Spontaneous combustion of coal increases the temperature in adjoining overburden strata of coal seams and poses a challenge when loading blastholes.This condition,known as hot-hole blasting,is dangerous due to the inc...Spontaneous combustion of coal increases the temperature in adjoining overburden strata of coal seams and poses a challenge when loading blastholes.This condition,known as hot-hole blasting,is dangerous due to the increased possibility of premature explosions in loaded blastholes.Thus,it is crucial to load the blastholes with an appropriate amount of explosives within a short period to avoid premature detonation caused by high temperatures of blastholes.Additionally,it will help achieve the desired fragment size.This study tried to ascertain the most influencial variables of mean fragment size and their optimum values adopted for blasting in a fiery seam.Data on blast design,rock mass,and fragmentation of 100 blasts in fiery seams of a coal mine were collected and used to develop mean fragmentation prediction models using soft computational techniques.The coefficient of determination(R^(2)),root mean square error(RMSE),mean absolute error(MAE),mean square error(MSE),variance account for(VAF)and coefficient of efficiency in percentage(CE)were calculated to validate the results.It indicates that the random forest algorithm(RFA)outperforms the artificial neural network(ANN),response surface method(RSM),and decision tree(DT).The values of R^(2),RMSE,MAE,MSE,VAF,and CE for RFA are 0.94,0.034,0.027,0.001,93.58,and 93.01,respectively.Multiple parametric sensitivity analyses(MPSAs)of the input variables showed that the Schmidt hammer rebound number and spacing-to-burden ratio are the most influencial variables for the blast fragment size.The analysis was finally used to define the best blast design variables to achieve optimum fragment size from blasting.The optimum factor values for RFA of S/B,ld/B and ls/ld are 1.03,1.85 and 0.7,respectively.展开更多
针对二次泵变流量空调冷冻水系统采取的回水温度PID控制方式,往往导致稳态误差与超调量均较大和调节时间较长等问题。鉴于此,提出了回水温度PI^(λ)D^(μ)-供水流量PI^(λ)串级控制策略和改进的粒子群算法实施串级控制器参数整定的设计...针对二次泵变流量空调冷冻水系统采取的回水温度PID控制方式,往往导致稳态误差与超调量均较大和调节时间较长等问题。鉴于此,提出了回水温度PI^(λ)D^(μ)-供水流量PI^(λ)串级控制策略和改进的粒子群算法实施串级控制器参数整定的设计方案。根据二次泵变流量空调冷冻水系统的工艺要求和相关自动控制理论,对该回水温度PI^(λ)D^(μ)-供水流量PI^(λ)串级系统的各个组成环节,如主、副被控对象及回水温度PI^(λ)D^(μ)控制器(Fractional Order PID Controller for Backwater Temperature,BT-FOPIDC)和供水流量PI^(λ)控制器(Fractional Order PI Controller for the Flow of Water Supply,FWS-FOPIC)等进行建模。引入正切三角函数对基本粒子群算法中的惯性权重进行非线性递减的改变,构建改进的粒子群算法(Modified Particle Swarm Algorithm,MPSA),对这两个串级控制器的参数进行整定,获取8个参数最佳值。借助MATLAB软件,对该回水温度PI^(λ)D^(μ)-供水流量PI^(λ)串级系统进行组态和仿真运行。结果表明,该分数阶串级控制系统及其基于MPSA的控制器参数整定在理论上是可行的,且控制效果优于传统的回水温度PID单回路控制系统。展开更多
针对卫星网络动态环境下的高速信息传输、业务类型差异大等特点,提出一种综合考虑各业务QoS(Quality of Service)指标的可靠性分析方法。在卫星通信网络实际运行周期内,通信系统往往处于逐渐劣化过程中,导致卫星的节点和链路除正常工作...针对卫星网络动态环境下的高速信息传输、业务类型差异大等特点,提出一种综合考虑各业务QoS(Quality of Service)指标的可靠性分析方法。在卫星通信网络实际运行周期内,通信系统往往处于逐渐劣化过程中,导致卫星的节点和链路除正常工作和完全失效外,还存在部分失效的工作状态。本文在链路多状态基础上基于最小路集算法(Minimum Path Set Algorithms,MPSA)在不同业务的QoS指标(时延、带宽和丢包率)约束下,得出满足该业务QoS约束的所有可靠路径集,对路径集中路径进行不交化处理得到网络端-端可靠性。研究结果表明,不同业务由于QoS需求的差异导致网络端-端可靠性不同,所提算法与传统算法相比更加符合实际。由于实际卫星网络环境中会采用端-端并行多路径传输(Multi-Path Transmission,MTP),本文在上述研究的基础上,进一步对多路径的端-端可靠性进行了研究,结果表明多路径数据传输可靠性高。展开更多
New Yorkers often say that it is easier to get their kids into Harvard University than into a top-tier pri-vate preschool. This may be an exaggeration but it＇s not far from the truth, said Amanda Uhry, founder and Pr...New Yorkers often say that it is easier to get their kids into Harvard University than into a top-tier pri-vate preschool. This may be an exaggeration but it＇s not far from the truth, said Amanda Uhry, founder and President of Manhattan Private School Advisors （MPSA）, the city＇s largest private school advisory tirol.展开更多
文摘Spontaneous combustion of coal increases the temperature in adjoining overburden strata of coal seams and poses a challenge when loading blastholes.This condition,known as hot-hole blasting,is dangerous due to the increased possibility of premature explosions in loaded blastholes.Thus,it is crucial to load the blastholes with an appropriate amount of explosives within a short period to avoid premature detonation caused by high temperatures of blastholes.Additionally,it will help achieve the desired fragment size.This study tried to ascertain the most influencial variables of mean fragment size and their optimum values adopted for blasting in a fiery seam.Data on blast design,rock mass,and fragmentation of 100 blasts in fiery seams of a coal mine were collected and used to develop mean fragmentation prediction models using soft computational techniques.The coefficient of determination(R^(2)),root mean square error(RMSE),mean absolute error(MAE),mean square error(MSE),variance account for(VAF)and coefficient of efficiency in percentage(CE)were calculated to validate the results.It indicates that the random forest algorithm(RFA)outperforms the artificial neural network(ANN),response surface method(RSM),and decision tree(DT).The values of R^(2),RMSE,MAE,MSE,VAF,and CE for RFA are 0.94,0.034,0.027,0.001,93.58,and 93.01,respectively.Multiple parametric sensitivity analyses(MPSAs)of the input variables showed that the Schmidt hammer rebound number and spacing-to-burden ratio are the most influencial variables for the blast fragment size.The analysis was finally used to define the best blast design variables to achieve optimum fragment size from blasting.The optimum factor values for RFA of S/B,ld/B and ls/ld are 1.03,1.85 and 0.7,respectively.
文摘针对二次泵变流量空调冷冻水系统采取的回水温度PID控制方式,往往导致稳态误差与超调量均较大和调节时间较长等问题。鉴于此,提出了回水温度PI^(λ)D^(μ)-供水流量PI^(λ)串级控制策略和改进的粒子群算法实施串级控制器参数整定的设计方案。根据二次泵变流量空调冷冻水系统的工艺要求和相关自动控制理论,对该回水温度PI^(λ)D^(μ)-供水流量PI^(λ)串级系统的各个组成环节,如主、副被控对象及回水温度PI^(λ)D^(μ)控制器(Fractional Order PID Controller for Backwater Temperature,BT-FOPIDC)和供水流量PI^(λ)控制器(Fractional Order PI Controller for the Flow of Water Supply,FWS-FOPIC)等进行建模。引入正切三角函数对基本粒子群算法中的惯性权重进行非线性递减的改变,构建改进的粒子群算法(Modified Particle Swarm Algorithm,MPSA),对这两个串级控制器的参数进行整定,获取8个参数最佳值。借助MATLAB软件,对该回水温度PI^(λ)D^(μ)-供水流量PI^(λ)串级系统进行组态和仿真运行。结果表明,该分数阶串级控制系统及其基于MPSA的控制器参数整定在理论上是可行的,且控制效果优于传统的回水温度PID单回路控制系统。
文摘针对卫星网络动态环境下的高速信息传输、业务类型差异大等特点,提出一种综合考虑各业务QoS(Quality of Service)指标的可靠性分析方法。在卫星通信网络实际运行周期内,通信系统往往处于逐渐劣化过程中,导致卫星的节点和链路除正常工作和完全失效外,还存在部分失效的工作状态。本文在链路多状态基础上基于最小路集算法(Minimum Path Set Algorithms,MPSA)在不同业务的QoS指标(时延、带宽和丢包率)约束下,得出满足该业务QoS约束的所有可靠路径集,对路径集中路径进行不交化处理得到网络端-端可靠性。研究结果表明,不同业务由于QoS需求的差异导致网络端-端可靠性不同,所提算法与传统算法相比更加符合实际。由于实际卫星网络环境中会采用端-端并行多路径传输(Multi-Path Transmission,MTP),本文在上述研究的基础上,进一步对多路径的端-端可靠性进行了研究,结果表明多路径数据传输可靠性高。
文摘New Yorkers often say that it is easier to get their kids into Harvard University than into a top-tier pri-vate preschool. This may be an exaggeration but it＇s not far from the truth, said Amanda Uhry, founder and President of Manhattan Private School Advisors （MPSA）, the city＇s largest private school advisory tirol.
