1,721,194 research outputs found
Fatigue limit: Is there a link to the quasi-static damage?
No full textThe paper presents experimentally and numerically observed relations of the fatigue life limit and the quasi-static damage threshold, which provide rough estimation for the design strains to use under fatigue strength requirements and allow planning of the fatigue testing programs to minimize the amount of costly and time-consuming experiments with low loads and high number of cycles
Fatigue of Textile and Short Fiber Reinforced Composites
No full textThis book covers several aspects of the fatigue behavior of textile and short fiber reinforced composites. The first part is dedicated to 2D and 3D reinforced textile composites and includes a systematic description of the damage evolution for quasi-static and tensile-tensile fatigue loadings. Acoustic emissions and digital image correlation are considered in order to detect the damage modes’ initiation and development. The acoustic emission thresholds of the quasi-static loading are connected to the ‘fatigue limit’ of the materials with distinctions for glass and carbon reinforcements.
The second part is devoted to the fatigue behavior of injection molded short fiber reinforced composites. Experimental evidence highlighting the dependence of their fatigue response on various factors: fiber and matrix materials, fiber distribution, environmental and loading conditions are described. A hybrid (experimental/simulations) multi-scale method is presented, which drastically reduces the amount of the necessary experimental data for reliable fatigue life predictions
Dynamics and drivers of land use land cover changes in Bangladesh
Full text linkLand is scarce in Bangladesh: Bangladesh occupies ~0.03 % of world’s land area, but supports over ~2% of human population. This high population to land ratio, combined with socioeconomic development has placed tremendous pressure on Bangladesh’s land resources for food, feed, and fuel. This study assesses the dynamics of land use land cover changes and its subsequent drivers at national and sub-national scales. We show contemporary spatial estimates of land change in Bangladesh using national-level analysis of Landsat imageries for 2000 and 2010. This analysis uses our newly compiled extensive socioeconomic database which covers ~480 sub-districts along with biophysical data. We also synthesized information from over 80 survey-based case studies on land use drivers in Bangladesh to complement our macro-scale analysis. We present a detailed analysis of contemporary land change both in terms of national extent and the use of detailed spatial information on land change, socioeconomic factors, and synthesis of case studies. Our results showed eight broad land cover types, of which majority is covered by agriculture (~70%), waterbody (rivers and shrimp ponds) (~10%) and forests (~8%). We found that agriculture, forest and mangrove areas showed a decreasing trend while bare soil, shrub land, waterbody and settlement showed an increasing trend. We identified three major land conversion types: agriculture to shrimp ponds, forest to shrub land and shrimp ponds to bare soil, and their hotspot regions at a sub-district level. Based on our analysis, we find both biophysical and socioeconomic variables contributing to the land conversions. We find that conversion of agriculture to shrimp ponds is driven by increasing rate of population, urban household size and rural household number, access to highways and variation in temperature. Drivers related to forest to shrubland conversion include increasing rate of population, access to rivers, highways and cities, and increased rate of precipitation. Lastly, shrimp ponds to bare soil conversion is driven by access to highway, cities and rivers, elevation and increasing rate of precipitation.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2019-05-01The student, Suravi Shrestha, accepted the attached license on 2017-04-27 at 10:07.The student, Suravi Shrestha, submitted this Thesis for approval on 2017-04-27 at 10:12.This Thesis was approved for publication on 2017-04-27 at 18:07.DSpace SAF Submission Ingestion Package generated from Vireo submission #11108 on 2017-08-10 at 15:07:12Made available in DSpace on 2017-08-10T20:33:29Z (GMT). No. of bitstreams: 2
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Previous issue date: 2017-04-27Embargo set by: Colleen Fallaw for item 102850
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Estimation of the global carbon fluxes due to agricultural management activities using a land surface model (ISAM)
Full text linkAgricultural activities contribute to global greenhouse gas (GHG) emissions and climate. The worldwide hike in the food demand due to the rapidly growing population over time has intensified agricultural activities, resulting in a significant amount of GHG emissions (e.g., CO2, CH4, and N2O). Previous global studies have focused on non-CO2 emissions (i.e., CH4, N2O) and ignored the CO2 emissions from the agriculture sector. This study uses a land surface model with spatially heterogeneous representations of agricultural land management practices to estimate the carbon dynamics induced by agricultural land management practices (i.e., planting crops, fertilization, irrigation, harvesting, and grazing) and land-use change (i.e., agricultural land expansion). The estimated global net carbon emission from agriculture and its related land-use change is 2.26 Pg C/yr (net source) in ca. 2010. The land management activities released 0.85 Pg C/yr (38%), and the land-use change activities emitted 1.41 Pg C/yr (62%). Cropland and grazing land released about 72% and 28% of the total agriculture emissions. Maize, rice, and wheat are the greatest contributing crops. South America (22%), North America (19%) and, South and Southeast Asia (13%) are the leading emitting regions. By quantifying the carbon emissions induced by different agricultural management practices, this study help in improving the representations of land management practices in the climate models.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2022-12-01The student, Prateek Sharma, accepted the attached license on 2020-12-08 at 15:40.The student, Prateek Sharma, submitted this Thesis for approval on 2020-12-08 at 15:58.This Thesis was approved for publication on 2020-12-09 at 17:00.DSpace SAF Submission Ingestion Package generated from Vireo submission #16090 on 2021-03-04 at 16:33:52Made available in DSpace on 2021-03-05T21:47:35Z (GMT). No. of bitstreams: 2
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Modeling the combined environmental effects on net land carbon flux in the present and future scenarios
Full text linkAnthropogenic activities such as fossil fuel production and Land Use and Land Use Changes (LULCC) have been contributing to the sources for the atmospheric carbon dioxide (CO2) in the global carbon cycle. The terrestrial ecosystem globally absorbs about 30% of the anthropogenic CO2 emissions as a sink. Land therefore consists of two counteracting CO2 fluxes, a source from LULCC and a sink from the terrestrial ecosystem. This net land carbon flux (e.g., Net Biome Production, NBP) is the most uncertain component of the Global Carbon Budget (GCB). Hence, it is important to understand the major drivers of sinks and sources of CO2 in order to reduce the uncertainty of GCB. This study quantifies the combined environmental effects (atmospheric CO2, nitrogen (N) deposition, climate change, and LULCC) on NBP and the relative contribution of individual environmental effects in the present decade (2009~2018) and the last decade (2090~2099) of the 21st century by using a global land surface model, Integrated Science Assessment Model (ISAM). The model is driven by historical observation data and future projection data from Scenario Model Intercomparison Project (ScenarioMIP) of Coupled Models Intercomparison Project Phase 6 (CMIP6). Two combinations of Shared Socioeconomic Pathways (SSP) and radiative forcing (SSP2-45 and SSP5-85) are used to force the model. SSP2-45 has radiative forcing of 4.5 W/m2 and Middle of the Road of SSP. SSP5-85 has radiative forcing of 8.5 W/m2 and Fossil Fueled Development of SSP. The modeled simulation results show that the land continuously acts as a net sink of CO2 in the future scenarios. The estimated combined environmental effects on the mean NBP for the 2090s under SSP2-45 and SSP5-85 are 0.75 PgC/yr and 3.47 PgC/yr, respectively from the value of 0.24 PgC/yr for the 2010s. The atmospheric CO2 + N deposition effect contributes to the net sink of CO2 for the present decade (3.8 PgC/yr) and the last decade of the future scenarios (SSP2-45: 3.79 PgC/yr and SSP585: 10.49 PgC/yr). The greatest sinks correspond to forest areas in the tropics, which show higher CO2 fertilization and lesser N limitations than the extra-tropics. The LULCC effect (-2.54 PgC/yr) dominates over the atmospheric CO2 + N deposition effect in the present decade. This leads to the net source of CO2 in some tropical and extra-tropical regions. However, in the 2090s, warmer climate under two future scenarios leads to more CO2 release (SSP2-45: -1.68 PgC/yr and SSP5-85: -5.64 PgC/yr) to the atmosphere than due to LULCC effect (SSP2-45: -1.35 PgC/yr and SSP5-85: -1.37 PgC/yr). Overall, the study emphasizes how the environmental effects drive the temporal and spatial variations of net land carbon flux through their compensation and dominance in the present and future scenarios.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2022-05-01The student, Eunkyoung Choi, accepted the attached license on 2020-05-13 at 11:43.The student, Eunkyoung Choi, submitted this Thesis for approval on 2020-05-13 at 12:16.This Thesis was approved for publication on 2020-05-14 at 10:01.DSpace SAF Submission Ingestion Package generated from Vireo submission #15378 on 2020-08-25 at 17:31:23Made available in DSpace on 2020-08-26T23:58:49Z (GMT). No. of bitstreams: 2
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
An Integrated Modeling Study of Ocean Circulation, the Ocean Carbon Cycle, Marine Ecosystems, and Climate Change
No full textThe unifying theme of this study is to conduct an extensive exploration of various interactions between ocean circulation, the carbon cycle, marine ecosystems, and climate change using an earth system model of intermediate complexity, ISAM-2.5D (Integrated Science Assessment Model). First, through the simulation of radiocarbon (in terms of Delta14C) it is demonstrated that the inclusion of isopycnal diffusion and a parameterization of eddy-induced circulation in the ISAM-2.5D model yields the most realistic representation of ocean mixing and circulation. Secondly, I demonstrate the value of the simulation of multiple tracers, combined with a variety of observational data, in constraining the ISAM-2.5D model that has been constrained by the simulation of Delta14C. Through the simulation of ocean biogeochemical cycles and CFC-11 and the use of the updated observational data of bomb radiocarbon, I improve the Delta14C-constrained ISAM-2.5D model's performance in simulating ocean circulation and air-sea gas exchange, as well as its credibility in predicting oceanic carbon uptake. Third, I use the ISAM-2.5D model to assess the efficiency of direct carbon injection into the deep ocean with the influence of climate change. It is shown that the consideration of climate change enhances the retention time of injected carbon into the Atlantic Ocean as a result of weakened North Atlantic overturning circulation in a warming climate. However, the climatic effect is insignificant on the efficiency of carbon injection into the Pacific and Indian Oceans. Finally, I quantify that increased atmospheric CO2 concentrations would be mainly responsible for future ocean acidification, including lowering in ocean pH and sea water saturation state with respect to carbonate minerals. The consideration of climate change produces a second-order modification to projected ocean acidification. Therefore, in addition to its radiative effects on climate change, increased atmospheric CO2 concentrations could pose a great threat to marine ecosystems through ocean acidification, which is largely independent of the magnitude of climate change. Overall, this study yields a number of valuable insights into different aspects of the coupled ocean circulation-marine ecosystems-carbon cycle system and contributes to advance our understanding of the ocean carbon cycle and marine chemistry in an environment of changing climate.Made available in DSpace on 2015-09-28T14:52:22Z (GMT). No. of bitstreams: 2
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Previous issue date: 2006Embargo set by: Seth Robbins for item 87251
Lift date: Forever
Reason: Restricted to the U of I community idenfinitely during batch ingest of legacy ETDsRestricted to the U of I community idenfinitely during batch ingest of legacy ETDsU of I Only155 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006
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