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2020, 40(6): .

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2020, 40(6): .

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Study of Dynamic Model for Bubble Impact and Bounce from Rigid Wall

YU Yong, LUO Song

2020, 40(6): 581-591. doi:10.15918/j.tbit1001-0645.2019.136

Abstract(933) PDF(441)

Abstract:
In order to understand the physical mechanism and detailed hydrodynamic process of the interaction between bubble and rigid wall, the dynamic process of the interaction between bubble and wall was analyzed and the development of theoretical model was summarized. The numerical solution was carried out by using the theoretical model established. When a bubble on millimeter size range collided with a rigid wall vertically, a liquid film was formed between the wall and the bubble surface. The abundant and complicated film appeared in different forms. Deformation of the bubble surface would change the distribution of pressure in the film and the film drainage process occurred. The bubble rebounded several times in the process of interaction with the wall until the kinetic energy was completely dissipated. In the dynamic model established, the film thickness was described by Stokes-Reynolds equation and the pressure distribution in the liquid film was calculated by Young-Laplace equation. The wall-induced force caused by pressure was introduced into the trajectory model of bubble. The results show that the wall induced force model based on the thin film lubrication approximation can predict the trajectory of bubbles with good accuracy and reflect the dynamic process of multiple rebounds of bubbles very well. The wall induced force plays a dominant role in the bubble motion in the process of collision. With the increase of bubble size and Reynolds number, the number of bubble rebounds will increase gradually. Whether bubble rebound or not and the number of rebounds are directly related to Reynolds number.

Isogeometric Analysis with Hierarchical B-Splines for Planar Structural Dynamics with Large Deformation

RONG Ji-li, XIONG Li-yuan, LIU Cheng, XIN Peng-fei, LIU Zhi-chao

2020, 40(6): 592-601. doi:10.15918/j.tbit1001-0645.2019.150

Abstract(1064) PDF(356)

Abstract:
In order to develop the adaptive mesh refinement algorithm for planar structural dynamics with large deformation, the construction of hierarchical B-spline basis functions for isogeometric analysis and the multi-level Bézier extraction approach restudied. In order to maintain the uniformity of element basis functions, the multi-level Bézier extraction approach was employed to present a standard element structure for the hierarchical B-spline during analysis process. Furthermore, the super-convergence patch recovery method was applied to obtain the reference stress in the adaptive analysis. Therefore, the refinement domain determined based on the energy norm error, which calculated via the reference stress and the numerical stress during the error estimation. Finally, the effectiveness and accuracy of the isogeometric analysis based on the hierarchical B-spline are validated by a static example of an elastic plate with circular hole and a planar structural dynamic example with large deformation.

Experimental Study on Influenceing Factors of Ignition Sensibility of Coal Dust Cloud

YU Hong-kun, WANG Cheng, PANG Lei, CHEN Dong-ping

2020, 40(6): 602-608. doi:10.15918/j.tbit1001-0645.2019.089

Abstract(1101) PDF(321)

Abstract:
In order to study the ignition sensibility of coal dust cloud, three kinds of typical pulverized coal-anthracite, bituminous coal and lignite-were chosen. And a Godbert-Greenwald oven was used to test the influence of different test conditions and coal dust types on the minimum ignition temperature (MIT) of coal dust and the suppression of coal dust cloud combustion by inert dust. The study found that the MIT of coal dust cloud first decreased and then rose with the increase of dust pressure. The optimal dust pressure was 50 kPa, on which condition the coal dust cloud ignition temperature arrived at minimum value. With the increase of coal dust particle size, the MIT of coal dust cloud showed a linear increase trend. With the increase of coal dust cloud concentration, the MIT of coal dust cloud decreased at first and then rose. For three kinds of coal dusts, all of them had a best ignition concentration. The best ignition concentration of coal-anthracite and bituminous coal was 1.818 g/L, and for lignite it was 1.364 g/L. The MIT of coal dust cloud decreased with the increase of volatility. For the coal dust which contained less than 15% volatility, the ash had obvious suppressive effect. When the content of volatility was more than 15%, the ash had little effect on the combustion of coal dust. The carbon black had the strongest inhibiting effect, coal fly ash had the second strongest inhibiting effect, and CaCO₃had the weakest inhibiting effect on the MIT of coal dust clouds. The research results can strengthen the understanding of the combustion law of coal dust, and provide reference for the protection of coal dust fire and explosion and risk assessment of coal dust.

Substrate Design and Stab-Resistant Mechanism of a New Type of Bionic Stab-Resistant Clothing

YUAN Meng-qi, GUO Ya-xin, QIAN Xin-ming

2020, 40(6): 609-616. doi:10.15918/j.tbit1001-0645.2019.175

Abstract(998) PDF(355)

Abstract:
To further develop lightweight and effective individual stab-resistant equipment, this study drew on the biological armor model of nature to design a bionic stab-resistant substrate with a triangular pyramidal structure. Numerical simulations and experimental testing of a knife impacting a substrate were used to study the impact-resistance behavior and stab-resistance mechanism of a triangular pyramidal stab-resistant substrate, and an optimal structural design was thus obtained. Because the triangular pyramidal structure had a dispersing effect on the knife impact force, the material could avoid the concentrated damage by the impact kinetic energy, giving the triangular pyramidal structure a much higher stab resistance than a comparable flat plate. The optimal angle of the triangular pyramidal stab-resistant substrate produced from a modified titanium alloy (TC611) material with excellent impact toughness was found to be 22.5° and the optimal thickness 1 mm. A full stab-resistant layer designed and manufactured using a new riveting method passed the knife impact test for police stab-resistant clothing in line with the GA 68-2008 standards. This clothing works more effectively against the impact of a knife, being lightweight, and having a shorter manufacturing cycle, and higher wearability.

Numerical Simulation of Hypervelocity Impact Based on the Optimal Transportation Meshfree Method

MA Tian-bao, SU Xin, HAO Li

2020, 40(6): 617-622. doi:10.15918/j.tbit1001-0645.2019.120

Abstract(1029) PDF(480)

Abstract:
Compared with the SPH method, the optimal transportation meshfree method (OTM) can effectively overcome the non-conservation of energy, and completely avoid the tensile instability and the zero energy mode. Numerical simulations of hypervelocity impact of aluminum alloy plates by aluminum spherical projectile were presented using the OTM method. The Johnson-Cook constitutive model and the Mie-Grüneisen state equation were employed to describe the dynamic response of aluminum subjected to high strain rates, high pressures and high temperatures. In the simulation of the impact on single plate, the OTM's numerical results of crater diameters, the width and the length of debris cloud and the core debris cloud's shape and distribution were in good agreement with the experimental results. Furthermore, the hypervelocity impact on double plates was also simulated by the OTM method, and the results indicated that the morphology characteristics of debris cloud fitted the experimental results well, and the error of secondary debris cloud's length between numerical and experimental results was only 2.6%. All the numerical results prove that the OTM method is more suitable for the simulation of hypervelocity impact.

The Influence of Bore Damage on Bullet's Exterior Ballistics Process

SHEN Chao, ZHOU Ke-dong, HE Lei, LU Ye, LI Jun-song

2020, 40(6): 623-631. doi:10.15918/j.tbit1001-0645.2019.147

Abstract(1060) PDF(411)

Abstract:
In order to study how the damaged bore influences bullet's aerodynamic characteristics and the exterior ballistics process, finite element models of damaged barrels at 4 life were established based on systematic life tests of 12.7 mm machine gun barrels to obtain bullets' surface morphologies at the muzzle. Simulations of the aerodynamic parameters for the high-speed spinning bullets with different surface morphologies were carried out adopting the computational fluid dynamics (CFD) method with the shear stress transport (SST)k-ωturbulent model. Uniform design method was used to arrange the interior ballistics computing process influenced by random factors, and the random response states of bullets' disturbances at the muzzle were acquired. A model of 6-D exterior ballistics of rigid bullets was set up, and the numerical calculation software was programmed combined with bullets' aerodynamic parameters and muzzle disturbances. The simulated results of the dispersion circle radius and the ratios of elliptical bullet holes of bullets shot from the barrels at 4 life fit well with the experimental data. The computed results show that the increase of bullets disturbances at muzzle, and the antedisplacement of pressure center of aerodynamic forces as well as the increase of Magnus moment coefficient are the major reasons for the decrease of bullet's flight stability and the terminal of a barrel's later life.

Study on Fractal Characteristics and Fracture Mechanism of Frozen Rocks

YANG Yang, LI Xiang-long, YANG Ren-shu, WANG Jian-guo

2020, 40(6): 632-639,682. doi:10.15918/j.tbit1001-0645.2019.169

Abstract(1123) PDF(369)

Abstract:
Through the dynamic impact test of pressure bar (SHPB), the dynamic mechanical properties of red sandstone under negative temperature were studied, and the influences of different negative temperature on rock strength properties, fractal dimension and dissipated energy were analyzed, and the reasons for the deterioration of rock dynamic mechanical properties under low negative temperature were analyzed in combination with micro-fracture morphology.The research shows that low negative temperature will cause "frostbite" of red sandstone. Under high strain rate loading, the rock will quickly lose its bearing capacity and its dynamic mechanical strength will drop sharply.The dissipated energyW_Lof frozen rock specimen is positively correlated with the fractal dimensionD, and closely related to the macroscopic failure characteristics. In other words, the greater the dissipated energy is, the more seriously the rock is broken, and the greater the corresponding fractal dimension is.Fracture morphology analysis shows that the lower negative temperature can make the red sandstone interface between internal material generate a large number of cracks, the crack tip poor, to instability under high strain rate loading low stress brittle fracture the composition of cement more susceptible to negative temperature effect, so the dynamic load and negative temperature cement, cause the collapse of the red sandstone as a whole.

Road Extraction Based on PSO Different Ratio Deconvolution Feature Fusion

PAN Feng, AN Qi-chao, DIAO Qi, WANG Rui, FENG Xiao-xue

2020, 40(6): 640-647. doi:10.15918/j.tbit1001-0645.2019.198

Abstract(1155) PDF(406)

Abstract:
To improve road extraction accuracy in complex scenes based on traditional FCN algorithm with different scales of multi-scale feature fusion,several works were carried out for the complex aerial road scene, designing a FROBIT farmland road dataset for farmland environment, extracting the road information from FROBIT dataset (farmland road) and Massachusetts road dataset (city road) based on full convolutional neural network (FCN), improving the deconvolution method based on traditional FCN network, implementing multi-scale feature fusion with different proportions based on particle swarm optimization (PSO). Comparing the multi-scale FCN network proposed in this paper with the traditional FCN neural network on the FROBIT dataset and the Massachusetts road dataset, the experimental results show that the multi-scale FCN network is superior to the traditional FCN neural network in extraction accuracy.

Multi-Tier Transmission Control of Marine Observation Data

CHANG Hao-tian, FENG Jing, DUAN Chao-fan, YAN Chao, XIA Kai-wen

2020, 40(6): 648-654. doi:10.15918/j.tbit1001-0645.2020.056

Abstract(1205) PDF(434)

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The sea-air-space integrated network (SASIN) and collaborative data transmission mechanism were proposed. By complementing cruising nodes with access points, such as UAVs and unmanned boats, the buoy/submarine buoy data was partially collected, processed and forwarded to the data center, thus increasing the overall data transmission efficiency and reducing the transmission delay. This paper studied the joint scheduling control mechanism of virtual machine allocation, task scheduling and computation task offloading in SASIN. In this paper, aQ-learning based computational offloading method was proposed in dynamic network conditions, so as to deal with the multi-dimension resource scheduling of the SASIN.

Cave Targets Recognition on Meta-Convolutional Networks and Lifelong Learning

CHEN Ke-shan, XUE Xu, JIA Bo-ran, SONG Peng-liang, MEI Yu-qing

2020, 40(6): 655-660. doi:10.15918/j.tbit1001-0645.2019.148

Abstract(1165) PDF(359)

Abstract:
Cave target is the high-value recognizing target. According to the difficulty about cave target data collection, the high data similarity, the limitation of the artificial feature, and the deep neural networks needs massive data, a method of combining meta-convolutional network and deep convolutional networks named meta-convolutional networks(MCNN), and combining lifelong learning was proposed (MCNN-LLS). Firstly, a meta-convolutional network was established by combining deep convolutional network and meta-learning. This network can use old knowledge to guide the training process, and can use the small sample to train an ideal cave detection model. Then combining lifelong learning and establishing the lifelong learning system (LLS), designing the expert review model to identify the recognition results by the cave detection model, and introducing potential tasks, model asynchronously update to reach the effect of model sustainable updating. Experiments show that this method only needs small sample, has high accuracy of recognizing cave target, and the recognition effect can gradually increase with the accumulation of new data.

Adaptive Squeezed State Phase Estimation Based on Extended Kalman-Bucy Filter

CHEN Shu-xin, XU Han, WU Hao, FANG Liang, CUI Jun-hui, ZHONG Hui

2020, 40(6): 661-666,686. doi:10.15918/j.tbit1001-0645.2019.078

Abstract(1007) PDF(373)

Abstract:
It's expected to improve the positioning accuracy beyond the classical theory by using quantum parameter estimation theory to obtain the phase parameters in navigation angle measurement. When the phase squeezed state is detected by homodyne, the local oscillator phase should be orthogonal to the phase to be measured. In order to satisfy this condition, at the same time, considering the characteristics of nonlinear and real-time of the navigation system, a homodyne phase locked loop was designed based on extended Kalman-Bucy filter to provide real-time feedback control for the phase of the local oscillator and realize the real-time estimation of the phase of squeezed state. Theoretical analysis and simulation results show that, using squeezed state as a signal field to obtain the phase parameter, it can not only break through the limitation of shot noise, but also improve the positioning accuracy of navigation angle measuring system. And the phase estimation accuracy is the highest under the optimal squeezing level which depends on the intensity of the squeezed state and the phase stability of the measurement system.

Thermosensitive Molecularly Imprinted Quantum Dots as Biosensor for the Detection of Bovine Hemoglobin

LUO Ai-qin, LIU Hong-yang, ZHANG Xin, CHEN Wei-jie, LI Yuan-yuan, SUN Li-quan

2020, 40(6): 667-673. doi:10.15918/j.tbit1001-0645.2019.059

Abstract(1001) PDF(337)

Abstract:
A thermosensitive biosensor based on molecularly imprinted quantum dots (QD@MIPs) was developed and used for rapid detection of bovine hemoglobin (BHb). The experimental results show that, the prepared QD@MIPs can provide a fast fluorescence response to BHb and achieve the adsorption equilibrium in 15 min. Under optimal conditions, the fluorescence quenching of BHb is proportional to the concentration in the range of 0.15~2.3μmol/L with a correlation coefficient of 0.986 9, and the detection limit is 0.097μmol/L. Moreover, the prepared QD@MIPs possesses thermosensitive, this feature can endow it rapid adsorption and release of template protein by changing the temperature in bio-analysis.

EPDM Flame Retardant & Thermal Protection Material in Thermal Runaway of Lithium-ion Batteries

LI Xiang-mei, QIAO Yu, WANG Shu-ping, CHEN Jing-hui, FAN Ming-hao, GAO Fei, HE Ji-yu, YANG Kai, YANG Rong-jie

2020, 40(6): 674-682. doi:10.15918/j.tbit1001-0645.2019.249

Abstract(1393) PDF(378)

Abstract:
The effects of flame retardant and material thickness on the properties of ethylene propylene diene monomer (EPDM) flame retardant thermal protection materials were investigated, and the application of flame retardant EPDM in the lithium-ion battery pack was evaluated. Results show that, the back temperature of EPDM with flame retardant is lower than the temperature of EPDM without flame retardant, the back temperature of EPDM decreases and the flame retardant performance improves with the load of flame retardant and the increase of sample thickness. When the ignition temperature is 500℃, the final stable back temperatures of EPDM with a thickness of 3 mm and 6 mm are 185.1℃ and 165.7℃ respectively. Taking the flame retardant EPDM with 3 mm thickness as the protection of the lithium-ion battery pack, a thermal runaway test was carried out. The test results show that, only one battery explosion occurs with thermal protection, and all five batteries explode without thermal protection in the battery pack. And then, taking a battery pack as the center of the area coverage, an explosion experiment of the lithium-ion battery pack was completed to analyze the thermal protection effect of flame retardant EPDM. The results show that, the temperature of the battery pack in the surround region about the radius 30 cm can be affected by the explosion of the battery without thermal protection of flame retardant EPDM, causing the field temperature up to 300℃, being very dangerous. After protecting the lithium-ion battery with EPDM thermal protection material, the temperature in this area fluctuates between 20~28℃, which is a very safe temperature range.

A Recursive Weighted Least Squares Optimization Method for Sensor Nodes Positioning in Wireless Sensor Networks

MIRAU Silas, XU Hao, SONG Yang, SUN Hua-fei

2020, 40(6): 683-686. doi:10.15918/j.tbit1001-0645.2019.047

Abstract(912) PDF(416)

Abstract:
To study the signal source location based on received signal strength measurement, a least squares optimization algorithm was proposed. Firstly, a linear model was established to calculate path loss. Then, the weighted least squares method was introduced. And a recursive weighted least squares optimization method was presented for sensor node location in wireless sensor networks. Finally, the algorithm proposed in this paper with the two algorithms based on RSS was compared. The simulation results show that, the iterative weighted least squares method presented can greatly improve the positioning accuracy.

Operator Weighted Concurrence Measure on Two-Qubit Quantum System

AUNG Khaing Zaw, LIU Kai, JIANG Li-ning

2020, 40(6): 687-690. doi:10.15918/j.tbit1001-0645.2019.106

Abstract(1011) PDF(925)

Abstract:
Based on the operator theory in Hilbert space, the definition of operator weighted concurrence entanglement measure was introduced by means of a reduced matrix of quantum states. The efficiency in identifying the entanglement of a quantum state was also analyzed. Together with some properties, the relation and consistency between the measure and quantum channels was studied in the meantime.

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