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Lessons learned from requirements gathering for virtual reality simulators

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Virtual Reality & Intelligent Hardware 2021年第5期3卷 407-422页

作者： Vivian gÓMEZ Kelly peÑARANDA Pablo FIgUEROA Department of Systems and Computing Engineering Universidad de Los AndesBogotá7620001Colombia

Background This paper shows how current collaborative virtual environments(VEs)such as Mozilla Hubs and AltspaceVR can aid in the task of requirements gathering in VR for simulation and *** We performed a qualitative study on our use of these technologies in the requirements gathering of two *** Our results show that requirements gathering in virtual reality has an impact on the process of requirements *** report advantages and shortcomings that will be of interest to future *** example,we found that VR sessions for requirements gathering in current VEs could benefit from better pointers and better sound *** Current VEs are useful for the requirements gathering task in the development of VR simulators and VR training environments.

关键词： Human computer interaction Virtual environment Requirements gathering globally dispersed teams VR simulators and training

Flexible and flame-retarding phosphorylated MXene/polypropylene composites for efficient electromagnetic interference shielding

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Journal of Materials Science & Technology 2022年第16期111卷 66-75页

作者： Tingting Tang shanchi Wang Yue Jiang Zhiguang Xu Yu Chen Tianshu pe.g Fawad Khan Jiabing Feng Pingan Song Yan Zhao College of Textile and Clothing Engineering Soochow UniversitySuzhou 215123China China-Australia Institute for Advanced Materials and Manufacturing Jiaxing UniversityJiaxing 314001China AECC Beijing Institute of Aeronautical Materials Beijing 100095China Centre for Future Materials University of Southern QueenslandSpringfield CentralQLD 4300Australia

Flame-retardant composites with high electromagnetic interference(EMI)shielding performance are desirable for electronic device *** great potential of MXene for high EMI,it still remains a great challenge to develop high-performance flame-retardant polymer/MXene composites with excellent EMI shielding effectiveness because of the poor oxidative stability of ***,phosphorylated MXene/polypropylene(PP)composites are prepared by coating phosphorylated MXene on PP fabric followed by spraying polyethylenimine(peI)and *** phosphorylated MXene proves to be more durable against oxidation than pure MXene due to the protection effect of *** hot-pressing,melted PP fibers are fused together at their contact points and thus as-prepared composites are bi-continuous with two interpenetrating *** composites show significantly improved thermal stability and flame retardancy relative to pure PP,with a low total heat release(THR)of 3.7 kJ/g and a heat release rate(HRR)of 50.0 W/g,which are reduced by 78%and 87%,*** addition,the composites exhibit a high electrical conductivity of~36,700 S/m and an EMI shielding performance of~90 d B over the whole frequency range of 8–12 gHz with a thickness of~400μ*** as-developed PP/MXene composites hold great promise for reliable protection of next-generation electronic devices working in complex environments.

关键词： MXene Flame retardancy Polypropylene composite EMI shielding

Modeling slow deformation of polygonal particles using DEM

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Particuology 2008年第6期6卷 506-514页

作者： Andrés A. pea pedro g. Lind Hans J. Herrmann Institute for Computational Physics Universitt Stuttgart Computational Physics IfB HIF E12 ETH Hnggerberg CH-8093 Zrich Switzerland Departamento de Física Universidade Federal do Ceará

We introduce two improvements in the numerical scheme to simulate collision and slow shearing of irregular particles. First, we propose an alternative approach based on simple relations to compute the frictional contact forces. The approach improves efficiency and accuracy of the Discrete Element Method （DEM） when modeling the dynamics of the granular packing. We determine the proper upper limit for the integration step in the standard numerical scheme using a wide range of material parameters. To this end, we study the kinetic energy decay in a stress controlled test between two particles. Second, we show that the usual way of defining the contact plane between two polygonal particles is, in general, not unique which leads to discontinuities in the direction of the contact plane while particles move. To solve this drawback, we introduce an accurate definition for the contact plane based on the shape of the overlap area between touching particles, which evolves continuously in time.

关键词： granular media Discrete element method Slow deformation Contact forces

The global boundary Stratotype Section and Point （gSSP） of the Drumian Stage （Cambrian） in the Drum Mountains, Utah, USA

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Episodes 2007年第2期30卷 85-95页

作者： Loren E. Babcock Richard A. Robison Margaret N. Rees shanchi pe.g Matthew R. Saltzman School of Earth Sciences The Ohio State University 125 South Oval Mall Columbus OH 43210 USA. Department of geology University of Kansas Lawrence KS 66045 USA. Department of geoscience University of Nevada Las Vegas Las Vegas NV 89145 USA. State Key Laboratory of Palaeobiology and Stratigraphy Nanjing Institute of Geology and Palaeontology Chinese Academy of Sciences 39 East Beijing Road Nanjing 210008 China.

The global boundary Stratotype Section and Point （gSSP） for the base of the Drumian Stage （Cambrian Series 3） is defined at the base of a limestone （calcisiltite） layer 62 m above the base of the Wheeler Formation in the Stratotype Ridge section, Drum Mountains, Utah, USA. The gSSP level contains the lowest occurrence of the cosmopolitan agnostoid trilobite Ptychagnostus atavus （base of the P. atavus Zone）. Secondary global markers near the base of the stage include the DICE negative δ^13C excursion, the onset of a long monotonic ^87Sr/^86Sr isotopic shift, and the transgressive phase of a eustatic event. Faunal turnovers close to the base of the Drumian Stage are recognized as the base of the Bolaspidella Zone （polymerid trilobites） in Laurentia, the historic base of the Floran Stage in Australia, the base of the Dorypyge richthofeni Zone （polymerid trilobites） in South China, and the base of the gapparodus bisulcatus-Westergaardodina brevidens Assemblage-zone （conodonts） in Baltica and South China. The last occurrence of the cosmopolitan trilobite Ptychagnostus gibbus occurs in the lower part of the Drumian Stage, and the base of the Hydrocephalus hicksii Zone （polymerid trilobites） as used in Siberia and Baltica occurs near the base of the stage.

关键词：寒武纪地球边界犹他州美国地层类型

Catastrophic climate change and the collapse of human societies

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National Science Review 2023年第6期10卷 52-54页

作者： Josep pe?uelas Sandra Nogué CREAF Cerdanyola del Vallès CSIC Global Ecology Unit CREAF-CSIC-UAB Universitat Autònoma de Barcelona

The scientific community has focused the agenda of studies of climate change on lower-end warming and simple risk analyses,because more realistic complex assessments of risk are more difficult,the benchmark of the international targets is the Paris Agreement goal of limiting warming to ged droughts,floods and heat waves,together with the consequent food insecurity,civil unrest and migrations,however,are opening the eyes not only of most scientists but also of most people all over the world to the need for considering,at least,the potential catastrophic effects of the collapse of ecosystems and society due to the current emergency of climate change.

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Virtual-reality-based digital twin of office spaces with social distance measurement feature

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Virtual Reality & Intelligent Hardware 2022年第1期4卷 55-75页

作者： Abhishek MUKHOPADHYAY g S Rajshekar REDDY KamalPreet Singh SALUJA Subhankar gHOSH Anasol peÑA-RIOS gokul gOPAL Pradipta BISWAS Indian Institute of Science BangaloreIndia BT Plc UK

Background Social distancing is an effective way to reduce the spread of the SARS-CoV-2 *** students and researchers have already attempted to use computer vision technology to automatically detect human beings in the field of view of a camera and help enforce social ***,because of the present lockdown measures in several countries,the validation of computer vision systems using large-scale datasets is a *** In this paper,a new method is proposed for generating customized datasets and validating deep-learning-based computer vision models using virtual reality(VR)*** VR,we modeled a digital twin(DT)of an existing office space and used it to create a dataset of individuals in different postures,dresses,and *** test the proposed solution,we implemented a convolutional neural network(CNN)model for detecting people in a limited-sized dataset of real humans and a simulated dataset of humanoid *** We detected the number of persons in both the real and synthetic datasets with more than 90%accuracy,and the actual and measured distances were significantly correlated(r=0.99).Finally,we used intermittent-layer-and heatmap-based data visualization techniques to explain the failure modes of a *** A new application of DTs is proposed to enhance workplace safety by measuring the social distance between *** use of our proposed pipeline along with a DT of the shared space for visualizing both environmental and human behavior aspects preserves the privacy of individuals and improves the latency of such monitoring systems because only the extracted information is streamed.

关键词： Virtual environment Digital twin 3D visualization Convolutional neural network Object detection Social distancing

Hydroxyapatite composites with carbon allotropes:Preparation,properties,and applications

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Particuology 2024年第5期88卷 239-265页

作者： Boris I.Kharisov Oxana V.Kharissova Lucy T.gonzález Yolanda peña Méndez Igor E.Uflyand Idalia gómez de la Fuente Universidad Autónoma de Nuevo León Ave.UniversidadCiudad UniversitariaSan Nicolás de los GarzaNuevo León 66455Mexico Tecnologico de Monterrey Escuela de Ingeniería y CienciasMonterreyNuevo Leon 64890Mexico Department of Chemistry Southern Federal UniversityRostov-on-DonRussia

Hydroxyapatite(HA)and its composites with inorganic additives,dopants,and polymers is a rapidly developing branch in the materials *** particular,carbon allotropes are widely used in these composites being widely applied for medical *** a gap of insufficient generalization of recent achievements in the field of the HA/Carbon composites,in this review we present the state of the art of the field of HA composites and hybrids with classic carbon allotropes and *** composites are known for carbon nanotubes,nanofibers,graphene and its oxidized forms,as well as,in a lesser grade,for graphite,fullerenes,nanodiamonds,carbon nanofoams,*** composites can be fabricated by a variety of classic and less-common methods,such as co-precipitation(with or without ultrasonic treatment),CVD,hot isostatic pressing,hydrothermal,spark plasma sintering,biomimetic mineralization,thermal and plasma spray,electrochemical and electrophoretic deposition,self-assembling,3D printing,electrospinning,and lyophilisation,among *** of various synthesis techniques can be also carried out for composite *** or synthetic HA can be used as it is for further interaction with carbon allotropes or it can be first prepared and then reacted with carbon counterpart;similarly,carbon allotropes can be introduced into the interaction with HA directly or they can be first synthesized,in particular from *** biocompatible composites can be produced in the form of coatings,powders,and scaffolds and can additionally contain quantitative amounts of third phases,frequently natural or synthetic *** these composites,especially with O-containing functionalizing groups,HA disadvantages could be considerably decreased with simultaneous enhancement of mechanical properties,becoming similar to human bone,chemical stability and biocompatibility,as well as possessing antibacterial ***→g reduction and higher HA decoration were obs

关键词： Hydroxyapatite Carbon nanotubes graphene Quantum dots Fullerenes Nanodiamonds

Partition of Forecast Error into Positional and Structural Components

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Advances in Atmospheric Sciences 2021年第6期38卷 1012-1019页

作者： Isidora JANKOV Scott gREgORY Sai RAVELA Zoltan TOTH Malaquías peÑA global Systems Laboratory NOAA/OARBoulderCO 80305USA general Atomics Electromagnetic Systems GroupLongmontCO 80501USA Earth Signals and Systems group EarthAtmospheric and Planetary SciencesMassachusetts Institute of TechnologyCambridgeMA 02139USA Department of Civil and Environmental Engineering University of Connecticut StorrsCT 06269USA

Weather manifests in spatiotemporally coherent *** forecasts hence are affected by both positional and structural or amplitude *** has been long recognized by practicing forecasters(cf.,e.g.,Tropical Cyclone track and intensity errors).Despite the emergence in recent decades of various objective methods for the diagnosis of positional forecast errors,most routine verification or statistical post-processing methods implicitly assume that forecasts have no positional *** Forecast Error Decomposition(FED)method proposed in this study uses the Field Alignment technique which aligns a gridded forecast with its verifying analysis *** total error is then partitioned into three orthogonal components:(a)large scale positional,(b)large scale structural,and(c)small scale error *** use of FED is demonstrated over a month-long MSLP data *** expected,positional errors are often characterized by dipole patterns related to the displacement of features,while structural errors appear with single extrema,indicative of magnitude *** most important result of this study is that over the test period,more than 50%of the total mean sea level pressure forecast error variance is associated with large scale positional *** importance of positional error in forecasts of other variables and over different time periods remain to be explored.

关键词： forecast error orthogonal decomposition positional structural

Effi ciency of phosphorus accumulation by plankton,periphyton developed on submerged artifi cial substrata and metaphyton:in-situ observation in two shallow ponds

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Journal of Oceanology and Limnology 2021年第3期39卷 928-945页

作者： Marija peĆIĆ Slađana POPOVIĆ Vesna MILUTINOVIĆ gordana SUBAKOV SIMIĆ Ivana TRBOJEVIĆ Dragana PREDOJEVIĆ Institute of Botany and Botanical garden‘Jevremovac’ Faculty of BiologyUniversity of BelgradeBelgrade 11000Serbia Institute of Chemistry Technology and MetallurgyScientific InstitutionNational InstituteCenter for Ecology and TechnoeconomicsUniversity of BelgradeBelgrade 11000Serbia Institute of Public Health of Belgrade Belgrade 11000Serbia

Phosphorus overenrichment of shallow ponds prevailing in wetlands leads to their eutrophication causing the collapse of those vulnerable *** potential of phosphorus accumulation by periphyton developed on artificial substrata has been investigated in two shallow ponds(Bara?ka and?iroki Rit)in northwest Serbia and compared to the same ability of plankton and *** periphyton substrate carrier has been submerged from May to *** continuously(CS)and monthly developed(MS)periphyton were *** component of all investigated communities has been qualitatively *** accumulation of only 14.7 mg TP/m^(2) was recorded in three-month exposed periphyton *** exposed from July to August reached maximal 12.7 mg TP/m^(2).Plankton community that was characterized by more diverse and abundantly developed algal component was more effective in phosphorus accumulation(0.7 mg/g dry weight)in comparison with dominantly inorganic and diatom-dominated periphyton in Bara?*** conditions caused by recent revitalization(dredging organic matter and mud from pond basin—redigging)as well as rapid desiccation of?iroki Rit disabled making an unambiguous conclusion about the efficiency of phosphorus accumulation among different communities,but suggested slight potential of phosphorus harvesting by metaphyton in this *** to the shorter exposure time that brings the reduced risk of unpredictable changes in the ecosystem,as well as the considerable amount of accumulated phosphorus,large-scale application of one-month exposed periphyton developed on artificial substrates would be more advisable for phosphorus harvesting in nutrient affected shallow ponds.

关键词： periphyton phosphorus accumulation shallow ponds (phyto)plankton metaphyton eutrophication