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Land Use and Land Cover Dynamics in the Eseka Alluvial Gold Mining District, Centre Region, Cameroon

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Journal of Geographic Information System 2024年第4期16卷 289-305页

作者： Shu Vejiline Lum-Ndob Fonge Beatrice Ambo Ambe Godlove Neba Ateh Kevin Ijunghi Enerst Tata Cheo Emmanuel Suh depart.ent of Plant science Faculty of Science University of Buea Buea Cameroon depart.ent of Mining and Mineral Engineering National Higher Polytechnic Institute The University of Bamenda Bambili Cameroon Economic geology Unit Department of Geology Faculty of Science University of Buea Buea Cameroon depart.ent of geology Mining and Environmental Science The University of Bamenda Bambili Cameroon

Local populations in Cameroon thrive on forest resources and the flow of ecosystem services they provide are pivotal in sustaining national economy, improving people’s lives, safeguarding biodiversity, and mitigating the impacts of environmental changes. The exploitation of these resources invariably leads to deforestation and forest degradation. This study was designed to evaluate land use land cover change (LULCC) in the Eseka alluvial gold mining district with the aid of Landsat images. In the investigation of forest cover change, four Landsat satellite images for (1990, 2002, 2015 and 2022) were used. Ground-truthing also helped to identify the activities carried out by the local population and to determine agents, drivers and pressures of land use and land cover change. Four main land cover classes namely: forest, agricultural land, settlement/mining camps and water bodies were selected. Between 1990 and 2022, the proportion of forest decreased from 98% to 34% while those of agricultural land and settlement/mining camps increased from 2% to 60% and 0.54% to 6% respectively. Analysis showed ongoing deforestation with forest cover loss of ~98,263 ha in 32 years giving a cover change percentage of 63.94%. Kappa coefficient for the study period ranged from 0.92 to 0.99. Forest cover loss could be attributed to farming activities, wood extraction and alluvial gold mining activities. Economic motives notably the need to increase household income from a frequent demand for farm and wood products in neighbouring towns and the quest for gold were the main drivers of these activities. Hence, this study assesses the impact of human activities from the mining sector on the forest ecosystem in a bid to inform mitigation policies.

关键词： Land Use and Land Cover Changes Biodiversity Alluvial Gold Mining Drivers Landsat Images Ground-Truthing Mitigation

Frequency-tunable single-photon router based on a microresonator containing a driven three-level emitter

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Chinese Physics B 2024年第6期33卷 377-381页

作者：黄劲松胡菁兰李艳玲徐中辉 School of Information Engineering Jiangxi University of Science and TechnologyGanzhou 341000China faculty of science Jiangxi University of Science and TechnologyGanzhou 341000China

We propose a frequency-tunable router of single photons with high routing efficiency, which is constructed by two waveguides mediately linked by a single-mode whispering gallery resonator with a driven three-level emitter. Quantum routing probability in the output port is obtained via the real-space Hamiltonian. By adjusting the resonator–emitter coupling and the drive, the desired continuous central frequencies for the resonance peaks of routing photons can be manipulated nearly linearly, with the assistance of Rabi splitting effect and optical Stark shift. The proposed routing system may provide potential applications in designing other frequency-modulation quantum optical devices, such as multiplexers,filters, and so on.

关键词： quantum routing scattering theory optical waveguide microresonator

A comparative study for petroleum removal capacities of the bacterial consortia entrapped in sodium alginate,sodium alginate/poly(vinyl alcohol),and bushnell haas agar

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Petroleum science 2024年第1期21卷 705-715页

作者： Sezen Bilen Ozyurek depart.ent of Biology(Biotechnology) Faculty of ScienceHacettepe UniversityAnkaraBeytepe06800Turkey

The purpose of this study was to identify and compare the degradation efficiencies of free and entrapped bacterial consortia(Staphylococcus capitis CP053957.1 and Achromobacter marplatensis MT078618.1)to different polymers such as Sodium Alginate(SA),Sodium Alginate/Poly(Vinyl Alcohol)(SA/PVA),and Bushnell Haas Agar(BHA).In addition to SA and SA/PVA,which are cost-effective,non-toxic and have different functional groups,BHA,which is frequently encountered in laboratory-scale studies but has not been used as an entrapment material until *** on these,the polymers with different surface morphologies and chemical compositions were analyzed by SEM and *** the petroleum removal efficiency was higher with the entrapped bacterial consortia than with the free one,BHA-entrapped bacterial consortium enhanced the petroleum removal more than SA and SA/***,the degradation rate of bacterial consortia entrapped with BHA was 2.039 day^(-1),SA/PVA was 1.560,SA was 0.993,the half-life period of BHA-entrapped bacterial consortia is quite low(t_(1/2)=0.339)compared with SA(t_(1/2)=0.444)and SA/PVA(t_(1/2)=0.697).The effects of the four main factors such as:amount of BHA(0.5,1,1.5,2,2.5,3 g),disc size(4,5,6,7,8 mm),inoculum concentration(1,2.5,5,7.5,10 mL),and incubation period on petroleum removal were also *** maximum petroleum removal(94.5%)was obtained at≥2.5 mL of bacterial consortium entrapped in 2 g BHA with a 7 mm disc size at 168 h and the results were also confirmed by statistical *** a decrease was observed during the reuse of bacterial consortium entrapped in BHA,the petroleum removal was still above 50%at 10th *** on GC-MS analysis,the removal capacity of BHA-entrapped consortium was over 90%for short-chain n-alkanes and 80%for medium-chain ***,the obtained data are expected to provide a potential guideline in cleaning up the large-scale oil pollution in the *** there has been no similar stud

关键词： Entrapment of bacterial consortia Petroleum RemovalBushnell Haas agar Sodium alginate Sodium alginate/poly(vinyl alcohol)

Numerical simulation of the effect of coaxial and cross-axis injection modes on pulverized coal combustion in the raceway of blast furnace tuyere

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Particuology 2024年第10期93卷 154-169页

作者： Yunpeng Wang Lei Gao Xiaolei Zhou faculty of Metallurgy and Energy Engineering Kunming University of Science and TechnologyKunming650093China

The aim of this study is to investigate the influence of the angle of the pulverized coal (PC) injection lance on the combustion characteristics of fuel in the raceway of blast furnace tuyeres. Using FLUENT software, a Euler-Lagrange three-dimensional numerical model was constructed to analyze the influence of different positions of blast furnace tuyere coal powder injection lance (coaxial and cross-axis) on key parameters such as temperature distribution, gas flow, and combustion efficiency. The results demonstrate that adjusting the angle of the injection lance significantly modifies the average and peak temperatures in the raceway, while the composition of gas components remains relatively stable. When the injection lance angle is 10°, the average temperature and peak temperature in the raceway are 2294 K and 2747 K, respectively. When the injection lance angle is 12°, the combustion efficiency of the PC reaches 80.8%. This study reveals the significant impact of the injection lance angle on the combustion process. Especially at an angle of 12°, the combustion efficiency of the blast furnace significantly improves. With coaxial injection, the combustion rate increases as the distance between the injection lance tip and the tuyere increases. This paper is instructive for the optimization of the blast furnace combustion system, which improve fuel utilization efficiency and reduce environmental emissions. This paper provides practical recommendations for adjusting blast furnace operational parameters, offering insights for achieving more efficient and environmentally friendly industrial production.

关键词： Pulverized coal combustion Tuyere raceway Blast furnace CFD simulation

Ionization Potential Depression Model for Warm/Hot and Dense Plasmas

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Chinese Physics Letters 2024年第8期41卷 45-57页

作者： Chensheng Wu Fuyang Zhou Jun Yan Xiang Gao Yong Wu Chunhua Zeng Jianguo Wang Institute of Applied Physics and Computational Mathematics Beijing 100088China faculty of science Kunming University of Science and TechnologyKunming 650500China

For warm/hot and dense plasmas(WDPs),ionization potential depression(IPD)plays a crucial role in determining its ionization balance and understanding the resultant microscopic plasma properties.A sophisticated and unified IPD model is necessary to resolve those existing discrepancies between theoretical and experimental ***,the applicability of those widely used IPD models nowadays is limited,especially for the nonlocal thermodynamic equilibrium(non-LTE)dense plasma produced by short-pulse *** this work,we propose an IPD model that considers inelastic atomic processes,in which three-body recombination and collision ionization processes are found to play a crucial role in determining the electron distribution and IPD for a *** IPD model is validated by reproducing latest experimental results of Al plasmas with a wide-range condition of 70 eV–700 eV temperature and 0.2–3 times solid density,as well as a typical non-LTE system of hollow Al *** is demonstrated that the present IPD model has a significant temperature dependence due to the consideration of the inelastic collision *** a lower computational cost and wider application range of plasma conditions,the proposed model is expected to provide a promising tool to study the ionization balance and the atomic processes,as well as the related radiation and particle transports properties of the WDP.

关键词： properties. collision determining

Accurate Source-Receiver Positioning Method for a High-Resolution Deep-Towed Multichannel Seismic Exploration System

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Journal of Ocean University of China 2024年第2期23卷 415-426页

作者： LI Jing LIU Kai WEI Zhengrong ZHANG Liancheng LIU Yangting PEI Yanliang LIU Chenguang LIU Baohua Key Laboratory of Marine geology and Metallogeny First Institute of OceanographyMNRQingdao 266061China Laboratory for Marine geology Laoshan LaboratoryQingdao 266061China College of Ocean science and Engineering Shandong University of Science and TechnologyQingdao 266590China Key Laboratory of Fluid Transmission Technology of Zhejiang Province Zhejiang Sci-Tech UniversityHangzhou 310018China

The near-seabed multichannel seismic exploration systems have yielded remarkable successes in marine geological disaster assessment,marine gas hydrate investigation,and deep-sea mineral exploration owing to their high vertical and horizontal ***,the quality of deep-towed seismic imaging hinges on accurate source-receiver positioning *** light of existing technical problems,we propose a novel array geometry inversion method tailored for high-resolution deep-towed multichannel seismic exploration *** method is independent of the attitude and depth sensors along a deep-towed seismic streamer,accounting for variations in seawater velocity and seabed slope *** approach decomposes the towed line array into multiline segments and characterizes its geometric shape using the line segment distance and pitch *** optimization parameters for seawater velocity and seabed slope angle,we establish an objective function based on the model,yielding results that align with objective *** the particle swarm optimization algorithm enables synchronous acquisition of optimized inversion results for array geometry and seawater *** validation using theoretical models and practical data verifies that our approach effectively enhances source and receiver positioning inversion *** algorithm exhibits robust stability and reliability,addressing uncertainties in seismic traveltime picking and complex seabed topography conditions.

关键词： high-resolution deep-towed multichannel seismic exploration source-receiver positioning array geometry inversion seawater heterogeneity seabed slope angle

Surface wave inversion with unknown number of soil layers based on a hybrid learning procedure of deep learning and genetic algorithm

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Earthquake Engineering and Engineering Vibration 2024年第2期23卷 345-358页

作者： Zan Zhou Thomas Man-Hoi Lok Wan-Huan Zhou depart.ent of Civil and Environmental Engineering Faculty of Science and TechnologyUniversity of MacaoMacaoChina

Surface wave inversion is a key step in the application of surface waves to soil velocity ***,a common practice for the process of inversion is that the number of soil layers is assumed to be known before using heuristic search algorithms to compute the shear wave velocity profile or the number of soil layers is considered as an optimization ***,an improper selection of the number of layers may lead to an incorrect shear wave velocity *** this study,a deep learning and genetic algorithm hybrid learning procedure is proposed to perform the surface wave inversion without the need to assume the number of soil ***,a deep neural network is adapted to learn from a large number of synthetic dispersion curves for inferring the layer ***,the shear-wave velocity profile is determined by a genetic algorithm with the known layer *** applying this procedure to both simulated and real-world cases,the results indicate that the proposed method is reliable and efficient for surface wave inversion.

关键词： surface wave inversion analysis shear-wave velocity profile deep neural network genetic algorithm

Novel synthesis of stabilized Bi1-x-yGdxDyyO1.5 solid electrolytes with enhanced conductivity for intermediate temperature solid oxide fuel cells（SOFCs）

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Journal of Rare Earths 2024年第10期42卷 1903-1911页

作者： Ahmed H.Ibrahim Yehia M.Abbas H.A.Ayoub Marwa H.Ali Mustafa Aldoori Materials science Laboratory Physics DepartmentFaculty of ScienceSuez Canal University Ministry of Higher Education and Scientific Research Aliraqia University

Herein,we report the synthesis of a Dy-Gd co-doped cubic phase-stabilized Bi2O3solid electrolyte system via solid-state processing under atmospheric *** with Dy3+and Gd3+has been observed to significantly enhance the densification process during sintering for stabilization purposes,thereby improving the electrical properties of δ-Bi2O3-type *** synthesized ceramics were characterized using X-ray diffraction（XRD）,field emission scanning electron microscopy-energy dispersive X-ray spectroscopy（FESEM-EDX）,thermal gravimetry/differential thermal analysis（TG/DTA）,and the four-point probe technique（4PPT）.XRD analysis reveals that the samples Bi1-x-yGdxDyyO1.5（y=0.05/x=0.05,0.10,0,15,and 0.20,and x=0.05/y=0.10,0.15,and 0.20） exhibit a stable face-centered cubic δ-phase and a mixed-phase crystallographic *** XRD analysis of the stabilized δ-phase suggests that the prepared oxides show a face-centered cubic（FCC） structure with a space group of *** micrographs reveal that the composition Bi0.90Gd0.05Dy0.05O1.5has no significant ***,an evident increase in the pore formation is observed as the amount of Gd2O3increases until it reaches 20%.This finding suggests that dense pellets are formed during the sintering process at 900-1000℃.The DTA analyses were performed to verify the phase stability,which agrees with the XRD *** electrochemical performance of the synthesized Dy-Gd co-doped Bi2O3solid electrolyte system was evaluated and analyzed in detail by using the electrochemical impedance spectroscopy（EIS） technique,Based on EIS and conductivity measurements,Bi0.75Gd0.20Dy0.05O1.5exhibits the lowest activation energy of 0.519 eV and the highest conductivity value of 0.398 S/cm at 627℃compared to the other samples;this composition can be used as a solid electrolyte for intermediatetemperature solid oxide fuel cells（SOFCs）.

关键词： Electrochemical impedance spectroscopy (EIS) Fast Fourier transform (FFT) Rare earths Rietveld Solid oxide fuel cells (SOFCs) Solid-state processing

Water-soluble organic matter with various polarities in PM_(2.5) over Xi'an,China:Abundance,functional groups,and light absorption

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Particuology 2024年第1期84卷 281-289页

作者： Xueting Yang Shasha Huang Dan Li Hongmei Xu Yaling Zeng Liu Yang Diwei Wang Ningning Zhang Junji Cao Zhenxing Shen depart.ent of Environmental science and Engineering Xi'an Jiaotong UniversityXi'an710049China School of Environmental science and Engineering Southern University of Science and TechnologyShenzhen518055China State Key Laboratory of Loess and Quaternary geology Institute of Earth EnvironmentChinese Academy of SciencesXi'an710049China

Humic-like substances(HULIS)are a major component of brown carbon and consequently play a major role in climate *** this study,70 PM_(2.5) samples were collected from Xi'an in winter 2019 and summer *** HULIS(HULIS-n),acidic HULIS(HULIS-a),and high-polarity water-soluble organic compounds(HP-WSOC)were analyzed to determine their carbon concentrations and measure their ultraviolet-visible absorption and infrared *** the three components,HULIS-n had the highest carbon content in both winter(3.29±1.45μg m^(-3))and in summer(1.38±1.10μg m^(-3)).The semi-quantitative results for the functional groups revealed that HP-WSOC was rich in carboxylic acids and had high aromaticity in winter,whereas HULIS-n was rich in carboxylic acids in ***,HULJS-a was richer in nitrate esters and saturated aliphatic hydrocarbons in summer than in *** results for specific ultraviolet absorbance(SUVA)and E_(250)/E_(365) revealed that HULIS had higher molecular weight and aromaticity in winter than in ***-n dominated in the total light absorption of HULIS+HP-WSOC in both winter(73.08%)and summer(48.57%).Overall,the results on the carbon content,optical properties,and functional groups of WSOCs with differing polarity can improve un-derstanding of environmental and climatic effects.

关键词： Humic-like substances(HULIS) Aromaticity Fourier-transform infrared(FTIR) spectroscopy Light absorbance