Desorption rate index(DRI)was presented to the Australian underground coal industry in 1995 as a means for determining outburst threshold limits for Australian coal seams.DRI is a measure of the gas volume released fr...Desorption rate index(DRI)was presented to the Australian underground coal industry in 1995 as a means for determining outburst threshold limits for Australian coal seams.DRI is a measure of the gas volume released from a coal sample in the first 30 s of crushing during the Q3 stage of gas content testing,multiplied by the ratio between measured Q3 and QM.Relationships were identified between QM and DRI for both CO2 and CH4 rich coal samples collected from the Bulli Seam at West Cliff Colliery and that identified relationship was referred to as the Bulli Seam Benchmark.The outburst mining gas content threshold limit values specified for the Bulli Seam at that time,when applied to the QM-DRI Bulli Seam benchmark,was shown to closely align with a DRI value of 900(DRI900),for both CO2 and CH4 rich seam gas conditions.The Australian coal industry adopted the DRI900 as the basis for determining outburst gas content TLV for Australian coal seams.Outburst mining experience in Australia has shown that gas content is not the only significant factor that impacts outburst risk,as all significant outburst events have been associated with abnormal geological conditions,such as faults and dykes.Therefore,assessing the potential application of additional outburst risk factors,to accurately define outburst risk zones,set safe mining threshold levels,and determine appropriate mining controls,warrants further investigation.Several Australian coal mines have implemented mining procedures enabling mining to continue in areas with gas content greater than the TLV determined using the DRI900 approach,without inducing an outburst.There is a broad lack of understanding among Australian coal mine operators as to the procedure and calculations used to determine DRI.Also,there has been growing concern regarding the accuracy and validity of the DRI900 method for determining outburst TLV.A comprehensive set of gas data has been collected from Australian coal seams,including the Bulli Seam,and this data has been used to investigate the DRI,Bulli Seam Benchmark,and the applicability of using DRI900 as the basis for assessing outburst risk and determining gas content TLV.The results are presented and discussed.展开更多
This paper proposes a method for measuring the stimulated Brillouin scattering （SBS） threshold based on waveform variation of SBS optical limiting. The output waveforms for different pump power densities are numeric...This paper proposes a method for measuring the stimulated Brillouin scattering （SBS） threshold based on waveform variation of SBS optical limiting. The output waveforms for different pump power densities are numerically simulated, and validated in the Nd：YAG seed-injected laser system. The results indicate that SBS does not take place in the case of a low pump power density and thus the output power scales up linearly with pump power. Once the pump power density exceeds the SBS threshold, SBS takes place and thereby the energies are transferred from pump to Stokes. As a result, a small shoulder appears in the trailing edge of the output waveform, which provides another method to determine the SBS threshold.展开更多
The uniformity of threshold voltage and threshold current in the In2 Se3 nanowire-based phase change memory （PCM） devices is investigated. Based on the trap-limited transport model, amorphous layer thickness, trap d...The uniformity of threshold voltage and threshold current in the In2 Se3 nanowire-based phase change memory （PCM） devices is investigated. Based on the trap-limited transport model, amorphous layer thickness, trap density, and trap depth are considered to clarify their influences upon the threshold voltage and threshold current through simulations.展开更多
We consider the response of a test subject upon a skin area being heated with an electromagnetic wave or a contact surface. When the specifications of the electromagnetic beam are fixed, the stimulus is solely describ...We consider the response of a test subject upon a skin area being heated with an electromagnetic wave or a contact surface. When the specifications of the electromagnetic beam are fixed, the stimulus is solely described by the heating duration. The binary response of a subject, escape or no escape, is determined by the stimulus and a subjective threshold that varies among test realizations. We study four methods for inferring the median subjective threshold in psychophysical experiments: 1) sample median, 2) maximum likelihood estimation (MLE) with 2 variables, 3) MLE with 1 variable, and 4) adaptive Bayesian method. While methods 1 - 3 require samples of time to escape measured in the method of limits, method 4 utilizes binary outcomes observed in the method of constant stimuli. We find that a) the adaptive Bayesian method converges and is as efficient as the sample median even when the assumed model distribution is incorrect;b) this robust convergence is lost if we infer the mean instead of the median;c) for the optimal performance in an uncertain situation, it is best to use a wide model distribution;d) the predicted error from the posterior standard deviation is unreliable, dominated by the assumed model distribution.展开更多
基金ACARPthe Australian underground coal mine operators who have supported this research project
文摘Desorption rate index(DRI)was presented to the Australian underground coal industry in 1995 as a means for determining outburst threshold limits for Australian coal seams.DRI is a measure of the gas volume released from a coal sample in the first 30 s of crushing during the Q3 stage of gas content testing,multiplied by the ratio between measured Q3 and QM.Relationships were identified between QM and DRI for both CO2 and CH4 rich coal samples collected from the Bulli Seam at West Cliff Colliery and that identified relationship was referred to as the Bulli Seam Benchmark.The outburst mining gas content threshold limit values specified for the Bulli Seam at that time,when applied to the QM-DRI Bulli Seam benchmark,was shown to closely align with a DRI value of 900(DRI900),for both CO2 and CH4 rich seam gas conditions.The Australian coal industry adopted the DRI900 as the basis for determining outburst gas content TLV for Australian coal seams.Outburst mining experience in Australia has shown that gas content is not the only significant factor that impacts outburst risk,as all significant outburst events have been associated with abnormal geological conditions,such as faults and dykes.Therefore,assessing the potential application of additional outburst risk factors,to accurately define outburst risk zones,set safe mining threshold levels,and determine appropriate mining controls,warrants further investigation.Several Australian coal mines have implemented mining procedures enabling mining to continue in areas with gas content greater than the TLV determined using the DRI900 approach,without inducing an outburst.There is a broad lack of understanding among Australian coal mine operators as to the procedure and calculations used to determine DRI.Also,there has been growing concern regarding the accuracy and validity of the DRI900 method for determining outburst TLV.A comprehensive set of gas data has been collected from Australian coal seams,including the Bulli Seam,and this data has been used to investigate the DRI,Bulli Seam Benchmark,and the applicability of using DRI900 as the basis for assessing outburst risk and determining gas content TLV.The results are presented and discussed.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 60778019 and 60878005)the Program for New Century Excellent Talents in University (Grant No NCET-08-0173)the Program of Excellent Team in Harbin Institute of Technology and the Program of Science and Technology of the Education Bureau of Heilongjiang Province,China (Grant No11521048)
文摘This paper proposes a method for measuring the stimulated Brillouin scattering （SBS） threshold based on waveform variation of SBS optical limiting. The output waveforms for different pump power densities are numerically simulated, and validated in the Nd：YAG seed-injected laser system. The results indicate that SBS does not take place in the case of a low pump power density and thus the output power scales up linearly with pump power. Once the pump power density exceeds the SBS threshold, SBS takes place and thereby the energies are transferred from pump to Stokes. As a result, a small shoulder appears in the trailing edge of the output waveform, which provides another method to determine the SBS threshold.
基金supported by the National Basic Research Program of China(Grant No.2011CBA00604)
文摘The uniformity of threshold voltage and threshold current in the In2 Se3 nanowire-based phase change memory （PCM） devices is investigated. Based on the trap-limited transport model, amorphous layer thickness, trap density, and trap depth are considered to clarify their influences upon the threshold voltage and threshold current through simulations.
文摘We consider the response of a test subject upon a skin area being heated with an electromagnetic wave or a contact surface. When the specifications of the electromagnetic beam are fixed, the stimulus is solely described by the heating duration. The binary response of a subject, escape or no escape, is determined by the stimulus and a subjective threshold that varies among test realizations. We study four methods for inferring the median subjective threshold in psychophysical experiments: 1) sample median, 2) maximum likelihood estimation (MLE) with 2 variables, 3) MLE with 1 variable, and 4) adaptive Bayesian method. While methods 1 - 3 require samples of time to escape measured in the method of limits, method 4 utilizes binary outcomes observed in the method of constant stimuli. We find that a) the adaptive Bayesian method converges and is as efficient as the sample median even when the assumed model distribution is incorrect;b) this robust convergence is lost if we infer the mean instead of the median;c) for the optimal performance in an uncertain situation, it is best to use a wide model distribution;d) the predicted error from the posterior standard deviation is unreliable, dominated by the assumed model distribution.
