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A plotless density estimator with a Norton-Rice distribution for ordered distances

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Journal of Forestry Research 2021年第6期32卷 2385-2401页

作者： steen Magnussen Canadian Forest Service Pacific Forestry CentreNatural Resources CanadaVictoriaBCV8Z 1M5Canada

A Norton-Rice distribution(NRD)is a versatile,flexible distribution for k ordered distances from a random location to the k nearest *** a context of plotless density estimation(PDE)with n randomly chosen sample locations,and distances measured to the k=6 nearest objects,the NRD provided a good fit to distance data from seven populations with a census of forest tree stem *** importantly,the three parameters of a NRD followed a simple trend with the order(1,…,6)of observed *** trend is quantified and exploited in a proposed new PDE through a joint maximum likelihood estimation of the NRD parameters expressed as a functions of distance *** simulated probability sampling from the seven populations,the proposed PDE had the lowest overall bias with a good performance potential when compared to three alternative ***,absolute bias increased by 0.8 percentage points when sample size decreased from 20 to *** terms of root mean squared error(RMSE),the new proposed estimator was at par with an estimator published in Ecology when this study was wrapping up,but otherwise superior to the remaining two investigated *** of nominal 95%confidence intervals averaged 0.94 for the new proposed estimators and 0.90,0.96,and 0.90 for the comparison *** tangible improvements in PDEs over the last decades,a globally least biased PDE remains elusive.

关键词： Fixed-count sampling Spatial point pattern Distance distributions Forest inventory Joint maximum likelihood estimation Bias Root mean squared error Coverage

EVALUATION OF ADDED RESISTANCE OF KVLCC2 IN SHORT WAVES

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Journal of Hydrodynamics 2011年第6期23卷 709-722页

作者： steen Sverre Department of Marine Technology Norwegian University of Science and Technology

The added resistance of KVLCC2 in short and regular head waves has been studied theoretically and experimentally. Model tests are performed to determine how well the asymptotic formula （Faltinsen et al. 1980） predicts the typical level of added resistance in short waves. Because the asymptotic formula neglects the effects of ship motions, it is combined with theoretical methods to calculate the added resistance in long waves using an function to predict the added resistance in the intermediate wavelength region where both ship motions and wave reflection are important. A unique feature of this experiment is that the ship model is divided into three segments to explore the added resistance distribution with respect to hull segment. This paper discusses the sensitivity of experimental results to the quality of the incident regular head waves. Moreover, a novel procedure for analyzing added resistance is described. Finally, the experimentally determined added resistance of KVLCC2 is compared with theoretical results. It is shown that the added resistance from the combined theoretical methods agrees well with experimental results in both the intermediate and short wave regions. The use of hull segments shows that added resistance is concentrated primarily at the bow.

关键词： added resistance KVLCC2 short waves function

A computationally efficient method for identification of steady state in time series data from ship monitoring

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Journal of Ocean Engineering and Science 2020年第4期5卷 333-345页

作者： Øyvind Øksnes Dalheim Sverre steen Department of Marine Technology Norwegian University of Science and Technology(NTNU)Otto Nielsens vei 10Trondheim 7491Norway Rolls-Royce 1 University Technology Centre(UTC)-Ship performance and cyber-physical systems TrondheimNorway

Most applied time series are non-stationary,or exhibit some kind of non-stationarity for at least parts of the time *** time series analyses or mathematical modeling purposes,the non-stationarities can be difficult to ***,identification of stationary and non-stationary behavior is of great practical interest in time series *** this study a robust and computationally efficient method to identify steady state parts of time series data is *** method is based on the class of deterministic trend models using a sliding window,and is focused towards being easy to implement,efficient and practical in use and to preserve data *** demonstrate the performance of the steady state identifier,the method is applied on different sets of time series data from two ships equipped with systems for in-service *** method is shown to be reliable and practical for identifying steady state parts of time series data,and can serve as a practical preprocessing tool for time series data analysis.

关键词： Stationarity Steady state Signal extraction Change point In-service data Ship monitoring

Rapid mapping of alloy surface phase diagrams via Bayesian evolutionary multitasking

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npj Computational Materials 2023年第1期9卷 905-918页

作者： Shuang Han steen Lysgaard Tejs Vegge Heine Anton Hansen Department of Energy Conversion and Storage Technical University of DenmarkAnker EngelundsvejBuilding 3012800 Kgs.LyngbyDenmark

Surface phase diagrams(SPDs)are essential for understanding the dependence of surface chemistry on reaction *** multi-component systems such as metal alloys,the derivation of such diagrams often relies on separate first-principles global optimization tasks under different reaction *** we show that this can be significantly accelerated by leveraging the fact that all tasks essentially share a unified configurational search space,and only a single expensive electronic structure calculation is required to evaluate the stabilities of a surface structure under all considered reaction *** a general solution,we propose a Bayesian evolutionary multitasking(BEM)framework combining Bayesian statistics with evolutionary multitasking,which allows efficient mapping of SPDs even for very complex surface *** proofs of concept,we showcase the performance of our methods in deriving the alloy SPDs for two heterogeneous catalytic systems:the electrochemical oxygen reduction reaction(ORR)and the gas phase steam methane reforming(SMR)reaction.

关键词： alloy surface diagrams

Use of Standard Operating Procedures for Supporting Cross-Organizational Emergency Management:Challenges and Opportunities Identified from a Tabletop Exercise

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International Journal of Disaster Risk Science 2024年第5期15卷 673-687页

作者： Kristine steen-Tveit Bjørn Erik Munkvold Kjetil Rustenberg Department of Information Systems Centre for Integrated Emergency ManagementUniversity of Agder4630KristiansandNorway

This study investigated the crucial role of formulating and applying standard operating procedures(SOPs)in the context of emergency planning and *** effective application of SOPs during operations is essential in order to address challenges that surpass individual organizational capacities.A specific focus on fostering efficient information sharing and executing specified actions maximizes the prospect of *** explore the collective functionality of SOPs across organizations,we conducted a comprehensive tabletop exercise involving 10 organizations spanning tactical,operational,and strategic *** analysis identified six key challenges,primarily related to the structures for information sharing,communication pathways,and the complex integration and application of common SOPs within these diverse organizational *** research contributes insights into the use of SOPs in large-scale,cross-organizational scenarios.

关键词： Cross-organizational emergency management Standard operating procedures Tabletop exercise Team situational awareness

Unfolding the structural stability of nanoalloys via symmetry-constrained genetic algorithm and neural network potential

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npj Computational Materials 2022年第1期8卷 1135-1145页

作者： Shuang Han Giovanni Barcaro Alessandro Fortunelli steen Lysgaard Tejs Vegge Heine Anton Hansen Department of Energy Conversion and Storage Technical University of DenmarkFysikvej2800Kgs.LyngbyDenmark CNR-ICCOM&IPCF Consiglio Nazionale delle Ricerchevia G.Moruzzi 156124PisaItaly

The structural stability of nanoalloys is a challenging research subject due to the complexity of size,shape,composition,and chemical *** genetic algorithm is a popular global optimization method that can efficiently search for the ground-state nanoalloy ***,the algorithm suffers from three significant limitations:the efficiency and accuracy of the energy evaluator and the algorithm’s *** we describe the construction of a neural network potential intended for rapid and accurate energy predictions of Pt-Ni nanoalloys of various sizes,shapes,and *** further introduce a symmetry-constrained genetic algorithm that significantly improves the efficiency and viability of the algorithm for realistic size *** combination of the two allows us to explore the space of homotops and compositions of Pt-Ni nanoalloys consisting of up to 4033 atoms and quantitatively report the interplay of shape,size,and composition on the dominant chemical ordering patterns.

关键词： structure symmetry constrained

Review on modelling of corrosion under droplet electrolyte for predicting atmospheric corrosion rate

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Journal of Materials Science & Technology 2021年第3期62卷 254-267页

作者： Bangalore Gangadharacharya Koushik Nils Van den steen Mesﬁn Haile Mamme Yves Van Ingelgem Herman Terryn Vrije Universiteit Brussel Research Group Electrochemical and Surface Engineering(SURF)Pleinlaan 21050 BrusselsBelgium Vrije Universiteit Brussel Eenheid Algemene Chemie(ALGC)Pleinlaan 21050 BrusselsBelgium

Atmospheric corrosion of metals is the most common type of corrosion which has a significant impact on the environment and operational safety in various situations of everyday *** of the common examples can be observed in land,water and air transportation systems,electronic circuit boards,urban and offshore *** dew drops formed on metal surface due to condensation of atmospheric moisture facilitates corrosion as an *** corrosion mechanisms under these droplets are different from classically known bulk electrolyte *** to thin and non-uniform geometric thickness of the droplet electrolyte,the atmospheric oxygen requires a shorter diffusion path to reach the metal *** corrosion under a droplet is driven by the depletion of oxygen in the center of the droplet compared to the edge,known as differential *** case of a larger droplet,differential aeration leads to preferential cathodic activity at the edge and is controlled by the droplet ***,for a smaller droplet,the oxygen concentration remains uniform and hence cathodic activity is not controlled by droplet *** geometry of condensed droplets varies dynamically with changing environmental parameters,influencing corrosion mechanisms as the droplets evolve in *** this review,various modelling approaches used to simulate the corrosion under droplet electrolytes are *** the efforts of developing a comprehensive model to estimate corrosion rates,it has been noted from this review that the influence of geometric evolution of the droplet due to condensation/evaporation processes on corrosion mechanisms are yet to be *** varying external factors like environmental temperature,relative humidity,presence of hygroscopic salts and pollutants influence the evolution of droplet electrolyte,making it a complex phenomenon to ***,an overview of available dropwise condensation and evaporation models which descri

关键词： Atmospheric corrosion Water droplets Mathematical modelling Condensation Evaporation

Genetic algorithms for computational materials discovery accelerated by machine learning

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npj Computational Materials 2019年第1期5卷 746-751页

作者： Paul C.Jennings steen Lysgaard Jens Strabo Hummelshøj Tejs Vegge Thomas Bligaard SUNCAT Center for Interface Science and Catalysis Department of Chemical EngineeringStanford UniversityStanfordCA 94305USA SLAC National Accelerator Laboratory 2575 Sand Hill RoadMenlo ParkCA 94025USA Department of Energy Conversion and Storage Technical University of DenmarkLyngbyDenmark Toyota Research Institute Los AltosCA 94022USA

Materials discovery is increasingly being impelled by machine learning methods that rely on pre-existing *** datasets are lacking,unbiased data generation can be achieved with genetic *** a machine learning model is trained on-the-fly as a computationally inexpensive energy predictor before analyzing how to augment convergence in genetic algorithm-based approaches by using the model as a *** leads to a machine learning accelerated genetic algorithm combining robust qualities of the genetic algorithm with rapid machine *** approach is used to search for stable,compositionally variant,geometrically similar nanoparticle alloys to illustrate its capability for accelerated materials discovery,e.g.,nanoalloy *** machine learning accelerated approach,in this case,yields a 50-fold reduction in the number of required energy calculations compared to a traditional“brute force”genetic *** makes searching through the space of all homotops and compositions of a binary alloy particle in a given structure feasible,using density functional theory calculations.

关键词： alloy alloys searching

The importance of aboveground and belowground interspecific interactions in determining crop growth and advantages of peanut/maize intercropping

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The Crop Journal 2021年第6期9卷 1460-1469页

作者： Nianyuan Jiao Jiangtao Wang Chao Ma Chaochun Zhang Dayong Guo Fusuo Zhang Erik steen Jensen College of Agronomy Henan University of Science and TechnologyLuoyang 471023HenanChina College of Resources and Environmental Sciences China Agricultural UniversityBeijing 100193China Department of Biosystems and Technology Swedish University of Agricultural SciencesAlnarp 23053Sweden

Intercropping of maize(Zea mays L.) and peanut(Arachis hypogaea L.) often results in greater yields than the respective sole crops. However, there is limited knowledge of aboveground and belowground interspecific interactions between maize and peanut in field. A two-year field experiment was conducted to investigate the effects of interspecific interactions on plant growth and grain yield for a peanut/maize intercropping system under different nitrogen(N) and phosphorus(P) levels. The method of root separation was employed to differentiate belowground from aboveground interspecific interactions. We observed that the global interspecific interaction effect on the shoot biomass of the intercropping system decreased with the coexistence period, and belowground interaction contributed more than aboveground interaction to advantages of the intercropping in terms of shoot biomass and grain yield. There was a positive effect from aboveground and belowground interspecific interactions on crop plant growth in the intercropping system, except that aboveground interaction had a negative effect on peanut during the late coexistence period. The advantage of intercropping on grain came mainly from increased maize yield(means 95%) due to aboveground interspecific competition for light and belowground interaction(61%–72% vs. 28%–39% in fertilizer treatments). There was a negative effect on grain yield from aboveground interaction for peanut, but belowground interspecific interaction positively affected peanut grain *** supply of N, P, or N + P increased grain yield of intercropped maize and the contribution from aboveground interspecific interaction. Our study suggests that the advantages of peanut/maize intercropping for yield mainly comes from aboveground interspecific competition for maize and belowground interspecific facilitation for peanut, and their respective yield can be enhanced by N and P. These findings are important for managing the intercropping system and optim

关键词： Peanut/maize intercropping Aboveground interspecific competition Belowground interspecific facilitation Nitrogen and phosphorus Advantage of intercropping