• Issue 2,2019 Table of Contents
    Select All
    Display Type: |
    • >Special Column: National Young Scholar/Local Science Foundation
    • Research on CFD numerical simulation of an oblique tee and the influencing factors of heat transfer

      2019, 40(2):97-104. DOI: 10.7535/hbkd.2019yx02001

      Abstract (1398) HTML (0) PDF 973.33 K (1633) Comment (0) Favorites

      Abstract:In order to study the flow and heat transfer process of the fluid in an obliquetee, the CFD simulation of flow and heat transfer processes of the fluid in oblique tee with the included angle of 20°~90°, the velocity ratio of 2~3.5 and the branch position of 500~1 000 mm is carried out based on Fluent software, and the sensitivity analysis of various parameters influencing the average heat transfer coefficient of wall surface is conducted by orthogonal experimental design. The results show that as the included angle or velocity ratio increases, the maximum velocity of fluid at the outlet of oblique tee increases gradually, and the influence of velocity ratio is more significant. The average heat transfer coefficient of wall surface also increases with the increase of included angle and velocity ratio; the branch position mainly affects the average heat transfer coefficient of wall surface, and its influence on the velocity is negligible. The average heat transfer coefficient of wall surface is increasing with the decrease of the branch position. According to the different effects of various parameters on average heat transfer coefficient of wall surface, branch position l>velocity ratio λ>included angle θ, which means that the closer the branch pipe is to the inlet of main pipe, the greater the velocity ratio, and the greater the included angle, the better the heat transfer effect of wall surface will be. Therefore, the branch position is the primary factor to influence the heat transfer effect of oblique tee.

    • Overview of braking intention recognition for longitudinal dynamic control of vehicles

      2019, 40(2):105-111. DOI: 10.7535/hbkd.2019yx02002

      Abstract (1421) HTML (0) PDF 851.66 K (1707) Comment (0) Favorites

      Abstract:As a prerequisite for the control of the brake by wire system, the identification of braking intention has a direct impact on the accuracy of the vehicle control system, and it affects the vehicle running safety under specific working conditions, thus, in order to improve the active safety and braking performance of the vehicle, aiming at the longitudinal stability control problem in vehicle dynamics, the braking intention is taken as the breakthrough point, and the classification of braking intentions is introduced. At the same time, the vehicle dynamics control of braking intention recognition based on the research status at home and abroad is outlined. Besides, combining with the braking intention recognition feature selection problem, several typical braking intention recognition methods, including fuzzy inference system, neural network, adaptive neural fuzzy inference system, hidden Markov model and cluster analysis, are comparatively analyzed. Considering the status quo of research, the research emphasis and direction of braking intention recognition for vehicle dynamics control is pointed out, including reasonably selecting characteristic parameters, transition of export target and multistandard evaluation system.

    • >Mathematics
    • Numerical bifurcation and hybrid control of a Gompertz model with time delay

      2019, 40(2):112-118. DOI: 10.7535/hbkd.2019yx02003

      Abstract (1293) HTML (0) PDF 865.34 K (1029) Comment (0) Favorites

      Abstract:In order to study the stability of species, the biological systems are required to reduce or expand the stable region. For a Gompertz model with time delay, a hybrid control Euler method is proposed in which state feedback and parameter perturbation are used to control the Neimark-Sacker bifurcation. The local stability of the equilibria is discussed according to Hopf bifurcation theory. For controlling Neimark-Sacker bifurcation, the hybrid control numerical algorithm is introduced to generate the Neimark-Sacker bifurcation at a desired bifurcation point. The explicit algorithms for determining the direction of the bifurcation and the stability of the bifurcating periodic solutions are derived by using the normal form method and center manifold theorem. Numerical examples are provided to illustrate the theoretical results. The research results show that the branch point can be in advance or delay for the delay Gompertz model system through choosing appropriate control parameters. The algorithm has obtained good results both in theory and numerical performance, which provides a new method and has certain theoretical significance for its application in many control problems.

    • Existence of solutions for quasilinear p-biharmonic equations with critical Sobolev-Hardy terms

      2019, 40(2):119-124. DOI: 10.7535/hbkd.2019yx02004

      Abstract (1618) HTML (0) PDF 836.01 K (1022) Comment (0) Favorites

      Abstract:In order to study a class of quasilinear p-biharmonic equations with Hardy terms and multi-critical Sobolev-Hardy exponents, the existence theorem of the solutions to the above problem is established by means of the Ekeland variational principle. Firstly, to guarantee the variational functional is bounded from below, it is restricted on a set Mη (usually called Nehari manifold). Secondly, the set Mη is divided into three parts M+η, M0η and M-η by using fibering maps. Moreover, the existence of minimum in M+η and M-η is proved by studying the properties of the two subsets. Finally, by using implicit function theorem, it is found that there exists a minimizing sequence {un} making the (PS)c conditions hold when the parameters satisfy certain conditions. Therefore, the existence of the solutions to the problem is proved. The conclusions provide a theoretical basis for judging the structure and properties of the solutions.

    • >Chemistry and Chemical Industry
    • Preparation of Ag/RGO@DE nanocomposite particles and photocatalytic reduction of p-nitrophenol

      2019, 40(2):125-132. DOI: 10.7535/hbkd.2019yx02005

      Abstract (1345) HTML (0) PDF 1022.57 K (1206) Comment (0) Favorites

      Abstract:In order to effectively reduce nitro compounds in contaminated water, Ag/RGO@DE nanocomposite particles with high catalytic activity are prepared with an in-situ synthesis method. The morphology, microstructure and composition of as-prepared Ag/RGO@DE nanocomposite particles are characterized by SEM, XRD, XPS and FTIR, and the photoelectric property of the Ag/RGO@DE nanocomposite particles is characterized by UV-vis DRS, PL and photocurrent. The influence of different Ag and RGO load on catalytic activities of Ag/RGO@DE nanocomposite particles are examined by using the reduction of 4-NP as a model reaction. The results show that the RGO has lamellar structure, while the silver nanoparticles are face-centered cubic crystallites dispersing on the surface or between the lamellar of the RGO and diatomite. The visible-light absorption and electron-hole separation efficiency of RGO are improved by the introduction of silver nanoparticles. When the mass fraction of Ag is 2.5% and the mass fraction of RGO is 26.6%, the Ag/RGO@DE nanocomposite demonstrates the best photocatalytic activity. Ag/RGO@DE nanocomposite particles have satisfying stability and high catalytic activity for the reduction of 4-NP.

    • >Food Science and Biological Science
    • Cloning and expression of phosphoenolpyruvate carboxykinase from Escherichia coli

      2019, 40(2):133-137. DOI: 10.7535/hbkd.2019yx02006

      Abstract (1293) HTML (0) PDF 979.22 K (1074) Comment (0) Favorites

      Abstract:In order to better study the structure and function of phosphoenolpyruvate carboxylase, the phosphoenolpyruvate carboxylase gene is cloned and expressed by PCR (polymerase chain reaction), double enzyme digestion and cell transformation. The results show that the new phosphoenolpyruvate carboxylase gene of Escherichia coli is successfully amplified and cloned into the prokaryotic expression vector pET-30a, and then introduced into Escherichia coli BL21 expression system. The phosphoenolpyruvate carboxylase of Escherichia coli is successfully induced by IPTG. The phosphoenolpyruvate carboxylase can be efficiently expressed by using the proposed method, which provides preparation for further scale expression, purification and application.

    • Study on the metabolite difference of tricolor quinoa from different habitats based on GC-MS

      2019, 40(2):138-144. DOI: 10.7535/hbkd.2019yx02007

      Abstract (1333) HTML (0) PDF 925.47 K (1095) Comment (0) Favorites

      Abstract:In order to study the effects of different habitats on the development of quinoa, taking quinoa seeds from different habitats as research objects, significant differences in metabolites and related metabolic pathways are screened. The metabolic profiles of the seeds of black quinoa, red quinoa and white quinoa from Dulan County, Qinghai Province and Yanyuan County, Sichuan Province are analyzed through non-targeted metabonomics analysis with GC-MS platform. The original data are pretreated by XCMS online platform for subsequent multivariate statistical analysis. The results show that the metabolic characteristics of black, red and white seeds in Dulan county and Yanyuan County are different. Among them, the difference between red and white seeds from the two counties is larger, while the difference of the black quinoa seeds is the smallest. There are 570 characteristic peaks in red seeds which have significant differences, and the up-regulated substances are less than the down-regulated. The difference between black quinoa from two habitats is the smallest, and the up- and down-regulated trends are like that of red quinoa. There is secondly significant difference between the white seeds from the two habitats, and the up- and down-regulated trends are the opposite of that of the red and black quinoas, and 486 characteristic peaks are detected, with more up-regulated substances than down-regulated. Different habitats have great impact on quinoa. Black and red quinoas are more suitable to be planted in Dulan County, Qinghai Province, while white quinoa is more suitable to be planted in Yanyuan County, Sichuan Province. The conclusions could guide the cultivation and breeding of quinoa in Dulan county and Yanyuan County, and provide theoretical basis for further study of the stress resistance mechanism of quinoa.

    • >Mechanical, Electronics and Information Science
    • Speed control of PM synchronous linear motor based on dynamic matrix

      2019, 40(2):145-151. DOI: 10.7535/hbkd.2019yx02008

      Abstract (1571) HTML (0) PDF 1.03 M (1204) Comment (0) Favorites

      Abstract:In order to improve the dynamic response performance of the linear motor, improve the robustness of the motor control system, and make the motor run stably, based on the theory of predictive control, a dynamic matrix controller suitable for speed loop control of linear motor is designed. The PID controller of speed loop in the traditional linear motor control system is replaced by dynamic matrix controller. The simulation models of the permanent magnet synchronous linear motors with PID controller and dynamic matrix speed controller are built. The step signal is applied to the control system, and the simulation under sudden load and sudden load reduction is completed. The response results of the systems with the two controllers are compared. The simulation results show that when the speed loop is controlled by dynamic matrix, the response speed of the motor is faster, the overshoot is smaller, and the motor speed is stable. The improved speed loop controller improves the robustness of the linear motor control system, the dynamic performance of the linear motor, and the anti-disturbance capability of the control system, which facilitates the operation of the motor under great load change conditions.

    • Abstractive summarization model considering hybrid lexical features

      2019, 40(2):152-158. DOI: 10.7535/hbkd.2019yx02009

      Abstract (1654) HTML (0) PDF 877.35 K (1346) Comment (0) Favorites

      Abstract:In order to use lexical features (including n-gram and part of speech information) to identify more key vocabulary content in the summarization generation process to further improve the quality of the summarization, an algorithm based on sequence-to-sequence (Seq2Seq) structure and attention mechanism and combining lexical features is proposed. The input layer of the algorithm combines the part of speech vector with the word vector, which is the input of the encoder layer. The encoder layer is composed of bi-directional LSTM, and the context vector is composed of the output of the encoder and the lexical feature vector extracted from the convolution neural network. The convolutional neural network layer in the model controls the lexical information, the bi-directional LSTM controls the sentence information, and the decoder layer uses unidirectional LSTM to decode the context vector and generates the summarization. The experiments on public dataset and the self-collected dataset show that the performance of the summarization generation model considering lexical feature is better than that of the contrast model. The ROUGE-1, ROUGE-2 and ROUGE-L scores on the public dataset are improved by 0.024, 0.033 and 0.030, respectively. Therefore, the generation of summarization is not only related to the semantics and themes of the article, but also to the lexical features.The proposed model provides a certain reference value in the research of generating summarization of integrating key infromation.

    • Frequency control technology for ultrasonic motor based on correlation phase extraction method

      2019, 40(2):159-166. DOI: 10.7535/hbkd.2019yx02010

      Abstract (1795) HTML (0) PDF 983.99 K (1082) Comment (0) Favorites

      Abstract:In order to solve the problems that the speed of ultrasonic motor is usually affected by the changes of temperature and load, and that due to installation volume and cost of the speed sensor, the closed-loop control based on speed feedback is often limited in some special applications, a frequency closed-loop control method based on phase difference feedback is introduced. Firstly, the type of phase difference feedback quantity is optimally selected according to the sensitivity of different motor phase differences to the temperature and load change; secondly, aiming to the interference of mechanical and harmonic noises on phase difference calculating result, the correlation phase extraction method is proposed to improve the accuracy of phase difference between driving voltage and monitor electrode voltage; lastly, the corresponding frequency closed-loop control scheme is given according to the changes of temperature and load change, respectively. Experiment results indicate that this method can reduce the speed fluctuations caused by the changes of temperature and load, and improve the speed stability of motor system. Because only two voltage signals are needed to be recorded, this method is easy for implementation.

    • Multi-time scale reduction of photovoltaic system models

      2019, 40(2):167-174. DOI: 10.7535/hbkd.2019yx02011

      Abstract (1291) HTML (0) PDF 875.85 K (1040) Comment (0) Favorites

      Abstract:In order to solve the model complexity and analysis difficulty of electric system joined up by photovoltaic power system, a simple and practical model reduction method of photovoltaic power system is proposed. Considering the main circuit and control strategy, a small signal model of photovoltaic power generation system is established. On this basis, the multi-time scale characteristics of the system model are decomposed to determine the fast and slow states. The correctness of the fast and slow states decomposition is verified by the relative velocity estimation method, which avoids the inconsistency of the stability of the system before and after the reduction caused by the improper selection of perturbation parameters. By ignoring the fast dynamic factors, the order of the model is reduced, and the zero-order approximation model and the first-order approximation model are obtained by adding correction terms. Finally, the dynamic responses and calculation errors of the reduced order model, the corrected model and the original model are compared in MATLAB. The results show that the reduced model and the correction model can correctly reflect the dynamic response of the detailed model under small perturbations, and have obvious advantages in improving the calculation speed and simplifying the analysis process.

    • >Special Column: New Energy Resources, Energy Conservation and Environmental Protection
    • Correlation between antibiotic resistance genes and microbial communities in pharmaceutical wastewater

      2019, 40(2):175-181. DOI: 10.7535/hbkd.2019yx02012

      Abstract (1151) HTML (0) PDF 936.12 K (1128) Comment (0) Favorites

      Abstract:In order to study the distribution, amplification and correlation of microbial community structure and resistance genes in pharmaceutical wastewater, a variety of biological treatment processes are used to treat pharmaceutical wastewater. Combining Miseq high throughput sequencing analysis technology and fluorescence quantitative PCR technology, activated sludge in pharmaceutical wastewater plants is detected. The results show that sul1, sul2, tetO, tetQ, tetW, OXA-1 and INT1 are widely detected at all stages of pharmaceutical wastewater treatment plant. The total resistance gene concentration ranges from 3.09×108 to 2.26×109 copies/g (dry weight), and the total gene concentration increases by 7.3 times. Miseq sequencing results show that the dominant bacteria in pharmaceutical wastewater are Proteobacteria, Bacteroidetes, Firmicutes, Thermus and Gemmatimonadetes, with an average relative abundance ratio of 81.05%. Redundancy analysis shows that Aeromicrobium is positively correlated with sul2 to a high degree, which might be sul2 existing in microbial communities. Among the possible major microflora, Rhodovulum and Rhodospirillaceae are highly positively correlated with OXA-1 and tetQ, which are the main microflora of ARGs distribution. Acinetobacter has a high degree of positive correlation with tetO and tetW, which may be the main possible microflora of tetO and tetW in microbial community. The results show that appreciation and distribution of antibiotic resistance gens are connected with concerned specific bacterial genus. The controlled abundance of concerned bacterial genus could subduce resistance gene in industrial wastewater factory.

    • Numerical simulation study on calcination process of cement triple-spouting precalciner

      2019, 40(2):182-188. DOI: 10.7535/hbkd.2019yx02013

      Abstract (1244) HTML (0) PDF 937.58 K (1155) Comment (0) Favorites

      Abstract:To study the calcination process in a precalciner and improve calcination effect, the 4 500 t/d TTF precalciner in a domestic cement company is numerically modeled by Fluent. By selecting the standard k-ε model, discrete phase model and component transfer model, the flow field and temperature field are simulated, based on which, the pulverized coal combustion process and the effects of cement raw meal angle, tertiary air velocity and tertiary air temperature on calcination process are analyzed. The results show that the incidence angle of raw meal has great influence on the decomposition rate. When the tertiary air velocity is higher, the decomposition rate of raw meal and the burning rate of coke are also higher. Increase in tertiary air temperature causes insufficient combustion air and reduces coke reactivity, thereby reduces combustion rate. By optimizing the three parameters, the decomposition rate of CaCO3 and the burning rate of coke can reach 90.3% and 88.0%, respectively. The research on the numerical simulation of cement precalciner calcination process and its application in practical engineering projects can provide theoretical reference for optimizing cement production conditions, and has great practical significance for the cement industry and its coordinated development with resources and environment.

Editor in chief:朱立光

Inauguration:

International standard number:ISSN 1008-1542

Unified domestic issue:CN 13-1225/TS

Domestic postal code:

  • Most Read
  • Most Cited
  • Most Downloaded
Press search
Search term
From To