Background: The Air Force Health Study collected reproductive outcomes for live-born children of male Air Force veterans of the Vietnam War. Methods: Dioxin values for participants were obtained from blood samples. An...Background: The Air Force Health Study collected reproductive outcomes for live-born children of male Air Force veterans of the Vietnam War. Methods: Dioxin values for participants were obtained from blood samples. Analyses were conducted of occurrence of 16 specific categories of birth defects and developmental disabilities. Children were categorized as conceived before and after the start of participants’ Vietnam War service. Children conceived before the start of Vietnam War service were treated as being conceived when their fathers had unquantifiable dioxin values. Children conceived after the start of Vietnam War service for participants with missing dioxin values were excluded from primary analyses, but were used to assess the impact of their exclusion on conclusions. Correlation between values for specific categories for multiple children fathered by the same participant was accounted for. The dose-response relationship was treated as a step function increasing for dioxin values larger than adaptively identified individual thresholds changing with the specific category. Results: For 15 of 16 specific categories, the probability of occurrence increased substantially for a sufficiently high dioxin level above identified thresholds. Exclusion of children due to missing dioxin likely did not affect these results. Conclusions: Results supported the conclusion of substantial adverse effects on a wide variety of specific categories of birth defects and developmental disabilities due to sufficiently high exposures to dioxin, a toxic contaminant of Agent Orange used for herbicide spraying in the Vietnam War. Results may hold more generally, but might also have been affected by a variety of limitations.展开更多
Surface roughness plays a significant role in floatability of coal.In the present paper,coking coal surface was polished by three different sandpapers and the surface properties were characterized by contact angle and...Surface roughness plays a significant role in floatability of coal.In the present paper,coking coal surface was polished by three different sandpapers and the surface properties were characterized by contact angle and roughness measurements.The effect of surface roughness on floatability was investigated by adhesion force measurement system for measuring interaction forces between droplets/bubbles and coking coal surfaces with different roughness.The results showed that the contact angle decreased with increasing roughness yet the adhesion force between the water droplet and coal surface increased owing to the increased contact line and the appearance of line pinning.Maximum adhesion forces between water and surfaces were 111.70,125.48,and 136.42μN when the roughness was 0.23,0.98,and 2.79 μm,respectively.In contrast,under a liquid environment,the adhesion forces between air bubble/oil droplet and coal surfaces were decreased with increasing roughness because of the restriction by water.Maximum adhesion forces of increasing roughness were 97.14,42.76,and 17.86 μN measured at interfaces between air bubble and coal surfaces and 169.48,145.84,and 121.02 lN between oil droplet and surfaces,respectively.Decreasing roughness could be beneficial to the spreading of oil droplets and the adhesion of bubbles which is conducive to flotation separation.展开更多
The effective radiative forcing (ERF) and associated surface air temperature change over eastern China are estimated using multi-model results from CMIP5 (Coupled Model Intercomparison Project Phase 5). The model ...The effective radiative forcing (ERF) and associated surface air temperature change over eastern China are estimated using multi-model results from CMIP5 (Coupled Model Intercomparison Project Phase 5). The model results show that, relative to 1850, the multi-model and annual mean aerosol ERF for the year 2005 is -4.14 W m^-2 at the top of the atmosphere over eastern China (20°-45°N, 105°-122.5°E). As a result of this ERF, the multi-model and annual mean surface air temperature change in eastern China during 1850-2005 is -1.05℃, leading to a climate sensitivity of 0.24℃/ (Wm^-2) in this region.展开更多
This paper presents a coupled magnetic-circuit method for computing the magnetic force of air-core reactor under short-time current. The current and the magnetic flux density are computed first and then the magnetic f...This paper presents a coupled magnetic-circuit method for computing the magnetic force of air-core reactor under short-time current. The current and the magnetic flux density are computed first and then the magnetic force is obtained. Thus, the dynamic stability performance of air-core reactor can be analyzed at the design stage to reduce experimental cost and shorten the lead-time of product development.展开更多
NIKE AIR FORCE 1是NIKE各种鞋类中拥有最大专营模式的系列。从纽约到北京,AIR FORCE 1都是在街头巷尾最热门的鞋款。AIR FORCE 1是以篮球鞋来体现街头HIP HOP精神的典范。在这25年中,有超过1700双不同版本的AIR FORCE 1被制造出来....NIKE AIR FORCE 1是NIKE各种鞋类中拥有最大专营模式的系列。从纽约到北京,AIR FORCE 1都是在街头巷尾最热门的鞋款。AIR FORCE 1是以篮球鞋来体现街头HIP HOP精神的典范。在这25年中,有超过1700双不同版本的AIR FORCE 1被制造出来.而AF1的大型庆祝活动将贯穿2007年的春夏秋冬。就在2007年逐步走到年底的时候.NIKE再次重拳出击。推出了SERATO AIR FORCE 1PACK。展开更多
The 300 MW steam turbine installed in Waigaoqiao Power Plant with combined HPIP cylinders of double casing structure is a product of the Shanghai Turbine Works utilizing licensed technology. It has a large heat storag...The 300 MW steam turbine installed in Waigaoqiao Power Plant with combined HPIP cylinders of double casing structure is a product of the Shanghai Turbine Works utilizing licensed technology. It has a large heat storage capacity and good thermal insulation, so the metal temperature of first stage of HP cylinder (FSMTI) may reach 400-450℃ after shut down and it takes 7-8 days to cool to 150℃ by natural cooling, Now with a forced cooling system the cooling time may be reduced to 40 hours, so that the turbine may be opened for repair work in about 5-6 days. The cooling system for #2 unit and test procedure are briefly described below.展开更多
Heating-only fan coil(HFC)is one of the suited end users,which is not only compact but also highly efficient.And the major factors affecting the heat dissipation performance of HFC include leakage through coil bypass,...Heating-only fan coil(HFC)is one of the suited end users,which is not only compact but also highly efficient.And the major factors affecting the heat dissipation performance of HFC include leakage through coil bypass,distance between fan and coil,fan structure and air inlet type.Under natural air convection or forced,experimental studies were made on the effects of these factors upon the heat dissipation performance of HFC.The results show that:1)After reducing the leakage through coil bypass,the heat dissipation of HFC increases 16.9% under natural convection,and increases 8.3% under forced convection.2)After the distance between fan and coil be raised from 23.2cm to 41.7cm,the heat dissipation of HFC decreases 21.3% under natural convection,but increases12.8% under forced convection.3)After changing the fan structure,the heat dissipation of HFC increases 41.8% under natural convection,and the heat dissipation per motor power increases 96.1% under forced convection.4)The heat dissipations of HFC with round pass,slit and strip type of air inlet are different,whose proportion is about 100%,110%,136% under natural convection,and 100%,105%,116% under forced convection.展开更多
A case study was performed in Beijing in 2000 to observe concentrations of SO2 and NOx in the atmosphere and to evaluate their radiative impact. It was found that the concentrations of these gases are usually high in ...A case study was performed in Beijing in 2000 to observe concentrations of SO2 and NOx in the atmosphere and to evaluate their radiative impact. It was found that the concentrations of these gases are usually high in the morning due to a temperature inversion in the boundary layer. The average concentrations obtained from the observations are much higher than those used in the McClatchey reference atmosphere. The radiative impacts of these gases are calculated using a line-by-line radiative transfer model. The results show that the radiative forcing at the surface due to SO2 is 0.0576 W m^-2 and that due to NOx is 0.0032 W m^-2. These figures are almost compatible with that due to CFC11.展开更多
A separation method is proposed to design and improve shock absorber according to the characteristics of each force. The method is validated by rig test. The force data measured during rig test is the resultant force ...A separation method is proposed to design and improve shock absorber according to the characteristics of each force. The method is validated by rig test. The force data measured during rig test is the resultant force of damping force, rebound force produced by pressed air, and friction force. Different characters of damping force, air rebound force and friction force can be applied to seperate each force from others. A massive produced air filling shock absorber is adopted for the validation. The statistic test is used to get the displacement-force curves. The data are used as the input of separation calculation. Then the tests are carried out again to obtain the force data without air rebound force. The force without air rebound is compared to the data derived from the former tests with the separation method. The result shows that this method can separate the damping force and the air elastic force.展开更多
Due to the high viscosity of magnetorheological(MR)fluid,eliminating air pockets dissolved in the fluid is very difficult,which results in a force lag phenomenon.In order to evaluate the performance of a semi-active c...Due to the high viscosity of magnetorheological(MR)fluid,eliminating air pockets dissolved in the fluid is very difficult,which results in a force lag phenomenon.In order to evaluate the performance of a semi-active control system based on the MR damper considering the trapped air effect,a performance test on a MR damper is carried out under different loading cases,and the influence of the input current,excitation amplitude and frequency on the force lag phenomenon is analyzed.A concise and efficient parametric model,combining the simple Bouc-Wen model and a spring with small stiffness,is proposed to portray the experimental characteristics of the MR damper with force lag,and then the response analysis of the semi-active controlled single-degree-of-freedom(SDOF)structure is performed using the classic clipped-optimal control strategy based on acceleration feedback.Numerical results show that the trapped air in the MR fluid can weaken the control effect of the MR damper,and the performance of the semi-active control system will be reduced more obviously and become close to the passive-off control with the increasing content of air trapped in the MR fluid.展开更多
This paper studies the CoNbZr soft magnetic thin film by magnetic force microscopy (MFM). By measuring in atmosphere circumstance, the magnetic force images display some clear dark dots which are corresponding to th...This paper studies the CoNbZr soft magnetic thin film by magnetic force microscopy (MFM). By measuring in atmosphere circumstance, the magnetic force images display some clear dark dots which are corresponding to the clusters in the topography images welL Then the dark dots disappear in magnetic force images, scanning in high vacuum. This indicates that the dark dots are caused by air damping between the vibrating tip and the sample. An interpretation for the above observation is given.展开更多
<b>Background:</span></b><span style="font-family:""><span style="font-family:Verdana;"> Tidal expiratory flow limitation (tEFL) is defined as absence of increase...<b>Background:</span></b><span style="font-family:""><span style="font-family:Verdana;"> Tidal expiratory flow limitation (tEFL) is defined as absence of increase in air flow during forced expiration compared to tidal breathing and is related to dyspnea at rest and minimal exertion in patients with chronic airflow limitation (CAL). Tidal EFL has not been expressed as a continuous variable (0% - 100%) in previous analyses. </span><b><span style="font-family:Verdana;">Objective:</span></b><span style="font-family:Verdana;"> To relate the magnitude of tEFL to spirometric values and Modified Medical Research Council (MMRC) score and Asthma Control Test (ACT). </span><b><span style="font-family:Verdana;">Methods:</span></b><span style="font-family:Verdana;"> Tidal EFL was computed as percent of the tidal volume (0% - 100%) spanned (intersected) by the forced expiratory-volume curve. </span><b><span style="font-family:Verdana;">Results: </span></b><span style="font-family:Verdana;">Of 353 patients screened, 192 (114 M, 78 F) patients (136 with COPD, 56 with asthma) had CAL. Overall characteristics: (mean ± SD) age 59 ± 11 years, BMI 28 ± 7, FVC (% pred) 85 ± 20, FEV1 (% pred) 66 ± 21, FEV1/FVC 55% ± 10%, RV (% pred) 147 ± 42. Tidal EFL in patients with tEFL was 53% ± 39%. Using univariate analysis, strongest correlations were between tEFL and FVC and between tEFL and RV in patients with BMI < 30 kg/m</span><sup><span style="font-family:Verdana;">2</span></sup><span style="font-family:Verdana;">. In patients with nonreversible CAL, tEFL was positively associated with increasing MMRC, negatively with spirometric measurements, and positively with RV/TLC. In asthmatics, ACT scores were higher in patients with mean BMI ≥ 28 kg/m</span><sup><span style="font-family:Verdana;">2</span></sup><span style="font-family:Verdana;"> (p < 0.00014) and RV/TLC values > 40% (p < 0.03). </span><b><span style="font-family:Verdana;">Conclusions:</span></b><span style="font-family:Verdana;"> Dyspnea is strongly associated with tEFL and lung function, particularly in patients with nonreversible CAL. Air trapping and </span><span style="font-family:Verdana;">BMI contribute to tEFL.展开更多
Deterioration of city air quality is the serious problem in the process of rapid urbanization and economic development in China. Taking 74 cities that have implemented the new Ambient Air Quality Standards (GB3095- 2...Deterioration of city air quality is the serious problem in the process of rapid urbanization and economic development in China. Taking 74 cities that have implemented the new Ambient Air Quality Standards (GB3095- 2012) since 2013 as examples, using statistical and ArcGIS spatial analysis method, the multi-scale temporal and spatial variations characteristics and the impact of social and economic factors on urban air quality variations, are analyzed in this paper. The main research conclusions are as follows:(1) Air quality in Chinese cities shows very significant seasonal variations, with higher air quality in summer and autumn, and lower air quality in spring and winter; (2) Seen from a daily pollution perspective, air pollution is very serious and will tend to be more serious in the future; (3) Seen from an hourly variation perspective, urban air quality is time coupled with social production and urban living; (4) The overall spatial pattern of urban air quality is high in the east and north and low in the west and south, but with an obvious trend towards regional integration. (5) Cities in different regions have different factors that cause air quality variations. In general, urbanization level and energy consumption per GDP are the common factors.展开更多
文摘Background: The Air Force Health Study collected reproductive outcomes for live-born children of male Air Force veterans of the Vietnam War. Methods: Dioxin values for participants were obtained from blood samples. Analyses were conducted of occurrence of 16 specific categories of birth defects and developmental disabilities. Children were categorized as conceived before and after the start of participants’ Vietnam War service. Children conceived before the start of Vietnam War service were treated as being conceived when their fathers had unquantifiable dioxin values. Children conceived after the start of Vietnam War service for participants with missing dioxin values were excluded from primary analyses, but were used to assess the impact of their exclusion on conclusions. Correlation between values for specific categories for multiple children fathered by the same participant was accounted for. The dose-response relationship was treated as a step function increasing for dioxin values larger than adaptively identified individual thresholds changing with the specific category. Results: For 15 of 16 specific categories, the probability of occurrence increased substantially for a sufficiently high dioxin level above identified thresholds. Exclusion of children due to missing dioxin likely did not affect these results. Conclusions: Results supported the conclusion of substantial adverse effects on a wide variety of specific categories of birth defects and developmental disabilities due to sufficiently high exposures to dioxin, a toxic contaminant of Agent Orange used for herbicide spraying in the Vietnam War. Results may hold more generally, but might also have been affected by a variety of limitations.
基金This work was supported by the Jiangsu Natural Science Fund-Youth Fund(BK20190639)National Nature Science Foundation of China(Nos.21978318,51904300,and 51922106)National Key R&D Program of China(2020YFC1908803).
文摘Surface roughness plays a significant role in floatability of coal.In the present paper,coking coal surface was polished by three different sandpapers and the surface properties were characterized by contact angle and roughness measurements.The effect of surface roughness on floatability was investigated by adhesion force measurement system for measuring interaction forces between droplets/bubbles and coking coal surfaces with different roughness.The results showed that the contact angle decreased with increasing roughness yet the adhesion force between the water droplet and coal surface increased owing to the increased contact line and the appearance of line pinning.Maximum adhesion forces between water and surfaces were 111.70,125.48,and 136.42μN when the roughness was 0.23,0.98,and 2.79 μm,respectively.In contrast,under a liquid environment,the adhesion forces between air bubble/oil droplet and coal surfaces were decreased with increasing roughness because of the restriction by water.Maximum adhesion forces of increasing roughness were 97.14,42.76,and 17.86 μN measured at interfaces between air bubble and coal surfaces and 169.48,145.84,and 121.02 lN between oil droplet and surfaces,respectively.Decreasing roughness could be beneficial to the spreading of oil droplets and the adhesion of bubbles which is conducive to flotation separation.
基金supported by the National Basic Research Program of China[973 Program,grant number 2014CB441202]the National Natural Science Foundation of China[grant numbers41475137 and 91544219]
文摘The effective radiative forcing (ERF) and associated surface air temperature change over eastern China are estimated using multi-model results from CMIP5 (Coupled Model Intercomparison Project Phase 5). The model results show that, relative to 1850, the multi-model and annual mean aerosol ERF for the year 2005 is -4.14 W m^-2 at the top of the atmosphere over eastern China (20°-45°N, 105°-122.5°E). As a result of this ERF, the multi-model and annual mean surface air temperature change in eastern China during 1850-2005 is -1.05℃, leading to a climate sensitivity of 0.24℃/ (Wm^-2) in this region.
基金Supported by Hi-Tech Research and Development Program of China (grants No.2002AA414060)
文摘This paper presents a coupled magnetic-circuit method for computing the magnetic force of air-core reactor under short-time current. The current and the magnetic flux density are computed first and then the magnetic force is obtained. Thus, the dynamic stability performance of air-core reactor can be analyzed at the design stage to reduce experimental cost and shorten the lead-time of product development.
文摘NIKE AIR FORCE 1是NIKE各种鞋类中拥有最大专营模式的系列。从纽约到北京,AIR FORCE 1都是在街头巷尾最热门的鞋款。AIR FORCE 1是以篮球鞋来体现街头HIP HOP精神的典范。在这25年中,有超过1700双不同版本的AIR FORCE 1被制造出来.而AF1的大型庆祝活动将贯穿2007年的春夏秋冬。就在2007年逐步走到年底的时候.NIKE再次重拳出击。推出了SERATO AIR FORCE 1PACK。
文摘The 300 MW steam turbine installed in Waigaoqiao Power Plant with combined HPIP cylinders of double casing structure is a product of the Shanghai Turbine Works utilizing licensed technology. It has a large heat storage capacity and good thermal insulation, so the metal temperature of first stage of HP cylinder (FSMTI) may reach 400-450℃ after shut down and it takes 7-8 days to cool to 150℃ by natural cooling, Now with a forced cooling system the cooling time may be reduced to 40 hours, so that the turbine may be opened for repair work in about 5-6 days. The cooling system for #2 unit and test procedure are briefly described below.
基金Supported by National11th Five-Year Plan Major Scientific and Technological Issues of China(2006BAJ01A04)
文摘Heating-only fan coil(HFC)is one of the suited end users,which is not only compact but also highly efficient.And the major factors affecting the heat dissipation performance of HFC include leakage through coil bypass,distance between fan and coil,fan structure and air inlet type.Under natural air convection or forced,experimental studies were made on the effects of these factors upon the heat dissipation performance of HFC.The results show that:1)After reducing the leakage through coil bypass,the heat dissipation of HFC increases 16.9% under natural convection,and increases 8.3% under forced convection.2)After the distance between fan and coil be raised from 23.2cm to 41.7cm,the heat dissipation of HFC decreases 21.3% under natural convection,but increases12.8% under forced convection.3)After changing the fan structure,the heat dissipation of HFC increases 41.8% under natural convection,and the heat dissipation per motor power increases 96.1% under forced convection.4)The heat dissipations of HFC with round pass,slit and strip type of air inlet are different,whose proportion is about 100%,110%,136% under natural convection,and 100%,105%,116% under forced convection.
基金This work was supported by the project of"Research on the Supporting Technology of Atmospheric Environment for the Sustainable Urban Planning"from China Rural Technology Development Center,Beijing Natural Science Foundation(No.8051002)National Natural Science Foundation of China(No.40505002).
文摘A case study was performed in Beijing in 2000 to observe concentrations of SO2 and NOx in the atmosphere and to evaluate their radiative impact. It was found that the concentrations of these gases are usually high in the morning due to a temperature inversion in the boundary layer. The average concentrations obtained from the observations are much higher than those used in the McClatchey reference atmosphere. The radiative impacts of these gases are calculated using a line-by-line radiative transfer model. The results show that the radiative forcing at the surface due to SO2 is 0.0576 W m^-2 and that due to NOx is 0.0032 W m^-2. These figures are almost compatible with that due to CFC11.
文摘A separation method is proposed to design and improve shock absorber according to the characteristics of each force. The method is validated by rig test. The force data measured during rig test is the resultant force of damping force, rebound force produced by pressed air, and friction force. Different characters of damping force, air rebound force and friction force can be applied to seperate each force from others. A massive produced air filling shock absorber is adopted for the validation. The statistic test is used to get the displacement-force curves. The data are used as the input of separation calculation. Then the tests are carried out again to obtain the force data without air rebound force. The force without air rebound is compared to the data derived from the former tests with the separation method. The result shows that this method can separate the damping force and the air elastic force.
基金The National Science Fund for Distinguished Young Scholars(No.51625803)China and Korea International Cooperation Project of the National Key Research and Development Program(No.2016YEE0119700)+3 种基金the Fundamental Research Funds for the Central Universities(No.3205008102)the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions(No.CE02-2-33)Research and Innovation Project for College Graduates of Jiangsu Province(No.KYLX15_0088,KYLX16_0255)the State Foundation for Studying Abroad,China
文摘Due to the high viscosity of magnetorheological(MR)fluid,eliminating air pockets dissolved in the fluid is very difficult,which results in a force lag phenomenon.In order to evaluate the performance of a semi-active control system based on the MR damper considering the trapped air effect,a performance test on a MR damper is carried out under different loading cases,and the influence of the input current,excitation amplitude and frequency on the force lag phenomenon is analyzed.A concise and efficient parametric model,combining the simple Bouc-Wen model and a spring with small stiffness,is proposed to portray the experimental characteristics of the MR damper with force lag,and then the response analysis of the semi-active controlled single-degree-of-freedom(SDOF)structure is performed using the classic clipped-optimal control strategy based on acceleration feedback.Numerical results show that the trapped air in the MR fluid can weaken the control effect of the MR damper,and the performance of the semi-active control system will be reduced more obviously and become close to the passive-off control with the increasing content of air trapped in the MR fluid.
基金Supported by the National Key Fundamental Research Program of China (No. 51310Z07)
文摘This paper studies the CoNbZr soft magnetic thin film by magnetic force microscopy (MFM). By measuring in atmosphere circumstance, the magnetic force images display some clear dark dots which are corresponding to the clusters in the topography images welL Then the dark dots disappear in magnetic force images, scanning in high vacuum. This indicates that the dark dots are caused by air damping between the vibrating tip and the sample. An interpretation for the above observation is given.
文摘<b>Background:</span></b><span style="font-family:""><span style="font-family:Verdana;"> Tidal expiratory flow limitation (tEFL) is defined as absence of increase in air flow during forced expiration compared to tidal breathing and is related to dyspnea at rest and minimal exertion in patients with chronic airflow limitation (CAL). Tidal EFL has not been expressed as a continuous variable (0% - 100%) in previous analyses. </span><b><span style="font-family:Verdana;">Objective:</span></b><span style="font-family:Verdana;"> To relate the magnitude of tEFL to spirometric values and Modified Medical Research Council (MMRC) score and Asthma Control Test (ACT). </span><b><span style="font-family:Verdana;">Methods:</span></b><span style="font-family:Verdana;"> Tidal EFL was computed as percent of the tidal volume (0% - 100%) spanned (intersected) by the forced expiratory-volume curve. </span><b><span style="font-family:Verdana;">Results: </span></b><span style="font-family:Verdana;">Of 353 patients screened, 192 (114 M, 78 F) patients (136 with COPD, 56 with asthma) had CAL. Overall characteristics: (mean ± SD) age 59 ± 11 years, BMI 28 ± 7, FVC (% pred) 85 ± 20, FEV1 (% pred) 66 ± 21, FEV1/FVC 55% ± 10%, RV (% pred) 147 ± 42. Tidal EFL in patients with tEFL was 53% ± 39%. Using univariate analysis, strongest correlations were between tEFL and FVC and between tEFL and RV in patients with BMI < 30 kg/m</span><sup><span style="font-family:Verdana;">2</span></sup><span style="font-family:Verdana;">. In patients with nonreversible CAL, tEFL was positively associated with increasing MMRC, negatively with spirometric measurements, and positively with RV/TLC. In asthmatics, ACT scores were higher in patients with mean BMI ≥ 28 kg/m</span><sup><span style="font-family:Verdana;">2</span></sup><span style="font-family:Verdana;"> (p < 0.00014) and RV/TLC values > 40% (p < 0.03). </span><b><span style="font-family:Verdana;">Conclusions:</span></b><span style="font-family:Verdana;"> Dyspnea is strongly associated with tEFL and lung function, particularly in patients with nonreversible CAL. Air trapping and </span><span style="font-family:Verdana;">BMI contribute to tEFL.
基金National Natural Sciences Foundation of China(A Study on the resource-environment base for the Modern Man-Land Relationship in China,No.8122015)
文摘Deterioration of city air quality is the serious problem in the process of rapid urbanization and economic development in China. Taking 74 cities that have implemented the new Ambient Air Quality Standards (GB3095- 2012) since 2013 as examples, using statistical and ArcGIS spatial analysis method, the multi-scale temporal and spatial variations characteristics and the impact of social and economic factors on urban air quality variations, are analyzed in this paper. The main research conclusions are as follows:(1) Air quality in Chinese cities shows very significant seasonal variations, with higher air quality in summer and autumn, and lower air quality in spring and winter; (2) Seen from a daily pollution perspective, air pollution is very serious and will tend to be more serious in the future; (3) Seen from an hourly variation perspective, urban air quality is time coupled with social production and urban living; (4) The overall spatial pattern of urban air quality is high in the east and north and low in the west and south, but with an obvious trend towards regional integration. (5) Cities in different regions have different factors that cause air quality variations. In general, urbanization level and energy consumption per GDP are the common factors.