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An enhanced correlation for gas-particle heat and mass transfer in packed and fluidized bed reactors

CHEMICAL ENGINEERING JOURNAL 2019年 374卷 531-544页

作者： Zhu, Li-Tao Liu, Yuan-Xing Luo, Zheng-Hong Shanghai Jiao Tong Univ State Key Lab Met Matrix Composites Sch Chem & Chem Engn Dept Chem Engn Shanghai 200240 Peoples R China

Particle-resolved (PR) high-fidelity simulations, e.g., direct numerical simulation (DNS), have emerged as a powerful tool to precisely capture the full details of complex fluid-particle heat and mass transfer behaviors. The captured information can be used to constitute closures for unresolved conservation equations. However, such simulations are commonly performed under a specific variety of operating conditions. To broaden the range of closure model applicability, this fundamental study develops an enhanced correlation for the gas-particle transport rate in terms of Nusselt (Sherwood) number via collecting data points (epsilon = [0.35, 1], Re-p = [0, 550]) from open sources. The collected data are predicted with a mean relative error of 9.3%. The extended correlation is then systematically validated by comparison with experimental data and PR-DNS results. Finally, the correlation is applied to integrate with a macroscopic computational fluid dynamics (CFD) reactor model. validation results reveal an enhanced improvement in mass and heat transfer predictions. Moreover, the overall thermal and reactive behaviors computed from the coupled reactor model achieve reasonably good accordance with PR-DNS predictions over various process conditions. The developed correlation is hopeful to improve the accuracy of coarse-grained simulation of interphase heat and mass transfer accompanied by heterogeneously catalyzed chemical reaction.

关键词： Multiphase reactive flows Heat and mass transfer Correlation development CFD modeling model verification and validation

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Character navigation in dynamic environments based on optical flow

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COMPUTER GRAPHICS FORUM 2019年第2期38卷 181-192页

作者： Lopez, Axel Chaumette, Francois Marchand, Eric Pettre, Julien Univ Rennes CNRS INRIA IRISA Rennes France

Steering and navigation are important components of character animation systems to enable them to autonomously move in their environment. In this work, we propose a synthetic vision model that uses visual features to steer agents through dynamic environments. Our agents perceive optical flow resulting from their relative motion with the objects of the environment. The optical flow is then segmented and processed to extract visual features such as the focus of expansion and time-to-collision. Then, we establish the relations between these visual features and the agent motion, and use them to design a set of control functions which allow characters to perform object-dependent tasks, such as following, avoiding and reaching. Control functions are then combined to let characters perform more complex navigation tasks in dynamic environments, such as reaching a goal while avoiding multiple obstacles. Agent's motion is achieved by local minimization of these functions. We demonstrate the efficiency of our approach through a number of scenarios. Our work sets the basis for building a character animation system which imitates human sensorimotor actions. It opens new perspectives to achieve realistic simulation of human characters taking into account perceptual factors, such as the lighting conditions of the environment.

关键词： CCS Concepts • Computing methodologies → modeling and simulation model development and analysis model verification and validation Animation

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Analyzing El Nino-Southern Oscillation Predictability Using Long-Short-Term-Memory models

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EARTH AND SPACE SCIENCE 2019年第2期6卷 212-221页

作者： Huang, Andrew Vega-Westhoff, Ben Sriver, Ryan L. Univ Illinois Dept Atmospner Sci Urbana IL 61801 USA

El Nino-Southern Oscillation (ENSO) can have global impacts, affecting daily temperature and precipitation, and extreme weather, such as hurricanes and tornadoes. Because of its importance, scientists strive to understand the processes that govern ENSO and develop models to predict its evolution and changes in variability. Here long-short-term-memory models (LSTMs) were compared to linear regression models (LR) to explore the benefits of simple, deep neural networks in predicting ENSO, in addition to quantifying the relative importance of the sources of ENSO's predictability. The models use central Pacific sea surface temperatures (SST), equatorial Pacific warm water volumes, and western Pacific zonal winds as predictors, individually and in combinations, on monthly and daily resolutions, from 1- to 11-month leads. By using these predictors, many characteristic time scales are encompassedfrom days-to-weeks in the atmosphere, to months-to-seasons in the coupled system, and interseasonal-to-interannual in the subsurface ocean. Results show, with monthly input, predictions from LSTM were like predictions from LR. However, with daily SST at longer leads, LSTM exhibited some advantage over LR in terms of the correlation coefficient. This suggests that daily SST may contain some nonlinear element that improves LSTM predictability compared to LR. In addition, this suggests that more information, such as gridded data and additional variables, would likely improve predictability using LSTM, but results would be more difficult to interpret. Overall, LSTM may be appealing because once the computationally expensive training of LSTM is complete, the predictions employing the trained model can be relatively cheap to perform thereafter.

关键词： modeling model verification and validation neural networks fuzzy logic

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Research on permeability coefficient of a polyethylene controlled-release film coating for urea and relevant nutrient release pathways

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POLYMER TESTING 2017年 59卷 90-98页

作者： Wei, Ya Li, Juan Li, Yanting Zhao, Bingqiang Zhang, Ligan Yang, Xiangdong Chang, Jiang Chinese Acad Agr Sci Inst Agr Resources & Reg Planning Key Lab Plant Nutr & Fertilizer Minist Agr Beijing 100081 Peoples R China Anhui Agr Univ Sch Resources & Environm Hefei 230036 Peoples R China

The permeability coefficient is a key factor that reflects the nutrient release capability of polymer-coated fertilizers. To investigate the permeability coefficient of polyethylene (PE) controlled-release film and to determine the difference between the controlled-release film and a dense membrane, we designed a film permeation device to measure the permeability coefficient of a PE controlled-release film coating for urea, and a mathematical model was used to check the accuracy of these measurements. By measuring the permeation coefficient of a dense, PE membrane, the compactness of the PE controlled-release film was analyzed, and the nutrient release pathway of PE-coated fertilizer was discussed. Research indicated that urea was constantly released through PE controlled-release film and the permeability coefficient remained constant. The permeability coefficient for PE controlled-release film coating on urea with 1-4 months release time was in the range of 7.17-18.7E-15 m(2)/s with 2.6 times difference between the maximum and minimum. The permeability coefficient decreased as the release time increased, conforming to the inversely proportional relationship between permeation amount and time in the nutrient release model. It is investigated that the measured values are close to the theoretical values and can be used in model calculation. The urea permeability coefficient of PE dense membrane was 7.11E-18 m(2)/s, which is 1000-2600 times smaller than that of the PE controlled-release film. The contribution of permeability of polymer material itself is negligible. It can be concluded that PE controlled-release film is not a dense membrane but porous and that nutrient release is mainly determined by pore configuration of the film. (C) 2017 Elsevier Ltd. All rights reserved.

关键词： Polyethylene controlled-release urea Film Permeability coefficient model verification and validation Nutrient release pathway

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Effects of parameter indeterminacy in pelagic biogeochemical modules of Earth System models on projections into a warming future: The scale of the problem

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GLOBAL BIOGEOCHEMICAL CYCLES 2017年第7期31卷 1155-1172页

作者： Loeptien, U. Dietze, H. GEOMAR Helmholtz Ctr Ocean Res Kiel Kiel Germany Christian Albrechts Univ Kiel Inst Geosci Kiel Germany

Numerical Earth System models are generic tools used to extrapolate present climate conditions into a warming future and to explore geoengineering options. Most of the current-generation models feature a simple pelagic biogeochemical model component that is embedded into a three-dimensional ocean general circulation model. The dynamics of these biogeochemical model components is essentially controlled by so-called model parameters most of which are poorly known. Here we explore the feasibility to estimate these parameters in a full-fledged three-dimensional Earth System model by minimizing the misfit to noisy observations. The focus is on parameter identifiability. Based on earlier studies, we illustrate problems in determining a unique estimate of those parameters that prescribe the limiting effect of nutrient-and light-depleted conditions on carbon assimilation by autotrophic phytoplankton. Our results showcase that for typical models and evaluation metrics no meaningful "best" unique parameter set exists. We find very different parameter sets which are, on the one hand, equally consistent with our (synthetic) historical observations while, on the other hand, they propose strikingly differing projections into a warming climate.

关键词： biogeochemical ocean modeling model verification and validation parameter estimation future projections uncertainty Earth System model

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A Systematic Map on Verifying and Validating Software Process Simulation models

A Systematic Map on Verifying and Validating Software Proces...

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International Conference on Software and System Process (ICSSP)

作者： Gong, Haojie Zhang, He Yu, Dexian Liu, Bohan Nanjing Univ Software Inst Nanjing Jiangsu Peoples R China

ISBN: (纸本)9781450352703

verification and validation (V&V) is a critical step in software process modelling to secure the model's quality and credibility. Software Process Simulation models (SPSMs) that are based on descriptive process models offer the executability that is able to demonstrate the dynamic changes of software process over time. The V&V of process simulation models go beyond static process models and turn to be more complex and challenging to software modelers. This study aims to identify what aspects of process simulation models are verified and validated by using which V&V methods in what conditions in software engineering research. We conducted a systematic literature review (mapping study) on the studies of software process simulation that report of their V&V activities. We identified 72 relevant studies from a pool of 331 papers on SPSM until 2015. These studies can be mapped to ten V&V methods applied for five aspects of process models to be verified and validated, i.e., syntactic quality, semantic quality, pragmatic quality, performance, and value. A systematic map is presented to illustrate the relationships between the identified V&V methods and their supporting aspects of process models. This mapping will provide the community reference value when developing, verifying, and validating software process (simulation) models.

关键词： model verification and validation process modeling process simulation systematic mapping study

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Quantitative Interpretation of Air Radon Progeny Fluctuations in Terms of Stability Conditions in the Atmospheric Boundary Layer

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BOUNDARY-LAYER METEOROLOGY 2016年第3期160卷 529-550页

作者： Salzano, Roberto Pasini, Antonello Casasanta, Giampietro Cacciani, Marco Perrino, Cinzia Natl Res Council Italy Inst Atmospher Pollut Res I-50019 Florence Italy Natl Res Council Italy Inst Atmospher Pollut Res I-00015 Rome Italy Natl Res Council Italy Inst Atmospher Sci & Climate I-00155 Rome Italy Univ Roma La Sapienza Dept Phys I-00145 Rome Italy

Determining the mixing height using a tracer can improve the information obtained using traditional techniques. Here we provide an improved box model based on radon progeny measurements, which considers the vertical entrainment of residual layers and the variability in the soil radon exhalation rate. The potential issues in using progeny instead of radon have been solved from both a theoretical and experimental perspective;furthermore, the instrumental efficiency and the counting scheme have been included in the model. The applicability range of the box model has been defined by comparing radon-derived estimates with sodar and lidar data. Three intervals have been analyzed ("near-stable", "transition" and "turbulent"), and different processes have been characterized. We describe a preliminary application case performed in Rome, Italy, while case studies will be required to determine the range limits that can be applied in any circumstances.

关键词： Aerosols and particles Boundary-layer processes Geochemical cycles model verification and validation modelling

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Interannual variability of tropical cyclone activity and regional Hadley circulation over the Northeastern Pacific

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GEOPHYSICAL RESEARCH LETTERS 2015年第7期42卷 2473-2481页

作者： Zhang, Gan Wang, Zhuo Univ Illinois Dept Atmospher Sci Urbana IL 61820 USA

The interannual variability of the regional Hadley circulation (HC) and tropical cyclone (TC) activity over the Northeastern Pacific (NEP) was investigated. The interannual variability of the HC in the NEP hurricane season is found dominated by a mode (M1EP) regulating the strength and meridional extent of the Intertropical Convergence Zone. M1EP has a more robust correlation with NEP TC activity than the El Nino-Southern Oscillation sea surface temperature indices. The strong correlation is attributed to the impacts of M1EP on environmental conditions. In addition, the leading mode of the Atlantic HC, which has an anticorrelation with M1EP, also strongly impacts NEP TC activity. The findings, together with Zhang and Wang (2013), highlight the role of the HC in controlling the variability of TC activity as well as the interbasin connection between the NEP and the Atlantic. The regional HC is thus recommended as a useful metric to benchmark models in simulating TC activity.

关键词： tropical cyclones ocean atmosphere interactions climate change and variability general circulation ENSO model verification and validation

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Development of an Assessment Tool of the Effects of ITS on CO2 Emissions

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INTERNATIONAL JOURNAL OF INTELLIGENT TRANSPORTATION SYSTEMS RESEARCH 2013年第3期11卷 129-140页

作者： Kuwahara, Masao Horiguchi, Ryota Hayashi, Seiji Tanaka, Shinji Tohoku Univ Grad Sch Informat Sci Sendai Miyagi Japan I Transport Lab Co Ltd Tokyo Japan Japan Automot Res Inst Tokyo Japan Yokohama Natl Univ Yokohama Kanagawa Japan

Some Intelligent Transport Systems (ITS) technologies are expected to effectively reduce energy consumption and carbon dioxide (CO2) emissions from vehicular highway traffic, which contributes about 20 % of CO2 emissions in Japan. The paper proposes a classification of ITS solutions regarding their effects on the reduction. A newly developed method, consisting of a traffic simulation (TS), an emission model (EM) and a harmonization of those models, is introduced, and its efficiency and reliability are examined by a verification and validation procedure. The procedure is collaboratively developed with specialists from the EU and USA during a 5-year research activity between 2008 and 2013. Application trials of the method are also demonstrated and the effectiveness of the developed method proved to be applicable for evaluating the reduction of vehicular traffic CO2 emissions.

关键词： Carbon dioxide emission Traffic simulation model Emission model model verification and validation

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Formal verification and validation of DEVS Simulation models

Formal Verification and Validation of DEVS Simulation Models

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AFRICON Conference

作者： Olamide, Soremekun Ezekiel Kaba, Traore Mamadou African Univ Sci & Technol Abuja Nigeria Univ Blaise Pascal LIMOS CNRS UMR 6158 Clermont Ferrand 2 France

ISBN: (纸本)9781467359405

We present a model-based verification technique built on selective and pragmatic use of formal methods, by using simplified model checking tools that focus on error detection rather than formalized proofs. This framework is to check and confirm that the trajectories and events of DEVS-Driven modeling Language (DDML) simulation models and that of the real system agree in order to achieve replicative, predictive and structural validity through the lightweight application of formal methods. This is to reduce and ease the Simulation model verification efforts while increasing the coverage of the process, in order to verify the transformational accuracy of the model development process, increase confidence in the simulation model and allow for performance evaluation of simulation models. This framework provides a model refinement iterative procedure that helps to enhance the DEVS Simulation model, correct errors or adapt to changing contextual requirements. This refinement procedure is applicable to evolutionary software development and systems requiring rapid prototyping, in order to meet up with changing requirements of such systems with the aid of iterative refinement. Furthermore, we present a case study example of a GSM telecommunication system to reveal the ability of this framework to not only formally verify system but also refine their models.

关键词： DEVS DDML Formal Methods model verification and validation model- Refinement GSM

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