[Objective] With the background of dramatic changes in land use patterns,the aim was to explore the ecosystem services value of Fei County based on RS and GIS.[Method] Ecological changes in the environment can bring c...[Objective] With the background of dramatic changes in land use patterns,the aim was to explore the ecosystem services value of Fei County based on RS and GIS.[Method] Ecological changes in the environment can bring changes in economic value expressed quantitatively by ecosystem service value (ESV).According to modified ESV equivalency factor tables and three periods of interpreted TM remote sensing images in 1990,2000 and 2009,this paper calculated the total ESV in Fei County,Shandong Province,China and analyzed the relationship between ESV and the land-use changes at last.[Result] The results showed that the total ESV of the study area decreased from 2.144×109 yuan in 1990,2.139×109 yuan in 2000,and at last to 2.098×109 yuan in 2009 as the overall study area land use pattern changed dramatically,in which the built-up land increased by 23%,while the cropland and forest were constantly on the decrease.[Conclusion] The research provides theoretical support for the construction of high efficient ecological economic zone and sustainable development of the region.展开更多
The design and applications of a land information system built upon ARC/INFO and ArcView are presented. The proposed system not only maintains all the advantages of the more conventional implementations but also enhan...The design and applications of a land information system built upon ARC/INFO and ArcView are presented. The proposed system not only maintains all the advantages of the more conventional implementations but also enhances them in the following ways: 1) the application program interfaces (API) are used to transmit data and messages among different parts of the system; 2) the integrated system can support studies on land evaluations and ecological analyses by efficient management of attribute and spatial data and 3) correspondingly, spatial records and attributive records are linked by the same identifiers (ID). A case study application in Zigui County of the Three Gorges Area in China demonstrates that the system could employ land-use maps and land property data to predicate and analyze the land utilization changes in the past, present and future. The ecological environment analysis can be carried out with the data of land, economics and terrain map used, showing that the system can be widely applied, especially to survey land and environment resources in the countryside area.展开更多
Hyperspectral data are an important source for monitoring soil salt content on a large scale. However, in previous studies, barriers such as interference due to the presence of vegetation restricted the precision of m...Hyperspectral data are an important source for monitoring soil salt content on a large scale. However, in previous studies, barriers such as interference due to the presence of vegetation restricted the precision of mapping soil salt content. This study tested a new method for predicting soil salt content with improved precision by using Chinese hyperspectral data, Huan Jing-Hyper Spectral Imager(HJ-HSI), in the coastal area of Rudong County, Eastern China. The vegetation-covered area and coastal bare flat area were distinguished by using the normalized differential vegetation index at the band length of 705 nm(NDVI705). The soil salt content of each area was predicted by various algorithms. A Normal Soil Salt Content Response Index(NSSRI) was constructed from continuum-removed reflectance(CR-reflectance) at wavelengths of 908.95 nm and 687.41 nm to predict the soil salt content in the coastal bare flat area(NDVI705 < 0.2). The soil adjusted salinity index(SAVI) was applied to predict the soil salt content in the vegetation-covered area(NDVI705 ≥ 0.2). The results demonstrate that 1) the new method significantly improves the accuracy of soil salt content mapping(R2 = 0.6396, RMSE = 0.3591), and 2) HJ-HSI data can be used to map soil salt content precisely and are suitable for monitoring soil salt content on a large scale.展开更多
Landscape pattern analysis is becoming the core to study global or local change. Incorporated with fast, dynamic and precise spatial information technology, Landscape pattern analysis has been a foundation for the gov...Landscape pattern analysis is becoming the core to study global or local change. Incorporated with fast, dynamic and precise spatial information technology, Landscape pattern analysis has been a foundation for the governments to make decision. In this paper, Maoxian county, located in the northwest of Sichuan Province, was selected as the study area. Landsat TM data in 1994 and Landsat ETM data in 2002, with dates are just same as the time of national policy changes, are classified to make the landscape patterns change. The result indicates that, from 1994 to 2002, owing to the policies of the project of wild wood resource protect and the project of returning land for farming to forestry (grass), the forests has increased about 2.68%, Natural meadow has increased about 0.83%, Shrubby has increased about 0.63%, Farm land has decreased about 4.10% and the fragment of forests in 2002 is lower than in 1994. This states that the national policy actioned during 1990s have much positive influence on the landscape patterns in Maoxian county.展开更多
On July 22, 2013, the Minxian-Zhangxian Ms6. 6 earthquake occurred on the east segment of Lintan-Dangchang fault. The analysis of digital elevation and remote sensing imaging shows that the east segment of Lintan-Dang...On July 22, 2013, the Minxian-Zhangxian Ms6. 6 earthquake occurred on the east segment of Lintan-Dangchang fault. The analysis of digital elevation and remote sensing imaging shows that the east segment of Lintan-Dangchang fault is still active and the main thrust feature of the fault switches to left lateral slip. With the field research of intensity and damage, several abnormal areas of degree VIII spread in the isoseismal line of degree VII and some abnormal areas of degree VII spread in the isoseismal line of degree VI. These abnormal areas are distributed along the hanging wall of the fault in a width of 2km. The analysis based on the remote sensing and digital elevation model shows that the segment of the Lintan-Dangchang fault south of Minxian mainly slips in left literal. The fault movement made the soil soft in the fault zone. The earthquake motion propagated along the fault zone. Therefore the strong earthquake motion caused foundation failure in the soft soil along the fault zone and the abnormal intense areas of disaster formed.展开更多
Source spectra,corner frequency and zero frequency amplitudes in near-source conditions were measured using waveform data from 989 earthquakes with magnitudes larger than ML2.0 observed by the Beijing Digital Telemetr...Source spectra,corner frequency and zero frequency amplitudes in near-source conditions were measured using waveform data from 989 earthquakes with magnitudes larger than ML2.0 observed by the Beijing Digital Telemetry Seismic Network in the Capital Circle Region of China and its surrounding areas from January 2002 to June 2006 by the Brune model.Relevant formulas that were used for the calculation of dynamic source parameters include rupture radius,seismic moment,seismic energy,stress drop,and apparent stress.Scaling relations and characteristics of temporal-spatial variations of these dynamic parameters before the MS5.1 Wenan earthquake in Hebei Province that occurred on July 20,2006 were analyzed.Results show that apparent stress,stress drop,and the ratio of seismic energy to the rupture radius had relatively high values in some areas before the Wenan earthquake.These high-value concentration areas were mainly distributed in the North China Plain seismic zone.As is seen from the time curves,parameters,such as apparent stress,stress drop,and ratio of seismic energy to rupture radius underwent significant ascending processes before the Wenan earthquake,but the variation in the corner frequency showed a descending trend.This result might be related to the enhancement of stress in the North China Plain seismic zone before the earthquake.展开更多
Hyper-spectral data is widely used to determine soil properties. However, few studies have explored the soil spectral characteristics as response to soil erosion. This study analysed the spectral response of different...Hyper-spectral data is widely used to determine soil properties. However, few studies have explored the soil spectral characteristics as response to soil erosion. This study analysed the spectral response of different eroded soils in subtropical China, and then identify the spectral characteristics and soil properties that better discriminate softs with different erosion degrees. Two methods were compared: direct identification by inherent spectral characteristics and indirect identification by predictions of critical soft properties. Results showed that the spectral curves for different degrees of erosion were similar in morphology, while overall reflectance and characteristics of specific absorption peaks were different. When the first method is applied, some differences among different eroded groups were found by integration of associated indicators. However, the index of such indicators showed apparent mixing and crossover among different groups, which reduced the accuracy of identification. For the second method, the correlation between critical soil properties, such as soil organic matter (SOM), iron and aluminium oxides and reflectance spectra, was analysed. The correlation coefficients for the moderate eroded group were primarily between -0.3 to -0.5, which were worse than the other twogroups. However, the maximum value of R2 was obtained as 0.86 and 0.94 for the non-apparent eroded and the severe group. Furthermore, these two groups also showed some differences in the spectral response of iron complex state (Fep), Aluminium amorphous state (Alo) and the modelling results for soil organic matter (SOM). The study proved that it is feasible to identify different degrees of soil erosion by hyperspectral data, and that indirect identification by modelling critical soil properties and reflectance spectra is much better than direct identification. These results indicate that hyper-spectral data may represent a promising tool in monitoring and modelling soil erosion.展开更多
The M_S6. 1 earthquake was a foreshock-mainshock-aftershock type which occurred in the boundary region between Zogang and Markam counties on August 12,2013. Within 9hours before the main shock seven earthquakes of gre...The M_S6. 1 earthquake was a foreshock-mainshock-aftershock type which occurred in the boundary region between Zogang and Markam counties on August 12,2013. Within 9hours before the main shock seven earthquakes of greater than M_L2. 0 occurred,with a maximum of M_L4. 7. In this paper,the earthquake focal mechanism changing process of the Zogang-Markam M_S6. 1 earthquake sequence is studied by calculating the correlation coefficient of body wave spectral amplitudes,and the result shows that the correlation coefficients of spectral amplitude of foreshocks present high value fluctuation with an average value of 0. 86,which shows that the focal mechanism of foreshocks are similar;and the correlation coefficients of spectral amplitude of aftershocks present low value,which shows that the possibility of a large earthquake is not high after a time.展开更多
A catastrophic landslide occurred at Xinmo village in Maoxian County, Sichuan Province,China, on June 24, 2017. A 2.87×106 m3 rock mass collapsed and entrained the surface soil layer along the landslide path. Eig...A catastrophic landslide occurred at Xinmo village in Maoxian County, Sichuan Province,China, on June 24, 2017. A 2.87×106 m3 rock mass collapsed and entrained the surface soil layer along the landslide path. Eighty-three people were killed or went missing and more than 103 houses were destroyed. In this paper, the geological conditions of the landslide are analyzed via field investigation and high-resolution imagery. The dynamic process and runout characteristics of the landslide are numerically analyzed using a depth-integrated continuum method and Mac Cormack-TVD finite difference algorithm.Computational results show that the evaluated area of the danger zone matchs well with the results of field investigation. It is worth noting that soil sprayed by the high-speed blast needs to be taken into account for such kind of large high-locality landslide. The maximum velocity is about 55 m/s, which is consistent with most cases. In addition, the potential danger zone of an unstable block is evaluated. The potential risk area evaluated by the efficient depthintegrated continuum method could play a significant role in disaster prevention and secondary hazard avoidance during rescue operations.展开更多
An earthquake measuring 5.1 on the Richter scale struck Wen'an county,Hebei Province on July 4,2006. No casualties have been reported,with only slight damage. The disaster level of this event is the slightest on t...An earthquake measuring 5.1 on the Richter scale struck Wen'an county,Hebei Province on July 4,2006. No casualties have been reported,with only slight damage. The disaster level of this event is the slightest on the M4.9~5.1 events record tally since the CCDSN (China Center of Digital Seismic Network) was built in 1999. The epicenter intensity of this earthquake was low,while in areas like Beijing,which is 100km far away,abnormal high intensity zones appeared. This article discusses the reasons behind this abnormal phenomenon,with the diagrams of intensity isolines drawn by the intense seismic stations and networks in the capital circle area as references,as well as the seismogenic mechanism in the source,the seismic histories,the geological structures and the ray pathways of seismic waves in areas within 150km around the epicenter. It was concluded that the special dynamic and geological situations were the main causes for the lower intensity degree and slight damage in the epicenter area,but higher intensity in the surrounding areas.展开更多
On the basis of extending Lee's(1999) model, this paper resolves the problem of biased division in the specification of equation and employs Urban Household Survey(UHS) data,China Household Income Project(CHIP) da...On the basis of extending Lee's(1999) model, this paper resolves the problem of biased division in the specification of equation and employs Urban Household Survey(UHS) data,China Household Income Project(CHIP) data and county-level minimum wage data collected by authors to investigate the wage distribution effects of change in the effective minimum wages measured by relative value. The result shows that the effective minimum wage will exert a significant spillover effect on wage distribution at the40 th percentile and below, which is favorable to reducing wage gaps at the bottom. This conclusion holds true under various robustness tests. However, the shrinking effective minimum wage has created a downward drag on wages, thus widening wage gaps at the bottom. The shrinking effective minimum wage contributed 150%,53.8%,45.5% and16.7% to the wage gaps at the 10 th, 20 th, 30 th and 40 th percentiles compared with the 50 th percentile. Therefore, the key to ensuring the effectiveness of minimum wages lies in the implementation of an automatic adjustment mechanism correlated with macroeconomic indicators. Compliance with minimum wages must be guaranteed and change in minimum wages must be measured with relative value.展开更多
Temperature changes are known to have significant impacts on human health. Accurate estimates of population-weighted average monthly air temperature for US counties are needed to evaluate temperature's association wi...Temperature changes are known to have significant impacts on human health. Accurate estimates of population-weighted average monthly air temperature for US counties are needed to evaluate temperature's association with health behaviours and disease, which are sampled or reported at the county level and measured on a monthly--or 30-day--basis. Most reported temperature estimates were calculated using ArcGIS, relatively few used SAS. We compared the performance of geostatistical models to estimate population-weighted average temperature in each month for counties in 48 states using ArcGIS v9.3 and SAS v 9.2 on a CITGO platform. Monthly average temperature for Jan-Dec 2007 and elevation from 5435 weather stations were used to estimate the temperature at county population centroids. County estimates were produced with elevation as a covariate. Performance of models was assessed by comparing adjusted R2, mean squared error, root mean squared error, and processing time. Prediction accuracy for split validation was above 90% for 11 months in ArcGIS and all 12 months in SAS. Cokriging in SAS achieved higher prediction accuracy and lower estimation bias as compared to cokriging in ArcGIS. County-level estimates produced by both packages were positively correlated (adjusted R2 range=0.95 to 0.99); accuracy and precision improved with elevation as a covariate. Both methods from ArcGIS and SAS are reliable for U.S. county-level temperature estimates; However, ArcGIS's merits in spatial data pre-processing and processing time may be important considerations for software selection, especially for multi-year or multi-state projects.展开更多
基金supported by Fei county land and resources bureau of Shandong province
文摘[Objective] With the background of dramatic changes in land use patterns,the aim was to explore the ecosystem services value of Fei County based on RS and GIS.[Method] Ecological changes in the environment can bring changes in economic value expressed quantitatively by ecosystem service value (ESV).According to modified ESV equivalency factor tables and three periods of interpreted TM remote sensing images in 1990,2000 and 2009,this paper calculated the total ESV in Fei County,Shandong Province,China and analyzed the relationship between ESV and the land-use changes at last.[Result] The results showed that the total ESV of the study area decreased from 2.144×109 yuan in 1990,2.139×109 yuan in 2000,and at last to 2.098×109 yuan in 2009 as the overall study area land use pattern changed dramatically,in which the built-up land increased by 23%,while the cropland and forest were constantly on the decrease.[Conclusion] The research provides theoretical support for the construction of high efficient ecological economic zone and sustainable development of the region.
基金Project supported by the National Natural Science Foundation of China (No. 49801010) the Chinese Academy of Sciences (No. KZ951-A1-202-02-01).
文摘The design and applications of a land information system built upon ARC/INFO and ArcView are presented. The proposed system not only maintains all the advantages of the more conventional implementations but also enhances them in the following ways: 1) the application program interfaces (API) are used to transmit data and messages among different parts of the system; 2) the integrated system can support studies on land evaluations and ecological analyses by efficient management of attribute and spatial data and 3) correspondingly, spatial records and attributive records are linked by the same identifiers (ID). A case study application in Zigui County of the Three Gorges Area in China demonstrates that the system could employ land-use maps and land property data to predicate and analyze the land utilization changes in the past, present and future. The ecological environment analysis can be carried out with the data of land, economics and terrain map used, showing that the system can be widely applied, especially to survey land and environment resources in the countryside area.
基金Under the auspices of National Natural Science Foundation of China(No.41230751,41101547)Scientific Research Foundation of Graduate School of Nanjing University(No.2012CL14)
文摘Hyperspectral data are an important source for monitoring soil salt content on a large scale. However, in previous studies, barriers such as interference due to the presence of vegetation restricted the precision of mapping soil salt content. This study tested a new method for predicting soil salt content with improved precision by using Chinese hyperspectral data, Huan Jing-Hyper Spectral Imager(HJ-HSI), in the coastal area of Rudong County, Eastern China. The vegetation-covered area and coastal bare flat area were distinguished by using the normalized differential vegetation index at the band length of 705 nm(NDVI705). The soil salt content of each area was predicted by various algorithms. A Normal Soil Salt Content Response Index(NSSRI) was constructed from continuum-removed reflectance(CR-reflectance) at wavelengths of 908.95 nm and 687.41 nm to predict the soil salt content in the coastal bare flat area(NDVI705 < 0.2). The soil adjusted salinity index(SAVI) was applied to predict the soil salt content in the vegetation-covered area(NDVI705 ≥ 0.2). The results demonstrate that 1) the new method significantly improves the accuracy of soil salt content mapping(R2 = 0.6396, RMSE = 0.3591), and 2) HJ-HSI data can be used to map soil salt content precisely and are suitable for monitoring soil salt content on a large scale.
文摘Landscape pattern analysis is becoming the core to study global or local change. Incorporated with fast, dynamic and precise spatial information technology, Landscape pattern analysis has been a foundation for the governments to make decision. In this paper, Maoxian county, located in the northwest of Sichuan Province, was selected as the study area. Landsat TM data in 1994 and Landsat ETM data in 2002, with dates are just same as the time of national policy changes, are classified to make the landscape patterns change. The result indicates that, from 1994 to 2002, owing to the policies of the project of wild wood resource protect and the project of returning land for farming to forestry (grass), the forests has increased about 2.68%, Natural meadow has increased about 0.83%, Shrubby has increased about 0.63%, Farm land has decreased about 4.10% and the fragment of forests in 2002 is lower than in 1994. This states that the national policy actioned during 1990s have much positive influence on the landscape patterns in Maoxian county.
基金supported by basic scientific research operating expenses of Institute of Earthquake Science,China Earthquake Administration(2012IES010202)
文摘On July 22, 2013, the Minxian-Zhangxian Ms6. 6 earthquake occurred on the east segment of Lintan-Dangchang fault. The analysis of digital elevation and remote sensing imaging shows that the east segment of Lintan-Dangchang fault is still active and the main thrust feature of the fault switches to left lateral slip. With the field research of intensity and damage, several abnormal areas of degree VIII spread in the isoseismal line of degree VII and some abnormal areas of degree VII spread in the isoseismal line of degree VI. These abnormal areas are distributed along the hanging wall of the fault in a width of 2km. The analysis based on the remote sensing and digital elevation model shows that the segment of the Lintan-Dangchang fault south of Minxian mainly slips in left literal. The fault movement made the soil soft in the fault zone. The earthquake motion propagated along the fault zone. Therefore the strong earthquake motion caused foundation failure in the soft soil along the fault zone and the abnormal intense areas of disaster formed.
基金the Special Research Fund for Earthquake Science,China (200708023)
文摘Source spectra,corner frequency and zero frequency amplitudes in near-source conditions were measured using waveform data from 989 earthquakes with magnitudes larger than ML2.0 observed by the Beijing Digital Telemetry Seismic Network in the Capital Circle Region of China and its surrounding areas from January 2002 to June 2006 by the Brune model.Relevant formulas that were used for the calculation of dynamic source parameters include rupture radius,seismic moment,seismic energy,stress drop,and apparent stress.Scaling relations and characteristics of temporal-spatial variations of these dynamic parameters before the MS5.1 Wenan earthquake in Hebei Province that occurred on July 20,2006 were analyzed.Results show that apparent stress,stress drop,and the ratio of seismic energy to the rupture radius had relatively high values in some areas before the Wenan earthquake.These high-value concentration areas were mainly distributed in the North China Plain seismic zone.As is seen from the time curves,parameters,such as apparent stress,stress drop,and ratio of seismic energy to rupture radius underwent significant ascending processes before the Wenan earthquake,but the variation in the corner frequency showed a descending trend.This result might be related to the enhancement of stress in the North China Plain seismic zone before the earthquake.
文摘Hyper-spectral data is widely used to determine soil properties. However, few studies have explored the soil spectral characteristics as response to soil erosion. This study analysed the spectral response of different eroded soils in subtropical China, and then identify the spectral characteristics and soil properties that better discriminate softs with different erosion degrees. Two methods were compared: direct identification by inherent spectral characteristics and indirect identification by predictions of critical soft properties. Results showed that the spectral curves for different degrees of erosion were similar in morphology, while overall reflectance and characteristics of specific absorption peaks were different. When the first method is applied, some differences among different eroded groups were found by integration of associated indicators. However, the index of such indicators showed apparent mixing and crossover among different groups, which reduced the accuracy of identification. For the second method, the correlation between critical soil properties, such as soil organic matter (SOM), iron and aluminium oxides and reflectance spectra, was analysed. The correlation coefficients for the moderate eroded group were primarily between -0.3 to -0.5, which were worse than the other twogroups. However, the maximum value of R2 was obtained as 0.86 and 0.94 for the non-apparent eroded and the severe group. Furthermore, these two groups also showed some differences in the spectral response of iron complex state (Fep), Aluminium amorphous state (Alo) and the modelling results for soil organic matter (SOM). The study proved that it is feasible to identify different degrees of soil erosion by hyperspectral data, and that indirect identification by modelling critical soil properties and reflectance spectra is much better than direct identification. These results indicate that hyper-spectral data may represent a promising tool in monitoring and modelling soil erosion.
基金jointly sponsored by the Special Program of Earthquake Science and Technology of Earthquake Administration of Sichuan Province(LY1302) the National Key Technology R&D Program of China(2012BAK19802)
文摘The M_S6. 1 earthquake was a foreshock-mainshock-aftershock type which occurred in the boundary region between Zogang and Markam counties on August 12,2013. Within 9hours before the main shock seven earthquakes of greater than M_L2. 0 occurred,with a maximum of M_L4. 7. In this paper,the earthquake focal mechanism changing process of the Zogang-Markam M_S6. 1 earthquake sequence is studied by calculating the correlation coefficient of body wave spectral amplitudes,and the result shows that the correlation coefficients of spectral amplitude of foreshocks present high value fluctuation with an average value of 0. 86,which shows that the focal mechanism of foreshocks are similar;and the correlation coefficients of spectral amplitude of aftershocks present low value,which shows that the possibility of a large earthquake is not high after a time.
基金Financial support from National Nature Science Foundation of China (Grant No. 41572303, 41520104002)Chinese Academy of Sciences “Light of West China” Program and Youth Innovation Promotion Association
文摘A catastrophic landslide occurred at Xinmo village in Maoxian County, Sichuan Province,China, on June 24, 2017. A 2.87×106 m3 rock mass collapsed and entrained the surface soil layer along the landslide path. Eighty-three people were killed or went missing and more than 103 houses were destroyed. In this paper, the geological conditions of the landslide are analyzed via field investigation and high-resolution imagery. The dynamic process and runout characteristics of the landslide are numerically analyzed using a depth-integrated continuum method and Mac Cormack-TVD finite difference algorithm.Computational results show that the evaluated area of the danger zone matchs well with the results of field investigation. It is worth noting that soil sprayed by the high-speed blast needs to be taken into account for such kind of large high-locality landslide. The maximum velocity is about 55 m/s, which is consistent with most cases. In addition, the potential danger zone of an unstable block is evaluated. The potential risk area evaluated by the efficient depthintegrated continuum method could play a significant role in disaster prevention and secondary hazard avoidance during rescue operations.
基金funded by the project "Demonstration of typical changes of vulne rability of disasters in urban-rural fringe:a case study of seismic disaster in the Beijing-Tianjin-Tangshan region" of National Natural Science Foundation (Grant No.40771011)
文摘An earthquake measuring 5.1 on the Richter scale struck Wen'an county,Hebei Province on July 4,2006. No casualties have been reported,with only slight damage. The disaster level of this event is the slightest on the M4.9~5.1 events record tally since the CCDSN (China Center of Digital Seismic Network) was built in 1999. The epicenter intensity of this earthquake was low,while in areas like Beijing,which is 100km far away,abnormal high intensity zones appeared. This article discusses the reasons behind this abnormal phenomenon,with the diagrams of intensity isolines drawn by the intense seismic stations and networks in the capital circle area as references,as well as the seismogenic mechanism in the source,the seismic histories,the geological structures and the ray pathways of seismic waves in areas within 150km around the epicenter. It was concluded that the special dynamic and geological situations were the main causes for the lower intensity degree and slight damage in the epicenter area,but higher intensity in the surrounding areas.
基金a result of the Youth Program of the National Natural Science Foundation of China(Grant No.:7140328971403307)
文摘On the basis of extending Lee's(1999) model, this paper resolves the problem of biased division in the specification of equation and employs Urban Household Survey(UHS) data,China Household Income Project(CHIP) data and county-level minimum wage data collected by authors to investigate the wage distribution effects of change in the effective minimum wages measured by relative value. The result shows that the effective minimum wage will exert a significant spillover effect on wage distribution at the40 th percentile and below, which is favorable to reducing wage gaps at the bottom. This conclusion holds true under various robustness tests. However, the shrinking effective minimum wage has created a downward drag on wages, thus widening wage gaps at the bottom. The shrinking effective minimum wage contributed 150%,53.8%,45.5% and16.7% to the wage gaps at the 10 th, 20 th, 30 th and 40 th percentiles compared with the 50 th percentile. Therefore, the key to ensuring the effectiveness of minimum wages lies in the implementation of an automatic adjustment mechanism correlated with macroeconomic indicators. Compliance with minimum wages must be guaranteed and change in minimum wages must be measured with relative value.
基金supported by the CDC Public Health Informatics Fellowship Program (PHIFP)supported by the Dental, Oral and Craniofacial Data Resource Center, a joint project of CDC’s Division of Oral Health and NIH’s National Institute of Dental and Craniofacial Research
文摘Temperature changes are known to have significant impacts on human health. Accurate estimates of population-weighted average monthly air temperature for US counties are needed to evaluate temperature's association with health behaviours and disease, which are sampled or reported at the county level and measured on a monthly--or 30-day--basis. Most reported temperature estimates were calculated using ArcGIS, relatively few used SAS. We compared the performance of geostatistical models to estimate population-weighted average temperature in each month for counties in 48 states using ArcGIS v9.3 and SAS v 9.2 on a CITGO platform. Monthly average temperature for Jan-Dec 2007 and elevation from 5435 weather stations were used to estimate the temperature at county population centroids. County estimates were produced with elevation as a covariate. Performance of models was assessed by comparing adjusted R2, mean squared error, root mean squared error, and processing time. Prediction accuracy for split validation was above 90% for 11 months in ArcGIS and all 12 months in SAS. Cokriging in SAS achieved higher prediction accuracy and lower estimation bias as compared to cokriging in ArcGIS. County-level estimates produced by both packages were positively correlated (adjusted R2 range=0.95 to 0.99); accuracy and precision improved with elevation as a covariate. Both methods from ArcGIS and SAS are reliable for U.S. county-level temperature estimates; However, ArcGIS's merits in spatial data pre-processing and processing time may be important considerations for software selection, especially for multi-year or multi-state projects.