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Railway Engineering Science 2021年第3期29卷 258-270页

作者： Orwell Madovi Andreas Hoffrichter nick little Shanelle N.Foster Raphael Isaac Department of Electrical and Computer Engineering Michigan State University428 South Shaw LaneRoom 2120East LansingMI 48824USA Center for Railway Research&Education Broad College of BusinessMichigan State University3535 Forest RoadRoom C-36LansingMI 48910USA

Diesel fuel combustion results in exhaust containing air pollutants and greenhouse gas *** railway vehicles use diesel fuel as their energy *** emissions,as well as concerns about economical,alternative power supply,have driven efforts to move to hydrogen motive *** fuel cell technology applied to railways offers the opportunity to eliminate harmful exhaust emissions and the potential for a low-or zero-emission energy supply ***,only multiple-unit trains with hydrail technology operate *** of an Integrated Hybrid Train Simulator for intercity railway is *** proposed tool incorporates the effect of powertrain components during the wheel-to-tank *** to its predecessors,the proposed reconfigurable tool provides high fidelity with medium requirements and minimum computation *** train simulation and the federal government’s Greenhouse gases,Regulated Emissions,and Energy use in Transportation(GREET)model are used in combination to evaluate the feasibility of various train and powertrain *** Piedmont intercity service operating in North Carolina is used as a case *** study includes six train configurations and powertrain options as well as nine hydrogen supply options in addition to the diesel *** results show that a hydrail option is not only feasible,but a low-or zero-carbon hydrogen supply chain could be possible.

关键词： Hydrail Life cycle assessment Criteria pollutants Well-to-wheel Single train simulation Modeling

A new software for automated counting of glistenings in intraocular lenses in vivo

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International Journal of Ophthalmology(English edition) 2023年第8期16卷 1237-1242页

作者： nick Stanojcic Christopher C.Hull Eduardo Mangieri Nathan little David O’Brart Department of Ophthalmology Guy’s and St Thomas’NHS Foundation TrustLondon SE17EHUK Centre for Applied Vision Research School of Health SciencesUniversity of LondonLondon EC1V 0HBUK Sparca Ltd CroydonSurrey CR01QQUK King’s College London WC2R 2LSUK

AIM:To assess the performance of a bespoke software for automated counting of intraocular lens(IOL)glistenings in slit-lamp ***:IOL glistenings from slit-lamp-derived digital images were counted manually and automatically by the bespoke *** images of one randomly selected eye from each of 34 participants were used as a training set to determine the threshold setting that gave the best agreement between manual and automatic grading.A second set of 63 images,selected using randomised stratified sampling from 290 images,were used for software *** images were obtained using a previously described ***-derived automated glistenings counts were compared to manual counts produced by three ***:A threshold value of 140 was determined that minimised the total deviation in the number of glistenings for the 34 images in the training *** this threshold value,only slight agreement was found between automated software counts and manual expert counts for the validating set of 63 images(κ=0.104,95%CI,0.040-0.168).Ten images(15.9%)had glistenings counts that agreed between the software and manual *** were 49 images(77.8%)where the software overestimated the number of ***:The low levels of agreement show between an initial release of software used to automatically count glistenings in in vivo slit-lamp images and manual counting indicates that this is a non-trivial *** improvement involving a dialogue between software developers and experienced ophthalmologists is required to optimise *** results suggest that validation of software is necessary for studies involving semi-automatic evaluation of glistenings.

关键词： new software automated counting glistenings intraocular lenses slit-lamp images

ATC simulation for flight training:The missing link

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International Journal of Modeling, Simulation, and Scientific Computing 2017年第4期8卷 1-9页

作者： nick Papadopoli Engineering CPL Montreal QuebecCanada Nick.Papadopoli@***

This paper presents the state of piloted flight simulation fidelity with a focus on the missing link needed to complete the flight simulation experience,namely the simulated ATC environment(SATCE).To date,there has been a great deal of effort invested in providing the highest level of flight realism ***,little investment has gone into systems which are used to improve communication skills with ATC while in a populated active *** is important to note that the relatively few SATCEs is not due to the lack of technology,since such products have been available for about a *** primary reason for its absence is the inability and unwillingness for operators to justify the investment in such a training *** the meantime,the aviation industry has recognized that pilots need to have better communication skills while operating in various *** ICAO,with help from ARINC Industry Activities/FSEMC,has already taken steps to recommend the inclusion of SATCE characteristics in flight simulation *** aviation and research communities need to assist efforts by producing the necessary studies and metrics which can be used to evaluate and validate SATCEs used in the flight training.

关键词： Simulated air traffic control environment SATCE ATC communications artificial intelligent controllers flight training

Understanding the need for pre-injection from permeability measurements: What is the connection?

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Journal of Rock Mechanics and Geotechnical Engineering 2019年第3期11卷 576-597页

作者： nick Barton Eda Quadros nick Barton & Associates OsloNorway BGTech Soil and Rock Engineering Ltd. Sao PauloBrazil

Pre-grouting ahead of tunnels has three main functions:to control water inflow into the tunnel,to limit groundwater drawdown above the tunnel,and to make tunnelling progress more predictable since rock mass quality is effectively *** helps to avoid settlement damage caused by consolidation of clay deposits beneath built-up areas,since towns tend to be built where terrain is more flat,due to the clay *** are so many instances of settlement damage that the profession needs to take note of the need for high-pressure pre-grouting,to use micro-cements and micro-silica *** use of highpressure injection may cause joint jacking,but this is local in extent when the rapid pressure decay away from an injection hole is *** effect is variable and depends on the geometrical parameters of the *** pressure-decay advantage must not be violated by maintaining high pressure when grout flow from the injection hole has *** latter can cause damage to the grouting already *** methods of estimating mean hydraulic apertures(e)from Lugeon testing are described,and from more sophisticated three-dimensional(3D)permeability *** estimation of the larger mean physical joint apertures(E)is based on the joint roughness coefficient(JRC).Comparison is then made with the empirical aperture-particle size criterion E>4d95,where d95 represents almost the largest cement particle *** on joint set orientations and on the available micro-cements,the decision must be made of which range of pre-injection pressure should be aimed for,using successive reductions of the water-cement ratio w/*** simple estimation of permeability,also with depth dependence,can be made with the empirical link between a modified rock mass quality Q and permeability,which is termed *** value of this parameter can be based on core-logging or intunnel face *** 3D before-and-after-grouting permeability measurements have been use

关键词： Pre-grouting Micro-cement Hydraulic apertures Physical joint apertures Joint roughness Particle size Anisotropic permeability

Mixed reality emergency management:bringing virtual evacuation simulations into real-world built environments

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International Journal of Digital Earth 2019年第2期12卷 190-208页

作者： Ian Lochhead nick Hedley Department of Geography Simon Fraser UniversityBurnabyCanada

Computer-based evacuation simulations are important tools for emergency *** simulations vary in complexity and include 2D and 3D GIS-based network analyses,agent-based models,and sophisticated models built on documented human behaviour and particle *** the influential role of built environments in determining human movement,a disconnect often exists between the features of the real world and the way they are represented within these simulation *** proliferation of emergency management location-aware mobile devices,along with a recent infatuation for augmented reality(AR),has resulted in new wayfinding and hazard assessment tools that bridge this gap,allowing users to visualize geospatial information superimposed on the real *** this paper,we report research and development that has produced AR geovisual analytical systems,enabling visual analysis of human dynamics in multilevel built environments with complex thoroughfare network *** demonstrate prototypes that show how mixed reality visual analysis of intelligent human movement simulations built in virtual spaces can become part of real *** research introduces a fundamentally new way to view and link simulations of people with the real-world context of the built environment:mixed reality crowd simulation in real space.

关键词： Augmented reality 3D geovisualization situated simulation human movement analysis emergency management

Risk of shear failure and extensional failure around over-stressed excavations in brittle rock

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Journal of Rock Mechanics and Geotechnical Engineering 2017年第2期9卷 210-225页

作者： nick Barton Baotang Shen nick Barton&Associates OsloNorway CSIRO Energy BrisbaneAustralia

The authors investigate the failure modes surrounding over-stressed tunnels in *** lines of investigation are employed:failure in over-stressed three-dimensional(3D) models of tunnels bored under 3D stress,failure modes in two-dimensional(2D) numerical simulations of 1000 m and 2000 m deep tunnels using FRACOD,both in intact rock and in rock masses with one or two joint sets,and finally,observations in TBM(tunnel boring machine) tunnels in hard and medium hard massive *** reason for 'stress-induced' failure to initiate,when the assumed maximum tangential stress is approximately(0.4-0.5)σ_c(UCS,uniaxial compressive strength) in massive rock,is now known to be due to exceedance of a critical extensional strain which is generated by a Poisson's ratio ***,because similar 'stress/strength' failure limits are found in mining,nuclear waste research excavations,and deep road tunnels in Norway,one is easily misled into thinking of compressive stress induced *** of this,the empirical SRF(stress reduction factor in the Q-system) is set to accelerate as the estimated ratio σ_(θmax)/σ_c >> *** mining,similar 'stress/strength' ratios are used to suggest depth of *** reality behind the fracture initiation stress/strength ratio of '0.4' is actually because of combinations of familiar tensile and compressive strength ratios(such as 10) with Poisson's ratio(say0.25).We exceed the extensional strain limits and start to see acoustic emission(AE) when tangential stress σθ ≈ 0.4σc,due to simple *** combination of 2D theoretical FRACOD models and actual tunnelling suggests frequent initiation of failure by 'stable' extensional strain fracturing,but propagation in 'unstable' and therefore dynamic *** the case of very deep tunnels(and 3D physical simulations),compressive stresses may be too high for extensional strain fracturing,and shearing will dominate,both ahead of the face and following the *** shallower,the conc

关键词： Fracture propagation Tension Shear Poisson’s ratio Break-out Rock burst Deep tunnels FRACOD model

Computational fluid dynamics simulation of Hyperloop pod predicting laminar–turbulent transition

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Railway Engineering Science 2020年第1期28卷 97-111页

作者： Nathalie nick Yohei Sato Department of Mechanical and Process Engineering Swiss Federal Institute of TechnologyETH ZurichLEO B 9.1Leonhardstrasse 278092 ZurichSwitzerland Nuclear Energy and Safety Research Division Paul Scherrer InstituteForschungsstrasse 1115232 Villigen PSISwitzerland

Three-dimensional compressible flow simulationswere conducted to develop a Hyperloop pod. Thenovelty is the usage of Gamma transition model, in whichthe transition from laminar to turbulent flow can be ***, a mesh dependency study was undertaken,showing second-order convergence with respect to themesh refinement. Second, an aerodynamic analysis for twodesigns, short and optimized, was conducted with thetraveling speed 125 m/s at the system pressure 0.15 *** concept of the short model was to delay the transitionto decrease the frictional drag;meanwhile that of theoptimized design was to minimize the pressure drag bydecreasing the frontal area and introduce the transitionmore toward the front of the pod. The computed resultsshow that the transition of the short model occurred moreon the rear side due to the pod shape, which resulted in 8%smaller frictional drag coefficient than that for the optimizedmodel. The pressure drag for the optimized designwas 24% smaller than that for the short design, half ofwhich is due to the decrease in the frontal area, and theother half is due to the smoothed rear-end shape. The totaldrag for the optimized model was 14% smaller than that forthe short model. Finally, the influence of the systempressure was investigated. As the system pressure and theReynolds number increase, the frictional drag coefficientincreases, and the transition point moves toward the front,which are the typical phenomena observed in the transitionregime.

关键词： Computational fluid dynamics(CFD) Drag Subsonic compressible flow Hyperloop Laminar-turbulent transition

Prediction and Control of Distortion and Residual Stresses in Electron Beam Welding

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稀有金属材料与工程 2011年第S4期40卷 26-29页

作者： nick Bagshawa Chris Punshona TWI Ltd Granta ParkGreat AbingtonCambridgeCB21 6ALUK

Electron beam welding is recognized as an attractive method for minimizing distortion during welding,and is used frequently to join parts which are already finally machined or close to finished *** such cases,before EB welding,it is of great value to be able to estimate the level of accuracy that will be achieved and the dimensional stability of the assembly throughout its service *** presentation describes the development of a finite element (FE) modelling technique,validated by experiment,for predicting and understanding the development of residual stresses and distortion during EB welding,particularly in circular *** use of this method for optimization of welding procedures and residual stress mitigation methods is described and illustrated through a number of practical examples.

关键词： EB welding residual stress distortion

The boring billion? - Lid tectonics, continental growth and environmental change associated with the Columbia supercontinent

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Geoscience Frontiers 2013年第6期4卷 681-691页

作者： nick M.W.Roberts NERC Isotope Geosciences Laboratory British Geological SurveyKeyworthNottingham NG12 5GGUK

The evolution of Earth＇s biosphere,atmosphere and hydrosphere is tied to the formation of continental crust and its subsequent movements on tectonic *** supercontinent cycle posits that the continental crust is periodically amalgamated into a single landmass,subsequently breaking up and dispersing into various continental *** is possibly the first true supercontinent,it amalgamated during the 2.0-1.7 Ga period,and collisional orogenesis resulting from its formation peaked at 1.95-1.85 *** and palaeomagnetic evidence indicate that Columbia remained as a quasi-integral continental lid until at least 1.3 *** break-up attempts are evidenced by dyke swarms with a large temporal and spatial range; however,palaeomagnetic and geologic evidence suggest these attempts remained *** than dispersing into continental fragments,the Columbia supercontinent underwent only minor modifications to form the next supercontinent （Rodinia） at 1.1 -0.9 Ga; these included the transformation of external accretionary belts into the internal Grenville and equivalent collisional *** Columbia provides evidence for a form of ‘lid tectonics’,modern style plate tectonics occurred on its periphery in the form of accretionary *** detrital zircon and preserved geological record are compatible with an increase in the volume of continental crust during Columbia＇s lifespan; this is a consequence of the continuous accretionary processes along its *** quiescence in plate tectonic movements during Columbia＇s lifespan is correlative with a long period of stability in Earth＇s atmospheric and oceanic *** variability starting at 1.3 Ga in the environmental record coincides with the transformation of Columbia to Rodinia; thus,the link between plate tectonics and environmental change is strengthened with this interpretation of supercontinent history.

关键词： Rodinia Columbia Supercontinents Continental growth Lid tectonics Mesoproterozoic

Changes in the phenology of the ground beetle Pterostichus madidus

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Insect Science 2011年第4期18卷 462-472页

作者： Gabor Pozsgai nick A. littlewood Macaulay Land Use Research IneUtute Craigiebuckler Aberdeen UK

A growing body of evidence shows that climate change can alter the phenology of plants and animals. In this study long-term data from the UK Environmental Change Network （ECN） were analyzed to investigate whether there has been a change in the phenology of the ground beetle Pterostichus madidus （Fabricius, 1775）. Pitfall trap data were available from 12 ECN sites across the United Kingdom, most of which have been in operation for more than 15 years. Weather and vegetation datasets were also utilized. Pitfall trap lines were categorized to eight vegetation types. Trend analysis over time was carried out first using all the available dates of capture events, then the datasets grouped by vegetation type and site. Shifts in high-activity periods were also analyzed. P madidus appearance dates advanced significantly at seven sites and in five vegetation types. Peak activity advanced at two sites. At one site the timing of activity became significantly later. The last day of activity did not change significantly, supporting the theory that the cessation of the activity period is more likely to be controlled by photoperiod than temperature. The relationships between phenological variables and climatic factors were also investigated. Howe＇ver, no significant correlations were detected. These results demonstrate that between 1992 and 2008, phenology ofP madidus at seven sites from the eight analyzed has changed. Global warming may be driving these changes and future work will investigate underlying processes.

关键词： black clock beetle climate change Environmental Change Network life-history long-term data trend analysis