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Evaluating the biosignature potential of ammonium in Proterozoic red beds and implications for the search for life on Mars
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作者 Eva E.Stüeken Philip Fralick +1 位作者 Stephen Hillier Anthony R.Prave 《Earth and Planetary Physics》 EI CAS CSCD 2024年第6期836-853,共18页
Over the past two decades,it has become increasingly apparent that early Mars may once have been warmer,wetter and more habitable for microbial life than it is today,which has spurred discussions about potential biosi... Over the past two decades,it has become increasingly apparent that early Mars may once have been warmer,wetter and more habitable for microbial life than it is today,which has spurred discussions about potential biosignatures that may be preserved in Martian sediments.An impediment to this line of research is the pervasive oxidation of Mars’surface due to photochemical oxidants that have likely destroyed remnants of organic matter.Here,we investigate whether nitrogen(N)transferred from biomass to phyllosilicate minerals during diagenesis can be preserved in oxidized mudrocks.We investigate two sequences of terrestrial Proterozoic red beds,namely the Sibley Group(1.4 Ga)in Canada and the Stoer Group(1.2 Ga)in Scotland,and we find enrichments in authigenic N in the range of several tens of ppm in both units.The highest concentrations(ca.100 ppm on average)are found in the most desiccated red beds of the Stoer Group,concurrent with enrichments in potassium(K).We discuss similarities and differences between the two sets of rocks with regards to salinity,pH,biological productivity and K-metasomatism,and we conclude that the ideal mechanism for the preservation of biogenic N in red beds may be in-situ release of ammonium from microbial mats into the clay substrate,possibly facilitated by early diagenetic,biologically induced illitization.Illite and smectite have been observed on Mars,and experiments suggest that Martian waters contained moderate amounts of dissolved K.Hence,it is conceivable that a similar K and N enrichment process could have occurred as to what we document for the Proterozoic,preserving evidence of life that may have survived to the modern day. 展开更多
关键词 red beds BIOSIGNATURE MARS NITROGEN AMMONIUM clay minerals
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New indices to balanceα-diversity against tree size inequality
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作者 Li Zhang Brady K.Quinn +4 位作者 Cang Hui Meng Lian Johan Gielis Jie Gao Peijian Shi 《Journal of Forestry Research》 SCIE EI CAS CSCD 2024年第1期229-237,共9页
The number and composition of species in a community can be quantified withα-diversity indices,including species richness(R),Simpson’s index(D),and the Shannon-Wiener index(H΄).In forest communities,there are large ... The number and composition of species in a community can be quantified withα-diversity indices,including species richness(R),Simpson’s index(D),and the Shannon-Wiener index(H΄).In forest communities,there are large variations in tree size among species and individu-als of the same species,which result in differences in eco-logical processes and ecosystem functions.However,tree size inequality(TSI)has been largely neglected in studies using the available diversity indices.The TSI in the diameter at breast height(DBH)data for each of 99920 m×20 m forest census quadrats was quantified using the Gini index(GI),a measure of the inequality of size distribution.The generalized performance equation was used to describe the rotated and right-shifted Lorenz curve of the cumulative proportion of DBH and the cumulative proportion of number of trees per quadrat.We also examined the relationships ofα-diversity indices with the GI using correlation tests.The generalized performance equation effectively described the rotated and right-shifted Lorenz curve of DBH distributions,with most root-mean-square errors(990 out of 999 quadrats)being<0.0030.There were significant positive correlations between each of threeα-diversity indices(i.e.,R,D,and H’)and the GI.Nevertheless,the total abundance of trees in each quadrat did not significantly influence the GI.This means that the TSI increased with increasing spe-cies diversity.Thus,two new indices are proposed that can balanceα-diversity against the extent of TSI in the com-munity:(1−GI)×D,and(1−GI)×H’.These new indices were significantly correlated with the original D and H΄,and did not increase the extent of variation within each group of indices.This study presents a useful tool for quantifying both species diversity and the variation in tree sizes in forest communities,especially in the face of cumulative species loss under global climate change. 展开更多
关键词 Diameter at breast height(DBH) Gini index Shannon-Wiener index Simpson’s index QUADRAT Tree size
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Multiphysics processes in the interfacial transition zone of fiber-reinforced cementitious composites under induced curing pressure and implications for mine backfill materials: A critical review 被引量:1
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作者 Brett Holmberg Liang Cui 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS CSCD 2023年第8期1474-1489,共16页
The mesoscale fiber-matrix interfacial transition zone(FM-ITZ) under induced curing pressure plays a key role in the effectiveness of fiber reinforcement and the engineering application of fiber-reinforced cementitiou... The mesoscale fiber-matrix interfacial transition zone(FM-ITZ) under induced curing pressure plays a key role in the effectiveness of fiber reinforcement and the engineering application of fiber-reinforced cementitious composites(FRCCs). This critical review establishes the link among induced curing pressure(i.e., external loading condition), multiphysics processes(i.e., internal governing mechanism), and interface behavior(i.e., material behavior) for FRCC materials through analysis of the state-of-the-art research findings on the FM-ITZ of FRCC materials. The following results are obtained. For the mechanical process, the induced curing pressure changes the stress state and enhances multicracking behavior, which can strengthen the FM-ITZ. For the hydraulic process, the strengthened seepage of the FM-ITZ under induced curing pressure weakens the effective stress and exaggerates the deficiency in water retention capacity between the bulk matrix and the FMITZ. For the thermal process, the induced curing pressure causes a steep temperature gradient in the FM-ITZ and thus influences the temperature evolution and thermally-induced microcracks in the FM-ITZ. For the chemical process, the induced curing pressure enhances hydration kinetics and results in the formation of additional hydration products in the FM-ITZ. Moreover, recommendations are proposed on the basis of findings from this review to facilitate the implementation of fiber reinforcement in cemented paste backfill technology. 展开更多
关键词 cemented paste backfill cementitious composites interfacial transition zone fiber reinforcement MULTIPHYSICS induced curing pressure
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The formation of orthogonal joint systems and cuboidal blocks:New insights gained from flat-lying limestone beds in the region of Havre-Saint-Pierre(Quebec,Canada)
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作者 Shaocheng Ji Yvéric Rousseau +1 位作者 Denis Marcotte Noah John Phillips 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2023年第12期3079-3093,共15页
Vertical orthogonal joints are a common feature in shallow crustal rocks.There are several competing theories for their formation despite the ubiquity.We examined the exceptional exposures of orthogonal joints in flat... Vertical orthogonal joints are a common feature in shallow crustal rocks.There are several competing theories for their formation despite the ubiquity.We examined the exceptional exposures of orthogonal joints in flat-lying Ordovician limestone beds from the Havre-Saint-Pierre Region in Quebec,Canada(north shore of Saint-Lawrence River)to test conceptual models of joint formation in a natural setting.In the region,the spacing of cross-joints is consistently larger than the spacing of systematic joints by a factor of 1.5 approximately.The joint-spacing-to-bed-thickness ratios(s/t)are much larger in these beds(s/t=4.3 for systematic joints,and 6.4 for cross-joints)than those in higher strained strata along the south shore of the Saint-Lawrence River(s/t=1),highlighting the effect of tectonic strain in decreasing fracture spacing and block size.The high values of s/t indicate that cross-joint formation was unlikely caused by a switch from compression to tension once a critical s/t ratio for systematic joints was reached(as hypothesized in previous studies).We proposed a new model for the formation of orthogonal joint systems where the principal stress axes locally switch during the formation of systematic fractures.The presence of ladder-shaped orthogonal joints suggests a state of effective stress withσ_(1)^(∗)≫0>σ_(2)^(∗)>σ_(3)^(∗)and whereσ_(2)^(∗)-σ_(3)^(∗)is within the range of fracture strength variability at the time of fracture.This research provides a new mechanical model for the formation of orthogonal joint systems and cuboidal blocks. 展开更多
关键词 Plato's cuboids Orthogonal joints Fracture spacing LIMESTONE Layered rock mechanics Appalachian geology
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Collective coherent emission of electrons in strong laser fields and perspective for hard x-ray lasers
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作者 E.G.Gelfer A.M.Fedotov +1 位作者 O.Klimo S.Weber 《Matter and Radiation at Extremes》 SCIE EI CSCD 2024年第2期1-3,共3页
Coherent motion of particles in a plasma can imprint itself on radiation.The recent advent of high-power lasers—allowing the nonlinear inverse Compton-scattering regime to be reached—has opened the possibility of lo... Coherent motion of particles in a plasma can imprint itself on radiation.The recent advent of high-power lasers—allowing the nonlinear inverse Compton-scattering regime to be reached—has opened the possibility of looking at collective effects in laser–plasma interactions.Under certain conditions,the collective interaction of many electrons with a laser pulse can generate coherent radiation in the hard x-ray regime.This perspective paper explains the limitations under which such a regime might be attained. 展开更多
关键词 laser SCATTERING COHERENT
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Evolutionary history shapes variation of wood density of tree species across the world 被引量:1
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作者 Fangbing Li Hong Qian +7 位作者 Jordi Sardans Dzhamal Y.Amishev Zixuan Wang Changyue Zhang Tonggui Wu Xiaoniu Xu Xiao Tao Xingzhao Huang 《Plant Diversity》 SCIE CAS CSCD 2024年第3期283-293,共11页
The effect of evolutionary history on wood density variation may play an important role in shaping variation in wood density,but this has largely not been tested.Using a comprehensive global dataset including 27,297 m... The effect of evolutionary history on wood density variation may play an important role in shaping variation in wood density,but this has largely not been tested.Using a comprehensive global dataset including 27,297 measurements of wood density from 2621 tree species worldwide,we test the hypothesis that the legacy of evolutionary history plays an important role in driving the variation of wood density among tree species.We assessed phylogenetic signal in different taxonomic(e.g.,angiosperms and gymnosperms)and ecological(e.g.,tropical,temperate,and boreal)groups of tree species,explored the biogeographical and phylogenetic patterns of wood density,and quantified the relative importance of current environmental factors(e.g.,climatic and soil variables)and evolutionary history(i.e.,phylogenetic relatedness among species and lineages)in driving global wood density variation.We found that wood density displayed a significant phylogenetic signal.Wood density differed among different biomes and climatic zones,with higher mean values of wood density in relatively drier regions(highest in subtropical desert).Our study revealed that at a global scale,for angiosperms and gymnosperms combined,phylogeny and species(representing the variance explained by taxonomy and not direct explained by long-term evolution process)explained 84.3%and 7.7%of total wood density variation,respectively,whereas current environment explained 2.7%of total wood density variation when phylogeny and species were taken into account.When angiosperms and gymnosperms were considered separately,the three proportions of explained variation are,respectively,84.2%,7.5%and 6.7%for angiosperms,and 45.7%,21.3%and 18.6%for gymnosperms.Our study shows that evolutionary history outpaced current environmental factors in shaping global variation in wood density. 展开更多
关键词 Wood density PHYLOGENY ANGIOSPERMS GYMNOSPERMS Climate factors Biophysical parameters
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Matched pair analysis of the effect of longer hypothermic machine perfusion time on kidney transplant outcomes
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作者 Carlos Verdiales Luke Baxter +2 位作者 Hyun Ja Lim Gavin Beck Michael A Moser 《World Journal of Transplantation》 2024年第3期95-101,共7页
BACKGROUND Hypothermic machine perfusion(HMP)has demonstrated benefits in terms of early kidney transplant function compared to static cold storage.While longer preservation times have shown detrimental effects,a prev... BACKGROUND Hypothermic machine perfusion(HMP)has demonstrated benefits in terms of early kidney transplant function compared to static cold storage.While longer preservation times have shown detrimental effects,a previous paired study indicated that longer pump times(the second kidney in a pair)might lead to improved outcomes.AIM To revisit the prior paired study's somewhat unexpected results by reviewing our program's experience.METHODS A total of 61 pairs of transplant recipients who received kidneys from the same donor(2012-2021)were analyzed.Patients were divided into two groups depending on whether they were transplanted first(K1)or second(K2).Therefore,the patients in each pair had identical donor characteristics,except for time on the pump.Statistical analyses included Kaplan-Meyer analysis and paired tests,including McNemar's test,student's paired t-test,or Wilcoxon's test,as appropriate.RESULTS The two groups of recipients had similar demographics(age,body mass index,diabetes,time on dialysis,sensit-ization and retransplants).Cold ischemic times for K1 and K2 were 8.9(95%CI:7.9,9.8)and 14.7 hours(13.7,15.8)(P<0.0001),respectively.Overall,K2 had a higher rate of freedom from biopsy-proven acute rejection at 1 year(P=0.015).Delayed graft function was less common in K2,12/61(20%)than in K1,20/61(33%)(P=0.046).Finally,K2 showed a higher graft survival than K1(P=0.023).CONCLUSION Our results agree with a previous study that suggested possible advantages to longer pump times.Both studies should encourage further research into HMP's potential anti-inflammatory effect. 展开更多
关键词 Hypothermic machine perfusion Paired kidney study Early acute rejection
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Spatiotemporal evolution of thermo-hydro-mechanical-chemical processes in cemented paste backfill under interfacial loading 被引量:2
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作者 Sai Pramod Singalreddy Liang Cui Kun Fang 《International Journal of Mining Science and Technology》 SCIE EI CAS CSCD 2022年第6期1207-1217,共11页
Cemented paste backfill(CPB)and rock interface interaction causes the formation of an interfacial loading and affects the thermal,hydraulic,mechanical,and chemical processes in bulk CPB and thus its in-situ behavior.I... Cemented paste backfill(CPB)and rock interface interaction causes the formation of an interfacial loading and affects the thermal,hydraulic,mechanical,and chemical processes in bulk CPB and thus its in-situ behavior.In this study,a new meter-sized column model is developed to systematically investigate the multiphysics processes in CPB under interfacial loading.The obtained results discover that for the mechanical process,the interfacial loading leads to a reduced settlement and a weakened stress level in CPB.For the hydraulic process,lower matric suction and smaller moisture content coexist in CPB under interfacial loading.For the thermal process,the interfacial loading weakens the porosity-dependent thermal conduction and causes retardation in temperature variation relative to the ambient temperature.For the chemical process,weakened cement hydration with smaller electrical conductivity was observed in CPB under interfacial loading.Therefore,the obtained results reveal the linkage between the interfacial loading and multiphysics processes in CPB and thus contribute to an in-depth understanding of the multiphysics behavior of CPB in underground mines. 展开更多
关键词 Spatiotemporal evolution Multiphysics processes Interfacial loading Cemented paste backfill Underground mine
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Biochar-based bioenergy and its environmental impact in Northwestern Ontario Canada: A review 被引量:5
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作者 Krish Homagain Chander Shahi +1 位作者 Nancy Luckai Mahadev Sharma 《Journal of Forestry Research》 SCIE CAS CSCD 2014年第4期737-748,共12页
Biochar is normally produced as a by-product of bioenergy. However, if biochar is produced as a co-product with bioenergy from sustainably managed forests and used for soil amendment, it could pro- vide a carbon neutr... Biochar is normally produced as a by-product of bioenergy. However, if biochar is produced as a co-product with bioenergy from sustainably managed forests and used for soil amendment, it could pro- vide a carbon neutral or even carbon negative solution for current envi- ronmental degradation problems. In this paper, we present a comprehen- sive review of biochar production as a co-product of bioenergy and its implications. We focus on biochar production with reference to biomass availability and sustainability and on bioehar utilization for its soil amendment and greenhouse gas emissions reduction properties. Past studies confirm that northwestern Ontario has a sustainable and sufficient supply of biomass feedstock that can be used to produce bioenergy, with biochar as a co-product that can replace fossil fuel consumption, increase soil productivity and sequester carbon in the long run. For the next step, we recommend that comprehensive life cycle assessment of bio- char-based bioenergy production, from raw material collection to bioehar application, with an extensive economic assessment is necessary for making this technology commercially viable in northwestern Ontario. 展开更多
关键词 biomass life cycle assessment LCA C02 carbon sequestra-tion greenhouse gas emissions soil amendment
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An application of data envelopment analysis to investigate the efficiency of lumber industry in northwestern Ontario,Canada 被引量:1
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作者 Thakur Prasad Upadhyay Chander Shahi Mathew Leitch Reino Pulkki 《Journal of Forestry Research》 SCIE CAS CSCD 2012年第4期675-684,共10页
This study aims at exploring the technical efficiency of lum- ber industry in northwestern Ontario, Canada using data envelopment analysis (DEA). The DEA model analyzes relative technical efficiency of lumber mills ... This study aims at exploring the technical efficiency of lum- ber industry in northwestern Ontario, Canada using data envelopment analysis (DEA). The DEA model analyzes relative technical efficiency of lumber mills with disproportionate inputs and outputs by dividing the 10- year time series data, for inputs and outputs of 24 lumber mills, over two periods (1999-2003 and 2004-2008). Four inputs, namely, material (log volume), labour (man-hours), two types of energy (hog-fuel and electric- ity), and one output (lumber volume) are used in this study. The trend analysis shows an annual reduction of 10%, 13% and 13% for lumber output, log consumption (input) and number of employees, respectively, during the period 1999-2008. The results from DEA with two scenarios with energy inputs and without energy inputs, for the two periods are found to be mixed and interesting. While some mills have improved their performance in terms of best use of available scarce inputs in the second period, some have shown negative per cent change in efficiency. In the with energy input and the without energy input scenario, some of the mills show a reduction in efficiency in the second period from the first period, with the highest estimated reductions of-13.9% and -47.6%, respectively. A possible explanation for these negative performances of mills in the latter period is the decline in production in the second period compared to the first period, where these mills were not able to adjust their inputs (mostly labour) as proportional lay-offs might not have been possible. These results provide policy makers and industry stakeholders with an improved understanding of the trends of efficiency and employ- ment as well as reallocation opportunities of future inputs in order to increase benefits from this sector. 展开更多
关键词 allocative efficiency forest products industry MODELLING production inputs technical efficiency
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Dynamic buckling mechanism of pillar rockbursts induced by stress waves 被引量:1
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作者 J.Deng N.S.Kanwar +1 位作者 M.D.Pandey W.-C.Xie 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2019年第5期944-953,共10页
Rockbursts are sudden and violent rock failures that can lead to huge production and equipment losses,injury or death of mining workers.Buckling has been regarded as one of the key mechanisms of rockbursts,which are o... Rockbursts are sudden and violent rock failures that can lead to huge production and equipment losses,injury or death of mining workers.Buckling has been regarded as one of the key mechanisms of rockbursts,which are often induced by dynamic loads from mining excavations,such as drilling and blasting in underground mining.The paper attempts to investigate the dynamic buckling mechanism of pillar rockbursts in underground mining,by considering rockbursts as a dynamic stability problem of underground rock structures.The results include:(1)A new explanation of the“sudden and violent”phenomenon of rockbursts,characterized by exponential growth of the amplitudes of transverse displacement responses,even in the presence of rock damping;(2)Identification of the critical role in inducing rockbursts of dynamic loads that bear frequencies approximately double the natural pillar frequency;(3)The greater influence on rockburst occurrence of the amplitude of dynamic component relative to the static component of loads;and(4)Quantification of the relative effects of stress waveform of dynamic loads on pillar rockbursts,which are in decreasing order if other parameters remain constant:rectangular,sinusoidal,and exponential waveforms.Application examples are provided and limitations of the approach are discussed.This research is motivated by the on-going and ubiquitous occurrence of rockbursts in underground excavations all around the world.In contrast to conventional methods that use rock specimens or rock materials to study rockbursts,this investigation emphasizes the structural effects on rockbursts,which has potential applications in hard rock mining engineering. 展开更多
关键词 PILLAR rockbursts BUCKLING MECHANISM Stress WAVES Structural ROCK MECHANICS
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Characteristics of Light Availability Under Forest Canopies and Its Influences on Photosynthesis of Understory Plants 被引量:1
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作者 Han Y.H.Chen 《Forestry Studies in China》 CAS 2003年第3期54-62,共9页
Available light under forest canopies includes two components, diffuse light and direct light (sunflecks), and is characterized as low and highly dynamic. Understory habitats under different forest types experience di... Available light under forest canopies includes two components, diffuse light and direct light (sunflecks), and is characterized as low and highly dynamic. Understory habitats under different forest types experience different light conditions. Sunflecks as a critical resource for understory plants have great importance on carbon gain of understory plants. Under the light-limiting habitat, understory plants exhibit a high light utilization efficiency attributed by a post-illumination CO2 uptake. Although different species have different photosynthetic responses, shade plants appear to be acclimated to respond more quickly and efficiently to sunflecks. This acclimation includes a faster induction, relatively lower rate of induction loss, lower photosynthetic compensation point, and higher water use efficiency. The process that shade plants harvest light energy is not well known. Studies of photosynthetic responses to sunflecks in natural conditions are rare. Little is known about constraints on sunfleck utilization, which may change seasonally. Extensive field studies in conjunction with laboratory investigations will be needed to further understand potential and actual constraints on sunfleck utilization. Most studies on photosynthetic responses to fluctuating light condition were done in the level of leaves. Fluctuating light utilization on the basis of whole plants and populations presents future challenges to ecologists. 展开更多
关键词 forest understory light availability sunflecks shade plants PHOTOSYNTHESIS light utilization efficiency.
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Allometric models for aboveground biomass of six common subtropical shrubs and small trees 被引量:2
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作者 Cheng Huang Chun Feng +6 位作者 Yuhua Ma Hua Liu Zhaocheng Wang Shaobo Yang Wenjing Wang Songling Fu Han Y.H.Chen 《Journal of Forestry Research》 SCIE CAS CSCD 2022年第4期1317-1328,共12页
The aboveground biomass(AGB)of shrubs and small trees is the main component for the productivity and carbon storage of understory vegetation in subtropical secondary forests.However,few allometric models exist to accu... The aboveground biomass(AGB)of shrubs and small trees is the main component for the productivity and carbon storage of understory vegetation in subtropical secondary forests.However,few allometric models exist to accurately evaluate understory biomass.To estimate the AGB of five common shrub(diameter at base<5 cm,<5 m high)and one small tree species(<8 m high,trees’s seedling),206 individuals were harvested and species-specific and multi-species allometric models developed based on four predictors,height(H),stem diameter(D),crown area(Ca),and wood density(ρ).As expected,the six species possessed greater biomass in their stems compared with branches,with the lowest biomass in the leaves.Species-specific allometric models that employed stem diameter and the combined variables of D~2H andρDH as predictors accurately estimated the components and total AGB,with R^(2) values from 0.602 and 0.971.A multi-species shrub allometric model revealed that wood density×diameter×height(ρDH)was the best predictor,with R^(2) values ranging from between 0.81 and 0.89 for the components and total AGB,respectively.These results indicated that height(H)and diameter(D)were effective predictors for the models to estimate the AGB of the six species,and the introduction of wood density(ρ)improved their accuracy.The optimal models selected in this study could be applied to estimate the biomass of shrubs and small trees in subtropical regions. 展开更多
关键词 Aboveground biomass Allometric models SHRUBS Small trees Subtropical forests
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Deciphering anomalous Ag enrichment recorded by galena in Dayingezhuang Au(-Ag)deposit,Jiaodong Peninsula,Eastern China 被引量:4
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作者 Zhan-kun LIU Xian-cheng MAO +4 位作者 Fan-yun WANG Lei TANG Guang-huan CHEN Jin CHEN Hao DENG 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2021年第12期3831-3846,共16页
Texture,geochemistry,and in-situ Pb isotope of galena were investigated to probe the origin of anomalous Ag enrichment in the Dayingezhuang Au(-Ag)deposit.Silver enrichment postdates the main Au mineralization and occ... Texture,geochemistry,and in-situ Pb isotope of galena were investigated to probe the origin of anomalous Ag enrichment in the Dayingezhuang Au(-Ag)deposit.Silver enrichment postdates the main Au mineralization and occurs in the south of the Dayingezhuang deposit.It is primarily associated with galena and the exsolution of Ag-rich sulfosalts(e.g.,matildite)in distal vein-ores related to steeply dipping brittle fractures.Silver-rich galena is characterized by the least radiogenic Pb isotope signature(^(206)Pb/^(204)Pb 17.195–17.258 and ^(208)Pb/^(204)Pb 37.706–37.793),possibly indicating a metasomatized lithospheric mantle or modified lower crustal source for Pb and Ag.Both of these mafic and ultramafic source regions have been previously suggested as Au reservoirs for other Jiaodong Au deposits,implying that the metal reservoir has only a weak control on the uneven Ag-enrichment.Since the Ag-enrichment areas are located in the footwalls of both the Dayingezhuang and Zhaoping faults,the enrichment was most likely dominated by local rotational stress during coeval movements of the two faults in a NE–SW compression and NW−SE extension regime.This work highlights the shallow-crust structural deformation responsible for controlling the flow of late ore-forming fluid resulting in local anomalous metal enrichment. 展开更多
关键词 GALENA lead isotope silver Dayingezhuang deposit Jiaodong Peninsula
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Life cycle cost and economic assessment of biochar-based bioenergy production and biochar land application in Northwestern Ontario, Canada 被引量:1
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作者 Krish Homagain Chander Shahi +1 位作者 Nancy Luckai Mahadev Sharma 《Forest Ecosystems》 SCIE CSCD 2017年第1期12-21,共10页
Background: Replacement of fossil fuel based energy with biochar-based bioenergy production can help reduce greenhouse gas emissions while mitigating the adverse impacts of climate change and global warming. However,... Background: Replacement of fossil fuel based energy with biochar-based bioenergy production can help reduce greenhouse gas emissions while mitigating the adverse impacts of climate change and global warming. However, the production of biochar-based bioenergy depends on a sustainable supply of biomass. Although, Northwestern Ontario has a rich and sustainable supply of woody biomass, a comprehensive life cycle cost and economic assessment of biochar-based bioenergy production technology has not been done so far in the region. Methods: In this paper, we conducted a thorough life cycle cost assessment (LCCA) of biochar-based bioenergy production and its land application under four different scenarios: 1) biochar production with low feedstock availability; 2) biochar production with high feedstock availability; 3) biochar production with low feedstock availability and its land application; and 4) biochar production with high feedstock availability and its land applicationusing SimaPro, EIOLCA software and spreadsheet modeling. Based on the LCCA results, we further conducted an economic assessment for the break-even and viability of this technology over the project period. Results: It was found that the economic viability of biochar-based bioenergy production system within the life cycle analysis system boundary based on study assumptions is directly dependent on costs of pyrolysis, feedstock processing (drying, grinding and pelletization) and collection on site and the value of total carbon offset provided by the system. Sensitivity analysis of transportation distance and different values of C offset showed that the system is profitable in case of high biomass availability within 200 km and when the cost of carbon sequestration exceeds CAD S60 per tonne of equivalent carbon (CO2e). Conclusions: Biochar-based bioenergy system is economically viable when life cycle costs and environmental assumptions are accounted for. This study provides a medium scale slow-pyrolysis plant scenario and we recommend similar experiments with large-scale plants in order to implement the technology at industrial scale. 展开更多
关键词 LCA LCCA SimaPro BIOCHAR Biomass PYROLYSIS BIOENERGY Wood Pellets
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Determining thresholds of low soil temperature for ecophysiological traits of black spruce and jack pine seedlings 被引量:1
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作者 CHENG Song 《Forestry Studies in China》 CAS 2009年第3期139-147,共9页
Many studies have estimated approximately ranges of thresholds of low soil temperature in the growth and ecophysi-ological traits of trees, but difficultly determined the exact values. To resolve the problem, black sp... Many studies have estimated approximately ranges of thresholds of low soil temperature in the growth and ecophysi-ological traits of trees, but difficultly determined the exact values. To resolve the problem, black spruce (Picea mariana) and jack pine (Pinus banksiana) seedlings were exposed to 5, 10, 15, 20, 25, 30 and 35℃ soil temperature in greenhouses. After 90 days of the treatment, net photosynthetic rate (A), stomatal conductance (gs), transpiration rate (E), water use efficiency (WUE) and specific leaf area (SLA) were measured. This study showed that all the traits had an asymmetrical peak relationship with changing soil temperature, the relationship was well simulated using a cubic curvilinear model, and the exact thresholds could be derived from the second derivative of the model. The results revealed that the thresholds varied among ecophysiological traits and between tree species. In black spruce, the thresholds were 14.1, 14.7, 10.7, 14.4 and 16.2℃ forA, gs, E, WUE and SLA; 15.4, 10.4, 14.7, 16.9 and 10.5℃ for the corresponding traits in jack pine. The lowest thresholds of E in black spruce and gs in jack pine were an indicator representing the minimum requirement of soil temperature for the regular processes of ecophysiology. The highest thresholds of SLA in black spruce and WUE in jack pine suggest they are the most sensitive to decreasing soil temperature and may play an important role in the acclimation. The averaged thresholds were at 14.0 and 13.6℃ for black spruce and jack pine, suggesting that the sensitivity of both species to low soil temperature was quite close. 展开更多
关键词 black spruce cubic curvilinear model ecophysiological traits jack pine low soil temperature threshold
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Ice-and cryogel-soil composites in water-retaining elements in embankment dams constructed in cold regions
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作者 N. K. Vasiliev A. A. Ivanov +1 位作者 I. N. Shatalina V. V. Sokurov 《Research in Cold and Arid Regions》 CSCD 2013年第4期444-450,共7页
There are a number of serious problems connected with building and repairing water-reining elements in embankment dams in cold regions. One of them is the difficulty in finding inexpensive clay materials with the nece... There are a number of serious problems connected with building and repairing water-reining elements in embankment dams in cold regions. One of them is the difficulty in finding inexpensive clay materials with the necessary structural properties and using them in the winter. Another is the cracks that appear in the upper part of a dam when the core freezes to the banks, and leakage along the cracks threatens to desWoy the dam. Still another is the process of erosion at the bottom of the core which may occur through fissures in the rock foundation of a dam and in transport constructions. Also, the behaviour of water-retaining elements during eazthquakes is unreliable. All of these problems can be solved by using iceand cryogel-soil composites created by cryotropic gel formation (CGF). Our laboratory investigations demonstrate that the materials proposed for water-retaining elements have the necessary permeable, plastic, thermophysical, and slrength properties to solve all of these problems. Certain consmactious of water-retaining elements which may prove to be both safe and cost-effective are proposed. However, these iceand cryogel-soil composites need to be field-validated before they are used in dams and transport structures in cold regions. 展开更多
关键词 water-retaining elements trasport slructures cold regions cryogel-soil composites polyvinyl alcohol plastic properties
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Biochar-Induced Priming Effects in Young and Old Poplar Plantation Soils 被引量:3
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作者 Weiwei Lu Yirui Zhang +7 位作者 Yixian Yao Yuying Wu Han Y.H.Chen Hailin Zhang Jia Yu Caiqin Shen Qi Liu Honghua Ruan 《Phyton-International Journal of Experimental Botany》 SCIE 2020年第1期13-26,共14页
The priming effect(PE)induced by biochar provides a basis for evaluating its carbon(C)sequestration potential in soils.A 60 days’laboratory incubation was conducted,which involved the amendment of biochar(1%of soil m... The priming effect(PE)induced by biochar provides a basis for evaluating its carbon(C)sequestration potential in soils.A 60 days’laboratory incubation was conducted,which involved the amendment of biochar(1%of soil mass)produced from rice straw at 300℃(B300)and 500℃(B500)to young(Y)and old(O)poplar plantation soils,with the aim of studying the responses of biochar-induced PEs to poplar plantation ages.This incubation included six treatments:Y+CK(control),Y+B300,Y+B500,O+CK,O+B300,and O+B500.Carbon dioxide(CO_(2))emissions were significantly increased(p<0.05)in the B300 amended soils,while it was decreased in the B500 amended soils compared to the CK.The primed CO_(2) emissions were 2.35 times higher in the Y+B300 than the O+B300 treatments,which was measured to be 18.6 and 5.56 mg C·kg^(-1) with relative PEs of 12.4%and 3.35%,respectively.However,there was little difference between the primed CO_(2) emissions in Y+B500 and O+B500 treatments,which were measured to be-24.9 and-29.6 mg·C·kg^(-1) with relative PEs of-16.6%and-17.8%,respectively.Dissolved organic carbon(DOC)was significantly lower in the young poplar plantation soil than that in the old poplar plantation soil regardless of biochar amendment throughout the incubation,indicating greater C-limit of soil microorganisms in the young poplar plantation soil.Using ^(13)C isotope tracing,neither B300 nor B500 decreased native soil-derived DOC,which indicated that the negative B500-induced PEs were not due to a reduction in the availability of native soil-derived C.In conclusion,the response of biochar-induced PEs to poplar plantation age depends on biochar types while soil available C indirectly affects biochar-induced PEs.Further studies should focus on how the interactive effects between soil C availability and microbial community impacts biochar-induced PEs. 展开更多
关键词 BIOCHAR dissolved organic carbon pyrolysis temperature poplar plantation age priming effect
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Automating Transfer Credit Assessment-A Natural Language Processing-Based Approach
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作者 Dhivya Chandrasekaran Vijay Mago 《Computers, Materials & Continua》 SCIE EI 2022年第11期2257-2274,共18页
Student mobility or academic mobility involves students moving between institutions during their post-secondary education,and one of the challenging tasks in this process is to assess the transfer credits to be offere... Student mobility or academic mobility involves students moving between institutions during their post-secondary education,and one of the challenging tasks in this process is to assess the transfer credits to be offered to the incoming student.In general,this process involves domain experts comparing the learning outcomes of the courses,to decide on offering transfer credits to the incoming students.This manual implementation is not only labor-intensive but also influenced by undue bias and administrative complexity.The proposed research article focuses on identifying a model that exploits the advancements in the field of Natural Language Processing(NLP)to effectively automate this process.Given the unique structure,domain specificity,and complexity of learning outcomes(LOs),a need for designing a tailor-made model arises.The proposed model uses a clustering-inspired methodology based on knowledge-based semantic similarity measures to assess the taxonomic similarity of LOs and a transformer-based semantic similarity model to assess the semantic similarity of the LOs.The similarity between LOs is further aggregated to form course to course similarity.Due to the lack of quality benchmark datasets,a new benchmark dataset containing seven course-to-course similarity measures is proposed.Understanding the inherent need for flexibility in the decision-making process the aggregation part of the model offers tunable parameters to accommodate different levels of leniency.While providing an efficient model to assess the similarity between courses with existing resources,this research work also steers future research attempts to apply NLP in the field of articulation in an ideal direction by highlighting the persisting research gaps. 展开更多
关键词 Articulation agreements higher education natural language processing semantic similarity
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Using Statistical Methods for Rock Parameter Identification to Analyse the THM Behaviour of Callovo-Oxfordian Claystone due to Heating
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作者 Michael Jobmann Sha Li +4 位作者 Mirko Polster Michael Breustedt Roger Schlegel Petr Vymlatil JohannesWill 《Journal of Geological Resource and Engineering》 2016年第3期125-136,共12页
In the framework of a heater experiment at the Meuse/Haute-Marne rock laboratory, DBE TECHNOLOGY and Dynardo performed an analysis of the rock behaviour in response to heating. New approaches describing rock permeabil... In the framework of a heater experiment at the Meuse/Haute-Marne rock laboratory, DBE TECHNOLOGY and Dynardo performed an analysis of the rock behaviour in response to heating. New approaches describing rock permeability as a function of stress and plastic strain were used, and statistical methods for parameter identification were applied. The methods comprise automatic sensitivity analysis and optimization algorithms that allow a parameter fitting and an analysis of the importance of individual parameters for the general system development. The identification process resulted in a parameter set that allows a good description of the rock behaviour while being heated. 展开更多
关键词 Claystone parameter identification sensitivity analysis PERMEABILITY pore pressure optimization.
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