In longwall mines, atmospheric pressure fluctuations can disturb the pressure balance between the gob and the ventilated working area, resulting in a phenomenon known as ‘‘gob breathing". Gob breathing triggers...In longwall mines, atmospheric pressure fluctuations can disturb the pressure balance between the gob and the ventilated working area, resulting in a phenomenon known as ‘‘gob breathing". Gob breathing triggers gas flows across the gob and the working areas and may result in a condition where an oxygen deficient mixture or a methane accumulation in the gob flows into the face area. Computational Fluid Dynamics(CFDs) modeling was carried out to analyze this phenomenon and its impact on the development of an explosive mixture in a bleeder-ventilated panel scheme. Simulation results indicate that the outgassing and ingassing across the gob and the formation of Explosive Gas Zones(EGZs) are directly affected by atmospheric pressure changes. In the location where methane zones interface with mine air, EGZ fringes may form along the face and in the bleeder entries. These findings help assess the methane ignition and explosion risks associated with fluctuating atmospheric pressures.展开更多
In order to improve the utilization rate of foam,an arc jet nozzle was designed for precise dust control.Through theoretical analysis,the different demands of foam were compared amongst arc jets,flat jets and full con...In order to improve the utilization rate of foam,an arc jet nozzle was designed for precise dust control.Through theoretical analysis,the different demands of foam were compared amongst arc jets,flat jets and full cone jets when the dust source was covered identically by foam.It is proved that foam consumption was least when an arc jet was used.Foam production capability of an arc jet nozzle under different conditions was investigated through experiments.The results show that with the gas liquid ratio(GLR)increasing,the spray state of an arc jet nozzle presents successively water jet,foam jet and mist.Under a reasonable working condition range of foam production and a fixed GLR,foam production quantity increases at first,and then decreases with the increase of liquid supply quantity.When the inner diameter of the nozzle is 14 mm,the best GLR is 30 and the optimum liquid supply quantity is0.375 m^3/h.The results of field experiments show that the total dust and respirable dust suppression efficiency of arc jet nozzles is 85.8%and 82.6%respectively,which are 1.39 and 1.37 times higher than the full cone nozzles and 1.20 and 1.19 times higher than the fiat nozzles.展开更多
In this paper, the authors will study the estimation of maintenance efficiency in Arithmetic Reduction of Intensity （ARI） and Arithmetic Reduction of Age （ARA） models with a memory m. These models have been propos...In this paper, the authors will study the estimation of maintenance efficiency in Arithmetic Reduction of Intensity （ARI） and Arithmetic Reduction of Age （ARA） models with a memory m. These models have been proposed by Doyen （2005）, the failure process is simply Non Homogeneous Poisson Process （NHPP）. Our models are defined by reformulation of ARI and ARA ones using bathtub failure intensity. This form is presented like a superposition of two NHPP and Homogeneous Poisson Process （HPP）. Moreover, the particularity of this model allows taking account of system state improvement in time course. The maintenance effect is characterized by the change induced on the failure intensity before and after failure during degradation period. To simplify study, the asymptotic properties of failure process are derived. Then, the asymptotic normality of several maintenance efficiency estimators can be proved in the case where the failure process without maintenance is known. Practically, the coverage rate of the asymptotic confidence intervals issued from those estimators is studied.展开更多
To investigate airflow pattern and its impact on particle deposition, finite-volume based computational fluid dynamics （CFD） simulations were conducted in the diseased triple-bifitrcation airways. Computations were ...To investigate airflow pattern and its impact on particle deposition, finite-volume based computational fluid dynamics （CFD） simulations were conducted in the diseased triple-bifitrcation airways. Computations were carried out for twenty Reynolds numbers ranging from 100 to 2 000 in the step of 100. Particles in the size range of 1-10 μm were conducted. Two particle deposition mechanisms （gravitational sedimentation and inertial impaction） were considered. The results indicate that there are strong relationship between airflow structures and particle deposition patterns. Deposition efficiency is different for different particles in the whole range of the respiratory rates. Particles in different sizes can deposit at different sites. Smaller particles can be uniformly deposited at the inside wall of the considered model. Larger particles can be mainly deposited in the proximal bifurcations. Deposition fraction varies a lot for different inlet Reynolds numbers. For lower Reynolds numbers, deposition fraction is relatively small and varies a little with varying the diameters. For Reynolds number to target the aerosols at the specific site. higher Reynolds numbers, there is a most efficient diameter for each展开更多
Objective Bronchoscopy has been extensively used in the diagnosis of respiratory diseases, and par- ticularly, malignant diseases. However, endoscopists do not normally perform bronchoscopic biopsy in Case lesions are...Objective Bronchoscopy has been extensively used in the diagnosis of respiratory diseases, and par- ticularly, malignant diseases. However, endoscopists do not normally perform bronchoscopic biopsy in Case lesions are undetected via bronchoscopy. The aim of this study was to evaluate whether performing bron- choscopic biopsy could be established in the diagnosis of lung cancer in case of endobronchial abnormali- ties undetectable to the naked eye. Methods We retrospectively analyzed 109 cases between January 2008 and December 2012. The in- clusion criteria were confirmed lung cancer diagnosis, transbronchial biopsy performed in the absence of visible endobronchial manifestations, brushing, and bronchoalveolar lavage （BAL） according to the images obtained from high-resolution computed tomography （HRCT）. Data regarding age, sex, pathology, tumor stage; the method of diagnosis; location of primary lesion （central, peripheral, or intermediate）; tumor size, mediastinal lymph node metastasis, and the serum carcinoembryonic antigen （CEA） value were collected. The Pearson chi-square test or Fisher＇s exact and McNemar tests were used in the univadate analysis. Results Among the 109 patients, the diagnosis of 37 （33.9%） patients was confirmed through bronchos- copy. Brushing and BAL had higher positive detection rates than biopsy （P = 0.004）. There were no differ- ences in the positive detection rates between the sex, pathology, lesion location, tumor size, lymph node metastasis, and the serum CEA value （P〈 0.05 for all groups）. Conclusion Despite the normal appearance of the endobronchial manifestations, lesions undetectable by bronchoscopy could be indicated. Therefore, we suggest performing bronchoscopic biopsy and that brushing and BAL might increase the positive detection rate of bronchoscepic examination.展开更多
This paper introduces a design to improve the radiotherapy accuracy of gamma knife. In this design, sensor is used to collect respiratory parameters and tumor displacement (caused by human respiration) model is establ...This paper introduces a design to improve the radiotherapy accuracy of gamma knife. In this design, sensor is used to collect respiratory parameters and tumor displacement (caused by human respiration) model is established through optimization modeling. At the same time, data are transferred to single chip microcomputer (SCM) system by pressure sensor and then stepping motor is controlled by SCM. Finally, the intelligent positioning bed is under the control of stepping motor. As a result, the intelligent positioning bed can move reverse to respiratory law. The experimental results showed that this method can reduce the influence of respiration on tumor displacement, improving the accuracy of intelligent positioning bed with simple circuit and low cost at the same time.展开更多
In this study, a membraneless, monolithic micro photocatalytic fuel cell with an air-breathing cathode was developed for simultaneous wastewater treatment and electricity generation. In this newly-developed micro phot...In this study, a membraneless, monolithic micro photocatalytic fuel cell with an air-breathing cathode was developed for simultaneous wastewater treatment and electricity generation. In this newly-developed micro photocatalytic fuel cell, the photoanode and cathode were arranged with a shoulder-to-shoulder design, forming two planar electrodes. Such design offers several advantages of enhanced mass transfer, uniform light distribution, short light transfer path, membrane elimination and easy fabrication, integration, and compatibility with other microdevices. The performance of this type fuel cell was evaluated by using methanol as a model pollutant under the alkaline condition. Experimental results indicated the developed micro photocatalytic fuel cell was able to show good photo-response to the illumination and satisfactory performance as well as durability. Parametric study on the cell performance was also performed. It was found that increasing the light intensity, methanol concentration andKOH concentration could improve the cell performance. But for the effect of the liquid flow rate, it was shown that the cell performance firstly increased with increasing the liquid flow rate and then decreased with further increasing the liquid flow rate. This study not only opens a new avenue for the design of the micro photocatalytic fuel cell but also is helpful for the optimization of the operating conditions.展开更多
基金the financial support of the National Institute for Occupational Safety and Health–United States(No.211-2014-60050)
文摘In longwall mines, atmospheric pressure fluctuations can disturb the pressure balance between the gob and the ventilated working area, resulting in a phenomenon known as ‘‘gob breathing". Gob breathing triggers gas flows across the gob and the working areas and may result in a condition where an oxygen deficient mixture or a methane accumulation in the gob flows into the face area. Computational Fluid Dynamics(CFDs) modeling was carried out to analyze this phenomenon and its impact on the development of an explosive mixture in a bleeder-ventilated panel scheme. Simulation results indicate that the outgassing and ingassing across the gob and the formation of Explosive Gas Zones(EGZs) are directly affected by atmospheric pressure changes. In the location where methane zones interface with mine air, EGZ fringes may form along the face and in the bleeder entries. These findings help assess the methane ignition and explosion risks associated with fluctuating atmospheric pressures.
基金supported by the National Natural Science Foundation of China(No.51474216)
文摘In order to improve the utilization rate of foam,an arc jet nozzle was designed for precise dust control.Through theoretical analysis,the different demands of foam were compared amongst arc jets,flat jets and full cone jets when the dust source was covered identically by foam.It is proved that foam consumption was least when an arc jet was used.Foam production capability of an arc jet nozzle under different conditions was investigated through experiments.The results show that with the gas liquid ratio(GLR)increasing,the spray state of an arc jet nozzle presents successively water jet,foam jet and mist.Under a reasonable working condition range of foam production and a fixed GLR,foam production quantity increases at first,and then decreases with the increase of liquid supply quantity.When the inner diameter of the nozzle is 14 mm,the best GLR is 30 and the optimum liquid supply quantity is0.375 m^3/h.The results of field experiments show that the total dust and respirable dust suppression efficiency of arc jet nozzles is 85.8%and 82.6%respectively,which are 1.39 and 1.37 times higher than the full cone nozzles and 1.20 and 1.19 times higher than the fiat nozzles.
文摘In this paper, the authors will study the estimation of maintenance efficiency in Arithmetic Reduction of Intensity （ARI） and Arithmetic Reduction of Age （ARA） models with a memory m. These models have been proposed by Doyen （2005）, the failure process is simply Non Homogeneous Poisson Process （NHPP）. Our models are defined by reformulation of ARI and ARA ones using bathtub failure intensity. This form is presented like a superposition of two NHPP and Homogeneous Poisson Process （HPP）. Moreover, the particularity of this model allows taking account of system state improvement in time course. The maintenance effect is characterized by the change induced on the failure intensity before and after failure during degradation period. To simplify study, the asymptotic properties of failure process are derived. Then, the asymptotic normality of several maintenance efficiency estimators can be proved in the case where the failure process without maintenance is known. Practically, the coverage rate of the asymptotic confidence intervals issued from those estimators is studied.
基金Project(51178466) supported by the National Natural Science Foundation of ChinaProject(200545) supported by the Foundation for the Author of National Excellent Doctoral Dissertation of ChinaProject(2011JQ006) supported by the Fundamental Research Funds of the Central Universities of China
文摘To investigate airflow pattern and its impact on particle deposition, finite-volume based computational fluid dynamics （CFD） simulations were conducted in the diseased triple-bifitrcation airways. Computations were carried out for twenty Reynolds numbers ranging from 100 to 2 000 in the step of 100. Particles in the size range of 1-10 μm were conducted. Two particle deposition mechanisms （gravitational sedimentation and inertial impaction） were considered. The results indicate that there are strong relationship between airflow structures and particle deposition patterns. Deposition efficiency is different for different particles in the whole range of the respiratory rates. Particles in different sizes can deposit at different sites. Smaller particles can be uniformly deposited at the inside wall of the considered model. Larger particles can be mainly deposited in the proximal bifurcations. Deposition fraction varies a lot for different inlet Reynolds numbers. For lower Reynolds numbers, deposition fraction is relatively small and varies a little with varying the diameters. For Reynolds number to target the aerosols at the specific site. higher Reynolds numbers, there is a most efficient diameter for each
文摘Objective Bronchoscopy has been extensively used in the diagnosis of respiratory diseases, and par- ticularly, malignant diseases. However, endoscopists do not normally perform bronchoscopic biopsy in Case lesions are undetected via bronchoscopy. The aim of this study was to evaluate whether performing bron- choscopic biopsy could be established in the diagnosis of lung cancer in case of endobronchial abnormali- ties undetectable to the naked eye. Methods We retrospectively analyzed 109 cases between January 2008 and December 2012. The in- clusion criteria were confirmed lung cancer diagnosis, transbronchial biopsy performed in the absence of visible endobronchial manifestations, brushing, and bronchoalveolar lavage （BAL） according to the images obtained from high-resolution computed tomography （HRCT）. Data regarding age, sex, pathology, tumor stage; the method of diagnosis; location of primary lesion （central, peripheral, or intermediate）; tumor size, mediastinal lymph node metastasis, and the serum carcinoembryonic antigen （CEA） value were collected. The Pearson chi-square test or Fisher＇s exact and McNemar tests were used in the univadate analysis. Results Among the 109 patients, the diagnosis of 37 （33.9%） patients was confirmed through bronchos- copy. Brushing and BAL had higher positive detection rates than biopsy （P = 0.004）. There were no differ- ences in the positive detection rates between the sex, pathology, lesion location, tumor size, lymph node metastasis, and the serum CEA value （P〈 0.05 for all groups）. Conclusion Despite the normal appearance of the endobronchial manifestations, lesions undetectable by bronchoscopy could be indicated. Therefore, we suggest performing bronchoscopic biopsy and that brushing and BAL might increase the positive detection rate of bronchoscepic examination.
文摘This paper introduces a design to improve the radiotherapy accuracy of gamma knife. In this design, sensor is used to collect respiratory parameters and tumor displacement (caused by human respiration) model is established through optimization modeling. At the same time, data are transferred to single chip microcomputer (SCM) system by pressure sensor and then stepping motor is controlled by SCM. Finally, the intelligent positioning bed is under the control of stepping motor. As a result, the intelligent positioning bed can move reverse to respiratory law. The experimental results showed that this method can reduce the influence of respiration on tumor displacement, improving the accuracy of intelligent positioning bed with simple circuit and low cost at the same time.
基金Acknowledgments The authors gratefully acknowledge the financial support of the National Natural Science Foundation of China （51576021, 51222603, 51276208 and 51325602） and the National High-Tech R＆D Program of China （2015AA043503）.
文摘In this study, a membraneless, monolithic micro photocatalytic fuel cell with an air-breathing cathode was developed for simultaneous wastewater treatment and electricity generation. In this newly-developed micro photocatalytic fuel cell, the photoanode and cathode were arranged with a shoulder-to-shoulder design, forming two planar electrodes. Such design offers several advantages of enhanced mass transfer, uniform light distribution, short light transfer path, membrane elimination and easy fabrication, integration, and compatibility with other microdevices. The performance of this type fuel cell was evaluated by using methanol as a model pollutant under the alkaline condition. Experimental results indicated the developed micro photocatalytic fuel cell was able to show good photo-response to the illumination and satisfactory performance as well as durability. Parametric study on the cell performance was also performed. It was found that increasing the light intensity, methanol concentration andKOH concentration could improve the cell performance. But for the effect of the liquid flow rate, it was shown that the cell performance firstly increased with increasing the liquid flow rate and then decreased with further increasing the liquid flow rate. This study not only opens a new avenue for the design of the micro photocatalytic fuel cell but also is helpful for the optimization of the operating conditions.
