Water management is of great importance to maintain performance and durability of proton exchange membrane fuel cells. This paper presents a novel proton exchange membrane (PEM) fuel cell with a humidification zone in...Water management is of great importance to maintain performance and durability of proton exchange membrane fuel cells. This paper presents a novel proton exchange membrane (PEM) fuel cell with a humidification zone in the membrane electrode assembly (MEA) of each cell, in which the moisture of the cathode exhaust gas could transfer through the membrane to humidify anode or cathode dry gas. With a simple model, the relative humidity (RH) of the dry air exhaust from a membrane humidifier with 100% RH stream as a counter flow is calculated to be 60.0%, which is very close to the experimental result (62.2%). Fuel cell performances with hydrogen humidifying, air humidifying and no humidifying are compared at 50, 60 and 70°C and the results indicate that humidifying is necessary and the novel design with humidifying zone in MEA is effective to humidify dry reactants. The hydrogen humidifying shows better performance in short term, while water recovered is limited and the stability is not as good as air humidifying. It is recommended that both air and hydrogen should be humidified with proper design of the humidifying zones in MEA and plates.展开更多
As one of the important parts of urban ecosystem, urban green space plays an irreplaceable role in maintaining the balance of carbon and oxygen, absorbing the pollution and removing dust, killing bacteria, purifying s...As one of the important parts of urban ecosystem, urban green space plays an irreplaceable role in maintaining the balance of carbon and oxygen, absorbing the pollution and removing dust, killing bacteria, purifying soil and water. To analyze the spatio-temporal changes of humidifying effect of green lands at the spring daytime, the authors monitored the air humidity within 1.8 m high from various underlying surfaces, including arbor-grass lands, shrub lands, herb lands and a cement pavement, from late February to late April in 2015 and 2016, when it was sunny and windless, in the Yuxi park of Shijiazhuang. The results were compared with the monitoring data of a bare land(190 m×120 m) without environmental interventions such as vegetation and water. The results could be summarized as follows:(1) The humidifying effect of green spaces was the weakest at 8:00 a.m. during the late February, whereas it was the strongest at 10:00 a.m.; from late March to late April, the humidifying effect of green spaces strengthened with the increase of air temperature, and the strongest was noted around 12:00-16:00.(2) The humidifying effect of various types of green lands was the strongest close to the ground, and reduced from 0.2 m to 1.8 m. This vertical stratification became apparent after the plants sprouted, the vertical difference of humidifying effect was the most significant in the herb lands, less significant in arbor-grass lands, and least in the shrub lands.(3) Multiple comparison analysis of the humidity data showed that relative humidity of all green lands achieved the significant level(P < 0.05), indicating the strong effect of landscape plants in adjusting atmospheric humidity in spring.(4) The humidifying effect of the artificial lake was more remarkable before the plants sprouted, however, with the rapid growth of plant leaves, theeffect gradually reduced and became even weaker than the effect of vegetation. Although the humidifying effect in spring was weaker than that in summer and autumn, the effect of humidification was more complicated during the growth of green leaves in spring than in summer and autumn. This is useful to construct the theory system of ecological environment effect of green lands in spring, summer and autumn.展开更多
As an important part of urban green space system, wetland parks have good ecological environment and various landscape resources, which play an irreplaceable role in adjusting the climate, beautifying the environment ...As an important part of urban green space system, wetland parks have good ecological environment and various landscape resources, which play an irreplaceable role in adjusting the climate, beautifying the environment and maintaining regional ecological balance. Therefore, research on humidifying effect of wetland park is of great significance. Air humidity below the height of 1.5 m above various underlying surfaces was measured in Taiping Riparian Wetland Park of Shijiazhuang. Monitoring time was selected in October 10–12, 2012 and six days among September and October, 2013 which were sunny days without wind(or the speed of wind less than 0.2 m/s). By analyzing the basic distribution regularity of humidity from horizontal and vertical directions at different times in autumn days, humidifying effect of various types of plants could be summarized from the sampled data. The humidifying effect of arbor-grasses can strengthen with the increase of temperature. The humidifying effect is the strongest at 10:00–14:00, then, it weakens after noon and the reduction rate tends to be smaller. Second, the humidity above the height of 0.2 m changes at a small scale and is much lower than that close to ground, which reveals great effect of ground cover plants and soil moisture. According to the monitoring data below the height of 1.5 m, the humidifying effect of shrubs is stronger than that of arbor-grasses. Last, the humidifying effect of surfaces with different land covers from strong to weak are shrubs, arbor-grasses, river. The rational allocation on various types of wetlands with a wide variety of structures can improve the atmospheric environment more effectively.展开更多
This paper presents an experimental testing and validation results for a zero-dimensional self-humidifying PEM (Proton Exchange Membrane) fuel cell stack. The model incorporates major electric and thermodynamic variab...This paper presents an experimental testing and validation results for a zero-dimensional self-humidifying PEM (Proton Exchange Membrane) fuel cell stack. The model incorporates major electric and thermodynamic variables and parameters involved in the operation of the PEM fuel cell under different operational conditions. The mathematical equations are modelled by using Matlab-Simulink tools in order to simulate the operation of the developed model with a commercially available 1 kW Horizon (H-1000) PEM fuel cell stack, which is used for the purposes of model validation and tuning of the developed model. The model is mathematically modelled and presented in the recent published work of authors. The observations from model simulations provide sufficient evidence and support to the results and observations obtained from testing 1 kW Horizon (H-1000) PEM fuel cell stack used in this research. The developed model can be used as a generic model and simulation platform for a self-humidifying PEM fuel cell with an output power varying from 50 W to 1 kW, with extrapolation to higher powers is also possible.展开更多
目的通过胃窦超声检查比较不同流速经鼻湿化快速通气(THRIVE)以及压力控制面罩通气(PCFV)对老年患者全麻手术诱导期间胃进气的影响。方法选择择期行全麻手术患者99例,男45例,女54例,年龄65~80岁,BMI 18.5~30.0 kg/m^(2),ASAⅠ—Ⅲ级。...目的通过胃窦超声检查比较不同流速经鼻湿化快速通气(THRIVE)以及压力控制面罩通气(PCFV)对老年患者全麻手术诱导期间胃进气的影响。方法选择择期行全麻手术患者99例,男45例,女54例,年龄65~80岁,BMI 18.5~30.0 kg/m^(2),ASAⅠ—Ⅲ级。将患者随机分为四组:THRIVE 30 L/min组(T30组,n=24)、THRIVE 50 L/min组(T50组,n=25)、THRIVE 70 L/min组(T70组,n=25)和面罩5 L/min压力控制通气组(F组,n=25)。四组患者麻醉诱导对刺激无反应后分别接受THRIVE 30、50、70 L/min和PCFV 5 L/min,FiO_(2)100%给氧。于麻醉诱导前、诱导后即刻、诱导后1、2和3 min时采用超声监测仰卧位胃进气阳性(GI^(+))情况。记录麻醉诱导前、诱导后即刻、诱导后1、2和3 min时胃窦横截面积(CSA)、PaO_(2)和PaCO_(2)。记录术后恶心呕吐等不良事件的发生情况。结果与F组比较,诱导后3 min T30、T50组GI^(+)发生率、CSA明显降低(P<0.05),T70组CSA明显降低(P<0.05),诱导后1、2、3 min T30组和T50组PaO_(2)明显降低,PaCO_(2)明显升高(P<0.05),诱导后3 min T70组PaO_(2)明显降低,PaCO_(2)明显升高(P<0.05)。与T70组比较,诱导后3 min T30组GI^(+)发生率、CSA明显降低(P<0.05),T50组CSA明显降低(P<0.05),诱导后1、2、3 min T30组PaO_(2)明显降低、PaCO_(2)明显升高(P<0.05),诱导后1、3 min T50组PaO_(2)明显降低(P<0.05)。与T50组比较,诱导后2、3 min T30组PaO_(2)明显降低,诱导后1、2、3 min PaCO_(2)明显升高(P<0.05)。四组术后恶心呕吐发生率差异无统计学意义。结论与传统PCFV比较,THRIVE技术用于麻醉诱导通气可降低胃进气的发生率,相较于THRIVE 30和70 L/min,THRIVE 50 L/min在提供较好的氧合同时,胃进气的发生率最低。展开更多
Ultrasonic humidifiers are commonly used in households to maintain indoor humidity and generate a large number of droplets or spray aerosols.However,there have been various health concerns associated with humidifier u...Ultrasonic humidifiers are commonly used in households to maintain indoor humidity and generate a large number of droplets or spray aerosols.However,there have been various health concerns associated with humidifier use,largely due to aerosols generated during operation.Here,we investigated the size distribution,chemical composition,and charged fraction of aerosol particles emitted from commercial ultrasonic humidifiers.Heavy metals in water used for humidifiers were found to be highly enriched in the ultrasonic humidifier aerosols(UHA),with the enrichment factors ranging from 102 to 107.This enrichment may pose health concerns for the building occupants,as UHA concentrations of up to 106 particles/cm^(3) or 3 mg/m^(3) were observed.Furthermore,approximately 90%of UHA were observed to be electrically charged,for the first time according to our knowledge.Based on this discovery,we proposed and tested a newmethod to remove UHA by using a simple electrical field.The designed electrical field in this work can efficiently remove 81.4%of UHA.Therefore,applying this electrical field could be an effective method to significantly reduce the health risks by UHA.展开更多
基金Supported by the National High Technology Research and Development Program of China (2008AA05Z104)
文摘Water management is of great importance to maintain performance and durability of proton exchange membrane fuel cells. This paper presents a novel proton exchange membrane (PEM) fuel cell with a humidification zone in the membrane electrode assembly (MEA) of each cell, in which the moisture of the cathode exhaust gas could transfer through the membrane to humidify anode or cathode dry gas. With a simple model, the relative humidity (RH) of the dry air exhaust from a membrane humidifier with 100% RH stream as a counter flow is calculated to be 60.0%, which is very close to the experimental result (62.2%). Fuel cell performances with hydrogen humidifying, air humidifying and no humidifying are compared at 50, 60 and 70°C and the results indicate that humidifying is necessary and the novel design with humidifying zone in MEA is effective to humidify dry reactants. The hydrogen humidifying shows better performance in short term, while water recovered is limited and the stability is not as good as air humidifying. It is recommended that both air and hydrogen should be humidified with proper design of the humidifying zones in MEA and plates.
基金Supported by the National Science and Technology Major Project(2011ZX05043-005)
文摘As one of the important parts of urban ecosystem, urban green space plays an irreplaceable role in maintaining the balance of carbon and oxygen, absorbing the pollution and removing dust, killing bacteria, purifying soil and water. To analyze the spatio-temporal changes of humidifying effect of green lands at the spring daytime, the authors monitored the air humidity within 1.8 m high from various underlying surfaces, including arbor-grass lands, shrub lands, herb lands and a cement pavement, from late February to late April in 2015 and 2016, when it was sunny and windless, in the Yuxi park of Shijiazhuang. The results were compared with the monitoring data of a bare land(190 m×120 m) without environmental interventions such as vegetation and water. The results could be summarized as follows:(1) The humidifying effect of green spaces was the weakest at 8:00 a.m. during the late February, whereas it was the strongest at 10:00 a.m.; from late March to late April, the humidifying effect of green spaces strengthened with the increase of air temperature, and the strongest was noted around 12:00-16:00.(2) The humidifying effect of various types of green lands was the strongest close to the ground, and reduced from 0.2 m to 1.8 m. This vertical stratification became apparent after the plants sprouted, the vertical difference of humidifying effect was the most significant in the herb lands, less significant in arbor-grass lands, and least in the shrub lands.(3) Multiple comparison analysis of the humidity data showed that relative humidity of all green lands achieved the significant level(P < 0.05), indicating the strong effect of landscape plants in adjusting atmospheric humidity in spring.(4) The humidifying effect of the artificial lake was more remarkable before the plants sprouted, however, with the rapid growth of plant leaves, theeffect gradually reduced and became even weaker than the effect of vegetation. Although the humidifying effect in spring was weaker than that in summer and autumn, the effect of humidification was more complicated during the growth of green leaves in spring than in summer and autumn. This is useful to construct the theory system of ecological environment effect of green lands in spring, summer and autumn.
基金supported by the National Science and Technology Major Project of the Ministry of Science and Technology of China(2011ZX05043-005)
文摘As an important part of urban green space system, wetland parks have good ecological environment and various landscape resources, which play an irreplaceable role in adjusting the climate, beautifying the environment and maintaining regional ecological balance. Therefore, research on humidifying effect of wetland park is of great significance. Air humidity below the height of 1.5 m above various underlying surfaces was measured in Taiping Riparian Wetland Park of Shijiazhuang. Monitoring time was selected in October 10–12, 2012 and six days among September and October, 2013 which were sunny days without wind(or the speed of wind less than 0.2 m/s). By analyzing the basic distribution regularity of humidity from horizontal and vertical directions at different times in autumn days, humidifying effect of various types of plants could be summarized from the sampled data. The humidifying effect of arbor-grasses can strengthen with the increase of temperature. The humidifying effect is the strongest at 10:00–14:00, then, it weakens after noon and the reduction rate tends to be smaller. Second, the humidity above the height of 0.2 m changes at a small scale and is much lower than that close to ground, which reveals great effect of ground cover plants and soil moisture. According to the monitoring data below the height of 1.5 m, the humidifying effect of shrubs is stronger than that of arbor-grasses. Last, the humidifying effect of surfaces with different land covers from strong to weak are shrubs, arbor-grasses, river. The rational allocation on various types of wetlands with a wide variety of structures can improve the atmospheric environment more effectively.
文摘This paper presents an experimental testing and validation results for a zero-dimensional self-humidifying PEM (Proton Exchange Membrane) fuel cell stack. The model incorporates major electric and thermodynamic variables and parameters involved in the operation of the PEM fuel cell under different operational conditions. The mathematical equations are modelled by using Matlab-Simulink tools in order to simulate the operation of the developed model with a commercially available 1 kW Horizon (H-1000) PEM fuel cell stack, which is used for the purposes of model validation and tuning of the developed model. The model is mathematically modelled and presented in the recent published work of authors. The observations from model simulations provide sufficient evidence and support to the results and observations obtained from testing 1 kW Horizon (H-1000) PEM fuel cell stack used in this research. The developed model can be used as a generic model and simulation platform for a self-humidifying PEM fuel cell with an output power varying from 50 W to 1 kW, with extrapolation to higher powers is also possible.
文摘目的通过胃窦超声检查比较不同流速经鼻湿化快速通气(THRIVE)以及压力控制面罩通气(PCFV)对老年患者全麻手术诱导期间胃进气的影响。方法选择择期行全麻手术患者99例,男45例,女54例,年龄65~80岁,BMI 18.5~30.0 kg/m^(2),ASAⅠ—Ⅲ级。将患者随机分为四组:THRIVE 30 L/min组(T30组,n=24)、THRIVE 50 L/min组(T50组,n=25)、THRIVE 70 L/min组(T70组,n=25)和面罩5 L/min压力控制通气组(F组,n=25)。四组患者麻醉诱导对刺激无反应后分别接受THRIVE 30、50、70 L/min和PCFV 5 L/min,FiO_(2)100%给氧。于麻醉诱导前、诱导后即刻、诱导后1、2和3 min时采用超声监测仰卧位胃进气阳性(GI^(+))情况。记录麻醉诱导前、诱导后即刻、诱导后1、2和3 min时胃窦横截面积(CSA)、PaO_(2)和PaCO_(2)。记录术后恶心呕吐等不良事件的发生情况。结果与F组比较,诱导后3 min T30、T50组GI^(+)发生率、CSA明显降低(P<0.05),T70组CSA明显降低(P<0.05),诱导后1、2、3 min T30组和T50组PaO_(2)明显降低,PaCO_(2)明显升高(P<0.05),诱导后3 min T70组PaO_(2)明显降低,PaCO_(2)明显升高(P<0.05)。与T70组比较,诱导后3 min T30组GI^(+)发生率、CSA明显降低(P<0.05),T50组CSA明显降低(P<0.05),诱导后1、2、3 min T30组PaO_(2)明显降低、PaCO_(2)明显升高(P<0.05),诱导后1、3 min T50组PaO_(2)明显降低(P<0.05)。与T50组比较,诱导后2、3 min T30组PaO_(2)明显降低,诱导后1、2、3 min PaCO_(2)明显升高(P<0.05)。四组术后恶心呕吐发生率差异无统计学意义。结论与传统PCFV比较,THRIVE技术用于麻醉诱导通气可降低胃进气的发生率,相较于THRIVE 30和70 L/min,THRIVE 50 L/min在提供较好的氧合同时,胃进气的发生率最低。
基金supported by the National Natural Science Foundation of China (Nos.42077193 and 21976034)the National Key R&D Program (Nos.2022YFC3702600 and 2022YFC3702601)the Shanghai Natural Science Foundation (23ZR1479700).
文摘Ultrasonic humidifiers are commonly used in households to maintain indoor humidity and generate a large number of droplets or spray aerosols.However,there have been various health concerns associated with humidifier use,largely due to aerosols generated during operation.Here,we investigated the size distribution,chemical composition,and charged fraction of aerosol particles emitted from commercial ultrasonic humidifiers.Heavy metals in water used for humidifiers were found to be highly enriched in the ultrasonic humidifier aerosols(UHA),with the enrichment factors ranging from 102 to 107.This enrichment may pose health concerns for the building occupants,as UHA concentrations of up to 106 particles/cm^(3) or 3 mg/m^(3) were observed.Furthermore,approximately 90%of UHA were observed to be electrically charged,for the first time according to our knowledge.Based on this discovery,we proposed and tested a newmethod to remove UHA by using a simple electrical field.The designed electrical field in this work can efficiently remove 81.4%of UHA.Therefore,applying this electrical field could be an effective method to significantly reduce the health risks by UHA.
