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Geochemistry and Sm-Nd systematics of the 1.67 Ga Buanji Group of southwestern Tanzania: Paleo-weathering, provenance and paleo-tectonic setting implications

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Geoscience Frontiers 2017年第5期8卷 1025-1037页

作者： charles H.Kasanzu Makenya A.H.Maboko Shukrani Manya Department of Geology University of Dar es Salaam P.O. Box 35052 Dar es Salaam Tanzania

We present major and trace and Nd-isotopic data of the^1.67 Ga Buanji Group of southwestern Tanzania in order to constrain the nature of their protolith and the intensity of chemical weathering in the source terranes and make inferences on the nature of climatic conditions during the late Paleoproterozoic in the region. Major and trace element contents of the shales from three stratigraphic formations are comparable to those of the post-Archaean Australian Shale(PAAS) and the average Proterozoic Shale(PS). They are characterized by enrichments in LREE relative to HREE((La/Yb)_(CN)=9.07-13.2;(Gd/Yb)cN = 1.51-1.85) and negative Eu anomalies(Eu/Eu~* = 0.61-0.81); features which are comparable to those of PAAS and PS, indicating upper continental sources. Provenance proxy ratios,together with abundances of Cr, Ni, Co and V that increase up-stratigraphy suggest a decreasing input of felsic detritus up-stratigraphy. Chemical Indices of Alteration(CIA) for the lower, middle and upper Buanji formations are 81. 76 and 79, respectively. These indices largely indicate intermediate(ca. 60-80)to extreme(>80) weathering intensities of the precursor rocks. These observations may suggest the prevalence of warm, humid climates during the late Paleoproterozoic in the *** lower Buanji Formation yielded a depleted mantle Nd model age(T_(DM)) of 、2100 Ma which indicates an Eburnean parentage. T_(DM) ages of 2486-2155 Ma and 2535-2379 Ma obtained from middle and upper Buanji formations, respectively, suggest a progressive increase of sedimentary input from the Tanzania Craton up-stratigraphy. The Eburnean T_(DM) ages of the lower Buanji rocks are attributed to their derivation through denudation of a decaying topographic high composed predominantly of rocks that were generated during the Palaeoproterozoic Ubendian orogenesis, possibly in the realm of Columbian Supercontinent assembly. Overlapping T_(DM) ages between the middle and upper Buanji formations suggest multiple sources i

关键词： Buanji Group Shales Source weathering conditions Provenance

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Palatability and profitability of co-occurring seeds alter indirect interactions among rodent-dispersed trees

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Integrative Zoology 2022年第2期17卷 206-216页

作者： Zhishu XIAO Marcel HOLYOAK charles J.KREBS Xiaoqun HUANG State Key Laboratory of Integrated Management of Pest Insects and Rodents in Agriculture Institute of ZoologyChinese Academy of SciencesChina University of Chinese Academy of Sciences BeijingChina Department of Environmental Science and Policy University of CaliforniaDavisUSA Department of Zoology University of British ColumbiaVancouverCanada

Beyond direct species interactions,seed dispersal is potentially affected by indirect seed–seed interactions among co-occurring nut-bearing trees which are mediated by scatter-hoarding animals as shared seed dispersers.A relevant question in such systems is to what extent different functional traits related to food palatability and profitability affect the kinds of indirect interactions that occur among co-occurring seeds,and the consequences for seed *** used field experiments to track seed dispersal with individually tagged seeds in both monospecific and mixed seed *** measured indirect effects based on 3 seed–seed species pairs from the family Fagaceae with contrasting seed size,tannin level,and dormancy in a subtropical forest in Southwest *** all else was equal,the presence of adjacently placed seeds with contrasting seed traits created different indirect effects measured through a variety of dispersal-related *** mutualism was reciprocal due to increasing seed dispersal in mixed seed patches with mixed differences in seed tannins and ***,differences in either seed size or dormancy in co-occurring adjacently placed seeds caused apparent competition with reduced seed removal or seed dispersal(distance)in at least one *** study supports the hypothesis that different functional traits related to food palatability and profitability in co-occurring seeds modify foraging decisions of scatter-hoarding animals,and subsequently cause indirect effects on seed dispersal among rodent-dispersed *** conclude that such indirect effects mediated by shared seed dispersers may act as an important determinant of seed dispersal for co-fruiting animal-dispersed trees in many natural forests.

关键词： dispersal distance functional trait scatter-hoarding rodents seed dispersal trait-mediated indirect interactions

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Structure of [Co(im)6]SiF6：Short Hydrogen Bonds Involving SiF62- Ions

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Chinese Journal of Structural Chemistry 2017年第6期36卷 965-970页

作者： NAZIR Sadia ARIF Muhammad RASHID Muhammad Abid WHITWOOD Adrian charles Department of Chemistry Govt. College Women University Faisalabad 3800 Pakistan Institute of Chemical Sciences Bahhauddin Zakariya University Multan 60800 Pakistan Department of Chemistry University of Agriculture Faisalabad 38040 Pakistan Department of Chemistry University of York Heslington York YO10 5DD UK

A new complex C（18）H（24）CoF6N（12）Si has been synthesized by the reaction of cobalt（II） fluoride tetrahydrate with imidazole in a glass vessel. SiF62-was generated by in situ reaction of fluoride on silica. This complex has been characterized by different techniques such as elemental analysis, IR studies, magnetic measurements, electronic absorption measurements and single-crystal X-ray structure determination. The crystals are hexagonal in the R-3 space group, with a = 13.225（6）, b = 13.225（6）, c = 12.517（11） A, and g = 120°. In complex [Co（im）6]SiF6, the cobalt atom is six-coordinated to adopt a regular octahedral geometry and the SiF62-ion acts as the counter anion. The crystal displays a network structure and SiF62- bridging hexagram formation by N-（39）···F-Si interactions between imdazole and SiF62-. SiF62-plays an important role in assembling the supramolecular aggregates.

关键词： anion binding imidazole SiF62- hydrogen bonds transitionmetal fluoride complexes

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Investigation of active vibration drilling using acoustic emission and cutting size analysis

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Journal of Rock Mechanics and Geotechnical Engineering 2018年第2期10卷 390-401页

作者： Yingjian Xiao charles Hurich John Molgaard Stephen D.Butt Faculty of Engineering and Applied Science Memorial University of Newfoundland Department of Earth Sciences Memorial University of Newfoundland

This paper describes an investigation of active bit vibration on the penetration mechanisms and bit-rock interaction for drilling with a diamond impregnated coring bit. A series of drill-off tests(DOTs) were conducted where the drilling rate-of-penetration(ROP) was measured at a series of step-wise increasing static bit thrusts or weight-on-bits(WOBs). Two active DOTs were conducted by applying 60 Hz axial vibration at the bit-rock interface using an electromagnetic vibrating table mounted underneath the drilling samples, and a passive DOT was conducted where the bit was allowed to vibrate naturally with lower amplitude due to the compliance of the drilling sample mountings. During drilling, an acoustic emission(AE) system was used to record the AE signals generated by the diamond cutter penetration and the cuttings were collected for grain size analysis. The instrumented drilling system recorded the dynamic motions of the bit-rock interface using a laser displacement sensor, a load cell, and an LVDT(linear variable differential transformer) recorded the dynamic WOB and the ROP, respectively. Calibration with the drilling system showed that rotary speed was approximately the same at any given WOB, facilitating comparison of the results at the same WOB. Analysis of the experimental results shows that the ROP of the bit at any given WOB increased with higher amplitude of axial bit-rock vibration, and the drill cuttings increased in size with a higher ROP. Spectral analysis of the AEs indicated that the higher ROP and larger cutting size were correlated with a higher AE energy and a lower AE frequency. This indicated that larger fractures were being created to generate larger cutting size. Overall, these results indicate that a greater magnitude of axial bit-rock vibration produces larger fractures and generates larger cuttings which, at the same rotary speed, results in a higher ROP.

关键词： Active bit vibration Diamond coring drilling Drill-off tests(DOTs) Acoustic emission(AE) Drilling performance Penetration mechanism Cutting size analysis

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An Ensemble-Based Hotel Reviews System Using Naive Bayes Classifier

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Computer Modeling in Engineering & Sciences 2023年第10期137卷 131-154页

作者： Joseph Bamidele Awotunde Sanjay Misra Vikash Katta Oluwafemi charles Adebayo Department of Computer Science Faculty of Information and Communication SciencesUniversity of IlorinIlorin240003Nigeria Department of Computer Science and Communication Otfold University CollegeHaldenNorway

The task of classifying opinions conveyed in any form of text online is referred to as sentiment *** emergence of social media usage and its spread has given room for sentiment analysis in our daily *** media applications and websites have become the foremost spring of data recycled for reviews for sentimentality in various *** subject matter can be encountered on social media platforms,such as movie product reviews,consumer opinions,and testimonies,among others,which can be used for sentiment *** rapid uncovering of these web contents contains divergence of many benefits like profit-making,which is one of the most vital of them *** to a recent study,81%of consumers conduct online research prior to making a *** the reviews available online are too huge and numerous for human brains to process and ***,machine learning classifiers are one of the prominent tools used to classify sentiment in order to get valuable information for use in companies like hotels,game companies,and so *** the sentiments of people towards different commodities helps to improve the services for contextual promotions,referral systems,and market ***,this study proposes a sentiment-based framework detection to enable the rapid uncovering of opinionated contents of hotel reviews.A Naive Bayes classifier was used to process and analyze the dataset for the detection of the polarity of the *** dataset from Datafiniti’s Business Database obtained from Kaggle was used for the experiments in this *** performance evaluation of the model shows a test accuracy of 96.08%,an F1-score of 96.00%,a precision of 96.00%,and a recall of 96.00%.The results were compared with state-of-the-art classifiers and showed a promising performance andmuch better in terms of performancemetrics.

关键词： Sentiment analysis hotel reviews Naive Bayes algorithm consumer opinions web 2.0 machine learning

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Nematode distribution in cultivated and undisturbed soils of Guinea Savannah and Semi-deciduous Forest zones of Ghana

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Geoscience Frontiers 2019年第2期10卷 381-387页

作者： Obed Asiedu charles Kodia Kwoseh Haddish Melakeberhan Thomas Adjei-Gyapong Kwame Nkrumah University of Science and Technology Michigan State University

Climate change affects air temperature, sea levels as well as the soil and its ecosystem. The Guinea Savannah and Semi-deciduous Forest zones of Ghana are characterized by different climatic conditions and vegetative cover. Annual average temperature has been steadily increasing whilst annual total rainfall has been decreasing in both zones, and this has been causing a southward shift of the Savannah into the Forest zone. Soil organisms provide crucial ecosystem services which are required for sustainable agriculture and food production yet crop cultivation disturbs the soil ecosystem. The harsh conditions associated with the Savannah further expose the soil ecosystem to disturbance and loss of biodiversity which threatens food production and security. Soil nematodes are the most abundant animals in the soil and play a central and critical role in the soil food web complex. Studying the nematode community structure gives a reflection of the status of the entire soil ecosystem. Soil samples were taken from cultivated and natural landscapes in the Guinea Savannah and Semi-deciduous Forest agroecological zones to analyse the nematode community. Results from the study showed the Guinea Savannah zone recording warmer soil temperatures, lower organic matter percentage and lower nematode diversity(Genus Richness) as compared to the Semi-deciduous Forest zone. If the Savannah continues to shift southward, the Forest zone soil ecosystem risks disturbance and loss of biodiversity due to the harsh Savannah conditions. Our findings indicate that prevailing crop cultivation practices also disturb soil ecosystem in the two ecological zones which span across West Africa. A disturbed soil ecosystem endangers the future of food production and food security.

关键词： Climate change Guinea Savannah Semi-deciduous Forest Soil temperature Soil nematode diversity

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Design of Oxygen Electrocatalysts Based on Biomass/MOF Derived Carbon Frameworks

Design of Oxygen Electrocatalysts Based on Biomass/MOF Deriv...

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作者： Victor charles 中国科学院大学(中国科学院过程工程研究所)

学位级别：硕士

电化学能源转换被视为解决当前全球能源危机的替代方法。这一过程由包括ORR,OER和HER在内的各种反应驱动。由于4个电子质子的转移反应过程,ORR和OER一直是这些过程面临的重要挑战。为了实现这些过程的广泛应用,必须合成能够有效驱动氧... 详细信息

电化学能源转换被视为解决当前全球能源危机的替代方法。这一过程由包括ORR,OER和HER在内的各种反应驱动。由于4个电子质子的转移反应过程,ORR和OER一直是这些过程面临的重要挑战。为了实现这些过程的广泛应用,必须合成能够有效驱动氧反应（ORR和OER）的廉价且丰富的电催化剂,这对于设计用于增强氧还原反应（ORR）和析氧反应（OER）的电催化剂对于诸如燃料电池,水分解和金属空气电池装置之类的能量转换系统至关重要。首先,通过掺入过渡金属合金和富氮小分子,利用一种烟梗这一廉价的生物质来制备新型多孔碳骨架（NiCo@N-C）。所得催化剂在碱性介质中的对氧还原反应提供了 0.92V的起始电势和0.86V的半波电势,优于市售的Pt/C催化剂。此外,该催化剂还表现出良好的析氧反应性能,具有280mV@10mA cm2的低过电势,ORR和OER之间的电势差仅为0.65V。掺入的NiCo合金和N杂原子调节了制备的碳骨架的电子结构,创建了丰富的活性位点,并改善了电荷的重新分布,因此导致更快的ORR和OER反应动力学。所制备的NiCo@N-C应用于Zn-空气电池的空气阴极,表现出良好的性能。这项工作为开发用于能源应用的高效多孔和功能化生物质衍生的氧电催化剂提供了一条新的思路。其次,通过超声浸渍法将CoOx和NiO纳米颗粒掺入Ui0-66 MOF的框架中,并在300℃下煅烧,以形成具有Ui0-66框架结构的CoOx/Ui066-300和NiO/Ui0-66-300异质结构。对合成材料的OER性能进行了研究,与NiO/Ui0-66-300和Ui0-66相比,CoOx/Ui0-66-300和Ui0-66的过电势较低,分别为291.6mV和416.6 mV。在550℃下对浸渍的纳米粒子进行热处理时,Ui066骨架坍塌,导致异质结构的OER性能下降。这项工作提供了一种通过合理设计异质结构来提高Co和Ni基材料的OER性能的新方法。

关键词：金属空气电池能量转换析氧反应性能

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STUDY OF CRYSTAL GROWTH AND SOLUTE PRECIPITATION THROUGH FRONT TRACKING METHOD

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Acta Mathematica Scientia 2010年第2期30卷 377-390页

作者： Xiaolin Li James Glimmi Xiangmin Jiao charles Peyser Yanhong Zhao Department of Applied Mathematics and Statistics Stony Brook University Stony Brook NY 11794 USA Computational Science Center Brookhaven National Laboratory Upton NY 11793 USA North Shore Hebrew Academy High School Great Neck NY 11020 USA

Crystal growth and solute precipitation is a Stefan problem. It is a free boundary problem for a parabolic partial differential equation with a time-dependent phase interface. The velocity of the moving interface between solute and crystal is a local function. The dendritic structure of the crystal interface, which develops dynamically, requires high resolution of the interface geometry. These facts make the Lagrangian front tracking method well suited for the problem. In this paper, we introduce an upgraded version of the front tracking code and its associated algorithms for the numerical study of crystal formation. We compare our results with the smoothed particle hydrodynamics method （SPH） in terms of the crystal fractal dimension with its dependence on the Damkohler number and density ratio.

关键词： front tracking crystal formation fractal dimension

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Finite Element Analysis of Recycled Aggregate Concrete in Freeze/Thaw Condition Using Ansys

Finite Element Analysis of Recycled Aggregate Concrete in Fr...

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作者： Kahanji charles 武汉理工大学

学位级别：硕士

有很问题与拆毁的建筑物中的废物处理有关。为了解决这个问题,可以把从废物中回收的混凝土用到其它的工程中。这项研究涉及到在经受冷冻融化的气候条件下的回收混凝土骨料的混凝土结构物。我们从先前的试验中得出来的有关素混凝土冷冻... 详细信息

有很问题与拆毁的建筑物中的废物处理有关。为了解决这个问题,可以把从废物中回收的混凝土用到其它的工程中。这项研究涉及到在经受冷冻融化的气候条件下的回收混凝土骨料的混凝土结构物。我们从先前的试验中得出来的有关素混凝土冷冻融化的结果已经做过关于有限元的分析。从以前的实验中能够得知得出：与天然骨料制成的混凝土相比,由再生骨料制成的混凝土强度相对较低。因此,在易经受冷冻融化的地区中对由循环再生骨料制成的混凝土结构进行详细的研究是很有必要的。从受冷冻或融化角度建立的数学模型没有好的发展。而这个模型做到了,从原则上来讲,判定出基于应力,由于冷冻原因在坚固的混凝土结构物上产生的裂缝是可行的。差分方程的解决需要运用有限元分析。由可循环骨料制成的未经过加固的混凝土的分析模型是基于以前可用的试验数据的基础之上的。使用ANSYS的常规有限元分析程序进行三维有限元分析并将其结果与试验结果对比,在有限元模型中输入基于试验的结果数据。使用ANSYS分析的结果与前实验结果相比吻合较好。

关键词： ANSYS 混凝土有限元冷冻/冻融可循环骨料

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Women and youths participation in agroforestry:What counts and what doesn’t around Mount Elgon,Uganda?

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Journal of Mountain Science 2021年第12期18卷 3306-3320页

作者： GALABUZI charles AGABA Hillary OKIA Clement Akias ODOUL Judith MUTHURI Catherine National Forestry Resources Research Institute(NaFORRI) Kampala 1752Uganda National Agricultural Research Organization(NARO) Entebbe 295Uganda World Agroforestry Uganda Country OfficeKampala 2641Uganda World Agroforestry United Nations AvenueNairobi 30677Kenya Department of Environmental Sciences Muni UniversityArua 725Uganda

The increase in global climate change incidents is a glaring indication that more pragmatic and direct approaches to tree and forest management are urgently needed.A study was conducted around Mount Elgon Uganda between June 2018 and December *** objectives were to:i)determine the socio-economic characteristics of women and youth farmers engaged in agroforestry,ii)determine the relationship between women and youth farmers’characteristics in adoption of tree technologies and related decisions,and iii)assess the incentives,challenges and strategies for promoting agroforestry technologies’adoption in the *** were collected from 250 women and youths using focus group discussions,semi-structured,and key informant *** showed that engagements in agroforestry practices attracted largely(82%)of uneducated women and youths and basic methods and tools were used to *** to 70%of women and youth relied on crop farming as a major source of income,earning about USD$250 *** and family size were positively(P>0.0001)related to tree adoption decisions while farmer capacity building activities(such as training,farmer guided field tours,and participatory farmer trial’s establishments)and access to low-cost tree seedlings motivated their involvement in tree *** scarcity,soil,water,and tree conservation issues and shortage of desired tree species affected the extent of tree growing in both women and youth-led *** suggested strategies comprised strengthening farmer capacity-building programs and upholding soil and water conservation *** has the potential to address the challenges related to land scarcity and shortage of desired tree products in women and youth-led households around Mount ***,the women and youths involved in farming activities were generally poor,illiterate and faced issues of land *** factors,limited their full potential and interest in agroforestry.A significant incr

关键词： Agroforestry trees Farmer decisions Farmer participation Livelihoods East African highlands

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