bluuebunny/crossref_metadata_2025 huggingface dataset:
Mathematical modeling and analysis of conditions for the robot’s uniformly accelerated motion along a straight rail track, taking into account the delay intervals
Authors: Lyubimov V V
Published: May 2021

The problem of the straight-line motion of a robot along a rectilinear rail track with the constant acceleration with delay intervals is considered. The aim of the paper is to determine and analyse the conditions describing the straight-line uniformly accelerated motion of the robot, taking into account the delay intervals. The law of speed change of the robot is simulated, using linear piecewise continuous functions of the time of motion. The necessary conditions for the uniformly accelerated motion of the robot in the acceleration and deceleration sections are formulated. Additionally, the criteria for uniformly variable acceleration and deceleration in the straight-line motion of the robot without delay intervals are recorded. It should be noted that the conditions and patterns presented in this paper have many practical applications. For example, they can be used in the development of traffic routes or in the operation of railway trains.
Solving logistics on the basis of fuzzy package
Authors: Muhamediyeva D K , Mirzaraxmedova A X
Published: May 2021

The article discusses an approach to solving a logistic problem based on fuzzy set theory. The classic fuzzy control module is developed at the node of the transport network, as well as when solving the problem of modeling the traffic control strategy in the network. An ambiguous rule base was developed for defining traffic control parameters at a transport network node, and rules were proposed for mapping a control parameter to a specific class and fuzzy rule base.
Modelling and presentation of cyber-physical systems on the morphological approach basis
Authors: Rakov D L
Published: May 2021

The article discussed cyber-physical systems are considered as a logical evolutionary stage in the development of system theory and system analysis. Cyber-Physical systems are a complex of interacting computational and physical components, with a constant exchange of information with the environment. The computational component can be easily changed and adapted to changing environmental conditions. At the same time, the re-construction of physical elements causes certain difficulties and already at the stage of conceptual design, they should be able to adapt to changes in the environment. Their use will allow you to achieve many advantages in the creation, management and operation of complex systems. These systems are highly adaptable in response to environmental changes, which leads to increased efficiency, are adaptable and transformative, and contribute to increased efficiency. The aim of the research was to find the position of cyber-physical systems in the general theory of systems. Morphological analysis was used for justification and selection, and it is proposed to use agglomerative clustering. The morphological representation made it possible to clearly determine the place of cyber-physical systems and to obtain a morphological set of possible variants. The creation of a classification morphological matrix will increase the accuracy of identification of these systems. For the first time, a morphological classification of cyber-physical systems as subsets of complex systems is given.
On generic complexity of the problem of searching of isomorphism for finite semigroups
Authors: Rybalov Alexander
Published: May 2021

This article is devoted to the investigation of generic complexity of the problem of searching of isomorphism for finite semigroups. That problem can be formulated as follows. For any pair of isomorphic finite semigroup Si and S2 with elements {1, 2,…, n}, represented by its multiplication tables, we need to find a bijection (permutation) of the set {1, 2,…, n}, which implements an isomorphism between S1 and S2. As for the classical isomorphism problem, any polynomial (even probabilistic) algorithms are unknown for the problem of searching of isomorphism for finite semigroups. We construct natural subproblems of this problem, for which there is no polynomial generic algorithm, provided that this problem is hard in the classical case. The study was carried out within the framework of the state contract of the Sobolev Institute of Mathematics (project no. 0314-2019-0004).
Formation of informative signs for predicting the disease of highly productive cows with non-communicable diseases
Authors: Safarova L
Published: May 2021

In this article, fuzzy set membership functions have been developed based on the main factors (clinical, morphochemical, rumen contents) to predict the following non-communicable diseases such as ketosis, osteodystrophy, secondary osteodystrophy and hypomicroelementosis in high-yielding cows. The results of the study show the high efficiency of the proposed decision-making algorithm for forecasting, classifying and measuring poorly formalized processes, that are described by fuzzy models. The available knowledge about the existing experimental data makes it possible to increase the adequacy of the fuzzy expert system.
New approaches to constructing quadrature formulas for functions with large gradients
Authors: Zadorin A I
Published: May 2021

The problem of numerical integration of functions with large gradients in the boundary layer is studied. The use of the Newton-Cotes formulas on a uniform grid to integrate such functions can lead to significant errors. The article investigates approaches to the construction of quadrature formulas, the error of which does not increase due to large gradients of the function in the boundary layer. The following approaches are considered: the construction of quadrature formulas that are exact on the singular component responsible for the growth of the function in the boundary layer, the application of the Newton-Cotes formulas on the Shishkin and Bakhvalov meshes, minimization the error of the quadrature formula due to the construction of nodes. The investigated approaches are new, partially reflected in the publications. The results of computational experiments are presented.
Development and application of the geometry constructions language to building computer geometric models
Authors: Boykov A A
Published: May 2021

Geometric models for industrial purposes are created in CAD systems making use of geometric constructions commands. At the same time, the so-called constructive or synthetic (as opposed to analytical) method to create a geometric model is implemented. The set of tools of any CAD system is limited, so accomplishing a specific task will require repeating a series of geometric constructions of the same type to form the desired shape. In this paper, a specific GC language (Geometry Constructions Language) is proposed to introduce an automated process of geometric modeling. To do this, theoretical issues of constructive geometry are analyzed, the main objects and syntax of the GC language are identified. The paper provides an example of building a model of a temple dome using GC language translator. It is noted that the GC language allows geometric modeling of regular curves (including trajectory of objects) and surfaces and applying new geometric correspondences and transformations. At the same time, geometric models in CAD systems are created faster since you don’t have to repeat manually the same type of construction or develop new equations and formulas for calculations.
Predictive geometric models for some hygienic properties of multi-component fabrics
Authors: Chizhik M A , Yurkov V Yu , Dolgova E Yu
Published: May 2021

This paper is devoted to the geometric and computer simulation of hygienic properties of fabrics which are considered as multi-parameter and multi-component systems. We consider predictive models of fabric hygroscopicity and air permeability. There is a problem of building co-ordinate geometric models on condition that the set of experimental data is limited. We solve the problem for static multi-component systems. All models are considered as monoidal surfaces in the space of input and output parameters. The paper proposes an algorithm of building linear and quadratic models of fabric properties. Results of the investigations allow us to substantiate producer’s choice of fabric construction and composition for manufacturing the clothes of special purpose. The method suggested in the paper is one of geometric modulus of the software HYPER-DESCENT which has been developed formerly. Our geometric models together with software HYPER-DESCENT may be applied for simulation and prediction the properties of multi-parametrical systems or technological processes of light industry.
Graphic modelling of the gear broaching process
Authors: Kondrashov A G , Safarov D T
Published: May 2021

The gear broaching method, in contrast to the hobbing methods with hob cutters, belongs to the shaping copying methods. The result of the gear broaching is a gear profile that is geometrically different from the theoretical design profile of the bevel gears. The possibility of graphical modeling of the results of the gear broaching process is currently absent, which makes it impossible to measure the geometric parameters of the rims of the gear wheels after their processing. The article proposes a method for graphical modeling of the process of gear broaching of bevel gears, including the construction of actual profiles of the broaching teeth, the adjustment scheme of the gear broaching machine, obtaining a family of trajectories of movement of each broaching tooth, aligning and stretching the profiles along the trajectories to obtain shaping elements. Subtraction of the shaping elements from the gear blank model produces a geometrically accurate 3D model of the bevel gear, which is the result of the interaction of each broach tooth and the blank.
Principles of solid modelling in point calculus
Authors: Konopatskiy E V , Bezditnyi A A , Lagunova M V , Naidysh A V
Published: May 2021

The article describes the principles of solid modelling in point calculus, including the definition of geometric bodies in the form of an organized set of points in space. At the same time, the choice of point calculus as a mathematical apparatus for effective modelling of geometric bodies in 3-dimensional space is substantiated, expanding the instrumental capabilities of computer graphics. By means of generalization, it has been established that the dimension of the space in which the geometric body is defined is equal to the number of current parameters. On the basis of this, a new definition of a geometric body is proposed as a geometric set of points, in which the number of its determining parameters is equal to the dimension of space. Examples of the definition of a tetrahedron body and a triangular prism body in point calculus, obtained considering the proposed definition of the term “geometric body”, are given. The obtained point equations are completely invariant with respect to the choice of the coordinate system and depend only on the coordinates of the points that define the vertices of the modelled bodies. Thus, the obtained point equations determine the entire set of bodies of tetrahedrons, bodies of triangular prisms, bodies of elliptical cylinders and cones in 3-dimensional space. The prospect of further research is the definition in point calculus of geometric bodies of curvilinear and irregular shapes, considering their relative position in space, as well as more complex composite geometric bodies in 3-dimensional space.
Simulation of a cylindrical-conical gear train on parallel axes with an adjustable side clearance
Authors: Krukov V A , Nam T V , Plyasov A V
Published: May 2021

The geometrical synthesis of a cylindrical-conical transmission on parallel axes with external gearing is considered on the basis of the blocking contour method, which makes it possible to determine solutions for the right and left ends of the wheel. The use of the calcula-tion for cylindrical-conical wheels is described. We used our own algorithm for constructing the blocking contour and engagement in the Math CAD program, and a 3D model of the trans-mission in the KISSsoft program. For a better example, the contour and engagement in the 3D model are given.
Supercapacitors application possibilities for lifting equipment induction electric drives
Authors: Lysenko O A , Simakov A V
Published: May 2021

In the article, the supercapacitors (ionistors) application for lifting equipment induction electric drives is considered. Electric lifting equipment is widely used in industry, construction, municipal services. The lifting equipment efficiency is insufficient, therefore the research topic is relevant. At the moment, an induction electric motor with a frequency converter with a DC link is used to regulate the mode of lifting and lowering loads. To smooth out the ripple and use the braking energy of the moving masses when lowering the load, it is proposed to use a supercapacitor as a DC bus storage. A supercapacitor has three to four degrees more capacity than an electrolytic capacitor and can store more electricity. The paper provides simulation modeling of the electric drive of the lifting equipment. Stern’s equation is used as a supercapacitor mathematical model. According to the simulation results, the power consumption of an electric drive with a supercapacitor is 41.02% less than that of an electric drive with an electrolytic capacitor.
The three-level inverter topologies analysis for application by electric centrifugal pump units
Authors: Lysenko O A , Simakov A V
Published: May 2021

In the article, the schemes for providing AC power with frequency conversion for the induction submersible electric drive of oil production units are analyzed. The electric submersible drive is widely used and has stringent efficiency requirements, so this research is relevant. The centrifugal pump units are composed of a low-voltage power source, a frequency converter, a step-up transformer, a cable line, an electric drive and a centrifugal pump. This article discusses options for replacing the step-up transformer and two-level voltage / frequency converter with a three-level flying capacitor converter (FCC) or a three-level clamping diode converter (NPC). The expected states of the power high voltage IGBT modules are described. The waveforms of the inverter output voltage and the submersible induction motor stator voltage in different circuits are shown. A voltage levels analysis for each module is done, the electric drive starting time change is estimated, the total harmonic distortions (THD) are calculated, and a 1.1% THD reduction by applying the NPC circuit is shown. The harmonic current spectrum for each circuit is presented.
Determination of conditions for optimal control of a permanent magnet synchronous motor of a single-stage reciprocating compressor for a proposed law of motion for ensuring the maximum efficiency
Authors: Tatevosyan A A
Published: May 2021

Attention is paid to issues of reliability and economy while ensuring high performance of energy conversion processes occurring in various subsystems when a linear magneto-electric drive (LMED) is designed, which includes a permanent magnets synchronous motor with permanent magnets (PMSM) and a compressor stage. Reducing the number of elements included in the LMED, for example, transmission and conversion mechanisms is one of the directions that increase the reliability of the LMED. However, in this case, non-linear suction-discharge processes occurring in the compressor stage have a significant effect on the operation of the electromechanical converter. In this regard, the task of improving the energy efficiency of LMED can be solved in various ways. The article describes the LMED control conditions of a low-speed single-stage piston compressor, obtained from the solution of the problem of optimizing the design of the magnetic system PMSM, at which maximum efficiency is achieved. The relationship of the generalized parameters of the drive with the design features of the PMSM is established.
Effect of the noise component of the aperture uncertainty on the dynamic range of the sample and hold circuit
Authors: Zhenatov B D
Published: May 2021

In this article, the influence of the noise component of the aperture uncertainty on the dynamic range of the sample-and-hold circuit (S/H circuit) is considered. For this purpose, a mathematical model of the S/H circuit is constructed, which is presented in the form of an ideal sampler, at the input of which a functional block is placed that simulates distortions of the sampled oscillation in the real S/H circuit. An analytical expression is obtained to show that the noise component of the aperture uncertainty generates frequency distortions of the input signal and additional noise, the properties of which are determined by the characteristics of the aperture uncertainty and the sampled oscillation.
Tensile modeling of titanium-aluminum composite with a wave profile of a welded joint and local melts
Authors: Gurevich L M , Danenko V F , Pronichev D V , Pisarev S P
Published: May 2021

Finite element simulation of tensile deformation of titanium-aluminum composite D20 – AD1 – VT6 was carried out. The joint boundary had a wave profile and local melts. 3D modeling of deformation of the composite D20 – AD1 – VT6 with a wave profile of the welded joint was carried out using the SIMULIA / Abaqus software. The relative thickness of the AD1 interlayer and the area of the melt were varied during the simulation. To determine for metal hardening during plastic deformation and the failure deformations for aluminum and aluminum alloy both Johnson-Cook deformation and fracture models was used. The influence of the size of the local melting zone and thickness of the soft interlayer on the distribution of stresses and strains in the composite is shown. The wave profile of the boundaries junction leads initially to localization of plastic deformation in the aluminum interlayer in the zone of free surfaces of the sample near the interface with the titanium alloy. A change in the length of vortices with areas of local melting near the tops of the wave profile from 0.3 to 0.8 mm had little effect on the profile of the curves “equivalent stress-absolute elongation of the sample”.
Using the finite element method and dimension analysis in modelling laser shock processing of titanium alloys with shape memory
Authors: Sakhvadze G Zh
Published: May 2021

The technology of laser shock processing of titanium alloys with the shape memory effect is simulated using the finite element method and dimensional analysis. In total, 16 independent dimensionless parameters characterizing the mechanical behavior of shape-memory NiTi alloys are analyzed. The dependences of the influence of the dimensionless duration of the laser pulse and the dimensionless peak pressure in the shock wave on the dimensionless depth of the plastic zone are obtained.
Comparison of titanium nitride and high-entropy coatings on parts of industrial plants
Authors: Yurov V M , Eremin E N , Guchenko S A
Published: May 2021

The task of the work is to establish a relationship between the main parameters of high-entropy CuZrTiNiCr coatings and their mechanical properties on parts of industrial enterprises with classic titanium nitride coatings. The technique is based on the use of mechanical alloying methods for the synthesis of high-entropy alloys and the production of magnetron targets from them. The application of titanium nitride coatings and high-entropy CuZrTiNiCr coatings on the parts was carried out on an NNV-6.6I1 installation. Establishment that high-entropy CuZrTiNiCr coatings have a density of 5.72 g/cm3, and the density of titanium nitride coatings is 5.44. The microhardness of high-entropy coatings is 14.1 GPa, while for titanium nitride coatings it varies over a wide range 20.2 GPa. The friction coefficient of titanium nitride coatings changes 0.4-0.5, which is 10 times higher than that of the high-entropy CuZrTiNiCr coating-0.04. This antifriction property of the high-entropy coating on the parts of industrial enterprises leads to greater wear resistance and a longer service life, in comparison with classical titanium nitride coatings. Titanium nitride coatings on industrial parts were found to be 10 times less effective than high-entropy CuZrTiNiCr coatings. This is due to the wear resistance of these coatings, which is due to the very low coefficient of friction and low surface energy.
Cell constant analytical study of electrochemical flow cell with interdigitated microelectrodes
Authors: Kozlov A G , Fadina E A
Published: May 2021

This paper presents the results of investigating the influence of design parameters of an electrochemical flow cell based on film interdigitated microelectrodes on its cell constant. This investigation is performed by the analytical method. To determine the cell constant the linear resistance between the adjacent fingers of the interdigitated microelectrodes is used. In its turn this resistance is found from the potential distribution in the unit subdomain of the interdigitated microelectrode system of the cell with the limited height. The dependencies of the cell constant on the cell height and the design parameters of the interdigitated microelectrode system (the spacing between fingers and the finger width) are determined. The cell height at which the change of the design parameters of the interdigitated microelectrode system has the least effect on the cell constant is found.
Simulation of chemical composition nitrogen-argon-aluminum plasma
Authors: Strunin V I , Khudaibergenov Zh G
Published: May 2021

Plasma-chemical model of magnetron discharge is described. The model allows you to predict the densities of the main plasma components. As a result of numerical modeling, it was found that dissociation of N2
ranges from 10% to 30% with an increase in plasma power, the degree of dissociation increases. The addition of N2
to the plasma leads to a decrease in ion density due to energy consumption for non-ionizing molecular collisions. It can be assumed that aluminum nitride is deposited on the surface of a substrate with a high flow of metal ions in combination with a stream of neutral molecules N2 with a low adhesion coefficient and a relatively small flow of nitrogen ions.
Application of the Herts equation for calculating the parameters of the elastic-plastic central impact of two solid deformable bodies
Authors: Chernyavsky D I , Chernyavsky D D
Published: May 2021

The study of the dynamics of mechanical impact of solid deformable bodies is an urgent problem in mechanics. This problem is associated with the strength calculations of machine parts and mechanisms. The most difficult case is the strength calculation under shock and vibration loads. Exact mathematical equations are obtained only for simple structural elements of machines: balls, rods, plates, beams, etc. The mathematical description of the dynamics of elements of machines of complex shapes under impact conditions is seriously difficult. A method of dynamic strength analysis of machine parts using the Hertzian contact theory is proposed. For the cases under consideration, the impact velocity of two bodies does not exceed 100 m / s.
To the development of the theory of contact interaction in two-roll modules
Authors: Khurramov Sh R
Published: May 2021

The results of the study of the stress-strain state in a two-roll module are presented. The angles that determine the characteristic points of the physical model of the roll contact curves are defined for the case when the strain properties of the material layer and elastic roll coatings are given by power dependences. Formulas are derived for calculating the angles of entering and exit, the angles separating the no-slip zones from the lag and advance slip zones, neutral angles and angles of maximum normal stresses of the two-roll module. It was stated that an increase in the friction coefficient of the roll with the material being processed leads to a decrease in the percentage of slip zones in the contact curve in the driven roll. It was revealed that with an increase in the dynamic coefficient, the slip lag zone decreases, and the advance slip zone increases. It was determined that the faster the feeding rate of the material layer, the greater the percentage of the no-slip zone in the roll contact curve. It was revealed that in the driven roll the neutral angle is inclined towards the entrance of the material layer into the contact zone of the rolls.
A quaternionic description of kinematics and dynamics universal joint
Authors: Mityushov E A , Misyura N E
Published: May 2021

The purpose of the work is figuring out the kinematic and dynamic equations of u-joint motion in the quaternion parametrization. The quaternion description of u-joint kinematics allowed us to formulate the claims about the crosspiece angular velocity projections. We’ve also determined the principle point projection acting on the crosspiece by solving the inverse problem from Euler’s dynamic equations with the found driving shaft’s angular velocity and the inertial crosspiece characteristics.

The modeling results are verified in the computer software-Mathcad and can be used for creating optimal u-joint designs by changing its geometry.
Kinematics of elements of a spherical ball bearing suspension
Authors: Raspopov V Ya , Telukhin S V
Published: May 2021

The kinematic constraint equations of elements of a spherical ball bearing suspension, separator and balls are considered. Based on the equation of motion of the separator and the balls, the angular coordinates of the separator and the trajectory of the centers of mass of the balls relative to the bearing surfaces are determined. Analytical expressions for determining the parameters of the separator and the balls motion are obtained for different ratios between the velocities of rotation of the rotor mounted on the outer ring and the inner ring of the suspension.
Construction project cost estimation model cost dependent on multi-objective fuzzy optimization calculation
Authors: Xu Jing , ye Meiying
Published: May 2021

With the development of the social economy, the number and scale of construction projects are also growing. How to control construction project costs has become the key to investment and construction. Based on the multi-objective fuzzy optimization computing, the completed project investment data in the actual project progress is used for empirical analysis of a construction project using the cost prediction model.
Comparative Analysis of Hydration Expansion Performance of Desulfurized gypsum-baseda/β Gypsum
Authors: Zhang Jixiu , Zhang Ye , Miao Yuanchao , Duan Saihong
Published: May 2021

Gypsum has micro-expansion characteristic during the process of hydration and solidification, and there are certain differences in the hydration expansion characteristics of different types of hemihydrate gypsum. In this paper, by analysing the gypsum crystal morphology, particle size distribution, hydration heat, dimensional change rate, and morphology change of hydration products in the process of hydration process, the hydration expansion performance of α/β gypsum are compared and discussed. The results indicate there are differences in the hydration swelling mechanism between α-gypsum and β-gypsum. The expansion of gypsum is the result of the combined effect of the crystal transformation and the release hydration heat during the hydration process. The particle size distribution and the amount of hydration water added have a great influence on the expansion performance.
Effect of Hybrid Fiber on Early Mechanical Properties of High Performance Concrete
Authors: He Tusheng , Chen Qidong , Li Zaibo , Liu Yang , Zhao Sanyin , Zhao Xuguang
Published: May 2021

The early mechanical properties of hybrid fiber reinforced concrete were studied by orthogonal test, the factors of steel fiber content, polypropylene fiber content and length on compressive strength and splitting tensile strength of concrete for 3 d ages were investigated, the test results were analyzed by range analysis, variance analysis and performance index analysis. The results show that the hybrid fiber has a negative hybrid effect on the compressive strength of concrete for 3 days, a positive hybrid effect on the splitting tensile strength of concrete for 3 days. When the volume fraction of polypropylene fiber is 0.1%, the length is 12mm, and the volume fraction of steel fiber is 1.5%, the compressive strength of concrete is the largest. When the volume fraction of polypropylene fiber is 0.15%, the length is 18mm and the volume fraction of steel fiber is 1.5%, the splitting tensile strength of concrete is the largest.
Study on the Selection Principles of Building Sealant in AAC External Wall
Authors: Zhang Ye , Zhang Jixiu , Miao Yuanchao , Duan Saihong
Published: May 2021

With the vigorous development of prefabricated buildings in China, the maturity of assembly technology, the matching of materials and the professionalism of construction have become the focus of attention. As the most important lightweight wall enclosure material, the sealant for autoclaved aerated concrete (AAC) wall plays a major role in the joint sealing of the wall. In this paper, on the analysis of related standards and the application characteristics of sealants, the requirements of sealant for AAC external wall are discussed and summarized. The requirements include good compatibility and adhesion with the substrate, low modulus and high displacement ability, environmental protection, good weather resistance and paint ability (when there is painting demand for the joints).
Water expansion performance standard for cement stabilized phosphogypsum soil
Authors: Peng Bo , Zhang Jing , Peng Jing-wen
Published: May 2021

The application of cement stabilized phosphogypsum soil (CSPS) in highway engineering has great economic and social benefits. There are few corresponding classification standards for water swelling during long-term use and so a test method for water swelling of CSPS is designed. Unconfined compressive strength (UCS), dry shrinkage (DS), and temperature shrinkage (TS) of CSPS at three cement contents and eight phosphogypsum (PG) contents were measured. This paper analyzes the reasons for the poor early mechanical strength of CSPS. Based on the water expansion tests, ultimate expansion without load (δe) is proposed as the evaluation index for water expansion. Combined with the relationship between the shear strength of the CSPS after the termination of water expansion, δe, and PG content, a water swelling classification standard for CSPS is established. The results show that be is negatively correlated with cement content, and positively correlated with PG content. In combination with direct shear test results, CSPS is divided into mild water expansion (0 <δe ≤15), moderate water expansion (15 < δe ≤80), and severe water expansion (δe > 80).
Comparative study on properties of recycled concrete mixed with slag and polypropylene fiber/steel fiber
Authors: Fang Jinmiao , Zhi-yong Han , Qingyun Ge , Zhu Bian , Wenli Li
Published: May 2021

In order to study the effect of fiber and slag on the performance of high performance recycled aggregate concrete, polypropylene fiber/steel fiber and slag are selected as admixtures, in which fiber is used as admixture and slag is equivalent to replace cement content. The influence of recycled aggregate content, admixture formula and admixture on the mechanical and water absorption properties of high performance recycled concrete and its improvement effect were analyzed systematically. The results showed that when the slag is added, the early mechanical properties of concrete have little effect, the later is slightly improved, but the water absorption of concrete is improved significantly. Adding fiber can not only improve the compressive strength, splitting tensile strength and flexural tensile strength of high performance recycled concrete, but also significantly improve the water absorption properties. Fiber and slag composite modified material can bond concrete mixture into a whole and improve the density of the mixture.
Study on the interaction mechanism between deep displacement of soil and internal force of anchor cable under pile-anchor support system of ultra-deep foundation pit
Authors: Han J H , Wang J P , Gu C Y
Published: May 2021

Based on a concrete engineering example, the change law of soil deep displacement and internal force of anchor cable in the excavation process of foundation pit under pile and anchor support system is simulated by numerical analysis method, and compared with the measured results, and the synergistic action law of soil deep displacement and internal force of anchor cable is discussed. The comparison between the results of finite element numerical analysis and the field measurement shows that the two-dimensional finite element numerical analysis can reflect the variation law of the deep displacement of soil and the internal force of anchor cable in the field to some extent.
Study on properties and pore structure characteristics of cement-based materials with limestone powder
Authors: Xia Junying , Yu Bentian , Wang Huan , Han Baojian , Chen Yanfei , Xie Chao
Published: May 2021

In order to study the effect of limestone powder as an auxiliary cementing material replacing part of cement on the properties and pore structure of cement mortar, the working performance, mechanical properties and pore structure characteristics of cement mortar with 0%, 10%, 20% and 40% substitutions of limestone powder were tested. The experimental results show that with the increase of the amount of limestone powder, the fluidity of mortar increases continuously and the water retention also becomes better. The addition of limestone powder improves the workability of mortar, but with the increase of limestone powder, the compressive strength of mortar decreases continuously. The results of low field NMR show that the porosity of cement mortar increases firstly and then decreases with the increase of limestone powder content. Compared with the reference mortar, its porosity is improved to some extent, however the pore throat distribution indicates that the increase of porosity is caused by the increase of small pores between 0.01μm and 0.16μm. The harmful macropores between 0.16μm and 0.63μm in mortar are reduced, which indicate that the addition of limestone powder can effectively improve the pore diameter distribution of mortar.
Centrifugal Modeling of Geo-synthetics Reinforced Roadbed under Cyclic Loading Condition
Authors: Mu Taiping , Chen Tianyi , Qiu Zhixiong
Published: May 2021

The cyclic load of overload vehicles will cause uneven deformation of the roadbed, leading to serious safety accidents. Geo-synthetics can effectively restrict the roadbed as a type of reinforcement. However, it is not clear how to arrange geo-synthetics for a good balance between the economic benefits and sufficient reinforcement. A series of centrifuge model tests of geo-synthetics reinforced roadbed are carried out under the cyclic loads. The deformation and reinforcement effect are investigated by considering the different geo-synthetics spacing. The results show that geo-synthetics effectively restricts the roadbed deformation. The reinforcement effect of geo-synthetics decreases with the increase of depth along the loading center. The geo-synthetics reinforcement effect is enhanced by decreasing the geo-synthetics spacing. The cyclic loads only induce deformation within a limited zone in the roadbed. As the geo-synthetics spacing decreases, the depth of the deformation zone decreases while the horizontal width increases.
Application Research on Information Integration Technology of Bridge BIM Model Based on 2-D EBS Coding System
Authors: Sha Gaocen , Wang Hong , Men Guangyu , Guo Rui , Feng Yuchuan
Published: May 2021

In the trend of information technology, BIM Technology has been widely used in the design, construction and maintenance stages of bridge engineering activities with its own advantages. At present, BIM Technology has made further development to realize the bridge life cycle information. In view of the shortage of information carrier in the application of EBS in BIM life cycle, this paper proposes a 2-dimensional EBS coding system component decomposition coding system. The 2-D EBS coding system is composed of component information and subsidiary information. Through the practical application of Shapotou Yellow River Bridge in Ningxia, the possibility of 2-D EBS coding system in bridge life cycle information integration, exchange and storage is further verified. It provides a link role for bridge life cycle informatization, and has strong engineering practice significance.
Accuracy analysis of multi-baseline InSAR height inversion
Authors: Hao Yin Ying , Hui YuanZhi
Published: May 2021

Digital elevation model (DEM) is of great significance in commercial and scientific applications, and the accuracy of elevation inversion represents the quality of DEM. With reference to the height measurement accuracy formula of single-baseline interferometric SAR, the mathematical relations between elevation accuracy and platform height, lower viewing angle, target oblique distance, baseline strip number, baseline length and baseline roll angle are established, and the variation of elevation accuracy with system parameters (especially the number of base lines and baseline length) is quantitatively analyzed, and the optimal range of multi-baseline InSAR system parameters is obtained. It provides a theoretical basis for the optimal design of system parameters.
A modified partially averaged Navier-stokes model for the turbulent flows over a backward facing step
Authors: Ye W X , Miyagawa K , Luo X W
Published: May 2021

In current study, a partially averaged Navier-stokes model based on a modified SST k-ω model is proposed (MSST PANS) to predict the turbulent flows with flow separations, recirculation and reattachment. A benchmark case, turbulence flows over the backward facing step (Re=50000), is treated to evaluate the capacity of the MSST PANS model. Several other turbulence models, i.e., the standard k-ε model, SST k-ω model, the standard k-ε PANS (SKE PANS) model and SST k-ω PANS (SST PANS) model are also implemented for comparisons with some available experimental data. Results show that the MSST PANS model performs the closest results in predicting the reattachment length as well as the corner vortex. Furthermore, the MSST PANS model yields improved statistics on the skin frictions, pressures, velocity profiles together with Reynolds stresses. In contrast to the SST PANS models, the modifications on the eddy viscosity and ω equation with consideration of streamline curvature show promising in capturing the small-scale flow separations, recirculation and reattachments in some industrial applications.
Localization and characterization of rotating noise sources on axial fans by means of an irregularly shaped microphone array
Authors: Amoiridis O , Zamponi R , Zarri A , Christophe J , Schram C
Published: May 2021

Aerodynamic noise emitted by low-speed axial fans has been receiving increasing attention in various sectors of high societal impact, such as automotive and HVAC systems. In this framework, turbulence interaction, flow non-uniformities, trailing-edge boundary layer fluctuations and blade-tip leakages are different mechanisms generating aeroacoustic sources on the rotating blades and contributing to the overall emitted sound. An accurate localization of the sound sources on the surface of the blade is instrumental in separating and isolating these contributions and, therefore, in designing novel sound mitigation concepts. The main objective of this paper is to present an inexpensive and efficient way to isolate and quantify the noise generating mechanisms on rotating blades by means of a irregularly shaped microphone array. The technique is based on ROtating Source Identifier (ROSI) and has been implemented and validated at the von Karman Institute for Fluid Dynamics (VKI). Simulated benchmark datasets that refer to rotating point sources emitting white noise have been considered for the validation of the method. The accuracy in the source localization and in the source strength reconstruction has been evaluated for a fixed and a variable angular rate. Moreover, the algorithm implementation has been parallelized with the purpose of reducing its computational time, which represents the main drawback of ROSI. Finally, the developed technique has been applied to measure the noise sources generated by a forward-skewed subsonic axial fan operated at maximum efficiency. In this case, it has been possible to successfully localize and characterize the major noise sources on the blades. Although further investigation will be necessary to gain better insight into the topic, the present work constitutes an important step for a better understanding of the physical phenomena occurring in the noise generation of an axial fan.
Hybrid Overset-LES Simulations of Noise Reduction Concepts of Loaded Airfoils
Authors: Bernicke P , Akkermans R A D
Published: May 2021

The noise reduction potential of a loaded airfoil is investigated by means of a novel Overset-LES simulation method. This aerodynamic noise prediction tool solves the compressible Navier-Stokes equations, supplemented with a sub-filter-stress model, in perturbation form over a background flow. The such obtained noise sources are subsequently propagated with wave propagation equations to the far-field (e.g., with the Acoustic Perturbation Equations). This hybrid prediction method is applied to a noise reduction investigation of a loaded airfoil. For this purpose, two geometries are considered, i.e., a reference geometry and a modified geometry with a long-chord slat. The effect of the long-chord slat on the turbulent sound sources is investigated by mainly considering turbulence statistics in the slat cove and shear-layer reattachment location. Moreover, the acoustic far-field propagation revealed the influence of a long-chord slat on the directivity. The slat noise reduction primarily results from the combined effect of the less intense shear-layer instabilities and the larger distance between reattachment location and upper trailing-edge, rather than a shielding effect by the long-chord slat. The predicted noise reduction matches well with values reported in literature.
Identification of Noise Sources in a Realistic Turbofan Rotor Using Large Eddy Simulation
Authors: Kholodov P , Moreau S
Published: May 2021

Large Eddy Simulation (LES) is performed using the NASA Source Diagnostic Test database at approach conditions (62% of the design speed). The simulation is performed in a periodic domain containing one single blade. The aerodynamic and acoustic results are compared with the experiment. Ffowcs Williams and Hawkings’ (FWH) analogy is used to compute the far-field noise from the solid surface of the rotor blade. The analogy is computed for the full blade and for its tip region to see the contribution of the latter. The dynamic mode decomposition is performed at different iso-radii of the computational domain. The contribution of the tip region to the far-field noise is observed around the first blade passing frequency (2.8 kHz) and 4 kHz due to the mixing process of the leading-edge and tip vortices. The rest of the blade contributes more at frequencies above 7 kHz which corresponds to the trailing-edge noise. The high-amplitude modes are observed at 75% and 90% of the spanwise length. These modes contribute to the corresponding frequency humps in the far-field spectrum.
Noise from unmanned aerial vehicle contra-rotating propellers
Authors: McKay R. S. , Go S. T. , Jung S. , Kingan M. J.
Published: May 2021

This paper presents an analysis of the noise produced by contra-rotating propeller systems used on small unmanned aerial vehicles. Selected results from an extensive experimental campaign are presented. In these experiments a commercially available contra-rotating propeller with 2- and 3-blade propellers was statically tested in a large anechoic chamber. It was observed that the noise spectrum contained a large number of tones which occurred at the sum of integer multiples of the blade passing frequency of each propeller. These tones exhibit some interesting features including: the amplitude of the interaction tones decays rapidly with increasing propeller spacing; tones for which the azimuthal mode number is equal to zero generally have a dipole like radiation pattern radiating strongly along the propeller axis. This is in contrast to the tones at the blade-passing frequency which radiate strongly in the plane of the propeller. A simple theoretical model for predicting the tones produced by the contra-rotating propeller is presented and is used to explain some of the observed phenomena.
Lattice Boltzmann Simulation of Industrial Axial Fan Noise
Authors: Hayashi K , Nakaye S , Nishimura S
Published: May 2021

Noise simulation of an industrial axial fan has been conducted by implicit large-eddy simulation with Lattice Boltzmann simulation which is based on Cumulant Lattice Boltzmann method with wall model and diffuse-interface method for a moving boundary condition. Simulation results are compared with experimental results of a factory test of an industrial fan for a thermal power generation. The result shows a good agreement and overall value is within 3dB error.
Analytical prediction of the blade trailing edge broadband noise of a plug fan
Authors: Zurbano-Fernández Ignacio , Guédel Alain , Robitu Mirela , Roger Michel
Published: May 2021

This study presents a low-order broadband noise prediction tool for centrifugal plug fans, based on analytical models using inputs from CFD simulations. Firstly, the fan used as a reference in this investigation was tested in a double reverberant room where the aerodynamic performance and the acoustic signature were measured simultaneously. Secondly, CFD RANS simulations of the fan in the test rig were performed. The outcome of the simulations is then used to feed Amiet’s analytical broadband noise model, along with wall-pressure spectral and correlation length models. Amiet’s model has been transposed to a rotating blade, adapted to the geometry of the fan. Finally, the model predictions are compared with the measurements.
Numerical Investigation of Pressure Fluctuation and Cavitation inside a Francis Turbine Draft Tube with Air Admission through a Fin
Authors: Zhang Ruizhi , Yu An , Nishi Michihiro , Luo Xianwu
Published: May 2021

The stabilizer installation and air admission have been proved to be two effective ways to alleviate the pressure fluctuation in the Francis turbine draft tube. In this research, a combined method of these two ways, i.e. air admission through a fin (one type of the stabilizer) is applied, and its effectiveness, especially air admission’s effects, on pressure fluctuation suppression has been investigated through numerical calculation. Two cases of different air amount (Q
*=0.01 and 0.02) are investigated. Results show that cavitation inside the draft tube is suppressed and the size of vortex rope is also slightly decreased after air is admitted. As a result, pressure fluctuation inside the draft tube is generally alleviated compared with no air admission case. The maximum amplitude of pressure fluctuation decreases by 9.2% with 0.01 air admission, and by 26.3% with 0.02 air admission. In addition, the position where the maximum amplitude of pressure fluctuation occurs also moves downstream, which should be due to the more violent interaction between the vortex rope in the main stream and a small vortex rope attached to the fin. Consequently, a slight increase of pressure fluctuation downstream the fin can be observed. Although air admission through the fin can suppress pressure fluctuation in the draft tube, it would also lead to turbine efficiency decrease. Therefore, the application of both fin and air admission should be carefully considered to achieve better performance for Francis turbines.