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Flamelet-like models applied in scramjet combustors:A state of art and prospect

Chinese Journal of Aeronautics 2023年第10期36卷 24-43页

作者： Tao TANG Zhenguo WANG Yuhui HUANG Mingbo SUN Hongbo WANG Guoyan ZHAO Jiangfei YU College of Aerospace Science and Engineering National University of Defense TechnologyChangsha 410073China Equipment Project Management Center Equipment Development DepartmentBeijing 100089China

Developing supersonic combustion models with efficiency,accuracy and practicality is important foundation to deeply understand the complex combustion processes in scramjet *** by efficiency and intuition,the flamelet-like models are widely used models in computational combustion ***,the supersonic combustion flow field has the nature of strong compressibility,multiple modality,and multiple scales,which poses a great challenge to the traditional flamelet-like models with fixed boundary conditions,and then the complex chemical reaction mechanisms that may face will impose additional computational *** this context,this paper reviews the flamelet-like models used in scramjet engines,and summarizes prominent issues in the application practice,including modeling partially premixed combustion,defining progress variable,solving temperature efficiently,evaluating assumed Probability Density Function(PDF)models,and treating mixture fraction ***,possible prospects and directions of improvements are proposed and highlighted for the flamelet-like *** fully describe the physicochemical scenario and address the raised challenges,these improvements are dedicated to dealing with the compressibility,temperature rise,time-scales,species of interest,multi-inlet combustion,the progress variable definition,and the higher Mach number flight condition.

关键词： Combustion model Flamelet-like model model improvements Supersonic combustion Scramjet

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Agricultural Fertilization Aggravates Air Pollution by Stimulating Soil Nitrous Acid Emissions at High Soil Moisture

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ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021年第21期55卷 14556-14566页

作者： Wang, Yanan Fu, Xiao Wu, Dianming Wang, Mengdi Lu, Keding Mu, Yujing Liu, Zhiguo Zhang, Yuanhang Wang, Tao Hong Kong Polytech Univ Dept Civil & Environm Engn Hong Kong 999077 Peoples R China Tsinghua Univ Tsinghua Shenzhen Int Grad Sch Inst Environm & Ecol Shenzhen 518055 Peoples R China East China Normal Univ Key Lab Geog Informat Sci Minist Educ Sch Geog Sci Shanghai 200241 Peoples R China Peking Univ Coll Environm Sci & Engn State Key Joint Lab Environm Simulat & Pollut Beijing 100871 Peoples R China Chinese Acad Sci Res Ctr Ecoenvironm Sci Beijing 100049 Peoples R China Univ Chinese Acad Sci Beijing 100049 Peoples R China

Nitrogen lost from fertilized soil is a potentially large source of atmospheric nitrous acid (HONO), a major precursor of the hydroxyl radical. Yet, the impacts of fertilizer types and other influencing factors on HONO emissions are unknown. As a result, the current state-of-the-art models lack an appropriate parameterization scheme to quantify the HONO impact on air quality after fertilization. Here, we report laboratory measurements of high HONO emissions from soils at a 75-95% water-holding capacity after applying three common fertilizers, which contrasts with previous lower predictions at high soil moisture. Urea use leads to the largest release of HONO compared to the other two commonly used fertilizers (ammonium bicarbonate and ammonium nitrate). The significant promotion effect of fertilization lasted up to 1 week. Implementation of the lab-derived parametrization in a chemistry transport model (CMAQ) significantly improved postfertilization HONO predictions at a rural site in the agriculture-intensive North China Plain and increased the regionally averaged daytime OH, O-3, and daily fine particulate nitrate concentrations by 41, 8, and 47%, respectively. The results of our study underscore the necessity to include this large postfertilization HONO source in modeling air quality and atmospheric chemistry. Fertilizer structure adjustments may reduce HONO emissions and improve the air quality in polluted regions with intense agriculture.

关键词： soil HONO emissions fertilization high soil moisture model improvements ambient air pollution

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Improving and calibrating channel erosion simulation in the Water Erosion Prediction Project (WEPP) model

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JOURNAL OF ENVIRONMENTAL MANAGEMENT 2021年 291卷 112616-112616页

作者： Guo, Tian Srivastava, Anurag Flanagan, Dennis C. Purdue Univ Agr & Biol Engn Dept W Lafayette IN 47907 USA Univ Idaho Soil & Water Syst Dept Moscow ID 83843 USA ARS USDA Natl Soil Eros Res Lab W Lafayette IN USA

The Water Erosion Prediction Project (WEPP) model has been widely used to assess the impacts of management practices and climate change on runoff and soil loss at both hillslope and watershed scales. However, the representation of channel erosion processes in WEPP has not been changed significantly since it was released. The current (WEPP v2012.8) and previous WEPP versions assume that channel input erodibility parameters are constant through time, which may lead to erroneous channel detachment predictions, especially for cropland with substantial tillage operations. In this research, the temporally constant values of channel erodibility and critical shear stress were replaced by daily updated values, using the same temporal erodibility and critical shear stress adjustments that are applied in hillslope profile simulations for rill detachment. Observed watershed-scale runoff and soil erosion data from six agricultural watersheds were used to calibrate and compare the WEPP model performance in simulating channel runoff volumes and soil losses before and after the modification. The research showed both WEPP v2012.8 and the modified WEPP model (WEPP_CE) could satisfactorily simulate event-based hydrology and soil erosion at the watershed outlets after calibration. The WEPP_CE model with temporally varying channel erodibility and critical shear stress values demonstrated improved representation of the physical processes in channel soil detachment. Continued improvement in the representation of channel erosion processes in WEPP and other process-based models is needed. The improved WEPP model can be used to evaluate the effectiveness of soil conservation practices on hydrology and erosion in further research.

关键词： Soil detachment Channel erosion Erosion modeling model improvements Agriculture Watershed hydrology

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High Dimensional Data Processing in Privacy Preserving Data Mining 9

High Dimensional Data Processing in Privacy Preserving Data ...

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IEEE 9th International Conference on Communication Systems and Network Technologies (CSNT)

作者： Rathi, Mayur Rajavat, Anand Shri Vaishnav Vidyapeeth Vishwavidyala Dept Comp Sci & Engn Indore India

ISBN: (纸本)9781728149769

In business intelligence data is an essential feature in decision making. An incomplete or lake of information can damage the entire project ideas. Therefore sometimes different business dimensions are collaborating their sensitive and personal data for enhancing decisional ability. During this, the dataset is significantly growing in dimensions. Therefore it is much intense to find a method by which the higher dimensional data can be handled. This paper contributes two key directions of the PPDM (privacy preserving data mining), first a survey conducted on the various PPDM models to understand the working and requirements of the PPDM systems. In addition to an experimental comparative study among PCA, k-PCA and Correlation coefficient based feature selection or dimensionality reduction is conducted. On the basis of experimental observations, the PCA and k-PCA feature selection techniques are degrading the classification accuracy as compared to correlation coefficient based classification. Therefore, in further system design and implementation, the correlation coefficient is used to handling a huge quantity of data dimensions.

关键词： Privacy preserving data mining multi party data source objective summarization model improvements techniques and tools

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A Review of Void Drift models in Subchannel Analysis

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NUCLEAR SCIENCE AND ENGINEERING 2019年第1-2期193卷 33-45页

作者： Mao, Hu Yang, Bao-Wen Wang, Sipeng Xi An Jiao Tong Univ Sch Nucl Sci & Technol Sci & Technol Ctr Adv Nucl Fuel Res & Dev Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ Collaborat Innovat Ctr High End Mfg Equipment Xianning West Rd 28 Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ Qindao Res Inst Qingdao 266300 Peoples R China

Subchannel analysis is widely used in nuclear reactor core thermal-hydraulic calculation and safety analysis. In subchannel analysis, the axial flow is usually treated as the dominant one-dimensional flow, and the lateral flow is simplified as the intersubchannel interactions and is modeled by introduction of semiempirical source terms or separate models. The accuracy of the subchannel analysis is strongly dependent on the modeling of intersubchannel interactions between adjacent subchannels. The intersubchannel interaction can be decomposed into three components: diversion cross flow that occurs due to imposed transverse pressure gradients, turbulent mixing that occurs due to stochastic pressure and flow fluctuations, and void drift that results from lateral migration of the gaseous phase (void) due to a strong tendency of the two-phase system approaching the equilibrium state of phase distribution. This critical review focuses on void drift research. Both experimental observation of the void drift phenomenon and the proposed void drift models are reviewed. The improvements and corresponding assessments of the void drift models are summarized. Following that, further improvements on the void drift model are proposed.

关键词： Void drift models model improvements intersubchannel mixing two-phase flow

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High Dimensional Data Processing in Privacy Preserving Data Mining

High Dimensional Data Processing in Privacy Preserving Data ...

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International Conference on Communication Systems and Network Technologies (CSNT)

作者： Mayur Rathi Anand Rajavat Department of Computer Science & Engineering Shri Vaishnav Vidyapeeth Vishwavidyala Indore India

ISBN: (数字)9781728149769

ISBN: (纸本)9781728149776

In business intelligence data is an essential feature in decision making. An incomplete or lake of information can damage the entire project ideas. Therefore sometimes different business dimensions are collaborating their sensitive and personal data for enhancing decisional ability. During this, the dataset is significantly growing in dimensions. Therefore it is much intense to find a method by which the higher dimensional data can be handled. This paper contributes two key directions of the PPDM (privacy-preserving data mining), first a survey conducted on the various PPDM models to understand the working and requirements of the PPDM systems. In addition to an experimental comparative study among PCA, k-PCA and Correlation coefficient based feature selection or dimensionality reduction is conducted. On the basis of experimental observations, the PCA and k-PCA feature selection techniques are degrading the classification accuracy as compared to correlation coefficient based classification. Therefore, in further system design and implementation, the correlation coefficient is used to handling a huge quantity of data dimensions.

关键词： Privacy preserving data mining multi party data source objective summarization model improvements techniques and tools Data Security dimensional data correlation coefficient (r) Feature extraction personal data data mining

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Functions of decision support systems (JRodos as an example): overview and new features and products

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RADIOPROTECTION 2016年第HS1期51卷 S9-S11页

作者： Raskob, W. Landman, C. Trybushnyi, D. Karlsruhe Inst Technol Hermann von Helmholtz Pl 1 D-76344 Eggenstein Leopoldshafen Germany

Under the auspices of its Euratom Research Framework Programmes, the European Commission (EC) has supported the development of the RODOS (Real-time Online DecisiOn Support) system for off-site emergency management after nuclear accidents for more than a decade. Significant additional funds have been provided by many national research programmes, research institutes and industrial collaborators. In particular, the German Ministry of the Environment, Nature Conservation and Reactor Safety financially contributed to the project with an emphasis on early emergency response. The final result of these collaborative actions, the comprehensive RODOS system, can be applied generally within and across Europe. It can be used in national or regional nuclear emergency centres, provides coherent support at all stages of an accident, and includes the long-term management and restoration of contaminated areas. Within the NERIS-TP project, several model improvements have been developed, covering the worldwide applicability of the system, the coupling with the early notification system of the IAEA, improved countermeasure modelling and model adaptation for the new ICRP 103 recommendations. Several of these new tools were also integrated into the ARGOS system (Hoe S., Muller H., Gering F., Thykier-Nielsen S., Havskov Sorensen J. (2002) ARGOS 2001: A decision support system for nuclear emergencies. In: American Nuclear Society Transactions. Winter Meeting Vol. 87, pp. 574-579).

关键词： RODOS model improvements worldwide applicability countermeasure modelling ARGOS

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Deciding whether and how to improve statewide travel demand models based on transportation planning application needs

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TRANSPORTATION PLANNING AND TECHNOLOGY 2013年第3期36卷 244-266页

作者： Xiong, Chenfeng Zhang, Lei Univ Maryland Dept Civil & Environm Engn College Pk MD 20742 USA

Many states in the USA have developed statewide travel demand models for transportation planning at the state level and along intercity corridors. Travel demand models at mega-region and provincial levels are also widely used in Europe and Asia. With modern transportation planning applications requiring enhanced model capabilities, many states are considering improving their four-step statewide demand models. This paper synthesizes representative statewide models developed with traditional four-step, advanced four-step, and integrated micro-simulation methods. The focus of this synthesis study is as much on model applications and data requirements as on modeling methods. An incremental model improvement approach toward advanced statewide models is recommended. Review findings also suggest model improvement activities should be justified by planning application needs. For statewide model improvement plans to be successful and financially sustainable, the return on model improvement investment needs to be demonstrated by timely applications that rely on improved model capabilities.

关键词： transportation planning travel demand models model applications data requirements model improvements

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Comparison of modelled and measured total CO and NO_x emission rates

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ATMOSPHERIC ENVIRONMENT 2002年第SUP1期36卷 S53-S60页

作者： Kühlwein, J Friedrich, R Kalthoff, N Corsmeier, U Slemr, F Habram, M Möllmann-Coers, M Univ Stuttgart Inst Energy Econ & Rat Use Energy IER D-70665 Stuttgart Germany Univ Karlsruhe Karlsruhe Res Ctr Inst Meteorol & Climate Res IMK D-76021 Karlsruhe Germany Fraunhofer Inst Atmosphar Umweltforsch IFU D-82467 Garmisch Partenkirchen Germany Julich Res Ctr Dept Safety & Radiat Protect ASS D-52425 Julich Germany

Hourly total CO and NO, emission rates determined experimentally from the city of Augsburg, a medium-sized city in southern Germany, were compared with data calculated with a high-resolution emission model. Mass balances based on Aircraft measurements and tracer techniques were used to ascertain real-world emission conditions. On the other hand, comparative emission data were modelled at two different precision levels. A 'default level' represents a mesoscale emission model providing emissions highly resolved in time and space as input data for air quality models. Improved activity data obtained by measurements were used for emission calculations at a 'superior level'. modelled and measured CO emission rates on working days, in general, were found to be in good agreement. CO emissions on Saturday were slightly underestimated by the model. modelled NO, emission rates at both levels agree well with the measurements on working days. On Saturday, the modelled NO,, emission rates are substantially higher than the measured ones, which represent only some 50-60% of the emission estimates. Comparisons between modelled hourly emissions from point sources and spatially highly resolved Aircraft measurements indicate that the temporal allocation of some industrial activities, especially of specific plants with irregular operating hours are very difficult to reflect by the model. (C) 2002 Published by Elsevier Science Ltd.

关键词： urban emission modelling uncertainties mass balance technique tracer technique model improvements

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