Volume 42,Issue 12,2019 Table of Contents

1 Test and simulation of the flow regeneration noise of dual mode muffler

WANG Bo , DENG Zhaoxiang , YANG Minglei

2019, 42(12):1-8. DOI: 10.11835/j.issn.1000-582X.2019.12.001

[Abstract](661) [HTML](462) [PDF 8.98 M](1356)

Abstract:
In order to explore the flow regeneration noise of the dual-mode muffler, a test bench was built. The flow regeneration noise and tailpipe noise were measured with the valve closed and opened respectively at different inlet flow rates by the methods of dual-microphone transfer function and the muffler static transmission loss. The test results show that the flow regeneration noise and the tailpipe noise are both reduced when the valve is opened, and the incident sound power of the flow regeneration noise at the outlet drops down to 1.1 dB, and the tailpipe noise down to 2.3 dB, which directly proves that the dual-mode muffler can help reduce the flow regeneration noise. Based on the test, a three-dimensional model of the muffler was built, and the flow field simulation inside the muffler was performed by Fluent, obtaining the distribution characteristics of pressure, airflow velocity and turbulent kinetic energy. The simulation results indicate that pressure, airflow velocity and turbulent kinetic energy of the muffler are reduced when the valve is opened. The simulation and experimental results are basically in agreement.

2 Seismic analysis and optimization of lifting-turnover mechanismof strong-radiation rods

ZHOU Jie , SHI Huimin , WANG Shilong , YANG Bo , LI Hai

2019, 42(12):9-22. DOI: 10.11835/j.issn.1000-582X.2019.12.002

[Abstract](626) [HTML](488) [PDF 4.43 M](1229)

Abstract:
The lifting-turnover mechanism is the key equipment of the post-processing system of the strong-radiation rod. According to the relevant design specifications, it is necessary to ensure that the rods does not break under seismic conditions and that the safety function and running performance of the mechanism are normal. To verify the seismic performance of the mechanism, based on ANASYS Workbench, finite element models of the lifting-turnover mechanism containing a hoist, a steel-wire rope, a silo rack-silo part, a rolling-over vehicle and upper/lower rails in the post-processing system, are established for seismic evaluation. Then, the stress assessment and strength check of the main units and the major bolts are carried out according to ASME codes, and the number of bolts installed on the upper rail is optimized. The simulation results show that the optimized lifting-turnover mechanism meets seismic design requirements of nuclear power plants.

3 The sound source identification of structural panels based on compressed singular value decomposition equivalent source method

HE Yansong , CHEN Liangsong , XU Zhongming , ZHANG Zhifei

2019, 42(12):23-33. DOI: 10.11835/j.issn.1000-582X.2019.12.003

[Abstract](841) [HTML](633) [PDF 20.33 M](1098)

Abstract:
To improve the performance of sound field reconstruction and sound source identification for the spatially extended source, a compressed singular value decomposition equivalent source method (CSVDESM), based on compressed sensing (CS) theory and the equivalent source method (ESM), is proposed in this paper. The CSVDESM obtains a series of orthogonal basis of the source field by the singular value decomposition (SVD), and reconstructs the sound field on the basis of the ESM and the CS framework. In addition, when combined with the high-order matrix function beamforming, CSVDESM can further improve the accuracy of sound source identification by increasing order value to narrow the identified acoustic center coverage continuously. Numerical simulation and experiment verify the validity and practicality of CSVDESM.

4 Prediction of component activity in alloys by neural network model based on MIVM

ZHOU Lanhua , ZENG Fuhong

2019, 42(12):34-40. DOI: 10.11835/j.issn.1000-582X.2019.12.004

[Abstract](705) [HTML](511) [PDF 1.38 M](883)

Abstract:
A back propagation (BP) algorithm of the neural network was established so as to use Molecular Interaction Volume Model (MIVM) to predict the components activity in alloy solution accurately and conveniently. Its input layer is the experimental activity coefficient of components in alloy solution, output layers are molecular pair energy interaction parameters and hidden layer is set to one layer. The structural parameters in BP neural network model were optimized via genetic algorithms, where the deviation between the experimental and theoretical values of the infinite dilution activity coefficient as fitness function. The optimization was carried out with minimum deviation so as to ensure the validity of BP neural network. Finally, the BP neural network model and algorithm were validated by taking the binary alloy solutions of Pb-Bi, Sn-Bi, Sn-Pb and Fe-Cu as examples. The results show that the average relative errors between the predicted and experimental values of components activity in the alloys are less than 4% and the absolute deviation less than 0.78, which can meet the requirements of engineering calculation.

5 Comprehensive geophysical exploration and safety evaluation of the mine with a fully mechanized pressurized mining face

MU Yi , XU Hui , MA Zhichao , JIANG Peng

2019, 42(12):41-49. DOI: 10.11835/j.issn.1000-582X.2019.12.005

[Abstract](678) [HTML](395) [PDF 21.91 M](1068)

Abstract:
Through the combined use of transient electromagnetic method and radio wave perspective method, the water-rich mining area and the water-conducting channel were detected in the pressurized mining area of the 61114 working face of the Dafanpu Mine, and the overlapping abnormal areas identified by the transient electromagnetic method and the radio wave perspective method were comprehensively analyzed. Safety evaluation and analysis of the pressurized mining area was conducted, and safe mining measures were proposed. The results showed that the transient electromagnetic method mainly detected the aquifer range and water richness, the radio wave perspective method mainly detected the development of the coal seam and the aquifuge layer. The overlapping abnormal regions detected respectively by the two methods had both water bodies and water channels, which were key areas for water prevention and control. For these overlapping anomalies defined by the underground comprehensive geophysical exploration, it was necessary to carry out pre-drilling verification. When the existence of water-rich anomalous structural belt was confirmed, safety analysis should be conducted in time, and grouting may be necessary for blocking the water conducting fractured zone or setting waterproof coal (rock) pillar to guarantee the safe mining on the pressurized workface.

6 Determination of the deformation stage of a fully mechanized caving face in the surrounding rock of mining roadway

QIN Hongyan , OUYANG Zhenhua , ZHAO Xidong , ZHANG Feng , TRAN MinhN guyen

2019, 42(12):50-59. DOI: 10.11835/j.issn.1000-582X.2019.12.006

[Abstract](498) [HTML](809) [PDF 8.68 M](1201)

Abstract:
To analyze the deformation characteristics of the mining roadway located in front of the fully mechanized top-coal caving face, we researched the j7401 fully mechanized top-coal caving face of the Helin Coal Mine with theoretical analysis and field measurement. According to the distribution curve of the advanced abutment pressure, three deformation stages of the roadway ahead of the working face are defined, which are the quick deformation stage, the deceleration deformation stage, and the stable deformation stage. The cut-off point of quick deformation stage and deceleration stage is the intersection of advanced abutment pressure and the original rock stress. The cut-off point of the deceleration deformation stage and stable deformation stage is the peak of the advanced abutment pressure. In this work, the advanced abutment pressure and roadway deformation of j7401 working face in mining were observed respectively, and the observation data was analyzed by the method of least squares fitting. The deformation of the roadway surrounding rock was partitioned based on the advanced abutment pressure observation data:the cut-off point of quick deformation stage and deceleration stage was 8.1 m ahead of the working face, and the cut-off point of deceleration deformation phase and stable stage was 19.8 m ahead of the working face. The deformation was also partitioned based on the roadway deformation observation data, in which way the cut-off point of quick deformation stage and deceleration stage was 8.9 m in front of the working face, and the cut-off point of deceleration deformation phase and stable stage was 20.1 m ahead of the working face. The deviations of the two classification methods were respectively 0.8 m and 0.3 m, indicating the method to partition the roadway surrounding rock deformation stage based on the advanced abutment pressure observation data is feasible and the precision is high.

7 Analysis of hydrazine in occupational environment by capillary gas chromatography

LIN Yimin , ZHOU Bin , TANG Lina , WANG Lijuan , ZHANG Wenwen , JI Weigang , YANG Xu

2019, 42(12):60-66. DOI: 10.11835/j.issn.1000-582X.2019.12.007

[Abstract](653) [HTML](557) [PDF 3.00 M](1061)

Abstract:
Hydrazine is derived with excessive furfural. The crystal of hydrazine derivative conversion is characterized by mass spectrometry. The comparative analyses are made between the hydrazine-derived furfural crystal, solvent, as well as extraction solution of furfural derivatives of hydrazine by the method of capillary gas chromatography. Reliable qualitative and quantitative analytical information is obtained, and the conditions of derivation, extraction and chromatographic analysis are optimized. The method is evaluated by standard curve, precision and accuracy tests. Experiments show that in the case of excessive furfural, hydrazine is completely converted to 2-furaldehyde azine, whose retention time is 6.20 min. The detection limit of the method is 0.007 8 mg/L, the relative standard deviation is 2.5%, and the recovery is in the range of 98% to 100%. The method has the advantages of symmetrical peak shape, high accuracy, high sensitivity and good selectivity. It provides a rapid and accurate procedure for the analysis and determination of hydrazine under different laboratory instruments and chromatographic column conditions.

8 Effects of starting powders on sinterability of Al₂O₃-ZrO₂ nanoceramics

FAN Changjie , LI Xin , XU Xiqing , ZHANG Xin , NIU Shuxin

2019, 42(12):67-73. DOI: 10.11835/j.issn.1000-582X.2019.12.008

[Abstract](607) [HTML](857) [PDF 8.22 M](1324)

Abstract:
In this work, Al₂O₃-ZrO₂ nanocomposites were prepared by spark plasma sintering (SPS) of nanocrystalline and amorphous powders, respectoively, and effects of starting powders on the densification and microstructure of the nanocomposites were investigated. To obtain dense nanocomposites, the minimum SPS temperature for nanocrystal powders was 1 400℃, and the resulting grain sizes were about 320 nm. For amorphous powders, however, the hot pressing temperature was as low as 1 200℃, and the products exhibited finer grains of about 150 nm. It was confirmed that amorphous powders could be hot pressed into dense nanocomposites at lower temperatures than nanocrystalline powders, and the easier densification of amorphous powders was attributed to the phase transformation of amorphous particles in sintering. This finding could provide new guidance for low temperature sintering of bulk nanocomposites.

9 An asymptotic analytical solution to the spherical indentation problem of incompressible elastic thin film

JIAO Zhian , WU Jian , WAN Ling

2019, 42(12):74-80. DOI: 10.11835/j.issn.1000-582X.2019.12.009

[Abstract](655) [HTML](698) [PDF 2.85 M](976)

Abstract:
In order to solve the problem of axisymmetric indentation of an incompressible elastic film on a rigid substrate, a simple analytical method based on Kerr-model is derived, in which the differential relation between the contact pressure and the displacement of the film's upper surface is established. Then, the high-order asymptotic solution to the problem is solved by using Betti's reciprocal theorem and the explicit relation between contact pressure, indentation depth and contact radius is built. When the high-order term is ignored, the present asymptotic solution is the same as the existing low-order solution. In addition, a finite element model is established to verify the accuracy of the asymptotic solution. The result shows that, compared with the existing low-order asymptotic solutions, the higher-order asymptotic solution agrees better with the existing numerical results and the newly developed numerical simulation results.

10 Study on preparation and properties of Ni-Fe bimetallic nanoparticles

LIU Hongxia , HUANG Xiaoyu , LIANG Jianjun , HUANG Donghong

2019, 42(12):81-88. DOI: 10.11835/j.issn.1000-582X.2019.12.010

[Abstract](636) [HTML](664) [PDF 4.02 M](1190)

Abstract:
To prepare zero-valent iron with excellent adsorptive and reducible properties, activated carbon was used in this experiment as a load, and modified with metal modification to obtain activated carbon-supported Ni/Fe bimetallic particles by electro-deposition. Ni/Fe-AC BPs were characterized by FESEM, EDS, and BET analyzer, and the Cr(Ⅵ) removal rate was used as the performance evaluation index. The results of single factor preparation test showed that the optimum deposition solution ratio was ferric sulfate 400 g/L, nickel sulfate 80 g/L, boric acid 40 g/L and manganese sulfate 60 g/L. The optimum electro-deposition conditions were current density 0.45 A/cm², temperature 40℃ and electrodeposition 10 min. Under these conditions, the removal rate of hexavalent chromium was as high as 100%. FESEM, EDS and XRD confirmed that the preparation of nickel-iron bimetallic particles was successful, and the prepared materials were flocculent and uniformly dispersed. The comparison tests of BET and AC, Fe-AC, Ni/Fe-AC BPs for chromium removal showed that the specific surface area of Ni/Fe-AC BPs was 47.6% smaller than AC, but the removal rate of Cr (VI) was 100%, while the adsorption rate of AC was only 5.43%. Therefore, Ni/Fe-AC BPs have a good catalytic reduction performance.

11 Phosphorus adsorption characteristics of the soils at different altitudes in water-level-fluctuating zone of Pengxi River

WANG Chong , FANG Fang , WANG Chao , YUAN Ziyue , ZHANG Rui , ZHOU Xiaoming , GUO Jinsong

2019, 42(12):89-98. DOI: 10.11835/j.issn.1000-582X.2019.12.011

[Abstract](763) [HTML](547) [PDF 1.19 M](865)

Abstract:
The phosphorus adsorption characteristics of the soils in water-level-fluctuating zone (WLFZ) have an important influence on the nutritional status of the reservoir water body. In order to study phosphorus adsorption characteristics of the soils at different altitudes in WLFZ, the 140 m, 145 m, 155 m, 165 m and 180 m altitudes soils of Shuangjiang in Pengxi River were selected for the thermodynamic experiment of phosphorus isothermal adsorption. The causes for the differences in phosphorus adsorption characteristics of soils from WLFZ were discussed. The results indicated that the adsorption-desorption equilibrium concentration (EPC) and the maximum adsorption amount (Q_max) of phosphorus gradually increased with the decrease of altitude, that is, the phosphorus adsorption capacity was enhanced. Combined with the analysis of the surface characteristics of the soil particles and that of the correlation between the adsorption characteristic parameters and the physical-chemical properties of the soil samples, it was considered that the soils from WLFZ had a smaller particle size distribution, higher organic matter content and Fe content, which were important factors affecting the phosphorus adsorption capacity, and the different characteristics of the soils were mainly affected by winter flooding sedimentation and summer rainfall erosion. Soils with low altitude has strong phosphorus adsorption capacity, which has certain positive significance for controlling eutrophication of the water bodies in Three Gorges Reservoir.

12 Build and application of safety evaluation indexes system for coal gasification enterprise based on fuzzy theory

ZHANG Lan , XU Jiang , WANG Kequan

2019, 42(12):99-110. DOI: 10.11835/j.issn.1000-582X.2019.12.012

[Abstract](644) [HTML](565) [PDF 1.01 M](1325)

Abstract:
In the process of coal gasification, there are many kinds of raw materials and products that are inflammable, explosive, poisonous and harmful, which can cause casualties and property losses. In order to evaluate comprehensively the risk level of safety production in coal gasification enterprises, we used the fuzzy comprehensive evaluation theory and selected the coal-to-methanol process, which is a typical coal gasification process, in a coal gasification enterprise in Chongqing as the study object to construct a reasonable indexes system of safety risk evaluation, and carried out fuzzy comprehensive safety evaluation of the enterprise.

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