The Kinematic Analysis and Simulation of the Large-Scale Linear Vibration Screen

2012 ◽  
Vol 215-216 ◽  
pp. 726-729 ◽  
Author(s):  
Xin Du
Keyword(s):  
Dynamic Model ◽  
Kinematic Analysis ◽  
Large Scale ◽  
Vertical Direction ◽  
Model Parameters ◽  
Linear Vibration ◽  
Theory Analysis ◽  
Kinematic Theory ◽  
Reasonable Range ◽  
Displacement Equation

The kinematic analysis had carried on large-scale linear vibration screen, which was based on the theory of multi-rigid-body system and the theory of self-synchronous vibration. According to the dynamic analysis, the displacement equation was established. The vibration screen of motion was decomposed into two vertical directions. It included the vertical direction and the horizontal direction. The model of vibration screen is analyzed in the vertical direction. The dynamic model is established and analyzed by COSMOSMotion software. The paper is consisted of three parts.1) Kinematic theory analysis of double motors on the linear vibrating machine. 2) Dynamic model is built. Fixed frame is replaced with simple parts in order that the model is observed later. Through the motion analysis of the vertical direction, it is concluded that the different stiffness of the spring group was corresponding to the moving distance. 3) It is judged that reasonable range of spring parameters and the system damping, and model parameters will be modified

Canyon Building Ventilation System Dynamic Model Optimization Study

1993 ◽  
Author(s):  
Franklin F. K. Chen ◽  
B. Ronald Moncrief
Keyword(s):  
Dynamic Model ◽  
Parameter Space ◽  
Large Scale ◽  
Age Factors ◽  
Ventilation System ◽  
Operating Conditions ◽  
Data Availability ◽  
Model Parameters ◽  
Desktop Computer ◽  
Plant Data

Abstract A canyon building houses special nuclear material processing facilities in two canyon like structures, each with approximately a million cubic feet of air space and a hundred thousand hydraulic equivalent feet of ductwork of various cross sections. The canyon ventilation system is a “once through” design with separate supply and exhaust fans, utilizes two large sand filters to remove radionuclide particulate matter, and exhausts through a tall stack. The ventilation equipment is similar to most industrial ventilation systems. However, in a canyon building, nuclear contamination prohibits access to a large portion of the system and therefore limits the kind of plant data possible. The facility investigated is 40 years old and is operating with original or replacement equipment of comparable antiquity. These factors, access and aged equipment, present a challenge in gauging the performance of canyon ventilation, particularly under uncommon operating conditions. The ability to assess canyon ventilation system performance became critical with time, as the system took on additional exhaust loads and aging equipment approached design maximum. Many “What if?” questions, needed to address modernization/safety issues, are difficult to answer without a dynamic model. This paper describes the development, the validation and the utilization of a dynamic model to analyze the capacity of this ventilation system, under many unusual but likely conditions. The development of a ventilation model with volume and hydraulics of this scale is unique. The resultant model resolutions of better than 0.05″wg under normal plant conditions and approximately 0.2″wg under all plant conditions achievable with a desktop computer is a benchmark of the power of micro-computers. The detail planning and the persistent execution of large scale plant experiments under very restrictive conditions not only produced data to validate the model but lent credence to subsequent applications of the model to mission oriented analysis. Modelling methodology adopted a two parameter space approach, rational parameters and irrational parameters. Rational parameters, such as fan age-factors, idle parameters, infiltration areas and tunnel hydraulic parameters are deduced from plant data based on certain hydraulic models. Due to limited accessibility and therefore partial data availability, the identification of irrational model parameters, such as register positions and unidentifiable infiltrations, required unique treatment of the parameter space. These unique parameters were identified by a numerical search strategy to minimize a set of performance indices. With the large number of parameters, this further attests to our strategy in utilizing the computing power of modern micros. Nine irrational parameters at five levels and 12 sets of plant data, counting up to 540 runs, were completely searched over the time span of a long weekend. Some key results, in assessing emergency operation, in evaluating modernization options, are presented to illustrate the functions of the dynamic model.

A simplified dynamic model with driver’s NMS characteristic for human-vehicle shared control of autonomous vehicle

2021 ◽  
pp. 095440702110189
Author(s):  
Huateng Wu ◽  
Hanbing Wei ◽  
Zheng Liu ◽  
Jin Xu
Keyword(s):  
Dynamic Model ◽  
Autonomous Vehicles ◽  
Large Scale ◽  
Autonomous Vehicle ◽  
Lyapunov Stability Theory ◽  
Shared Control ◽  
Steering Wheel ◽  
Adaptive Genetic Algorithm ◽  
Model Parameters ◽  
Control Authority

Since the large-scale application of fully autonomous vehicles is difficult to be commercialized in the short term, human-vehicle shared control (HVSC) is a promising technique. To implement the control authority allocation and observe the driver characteristic, it is essential to develop an efficient HVSC dynamic model with the driver’s neuromuscular characteristic (NMS). To further our previous research, a simplified HVSC dynamic model is proposed in this paper. This model simplifies the non-critical NMS parameters such as muscle spindle feedback, which has no significant feedback effect while retaining essential NMS characteristics such as stretch reflection and intrinsic properties. The model consists of a model predictive controller (MPC) coupled with a driver NMS model and a 2 DOF vehicle model. The stability is proved by Lyapunov stability theory. Moreover, a field experiment was conducted for validation of the model. The V-Box is utilized to measure the vehicle’s state signals, such as steering wheel angle and pedal stroke. Subsequently, the adaptive genetic algorithm (AGA) is employed to identify the model parameters based on the experimental results. The comparison between the experiment and the model output shows that the proposed model can accurately represent the driver’s NMS characteristics and vehicle dynamic parameters. This paper will serve as a theoretical basis for the control authority allocation for L3 class autonomous vehicles.

scholarly journals A modular microfluidic system based on a multilayered configuration to generate large-scale perfusable microvascular networks

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Tao Yue ◽  
Da Zhao ◽  
Duc T. T. Phan ◽  
Xiaolin Wang ◽  
Joshua Jonghyun Park ◽  
...  
Keyword(s):  
Large Scale ◽  
Circulatory System ◽  
Vertical Direction ◽  
Microfluidic System ◽  
Vital Role ◽  
Microvascular Networks ◽  
Biological Studies ◽  
Wide Range ◽  
High Flexibility

AbstractThe vascular network of the circulatory system plays a vital role in maintaining homeostasis in the human body. In this paper, a novel modular microfluidic system with a vertical two-layered configuration is developed to generate large-scale perfused microvascular networks in vitro. The two-layer polydimethylsiloxane (PDMS) configuration allows the tissue chambers and medium channels not only to be designed and fabricated independently but also to be aligned and bonded accordingly. This method can produce a modular microfluidic system that has high flexibility and scalability to design an integrated platform with multiple perfused vascularized tissues with high densities. The medium channel was designed with a rhombic shape and fabricated to be semiclosed to form a capillary burst valve in the vertical direction, serving as the interface between the medium channels and tissue chambers. Angiogenesis and anastomosis at the vertical interface were successfully achieved by using different combinations of tissue chambers and medium channels. Various large-scale microvascular networks were generated and quantified in terms of vessel length and density. Minimal leakage of the perfused 70-kDa FITC-dextran confirmed the lumenization of the microvascular networks and the formation of tight vertical interconnections between the microvascular networks and medium channels in different structural layers. This platform enables the culturing of interconnected, large-scale perfused vascularized tissue networks with high density and scalability for a wide range of multiorgan-on-a-chip applications, including basic biological studies and drug screening.

scholarly journals Why ability point estimates can be pointless: a primer on using skill measures from large-scale assessments in secondary analyses

2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Clemens M. Lechner ◽  
Nivedita Bhaktha ◽  
Katharina Groskurth ◽  
Matthias Bluemke
Keyword(s):  
Measurement Error ◽  
Statistical Models ◽  
Test Scores ◽  
Large Scale ◽  
Equation Modeling ◽  
Model Parameters ◽  
Advantages And Disadvantages ◽  
Point Estimates ◽  
Secondary Analyses ◽  
Large Scale Assessments

AbstractMeasures of cognitive or socio-emotional skills from large-scale assessments surveys (LSAS) are often based on advanced statistical models and scoring techniques unfamiliar to applied researchers. Consequently, applied researchers working with data from LSAS may be uncertain about the assumptions and computational details of these statistical models and scoring techniques and about how to best incorporate the resulting skill measures in secondary analyses. The present paper is intended as a primer for applied researchers. After a brief introduction to the key properties of skill assessments, we give an overview over the three principal methods with which secondary analysts can incorporate skill measures from LSAS in their analyses: (1) as test scores (i.e., point estimates of individual ability), (2) through structural equation modeling (SEM), and (3) in the form of plausible values (PVs). We discuss the advantages and disadvantages of each method based on three criteria: fallibility (i.e., control for measurement error and unbiasedness), usability (i.e., ease of use in secondary analyses), and immutability (i.e., consistency of test scores, PVs, or measurement model parameters across different analyses and analysts). We show that although none of the methods are optimal under all criteria, methods that result in a single point estimate of each respondent’s ability (i.e., all types of “test scores”) are rarely optimal for research purposes. Instead, approaches that avoid or correct for measurement error—especially PV methodology—stand out as the method of choice. We conclude with practical recommendations for secondary analysts and data-producing organizations.

scholarly journals Power-to-Green Methanol via CO2 Hydrogenation—A Concept Study Including Oxyfuel Fluidized Bed Combustion of Biomass

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4638
Author(s):  
Simon Pratschner ◽  
Pavel Skopec ◽  
Jan Hrdlicka ◽  
Franz Winter
Keyword(s):  
Large Scale ◽  
Positive Impact ◽  
Renewable Energy Sources ◽  
Air Separation ◽  
Model Parameters ◽  
Processing Unit ◽  
Fluidized Bed Combustion ◽  
Separation Unit ◽  
Oxyfuel Combustion ◽  
Wind Park

A revolution of the global energy industry is without an alternative to solving the climate crisis. However, renewable energy sources typically show significant seasonal and daily fluctuations. This paper provides a system concept model of a decentralized power-to-green methanol plant consisting of a biomass heating plant with a thermal input of 20 MWth. (oxyfuel or air mode), a CO2 processing unit (DeOxo reactor or MEA absorption), an alkaline electrolyzer, a methanol synthesis unit, an air separation unit and a wind park. Applying oxyfuel combustion has the potential to directly utilize O2 generated by the electrolyzer, which was analyzed by varying critical model parameters. A major objective was to determine whether applying oxyfuel combustion has a positive impact on the plant’s power-to-liquid (PtL) efficiency rate. For cases utilizing more than 70% of CO2 generated by the combustion, the oxyfuel’s O2 demand is fully covered by the electrolyzer, making oxyfuel a viable option for large scale applications. Conventional air combustion is recommended for small wind parks and scenarios using surplus electricity. Maximum PtL efficiencies of ηPtL,Oxy = 51.91% and ηPtL,Air = 54.21% can be realized. Additionally, a case study for one year of operation has been conducted yielding an annual output of about 17,000 t/a methanol and 100 GWhth./a thermal energy for an input of 50,500 t/a woodchips and a wind park size of 36 MWp.

Turbulent convection driven by surface cooling in shallow water

2002 ◽  
Vol 464 ◽  
pp. 81-111 ◽  
Author(s):  
OLEG ZIKANOV ◽  
DONALD N. SLINN ◽  
MANHAR R. DHANAK
Keyword(s):  
Thermal Convection ◽  
Large Scale ◽  
Fourier Method ◽  
Vertical Direction ◽  
Finite Depth ◽  
Turbulent Convection ◽  
Bottom Surface ◽  
Computational Domain ◽  
Surface Cooling ◽  
Adverse Weather

We present the results of large-eddy simulations (LES) of turbulent thermal convection generated by surface cooling in a finite-depth stably stratified horizontal layer with an isothermal bottom surface. The flow is a simplified model of turbulent convection occurring in the warm shallow ocean during adverse weather events. Simulations are performed in a 6 × 6 × 1 aspect ratio computational domain using the pseudo-spectral Fourier method in the horizontal plane and finite-difference discretization on a high-resolution clustered grid in the vertical direction. A moderate value of the Reynolds number and two different values of the Richardson number corresponding to a weak initial stratification are considered. A version of the dynamic model is applied as a subgrid-scale (SGS) closure. Its performance is evaluated based on comparison with the results of direct numerical simulations (DNS) and simulations using the Smagorinsky model. Comprehensive study of the spatial structure and statistical properties of the developed turbulent state shows some similarity to Rayleigh–Bénard convection and other types of turbulent thermal convection in horizontal layers, but also reveals distinctive features such as the dominance of a large-scale pattern of descending plumes and strong turbulent fluctuations near the surface.

Coupled Thermo-Hydro-Geochemical Models of Engineered Barrier Systems: The Febex Project

2000 ◽  
Vol 663 ◽  
Author(s):  
J. Samper ◽  
R. Juncosa ◽  
V. Navarro ◽  
J. Delgado ◽  
L. Montenegro ◽  
...  
Keyword(s):  
Large Scale ◽  
Reference Model ◽  
Numerical Models ◽  
Full Scale ◽  
Small Scale ◽  
Model Parameters ◽  
In Situ Test ◽  
Wide Range ◽  
Engineered Barrier

ABSTRACTFEBEX (Full-scale Engineered Barrier EXperiment) is a demonstration and research project dealing with the bentonite engineered barrier designed for sealing and containment of waste in a high level radioactive waste repository (HLWR). It includes two main experiments: an situ full-scale test performed at Grimsel (GTS) and a mock-up test operating since February 1997 at CIEMAT facilities in Madrid (Spain) [1,2,3]. One of the objectives of FEBEX is the development and testing of conceptual and numerical models for the thermal, hydrodynamic, and geochemical (THG) processes expected to take place in engineered clay barriers. A significant improvement in coupled THG modeling of the clay barrier has been achieved both in terms of a better understanding of THG processes and more sophisticated THG computer codes. The ability of these models to reproduce the observed THG patterns in a wide range of THG conditions enhances the confidence in their prediction capabilities. Numerical THG models of heating and hydration experiments performed on small-scale lab cells provide excellent results for temperatures, water inflow and final water content in the cells [3]. Calculated concentrations at the end of the experiments reproduce most of the patterns of measured data. In general, the fit of concentrations of dissolved species is better than that of exchanged cations. These models were later used to simulate the evolution of the large-scale experiments (in situ and mock-up). Some thermo-hydrodynamic hypotheses and bentonite parameters were slightly revised during TH calibration of the mock-up test. The results of the reference model reproduce simultaneously the observed water inflows and bentonite temperatures and relative humidities. Although the model is highly sensitive to one-at-a-time variations in model parameters, the possibility of parameter combinations leading to similar fits cannot be precluded. The TH model of the “in situ” test is based on the same bentonite TH parameters and assumptions as for the “mock-up” test. Granite parameters were slightly modified during the calibration process in order to reproduce the observed thermal and hydrodynamic evolution. The reference model captures properly relative humidities and temperatures in the bentonite [3]. It also reproduces the observed spatial distribution of water pressures and temperatures in the granite. Once calibrated the TH aspects of the model, predictions of the THG evolution of both tests were performed. Data from the dismantling of the in situ test, which is planned for the summer of 2001, will provide a unique opportunity to test and validate current THG models of the EBS.

Model-Based Analysis of Transient Behavior of Large Scale CFB Boilers

2003 ◽  
Author(s):  
Ari Kettunen ◽  
Timo Hyppa¨nen ◽  
Ari-Pekka Kirkinen ◽  
Esa Maikkola
Keyword(s):  
Flow Rate ◽  
Large Scale ◽  
Air Flow ◽  
Model Parameters ◽  
Air Flow Rate ◽  
Process Data ◽  
Cfb Boiler ◽  
Flow Rates ◽  
Load Change ◽  
Secondary Air

The main objective of this study was to investigate the load change capability and effect of the individual control variables, such as fuel, primary air and secondary air flow rates, on the dynamics of large-scale CFB boilers. The dynamics of the CFB process were examined by dynamic process tests and by simulation studies. A multi-faceted set of transient process tests were performed at a commercial 235 MWe CFB unit. Fuel reactivity and interaction between gas flow rates, solid concentration profiles and heat transfer were studied by step changes of the following controllable variables: fuel feed rate, primary air flow rate, secondary air flow rate and primary to secondary air flow ratio. Load change performance was tested using two different types of tests: open and closed loop load changes. A tailored dynamic simulator for the CFB boiler was built and fine-tuned by determining the model parameters and by validating the models of each process component against measured process data of the transient test program. The know-how about the boiler dynamics obtained from the model analysis and the developed CFB simulator were utilized in designing the control systems of three new 262 MWe CFB units, which are now under construction. Further, the simulator was applied for the control system development and transient analysis of the supercritical OTU CFB boiler.

A Micromechanics Approach to Assess Ductile Crack Initiation in Damaged Pipelines

2003 ◽  
Author(s):  
Claudio Ruggieri ◽  
Fernando F. Santos ◽  
Mitsuru Ohata ◽  
Masao Toyoda
Keyword(s):  
Ductile Fracture ◽  
Large Scale ◽  
Cell Model ◽  
High Strength ◽  
Void Coalescence ◽  
Model Parameters ◽  
Ductile Crack ◽  
Cracking Behavior ◽  
Damage Criterion ◽  
Limited Applicability

This study explores the capabilities of a computational cell framework into a 3-D setting to model ductile fracture behavior in tensile specimens and damaged pipelines. The cell methodology provides a convenient approach for ductile crack extension suitable for large scale numerical analyses which includes a damage criterion and a microstructural length scale over which damage occurs. Laboratory testing of a high strength structural steel provides the experimental stress-strain data for round bar and circumferentially notched tensile specimens to calibrate the cell model parameters for the material. The present work applies the cell methodology using two damage criterion to describe ductile fracture in tensile specimens: (1) the Gurson-Tvergaard (GT) constitutive model for the softening of material and (2) the stress-modified, critical strain (SMCS) criterion for void coalescence. These damage criteria are then applied to predict ductile cracking for a pipe specimen tested under cycling bend loading. While the methodology still appears to have limited applicability to predict ductile cracking behavior in pipe specimens, the cell model predictions of the ductile response for the tensile specimens show good agreemeent with experimental measurements.

Modeling and Identification of Elastomeric Bearing Characteristics for Large-Scale Simulations

1998 ◽  
Vol 120 (1) ◽  
pp. 63-73 ◽  
Author(s):  
K. N. Morman ◽  
E. Nikolaidis ◽  
J. Rakowska ◽  
S. Seth
Keyword(s):  
Large Scale ◽  
Dynamic Stiffness ◽  
Testing Procedure ◽  
Nonlinear Dependence ◽  
Model Parameters ◽  
Elastomeric Bearing ◽  
Nonlinear Viscoelastic ◽  
Component Test ◽  
Differential Type ◽  
Stiffness And Damping

A constitutive equation of the differential type is introduced to model the nonlinear viscoelastic response behavior of elastomeric bearings in large-scale system simulations for vibration assessment and component loads prediction. The model accounts for the nonlinear dependence of dynamic stiffness and damping on vibration amplitude commonly observed in the behavior of bearings made of particle-reinforced elastomers. A testing procedure for the identification of the model parameters from bearing component test data is described. The experimental and analytical results for predicting the behavior of four (4) different car bushings are presented. In an example application, the model is incorporated in an ADAMS simulation to study the dynamic behavior of a car rear suspension.

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