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Correction factor of lumped parameter model for linearly tapered piezoelectric cantilever

JOURNAL OF INTELLIGENT MATERIAL SYSTEMS AND STRUCTURES 2022年第3期33卷 474-488页

作者： Ismail, Mai R. Omar, Farag K. Ajaj, Rafic Ghodsi, Mojtaba United Arab Emirates Univ Dept Mech Engn Al Ain U Arab Emirates Khalifa Univ Sci & Technol Dept Aerosp Engn Abu Dhabi U Arab Emirates Univ Portsmouth Sch Energy & Elect Engn Portsmouth Hants England

distributed parameter model (DPM) gives an accurate representation of the vibration response of piezoelectric cantilevers. Nevertheless, lumped parameter model (LPM) has been widely used because of its simple mathematical representation. However, researchers developed a correction factor for LPM because of its inaccurate power output prediction of the piezoelectric harvesters. The developed correction factors were limited to the rectangular and exponentially tapered piezoelectric beams because the DPM of other shaped beams are rather complicated to derive. This paper presents a correction factor for linearly tapered piezoelectric cantilever beam using a finite element model (FEM) approach. Validation of the developed FEM is accomplished using two analytical models from literature of rectangular and exponentially tapered shapes with tip mass. Results show an excellent agreement between the FEM and the related DPM. The FEM of a linearly tapered piezoelectric cantilever is then built and the error of using the uncorrected LPM for different tapered ratios is investigated. Correction factors of different taper ratios subjected to various tip masses are developed. Comparisons between the corrected LPM and the FEM verify the estimation of the correction factor. Results show that FEM approach can be used to enhance the accuracy of LPM of piezoelectric cantilever harvesters.

关键词： Tapered piezoelectric cantilever correction factor lumped parameter model distributed parameter model finite element model tip mass effect

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Role of pH in partitioning and cation exchange of aromatic amines on water-saturated soils

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CHEMOSPHERE 2001年第4期44卷 627-635页

作者： Li, H Lee, LS Fabrega, JR Jafvert, CT Purdue Univ Dept Agron W Lafayette IN 47907 USA Purdue Univ Sch Civil Engn W Lafayette IN 47907 USA

Predicting the reversible interactions between aromatic amines and soil is essential for assessing the mobility, bioavailability and exposure from contaminated sites. Reversible sorption mechanisms of aniline and alpha -naphthylamine were investigated by using single and binary solute sorption to five soils at several pH values, and by applying a distributed parameter (DP) model. The DP model assumes linear partitioning of the neutral species into soil organic matter domains and organic cation binding on negative-charged sites with the exchange coefficients represented by a Gaussian probability distribution. Sorption nonlinearity was attributed to cation exchange with varying site affinities, which was adequately simulated using the DP model. Greater uptake by hydrophobic partitioning and selectivity for cation exchange sites was observed for alpha -naphthylamine compared to aniline. Sorption of alpha -naphthylamine was not impacted quantitatively by aniline under those conditions examined;however, aniline sorption was reduced by alpha -naphthylamine with the largest reduction occurring in the soil with the lowest pH. DP model simulations showed that although hydrophobic partitioning increases with soil-solution pH, cation exchange still contributes significantly to the total sorption even at soil-solution pH values greater than pK(a) + 2. (C) 2001 Elsevier Science Ltd. All rights reserved.

关键词： competitive sorption speciation aromatic amine distributed parameter model cation exchange partitioning

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Thermal performance calculation and analysis of heat transfer tube in super open rack vaporizer

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APPLIED THERMAL ENGINEERING 2016年 93卷 27-35页

作者： Pan, Jie Li, Ran Lv, Tao Wu, Gang Deng, Zhian Xian Shiyou Univ Coll Petr Engn Xian 710065 Shaanxi Provinc Peoples R China

As one of the most widely-used liquefied natural gas (LNG) vaporizer, super open rack vaporizer (SuperORV) consists of panel-shaped heat transfer tubes with duplex tube configuration. In this paper, an energy balance-based distributed parameter model for predicting the thermal performance of SuperORV heat transfer tube was developed, where introduces numerous empirical correlations. The results from the model exhibit a good agreement with the experimental data, which implies the calculation model is reliable. Based on this, the heat transfer process of SuperORV heat transfer tube was simulated numerically, the bulk fluid and metal temperature profiles along the heat transfer tube was obtained at the condition with ice formation and heat transfer enhancement measures, the thermal performance of SuperORV heat transfer tube was analyzed, and the effects of operating parameters and heat transfer enhancement measures on the thermal performance were discussed. The results show that the operating parameters have important effects on the thermal performance of heat transfer tube, and the heat transfer enhancement measures can improve the heat transfer performance markedly. The required minimum tube length while both inner fin and twisted tape insert were applied is shortened by 60% compared with that without heat transfer enhancement measures. (C) 2015 Elsevier Ltd. All rights reserved.

关键词： LNG SuperORV Heat transfer tube distributed parameter model Thermal performance

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modeling and simulation of an industrial falling film evaporator for alumina production

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CHEMICAL ENGINEERING RESEARCH & DESIGN 2020年 154卷 303-315页

作者： Wang, Xiaoli Xiong, Pan Sun, Kaixuan Xie, Yongfang Yang, Chunhua Cent S Univ Sch Automat Changsha 410083 Peoples R China Texas A&M Univ Texas A&M Energy Inst College Stn TX 77843 USA

This paper describes a mathematical model developed by combining a lumped parameter model (LPM) and a distributed parameter model (DPM) for an industrial falling film evaporator used for the evaporation of a sodium aluminate solution (SAS) during the alumina production process. In the LPM, the dynamic equations were deduced to calculate the concentration of the evaporator outlet. The DPM was developed to study the evaporation occurring in each heating tube, in which the residence time, film thickness, liquid load of the feed, and the amount of heat transfer were established as functions of the longitudinal location from the entrance down the tube. Material properties related to the compositions, such as the density and viscosity, were fitted from industrially measured data acquired during a heat balance test. The modeling of the overall heat transfer coefficient based on fluid mechanics is discussed. The effect of scaling, which is an obstacle to accurate modeling, was considered using the industrial history data combined with the calculations of the mass and heat balance equations. The simulated concentrations of the products revealed the high accuracy of the model. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

关键词： Falling film evaporator Alumina Lumped parameter model distributed parameter model

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Dynamic and energetic characteristics of a bistable piezoelectric vibration energy harvester with an elastic magnifier

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MECHANICAL SYSTEMS AND SIGNAL PROCESSING 2018年 105卷 427-446页

作者： Wang, Guangqing Liao, Wei-Hsin Yang, Binqiang Wang, Xuebao Xu, Wentan Li, Xiuling Zhejiang Gongshang Univ Sch Informat & Elect Engn Hangzhou 310018 Zhejiang Peoples R China Chinese Univ Hong Kong Dept Mech & Automat Engn Shatin Hong Kong Peoples R China

Bistable piezoelectric energy harvesters are being increasingly seen as an alternative to batteries in low-power devices. However, their energy harvesting characteristics are limited. To enhance these, we use a configuration including an elastic magnifier to amplify base excitation and provide sufficient kinetic energy to overcome potential well barriers, thus leading to large-amplitude bistable motion. We derive the distributed parameter mathematical model of this configuration by using Hamilton's principle. We then investigate the nonlinear dynamic behaviors and energetic characteristics and analyze the bifurcation for the equilibrium solution of the model. The simulations and experiments show high electromechanical responses and energy generation characteristics of the proposed system over a broad frequency band. The results suggest that, compared with a typical bistable piezoelectric energy harvester, the proposed energy harvester system with an elastic magnifier can provide higher output over a broader frequency band at lower excitation levels by adjusting the system's mass and stiffness ratios. (C) 2017 Elsevier Ltd. All rights reserved.

关键词： Bistable energy harvester Elastic magnifier Dynamic behavior Energetic characteristics Bifurcation analysis distributed parameter model

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Can we simulate regional groundwater flow in a karst system using equivalent porous media models? Case study, Barton Springs Edwards aquifer, USA

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JOURNAL OF HYDROLOGY 2003年第1-4期276卷 137-158页

作者： Scanlon, BR Mace, RE Barrett, ME Smith, B Univ Texas Jackson Sch Geosci Bur Econ Geol Austin TX 78758 USA Texas Water Dev Board Capitol Stn Austin TX 78711 USA Univ Texas Ctr Res Water Resources Austin TX 78758 USA Barton Springs Edwards Aquifer Conservat Dist Austin TX 78748 USA

Various approaches can be used to simulate groundwater flow in karst systems, including equivalent porous media distributed parameter, lumped parameter, and dual porosity approaches, as well as discrete fracture or conduit approaches. The purpose of this study was to evaluate two different equivalent porous media approaches: lumped and distributed parameter, for simulating regional groundwater flow in a karst aquifer and to evaluate the adequacy of these approaches. The models were applied to the Barton Springs Edwards aquifer, Texas. Unique aspects of this study include availability of detailed information on recharge from stream-loss studies and on synoptic water levels, long-term continuous water level monitoring in wells throughout the aquifer, and spring discharge data to compare with simulation results. The MODFLOW code was used for the distributed parameter model. Estimation of hydraulic conductivity distribution was optimized by using a combination of trial and error and automated inverse methods. The lumped parameter model consists of five cells representing each of the watersheds contributing recharge to the aquifer. Transient simulations were conducted using both distributed and lumped parameter models for a 10-yr period (1989-1998). Both distributed and lumped parameter models fairly accurately simulated the temporal variability in spring discharge;therefore, if the objective of the model is to simulate spring discharge, either distributed or lumped parameter approaches can be used. The distributed parameter model generally reproduced the potentiometric surface at different times. The impact of the amount of pumping on a regional scale on spring discharge can be evaluated using a lumped parameter model;however, more detailed evaluation of the effect of pumping on groundwater levels and spring discharge requires a distributed parameter modeling approach. Sensitivity analyses indicated that spring discharge was much more sensitive to variations in recharge

关键词： distributed parameter model equivalent porous media groundwater modeling karst hydrogeology lumped parameter model water resources management

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Design of microchannel Fischer-Tropsch reactor using cell-coupling method: Effect of flow configurations and distribution

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CHEMICAL ENGINEERING SCIENCE 2016年 143卷 63-75页

作者： Park, Seongho Jung, Ikhwan Lee, Yongkyu Kshetrimayum, Krishnadash S. Na, Jonggeol Park, Seongeon Shin, Seolin Ha, Daegeun Lee, Yeongbeom Chung, Jongtae Lee, Chul-Jin Han, Chonghun Seoul Natl Univ Sch Chem & Biol Engn Gwanak Ro 599 Seoul 151742 South Korea Seoul Natl Univ Engn Dev Res Ctr Gwanak Ro 599 Seoul 151742 South Korea Korea Gas Corp DME GTL Technol Res Ctr Incheonsinhang Daero 960 Inchon 406840 South Korea

The objective of this study is to design a microchannel Fischer-Tropsch reactor with the evaluation of several flow configurations and distribution effect. A cell coupling computation was carried out for the microchannel reactor of five different flow configurations. In the cell coupling method, all the process and cooling channels are decomposed into a number of unit cells, and then coupled to solve the material and energy balances. The realistic flow distribution effect was incorporated into the model by using results obtained from computational fluid dynamics (CFD). The kinetic model was validated with experimental data, and the results of the reactor model was compared with data taken from the literature and the results were found to be in good agreement. Several case studies were conducted to see the effect of flow configurations, flow distribution, and catalyst loading zones. It was observed that the geometry of cross-co-cross current was found to give the best performance among the designs considered. The study also reveals that flow distribution and catalyst loading zone need to be carefully controlled for the safe, robust, and reliable reactor design and operation. (C) 2016 Published by Elsevier Ltd.

关键词： Fischer-Tropsch Microchannel reactor Reactor design distributed parameter model Gas-to-Liquid process

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Particle-bed model for multicomponent adsorption-based separations: application to pressure swing adsorption

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CHEMICAL ENGINEERING SCIENCE 1999年第23期54卷 5647-5666页

作者： Serbezov, A Sotirchos, SV Univ Rochester Dept Chem Engn Rochester NY 14627 USA Inst Chem Engn & High Temp Chem Proc Patras 26500 Greece

A generalized nonisothermal particle-bed model for multicomponent adsorption-based separations is developed in this study. The multicomponent mass transport is described by the D'Arcy's law in the adsorbent bed and by the dusty-gas model in the adsorbent particles. No restrictions are imposed on the number of species in the multicomponent mixture. Appropriate boundary conditions are formulated for all the basic steps in an adsorptive separation scheme. The model is solved by a combination of the collocation and the subdomain methods of weighted residuals. A four-step pressure swing adsorption process for production of oxygen-enriched product from air using zeolite 5A as an adsorbent is employed as a model system for the application of the particle-bed model. The model is tested under various conditions of operations, and its predictions are discussed in the context of past analytical results and experimental observations. The results show that nonisothermal pressure swing adsorption processes approach their cyclic steady states very slowly because of the slow build up of the temperature profiles. II is also found that the external heat transport limitations at the outer surface of the adsorbent particles have no effect on the nonisothermal operation of the adsorbent beds, and it is thus concluded that a single energy equation for the macroscopic variation of the temperature in the bed would suffice in almost all practical applications. The particle-bed model is found to be superior to the lumped-parameter models for the case of strong intraparticle mass transport limitations. (C) 1999 Elsevier Science Ltd. All rights reserved.

关键词： pressure swing adsorption distributed parameter model multicomponent mass transport dusty-gas model generalized linear driving force approximation heat transport

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Collaborative simulation for dynamical PEMFC power systems

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INTERNATIONAL JOURNAL OF HYDROGEN ENERGY 2010年第16期35卷 8772-8782页

作者： Zhai, Shuang Sun, Pengtao Chen, Fengxiang Zhou, Su Zhang, Chuansheng Tongji Univ Coll Automot Engn Shanghai 201804 Peoples R China Univ Nevada Dept Math Sci Las Vegas NV 89154 USA

In this paper a collaborative simulation platform for proton exchange membrane fuel cell (PEMFC) power systems is presented, where the stack is simulated by a two-phase distributed parameter model and the auxiliary units by lumped parameter models. By exchanging the dynamic data between the external load/auxiliary units and PEMFC stack, dynamic simulation of PEMFC stack has been carried out during the load changes for various states associated with different characteristic variables. The internal states of the stack can be observed due to variation of external load/auxiliary units. Numerical experiments are provided for a special case with multiple cycles of load changes derived from an acceleration mode of a fuel cell vehicle. The numerical results demonstrate that the "undershoot" of output voltage is due to the response lag of the auxiliary units and liquid water accumulation in the fuel cell stack. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.

关键词： PEMFC Collaborative simulation Dynamic response Undershoot distributed parameter model Lumped parameter model

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Stabilization for continuum models of large space structures in large attitude maneuvers

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EUROPEAN JOURNAL OF CONTROL 2002年第4期8卷 361-372页

作者： De Santis, A Di Gennaro, S Univ Aquila Dipartimento Ingn Elettr I-67040 Laquila Italy Univ Roma La Sapienza Dipartimento Informat & Sistemist I-00184 Rome Italy

In this work we consider an infinite dimensional model of a large space structure with flexible elements. The control purpose consists of ensuring stability while performing large slew maneuvers. To this aim, a suitably accurate description of the nonlinear coupling between the rigid and the flexible motions of a spacecraft with flexible appendages is necessary. A control law from the state, ensuring global stabilization of the closed-loop solutions for any initial condition, is designed. Furthermore, considering the practical problems arising from the implementation of such a feedback, a control law from the output guaranteeing semiglobal stabilization, i.e., for any initial condition in a chosen region, is proposed. As opposite to the finite dimensional approach, which suffers the spillover effect, the proposed controllers ensure the asymptotic stabilization of all the modes.

关键词： large flexible structure distributed parameter model stabilization boundary control

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