Pub Date : 2017-01-01DOI: 10.1080/23312041.2017.1307566
Friday Uchenna Ochege, C. Okpala-Okaka
Abstract This study demonstrates a 30-year multi-temporal variations in vegetation cover changes as a means of filling the vegetation knowledge gap in the humid tropical forests of southeastern Nigeria. Landsats 4TM, 5TM and 7ETM+ data-sets were accessed and analysed using the Maximum Likelihood Classification algorithm to discriminate and geovisualize the spatiotemporal variations in the general vegetation and other land cover types, from 1984 to 2014. This was supported with detailed field surveys in dry and rainy seasons of 2011 and 2014 to ascertain the status of wide-ranging vegetation cover stands. A 44% vegetation decline was recorded given the reduction in dense vegetation spatial extent from 330.63 km2 in 1984 to 170.87 km2 in 2014. Sparse vegetation equally increased in spatial extent by 25% given the variations registered from 6.86 km2 in 1984 to 97.16 km2 in 2014. The reduction in vegetation cover was found to have been replaced by increase in other land cover types—residential (18.97 km2) and industrial areas (39.87 km2). Suggesting that, heterogeneity in the spatial distribution of land resources, in addition to weak concerns towards preserving the accruing benefits of vegetation resources attracted anthropogenic phenomenon (e.g. urbanization) to vegetated areas. As such, strengthening institutional monitoring and urban planning frameworks would help to improve sustainable governance of the tropical rainforests.
{"title":"Remote sensing of vegetation cover changes in the humid tropical rainforests of Southeastern Nigeria (1984–2014)","authors":"Friday Uchenna Ochege, C. Okpala-Okaka","doi":"10.1080/23312041.2017.1307566","DOIUrl":"https://doi.org/10.1080/23312041.2017.1307566","url":null,"abstract":"Abstract This study demonstrates a 30-year multi-temporal variations in vegetation cover changes as a means of filling the vegetation knowledge gap in the humid tropical forests of southeastern Nigeria. Landsats 4TM, 5TM and 7ETM+ data-sets were accessed and analysed using the Maximum Likelihood Classification algorithm to discriminate and geovisualize the spatiotemporal variations in the general vegetation and other land cover types, from 1984 to 2014. This was supported with detailed field surveys in dry and rainy seasons of 2011 and 2014 to ascertain the status of wide-ranging vegetation cover stands. A 44% vegetation decline was recorded given the reduction in dense vegetation spatial extent from 330.63 km2 in 1984 to 170.87 km2 in 2014. Sparse vegetation equally increased in spatial extent by 25% given the variations registered from 6.86 km2 in 1984 to 97.16 km2 in 2014. The reduction in vegetation cover was found to have been replaced by increase in other land cover types—residential (18.97 km2) and industrial areas (39.87 km2). Suggesting that, heterogeneity in the spatial distribution of land resources, in addition to weak concerns towards preserving the accruing benefits of vegetation resources attracted anthropogenic phenomenon (e.g. urbanization) to vegetated areas. As such, strengthening institutional monitoring and urban planning frameworks would help to improve sustainable governance of the tropical rainforests.","PeriodicalId":42883,"journal":{"name":"Cogent Geoscience","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/23312041.2017.1307566","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42531808","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-01-01DOI: 10.1080/23312041.2017.1356012
M. Ramírez-Herrera, K. Gaidzik
Abstract Extreme storms commonly trigger landslides in regions of humid, warm tropical climate causing loss of life and economic devastation. The tropical mountainous areas of Guerrero in southwest Mexico are frequently hit by extreme hurricanes and cyclones and thus prone to landslides. On 16 September 2013, a huge landslide resulted in 71 fatalities and destroyed a large part of La Pintada Village. We applied remote sensing techniques using the LIDAR DEM and high-resolution images of the La Pintada area, a post-landslide field survey, geotechnical laboratory tests of colluvium material from the landslide, and a slope stability analysis. We also interviewed eyewitnesses accounts of the event. Our results suggest that the 2013 La Pintada landslide was a complex and two-stage event. An intense four-day-long rainfall event related to the landfall of Hurricane Manuel resulted in the oversaturation of soil, which was the main factor that caused the landslide. The effect of rainfall was amplified by the lack of high and dense vegetation on the 250-m-high slope. The lack of vegetation and slope-under-cutting likely contributed to the decreased slope stability. We suggest that increased intensity of extreme storms has contributed to increased landslides in this area. Furthermore, in tropical climate areas, where significant population lives in mostly developing countries, the combination of these phenomena makes them highly vulnerable to extreme storms and landslide hazards.
{"title":"La Pintada landslide—A complex double-staged extreme event, Guerrero, Mexico","authors":"M. Ramírez-Herrera, K. Gaidzik","doi":"10.1080/23312041.2017.1356012","DOIUrl":"https://doi.org/10.1080/23312041.2017.1356012","url":null,"abstract":"Abstract Extreme storms commonly trigger landslides in regions of humid, warm tropical climate causing loss of life and economic devastation. The tropical mountainous areas of Guerrero in southwest Mexico are frequently hit by extreme hurricanes and cyclones and thus prone to landslides. On 16 September 2013, a huge landslide resulted in 71 fatalities and destroyed a large part of La Pintada Village. We applied remote sensing techniques using the LIDAR DEM and high-resolution images of the La Pintada area, a post-landslide field survey, geotechnical laboratory tests of colluvium material from the landslide, and a slope stability analysis. We also interviewed eyewitnesses accounts of the event. Our results suggest that the 2013 La Pintada landslide was a complex and two-stage event. An intense four-day-long rainfall event related to the landfall of Hurricane Manuel resulted in the oversaturation of soil, which was the main factor that caused the landslide. The effect of rainfall was amplified by the lack of high and dense vegetation on the 250-m-high slope. The lack of vegetation and slope-under-cutting likely contributed to the decreased slope stability. We suggest that increased intensity of extreme storms has contributed to increased landslides in this area. Furthermore, in tropical climate areas, where significant population lives in mostly developing countries, the combination of these phenomena makes them highly vulnerable to extreme storms and landslide hazards.","PeriodicalId":42883,"journal":{"name":"Cogent Geoscience","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/23312041.2017.1356012","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41929799","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-01-01DOI: 10.1080/23312041.2017.1416877
M. Javari
Abstract Rainfall variability is among the main challenges confronted when simulating the spatial patterns of climatic changes under different environmental conditions, particularly in countries with arid and semiarid climates such as Iran. Climate changes simulation, through geostatistical modeling, have made possible to develop the understanding of spatial variability, e.g. daily rainfall. This article presents some spatial variability simulations of average values of the daily rainfall for Iran from 170 stations and 39,042 rainfall points by comparing geostatistical techniques based on the prediction errors. For the spatial variability simulation of average values of the daily rainfall, rainfall data series of 1975–2014 was used to analyze the accuracy of geostatistical models. Four statistical error assessment measures, mean absolute deviation prediction errors, mean square prediction errors, root mean square prediction error (RMSPE), and coefficient of determination (R2), were used to assess and compare the interpolation techniques. Tetraspherical Ordinary Kriging, Exponential Kernel Smoothing, Order 5 Polynomial Kernel Smoothing, and Quartic Kernel Smoothing were selected as the best spatial models for simulating daily rainfall variability, in the order of their performance. The RMSPE varied between 0.042 and 2.639 were predicted by employed models for average values of the daily rainfall.
{"title":"Geostatistical modeling to simulate daily rainfall variability in Iran","authors":"M. Javari","doi":"10.1080/23312041.2017.1416877","DOIUrl":"https://doi.org/10.1080/23312041.2017.1416877","url":null,"abstract":"Abstract Rainfall variability is among the main challenges confronted when simulating the spatial patterns of climatic changes under different environmental conditions, particularly in countries with arid and semiarid climates such as Iran. Climate changes simulation, through geostatistical modeling, have made possible to develop the understanding of spatial variability, e.g. daily rainfall. This article presents some spatial variability simulations of average values of the daily rainfall for Iran from 170 stations and 39,042 rainfall points by comparing geostatistical techniques based on the prediction errors. For the spatial variability simulation of average values of the daily rainfall, rainfall data series of 1975–2014 was used to analyze the accuracy of geostatistical models. Four statistical error assessment measures, mean absolute deviation prediction errors, mean square prediction errors, root mean square prediction error (RMSPE), and coefficient of determination (R2), were used to assess and compare the interpolation techniques. Tetraspherical Ordinary Kriging, Exponential Kernel Smoothing, Order 5 Polynomial Kernel Smoothing, and Quartic Kernel Smoothing were selected as the best spatial models for simulating daily rainfall variability, in the order of their performance. The RMSPE varied between 0.042 and 2.639 were predicted by employed models for average values of the daily rainfall.","PeriodicalId":42883,"journal":{"name":"Cogent Geoscience","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/23312041.2017.1416877","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43207215","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-01-01DOI: 10.1080/23312041.2017.1354468
Tatsuya Ishige
Abstract Our purpose is to trace a contour in the form of a polygon. In this research, we use a bicubic spline function for interpolation of the elevation data on a grid covering the area of concern. We construct the polygon as a data consisting of ordered contour points on sides of the grid. The contour enters a cell at an entry point and goes out at an exit point on its sides. The polygon is formed connecting these points. A problem occurs as to which two points should be connected when a cell of the grid has more than three contour points on its sides. As for existing methods of the differential geometry such as discretization using tangential increments, it is difficult to predetermine a suitable step size to arrive at a next contour point correctly if several contour components wind closely to each other within a cell. As a solution, we take an algebraic approach exploiting a simple fact that a bicubic function is viewed as a univariate cubic function with a parameter. From this perspective, we identify the exit point examining the behavior of the real roots of the cubic equation for the contour in terms of the numerical order. Our method enables us to faithfully trace the contour of bicubic spline functions which provide smoother and better fitting curves than bilinear spline functions used by the other authors. Computation time is exhibited in the numerical experiment for an island in Japan.
{"title":"Contour tracing for geographical digital data","authors":"Tatsuya Ishige","doi":"10.1080/23312041.2017.1354468","DOIUrl":"https://doi.org/10.1080/23312041.2017.1354468","url":null,"abstract":"Abstract Our purpose is to trace a contour in the form of a polygon. In this research, we use a bicubic spline function for interpolation of the elevation data on a grid covering the area of concern. We construct the polygon as a data consisting of ordered contour points on sides of the grid. The contour enters a cell at an entry point and goes out at an exit point on its sides. The polygon is formed connecting these points. A problem occurs as to which two points should be connected when a cell of the grid has more than three contour points on its sides. As for existing methods of the differential geometry such as discretization using tangential increments, it is difficult to predetermine a suitable step size to arrive at a next contour point correctly if several contour components wind closely to each other within a cell. As a solution, we take an algebraic approach exploiting a simple fact that a bicubic function is viewed as a univariate cubic function with a parameter. From this perspective, we identify the exit point examining the behavior of the real roots of the cubic equation for the contour in terms of the numerical order. Our method enables us to faithfully trace the contour of bicubic spline functions which provide smoother and better fitting curves than bilinear spline functions used by the other authors. Computation time is exhibited in the numerical experiment for an island in Japan.","PeriodicalId":42883,"journal":{"name":"Cogent Geoscience","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/23312041.2017.1354468","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42809663","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-01-01DOI: 10.1080/23312041.2017.1353719
Gebremedhin Kiros, Amba Shetty, L. Nandagiri
Abstract Statistical analysis of continuous daily climate data and extensive weather records are important to evaluate possible long-term, hydrologic/climatic changes at local and regional scales. In the present study, daily rainfall data recorded in the period 1971–2013 (43 years) at seven meteorological stations distributed in the Geba River basin, northern Ethiopia were used to study trends in extreme rainfall indices at different temporal scales. The selected rainfall indices focus on intensity, frequency, and duration of extreme rainfall measures. The Mann– Kendall trend test results show that decreasing tendencies in the rainfall indices have predominantly observed in several stations, even though most of the stations did not show statistically significant trend over time at 95% significance level during the study period. In majority of the extreme rainfall indices, station Abiadi which is located at the downstream of the basin showed statistically significant increasing trend, while decreasing trend in very heavy rainfall days (R20mm) for Adigrat station, and consecutive dry days (CDD) and highest rainfall amount in one-day period (RX1day) for Mek’ele showed statistically significant at the 95% level of significance. Results of this study contribute to climate change research in the region and provide inputs for better planning toward adapting to changing climate.
{"title":"Extreme rainfall signatures under changing climate in semi-arid northern highlands of Ethiopia","authors":"Gebremedhin Kiros, Amba Shetty, L. Nandagiri","doi":"10.1080/23312041.2017.1353719","DOIUrl":"https://doi.org/10.1080/23312041.2017.1353719","url":null,"abstract":"Abstract Statistical analysis of continuous daily climate data and extensive weather records are important to evaluate possible long-term, hydrologic/climatic changes at local and regional scales. In the present study, daily rainfall data recorded in the period 1971–2013 (43 years) at seven meteorological stations distributed in the Geba River basin, northern Ethiopia were used to study trends in extreme rainfall indices at different temporal scales. The selected rainfall indices focus on intensity, frequency, and duration of extreme rainfall measures. The Mann– Kendall trend test results show that decreasing tendencies in the rainfall indices have predominantly observed in several stations, even though most of the stations did not show statistically significant trend over time at 95% significance level during the study period. In majority of the extreme rainfall indices, station Abiadi which is located at the downstream of the basin showed statistically significant increasing trend, while decreasing trend in very heavy rainfall days (R20mm) for Adigrat station, and consecutive dry days (CDD) and highest rainfall amount in one-day period (RX1day) for Mek’ele showed statistically significant at the 95% level of significance. Results of this study contribute to climate change research in the region and provide inputs for better planning toward adapting to changing climate.","PeriodicalId":42883,"journal":{"name":"Cogent Geoscience","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/23312041.2017.1353719","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42113716","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-01-01DOI: 10.1080/23312041.2017.1319259
R. Hewson, D. Robson, A. Carlton, P. Gilmore
Abstract One of the major problems faced by the application of geological remote sensing is its potential limitation in areas of a temperate climate with agricultural cultivation, limited outcrops and vegetation cover. This was the issue experienced when it was attempted to use the multi-spectral satellite Advanced Spaceborne Thermal Emission Reflectance Radiometer (ASTER) imagery to assist the updating of 1:100,000 geological mapping with the Ardlethan/Barmedman map sheets of central New South Wales (NSW), Australia. Most successful applications of geological remote sensing have been achieved in arid to semi-arid environments where vegetation and cultivation is minimal. Typically, day-time acquired ASTER visible to shortwave surface reflectance derived map products has extracted useful mineral related compositional information in such areas however in the studied areas of central NSW these techniques proved limited, particularly when using large mosaicked products such as the National Australia ASTER Geoscience Maps. Some improvement in geological discrimination was achieved using individual ASTER scenes, masked by high slope angle and processed into spectrally unmixed products. An alternative approach to extracting geoscience related products, utilised, night-time acquired ASTER thermal products. Their surface kinetic temperature products showed some potential for identifying the limited and sparse outcrops useful for field mapping geologists. Overall this study also showed the importance of the image spatial resolution in vegetated and cultivated areas with limited outcrop. Ideally a finer spatial image product than available with ASTER’s VNIR-SWIR combined products at 30 m is required.
{"title":"Geological application of ASTER remote sensing within sparsely outcropping terrain, Central New South Wales, Australia","authors":"R. Hewson, D. Robson, A. Carlton, P. Gilmore","doi":"10.1080/23312041.2017.1319259","DOIUrl":"https://doi.org/10.1080/23312041.2017.1319259","url":null,"abstract":"Abstract One of the major problems faced by the application of geological remote sensing is its potential limitation in areas of a temperate climate with agricultural cultivation, limited outcrops and vegetation cover. This was the issue experienced when it was attempted to use the multi-spectral satellite Advanced Spaceborne Thermal Emission Reflectance Radiometer (ASTER) imagery to assist the updating of 1:100,000 geological mapping with the Ardlethan/Barmedman map sheets of central New South Wales (NSW), Australia. Most successful applications of geological remote sensing have been achieved in arid to semi-arid environments where vegetation and cultivation is minimal. Typically, day-time acquired ASTER visible to shortwave surface reflectance derived map products has extracted useful mineral related compositional information in such areas however in the studied areas of central NSW these techniques proved limited, particularly when using large mosaicked products such as the National Australia ASTER Geoscience Maps. Some improvement in geological discrimination was achieved using individual ASTER scenes, masked by high slope angle and processed into spectrally unmixed products. An alternative approach to extracting geoscience related products, utilised, night-time acquired ASTER thermal products. Their surface kinetic temperature products showed some potential for identifying the limited and sparse outcrops useful for field mapping geologists. Overall this study also showed the importance of the image spatial resolution in vegetated and cultivated areas with limited outcrop. Ideally a finer spatial image product than available with ASTER’s VNIR-SWIR combined products at 30 m is required.","PeriodicalId":42883,"journal":{"name":"Cogent Geoscience","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/23312041.2017.1319259","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46248040","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-01-01DOI: 10.1080/23312041.2017.1286733
Z. Dobesová
Abstract This paper describes a cartographical and Geographic Information System (GIS) work on a poster for the subtropical greenhouse. The subtropical greenhouse is part of a collection of greenhouses in Olomouc that are located in the centre of the city (Czech Republic) near Smetana Park. An overall plan exists for the collection of greenhouses and botanical gardens in the area. We have created a poster regarding the subtropical greenhouse plan. Partial plan for the subtropical greenhouse shows the detailed positions of approximately 120 plants. This plan is central information on the big presented poster (format A0). Plans arose from the cooperation of cartographers and botanists using GIS. All digital maps and plans were created using ArcGIS software after punctual measure in the field. Beside text information on the poster, there are pictures of selected plants. They are accompanied with maps of their native range. The maps of the native range are original cartographical part of the same authors. The poster also contains an old proposal for the subtropical greenhouse, which was created by a leading garden architect, I. Otruba, in 1991 before construction of the greenhouse. The book regarding species in subtropical greenhouses was issued in 2013. It contains descriptions of 33 select species. The exposition represents mainly Mediterranean flora. Each species is described with text and includes illustrations of fruits, leafs, flowers, and habitus. Maps of the native ranges of each species are an original important part of the book. Greenhouses are open to the public, and students from Palacky University participate in botany and environmental lectures there. The visitors are tended to be intrigued by the astonishing variety of subtropical plants.
{"title":"Creation of subtropical greenhouse plan for the Flora Exhibition Grounds using GIS","authors":"Z. Dobesová","doi":"10.1080/23312041.2017.1286733","DOIUrl":"https://doi.org/10.1080/23312041.2017.1286733","url":null,"abstract":"Abstract This paper describes a cartographical and Geographic Information System (GIS) work on a poster for the subtropical greenhouse. The subtropical greenhouse is part of a collection of greenhouses in Olomouc that are located in the centre of the city (Czech Republic) near Smetana Park. An overall plan exists for the collection of greenhouses and botanical gardens in the area. We have created a poster regarding the subtropical greenhouse plan. Partial plan for the subtropical greenhouse shows the detailed positions of approximately 120 plants. This plan is central information on the big presented poster (format A0). Plans arose from the cooperation of cartographers and botanists using GIS. All digital maps and plans were created using ArcGIS software after punctual measure in the field. Beside text information on the poster, there are pictures of selected plants. They are accompanied with maps of their native range. The maps of the native range are original cartographical part of the same authors. The poster also contains an old proposal for the subtropical greenhouse, which was created by a leading garden architect, I. Otruba, in 1991 before construction of the greenhouse. The book regarding species in subtropical greenhouses was issued in 2013. It contains descriptions of 33 select species. The exposition represents mainly Mediterranean flora. Each species is described with text and includes illustrations of fruits, leafs, flowers, and habitus. Maps of the native ranges of each species are an original important part of the book. Greenhouses are open to the public, and students from Palacky University participate in botany and environmental lectures there. The visitors are tended to be intrigued by the astonishing variety of subtropical plants.","PeriodicalId":42883,"journal":{"name":"Cogent Geoscience","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/23312041.2017.1286733","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43843246","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-01-01DOI: 10.1080/23312041.2017.1333667
H. Kuang, Guangchun Jin, Zhenzhong Gao
Abstract On the basis of core descriptions, examinations of rock thin sections, and EMI logging, a fluvial-dominated fan delta depositional system consisting of the fan delta plain and front subfacies from the lower Urho Formation of the Upper Permian in the Karamay oilfield of Xinjiang, NW China, was recognized in this research. The typical characteristics of this kind of fan delta is the depositional processes that were dominated by the fluvial and tractive current structure that developed very well, while pro-fan delta and gravity deposition occurred very less. The key microfacies associations in the fan delta plain subfacies are braided channel, sheeted flow, mud flow, and sieve deposits, while the fan delta front subfacies commonly contains subaqueous channels, interdistributary channels, debris flow, grain flow, and subaqueous levee microfacies. A study of image logging, grain size, and compositions of rocks indicate that provenance directions are different from the early to the last depositional periods of the Urho Formation, i.e. it changed from the southwest initially to the northwest in the latest among the fifth period to the first period. In addition, with the corresponding provenance direction changing, the sedimentary facies also transform regularly. This paper illuminated the sedimentary facies, subfacies and microfacies and also discussed deeply the depositional distribution and evolution of the lower Urho Formation. A sedimentary model of the fluvial-dominated fan delta was presented in this paper.
{"title":"Sedimentary facies and evolution of the lower Urho Formation in the 8th area of Karamay oilfield of Xinjiang, NW China","authors":"H. Kuang, Guangchun Jin, Zhenzhong Gao","doi":"10.1080/23312041.2017.1333667","DOIUrl":"https://doi.org/10.1080/23312041.2017.1333667","url":null,"abstract":"Abstract On the basis of core descriptions, examinations of rock thin sections, and EMI logging, a fluvial-dominated fan delta depositional system consisting of the fan delta plain and front subfacies from the lower Urho Formation of the Upper Permian in the Karamay oilfield of Xinjiang, NW China, was recognized in this research. The typical characteristics of this kind of fan delta is the depositional processes that were dominated by the fluvial and tractive current structure that developed very well, while pro-fan delta and gravity deposition occurred very less. The key microfacies associations in the fan delta plain subfacies are braided channel, sheeted flow, mud flow, and sieve deposits, while the fan delta front subfacies commonly contains subaqueous channels, interdistributary channels, debris flow, grain flow, and subaqueous levee microfacies. A study of image logging, grain size, and compositions of rocks indicate that provenance directions are different from the early to the last depositional periods of the Urho Formation, i.e. it changed from the southwest initially to the northwest in the latest among the fifth period to the first period. In addition, with the corresponding provenance direction changing, the sedimentary facies also transform regularly. This paper illuminated the sedimentary facies, subfacies and microfacies and also discussed deeply the depositional distribution and evolution of the lower Urho Formation. A sedimentary model of the fluvial-dominated fan delta was presented in this paper.","PeriodicalId":42883,"journal":{"name":"Cogent Geoscience","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/23312041.2017.1333667","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48604644","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-12-31DOI: 10.1080/23312041.2016.1220444
K. Rajsekhar, P. Sharma, S. Shukla
Abstract This paper describes the movement of virus in one-dimensional unsaturated porous media. The governing virus transport equations consider the inactivation in liquid phase, liquid–solid interface, air–liquid interface, and sorption in both liquid–solid and air–liquid interfaces. Finite-volume method has been used for solving the advection and dispersion processes of the virus transport equation. The effects of transport parameters on virus concentration profiles have been investigated for virus present in liquid phase, adsorbed liquid–solid and liquid–air phases. The results show that the movement of viruses in three phases is affected by soil moisture, inactivation rate, pore velocity, and mass transfer coefficients. It is found that the magnitude of virus sorption is higher at the air–liquid interface as compared to the liquid–solid interface. A higher value of mass transfer coefficient leads to an increase in the virus concentration in both liquid–solid and air–liquid interfaces.
{"title":"Numerical modeling of virus transport through unsaturated porous media","authors":"K. Rajsekhar, P. Sharma, S. Shukla","doi":"10.1080/23312041.2016.1220444","DOIUrl":"https://doi.org/10.1080/23312041.2016.1220444","url":null,"abstract":"Abstract This paper describes the movement of virus in one-dimensional unsaturated porous media. The governing virus transport equations consider the inactivation in liquid phase, liquid–solid interface, air–liquid interface, and sorption in both liquid–solid and air–liquid interfaces. Finite-volume method has been used for solving the advection and dispersion processes of the virus transport equation. The effects of transport parameters on virus concentration profiles have been investigated for virus present in liquid phase, adsorbed liquid–solid and liquid–air phases. The results show that the movement of viruses in three phases is affected by soil moisture, inactivation rate, pore velocity, and mass transfer coefficients. It is found that the magnitude of virus sorption is higher at the air–liquid interface as compared to the liquid–solid interface. A higher value of mass transfer coefficient leads to an increase in the virus concentration in both liquid–solid and air–liquid interfaces.","PeriodicalId":42883,"journal":{"name":"Cogent Geoscience","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/23312041.2016.1220444","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60091751","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-09-12DOI: 10.1080/23312041.2016.1223899
A. Afifi, A. El-Rabbany
Abstract This paper introduces a dual-frequency precise point positioning (PPP) model, which combines the observations of three different global navigation satellite system (GNSS) constellations, namely GPS, Galileo, and BeiDou. A drawback of a single GNSS system such as GPS, however, is the availability of sufficient number of visible satellites in urban areas. Combining GNSS observations offers more visible satellites to users, which in turn is expected to enhance the satellite geometry and the overall positioning solution. However, combining several GNSS observables introduces additional biases, which require rigorous modeling, including the GNSS time offsets and hardware delays. In this paper, un-differenced ionosphere-free linear combination PPP model is developed. The additional biases of the GPS, Galileo, and BeiDou combination are accounted for through the introduction of a new unknown parameter, which is identified as the inter-system bias, in the PPP mathematical model. Natural Resources Canada’s GPSPace PPP software is modified to enable a combined GPS, Galileo, and BeiDou PPP solution and to handle the newly introduced biases. A total of four data-sets collected at four different IGS stations are processed to verify the developed PPP model. Precise satellite orbit and clock products from the International GNSS Service Multi-GNSS Experiment (IGS-MGEX) network are used to correct the GPS, Galileo, and BeiDou measurements. It is shown that the un-differenced GPS-only post-processed PPP solution indicates that the model is capable of obtaining a sub-decimeter-level accuracy. However, the solution takes about 20 min to converge to decimeter-level precision. The convergence time of the combined GNSS post-processed PPP solutions takes about 15 min to reach the decimeter-level precision, which represent a 25% improvement in comparison with the GPS-only post-processed PPP solution.
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