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open Journal of Microphysics 2024年第1期14卷 1-12页

作者： Phillip Wilfsen otieno Nyawere Department of Physical and Biological Sciences Kabarak University Nakuru Kenya

An analysis of mechanical, electronic and dynamical properties of antiperovskite Ca3Bo (B = Pb, ge, Sn) in cubic phase space group Pm-3m (221) has been studied using first principle density functional theory (DFT). Ground state energy computation was done using the Projector Augmented Wave (PAW) Pseudo Potentials and the Plane Wave (PW) basis set. The generalized Gradient Approximation (GGA) was used for the exchange correlation. The open source code QUANTUM ESPRESSo (QE) was used in this study in which plane wave basis sets are applied for the expansion of the electronic structure wave function. Thermo_pw as a post-processing code was used for the computation of mechanical properties including bulk modulus and elastic constants with their derivatives. The lattice parameters are here calculated to be 4.87 Å, 4.86 Å and 4.84 Å for Ca3Bo (B = Pb, ge, Sn) respectively which compares well with other works. This also shows that the three crystals are similar in size and in most of their properties. In addition to this, projected density of states and band structure are also computed both showing that these materials are of semi-metallic nature and are stable in cubic phase. Phonon modes at gamma are also reported.

关键词： Antiperovskite Elastic Constants generalized Gradient Approximation

Preparation and Alkylation of Carbon Nanofibers from Polymethyl Methacrylate

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Journal of Materials Science and Chemical Engineering 2024年第9期12卷 55-68页

作者： Stephen Mukhebi Situma geoffrey otieno Austin o. Aluoch Dickson M. Andala James owour School of Chemistry and Material Science Technical University of Kenya Haile Selassie Avenue Nairobi Kenya Chemistry Department Multi-Media University Nairobi Kenya

Carbon nanofibers have revolutionized nanotechnology due to their potential applications in emerging frontiers of research and industrial sectors. This can be attributed to their superior properties such as higher mechanical strength, unique surface characteristics, and improved adherence that is transmitted into the polymer matrix to form a nanocomposite with improved properties. Polymethyl methacrylate is a common carbon source for the synthesis of carbon nanofibres of its high mechanical strength, thermal stability, and low moisture and water absorbing capacity that allows its products to have several applications. In this work, we report the successful electrospinning of carbon nanofibres from Poly methyl methacrylate and functionalizing the resulting carbon nanofibres. The functionalized carbon nanofibres were analyzed to determine their solubility/dispersion in selected organic solvents, then characterized using Fourier transform infra-red spectroscopy, Raman spectroscopy, scanning electron microscopy combined with Energy dispersive spectroscopy and Thermalgravimetric analysis.

关键词： Polymethyl Methacrylate Electrospinning Carbon Nanofibres Alkylation

Interactive influence of rainfall manipulation and livestock grazing on species diversity of the herbaceous layer community in a humid savannah in Kenya

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Plant Diversity 2019年第3期41卷 198-205页

作者： Joseph o.ondier Daniel o.okach John C.onyango Dennis o.otieno Department of Botany Maseno University Private Bag Maseno Kenya Department of Biological Sciences Jaramogi Oginga Odinga University of Science and Technology P.O Box 210-40601 Bondo Kenya Department of Plant Ecology University of Bayreuth D-95440 Bayreuth Germany

Changes in rainfall regime and grazing pressure affect vegetation composition and diversity with ecological implications for savannahs. The savannah in East Africa has experienced increased livestock grazing and rainfall variability but the impacts associated with those changes on the herbaceous layer have rarely been documented. We investigated the effect of livestock grazing, rainfall manipulation and their interaction on the composition and diversity of the herbaceous community in the savannah for two years in Lambwe, Kenya. Rainfall manipulation plots were set up for vegetation sampling;these plots received either 50% more or 50% less rainfall than control plots. Simpson’s diversity and Bergere Parker indices were used to determine diversity changes and dominance respectively. The frequency of species was used to compute their abundance and their life forms as determined from the literature. Grazing significantly increased species diversity through suppression of dominant species. Rainfall manipulation had no significant impact on plant diversity in fenced plots, but rainfall reduction significantly reduced diversity in grazed plots. In contrast, rainfall manipulation had no impact on dominance in either fenced or grazed plots. The interaction of grazing and rainfall manipulation is complex and will require additional survey campaigns to create a complete picture of the implications for savannah structure and composition.

关键词： Plant diversity Grazing Rainfall Moist savannah

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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 *** are also hotspots for land use change and potential sources of carbon dioxide(Co_(2))due to the large soil carbon(C)*** 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 *** 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 *** 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 *** findingsthe peak aboveground biomass ranged between 380 and 1449 g m−2 and biomass production was significantly(Power in the grazed and abandoned *** maximum gross primary production(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,*** NEE fluctuations ranged between 10 and 21μmol m−2s−1,while spatial(among sites)differences ranged between 2 and 10μmol m−2 s−*** respiration(Reco)fluc-tuated between 5 and 10μmol m−2 s−1 during the growing *** was,however,not significantly different among the *** 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 ***,soil moisture accounted for 38-88%of the spatial and seasonal fluc-tuations in ecosystem Co_(2) fluxes and aboveground biomass *** influenced the maximum gPP and NEE rates through modification

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

Revealing a Transformation-Induced Plasticity(TRIP)Phenomenon in a Medium-Entropy Alloy

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Acta Metallurgica Sinica(English Letters) 2020年第8期33卷 1159-1165页

作者： Ibrahim ondicho Bernard Alunda Dicken owino Luke otieno Melody Chepkoech Department of Mechanical Engineering Dedan Kimathi University of TechnologyPrivate Bag-10143NyeriKenya Materials Design and Manufacturing(MADEMA)GroupDedan Kimathi University of TechnologyPrivate Bag-10143Dedan KimathiNyeriKenya Department of Advanced Root Industry Engineering Yuengnam UniversityGyeongsanSouth Korea Department of Mining and Minerals Processing Engineering Taita Taveta UniversityP.O.Box 635-80300VoiKenya Department of Mechanical Engineering Inha UniversityIncheonSouth Korea School of Mechanical Engineering Kyungpook National UniversityDaeguSouth Korea Department of Mechanical Engineering Howard UniversityWashingtonDCUSA

A transformation-induced plasticity phenomenon in Fe65(CoCrMnNi)35 medium-entropy alloy was *** to the X-ray diffraction patterns,the as-cast specimen contains a single-phase face-centered cubic(fcc),while low-temperature annealing at 500℃and 600℃leads to the introduction of a body-centered cubic(bcc)phase as a secondary *** increment of the annealing temperature to above 700℃eliminates the bcc phase,and the microstructure was found to contain a single-phase *** 20%true strain,an fcc-to-bcc phase transformation is observed;whereas,at 28%true strain,an fccto-hcp phase transformation takes place as an additional deformation *** strain-induced phase transformation phenomenon leads to improved tensile properties of this alloy.

关键词： Phase transformation X-ray diffraction Mechanical behavior Microstructure evolution Multicomponent alloys

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Greenhouse gas emission and its potential mitigation process from the waste sector in a large-scale exhibition

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Journal of Environmental Sciences 2015年第5期27卷 44-50页

作者： Ziyang Lou Bernd Bilitewski Nanwen Zhu Xiaoli Chai Bing Li Youcai Zhao Peter otieno School of Environmental Science and Engineering Shanghai Jiaotong University Institute for Waste Management and Contaminated Sites Treatment TU Dresden Faculty of Forestry Geo and Hydro SciencesPratzschwitzer Str.1501796 Pirna Germany State Key Laboratory of Pollution Control and Resource Reuse School of Environmental Science and Engineering Tongji University Institute of Ecological Chemistry Helmholtz Zentrum Müenchen German National Research Centre for Environmental HealthIngolst?dter Landstrasse 1D-85764 Neuherberg Germany Maseno University Department of Chemistry

As one of the largest human activities, World Expo is an important source of anthropogenic Greenhouse Gas emission（GHG）, and the GHG emission and other environmental impacts of the Expo Shanghai 2010, where around 59,397 tons of waste was generated during 184 Expo running days, were assessed by life cycle assessment（LCA）. Two scenarios, i.e., the actual and expected figures of the waste sector, were assessed and compared, and 124.01 kg Co2-equivalent（Co2-eq.）, 4.43 kg So2-eq., 4.88 kg No-3-eq., and 3509 m3 water per ton tourist waste were found to be released in terms of global warming（GW）, acidification（AC）,nutrient enrichment（NE） and spoiled groundwater resources（SGWR）, respectively. The total GHG emission was around 3499 ton Co2-eq. from the waste sector in Expo Park, among which 86.47% was generated during the waste landfilling at the rate of 107.24 kg Co2-eq.,and CH4, Co and other hydrocarbons（HC） were the main contributors. If the waste sorting process had been implemented according to the plan scenario, around 497 ton *** could have been attained. Unlike municipal solid waste, with more organic matter content, an incineration plant is more suitable for tourist waste disposal due to its high heating value, from the GHG reduction perspective.

关键词： GHG emission Mitigation process Waste sector Expo 2010 Shanghai Life cycle assessment

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Estimation of Finite Population Totals in High Dimensional Spaces

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open Journal of Statistics 2022年第5期12卷 581-596页

作者： Festus A. Were george o. orwa Romanus o. otieno Department of Statistics and Actuarial Sciences JKUAT Nairobi Kenya

In this paper, the problem of Nonparametric Estimation of Finite Population Totals in high dimensional datasets is considered. A robust estimator of the Finite Population Total based on Feedforward Backpropagation Neural Network is derived with the aid of a Super-Population Model. This current study is motivated by the fact that Local Polynomials and Kernel methods have in preceding related studies, been shown to provide good estimators for Finite Population Totals but in low dimensions. Even in these situations however, bias at boundary points presents a big challenge when using these estimators in estimating Finite Population parameters. The challenge worsens as the dimension of regressors increase. This is because as the dimension of the Regressor Vectors grows, the Sparseness of the Regressors’ values in the design space becomes unfeasible, resulting in a decrease in the fastest achievable rates of convergence of the Regression Function Estimators towards the target curve, rendering Kernel Methods and Local Polynomials ineffective to address these challenges. This study considers the technique of Artificial Neural Networks which yields robust estimators in high dimensions and reduces the estimation bias with marginal increase in variance. This is due to its Multi-Layer Structure, which can approximate a wide range of functions to any required level of precision. The estimator’s properties are developed, and a comparison with existing estimators was conducted to evaluate the estimator’s performance using real data sets acquired from the United Nations Development Programme 2020. The estimation approach performs well in an example using data from a United Nations Development Programme 2020 on the study of Human Development Index against other factors. The theoretical and practical results imply that the Neural Network estimator is highly recommended for survey sampling estimation of the finite population total.

关键词： Neural Networks Kernel Smoother Local Polynomial Nonparametric

APPLICATIoN oF THE TRRL FLooD ESTIMATIoN MoDEL IN HYDRoLoGICAL FoRECASTING FoR CATCHMENTS WITH LIMITED DATA-A CASE STUDY

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International Journal of Sediment Research 1998年第4期 74-84页

作者： otieno,F.A.o 1 and KIBATA,N. 2

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关键词： Flood forecasting Environmental hydrology Catchment studies Rational method Conceptual flood modelling

one-Sample Bayesian Predictive Analyses for a Nonhomogeneous Poisson Process with Delayed S-Shaped Intensity Function Using Non-Informative Priors

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open Journal of Statistics 2023年第5期13卷 717-733页

作者： otieno Collins orawo Luke Akong’o Matiri george Munene Department of Mathematics Egerton University Egerton Kenya

The delayed S-shaped software reliability growth model (SRGM) is one of the non-homogeneous Poisson process (NHPP) models which have been proposed for software reliability assessment. The model is distinctive because it has a mean value function that reflects the delay in failure reporting: there is a delay between failure detection and reporting time. The model captures error detection, isolation, and removal processes, thus is appropriate for software reliability analysis. Predictive analysis in software testing is useful in modifying, debugging, and determining when to terminate software development testing processes. However, Bayesian predictive analyses on the delayed S-shaped model have not been extensively explored. This paper uses the delayed S-shaped SRGM to address four issues in one-sample prediction associated with the software development testing process. Bayesian approach based on non-informative priors was used to derive explicit solutions for the four issues, and the developed methodologies were illustrated using real data.

关键词： Failure Intensity Non-Informative Priors Software Reliability Model Bayesian Approach Non-Homogeneous Poisson Process

Robust Classification through a Nonparametric Kernel Discriminant Analysis

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open Journal of Statistics 2022年第4期12卷 443-455页

作者： Macdonald G. obudho george o. orwa Romanus o. otieno Festus A. Were Department of Statistics and Actuarial Sciences Jomo Kenyatta University of Agriculture and Technology Nairobi Kenya

The problem of classification in situations where the assumption of normality in the data is violated, and there are non-linear clustered structures in the dataset is addressed. A robust nonparametric kernel discriminant classification function, which is able to address this challenge, has been developed and the misclassification rates computed for various bandwidth matrices. A comparison with existing parametric classification functions such as the linear discriminant and quadratic discriminant is conducted to evaluate the performance of this classification function using simulated datasets. The results presented in this paper show good performance in terms of misclassification rates for the kernel discriminant classifier when the correct bandwidth is selected as compared to other identified existing classifiers. In this regard, the study recommends the use of the proposed kernel discriminant classification rule when one wishes to classify units into one of several categories or population groups where parametric classifiers might not be applicable.

关键词： Discriminant Analysis Kernel Discriminant Nonparametric