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carbon dioxide exchange and biomass productivity of the herbaceous layer of a managed tropical humid savanna ecosystem in western Kenya

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journal of Plant Ecology 2013年第4期6卷 286-297页

作者： G.O.K’Otuto D.O.Otieno B.Seo H.O.Ogindo j.c.onyango Department of Applied Plant Sciences Maseno UniversityPrivate Bag MasenoKenya Department of Plant Ecology University of Bayreuth95440 BayreuthGermany Department of Botany Maseno UniversityPrivate Bag MasenoKenya

Aims Humid savannas,as a result of high precipitation amounts,are highly productive.they are also hotspots for land use change and potential sources of carbon dioxide(cO_(2))due to the large soil carbon(c)stocks.understanding how ecosystem cO_(2) exchange is influenced by changes arising from agricultural land use is vital in future management of these ecosystems and in responding to the ongoing shifts in manage-ment and climate.the aim of this study was to identify how ecosystem cO_(2) exchange and biomass productivity of the herbaceous layer of a humid savanna in Kenya respond to current management practices.Methods We used flux chambers to quantify cO_(2) fluxes,while monthly harvests were undertaken to determine biomass development of the herba-ceous layer of three sites that were(i)fenced to exclude livestock graz-ing,(ii)subjected to grazing by livestock and(iii)abandoned after being cultivated for maize production and also open to grazing by livestock.Important findingsthe peak aboveground biomass ranged between 380 and 1449 g m−2 and biomass production was significantly(Pction(gPP)and net ecosystem cO_(2) exchange(NEE)ranged between 21.8±1.3 to 32.5±2.7 and−9.6±0.7 to−17.9±4.8μmol m−2 s−1,respectively.seasonal NEE fluctuations ranged between 10 and 21μmol m−2s−1,while spatial(among sites)differences ranged between 2 and 10μmol m−2 s−1.Ecosystem respiration(Reco)fluc-tuated between 5 and 10μmol m−2 s−1 during the growing sea-son.Reco was,however,not significantly different among the sites.unlike in other similar ecosystems where ecosystem respiration is determined by the ambient temperature,we did not find any rela-tionship between Reco and temperature in this savanna.Instead,soil moisture accounted for 38-88%of the spatial and seasonal fluc-tuations in ecosystem cO_(2) fluxes and aboveground biomass pro-duction.management influenced the maximum gPP and NEE rates through modification of soil moisture,plant species composition and

关键词： tropical humid savanna abandoned croplands biomass production ecosystem cO_(2)exchange livestock grazing soil water content

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Heat and Mass Transfer for a Nanofluid Flow in Fluidized Bed Dryer in Presence of Induced Magnetic Field

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journal of Applied Mathematics and Physics 2024年第4期12卷 1401-1425页

作者： Kiptum j. Purity Mathew N. Kinyanjui Edward R. onyango Pan African University Institute for Basic Sciences Technology and Innovation Nairobi Kenya Department of Pure and Applied Mathematics Jomo Kenyatta University of Agriculture and Technology Nairobi Kenya

This research entails the study of heat and mass transfer of nanofluid flow in a fluidized bed dryer used in tea drying processes in presence of induced magnetic field. A mathematical model describing the fluid flow in a Fluidized bed dryer was developed using the nonlinear partial differential equations. Due to their non-linearity, the equations were solved numerically by use of the finite difference method. The effects of physical flow parameters on velocity, temperature, concentration and magnetic induction profiles were studied and results were presented graphically. From the mathematical analysis, it was deduced that addition of silver nanoparticles into the fluid flow enhanced velocity and temperature profiles. This led to improved heat transfer in the fluidized bed dryer, hence amplifying the tea drying process. Furthermore, it was noted that induced magnetic field tends to decrease the fluid velocity, which results in uniform distribution of heat leading to efficient heat transfer between the tea particles and the fluid, thus improving the drying process. The research findings provide information to industries on ways to optimize thermal performance of fluidized bed dryers.

关键词： Heat Transfer Induced Magnetic Field Nanofluid Fluidized Bed Dryer

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Semi-analytical investigation of heat transfer in a porous convective radiative moving longitudinal fin exposed to magnetic field in the presence of a shape-dependent trihybrid nanofluid

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Applied Mathematics and Mechanics(English Edition) 2024年第1期45卷 197-216页

作者： c.G.PAVITHRA B.j.GIREESHA M.L.KEERTHI Department of PG Studies and Research in Mathematics Kuvempu UniversityShankaraghatta 577451India Department of Mathematics and Statistics M.S.Ramaiah University of Applied SciencesBengaluru 560058India

The thermal examination of a non-integer-ordered mobile fin with a magnetism in the presence of a trihybrid nanofluid(Fe_3O_4-Au-Zn-blood) is carried out. Three types of nanoparticles, each having a different shape, are considered. These shapes include spherical(Fe_3O_4), cylindrical(Au), and platelet(Zn) configurations. The combination approach is utilized to evaluate the physical and thermal characteristics of the trihybrid and hybrid nanofluids, excluding the thermal conductivity and dynamic viscosity. These two properties are inferred by means of the interpolation method based on the volume fraction of nanoparticles. The governing equation is transformed into a dimensionless form, and the Adomian decomposition Sumudu transform method(ADSTM) is adopted to solve the conundrum of a moving fin immersed in a trihybrid nanofluid. The obtained results agree well with those numerical simulation results, indicating that this research is reliable. The influence of diverse factors on the thermal overview for varying noninteger values of γ is analyzed and presented in graphical representations. Furthermore, the fluctuations in the heat transfer concerning the pertinent parameters are studied. The results show that the heat flux in the presence of the combination of spherical, cylindrical, and platelet nanoparticles is higher than that in the presence of the combination of only spherical and cylindrical nanoparticles. The temperature at the fin tip increases by 0.705 759% when the value of the Peclet number increases by 400%, while decreases by 11.825 13% when the value of the Hartman number increases by 400%.

关键词： convection radiation moving longitudinal fin Adomian decomposition Sumudu transform method(ADSTM) trihybrid nanofluid magnetic field

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Thermoluminescence characterization of natural and synthetic irradiated ce-monazites

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journal of Rare Earths 2024年第4期42卷 643-650页

作者： V.correcher c.Boronat j.Garcia-Guinea j.F.Benavente T.Rivera-Montalvo cIEMAT Av.Complutense 4028040MadridSpain MNcN-cSIc J.Gutierrez Abascal 228006MadridSpain Instituto Politécnico Nacional CICATA-IPNAv.Legaria 694Mexico City11500Mexico

The thermoluminescence(TL)emission of synthetic and natural ce-monazites was characterized here to determine the potential application in the identification of microscopic defects from a qualitative point of view trying to link each TL peak to a chemical-physical process.The kinetic parameters that lead the luminescence processes were calculated by means of variable heating rate and computing glow curve deconvolution methods and allow identifying three groups of components at~90,130 and 290℃(for the mineral sample)and~90,170,220,270 and 320℃(for the synthetic cePO_(4):Nd_(0.20),La_(0.25)).The main differences appreciated in these complex TL curves are mainly due to(i)the content of impurities(natural sample contains lanthanides as well as U 0.60%and Th 5.22%)and(ii)the degree of crystallinity of the samples which is directly related to the type of impurities(synthetic monazite relies only on Nd and La).The behavior of the dose response in the range of 1-8 Gy is similar for both samples;the TL intensity increases linearly as the dose increases without changes in the position of the maxima,denoting first-order kinetic luminescence mechanism.Each peak could be mostly associated with structural defects(i.e.,phase transitions),chemical reactions(i.e.,ce3+?ce4+redox reaction,dehydration or dehydroxylation processes)or intrinsic defects(i.e.,Frenkel defects,ODcs or NBOHcs).

关键词： Thermoluminescence Kineticparameters Phosphate ce-monazite Defects Rare earths

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n-Alkane bound biomarker fingerprints from asphaltenes in the bitumens of Eastern Dahomey Basin,Nigeria:Source and genetic implications

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Petroleum Research 2024年第1期9卷 85-91页

作者： Modupe A.Egbeola Olubunmi c.Adeigbe Olajide j.Adamolekun Department of Geology University of IbadanIbadanNigeria Structural Geology and Tectonics Institute of Applied GeosciencesKIT-Karlsruhe Institute of TechnologyAdenauerring 20a76131KarlsruheGermany

The asphaltene fractions of the bitumens of Eastern Dahomey Basin in Nigeria,were analyzed by flash pyrolysis-gas chromatography(Py-Gc)method in order to unravel its geochemical history and properties.The distributions of the initial biomarkers of the original oils from the pyrolysates are related to the assessment of organic matter source,paleo-redox conditions and source environment during deposition.Also,it effectively establishes the genetic relationship of the bitumens.The n-alkane distributions in the pyrolysates reveal nc_(9)-nc_(32)n-alkanes,maximizing at nc_(14),isoprenoids-pristane(Pr)and phytane(Ph),and some n-alkene peaks.High peaks of low to medium-weight nc_(9)-nc20 n-alkanes and low peaks of nc_(21)+n-alkanes characterize the distributions.These reveal that abundant algal organic matter with some terrigenous inputs contributed to the source rock of the bitumens.The high concentration of marine organic matter inputs to the source rock is further confirmed by the nc_(17)/nc27 ratios which range from 5.39 to 19.82 and shows the predominance of nc_(17)alkanes.The general unimodal n-alkane distributions in the bitumens indicate derivation from similar organic matter types showing that they are genetically related.The anoxic to suboxic environmental conditions that prevailed during the deposition of the sediments is revealed by the isoprenoids,Pr/Ph ratios(0.72-1.28).Pristane/nc_(17)and Phytane/nc_(18)range from 0.16 to 0.33 and 0.22 to 0.56,revealing that the bitumens were from predominantly marine organic matter(type II kerogen)preserved in a reducing environment with no evidence of biodegradation.However,the Ph/nc_(18)ratio and the cross plot of Pr+Ph/nc_(17)+nc_(18)allow the classification of the bitumens into two subfamilies/groups(A and B).The bitumen samples have low wax content as indicated by the degree of waxiness ranging from 0.21 to 0.38 which confirms low terrigenous input.Based on the carbon preference index(cPI:0.92 to 1.55)and odd-even predominance(OEP:0.70 to 1.36),it is concluded that t

关键词： Genetic relationship Flash pyrolysis Biomarker Asphaltene Pyrolysates

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Laser-induced graphene-coated wearable smart textile electrodes for biopotentials signal monitoring

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Frontiers of Materials Science 2024年第1期18卷 95-111页

作者： c.M.Vidhya Yogita Maithani Sakshi Kapoor j.P.Singh Department of Physics Indian Institute of Technology DelhiHauz KhasNew Delhi 110016India

This paper describes how to produce a wearable dry electrode at a reasonable cost and how to use it for the monitoring of biopotentials in electrocardiography.Smart textiles in wearable technologies have made a great advancement in the health care management and living standards of humans.Graphene was manufactured using the low-cost single-step process,laser ablation of polyimide,a commercial polymer.Graphene dispersions were made using solvent isopropyl alcohol which has low boiling point,nontoxicity,and environmental friendliness.After successive coating of the graphene dispersion on the cotton fabric to make it conductive,the sheet resistance of the resulting fabric dropped to 3% of its initial value.The laser-induced graphene(LIG)cotton dry electrodes thus manufactured are comparable to Ag/Agcl wet electrodes in terms of the skin-to-electrode impedance,measuring between 78.0 and 7.2 kΩ for the frequency between 40 Hz and 1 kHz.The LIG cotton electrode displayed a signal-to-noise ratio of 20.17 dB.Due to its comfort,simplicity,and good performance over a longer period of time,the textile electrode appears suited for medical applications.

关键词： biopotential electrocardiogram electromyogram flexible electrode textile porous graphene

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HI in High Gas-phase Metallicity Dwarf Galaxy WISEA j230615.06+143927.9

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Research in Astronomy and Astrophysics 2024年第1期24卷 292-299页

作者： Yan Guo c.Sengupta T.c.Scott P.Lagos Y.Luo Purple Mountain Observatory Chinese Academy of SciencesNanjing 210023China School of Astronomy and Space Sciences University of Science and Technology of ChinaHefei 230026China Institute of Astrophysics and Space Sciences(IA Porto) Rua das Estrelas4150-762PortoPortugal

We present resolved Giant Metrewave Radio Telescope H I observations of the high gas-phase metallicity dwarf galaxy WISEA j230615.06+143927.9(z = 0.005)(hereafter j2306) and investigate whether it could be a Tidal Dwarf Galaxy(TDG) candidate. TDGs are observed to have higher metallicities than normal dwarfs. j2306 has an unusual combination of a blue g-r color of 0.23 mag, irregular optical morphology and high-metallicity(12 +log(O/H) = 8.68 ± 0.14), making it an interesting galaxy to study in more detail. We find j2306 to be an H I rich galaxy with a large extended, unperturbed rotating H I disk. Using our H I data we estimated its dynamical mass and found the galaxy to be dark matter(DM) dominated within its H I radius. The quantity of DM, inferred from its dynamical mass, appears to rule out j2306 as an evolved TDG. A wide area environment search reveals j2306 to be isolated from any larger galaxies which could have been the source of its high gas metallicity. Additionally, the H I morphology and kinematics of the galaxy show no indication of a recent merger to explain the high-metallicity.Further detailed optical spectroscopic observations of j2306 might provide an answer to how a seemingly ordinary irregular dwarf galaxy achieved such a high level of metal enrichment.

关键词： galaxies:abundances galaxies:dwarf galaxies:irregular radio lines:galaxies radio lines:ISM

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Isolating higher yielding and more stable rice genotypes in stress environments: fine-tuning a selection method using production and resilience score indices

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Frontiers of Agricultural Science and Engineering 2024年第1期11卷 169-185页

作者： Arnauld THIRY William j.DAVIES Ian c.DODD Lancaster Environment centre Lancaster UniversityLancasterLancashire LA14YWUK

In Asia, the rice crop sustains millions of people. However, growing demand for this crop needs to be met while simultaneously reducing its water consumption to cope with the effects of climate change. Lowland cropping systems are the most common and productive but have particularly high water requirements. High-yielding rice genotypes adapted to drier environments(such as rainfed or aerobic rice ecosystems) are needed to increase the water use efficiency of cropping. Identifying these genotypes requires fast and more accurate selection methods. It is hypothesized that applying a new quantitative selection method(the score index selection method), can usefully compare rice yield responses over different years and stress intensities to select genotypes more rapidly and efficiently. Applying the score index to previously published rice yield data for 39 genotypes grown in no-stress and two stress environments, identified three genotypes(ARB 8, IR55419-04 and ARB 7) with higher and stable yield under moderate to severe stress conditions. These genotypes are postulated to be better adapted to stress environment such as upland and aerobic environments. Importantly, the score index selection method offers improved precision than the conventional breeding selection method in identifying genotypes that are well-suited to a range of stress levels within the target environment.

关键词： Aerobic rice breeding selection drought resilience production capacity index resilience capacity index stress score index upland

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Mathematical modeling and simulations of stress mitigation by coating polycrystalline particles in lithium-ion batteries

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Applied Mathematics and Mechanics(English Edition) 2024年第6期45卷 947-962页

作者： N.IQBAL j.cHOI S.F.SHAH c.LEE S.LEE Department of Mechanical Roboticsand Energy EngineeringDongguk University-SeoulSeoul 04620Republic of Korea

A chemo-mechanical model is developed to investigate the effects on the stress development of the coating of polycrystalline Ni-rich LiNixMnyco_(z)O_(2)(x>0.8)(NMc)particles with poly(3,4-ethylenedioxythiophene)(PEDOT).The simulation results show that the coating of primary NMc particles significantly reduces the stress generation by efficiently accommodating the volume change associated with the lithium diffusion,and the coating layer plays roles both as a cushion against the volume change and a channel for the lithium transport,promoting the lithium distribution across the secondary particles more homogeneously.Besides,the lower stiffness,higher ionic conductivity,and larger thickness of the coating layer improve the stress mitigation.This paper provides a mathematical framework for calculating the chemo-mechanical responses of anisotropic electrode materials and fundamental insights into how the coating of NMc active particles mitigates stress levels.

关键词： lithium-ion battery(LIB) polycrystalline particle coating finite element simulation Ni-rich LiNixMnyco_(z)O_(2)(x>0.8)(NMc)

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Theoretical and experimental study of a bi-stable piezoelectric energy harvester under hybrid galloping and band-limited random excitations

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Applied Mathematics and Mechanics(English Edition) 2024年第3期45卷 461-478页

作者： Haitao LI Tianyu ZHENG Weiyang QIN Ruilan TIAN Hu DING j.c.jI Liqun cHEN Department of Engineering Mechanics North University of ChinaTaiyuan 030051China Department of Engineering Mechanics Northwestern Polytechnical UniversityXi'an 710072China Department of Engineering Mechanics Shijiazhuang Tiedao UniversityShijiazhuang 050043China Shanghai Key Laboratory of Mechanics in Energy Engineering Shanghai Frontier Science Center of MechnoinformaticsShanghai Institute of Applied Mathematics and MechanicsSchool of Mechanics and Engineering ScienceShanghai UniversityShanghai 200072China School of Mechanical and Mechatronic Engineering University of Technology SydneyNew South Wales 2007Australia

In the practical environment,it is very common for the simultaneous occurrence of base excitation and crosswind.Scavenging the combined energy of vibration and wind with a single energy harvesting structure is fascinating.For this purpose,the effects of the wind speed and random excitation level are investigated with the stochastic averaging method(SAM)based on the energy envelope.The results of the analytical prediction are verified with the Monte-carlo method(McM).The numerical simulation shows that the introduction of wind can reduce the critical excitation level for triggering an inter-well jump and make a bi-stable energy harvester(BEH)realize the performance enhancement for a weak base excitation.However,as the strength of the wind increases to a particular level,the influence of the random base excitation on the dynamic responses is weakened,and the system exhibits a periodic galloping response.A comparison between a BEH and a linear energy harvester(LEH)indicates that the BEH demonstrates inferior performance for high-speed wind.Relevant experiments are conducted to investigate the validity of the theoretical prediction and numerical simulation.The experimental findings also show that strong random excitation is favorable for the BEH in the range of low wind speeds.However,as the speed of the incoming wind is up to a particular level,the disadvantage of the BEH becomes clear and evident.

关键词： bi-stability inter-well response galloping band-limited random

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