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Analytical models of a convective heat exchanger with single-phase coolants

Thermal Engineering 2003年第10期50卷 807-814页

作者： Pikina, G.A. Zhuk, T.I. ul. Krasnokazarmennaya 14 Moscow 111250 Russia

The most accurate among the known linear models of a concurrent-countercurrent convective heat exchanger with distributed parameters is described. Frequency responses of various models are calculated and the analysis is made to prove that the simplifications assumed may be admitted. The latter is accomplished using the economizer of the type TGMP-344A boiler as an example.

关键词： simplification heat exchangers Economizers coolants frequency response distributed parameter ANALYSIS MODELS

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Exponentially weighted moving average chart as a suitable tool for nuchal translucency quality review

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PRENATAL DIAGNOSIS 2014年第4期34卷 367-376页

作者： Hynek, Martin Smetanova, Dagmar Stejskal, David Zvarova, Jana Gennet Ctr Fetal Med & Reprod Genet Prague Czech Republic Inst Comp Sci AS CR European Ctr Med Informat Stat & Epidemiol Prague Czech Republic Charles Univ Prague Fac Med 1 Inst Hyg & Epidemiol Prague Czech Republic Thomayer Hosp Dept Gynecol & Obstet Prague Czech Republic

Objectives This study aimed to design an exponentially weighted moving average (EWMA) chart for the quality review of nuchal translucency (NT) and to assess its performance compared with the methods currently in use: retrospective distribution-based methods and the cumulative sum (CUSUM) chart. Methods The EWMA model was designed for NT quality review using simulation. The NT measurements obtained during routine first-trimester screening in our centre over a two-and-a-half-year period were retrieved from the database. The NT distribution parameters, EWMA and CUSUM chart were established, and the methods were compared. Results On the basis of the results from the simulation, the optimal EWMA settings were established. A set of 9338 NT measurements obtained from nine sonographers was used to construct the EWMA and CUSUM charts and to calculate the distribution parameters. Distribution-based methods were unable to reveal the temporal periods of poor performance. The EWMA model agreed closely with the CUSUM but had the advantage promptly indicating when the process returned to an in-control state, thus extending its use to long-term prospective and retrospective quality assessments. Conclusions The EWMA provides a universal, easy and efficient tool for NT quality review when the prompt and effective detection of suboptimal performance is desired. (c) 2014 John Wiley & Sons, Ltd.

关键词： quality review Control charts Nuchal Translucency Moving average distributed parameter

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TURBULENT FLOW OF A CHEMICALLY REACTIVE GAS SUSPENSION IN A CHANNEL WITH A BLOW

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JOURNAL OF ENGINEERING PHYSICS AND THERMOPHYSICS 2007年第4期80卷 734-741页

作者： Volkov, K. N. Emel'yanov, V. N. DF Ustinov Balt State Tech Univ 1st Krasnoarmeiskaya Str St Petersburg 190005 Russia

The influence of the chemical reactions occurring in the gas phase of a gas suspension flowing in a channel with penetrable walls and the combustion of the condensed-impurity particles in this flow on its gasdynamic structure has been investigated. It is shown that the order of the system of equations defining a flow of a chemically reactive gas suspension with a homogeneous exothermic reaction proceeding at a definite rate and a heterogeneous combustion of the condensed-phase particles can be decreased if certain assumptions are mode. The distributions of the parameters of the gas and dispersed phases were calculated as functions of the rate of blow and the sizes of the particles.

关键词： gaseous phase Combustion GALNS gene blowing Gases System of equations Suspensions PAGR1 gene REACTIVE chemical reactions distributed parameter Turbulent Flow Instruction repertory

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Probabilistic accident consequence uncertainty analysis of the whole program package COSYMA

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RADIATION PROTECTION DOSIMETRY 2000年第3期90卷 365-372页

作者： Ehrhardt, J Jones, JA Goossens, LHJ Forschungszentrum Karlsruhe Inst Kern & Energietechn D-76021 Karlsruhe Germany Natl Radiol Protect Board Didcot OX11 0RQ Oxon England Delft Univ Technol NL-2600 GB Delft Netherlands

The overall uncertainty analysis of the program package COSYMA for assessing the radiological consequences of nuclear accidents builds on the results of a series of individual uncertainty and sensitivity analyses of its submodules. A set of 186 model parameters was identified which contribute most to the uncertainties of endpoints. Probabilistic accident consequence assessments with 144 weather sequences were performed for each of 300 sample sets derived from the uncertainty distributions of these parameters by Latin hypercube sampling. The evaluation of the results provided confidence bounds for the complementary cumulative frequency distributions of endpoints for three different source terms covering a wide range of release fractions. Concluding sensitivity analyses identified the most important model parameters responsible for the uncertainties of endpoints.

关键词： model parameters Nuclear disasters Nuclear Accidents confidence Remainder of a Series Telescoping a series Accidents Uncertainty distributed parameter

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Finite segment model complexity of an Euler-Bernoulli beam

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IFAC-PapersOnLine 2015年第1期28卷 334-340页

作者： Louca, Loucas S. University of Cyprus Department of Mechanical and Manufacturing Engineering Cyprus

A common approach for modeling the dynamic behavior of distributed parameter systems is the approximation through finite-segment models. These models are able to accurately predict the dynamic behavior of the system given that "adequate" segments are included in the model. Frequency-based methodologies can be used to address the complexity of such models. The purpose of the current work is to address the complexity of distributed parameter using the previously developed activity metric. More specifically the complexity of an Euler-Bernoulli beam model is considered. Bond graph models of this system already exist in the literature and the objective is to identify the necessary complexity (number of segments). A new modeling procedure is proposed for this type of systems where the model starts from simple and the number of segments is increased until an activity based criterion is satisfied. An illustrative example is provided to demonstrate the effectiveness of this methodology. © 2015, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.

关键词： Graph theory Bond graph distributed parameter distributed parameter systems Energy based models Euler Bernoulli beams Euler bernoulli beam models Finite segments Model complexity

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Innovation-Weight Parametrization in Data Assimilation: Formulation & Analysis with NAVDAS-AR/NAVGEM

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IFAC-PapersOnLine 2016年第18期49卷 176-181页

作者： Daescu, Dacian N. Langland, Rolf H. Portland State University PortlandOR97207 United States Marine Meteorology Division Naval Research Laboratory MontereyCA93943 United States

An innovation-weight parametrization is introduced as a practical approach to account for deficiencies in the representation of both background error and observation error covariance in a variational data assimilation system. The adjoint-based evaluation of the forecast error sensitivity provides a computationally efficient diagnosis to observation-space distributed parameters and guidance for tuning the analysis Kalman gain operator. Theoretical aspects are discussed and preliminary results are presented with the adjoint versions of the Naval Research Laboratory Atmospheric Variational Data Assimilation System-Accelerated Representer (NAVDAS-AR) and the Navy's Global Environmental Model (NAVGEM). © 2016

关键词： parameter estimation Applications Errors Research laboratories State estimation Computationally efficient distributed parameter Environmental model Naval Research Laboratory Observation errors Performance issues Theoretical aspects Variational data assimilation system

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Analysis of flow instabilities in two-phase natural circulation

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ASME International Mechanical Engineering Congress and Exposition

作者： Wu Geping Jiangsu Univ Sch Energy & Power Engn Zhenjiang Peoples R China

ISBN: (纸本)9780791843826

Safety concerns of nuclear reactors have attracted the attention of researchers on flow instabilities in natural circulation boiling loops. In this theoretical study, a drift flux model which solves the conservation equations of mass, momentum and energy applicable to boiling two-phase natural circulation systems is adopted. The influence of two-phase flow parameters such as drift velocity and void distribution parameter on the loop flow rate is weak. The model is used to analysis the effects of heat flux and inlet subcooling on steady circulation flow rate. High circulation flow rate is accompanied by high heat flux and low inlet subcooling. According to the region and number of meeting points which connects the resistance pressure drop curve and the driving pressure drop curve, flow excursion and density-wave instability sometimes may occur. Further, investigations are carried out to study the effect of heat flux and system pressure on the instabilities region in natural circulation.

关键词： Heat flux flow instability Natural convection recirculating flow conservation equations distributed parameter Flow rates Undercooling Electron mobility Nuclear reactors Effect of heat TWO PHASE FLOW

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Mathematical Model of Overhead Line for Mode Control Based on the Vector Measurements

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IFAC-PapersOnLine 2018年第30期51卷 468-472页

作者： Balametov, A. Khalilov, E. Isayeva, T. Azerbaijan Research Institute of Energetics and Energy Design Azerenerji JSC Baku Azerbaijan

The method and algorithm of increase of accuracy of modeling on regime parameters on the ends of an air-line gained from phasor measurement units-PMU taking into account actual weather conditions is offered. The method is based on sampling of quantity of links of chain model of the air-line, providing a comprehensible accuracy in comparison with instrumental errors PMU. Methodical lapses of the known simplified models of the steady-state in comparison with the equations of an air-line with the distributed parameters on the basis of a sizing up of a condition of a regime are investigated. At conducting of researches parameters of a real line 500 kV have been used. © 2016

关键词： Phasor measurement units Overhead lines Active loss Corona loss distributed parameter Extra high voltage Instrumental error Mode control Steady state Vector measurements

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Fiber-optic sensors based on fluctuation oscillations of waveguide micro-optomechanical resonance structures

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TECHNICAL PHYSICS 2013年第11期58卷 1646-1650页

作者： Egorov, F. A. Sci Ind Co Monitoring Tsentr Moscow 111399 Russia

The characteristics of fiber-optic oscillation frequency sensors of deformation and temperature that employ the thermal fluctuation resonant oscillations in the SMS(M) fiber structures (sensitive elements that represent oscillation systems with distributed parameters based on series-connected single- and multimode step-index fibers) are developed and studied. The measurements of the fluctuation oscillations are based on the amplitude-phase modulation of the optical wave in the multimode oscillating section due to variations in the path-length difference and tunneling of interfering beams. Accuracies of temperature and relative deformation measurements of +/- 2A degrees C and +/- 10(-5), respectively, are demonstrated. The estimation of the ultimate measurement sensitivity of the resonance frequency is based on the approximate calculation of the Allan variance that shows a possibility of the above sensors with temperature and deformation threshold sensitivities of 0.001A degrees C and 10(-8), respectively.

关键词： Fiber-Optic Sensors Structures Allan Variance Temperature Fiber optic sensors Approximate computation Sensors resonant frequencies fluctuations Optical Fibers distributed parameter Light waves

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Distribution parameter and drift velocity for two-phase flow in a large diameter pipe

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NUCLEAR ENGINEERING AND DESIGN 2010年第12期240卷 3991-4000页

作者： Shen, Xiuzhong Matsui, Ryota Mishima, Kaichiro Nakamura, Hideo Kyoto Univ Inst Res Reactor Kumatori Osaka 5900494 Japan Japan Atom Energy Agcy Nucl Safety Res Ctr Tokai Ibaraki 3191195 Japan

In view of practical importance of the drift flux model for two-phase flow analysis in general, and in the analysis of nuclear reactor transients and accidents in particular, the distribution parameter, and the drift velocity have been studied for two-phase flow in a vertical large diameter pipe. In this, study, local measurements were performed on flow parameters, such as void fraction, gas velocity and, liquid velocity in a vertical upward air-water two-phase flow in a pipe of 200 mm inner diameter and, 25 m in height by using the local sensor techniques such as hot-film probes, optical multi-sensor, probes and differential pressure gauges. Two-phase flow regimes in a vertical large diameter pipe, were classified into bubbly, churn and slug flows according to the visual observation. The values of the, distribution parameter and the mean drift velocity were determined directly by their definition using experiment data of the local flow parameters in a two-phase flow in a large diameter pipe. Various existing drift flux correlations were compared with the present experimental results and experimental data obtained by other researchers. A detailed discussion on the problems of these correlations was presented in this paper. Crown Copyright (c) 2010 Published by Elsevier B.V. All rights reserved.

关键词： C_0: distribution parameter j: mixture volumetric flux (m/s) j_g: superficial gas velocity (m/s) j_i: superficial liquid velocity (m/s) Re: Reynolds number et al Electron mobility Pipe Experimental data large diameter distributed parameter PIPE DIAMETER TWO PHASE FLOW LARGE DIAMETER PIPE

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