to form the double steel-concrete shear wall constrained with ribs and bars, the steel plate of the whole steel-concrete shear wall can be strengthened of the constraint. The research on Eccentric compressive behavior of double steel-concrete shear wall constrained with rib and bar is less, this paper analyzes double steel plate concrete shear wall by using larger length-width rectangular CFST column research methods. Based on the constitutive relation of the rectangular CFST column with ribs and bars, the relative parameters are changed, and a program is written to compare and analyze eccentric compressive behavior of double steel-concrete shear wall constrained with ribs and bars compared with that double steel plate concrete shear wall only constrained with bars.
Study on the influence of surrounding rock parameters on the stability of tunnel face
Authors: Wei Xiaohang , Sun Ze , Wang Zheng , Zhuang Dequan , Ba Wenwen
Published: February 2021

The surrounding rock is the construction environment and main load source of the tunnel, and its physical parameters have an important influence on the stability of the tunnel face. Based on orthogonal test method, with the Georgia E60 highway 3.0.04 - TA tunnel under construction as the engineering background, numerical test method is used to compare and analyze the influence of different surrounding rock parameters ( elastic modulus E, cohesion C, internal friction Angle φ) on the stability of tunnel face. The multiple linear regression fitting equations of three factors and extrusion deformation are given and verified. The results showed that the elastic modulus and cohesion of surrounding rocks had a significant influence on extrusion deformation of the tunnel face, while the internal friction Angle had no significant influence. The extrusion deformation of the tunnel face is negatively correlated with the elastic modulus, cohesion and internal friction Angle of surrounding rocks. The fitting equation can provide a means for predicting the stability of surrounding rock and guide the construction of the tunnel.
Study on the supporting time of the secondary lining of the highway tunnel with weak surrounding rock
Authors: Feng Jiaqing , Wang Xiaoming , Zhou Yongxing , Liu Guofeng , Liu Kaide
Published: February 2021

Based on the Dongxiu tunnel project of Liyu highway under construction in Guangxi province of China, this paper attempts to study the supporting time of the secondary lining of the highway tunnel with weak surrounding rocks. Firstly, the measurement data of typical section of the tunnel is fitted and used to reveal the evolution law of the settlement of the tunnel vault and peripheral convergence of the sidewall. Then the three-dimensional simulation is carried out to verify the rationality of the evolution law. After that, the supporting time of the secondary lining is determined relying on the results of field monitoring and numerical simulation. The results show that, both the settlement of the tunnel vault and the peripheral convergence for the Dongxiu tunnel can be characterized by exponential function, and it is reasonable to construct the secondary lining at 24th-25th day after excavation. The results can not only guide the subsequent construction on site but also provide reference for the determination of supporting time of the secondary lining of similar tunnel projects.