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Artykuły w czasopismach na temat "Upper forest limit"
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Ohsawa, M., P. H. J. Nainggolan, N. Tanaka i C. Anwar. "Altitudinal zonation of forest vegetation on Mount Kerinci, Sumatra: with comparisons to zonation in the temperate region of east Asia". Journal of Tropical Ecology 1, nr 3 (sierpień 1985): 193–216. http://dx.doi.org/10.1017/s0266467400000286.
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ABSTRACTThe altitudinal zonation of forests on Mount Kerinci, Sumatra (3800 m) is described and compared with that in the temperate region of east Asia. Nine plots were selected between 1750 m in altitude and the upper limit of vegetation at 3250 m, at intervals of about 200 m in altitude. The plots are distinguished according to their main dominants, and the population structure of the dominant species is examined. The lower forests have species showing the whole range of size classes as well as solitary giants as dominants, but the upper forests lack these giants and are floristically poorer. Between 1750 m (the start of well preserved natural vegetation) and 2950 m (the forest limit) three forest zones are distinguished, and between 2950 and 3250 m a scrub zone. Upper forest zones tend to be dominated by species of the same genus or family which form important understory components of the zone below. Based on floristic comparisons with mountains of higher latitudes (i.e. Himalayas and Japan), the two lower forest zones (up to 2400 m) represent a subtropical zone, and the upper forest zone a warm-temperate zone. Climatic conditions at the forest limit on Mount Kerinci are similar to those at the latitudinal limit of warm-temperate evergreen trees; in the Himalayas the forest limit represents the latitudinal limit of the cool-temperate, and in Japan of the subarctic Altitudinal zonation patterns change with latitude, reaching their most complex on subtropical mountains where the two floristic realms, the Boreal and Palaeotropical, meet. A scheme for the pattern of vegetation zonation in east Asia is proposed.
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Wang, Jing, Baiping Zhang i Yonghui Yao. "The Spatial Pattern of the Upper Limit of Montane Deciduous Broad-Leaved Forests and Its Geographical Interpretation in the East Monsoon Realm of China". Forests 12, nr 9 (9.09.2021): 1225. http://dx.doi.org/10.3390/f12091225.
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Montane deciduous broad-leaved forests (MDB) are mainly distributed in the east monsoon realm of China. The upper limit of MDB significantly varies from mountain to mountain. However, the spatial pattern of the upper limit of MDB and its underlying drivers are still unknown. In this study, we conducted hierarchical multiple regression to quantify the effect of climatic factors, peak elevation, and cold tolerance of dominant species on the geographical distribution of the upper limit of MDB on 75 mountains in the east monsoon realm of China. The results show that: (1) the upper limit of MDB in the east monsoon realm of China, 2800 m, is the highest in Taibai peak of the Qinling mountain ranges, from where it tends to decrease both northward and southward. (2) The upper limit of MDB on the mountains with climatic treeline is mainly affected by climatic factors, the minimum temperature of the coldest month (MinT), and the precipitation seasonality (PS), with an R2 of 0.733. (3) The upper limit of MDB on both temperate and subtropical mountains without climatic treeline is affected by MinT, PS, peak elevation, and cold tolerance of dominant species together, with an R2 of 0.793 and 0.748, respectively. (4) The dominant species of the upper limit of MDB significantly differ temperate and subtropical ranges, the former of which is mainly in the genus Betula, and the latter of which is in the genus Quercus. The upper limit of MDB with the genus Fagus as dominant species is only distributed in the mountains towards the south of the Qinling mountain ranges. (5) The warmth index (WI) at the upper limit of deciduous broad-leaved forest on the mountains with climatic treeline is about 60 °C month, which is lower than that at the northernmost boundary of the latitudinal distributed deciduous broad-leaved forest (90 °C month). Our study revealed the spatial pattern and geographical drivers of the upper limit of MDB, improved our understanding of differences in MDB vegetation among different mountain ranges, and provided climatic correlates for predicting the dynamics of the upper limit of MDB under climate change.
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Kenney, W. A. "Leaf Area Density as an urban forestry planning and management tool". Forestry Chronicle 76, nr 2 (1.04.2000): 235–39. http://dx.doi.org/10.5558/tfc76235-2.
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Many of the benefits that we derive from urban forests are directly or indirectly related to the leaf area of the forest. If we are to consider these multiple benefits at the level of the forest, the use of Leaf Area Density (LAD) provides some advantages over other often used measures. Since many factors in the urban landscape can limit leaf area, Potential Leaf Area Density (PLAD) can provide a measure of the upper limit to leaf area density. Using these two measures, urban forest planners and managers can integrate many of the issues associated with broader aspects of the structure and benefits of the forest under their jurisdiction. Some planning, policy, and educational applications of LAD and PLAD are discussed. Key words: urban forestry management and planning, leaf area density
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Klinge, M., J. Böhner i S. Erasmi. "Modeling forest lines and forest distribution patterns with remote-sensing data in a mountainous region of semiarid central Asia". Biogeosciences 12, nr 10 (20.05.2015): 2893–905. http://dx.doi.org/10.5194/bg-12-2893-2015.
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Abstract. Satellite images and digital elevation models provide an excellent database to analyze forest distribution patterns and forest limits in the mountain regions of semiarid central Asia on the regional scale. For the investigation area in the northern Tien Shan, a strong relationship between forest distribution and climate conditions could be found. Additionally areas of potential human impact on forested areas are identified at lower elevations near the edge of the mountains based on an analysis of the differences in climatic preconditions and the present occurrence of forest stands. The distribution of spruce (Picea schrenkiana) forests is hydrologically limited by a minimum annual precipitation of 250 mm and thermally by a minimum monthly mean temperature of 5 °C during the growing season. While the actual lower forest limit increases from 1600 m a.s.l. (above sea level) in the northwest to 2600 m a.s.l. in the southeast, the upper forest limit rises in the same direction from 1800 m a.s.l. to 2900 m a.s.l.. In accordance with the main wind directions, the steepest gradient of both forest lines and the greatest local vertical extent of the forest belt of 500 to 600 m to a maximum of 900 m occur at the northern and western mountain fronts. The forests in the investigation area are strongly restricted to north-facing slopes, which is a common feature in semiarid central Asia. Based on the presumption that variations in local climate conditions are a function of topography, the potential forest extent was analyzed with regard to the parameters slope, aspect, solar radiation input and elevation. All four parameters showed a strong relationship to forest distribution, yielding a total potential forest area that is 3.5 times larger than the present forest remains of 502 km2.
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Klinge, M., J. Böhner i S. Erasmi. "Modelling forest lines and forest distribution patterns with remote sensing data in a mountainous region of semi-arid Central Asia". Biogeosciences Discussions 11, nr 10 (13.10.2014): 14667–98. http://dx.doi.org/10.5194/bgd-11-14667-2014.
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Abstract. Satellite images and digital elevation models provide an excellent database to analyse forest distribution patterns and forest limits in the mountain regions of semi-arid Central Asia at the regional scale. For the investigation area in the northern Tien Shan a strong relation between forest distribution and climate conditions could be found. Additionally areas of potential human impact on forested areas are identified at lower elevations near the mountain border based on an analysis of the differences of climatic preconditions and present occurrence of forest stands. The distribution of spruce (Picea schrenkiana) forests is hydrologically limited by a minimum annual precipitation of 250 mm and thermally by a minimum monthly mean temperature of 5 °C during the growing season. While the actual lower forest limit increases from 1600 m a.s.l. in the northwest to 2600 m a.s.l. in the southeast, the upper forest limit takes the same course from 1800 to 2900 m a.s.l. In accordance with the main wind directions, the steepest gradient of both forest lines and the greatest local vertical extent of the forest belt of 500 to 600 m and maximum 900 m occur at the northern and western mountain fronts. The forests in the investigation area are strongly restricted to north facing-slopes, which is a common feature in semi-arid Central Asia. Based on the presumption that variations in local climate conditions are a function of topography, the potential forest extent was analysed with regard to the parameters slope, aspect, solar radiation input and elevation. All four parameters showed a strong relationship to forest distribution, yielding a total potential forest area that is 3.5 times larger than the present forest remains of 502 km2.
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Minďaš, Jozef, i Jana Škvareninová. "Biodiversity and climate change: consequences for upper tree line in Slovakia". Forestry Journal 62, nr 3 (1.09.2016): 181–85. http://dx.doi.org/10.1515/forj-2016-0022.
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Abstract Study of the effects of climate change on upper tree limit has mainly focused on the diversity of tree species as a result of the ability of species to tolerate temperature and moisture changes as well as some effects of disturbance regime changes. The tree species diversity changes due to climate change has been analysed via gap model and biodiversity indices. Gap models are individually based on simulations of establishment, growth, and mortality of each tree on the forest plot. Input ecological data for model calculations have been taken from the permanent research plots located in primeval forests in mountainous regions in Slovakia. The results of regional scenarios of the climatic change for the territory of Slovakia have been used, from which the values according to the CGCM3.1 (global) model, KNMI and MPI (regional) models. Model results for conditions of the climate change scenarios suggest a shift of the upper forest limit to the region of the present subalpine zone, in supramontane zone. The most significant tree species diversity changes have been identified for the upper tree line and current belt of dwarf pine (Pinus mugo) occurrence. Hill’s index of biodiversity in the upper forest line increased by 30 – 35% for horizon of 2050, resp. by 45 – 50% modeled for the horizon of 2075. Calculated values of Shannon’s index show an even higher increase due to climate change. For horizon 2050 is a roughly of three fold increase and horizon for 2075 by almost fivefold increase in the value of the index. Results from the gap model indicate the increase of tree species diversity 2 – 2,5 times.
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Markgraf, Vera. "Paleoenvironmental Changes at the Northern Limit of the Subantarctic Nothofagus Forest, lat 37°S, Argentina". Quaternary Research 28, nr 1 (lipiec 1987): 119–29. http://dx.doi.org/10.1016/0033-5894(87)90037-8.
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AbstractPaleoenvironmental changes dating back to before 10,000 yr B.P. at the northernmost occurrences of Nothofagus forests in Argentina at about latitude 37°S permit the reconstruction of past changes in the intensity of the winter rains, related to the southern westerlies that appear to determine the forest boundary. The paleoenvironmental interpretation is based on changes in the proportions of different Nothofagus species and changes in the ratio betwen forest and steppe taxa. The relatively most diverse and dense Nothofagus forest developed only during the last 4500 yr, prior to human impact during the last 300 yr. Before the middle Holocene, climatic conditions must have been different from the modern ones, with less overall precipitation judging from the overall lower amount of tree pollen and the reduction to primarily Nothfagus pumilio. An interval dated to older than 10,000 yr B.P. is characterized by co-occurrence of Prumnopitys andina, Nothofagus pumilio, and shrub-steppe taxa. Prumnopitys andina is known today only from scattered upper montane forest sites in Chile between 36° and 43°S lat and its ecological requirements are essentially unknown. The taxa combination, however, suggests that late-glacial climate must have been drier, and probably cooler than today. This implies that the winter rains and, consequently, the seasonal shift of the westerly circulation was reduced during the late Pleistocene and did not reach modern levels before 8500 yr B.P.
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Novotný, R., D. Černý i V. Šrámek. "Nutrition of silver fir (Abies alba Mill) growing at the upper limit of its occurrence in the Šumava National Park and Protected Landscape Area". Journal of Forest Science 56, No. 9 (30.09.2010): 381–88. http://dx.doi.org/10.17221/87/2009-jfs.
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In the second half of 20<sup>th</sup> century silver fir regeneration has been observed throughout all of the Europe, including the Czech Republic. The Bohemian Forest – Šumava Mts. is one of the regions where the silver fir percentage in forest stands is supposed to be increased from the present 2% to nearly 12%. During the period 2006–2007, in the Czech part of the Bohemian Forest, samples of silver fir were taken mainly in the upper altitudinal limit of silver fir occurrence. In the present paper the results of performed analyses are compared with similar surveys conducted in the other European regions. Samples from the Bohemian Forest, in contrast to other results, differ in higher phosphorus content and lower contents of calcium and manganese. Nitrogen content is slightly higher. Our values for the other elements (magnesium, potassium, zinc, sulphur) are comparable to those reported in Poland and Slovakia. In Germany, aside from the above mentioned differences, higher magnesium content was also found within the locality sampled.
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Silva, Lucas C. R., Geng Sun, Xia Zhu-Barker, Qianlong Liang, Ning Wu i William R. Horwath. "Tree growth acceleration and expansion of alpine forests: The synergistic effect of atmospheric and edaphic change". Science Advances 2, nr 8 (sierpień 2016): e1501302. http://dx.doi.org/10.1126/sciadv.1501302.
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Many forest ecosystems have experienced recent declines in productivity; however, in some alpine regions, tree growth and forest expansion are increasing at marked rates. Dendrochronological analyses at the upper limit of alpine forests in the Tibetan Plateau show a steady increase in tree growth since the early 1900s, which intensified during the 1930s and 1960s, and have reached unprecedented levels since 1760. This recent growth acceleration was observed in small/young and large/old trees and coincided with the establishment of trees outside the forest range, reflecting a connection between the physiological performance of dominant species and shifts in forest distribution. Measurements of stable isotopes (carbon, oxygen, and nitrogen) in tree rings indicate that tree growth has been stimulated by the synergistic effect of rising atmospheric CO2and a warming-induced increase in water and nutrient availability from thawing permafrost. These findings illustrate the importance of considering soil-plant-atmosphere interactions to understand current and anticipate future changes in productivity and distribution of forest ecosystems.
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Moravčík, M. "Derivation of target stocking for forests of Norway spruce vegetation zone in Slovakia". Journal of Forest Science 53, No. 8 (7.01.2008): 352–58. http://dx.doi.org/10.17221/2183-jfs.
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The present paper deals with derivation of target stocking in forests of Norway spruce vegetation zone. Target stocking in forests with prevailing ecological and social functions is the stocking when the forest fulfils demanded functions in the best way. For forests in the Norway spruce vegetation zone target stocking was derived by original procedures as an optimum stocking in harmonization of demands on the fulfilment of ecological functions (especially erosion control, hydrological and water protection ones), securing static stability and preconditions for the formation and growth of natural regeneration. We investigated the relations between stocking and indicators of static stability (slenderness coefficient and ratio of crown length to tree height), natural regeneration phases, ground and non-wood vegetation coverage and natural regeneration coverage. The most favourable status of these indicators was found out in stocking 0.7 and in the upper forest limit 0.6.
Rozprawy doktorskie na temat "Upper forest limit"
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Birre, Deborah. "Dynamique spatio-temporelle de la limite supérieure de la forêt dans la partie orientale des Pyrénées françaises : le rôle de l’anthropisation et des changements climatiques". Electronic Thesis or Diss., Paris 13, 2024. https://theses.hal.science/tel-04651374.
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La position de la limite supérieure forestière marquant la transition entre la forêt et la pelouse alpine en montagne est théoriquement régie par les températures. Cependant, sa réponse au réchauffement climatique actuel est complexe et non uniforme. Les conséquences de cette dynamique soulèvent des enjeux écologiques et socio-économiques importants. Cette thèse se concentre sur la partie orientale des Pyrénées pour démêler les interactions entre les facteurs potentiels et la dynamique de la limite supérieure forestière. L’hypothèse centrale de la thèse est que la hiérarchie des facteurs influençant la dynamique, qu’ils soient d’origine climatique ou anthropique, varie en fonction de l’échelle d'analyse. Pour tester cette hypothèse, une méthodologie combinant la géomatique via une cartographie diachronique à l’échelle de l’ensemble de la zone étudiée, des analyses statistiques régionales des facteurs potentiels, et des analyses locales via des relevés naturalistes sur le terrain, a été employée. Quatre résultats majeurs ont émergé de ces analyses : (i) l’abaissement altitudinal de la limite forestière par rapport à son altitude théorique ; (ii) la complémentarité des indicateurs de la dynamique au-delà du seul changement d’altitude ; (iii) la multidimensionnalité de la dynamique selon l’indicateur et l’échelle considérée et (iv) la multiscalarité de la dynamique où les contextes locaux influent de manière variable. Ces résultats confirment l’hypothèse centrale de la thèse et relativisent les effets du climat aux échelles régionales et localesThe position of the upper forest limit, which delineates the transition between forested areas and alpine grasslands in mountainous regions, is theoretically determined by temperatures. However, its response to current climate warming is intricate and heterogeneous, carrying significant ecological and socio-economic implications. This thesis focuses on the Eastern Pyrenees to unravel the interactions between various potential factors and the dynamics of the upper forest limit. The central hypothesis suggests that the hierarchy of influencing factors, whether climatic or anthropogenic, varies depending on the scale of analysis. To test this hypothesis, a methodology combining geomatics for diachronic mapping at the scale of the entire study area, regional statistical analyses of potential factors, and local field surveys has been employed. Four major results have emerged from these analyses : (i) the lowering of the forest limit altitude compared to its theoretical altitude; (ii) the complementary nature of dynamic indicators beyond mere altitude changes; (iii) the multidimensionality of the dynamic depending on the indicator and scale considered; and (iv) the multiscale nature of the dynamic, where local contexts variably influence outcomes. These findings confirm the central hypothesis of the thesis and shed light on the relative effects of climate at regional and local scales
Książki na temat "Upper forest limit"
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Wieser, Gerhard, i Michael Tausz. Trees at Their Upper Limit: Treelife Limitation at the Alpine Timberline. Springer, 2010.
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Wieser, Gerhard, i Michael Tausz. Trees at Their Upper Limit: Treelife Limitation at the Alpine Timberline. Springer London, Limited, 2007.
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(Editor), Gerhard Wieser, i Michael Tausz (Editor), red. Trees at their Upper Limit: Treelife Limitation at the Alpine Timberline (Plant Ecophysiology). Springer, 2006.
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Szewczyk, Janusz. Rola zaburzeń w kształtowaniu struktury i dynamiki naturalnych lasów bukowo-jodłowo-świerkowych w Karpatach Zachodnich. Publishing House of the University of Agriculture in Krakow, 2018. http://dx.doi.org/10.15576/978-83-66602-35-9.
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The aim of the study was to determine the influence of different disturbances (both natural and anthropogenic) on species composition and stand structure of old-growth mixed mountain forests in the Western Carpathians. These stands are usually dominated by beech, fir and spruce, mixed in different proportions. The tree main species represent different growth strategies, and they compete against each other. The longevity of trees makes the factors influencing the stand structure difficult to identify, even during longitudinal studies conducted on permanent research plots. That is why dendroecological techniques, based upon the annual variability of tree rings, are commonly used to analyze the disturbance histories of old-growth stands. Dendroecological methods make it possible to reconstruct the stand history over several centuries in the past by analyzing the frequency, intensity, duration and spatial scale of disturbances causing the death of trees. Combining the dendroecological techniques with the detailed measurements of stand structure, snag volume, CWD volume, and the analyses of regeneration species composition and structure allows us to identify the factors responsible for the changes in dynamics of mixed mountain forests. Various disturbance agents affect some species selectively, while some disturbances promote the establishment of tree seedlings of specific species by modifying environmental conditions. Describing the disturbance regime requires a broad scope of data on stand structure, on dead wood and tree regeneration, while various factors affecting all the stages of tree growth should be taken into consideration. On the basis of the already published data from permanent sample plots, combined with the available disturbance history analyses from the Western Carpathians, three research hypotheses were formulated. 1. The species composition of mixed mountain forests has been changing for at least several decades. These directional changes are the consequence of simultaneous conifer species decline and expansion of beech. 2. The observed changes in species composition of mixed mountain forests are the effect of indirect anthropogenic influences, significantly changing tree growth conditions also in the forests that are usually considered natural or near-natural. Cumulative impact of these indirect influences leads to the decrease of fir share in the tree layer (spruce decline has also been observed recently),and it limits the representation of this species among seedlings and saplings. The final effect is the decrease of fir and spruce share in the forest stands. 3. Small disturbances, killing single trees or small groups of trees, and infrequent disturbances of medium size and intensity dominate the disturbance regime in mixed mountain forests. The present structure of beech-fir-spruce forests is shaped both by complex disturbance regime and indirect anthropogenic influences. The data were gathered in permanent sample plots in strictly protected areas of Babia Góra, Gorce, and Tatra National Parks, situated in the Western Carpathians. All plots were located in the old-growth forest stands representing Carpathian beech forest community. The results of the measurements of trees, snags, coarse woody debris (CWD) and tree regeneration were used for detailed description of changes in the species composition and structure of tree stands. Tree ring widths derived from increment cores were used to reconstruct the historical changes in tree growth trends of all main tree species, as well as the stand disturbance history within the past two to three hundred years. The analyses revealed complex disturbance history in all of the three forest stands. Intermediate disturbances of variable intensity occurred, frequently separated by the periods of low tree mortality lasting from several decades up to over one hundred years. The intervals between the disturbances were significantly shorter than the expected length of forest developmental cycle, in commonly used theories describing the dynamics of old-growth stands. During intermediate disturbances up to several dozen percent of canopy trees were killed. There were no signs of stand-replacing disturbances, killing all or nearly all of canopy trees. The periods of intense tree mortality were followed by subsequent periods of increased sapling recruitment. Variability in disturbance intensity is one of the mechanisms promoting the coexistence of beech and conifer species in mixed forests. The recruitment of conifer saplings depended on the presence of larger gaps, resulting from intermediate disturbances, while beech was more successful in the periods of low mortality. However, in the last few decades, beech seems to benefit from the period of intense fir mortality. This change results from the influence of long-term anthropogenic disturbances, affecting natural mechanisms that maintain the coexistence of different tree species and change natural disturbance regimes. Indirect anthropogenic influence on tree growth was clearly visible in the gradual decrease of fir increments in the twentieth century, resulting from the high level of air pollution in Europe. Synchronous decreases of fir tree rings’ widths were observed in all three of the sample plots, but the final outcomes depended on the fir age. In most cases, the damage to the foliage limited the competitive abilities of fir, but it did not cause a widespread increase in tree mortality, except for the oldest firs in the BGNP (Babia Góra National Park) plot. BGNP is located in the proximity of industrial agglomeration of Upper Silesia, and it could be exposed to higher level of air pollution than the other two plots. High level of fir regeneration browsing due to the deer overabundance and insufficient number of predators is the second clear indication of the indirect anthropogenic influence on mixed mountain forests. Game impact on fir regeneration is the most pronounced in Babia Góra forests, where fir was almost completely eliminated from the saplings. Deer browsing seems to be the main factor responsible for limiting the number of fir saplings and young fir trees, while the representation of fir among seedlings is high. The experiments conducted in fenced plots located in the mixed forests in BGNP proved that fir and sycamore were the most preferred by deer species among seedlings and saplings. In GNP (Gorce National Park) and TNP (Tatra National Park), the changes in species composition of tree regeneration are similar, but single firs or even small groups of firs are present among saplings. It seems that all of the analysed mixed beech-fir-spruce forests undergo directional changes, causing a systematic decrease in fir representation, and the expansion of beech. This tendency results from the indirect anthropogenic impact, past and present. Fir regeneration decline, alongside with the high level of spruce trees’ mortality in recent years, may lead to a significant decrease in conifers representation in the near future, and to the expansion of beech forests at the cost of mixed ones.
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Hopke, Jill E., i Luis E. Hestres. Communicating about Fossil Fuel Divestment. Oxford University Press, 2017. http://dx.doi.org/10.1093/acrefore/9780190228620.013.566.
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Divestment is a socially responsible investing tactic to remove assets from a sector or industry based on moral objections to its business practices. It has historical roots in the anti-apartheid movement in South Africa. The early-21st-century fossil fuel divestment movement began with climate activist and 350.org co-founder Bill McKibben’s Rolling Stone article, “Global Warming’s Terrifying New Math.” McKibben’s argument centers on three numbers. The first is 2°C, the international target for limiting global warming that was agreed upon at the United Nations Framework Convention on Climate Change 2009 Copenhagen conference of parties (COP). The second is 565 Gigatons, the estimated upper limit of carbon dioxide that the world population can put into the atmosphere and reasonably expect to stay below 2°C. The third number is 2,795 Gigatons, which is the amount of proven fossil fuel reserves. That the amount of proven reserves is five times that which is allowable within the 2°C limit forms the basis for calls to divest.The aggregation of individual divestment campaigns constitutes a movement with shared goals. Divestment can also function as “tactic” to indirectly apply pressure to targets of a movement, such as in the case of the movement to stop the Dakota Access Pipeline in the United States. Since 2012, the fossil fuel divestment movement has been gaining traction, first in the United States and United Kingdom, with student-led organizing focused on pressuring universities to divest endowment assets on moral grounds.In partnership with 350.org, The Guardian launched its Keep it in the Ground campaign in March 2015 at the behest of outgoing editor-in-chief Alan Rusbridger. Within its first year, the digital campaign garnered support from more than a quarter-million online petitioners and won a “campaign of the year” award in the Press Gazette’s British Journalism Awards. Since the launch of The Guardian’s campaign, “keep it in the ground” has become a dominant frame used by fossil fuel divestment activists.Divestment campaigns seek to stigmatize the fossil fuel industry. The rationale for divestment rests on the idea that fossil fuel companies are financially valued based on their resource reserves and will not be able to extract these reserves with a 2°C or lower climate target. Thus, their valuation will be reduced and the financial holdings become “stranded assets.” Critics of divestment have cited the costs and risks to institutional endowments that divestment would entail, arguing that to divest would go against their fiduciary responsibility. Critics have also argued that divesting from fossil fuel assets would have little or no impact on the industry. Some higher education institutions, including Princeton and Harvard, have objected to divestment as a politicization of their endowments. Divestment advocates have responded to this concern by pointing out that not divesting is not a politically neutral act—it is, in fact, choosing the side of fossil fuel corporations.
Części książek na temat "Upper forest limit"
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Opsahl-Sorteberg, Hilde-Gunn, i Espen Evju. "Genome Editing of a Macroalgae with Possible Global Impacts". W A Roadmap for Plant Genome Editing, 121–30. Cham: Springer Nature Switzerland, 2023. http://dx.doi.org/10.1007/978-3-031-46150-7_7.
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AbstractKelp forests are major marine ecosystems and key sources of biodiversity comparable to tropical forests, as pointed out by Darwin on the Beagle in 1834: “Yet if in any country a forest was destroyed, I do not believe nearly so many species of animals would perish as would here, from the destruction of the kelp”. Despite the key roles supporting marine life, our understanding of their biology lags far behind that of land plants. Kelp mitigates the effects of climate change, sequesters CO2, reduces eutrophication while providing biomass for food, feed, and materials. Genome editing together with functional genomics can map genetic diversity potentials for temperature tolerance, important since they already face the upper tolerance limits in some regions. This chapter considers the major genome editing prerequisites; the transformation methods for introducing DNA/RNA and annotated genomes for predicting results. Risk assessments are discussed. These uses of genome editing show how widely applicable the techniques can be used from basic science to securing the global environment for our existence.
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Nakamura, Futoshi. "Concept and Application of Green and Hybrid Infrastructure". W Ecological Research Monographs, 11–30. Singapore: Springer Singapore, 2022. http://dx.doi.org/10.1007/978-981-16-6791-6_2.
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AbstractRecently, Japan has suffered extraordinary damage from typhoons, heavy rains, and megafloods, each of which has exceeded the upper limit of control by managed infrastructure for flood mitigation. First, I present a conceptual framework of hybrid infrastructure at the watershed scale, combining (1) fundamental green infrastructure (GI), composed of forests and wetlands in the watershed; (2) additional multilevel GI, such as flood control basins; and (3) existing engineered disaster prevention infrastructure, such as dams and artificial levees. Second, I introduce the disaster risk reduction function of natural forests and wetlands and three representative traditional flood control measures: discontinuous levees, overflow embankments, and flood protection forests. This GI should be properly allocated and maintained at the watershed scale to reduce damage by megafloods. The multiple types and functions of GI may provide essential habitats for wildlife and recreational opportunities for local residents and others. Finally, I address key points for planning, implementation, and governance of GI at the watershed scale.
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Fan, Runlin, Junsheng Zheng i Zize Zhan. "Penetration Behavior Analysis of Resin During the Impregnation Progress of Expanded Graphite Plates". W Proceedings of the 10th Hydrogen Technology Convention, Volume 1, 291–96. Singapore: Springer Nature Singapore, 2024. http://dx.doi.org/10.1007/978-981-99-8631-6_29.
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AbstractResin impregnation is an important process in the manufacture of composite graphite bipolar plates to reduce their porosity and improve their air tightness as well as flexural strength. In order to improve the filling efficiency of resin into expanded graphite plates and to investigate the factors influencing the resin penetration process, we compare the penetration rate and the upper limit of absorption of epoxy resin, acrylic resin and water in graphite plates. It was found that capillary force is part of the driving forces for resin penetration into the graphite plates, while the boundary layer is the main source of resistance. The higher viscosity of the resin not only leads to a lower resin flow rate, but also results in the formation of a thicker boundary layer, creating additional resistance. Further, the pores are not permeable by resin when the thickness of the boundary layer is greater than the pore size, which is an important reason why the expanded graphite plate is difficult to be filled by resin adequately.
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Nagy, Laszlo, i Georg Grabherr. "Introduction: What is alpine?" W The Biology of Alpine Habitats, 1–5. Oxford University PressOxford, 2009. http://dx.doi.org/10.1093/oso/9780198567035.003.0001.
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Abstract This book introduces the reader to a special mountain environment that can be relatively well defined by its characteristic physiognomy and its relative position along a bioclimatic gradient, which is reflected by the vertical zonation of the vegetation. Alpine environments are found where, along an altitude gradient, natural woody vegetation changes from various lowland and montane forest formations and gives way to dwarf-shrubs, various grass–heath, sedge–heath, and moss–heath formations, and finally, to open frozen ground. This book is about the upper, treeless end of this vertical gradient. The transition from closed forest to treeless vegetation—the upper montane zone with the treeline ecotone—marks the upper limits of tree growth. More precisely, an imaginary line connecting the highest outposts, forming clumps of small-stature trees, called the tree-line is the lower limit of the alpine zone; areas lying above it are called alpine (Grabherr et al. 2003; Körner 2007a). According to such criteria, overall, about 3% of the terrestrial surface of the Earth is covered by al-pine ecosystems, where about 4% of the Earth’s flora is found (Heywood 1995).
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Mosbah, O., F. Z. Sabi, S. M. Terrah, H. Boutchiche, N. Hamamousse, A. Sahila, A. Kaiss i N. Zekri. "Influence of fuel load on the flammability of live Pinus Halepensis needles". W Advances in Forest Fire Research 2022, 1671–74. Imprensa da Universidade de Coimbra, 2022. http://dx.doi.org/10.14195/978-989-26-2298-9_256.
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The fuel flammability, combustibility and fire spread properties depend on several parameters. Among these parameters the heat flux, moisture content, wind and the fuel load. Flammable ignition occurs when the emitted organic volatile components flow mixed with air reaches to a minimum rate corresponding to the lower flammability limit. The gas flow of these components depends on the fuel quantity (load) and its temperature. Therefore, ignition time depends on the fuel load. In this work the effect of the load on ignition time of live Pinus Halepensis needles is investigated using a cone calorimeter (providing three incident heat flux intensities). The average fuel moisture content is around 50% in wet basis. Ignition time exhibits an exponential trend for all the incident heat flux intensities considered with a correlation coefficient R^2>0.96. The exponent corresponds to a characteristic load m ̅_0 around 1 kg/m² slightly dependent on the incident flux within statistical errors. For very small loads compared to m ̅_0 ignition time is nearly independent of load, because the time required for water evaporation is neglected compared to that required for volatiles mixture with air to reach the lower flammability limit. For larger loads (in the range 0.38 kg/m² to 1.27 kg/m²), the time required for water evaporation introduces a shift in ignition time which increases linearly with load. Finally, for large loads compared to m ̅_0, the fuel bed thickness becomes larger than the optical length, and only its top layer is heated, transmitting thus heat to the internal layers by conduction. Therefore, the internal layers evaporate water and cool the upper one, leading to exponential of ignition time with the load. For dry fuels, ignition time appears independent of load.
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Haber, William A. "Plants and Vegetation". W Monteverde. Oxford University Press, 2000. http://dx.doi.org/10.1093/oso/9780195095609.003.0009.
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The vegetation at Monteverde is characterized by two features that are immediately noted by visitors. The first is the overwhelming abundance of mosses, epiphytes, and tree trunk climbers in the cloud forest. The second is the striking variety of vegetation types, and consequent very high regional plant biodiversity, cramped into a small area by the narrow elevational zonation of habitats along the upper mountain slopes. This luxuriance and diversity have been important factors in the attraction of biologists to Monteverde. Lawton and Dryer (1980) described the characteristics and distribution of forest types in the upper Monteverde Cloud Forest Preserve (MCFP), emphasizing the effect of the northeast trade winds on forest structure. With exposure to the trade winds and the accompanying heavy mist and clouds, the forest is reduced in height, has a more broken canopy, and supports greater epiphyte loads. Areas in the lee of the winds develop a forest with less abundant epiphytes and mosses and much taller, straighter trees, forming a closed canopy and more open understory while the strong winds apparently limit the stature of the forest on the exposed ridges, the mist and rain carried in from the Atlantic side during the dry season maintain the diverse epiphyte community of the upper Pacific slope. In contrast, a short walk down the Pacific slope during the dry season leads to progressively drier vegetation zones where ferns, epiphytes, and climbers nearly disappear. Hartshorn (1983) described vegetation in the zones below the cloud forest, with a description of the Holdridge life zone system (Holdridge 1967) and the life zones in Monteverde. In this chapter, the focal area of the vegetation is the study area of the Monteverde Flora Project, which is more extensive than the area covered in the references cited above. The aim of the Monteverde Flora, a project of the Missouri Botanical Garden in collaboration with the Manual to the Plants of Costa Rica Project, is to collect and identify the flora of the Monteverde area and produce identification guides.
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Brown, Timothy, Daniel McEvoy, Andrew Andrade i Britt Parker. "Exploring atmospheric evaporative demand in relation to wildland fire". W Advances in Forest Fire Research 2022, 169–72. Imprensa da Universidade de Coimbra, 2022. http://dx.doi.org/10.14195/978-989-26-2298-9_27.
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Evaporative demand, the upper limit of actual evapotranspiration (ET) that could occur given unlimited surface water supply, has a strong connection to drought and wildfire potential in the western United States and globally. A physically based evaporative demand formulation incorporates temperature, wind speed, humidity, and incoming shortwave radiation – components that drive land surfaceâ€atmosphere interactions and drying. These are also the primary physically based components in the U.S. National Fire Danger Rating System as well as inputs to other fire danger systems. Thus, correspondence between evaporative demand and fire danger can be expected and this has previously been demonstrated such as via the Evaporative Demand Drought Index (EDDI) indicator. For example, EDDI can be decomposed to examine the weighted physical factors over time leading up to a fire event. Utilizing evaporative demand for monitoring and prediction can serve as an early warning of significant fire potential weeks to possibly months in advance. Similarly, evaporative demand can inform prescribed burn planning. Based on the exploration of EDDI indicators prior to fire events, this presentation will discuss analyses of evaporative demand in the context of both wildfire and prescribed fire with an ultimate goal to better understand if and how evaporative demand can be used to inform wildland fire management decisions.
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Restás, Ágoston, Miguel Almeida, Saeid Lotfi, László Bodnár i Domingos Xavier Viegas. "Basic rules for developing fire sprinkler system in the forest". W Advances in Forest Fire Research 2022, 539–43. Imprensa da Universidade de Coimbra, 2022. http://dx.doi.org/10.14195/978-989-26-2298-9_84.
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It is a well-observed phenomenon in developed societies that, in order to return to nature, a part of the society seeks to settle near forests or in the forest creating wildland – urban interface (WUI) areas. It has special features and generates significant risk of fire on the experts try to find responds. In the present study, the authors intend to explore the theoretical foundations of the application of the sprinkler system in forest protecting built environment from fires. Understanding and finding basic rules for the effective sprinkler system application can contribute to reduce the impacts caused by fire. Authors found geometry of circle overlapping generates always problems regarding the effectiveness of sprinkler systems. 50% overlapping in longitudinal axis seems to be acceptable solution. In this case overlapping rate is 78% per circle with 1.6 kg.m-2 water coverage levels and 22% of the circles have 0.8 kg.m-2 water coverage level. Sequentially used system seems good solution for replacing the evaporated water, where 75% of the coverage level is accepted as lowest threshold of the effective rate. As an example, 300 m long protection zone requires 120 sprinkler heads. Building up this zone it requires 1,920 kg of water for wetting up, and then keeping it in service, it requires 7,200 kg.h-1 water. 39% of the service water is lost because it is above the upper limit of effectiveness.
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Whitmore, T. C. "Nutrients and their cycles". W Tropical Rain Forests, 156–73. Oxford University PressOxford, 1998. http://dx.doi.org/10.1093/oso/9780198501480.003.0008.
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Abstract This chapter investigates the effects of human usage of tropical rain forests on the ecosystem’s capital stock of plant mineral nutrients and on their cycles. First the nutrient cycling aspects of shifting agriculture are described, then nutrients and their cycles in primary rain forest. Based on this we discuss the effect on nutrients of different intensities of forest exploitation and the limits of sustainable utilization. The chapter concludes with discussions of the role nutrients might play in determining the distinctive structure and physiognomy of the heath forest and upper montane rain forest formations.
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Whitfield, Joey. "Communicating beyond the Human". W Latin American Culture and the Limits of the Human, 177–200. University Press of Florida, 2020. http://dx.doi.org/10.5744/florida/9781683401490.003.0008.
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Ciro Guerra’s El abrazo de la serpiente (2015) pushes at the limits of the human in several ways. It addresses the genocidal consequences of extractive capitalism, the transcendent promise of both shamanism and religious fanaticism, and communication between humans, animals, and plants, especially via the use of hallucinogenic plants such as ayahuasca. Set in a similar upper Amazon context to Eduardo Kohn’s acclaimed work of posthuman theory How Forests Think, the film dramatizes aspects of his theorization of nonhuman semiosis. In its plot and visual language, El abrazo draws heavily on the writing and photography of Richard Evans Schultes, the ethnobotanist whose work overlapped with that of counter cultural icon Timothy Leary. In this chapter I suggest that Guerra’s dramatization of interspecies communication also speaks to a less academically respected but nonetheless less posthuman line of thought: the counter cultural movement that advocates consumption of hallucinogenic Amazonian plants. In reading El abrazo as the meeting point of the posthuman thinking of Kohn and the neo-ayahasqueros I ask what the similarities are between the two.
Streszczenia konferencji na temat "Upper forest limit"
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Wang, Yong-Yi, Ming Liu, Yaxin Song i David Horsley. "Tensile Strain Models for Strain-Based Design of Pipelines". W ASME 2012 31st International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/omae2012-84241.
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This paper covers the development of tensile strain design models using a multidisciplinary approach, including fundamental fracture mechanics, small-scale material characterization tests, and large-scale tests of full-size pipes. The tensile strain design models are formulated in a four-level format. The Level 1 procedure provides estimated tensile strain capacity (TSC) in a tabular format for quick initial assessment. The initiation toughness alternatively termed apparent toughness is estimated from upper shelf Charpy impact energy. The Level 2 procedure contains a set of parametric equations based on an initiation-control limit state. The tensile strain capacity can be computed from these equations with the input of a pipe’s dimensional and material property parameters. The apparent toughness is estimated from either upper shelf Charpy energy or upper shelf toughness of standard CTOD test specimens. The Level 3 procedure uses the same set of equations as in Level 2 and the toughness values are obtained from low-constraint tests. In the Level 3 procedure, two limit states based on either initiation control or ductile instability can be used. The Level 4 procedure allows the use of direct FEA calculation to develop crack driving force relations. The same limit states as those in Level 3 may be used. The Level 4 procedures should only be used by seasoned experts in special circumstances where lower level procedures are judged inappropriate. The tensile strain design models may be used for the following purposes: (1) The determination of tensile strain capacity for a given set of material properties and flaw size. (2) The determination of acceptable flaw sizes for a given set of material properties and target tensile strain capacity. (3) The selection of material properties to achieve a target strain capacity for a given flaw size. (4) The optimization of the tensile strain capacity by balancing the requirements of material parameters, such as weld strength (thus weld strength mismatch level) versus toughness. The application of the tensile strain design models is given in a companion paper.
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Rodgers, J. Michael, i Tanya E. Jewell. "Design of Reflective Relay for Soft X-ray Lithography". W International Lens Design. Washington, D.C.: Optica Publishing Group, 1990. http://dx.doi.org/10.1364/ild.1990.ltue2.
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Optical lithography has demonstrated a resolution capability of about 0.35 micron. Systems using deep-ultraviolet light sources (e.g., excimer lasers) are anticipated to be able to resolve 0.25 micron features. For optical/UV sources, however, the resolution limit appears to be in the range of 0.15-0.25 microns, due to the upper limit of 1.0 on numerical aperture. One way to resolve smaller features, e.g. 0.1 micron, is to use soft x-ray sources. With such a source (with a wavelength, for example, of 13 nm), an optical system with a modest numerical aperture (e.g., 0.08) can be designed to provide resolution significantly better than is possible with optical/UV sources. An optical design which could be used in the formation of images over a 10x10 mm format in the soft x-ray spectral band is described in this paper.
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Houston, Thomas W., Greg E. Mertz i Andrew Maham. "Comparison of Seismic Design Provisions Using ASCE 43 With Conventional Design Based on ASCE 7 Seismic Loads". W ASME 2016 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/pvp2016-63681.
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One graded approach for the design of nuclear facilities would design high hazard facilities to meet the provisions of ASCE 43 while low hazard facilities would be designed as conventional structures based on the seismic loading and design criteria in ASCE 7. In structures with an intermediate hazard it is not immediately obvious which standard provides a more conservative design. This paper presents a case study that compares the performance of an intermediate hazard structure with ASCE 7 seismic loading and criteria to the target performance goals described in ASCE 43 and DOE-STD-1020. The purposes of seismic design associated with ASCE 7 are; 1) to provide minimum design criteria for structures appropriate to their primary function and use considering the need to protect the health, safety, and welfare of the general public by minimizing the earthquake-related risk to life, and 2) to improve the capability of essential facilities and structures containing substantial quantities of hazardous materials to function during and after design earthquakes. Designs developed using the provisions of ASCE 7 are targeted to a collapse prevention limit state probability of 1% in 50 years. The goal of the earthquake provisions in ASCE 43 is to ensure that high hazard nuclear facilities can withstand the effects of earthquakes with desired performance, expressed as probabilistic Target Performance Goals and various limit, or damage, states. These Target Performance Goals range from 1×10−4 to 1×10−5 with limit states ranging from essentially linear response to short of collapse. There are requirements invoked by ASCE 7 that are different than the requirements of ASCE 43 which prevents a direct computation of performance based on comparing the seismic demand levels required by each standard. These differences include the use of building R values in ASCE 7 compared to component specific Fu values in ASCE 43, the use of different analyses methods, ASCE 7 upper bound limits on seismic forces for some components, the limitations on framing system types, among others. The effect of these differences on the performance achieved between the two standards is evaluated for the design of a reinforced concrete shear wall structure that is representative of the types of structures used in nuclear facilities.
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DelRio, Frank W., Maarten P. de Boer, Leslie M. Phinney, Chris J. Bourdon i Martin L. Dunn. "Van der Waals and Capillary Adhesion of Microelectromechanical Systems". W ASME 2006 International Mechanical Engineering Congress and Exposition. ASMEDC, 2006. http://dx.doi.org/10.1115/imece2006-15169.
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Interfacial adhesion is an important factor in determining the performance and reliability of microelectromechanical systems (MEMS). Van der Waals dispersion forces are the dominant adhesion mechanism in the low relative humidity (RH) regime. At small roughness values, adhesion is mainly due to van der Waals dispersion forces acting across extensive non-contacting areas and is related to 1/Dave2, where Dave is the average surface separation. These contributions must be considered due to the close proximity of the surfaces, which is a result of the planar deposition technology. At large roughness values, van der Waals forces at contacting asperities become the dominating contributor to the adhesion. Capillary condensation of water has a significant effect on rough surface adhesion in the moderate to high RH regime. Above a threshold RH, which is a function of the surface roughness, the adhesion jumps due to meniscus formation at the interface and increases rapidly towards the upper limit of Γ=2 γcos θ=144 mJ/m2, where γ is the liquid surface energy and θ is the contact angle.
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Pylypchuk, Valery, Shih-Ken Chen, Nikolai Moshchuk i Bakhtiar Litkouhi. "Slip-Based Holistic Corner Control". W ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-64882.
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This paper describes an analytical methodology and related algorithms for controlling vehicle tire forces. The purpose of control is to provide a driver with a normal driving feel and keep the vehicle on a target path even under poor road conditions. All the control variables are calculated in real time by minimizing the error between actual and target CG forces and moments. Such a real time optimization is possible due to the availability of analytical solutions for the tire force adjustments derived in the matrix form. A key ingredient of the approach is the idea of constructing weight matrices dependent upon tire states after the optimal linear solution is obtained. When a tire reserve approaches its upper limit, the corresponding weight element increases exponentially. As a result, this stability element dominates the gradient of the target function regardless of CG force error magnitudes. Once the tire state becomes normal then the CG force error correction again becomes the dominant component in the control solutions.
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Oosthuizen, Patrick H., i David Scott. "A Numerical Study of Natural Convective Flow in a Narrow Open Top Enclosure With a Linearly Varying Side-Wall Temperature Attached to a Large Square Enclosure". W ASME 2001 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/imece2001/htd-24124.
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Abstract Natural convective flew in a large square enclosure with a narrow rectangular enclosure mounted symmetrically on the upper surface of this main enclosure has been considered. The horizontal bottom and vertical side-walls of the main enclosure are assumed to be at a uniform high temperature and the vertical side-walls of the narrow top enclosure are assumed have a temperature that varies linearly with height above the main enclosure. The top horizontal wall of the upper enclosure is assumed to be adiabatic The situation consider is an approximate model of that which arises when measurements have to be made in a large enclosure containing a hot fluid and in which the measuring instrument is mounted in a small enclosure which is open at one end to the main tank and which has the instrument mounted at the opposite closed end. In order to ensure that the instrument is not exposed to a temperature that is above its operational limit, the walls of this small enclosure are cooled. Fluid properties have been assumed constant except for the density change with temperature that gives rise to the buoyancy forces, this being treated by means of the Boussinesq type approximation. The governing equations have been written in dimensionless form and the resultant dimensionless equations have been solved using a finite-element method. Results have been obtained for a Prandtl number of 0.7. The effects of Rayleigh number and dimensionless height and width of the top enclosure on the maximum temperature of the top adiabatic surface have been investigated. The results show that provided the aspect ratio of the upper enclosure is kept large, overheating of the upper adiabatic surface of the top enclosure is not likely to occur.
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Ogink, R. H. M. "A Double Birkhoff Wake Oscillator for the Modeling of Vortex-Induced Vibration". W ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2011. http://dx.doi.org/10.1115/omae2011-49435.
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A double Birkhoff wake oscillator for the modeling of vortex-induced vibration is presented in which the oscillating variables are assumed to be associated with the boundary layer/near wake and the far wake. The fluid forces are assumed to consist of a potential added mass force and a force due to vortex shedding. In the limit of vanishing incoming flow velocity, the model equations reduce to a form similar to the Morison equation. The results of the double wake oscillator have been compared with forced vibration measurements and free vibration measurements over a range of mass and damping ratios. The model is capable of describing the most important trends in both the forced and free vibration experiments. Specifically, the double wake oscillator is able to model both the upper and lower branch of free vibration.
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Chen, Shih-Ken, Youssef Ghoneim, Nikolai Moshchuk, Bakhtiar Litkouhi i Valery Pylypchuk. "Tire-Force Based Holistic Corner Control". W ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-89861.
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This paper describes an analytical methodology and the related algorithms for controlling the vehicle tire forces. The purpose of the control is to provide the driver with a normal driving feel and keep the vehicle on a target path even under demanding road conditions. All the control variables are calculated in real time by minimizing a weighted cost function of the errors between actual and target CG forces and moments. Such real time optimization is possible due to the availability of analytical solutions for the tire force adjustments. A key ingredient of the approach is the idea of making the weights in the cost function dependent on tire states after the optimal linear solution is obtained. When the tire reserve approaches its upper limit, the corresponding weighted element increases exponentially. As a result, the stability element in the cost function dominates the gradient of the target function regardless of CG force error magnitudes. Once the tire state becomes normal then the CG force error correction becomes the dominant component in the control solutions.
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Arnold, Sebastien, Vincent Jaffrezic i Gregory Dubes. "DST in Deep Offshore Exploration: Pushing the Limits". W ADIPEC. SPE, 2022. http://dx.doi.org/10.2118/211585-ms.
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Abstract Objectives / Scope Reservoir connectivity has a strong impact on the number of wells that are required to produce a hydrocarbon accumulation and, ultimately, on the associated economics of the development. Appraisal well tests are commonly conducted to confirm that wells are able to drain sufficient reserves. In a deep-water environment however, the test durations are constrained by high rig costs which consequently limit the investigated volumes to only a portion of the reservoir. This paper describes two cases where close collaboration between reservoir and drilling teams allowed to achieve long radius of investigation while minimizing rig time and risk exposure. Methods, Procedures, Process In the first case, a ball valve located below the production packer was acoustically activated during the final build-up to isolate the lower part of the DST string. The upper part was then pulled out of hole to carry out well abandonment. Using an electromagnetic telemetry (EM) system, it was possible to communicate with the downhole gauges installed below the ball valve to continue the monitoring of the pressure build-up during the abandonment operations. In the second case, the rig remained on location but in a harsh environment with high risks of well disconnection. Few years ago, such operation was still considered as technically challenging with important financial exposure in case of disconnection during the DST operations. To face that challenge, the drilling team performed a careful selection and qualification of the DST string and surface equipment using the results of high angle acceptance tests and computerized finite element analysis. The DST acquisition program was optimized by the reservoir team both before and during the operations to minimize the time spent on location while collecting sufficient information. Specific forecast methods were also developed to anticipate any degradations of the weather conditions. Results, Observations, Conclusions In the first case, it was possible to record over 600 hours of undisturbed build-up data while minimizing the time spent on location. An investigated distance of 9.5km from the well was achieved saving additional appraisal wells. In the second case, over 200 hours of pressure data were collected in perfectly safe conditions. This provided key insight on the dynamic behavior of the field and should greatly help to assess the development of this deep offshore discovery. Novel / Additive information This paper illustrates how the combination of innovative techniques and close collaboration between drilling and reservoir teams can maximize the value of information during DSTs. This can help to reduce the number of appraisal wells and to de-risk the development of deep offshore discoveries.
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Chen, Jim S., i Jinho Kim. "Micro Particle Transport and Deposition in Human Upper Airways". W ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-42928.
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The hazard caused by inhaled particles depends on the site at which they deposit within the respiratory system. Knowledge of respiratory aerosol deposition rates and locations is necessary to (1) evaluate potential health effects and establish critical exposure limits and (2) design effective inhaled medications that target specific lung regions. Particles smaller than 10 μm in diameter can be breathed into lungs and are known as inhalable particles, while most of larger particles settle in mouth and nose. Inhalable particles settle in different regions of the lungs and the settling regions depends on the particle size. The motion of a particle is mainly affected by the inertia of the particle and by the particle’s aerodynamic drag. The most important dimensionless parameters in the prediction of particle motion are the flow Reynolds number and the Stoke number, which combines the effects of particle diameter, particle density, shape factor and slip factor. The purpose of this study is to investigate the airflows in human respiratory airways. The influence of particle size on transport and deposition patterns in the 3-D lung model of the human airways is the primary concern of this research. The lung model developed for this research extends from the trachea to the segmental bronchi and it is based on Weibel’s model. The velocity field of air is studied and particle transport and deposition are compared for particles in the diameter range of 1 μm – 100 μm (G0 to G2) and 0.1 μm – 10 μm (G3 to G5) at airflow rates of 6.0, 16.7, and 30.0 L/min, which represent breathing at rest, light activity, and heavy activity, respectively. The investigation is carried out by computational fluid dynamics (CFD) using the software Fluent 6.2. Three-dimensional, steady, incompressible, laminar flow is simulated to obtain the flow field. The discrete phase model (DPM) is then employed to predict the particle trajectories and the deposition efficiency by considering drag and gravity forces. In the present study, the Reynolds number in the range of 200 – 2000 and the Stoke number in the range of 10−5 – 0.12 are investigated. For particle size over 10 μm, deposition mainly occurs by inertial impaction, where deposition generally increases with increases in particle size and flow rate. Most of the larger micron sized particles are captured at the bifurcations, while submicron sized particles flow with the fluid into the lung lower airways. The trajectories of submicron sized particles are strongly influenced by the secondary flow in daughter branches. The present results of particle deposition efficiency in the human upper airways compared well with data in the literature.