Rock burst is a catastrophic dynamic disaster caused by sudden failure and instability of coal, loading paths play an important role in the failure of coal, the coal failure process is associated with charge exception...Rock burst is a catastrophic dynamic disaster caused by sudden failure and instability of coal, loading paths play an important role in the failure of coal, the coal failure process is associated with charge exception infonnation. Hence, violent coal failure mechanics and time-frequency domain distribution of charge signal such as rock burst under different loading paths should be studied in-depth. In this paper, grade and cyclic loading test were carried out for coal with impact tendency samples produced by blocks cored from 800 depth in Xiaoqing coal mine of the Tiefa coal group in northeast China. Theory discussion was carried out for the result of stress and strain, frequency-spectra analysis was conducted for the wavelet charge data, figures showing the evolution mechanism of mechanical properties and the relationship of timefrequency domain amplitude of charge signals in coal with different loading paths and stage were obtained. The failure process and characteristics of coal under different loading paths were summarized. It found that the loading path changed the manner of energy accelerate-release, there were more plastic strain generation in coal under cyclic loading than that under grade loading, the former was more likely to cause greater damage and failure, then the strength of coal under cyclic loading is generally lower than that under grade loading, an energy conversion mechanical model of stress, damage and deformation was developed and explained the effect of the loading path. Charge signal was primarily distributed in the strengthening and peak stages, where there was a high amplitude pulse at each stress drop. The charge pulse was a type of low frequency signal with a primary frequency distribution range of 1 -100Hz. Discussion on the charge generating mechanism from the perspective of friction slip, it demonstrated that the charge obtained during the coal failure process directly to stress loaded on and damage, the result verified it better. We propose that the research results in this study could be efficiently applied to daily mining activities, to provide an early warning and effectively avoid rock burst disaster.展开更多
The existence of space charge may be addressed as one of the reasons that could cause shielding failure of transmission lines. In order to study the effect of space charge on discharge propagation path, a new experime...The existence of space charge may be addressed as one of the reasons that could cause shielding failure of transmission lines. In order to study the effect of space charge on discharge propagation path, a new experimental system, including mainly DC high voltage generator, impulse voltage generator as well as rod-plane electrode, has been established. The space charge was generated around the rod by means of pre-applying DC high voltage, and the air gap dis- charge experiments were conducted with and without pre-applying DC high voltage, respectively. Meanwhile, high speed cameras worked simultaneously from the front and lateral side to record the discharge propagation path so as to obtain the curvature. After statistical analysis, it is shown that the curvature increases in the middle and lower portions of the propagation path when the effect of space charge is taken into account.展开更多
The new signature of liquid-gas phase transition has been well indicated by the higher-order fluctuations of the largest fragment charge,but the uncertainties of critical temperatures based on this signature have not ...The new signature of liquid-gas phase transition has been well indicated by the higher-order fluctuations of the largest fragment charge,but the uncertainties of critical temperatures based on this signature have not been revealed.This study extracts the critical temperatures of liquid-gas phase transition in nuclear reactions and investigates their uncertainties.Utilizing the isospin-dependent quantum molecular dynamics model in conjunction with the statistical model GEMINI enables us to describe the dynamical path from the initial to the final state.An isotope thermometer and a quantum fluctuation thermometer are employed to extract the nuclear temperature.The higher-order fluctuations of the largest fragment charge and critical temperatures are studied in^(124)Sn+^(120)Sn collisions ranging from 400 to 1000 MeV/nucleon and^(124)Sn+AZ collisions at 600 MeV/nucleon.Observations revealed that the pseudo-critical point is robustly indicated by the higher-order fluctuations of the largest fragment charge.The critical temperatures extracted by the isotope thermometer are relatively consistent,with an uncertainty of 15%,while those obtained by the quantum fluctuation thermometer are heavily influenced by the incident energy and mass number of target nuclei.The excitation energy E∗and bound charge Zbound are used for event-sorting.These two ensembles represent the statistical properties of the initial and final states of the system,respectively.The initial-final correlations of statistical properties might lead to two phenomena.First,the size distribution of the largest fragment at the pseudo-critical point based on the Zbound ensemble is wide,while that based on E∗ensemble exhibits bimodality,which is a typical characteristic in the liquid-gas coexistence of a finite system.Second,the temperature at the pseudo-critical point based on the Zbound ensemble is higher than that based on the E∗ensemble.Furthermore,the projectile-like system exhibits a significant dynamical effect in its evolution path from the initial to final state,closely associated with the fluctuation of critical temperature.展开更多
[目的/意义]技术路径识别能够得到表征技术发展的链接模式,挖掘技术方向及演变特征,对企业知悉技术路径发展有重要参考价值。[方法/过程]通过Web of Science和USPTO数据库对期刊文献和专利数据进行导出,利用Pajek软件分别构建期刊文献...[目的/意义]技术路径识别能够得到表征技术发展的链接模式,挖掘技术方向及演变特征,对企业知悉技术路径发展有重要参考价值。[方法/过程]通过Web of Science和USPTO数据库对期刊文献和专利数据进行导出,利用Pajek软件分别构建期刊文献和专利引文网络;对引文网络进行社群划分,提取最大的社群网络进行主路径识别;对双源主路径节点文献构建文本相似性矩阵,利用文本相似性算法将前述路径进行融合与连接,全面揭示技术发展路径。[结果/结论]提出了一种基于期刊文献与专利双源引文网络和文本相似性分析的技术路径识别及融合方法,将该方法应用于无线充电技术领域,揭示了无线充电技术的发展主线,验证了所提方法的可行性与实用性,为相关企业明晰技术路径提供了科学的决策理论支持。展开更多
基金the National Key Research & Development Program of China (2017YFC0804208)the National Nature Science Foundation of China (Grant Nos. 51774122. 5177404& 51504122)Scientific Research Foundation of State Key Lab. of Coal Mine Disaster Dynamics and Control (2011DA105287-FW 201605).
文摘Rock burst is a catastrophic dynamic disaster caused by sudden failure and instability of coal, loading paths play an important role in the failure of coal, the coal failure process is associated with charge exception infonnation. Hence, violent coal failure mechanics and time-frequency domain distribution of charge signal such as rock burst under different loading paths should be studied in-depth. In this paper, grade and cyclic loading test were carried out for coal with impact tendency samples produced by blocks cored from 800 depth in Xiaoqing coal mine of the Tiefa coal group in northeast China. Theory discussion was carried out for the result of stress and strain, frequency-spectra analysis was conducted for the wavelet charge data, figures showing the evolution mechanism of mechanical properties and the relationship of timefrequency domain amplitude of charge signals in coal with different loading paths and stage were obtained. The failure process and characteristics of coal under different loading paths were summarized. It found that the loading path changed the manner of energy accelerate-release, there were more plastic strain generation in coal under cyclic loading than that under grade loading, the former was more likely to cause greater damage and failure, then the strength of coal under cyclic loading is generally lower than that under grade loading, an energy conversion mechanical model of stress, damage and deformation was developed and explained the effect of the loading path. Charge signal was primarily distributed in the strengthening and peak stages, where there was a high amplitude pulse at each stress drop. The charge pulse was a type of low frequency signal with a primary frequency distribution range of 1 -100Hz. Discussion on the charge generating mechanism from the perspective of friction slip, it demonstrated that the charge obtained during the coal failure process directly to stress loaded on and damage, the result verified it better. We propose that the research results in this study could be efficiently applied to daily mining activities, to provide an early warning and effectively avoid rock burst disaster.
文摘The existence of space charge may be addressed as one of the reasons that could cause shielding failure of transmission lines. In order to study the effect of space charge on discharge propagation path, a new experimental system, including mainly DC high voltage generator, impulse voltage generator as well as rod-plane electrode, has been established. The space charge was generated around the rod by means of pre-applying DC high voltage, and the air gap dis- charge experiments were conducted with and without pre-applying DC high voltage, respectively. Meanwhile, high speed cameras worked simultaneously from the front and lateral side to record the discharge propagation path so as to obtain the curvature. After statistical analysis, it is shown that the curvature increases in the middle and lower portions of the propagation path when the effect of space charge is taken into account.
基金Supported by the National Natural Science Foundation of China (11875328, 12075327)the Key Laboratory of Nuclear Data foundation (JCKY2022201C157)the Fundamental Research Funds for the Central Universities, Sun Yat-sen University (22lgqb39)。
文摘The new signature of liquid-gas phase transition has been well indicated by the higher-order fluctuations of the largest fragment charge,but the uncertainties of critical temperatures based on this signature have not been revealed.This study extracts the critical temperatures of liquid-gas phase transition in nuclear reactions and investigates their uncertainties.Utilizing the isospin-dependent quantum molecular dynamics model in conjunction with the statistical model GEMINI enables us to describe the dynamical path from the initial to the final state.An isotope thermometer and a quantum fluctuation thermometer are employed to extract the nuclear temperature.The higher-order fluctuations of the largest fragment charge and critical temperatures are studied in^(124)Sn+^(120)Sn collisions ranging from 400 to 1000 MeV/nucleon and^(124)Sn+AZ collisions at 600 MeV/nucleon.Observations revealed that the pseudo-critical point is robustly indicated by the higher-order fluctuations of the largest fragment charge.The critical temperatures extracted by the isotope thermometer are relatively consistent,with an uncertainty of 15%,while those obtained by the quantum fluctuation thermometer are heavily influenced by the incident energy and mass number of target nuclei.The excitation energy E∗and bound charge Zbound are used for event-sorting.These two ensembles represent the statistical properties of the initial and final states of the system,respectively.The initial-final correlations of statistical properties might lead to two phenomena.First,the size distribution of the largest fragment at the pseudo-critical point based on the Zbound ensemble is wide,while that based on E∗ensemble exhibits bimodality,which is a typical characteristic in the liquid-gas coexistence of a finite system.Second,the temperature at the pseudo-critical point based on the Zbound ensemble is higher than that based on the E∗ensemble.Furthermore,the projectile-like system exhibits a significant dynamical effect in its evolution path from the initial to final state,closely associated with the fluctuation of critical temperature.
文摘[目的/意义]技术路径识别能够得到表征技术发展的链接模式,挖掘技术方向及演变特征,对企业知悉技术路径发展有重要参考价值。[方法/过程]通过Web of Science和USPTO数据库对期刊文献和专利数据进行导出,利用Pajek软件分别构建期刊文献和专利引文网络;对引文网络进行社群划分,提取最大的社群网络进行主路径识别;对双源主路径节点文献构建文本相似性矩阵,利用文本相似性算法将前述路径进行融合与连接,全面揭示技术发展路径。[结果/结论]提出了一种基于期刊文献与专利双源引文网络和文本相似性分析的技术路径识别及融合方法,将该方法应用于无线充电技术领域,揭示了无线充电技术的发展主线,验证了所提方法的可行性与实用性,为相关企业明晰技术路径提供了科学的决策理论支持。
