Gas compressibility factor (z-Factor) is one of the most important parameters in upstream and downstream calculations of petroleum industries.The importance of z-Factor cannot be overemphasized in oil and gas engine...Gas compressibility factor (z-Factor) is one of the most important parameters in upstream and downstream calculations of petroleum industries.The importance of z-Factor cannot be overemphasized in oil and gas engineering calculations.The experimental measurements,Equations of State (EoS) and empirical correlations are the most common sources of z-Factor calculations.There are more than twenty correlations available with two variables for calculating the z-Factor from fitting in an EoS or just through fitting techniques.However,these correlations are too complex,which require initial value and more complicated and longer computations or have magnitude error.The purpose of this study is to develop a new accurate correlation to rapidly estimate z-Factor.Result of this correlation is compared with large scale of database and experimental data also.Proposed correlation has 1.660 of Absolute Percent Relative Error (EABS) versus Standing and Katz chart and has also 3.221 of EABS versus experimental data.The output of this correlation can be directly assumed or be used as an initial value of other implicit correlations.This correlation is valid for gas coefficient of isothermal compressibility (cg) calculations also.展开更多
In Europe, very small forest areas can be considered to be old-growth, and they are mainly located in Eastern Europe. The typical structures of old growth forests infrequently occur in Mediterranean mountainous enviro...In Europe, very small forest areas can be considered to be old-growth, and they are mainly located in Eastern Europe. The typical structures of old growth forests infrequently occur in Mediterranean mountainous environments, since they have been affected by human activities for centuries. This study focused on a remote and almost pure Italian maple stand located in southern Italy, which has not been managed for long time due to its inaccessibility. The effects of natural evolution on the forest stand were evaluated through the analysis of the spatial and chronological structure and the regeneration patterns, then estimating the amounts and quality of deadwood occurrence. Across the whole stand, all the trees with DBH(diameter at breast height) larger than 50 cm(LLT, large living trees) were measured(DBH and height) and age was also determined through a dendrochronological approach. The diameters observed ranged between 50 and 145 cm with ages of 120 to 250 years. The Latham index calculated for trees within the sample plot highlighted a multilayered canopy with a dominant layer of largeliving trees(age > 120 years). The size-class distribution of stems had a reverse-J shape, and basal area was 52 m^2 ha^(-1). Deadwood was exclusively constituted by standing dead trees and CWD and its volume was on average 31 m^3 ha^(-1). Pure Italian maple forests are generally rare in Europe, and it was unexpected to find a forest stand characterized by a so complex structure with old growth attributes. The study of complex forest stand, even if small, could give precious information on the forest evolution, clarifying also diverse auto-ecological traits of tree species that usually are not common in our forests.展开更多
The history of the Black Mountains in North Carolina and the southern Spruce-Fir ecosystem has been fraught with widespread forest decline since the mid 1960’s. Balsam Woolly Adelgid attacks and acidic deposition wer...The history of the Black Mountains in North Carolina and the southern Spruce-Fir ecosystem has been fraught with widespread forest decline since the mid 1960’s. Balsam Woolly Adelgid attacks and acidic deposition were two of the most recognized causes of decline. Uncertainty arose about the future of these forests, and projections were made regarding the endangerment or extinction of the endemic Fraser fir ([Pursh] Poiret). This study analyzed data sets from a permanent plot network in the Black Mountains dating 1985, 2002, and 2012. Indications that the Fraser fir population is stabilizing from a “boom-bust” cycle of population growth and has entered the stem exclusion stage of forest stand development are evident. Fir live stem density increased more than 250% from 1985 to 2002, and then declined 40% by 2012 at the highest elevations in the forest. Overall, fir appeared to be more impacted on western facing slopes than eastern ones. The population of red spruce experienced a steady decrease in live stem counts, but an increase in live basal area through all years, and at all elevation classes (1675 m, 1830 m, and 1980 m), indicating a normal progression through stand development. Red spruce was also most negatively impacted on western facing slopes. Live stem density was significantly higher (P 0.001) than eastern plots, but live basal area was similar between the two aspects. Atmospheric deposition concentrations of the four main acidic molecules at Mt. Mitchell all peaked in 1998, but decreased by 2012. These reductions, occurring shortly after tightened regulations in the 1990 amendments to the Clean Air Act may have potential implications for increased forest resilience.展开更多
Background:Carbon(C),nitrogen(N),and phosphorus(P)stoichiometry is a key indicator of nutrient utilization in plants,and C/N/P ratios are related to the life histories and adaptation strategies of tree species.However...Background:Carbon(C),nitrogen(N),and phosphorus(P)stoichiometry is a key indicator of nutrient utilization in plants,and C/N/P ratios are related to the life histories and adaptation strategies of tree species.However,no consensus has been reached on how leaf stoichiometric characteristics are affected by forest type and stand ages.The relationships between leaf stoichiometry and geographical,meteorological,and soil factors also remain poorly understood.Methods:Leaf and soil were sampled from forest stands of different age groups(young,middle-aged,near-mature,and mature)in two forest types(Chinese fir(Cunninghamia lanceolata)forests and evergreen broadleaved forests).The relationships between leaf C,N,and P stoichiometric parameters and geographical,meteorological,and soil factors were analysed by using redundancy analysis(RDA)and stepwise linear regression analysis.Results:Leaf C concentrations peaked in the near-mature stands with increasing age irrespective of forest type.Leaf N and P concentrations fluctuated with a rising trend in Chinese fir forests,while decreased first and increased later from young to mature phases in natural evergreen broadleaved forests.Chinese fir forests were primarily limited by N and P,while natural evergreen broadleaved forests were more susceptible to P limitation.Leaf C,N,and P stoichiometric characteristics in Chinese fir forests were mainly affected by the soil total P concentration(SP),longitude(LNG),growing season precipitation(GSP)and mean temperature in July(JUT).The leaf C concentration was mainly affected by GSP and JUT;leaf N and P concentrations were both positively correlated with LNG;and leaf P was positively correlated with SP.In evergreen broadleaved forests,however,leaf stoichiometric parameters displayed significant correlations with latitude(LAT)and mean annual precipitation(MAP).Conclusions:Leaf stoichiometry differed among forest stands of different age groups and forest types.Leaf C,N,and P stoichiometry was primarily explained by the combinations of SP,LNG,GSP and JUT in Chinese fir forests.LAT and MAP were the main controlling factors affecting the variations in the leaf C,N,and P status in natural evergreen broadleaved forests,which supports the temperature-plant physiological hypothesis.These findings improve the understanding of the distribution patterns and driving mechanisms of leaf stoichiometry linked with stand age and forest type.展开更多
Scientists have debated for many years about the nature of time.Why does time seem to flow the past to the future? why does it never flow in the opposite direction-from the
Natural spruce-fir mixed stand is one of the main forest types in the world,and also has huge ecological,economic and social benefits.According to the structural characteristics and succession laws of natural spruce-f...Natural spruce-fir mixed stand is one of the main forest types in the world,and also has huge ecological,economic and social benefits.According to the structural characteristics and succession laws of natural spruce-fir forest,it is urgent and significant to develop scientific management measures for natural spruce-fir mixed stand in line with local conditions.The article outlined the characteristics of the distribution and structure, regeneration and succession laws of natural spruce-fir forest,and analyzed the current situation and existing problems of natural spruce-fir forest management.The following recommendations were eventually made:1) In no cutting area,all logging activities should be banned.In a restricted cutting area,the cutting intensity should be generally controlled within 15%of the stock volume before cutting.On the commodity forest management area, the appropriate cutting intensity should be determined according to the volume per hectare,determine and classification management should be implemented in accordance with the characteristics of forest,to ensure the scientific selective cutting.2) Closure for afforestation,planting and repair planting should be adopted on vegetation-intensive land,sparse shrubs covered land and harvesting slash,in order to accelerate natural regeneration.3) The in situ conservation should be conducted in nature reserves and scientific experiment stations of rare and endangered species,such as Abies chensiensis,Picea neoveitchii,Abies vuanbaoshanensis,to reduce human destruction.4) It is supposed to collect seeds in time,establish nursery,actively establish forest, expand artificial population and promote natural regeneration.展开更多
基金supported by Research Institute of Petroleum Industry-Kermanshah Campus
文摘Gas compressibility factor (z-Factor) is one of the most important parameters in upstream and downstream calculations of petroleum industries.The importance of z-Factor cannot be overemphasized in oil and gas engineering calculations.The experimental measurements,Equations of State (EoS) and empirical correlations are the most common sources of z-Factor calculations.There are more than twenty correlations available with two variables for calculating the z-Factor from fitting in an EoS or just through fitting techniques.However,these correlations are too complex,which require initial value and more complicated and longer computations or have magnitude error.The purpose of this study is to develop a new accurate correlation to rapidly estimate z-Factor.Result of this correlation is compared with large scale of database and experimental data also.Proposed correlation has 1.660 of Absolute Percent Relative Error (EABS) versus Standing and Katz chart and has also 3.221 of EABS versus experimental data.The output of this correlation can be directly assumed or be used as an initial value of other implicit correlations.This correlation is valid for gas coefficient of isothermal compressibility (cg) calculations also.
基金partially developed within the scope of research project LIFE+2013 "PAN LIFE Project-Natura 2000 Action Programme.Life+Nature-2013-LIFE13 NAT/IT/001075
文摘In Europe, very small forest areas can be considered to be old-growth, and they are mainly located in Eastern Europe. The typical structures of old growth forests infrequently occur in Mediterranean mountainous environments, since they have been affected by human activities for centuries. This study focused on a remote and almost pure Italian maple stand located in southern Italy, which has not been managed for long time due to its inaccessibility. The effects of natural evolution on the forest stand were evaluated through the analysis of the spatial and chronological structure and the regeneration patterns, then estimating the amounts and quality of deadwood occurrence. Across the whole stand, all the trees with DBH(diameter at breast height) larger than 50 cm(LLT, large living trees) were measured(DBH and height) and age was also determined through a dendrochronological approach. The diameters observed ranged between 50 and 145 cm with ages of 120 to 250 years. The Latham index calculated for trees within the sample plot highlighted a multilayered canopy with a dominant layer of largeliving trees(age > 120 years). The size-class distribution of stems had a reverse-J shape, and basal area was 52 m^2 ha^(-1). Deadwood was exclusively constituted by standing dead trees and CWD and its volume was on average 31 m^3 ha^(-1). Pure Italian maple forests are generally rare in Europe, and it was unexpected to find a forest stand characterized by a so complex structure with old growth attributes. The study of complex forest stand, even if small, could give precious information on the forest evolution, clarifying also diverse auto-ecological traits of tree species that usually are not common in our forests.
文摘The history of the Black Mountains in North Carolina and the southern Spruce-Fir ecosystem has been fraught with widespread forest decline since the mid 1960’s. Balsam Woolly Adelgid attacks and acidic deposition were two of the most recognized causes of decline. Uncertainty arose about the future of these forests, and projections were made regarding the endangerment or extinction of the endemic Fraser fir ([Pursh] Poiret). This study analyzed data sets from a permanent plot network in the Black Mountains dating 1985, 2002, and 2012. Indications that the Fraser fir population is stabilizing from a “boom-bust” cycle of population growth and has entered the stem exclusion stage of forest stand development are evident. Fir live stem density increased more than 250% from 1985 to 2002, and then declined 40% by 2012 at the highest elevations in the forest. Overall, fir appeared to be more impacted on western facing slopes than eastern ones. The population of red spruce experienced a steady decrease in live stem counts, but an increase in live basal area through all years, and at all elevation classes (1675 m, 1830 m, and 1980 m), indicating a normal progression through stand development. Red spruce was also most negatively impacted on western facing slopes. Live stem density was significantly higher (P 0.001) than eastern plots, but live basal area was similar between the two aspects. Atmospheric deposition concentrations of the four main acidic molecules at Mt. Mitchell all peaked in 1998, but decreased by 2012. These reductions, occurring shortly after tightened regulations in the 1990 amendments to the Clean Air Act may have potential implications for increased forest resilience.
基金supported by the National Natural Science Foundation of China(No.31971643)the Industry-University Cooperation Project of Fujian Science and Technology Department(Nos.2020N5008,2019N5009)+2 种基金the General program of Natural Science Foundation of Fujian Province of China(No.2018J01737)Special Funding Project of Fujian Provincial Department of Finance(SC-299)Minjiang Scholar Programme.
文摘Background:Carbon(C),nitrogen(N),and phosphorus(P)stoichiometry is a key indicator of nutrient utilization in plants,and C/N/P ratios are related to the life histories and adaptation strategies of tree species.However,no consensus has been reached on how leaf stoichiometric characteristics are affected by forest type and stand ages.The relationships between leaf stoichiometry and geographical,meteorological,and soil factors also remain poorly understood.Methods:Leaf and soil were sampled from forest stands of different age groups(young,middle-aged,near-mature,and mature)in two forest types(Chinese fir(Cunninghamia lanceolata)forests and evergreen broadleaved forests).The relationships between leaf C,N,and P stoichiometric parameters and geographical,meteorological,and soil factors were analysed by using redundancy analysis(RDA)and stepwise linear regression analysis.Results:Leaf C concentrations peaked in the near-mature stands with increasing age irrespective of forest type.Leaf N and P concentrations fluctuated with a rising trend in Chinese fir forests,while decreased first and increased later from young to mature phases in natural evergreen broadleaved forests.Chinese fir forests were primarily limited by N and P,while natural evergreen broadleaved forests were more susceptible to P limitation.Leaf C,N,and P stoichiometric characteristics in Chinese fir forests were mainly affected by the soil total P concentration(SP),longitude(LNG),growing season precipitation(GSP)and mean temperature in July(JUT).The leaf C concentration was mainly affected by GSP and JUT;leaf N and P concentrations were both positively correlated with LNG;and leaf P was positively correlated with SP.In evergreen broadleaved forests,however,leaf stoichiometric parameters displayed significant correlations with latitude(LAT)and mean annual precipitation(MAP).Conclusions:Leaf stoichiometry differed among forest stands of different age groups and forest types.Leaf C,N,and P stoichiometry was primarily explained by the combinations of SP,LNG,GSP and JUT in Chinese fir forests.LAT and MAP were the main controlling factors affecting the variations in the leaf C,N,and P status in natural evergreen broadleaved forests,which supports the temperature-plant physiological hypothesis.These findings improve the understanding of the distribution patterns and driving mechanisms of leaf stoichiometry linked with stand age and forest type.
文摘Scientists have debated for many years about the nature of time.Why does time seem to flow the past to the future? why does it never flow in the opposite direction-from the
文摘Natural spruce-fir mixed stand is one of the main forest types in the world,and also has huge ecological,economic and social benefits.According to the structural characteristics and succession laws of natural spruce-fir forest,it is urgent and significant to develop scientific management measures for natural spruce-fir mixed stand in line with local conditions.The article outlined the characteristics of the distribution and structure, regeneration and succession laws of natural spruce-fir forest,and analyzed the current situation and existing problems of natural spruce-fir forest management.The following recommendations were eventually made:1) In no cutting area,all logging activities should be banned.In a restricted cutting area,the cutting intensity should be generally controlled within 15%of the stock volume before cutting.On the commodity forest management area, the appropriate cutting intensity should be determined according to the volume per hectare,determine and classification management should be implemented in accordance with the characteristics of forest,to ensure the scientific selective cutting.2) Closure for afforestation,planting and repair planting should be adopted on vegetation-intensive land,sparse shrubs covered land and harvesting slash,in order to accelerate natural regeneration.3) The in situ conservation should be conducted in nature reserves and scientific experiment stations of rare and endangered species,such as Abies chensiensis,Picea neoveitchii,Abies vuanbaoshanensis,to reduce human destruction.4) It is supposed to collect seeds in time,establish nursery,actively establish forest, expand artificial population and promote natural regeneration.