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Estimating underground mine ventilation friction factors from low density 3D data acquired by a moving LiDAR

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International Journal of Mining Science and Technology 2018年第4期28卷 650-655页

作者： Curtis Watson joshua Marshall Mining Systems Laboratory The Robert M.Buchan Department of Mining Queen's University

Ventilation system analysis for underground mines has remained mostly unchanged since the Atkinson method was made popular by Mc Elroy in 1935. Data available to ventilation technicians and engineers is typically limited to the quantity of air moving through any given heading. Because computer-aided modelling, simulation, and ventilation system design tools have improved, it is now important to ensure that developed models have the most accurate information possible. This paper presents a new technique for estimating underground drift friction factors that works by processing 3 D point cloud data obtained by using a mobile Li DAR. Presented are field results that compare the proposed approach with previously published algorithms, as well as with manually acquired measurements.

关键词： Mine ventilation Mine design Mobile mapping Roughness estimation Friction factors LiDAR3D point clouds

Structure and dendroecology of Thuja occidentalis in disjunct stands south of its contiguous range in the central Appalachian Mountains, USA

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Forest Ecosystems 2017年第1期4卷 55-65页

作者： joshua A. Kincaid Shenandoah University 1460 University Drive Winchester VA 22601 USA

Background： Information on forest structure, growth, and disturbance history is essential for effective forest management in a dynamic landscape. Because most of our research concerning the ecology and growth of Thujo ocddenralis comes from sites in northern portions of its range, highly contextual biotic and abiotic factors that affect the species in more southern locales may not be fully accounted for. This research characterized the structural attributes and growth dynamics of Thuja occidentolis in disjunct forest stands south of its contiguous range margin. Methods： The Thujo occidentalis forests examined in this research were located in the central Appalachian Mountains, USA, approximately 440 km south of the contiguous range margin of the species. Forest structural attributes were characterized in two Thujo occidentalis forest stands, which are rare in the region. Tree-ring chronologies were used to examine the influences of disturbance and climate on the growth of Thuja occidentolis. Results： The forests contained a total of 13 tree species with Thuja occidentalis contributing substantially to the basal area of the sites. Thujo occidentalis stems were absent in the smallest size class, while hardwood species were abundant in the smallest classes. Thuja occidentalis stems also were absent from the 〈 70 years age class. By contrast, Thuja occidentalis snags were abundant within stands. Growth-release events were distributed across the disturbance chronology and generally affected a small number of trees. The Thujo occidentolis tree-ring chronology possessed an interseries correlation of 0.62 and mean sensitivity of 0.25. The correlation between mean temperature and Thuja occidentalis growth was weak and variable. Growth and moisture variables were more strongly correlated, and this relationship was predominantly positive. Conclusions： Structural attributes indicate the forests are in the understory reinitiation stage of forest development. Silvicultural manipul

关键词： Northern white cedar Disturbance Climate Range Disjunct Radial growth Regeneration

The legal sustainability of energy substitution in Nigeria’s electric power sector:renewable energy as alternative

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Protection and Control of Modern Power Systems 2020年第1期5卷 378-389页

作者： Olusola joshua Olujobi Legal Practitioner and Lecturer Business Management Department Covenant University Ota Ogun State Nigeria

Non-renewable fuel sources have been the predominant energy sources and a significant source of foreign exchange income for Nigeria,while at the same time there is a severe problem of electricity inconsistency and persistent power blackouts in *** research aims to end the concern for deficient energy use,and to encourage energy efficiency and *** has not maximized the advantages of renewable energy after the denationalisation of its electricity industry despite the current transformation in the power industry and the rising demand for renewable energy *** research adopts a doctrinal legal approach with a library-based legal research technique with a comparative legal *** reveals that the absence of a comprehensible legal regime with encouragement for the use of renewable energy is the fundamental element causing the slow utilization of renewable energy as a substitute source of energy in *** is suggested that,among other reforms,there is a need for a comprehensible legal regime on renewable energy and the encouragement of strict implementation of energy regulatory strategies and policies with incentives for the application of renewable energy sources in Nigeria.

关键词： Non-renewable energy Sustainability Renewable energy Fossil fuel Nigeria

Influence of climate fluctuations on Pinus palustris growth and drought resilience

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Forest Ecosystems 2023年第6期10卷 681-689页

作者： Joao Campoa joshua Puhlick CENSE–Center for Environmental and Sustainability Research CHANGE-Global Change and Sustainability InstituteDepartment of Environmental Sciences and EngineeringNOVA School of Science and TechnologyNOVA University LisbonCampus de Caparica2829-516 CaparicaPortugal The Jones Center at Ichauway 3988 Jones Center Drive39870NewtonGAUSA

The longleaf pine(Pinus palustris Mill.)ecosystem is an endangered ecosystem in the southeastern USA,and efforts to restore the species are ***,in recent decades,the region has experienced drastic fluctuations between wet and dry growing season conditions from year to year,and it is not fully understood how these fluctuations have influenced the growth of *** address this topic,we cored *** trees in woodlands of southwest Georgia and used dendrochronology techniques to determine how climate fluctuations have influenced the growth and drought resilience of *** also cored slash pine(Pinus elliottii Engelm.)trees in the same woodlands to compare growth between *** *** growth was less impacted by adverse climate conditions compared to ***,the strength of correlations between *** growth and temperature,precipitation,and Palmer Drought Severity Index(PDSI)changed over *** recent decades,climate conditions during the growing season became more influential on *** growth than the previous year's *** is concerning given that drought severity during the growing season has been *** results also indicate that *** was less resilient to droughts during the 2000s and 2010s than to those of the *** this new climate paradigm,our results suggest that *** might be more susceptible to growth reductions and less resistant to droughts than once *** work highlights the importance of understanding the impact of novel climate conditions on *** and has implications for restoration efforts,such as using silvicultural treatments that reduce tree vulnerability to drought(e.g.,thinning)and promote other climate-adapted species in mixture with ***.

关键词： Longleaf pine Slash pine Pinus elliottii Climate change Dendrochronology Dendroclimatology Forest disturbances

Influence of indoor airflow on airborne disease transmission in a classroom

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Building Simulation 2024年第3期17卷 355-370页

作者： Mojtaba Zabihi Ri Li joshua Brinkerhoff School of Engineering Faculty of Applied ScienceUniversity of British ColumbiaKelownaCanada

It has been widely accepted that the most effective way to mitigate airborne disease transmission in an indoor space is to increase the ventilation airflow,measured in air change per hour(ACH).However,increasing ACH did not effectively prevent the spread of *** better understand the role of ACH and airflow large-scale patterns,a comprehensive fully transient computational fluid dynamics(CFD)simulation of two-phase flows based on a discrete phase model(DPM)was performed in a university classroom setting with people *** investigations encompass various particle sizes,ventilation layouts,and flow *** findings demonstrated that the particle size threshold at which particles are deemed airborne is highly influenced by the background flow strength and large-scale flow pattern,ranging from 5µm to 10µm in the cases *** effects of occupants are significant and must be precisely accounted for in respiratory particle transport *** enhanced ventilation design(UFAD-CDR)for university classrooms is introduced that places a premium on mitigating airborne disease *** to the baseline design at the same ACH,this design successfully reduced the maximum number density of respiratory particles by up to 85%.A novel airflow-related parameter,Horizontality,is introduced to quantify and connect the large-scale airflow pattern with indoor aerosol *** underscores that ACH alone cannot ensure or regulate air *** addition to the necessary ACH for air exchange,minimizing horizontal bulk motion is essential for reducing aerosol transmissibility within the room.

关键词： aerosol transmission airflow pattern horizontality COVID-19 simulation classroom ventilation

Regular Orbits of Extra-special Groups

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Algebra Colloquium 2016年第4期23卷 681-688页

作者： joshua E. Goodson Texas A&M University at Galveston Department of General Academics P.O. Box 1675 Galveston Texas 77553 USA

In this paper, for odd primes p we find a recursive formula for the number of regular orbits of an extra-special p-group of exponent p2 acting on a faithful irreducible module over a finite field. This complements an ... 详细信息

关键词： extra-special orbits counting p-groups

Characteristics and source of black carbon aerosol over Taklimakan Desert

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Science China Chemistry 2010年第5期53卷 1201-1208页

作者： FU S.joshua Department of Civil and Environmental Engineering The University of Tennessee

Black carbon(BC) and PM10 in the center of the Taklimakan Desert were online monitored in the whole year of *** addi-tion,TSP samples were also synchronously daily collected by medium-volume samplers with Whatman41 filters in the spring of *** in the dust aerosol was up to 1.14%of the total mass of PM10.A remarkable seasonal variation of BC in the aerosol was observed in the order of winter>spring>autumn>*** peak value of BC appeared at midnight while the lowest one in the evening each day,which was just the reverse of that in the urban *** contribution of BC to the total mass of PM10 on non-dust storm days was～11 times of that in dust *** back trajectory and principal component analysis,it was found that BC in the dust aerosol over Taklimakan Desert might be attributed to the emission from the anthropogenic activities,including domestic heating,cooking,combustion of oil and natural gas,and the medium-range transport from those oases located in the margins of the *** total BC aerosol from the Taklimakan Desert to be transported to the eastward downstream was estimated to be 6.3×104 ton yr-1.

关键词： black carbon aerosol the Taklimakan desert long-range transport

Fundamental behaviours of production traffic in underground mine haulage ramps

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International Journal of Mining Science and Technology 2015年第1期25卷 7-14页

作者： Haviland David Marshall joshua Golder Associates Ltd. The Robert M. Buchan Department of Mining Queen’s University

Ramps(or declines) are often used in underground mines to transport ore, waste, materials, and personnel. This paper studies mine ramp productivity and presents results from a set of computer simulations designed to model the fundamental behaviours of ramp haulage systems. Simulations show that, under fundamental assumptions without random disturbances, the haulage system always converges to a periodic behaviour in the steady state, but that productivities vary between equilibria. Simulations also demonstrate how productivity per vehicle does not necessarily decrease as more vehicles are added and,for example, in the five-vehicle case, how a 3.1% improvement can be achieved over the use of four vehicles. The result reveals the inefficiency of commonly-used lockout-style vehicle coordination strategies,and suggests a possible avenue for improving the productivity of haulage ramps by controlling the system to achieve more productive behaviours.

关键词： Underground miningFleet managementDiscrete-time simulationVehicle dispatching

How a systems perspective can help us with the interdisciplinarity puzzle

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Journal of Data and Information Science 2023年第1期8卷 2-8页

作者： joshua Eykens ECOOM-UAntwerpen Middelheimlaan 1 2020 AntwerpBelgium

1 Introduction The future of scientific knowledge production is by many envisioned as an interdisciplinary *** an increasing extent knowledge generated within separate disciplines will be integrated to develop effecti... 详细信息

关键词： knowledge today tomorrow