Air flow control is one of the most important control methods for maintaining the stability and reliability of a fuel cell system, which can avoid oxygen starvation or oxygen saturation. The oxygen excess ratio （OER...Air flow control is one of the most important control methods for maintaining the stability and reliability of a fuel cell system, which can avoid oxygen starvation or oxygen saturation. The oxygen excess ratio （OER） is often used to indicate the air flow condition. Based on a fuel cell system model for vehicles, OER performance was analyzed for different stack currents and temperatures in this paper, and the results show that the optimal OER was affected weakly by the stack temperature. In order to ensure the system working in optimal OER, a control scheme that includes an optimal OER regulator and a fuzzy control was proposed. According to the stack current, a reference value of air flow rate was obtained with the optimal OER regulator and then the air compressor motor voltage was controlled with the fuzzy controller to adjust the air flow rate provided by the air compressor. Simulation results show that the control method has good dynamic and static characteristics.展开更多
Bandgap engineering by doping and co‐catalyst loading are two primary approaches to designing efficient photocatalysts by promoting visible‐light absorption and charge separation,respectively.Shifting of the TiO2con...Bandgap engineering by doping and co‐catalyst loading are two primary approaches to designing efficient photocatalysts by promoting visible‐light absorption and charge separation,respectively.Shifting of the TiO2conduction band edge is frequently applied to increase visible‐light absorption but also lowers the reductive properties of photo‐excited electrons.Herein,we report a visible‐light‐driven photocatalyst based on valance band edge control induced by oxygen excess defects and modification with a CuxO electron transfer co‐catalyst.The CuxO grafted oxygen‐rich TiO2microspheres were prepared by ultrasonic spray pyrolysis of the peroxotitanate precursor followed by a wet chemical impregnated treatment.We found that oxygen excess defects in TiO2shifted the valence band maximum upward and improved the visible‐light absorption.The CuxO grafted onto the surface acted as a co‐catalyst that efficiently reduced oxygen molecules to active intermediates(i.e.,O2??radial and H2O2),thus consuming the photo‐generated electrons.Consequently,the CuxO grafted oxygen‐rich TiO2microspheres achieved a photocatalytic activity respectively8.6,13.0and11.0as times high as those of oxygen‐rich TiO2,normal TiO2and CuxO grafted TiO2,for degradation of gaseous acetaldehyde under visible‐light irradiation.Our results suggest that high visible‐light photocatalytic efficiency can be achieved by combining oxygen excess defects to improve visible‐light absorption together with a CuxO electron transfer co‐catalyst.These findings provide a new approach to developing efficient heterojunction photocatalysts.展开更多
Oxygen uptake(V O_(2))was measured during a non-exhaustive high-intensity intermittent cross-exercise(HIICE)protocol consisting of four alternating bouts of 20 s running(R)and three bouts of bicycle exercise(BE)at~160...Oxygen uptake(V O_(2))was measured during a non-exhaustive high-intensity intermittent cross-exercise(HIICE)protocol consisting of four alternating bouts of 20 s running(R)and three bouts of bicycle exercise(BE)at~160%and~170%maximal oxygen uptake(V O_(2)max),respectively,with 10 s between-bout rests(sequence R-BE-R-BER-BE-R).The V O_(2) during the last BE([52.2±5.0]mL⋅kg^(-1)⋅min^(-1))was significantly higher than the V O_(2)max of the BE([48.0±5.4]mL⋅kg^(-1)⋅min^(-1),n=30)and similar to that of running.For clarifying the underlying mechanisms,a corresponding HIICE-protocol with BE and arm cranking ergometer exercise(AC)was used(sequence AC-AC-BE-AC-BE-AC-AC-BE).In some experiments,thigh blood flow was occluded by a cuff around the upper thigh.Without occlusion,the V O_(2) during the AC([39.2±7.1]mL⋅kg^(-1)⋅min^(-1)[6th bout])was significantly higher than the V O_(2)max of AC([30.2±4.4]mL⋅kg^(-1)⋅min^(-1),n=7).With occlusion,the corresponding V O_(2)([29.8±3.9]mL⋅kg^(-1)⋅min^(-1))was reduced to that of the V O_(2)max of AC and significantly less than the V O_(2) without occlusion.These findings suggest that during the last bouts of HIICE may exceed the of the specific exercise,probably because it is a summation of the V O_(2) for the ongoing exercise plus excess post-oxygen consumption(EPOC)produced by the previous exercise with a higher V O_(2)max.展开更多
Objectives To study the relationship between alcohol and atherosclerosis （AS）. Methods The paper reviewed the mechanism of the alcohol leading to AS from four aspects such as the introduction of alcohol and AS, imba...Objectives To study the relationship between alcohol and atherosclerosis （AS）. Methods The paper reviewed the mechanism of the alcohol leading to AS from four aspects such as the introduction of alcohol and AS, imbalance of oxidationantioxidation system, oxygen free radical （OFR） and endothelium cell （EC） apoptosis, apoptosis and AS. Results Excessive alcohol could lead to imbalance of oxidation-antioxidation system, and increase OFR, in the meanwhile, OFR could lead to EC apoptosis, which could lead to AS.展开更多
Nanofibrous carbonaceous materials （NFC） as a new class of materials having many applications, can catalyze the selective oxidation of H2S to sulfur. The correlation between NFC structure and its activity and select...Nanofibrous carbonaceous materials （NFC） as a new class of materials having many applications, can catalyze the selective oxidation of H2S to sulfur. The correlation between NFC structure and its activity and selectivity in H2S oxidation was determined. It is demonstrated that selectivity can be improved if NFC with more ordered structure be synthesized and the portion of the original catalyst in carbon be reduced by increasing the carbon accumulated in the catalyst.展开更多
This paper develops an adaptive neural network(NN)observer for proton-exchange membrane fuel cells(PEMFCs).Indeed,information on the oxygen excess ratio(OER)value is crucial to ensure optimal management of the durabil...This paper develops an adaptive neural network(NN)observer for proton-exchange membrane fuel cells(PEMFCs).Indeed,information on the oxygen excess ratio(OER)value is crucial to ensure optimal management of the durability and reliability of the PEMFC.The OER indicator is computed from the mass of oxygen and nitrogen inside the PEMFC cathode.Unfortunately,the measurement process of both these masses is difficult and costly.To solve this problem,the design of a PEMFC state observer is attractive.However,the behaviour of the fuel cell system is highly non-linear and its modelling is complex.Due to this constraint,a multilayer perceptron neural network(MLPNN)-based observer is proposed in this paper to estimate the oxygen and nitrogen masses.One notable advantage of the suggested MLPNN observer is that it does not require a database to train the NN.Indeed,the weights of the NN are updated in real time using the output error.In addition,the observer parameters,namely the learning rate and the damping factor,are online adapted using the optimization tools of extremum seeking.Moreover,the proposed observer stability analysis is performed using the Lyapunov theory.The observer performances are validated by simulation under MATLAB®/Simulink®.The supremacy of the proposed adaptive MLPNN observer is highlighted by comparison with a fixed-parameter MLPNN observer and a classical high-gain observer(HGO).The mean rela-tive error value of the excess oxygen rate is considered the performance index,which is equal to 1.01%for an adaptive MLPNN and 3.95%and 9.95%for a fixed MLPNN and HGO,respectively.Finally,a robustness test of the proposed observer with respect to measurement noise is performed.展开更多
基金supported by the National Natural Science Foundation of China (No. 51177138)the Research Fund for the Doctoral Program of High Education of China (No.20100184110015)Sichuan Province International Technology Cooperation and Exchange Program (No. 2012HH0007)
文摘Air flow control is one of the most important control methods for maintaining the stability and reliability of a fuel cell system, which can avoid oxygen starvation or oxygen saturation. The oxygen excess ratio （OER） is often used to indicate the air flow condition. Based on a fuel cell system model for vehicles, OER performance was analyzed for different stack currents and temperatures in this paper, and the results show that the optimal OER was affected weakly by the stack temperature. In order to ensure the system working in optimal OER, a control scheme that includes an optimal OER regulator and a fuzzy control was proposed. According to the stack current, a reference value of air flow rate was obtained with the optimal OER regulator and then the air compressor motor voltage was controlled with the fuzzy controller to adjust the air flow rate provided by the air compressor. Simulation results show that the control method has good dynamic and static characteristics.
基金supported by the National Natural Science Foundation of China(51072032,51372036,51702235)~~
文摘Bandgap engineering by doping and co‐catalyst loading are two primary approaches to designing efficient photocatalysts by promoting visible‐light absorption and charge separation,respectively.Shifting of the TiO2conduction band edge is frequently applied to increase visible‐light absorption but also lowers the reductive properties of photo‐excited electrons.Herein,we report a visible‐light‐driven photocatalyst based on valance band edge control induced by oxygen excess defects and modification with a CuxO electron transfer co‐catalyst.The CuxO grafted oxygen‐rich TiO2microspheres were prepared by ultrasonic spray pyrolysis of the peroxotitanate precursor followed by a wet chemical impregnated treatment.We found that oxygen excess defects in TiO2shifted the valence band maximum upward and improved the visible‐light absorption.The CuxO grafted onto the surface acted as a co‐catalyst that efficiently reduced oxygen molecules to active intermediates(i.e.,O2??radial and H2O2),thus consuming the photo‐generated electrons.Consequently,the CuxO grafted oxygen‐rich TiO2microspheres achieved a photocatalytic activity respectively8.6,13.0and11.0as times high as those of oxygen‐rich TiO2,normal TiO2and CuxO grafted TiO2,for degradation of gaseous acetaldehyde under visible‐light irradiation.Our results suggest that high visible‐light photocatalytic efficiency can be achieved by combining oxygen excess defects to improve visible‐light absorption together with a CuxO electron transfer co‐catalyst.These findings provide a new approach to developing efficient heterojunction photocatalysts.
基金supported in part by a KAKENHI Grant-in-Aid for Challenging Exploratory Research 26560406 from the Japan Society for the Promotion of Sciences.
文摘Oxygen uptake(V O_(2))was measured during a non-exhaustive high-intensity intermittent cross-exercise(HIICE)protocol consisting of four alternating bouts of 20 s running(R)and three bouts of bicycle exercise(BE)at~160%and~170%maximal oxygen uptake(V O_(2)max),respectively,with 10 s between-bout rests(sequence R-BE-R-BER-BE-R).The V O_(2) during the last BE([52.2±5.0]mL⋅kg^(-1)⋅min^(-1))was significantly higher than the V O_(2)max of the BE([48.0±5.4]mL⋅kg^(-1)⋅min^(-1),n=30)and similar to that of running.For clarifying the underlying mechanisms,a corresponding HIICE-protocol with BE and arm cranking ergometer exercise(AC)was used(sequence AC-AC-BE-AC-BE-AC-AC-BE).In some experiments,thigh blood flow was occluded by a cuff around the upper thigh.Without occlusion,the V O_(2) during the AC([39.2±7.1]mL⋅kg^(-1)⋅min^(-1)[6th bout])was significantly higher than the V O_(2)max of AC([30.2±4.4]mL⋅kg^(-1)⋅min^(-1),n=7).With occlusion,the corresponding V O_(2)([29.8±3.9]mL⋅kg^(-1)⋅min^(-1))was reduced to that of the V O_(2)max of AC and significantly less than the V O_(2) without occlusion.These findings suggest that during the last bouts of HIICE may exceed the of the specific exercise,probably because it is a summation of the V O_(2) for the ongoing exercise plus excess post-oxygen consumption(EPOC)produced by the previous exercise with a higher V O_(2)max.
文摘Objectives To study the relationship between alcohol and atherosclerosis （AS）. Methods The paper reviewed the mechanism of the alcohol leading to AS from four aspects such as the introduction of alcohol and AS, imbalance of oxidationantioxidation system, oxygen free radical （OFR） and endothelium cell （EC） apoptosis, apoptosis and AS. Results Excessive alcohol could lead to imbalance of oxidation-antioxidation system, and increase OFR, in the meanwhile, OFR could lead to EC apoptosis, which could lead to AS.
文摘Nanofibrous carbonaceous materials （NFC） as a new class of materials having many applications, can catalyze the selective oxidation of H2S to sulfur. The correlation between NFC structure and its activity and selectivity in H2S oxidation was determined. It is demonstrated that selectivity can be improved if NFC with more ordered structure be synthesized and the portion of the original catalyst in carbon be reduced by increasing the carbon accumulated in the catalyst.
基金supported by the Ministry of Higher Education,Scientific Research and Innovation,the Digital Development Agency and the CNRST of Morocco(Alkhawarizmi/2020/39).
文摘This paper develops an adaptive neural network(NN)observer for proton-exchange membrane fuel cells(PEMFCs).Indeed,information on the oxygen excess ratio(OER)value is crucial to ensure optimal management of the durability and reliability of the PEMFC.The OER indicator is computed from the mass of oxygen and nitrogen inside the PEMFC cathode.Unfortunately,the measurement process of both these masses is difficult and costly.To solve this problem,the design of a PEMFC state observer is attractive.However,the behaviour of the fuel cell system is highly non-linear and its modelling is complex.Due to this constraint,a multilayer perceptron neural network(MLPNN)-based observer is proposed in this paper to estimate the oxygen and nitrogen masses.One notable advantage of the suggested MLPNN observer is that it does not require a database to train the NN.Indeed,the weights of the NN are updated in real time using the output error.In addition,the observer parameters,namely the learning rate and the damping factor,are online adapted using the optimization tools of extremum seeking.Moreover,the proposed observer stability analysis is performed using the Lyapunov theory.The observer performances are validated by simulation under MATLAB®/Simulink®.The supremacy of the proposed adaptive MLPNN observer is highlighted by comparison with a fixed-parameter MLPNN observer and a classical high-gain observer(HGO).The mean rela-tive error value of the excess oxygen rate is considered the performance index,which is equal to 1.01%for an adaptive MLPNN and 3.95%and 9.95%for a fixed MLPNN and HGO,respectively.Finally,a robustness test of the proposed observer with respect to measurement noise is performed.
