• Issue 4,2019 Table of Contents
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    • >Special Column: National Young Scholar/Local Science Foundation
    • Resistance welding parametric modeling based on CATIA CAA

      2019, 40(4):285-293. DOI: 10.7535/hbkd.2019yx04001

      Abstract (1086) HTML (0) PDF 4.63 M (1317) Comment (0) Favorites

      Abstract:There′re numbers of welding spots and types in vehicle seat framework (VSF) and high welding quality requirement, while commercial CAD weld design has low efficiency and cannot satisfy customers′ requirement, so it′s urgent to realize automated processing design through self-defined development. Aiming at that problems, based on analysis of processing parameters and restrains of resistance welding in VSF, a framework for welding spot modeling via the technical route of CAA user interface design, self-defined object, parameter validation and entity creation, is advanced. Furthermore, problems of parameter automatic computing and validation are studied through examples of spot diameter computation of nut side weld and distance computation between spot center and sideline. Finally, parametric modeling of plate projection weld and nut weld of resistance welding of resistance welding for VSF is realized via CAA redevelopment. This case manifests that advanced development functions of CATIA can realize creation of self-defined objects and management of processing parameters to satisfy advanced customers′ requirement. CATIA CAA has integrated functions of GUI design, object extension and geometric and topological object edition, which grants its powerful ability in object self-definition, so it can be effectively applied to mature customers.

    • >Mathematics
    • Existence of positive solutions for boundary value problems of fractional differential equations with sign-changing nonlinear term

      2019, 40(4):294-300. DOI: 10.7535/hbkd.2019yx04002

      Abstract (1124) HTML (0) PDF 847.42 K (886) Comment (0) Favorites

      Abstract:In order to further study the properties of boundary value problems for fractional differential equations with non-linear terms,we discusses the existence of positive solutions for eigenvalue problems of (n-1,1) fractional differential equations with sign-changing nonlinear terms, where the fractional derivative is Riemann-Liouville. First we use the Green function for a given boundary value problem and convert the differential equation into an equivalent integral equation. Then, under the condition that the nonlinear term f(t, x) satisfies Caratheodory conditions (that is to say, the non-linear term f(t,x) is measurable function when the variable x was chosen arbitrarily, and the non-linear term f(t,x) is continuous function of x when the variable t was fixed). By constructing a suitable Banach space, we use the cone-stretching and compression fixed point theorem and Leray-Schauder nonlinear selection to obtain the sufficient conditions for the existence of positive solutions of boundary value problems.The results show that the nonlinear term f(t,x) can be singular at any point t. At the same time, the range of the eigenvalue which makes the solution of the boundary value problem exist was changed.The results lay a foundation for further study of the existing conclusions.

    • A stochastic three-species food web model with Lévy jumps

      2019, 40(4):301-306. DOI: 10.7535/hbkd.2019yx04003

      Abstract (1011) HTML (0) PDF 1018.05 K (833) Comment (0) Favorites

      Abstract:For a stochastic three-species food web model with double parameters perturbation and Lévy jumps, we give the existence and uniqueness of global positive solution,which is beneficial to further study its dynamic properties. Then, by constructing Lyapunov function and applying It′s formula and Chebyshev’s inequality, it is found that the model is stochastic and ultimately bounded. Moreover, the sufficient conditions of extinction are obtained by using exponential martingale inequality and Borel-Cantelli’s lemma. Finally, some numerical simulations are introduced to illustrate the rationality of the theoretical results. The results show that the model is stochastic and ultimately bounded under the influence of Lévy noise, and large Lévy noise can lead to the extinction of populations. The algorithm has obtained good results both in theory and numerical simulations, which provides certain significance for many problems of stochastic population models.

    • Mixed monotone method for a class of fractional q-difference boundary value problems

      2019, 40(4):307-316. DOI: 10.7535/hbkd.2019yx04004

      Abstract (964) HTML (0) PDF 882.83 K (846) Comment (0) Favorites

      Abstract:In order to study the existence and uniqueness of nontrivial solutions for boundary value problems of a class of nonlinear fractional difference equations.Firstly, a new concept is defined on a new set. Then, by using the definition of normal cone, the existence of unique fixed points for two mixed monotone operators is established. Green functions for linear fractional-order boundary value problems are obtained, and the upper and lower bounds of Green functions are estimated. Thus, the expression of the particular solution can be obtained.Secondly, by using the abstract theorem, we discuss the non-linear terms which meet the conditions of the theorem, establish the existence of the unique solution of the above problem, and obtain the iteration sequence approaching the unique solution. Furthermore, the existence and uniqueness of nontrivial solutions for boundary value problems of fractional difference equations are proved. Finally, we give an example to illustrate the validity of the main theorems and results. The results show that the conditions of the theorem are proved and the nontrivial solution of the boundary value problem satisfies the existence and uniqueness. The research method has obtained good results in theoretical proof and boundary value problem, and has certain reference significance for other boundary value problems.

    • >Mechanical, Electronics and Information Science
    • Water conservancy detection method and application based on migration locationing technology

      2019, 40(4):317-324. DOI: 10.7535/hbkd.2019yx04005

      Abstract (1257) HTML (0) PDF 1.67 M (916) Comment (0) Favorites

      Abstract:In order to suppress the strong direct wave in the original image of GPR, highlight the weak target signal and realize the accurate location of the hidden danger, a Stolt migration method combining with robust principal component analysis (RPCA) is proposed.Firstly, the synthetic data are generated by using the GPR analysis program package matGPR3.1 to simulate the dam-void model, and the original image of the GPR is obtained through scanning processing.Then the RPCA method is used to extract the hyperbolic signal of the target.Finally, the target signal is focused by Stolt migration technique, and the optimal migration effect is obtained by selecting the appropriate migration velocity through minimum entropy velocity estimation.The experimental results show that the proposed method can effectively suppress the clutter and identify the location of the target void more clearly.Compared with the previous methods, the image obtained by the method has higher resolution and better performance, and has a certain application value in the detection of hidden dangers in water conservancy project.

    • Study on vibration characteristics of deflection generator considering magnetostrictive effect

      2019, 40(4):325-332. DOI: 10.7535/hbkd.2019yx04006

      Abstract (1343) HTML (0) PDF 3.72 M (1093) Comment (0) Favorites

      Abstract:In order to improve the utilization of wind energy and solve the problem of single rotor rotation of existing switched reluctance generators, a new type of deflectable dual stator Switched Reluctance Wind generator is proposed. Firstly, based on the electromagnetic-solid mechanics module, the electromagnetic field, flux density and magnetostrictive density of stator structure are analyzed theoretically by establishing the magneto-solid coupling numerical model. Secondly, the finite element platform is used to model the generator intuitively. based on the theory of mechanics, the basic equation of electromagnetic solid mechanics considering magnetostrictive effect is established. Finally, the finite element method is used to simulate the internal and external stators of the generator and the rotation and deflection of the rotor. The stress distribution and the corresponding vibration displacement are obtained. The simulation results show that: The vibration displacement under magnetostrictive effect belongs to nanometer level and the stress is small, so the influence on generator operation can be neglected. The analysis method of magneto-solid coupling provides theoretical reference in analyzing motor vibration and further optimizing generator parameters.

    • Simulation research on excitation system of multi-electrode blood flow meter

      2019, 40(4):333-343. DOI: 10.7535/hbkd.2019yx04007

      Abstract (1007) HTML (0) PDF 3.74 M (941) Comment (0) Favorites

      Abstract:In order to monitor human blood flow rate and flow velocity distribution, a blood flow meter based on multi-electrode electromagnetic measurement has been proposed to measure the flow velocity of the arteriovenous blood by obtaining the induced voltage on the skin surface. The COMSOL 3-D model has been built to simulate the physical structure of the human limb, including the size and relative position of skin, fat, bones, muscles, arteries and veins. Based on the Helmholtz coil and C-type coil, the electromagnetic induction intensity distribution of excitation structures and methods is simulated which is imposed through the body measurement section. The optimal design scheme of the excitation coil is proposed. Different excitation systems of different structures and different incentive methods are compared. The result shows that the two pairs of Helmholtz coils of orthogonal layout with syntroph excitation current has better uniformity, field center symmetry and stronger magnetic field strength, and effectively enhances the value of induction electromotive force, showing it is more suitable for multi-electrode electromagnetic measurement of non-axisymmetric flow. The research result proves that the optimization scheme of excitation system is feasible, and its uniformity plays a positive role in improving the accuracy of velocity reconstruction.

    • >Material Science
    • Rotating bending fatigue properties of medium alloy Cr and Mo nitriding bearing steel

      2019, 40(4):344-350. DOI: 10.7535/hbkd.2019yx04008

      Abstract (973) HTML (0) PDF 2.81 M (958) Comment (0) Favorites

      Abstract:In order to study the influence of chemical heat treatment on the fatigue performance of large bearings, plasma nitriding and rotating bending fatigue test are conducted for the medium alloy Cr and Mo nitriding bearing steel. The middle alloy Cr and Mo bearing steel with double vacuum melting is used as the experimental material to analysis the microstructure after hardening and tempering (930 ℃+550 ℃)and the phase after plasma nitriding. The fatigue morphology and the mechanismroom of crack initiation after the test are analyzed. The relationship between surface defects and fatigue fracture mechanism is established.The results of experimentalshow that the microstructure of the test steel after hardening and tempering is tempered sorbite, M2C and M3C is the mainly precipitations. After nitriding,the compound layers in the nitriding layers are mainly composed of γ′phase (Fe4N) and CrN and the thickness is about 16 μm, which is not conducive to improve the performance of matrix fatigue. The RBF limit of the experimental steel after nitriding is 947 MPa, which is 19.4% higher than the RBF limit of the non-nitriding sample. The cracking of compound layer in the nitrided layer and the cracking of non-metallic inclusions are the two main ways of cracking. The compound layer and surface roughness have great influence on the fatigue life of test steel after nitriding. The results provide experimental and theoretical basis for improving the fatigue performance of medium alloy Cr and Mo nitriding bearing steel.

    • High temperature flow behavior and constitutive model of 35CrMo steel

      2019, 40(4):351-358. DOI: 10.7535/hbkd.2019yx04009

      Abstract (1077) HTML (0) PDF 1.87 M (1035) Comment (0) Favorites

      Abstract:In order to describe the stress-strain relationship of 35CrMo steel and establish constitutive model of material, the high temperature thermal simulation compression experiment of hot rolled 35CrMo steel is conducted by the Gleeble3800 thermal simulation machine, the effect ofdeformation temperature and strain rate on the material flow stress of 35CrMo steel is studied under the condition that the deformation temperature is 800, 900,1 000,1 100,1 200 ℃ and the strain rate are 0.01,0.1,1,10 s-1. The experimental results show that there are two stress-strain relationships, dynamic recovery and dynamic recrystallization, in the high-temperature deformation of 35CrMo steel.The constitutive equation of 35CrMo steel peak stress is established indirectly by calculating the relationship between critical strain and peak strain, and the accuracy of the constitutive equation is verified.This constitutive equation can well describe the stress-strain relationship under the thermal deformation condition of 35CrMo steel, and ithas basic theoretical significance for guidingthe thermal formingprocess design and numerical simulation of 35CrMo steel.

    • >Food Science and Biological Science
    • Application and research progress of metabonomics technology in monitoring violatory use of veterinary drugs

      2019, 40(4):359-365. DOI: 10.7535/hbkd.2019yx04010

      Abstract (1255) HTML (0) PDF 1.37 M (1118) Comment (0) Favorites

      Abstract:The development and innovation of veterinary drug residue analysis and detection technology is an important research content of animal-derived food safety monitoring. As an important part of systems biology, metabolomics research and its detection technology also play an indispensable role in the field of animal-derived food safety. Based on the current research results of metabolomics technology in the field of veterinary drug residue detection, the conceptual, principles and classification of metabolomics are illustrated. Taking the detection of two types of veterinary drug residues, such as clenbuterol and steroids, the current application status of the commonly used detection techniques of metabolomics contains liquid chromatography-tandem mass spectrometry (LC-MS) or gas chromatography-tandem mass spectrometry (GC-MS) on the detection of animal's blood and urine samples. The problems of untargeted metabolomics and targeted metabolomics with low precision and throughput are analyzed. The limitations of metabolomics technology over-reliance on large instrumentation and professional databases have also been offered. Further, metabolomics technology is proposed, which should be based on sample characteristics and detection purposes in the application of veterinary drug residue detection. The multi-technology platform (liquid chromatography electrospray time-of-flight mass spectrometry, ultra high performance liquid chromatography quadrupole time-of-flight mass spectrometry), multi-analysis platform (principal component analysis, partial least squares discrimination analysis) and multi-omics (genomics, transcriptomics, and proteomics) technology are used together to improve the applicability and applicational range of metabolomics technology in the field of veterinary drug residue detection. It provides new research directions for veterinary drug residue analysis and testing technology.

    • >Special Column: New Energy Resources, Energy Conservation and Environmental Protection
    • Study of pretreatment on Baiyinhua lignite in thermal extraction process

      2019, 40(4):366-370. DOI: 10.7535/hbkd.2019yx04011

      Abstract (1132) HTML (0) PDF 1.20 M (828) Comment (0) Favorites

      Abstract:In order to solve the problem of low thermal extraction rate of lignite, the raw coal is pretreated with acid and alkali as solvent, and then the pretreated raw coal is subjected to thermal extraction reaction to prepare ultra-pure coal under the process conditions of operating temperature 380 ℃, normal pressure and coal dissolution ratio of 10∶1. The effects of different acid and alkali solvents on thermal extraction rate are investigated. The results show that compared with raw coal, the thermal extraction rate of lignite treated with different kinds of acid-base solvents has been improved to different degrees, and the thermal extraction rate of lignite pretreated with potassium hydroxide is the highest, reaching 66.5%. Infrared spectrum shows that pretreatment of raw coal with acid-base solvent can effectively destroy the molecular structure of coal, expose inorganic mineral salts and fully expose organic functional groups. Therefore, higher yield of ultra-pure coal can be obtained through pretreatment, and the usage of high-quality coal in coal blending and coking industry can be reduced.

Editor in chief:朱立光

Inauguration:

International standard number:ISSN 1008-1542

Unified domestic issue:CN 13-1225/TS

Domestic postal code:

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