We are proudly a Ukrainian website. Our country was attacked by Russian Armed Forces on Feb. 24, 2022.
You can support the Ukrainian Army by following the link: https://u24.gov.ua/.
Even the smallest donation is hugely appreciated!
Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili
Consulta la lista di attuali articoli, libri, tesi, atti di convegni e altre fonti scientifiche attinenti al tema "Approximate boundary conditions".
Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.
Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.
Roberts, A. J. "Boundary conditions for approximate differential equations". Journal of the Australian Mathematical Society. Series B. Applied Mathematics 34, n. 1 (luglio 1992): 54–80. http://dx.doi.org/10.1017/s0334270000007384.
AbstractA large number of mathematical models are expressed as differential equations. Such models are often derived through a slowly-varying approximation under the assumption that the domain of interest is arbitrarily large; however, typical solutions and the physical problem of interest possess finite domains. The issue is: what are the correct boundary conditions to be used at the edge of the domain for such model equations? Centre manifold theory [24] and its generalisations may be used to derive these sorts of approximations, and higher-order refinements, in an appealing and systematic fashion. Furthermore, the centre manifold approach permits the derivation of appropriate initial conditions and forcing for the models [25, 7]. Here I show how to derive asymptotically-correct boundary conditions for models which are based on the slowly-varying approximation. The dominant terms in the boundary conditions typically agree with those obtained through physical arguments. However, refined models of higher order require subtle corrections to the previously-deduced boundary conditions, and also require the provision of additional boundary conditions to form a complete model.
3
Wang, Lian Wen. "Approximate Controllability of Boundary Control Systems with Nonlinear Boundary Conditions". Applied Mechanics and Materials 538 (aprile 2014): 408–12. http://dx.doi.org/10.4028/www.scientific.net/amm.538.408.
The paper deals with the approximate controllability of a class of nonlinear delayed control systems in which the control is acted through the boundary of the region and the boundary conditions are nonlinear. The approximate controllability result is established provided the approximate controllability of the corresponding linear systems.
4
Codina, Ramon, e Joan Baiges. "Approximate imposition of boundary conditions in immersed boundary methods". International Journal for Numerical Methods in Engineering 80, n. 11 (19 giugno 2009): 1379–405. http://dx.doi.org/10.1002/nme.2662.
Senior, T. B. A. "Approximate boundary conditions for homogeneous dielectric bodies". Journal of Electromagnetic Waves and Applications 9, n. 10 (1 gennaio 1995): 1227–39. http://dx.doi.org/10.1163/156939395x00019.
Berdnyk, Serhii, Andrey Gomozov, Dmitriy Gretskih, Viktor Kartich e Mikhail Nesterenko. "Approximate boundary conditions for electromagnetic fields in electrodmagnetics". RADIOELECTRONIC AND COMPUTER SYSTEMS, n. 3 (4 ottobre 2022): 141–60. http://dx.doi.org/10.32620/reks.2022.3.11.
The results of an analytical review of literature sources on the use of approximate boundary conditions for electromagnetic fields of impedance type in solving boundary value problems of electromagnetism for more than 80 recent years are presented. During this period, the impedance approach was generalized to various electrodynamic problems, in which its use made it possible to significantly expand the limits of mathematical modeling, which adequately considers the physical properties of real boundary surfaces. More than eighty years have passed since the publication of approximate boundary conditions for electromagnetic fields. The meaning and value of these conditions lies in the fact that they allow solving diffraction problems about fields outside well-conducting bodies without considering the fields inside them, which greatly simplifies the solution. Since then, numerous publications have been devoted to the application of impedance boundary conditions, the main of which (according to the authors) are presented in this paper. Particular attention is paid to the characteristics of electrically thin impedance vibrators and film-type surface structures as a personal contribution of the authors to the theory of impedance boundary conditions in electromagnetism. The subject of research in this article is the analysis of the limits and conditions for the correct application of impedance boundary conditions. The goal is to systematize the results of using the concept of approximate impedance boundary conditions for electromagnetic fields in problems of electrodynamics based on an analytical review of literature sources. The following results were obtained. The types of metal-dielectric structures are presented, for which methods of theoretical determination of the values of surface impedances for film-type structures are currently known, which are the most promising for creating technological control elements on their basis in centimeter and millimeter wavelength devices. Conclusions. The materials of this paper do not pretend to be a complete reference book covering all the results and aspects of the development of the concept of approximate impedance type boundary conditions in problems of electromagnetism over the past decades. Simultaneously, the authors hope that the information presented in this paper will be useful to specialists in the field of theoretical and applied electrodynamics, as well as graduate students, young scientists and students who are just mastering radiophysics and radio engineering specialties.
7
Puska, P. P., S. A. Tretyakov e A. H. Sihvola. "Approximate impedance boundary conditions for isotropic multilayered media". IEE Proceedings - Microwaves, Antennas and Propagation 146, n. 2 (1999): 163. http://dx.doi.org/10.1049/ip-map:19990561.
Borggaard, J., e T. Iliescu. "Approximate deconvolution boundary conditions for large eddy simulation". Applied Mathematics Letters 19, n. 8 (agosto 2006): 735–40. http://dx.doi.org/10.1016/j.aml.2005.08.022.
Lill, Georg. "Exact and approximate boundary conditions at artificial boundaries". Mathematical Methods in the Applied Sciences 16, n. 10 (ottobre 1993): 691–705. http://dx.doi.org/10.1002/mma.1670161003.
Huddleston, P. L. "Scattering by finite, open cylinders using approximate boundary conditions". IEEE Transactions on Antennas and Propagation 37, n. 2 (1989): 253–57. http://dx.doi.org/10.1109/8.18715.
Nous avons traité le cas de l'équation scalaire de Helmholtz. Nous allons tenter de traiter le cas des équations de Maxwell. On s'intéressera aux cas des méta-matériaux. Dans un premier cas la permittivité est négative dans la couche mince et dans le deuxième cas la perméabilité est en (1/delta)^2 We have dealt with the case of the scalar Helmholtz equation. We will try to handle the case of Maxwell's equation. We also will focus on the case of meta-materials. In a first case the permittivity is negative in the thin layer and in the second case is the permeability (1/delta) ^ 2
2
See, Chan H. "Computation of electromagnetic fields in assemblages of biological cells using a modified finite difference time domain scheme. Computational electromagnetic methods using quasi-static approximate version of FDTD, modified Berenger absorbing boundary and Floquet periodic boundary conditions to investigate the phenomena in the interaction between EM fields and biological systems". Thesis, University of Bradford, 2007. http://hdl.handle.net/10454/4762.
yes There is an increasing need for accurate models describing the electrical behaviour of individual biological cells exposed to electromagnetic fields. In this area of solving linear problem, the most frequently used technique for computing the EM field is the Finite-Difference Time-Domain (FDTD) method. When modelling objects that are small compared with the wavelength, for example biological cells at radio frequencies, the standard Finite-Difference Time-Domain (FDTD) method requires extremely small time-step sizes, which may lead to excessive computation times. The problem can be overcome by implementing a quasi-static approximate version of FDTD, based on transferring the working frequency to a higher frequency and scaling back to the frequency of interest after the field has been computed.
An approach to modeling and analysis of biological cells, incorporating the Hodgkin and Huxley membrane model, is presented here. Since the external medium of the biological cell is lossy material, a modified Berenger absorbing boundary condition is used to truncate the computation grid. Linear assemblages of cells are investigated and then Floquet periodic boundary conditions are imposed to imitate the effect of periodic replication of the assemblages. Thus, the analysis of a large structure of cells is made more computationally efficient than the modeling of the entire structure. The total fields of the simulated structures are shown to give reasonable and stable results at 900MHz, 1800MHz and 2450MHz. This method will facilitate deeper investigation of the phenomena in the interaction between EM fields and biological systems.
Moreover, the nonlinear response of biological cell exposed to a 0.9GHz signal was discussed on observing the second harmonic at 1.8GHz. In this, an electrical circuit model has been proposed to calibrate the performance of nonlinear RF energy conversion inside a high quality factor resonant cavity with known nonlinear device. Meanwhile, the first and second harmonic responses of the cavity due to the loading of the cavity with the lossy material will also be demonstrated. The results from proposed mathematical model, give good indication of the input power required to detect the weakly effects of the second harmonic signal prior to perform the measurement. Hence, this proposed mathematical model will assist to determine how sensitivity of the second harmonic signal can be detected by placing the required specific input power.
3
See, Chan Hwang. "Computation of electromagnetic fields in assemblages of biological cells using a modified finite difference time domain scheme : computational electromagnetic methods using quasi-static approximate version of FDTD, modified Berenger absorbing boundary and Floquet periodic boundary conditions to investigate the phenomena in the interaction between EM fields and biological systems". Thesis, University of Bradford, 2007. http://hdl.handle.net/10454/4762.
There is an increasing need for accurate models describing the electrical behaviour of individual biological cells exposed to electromagnetic fields. In this area of solving linear problem, the most frequently used technique for computing the EM field is the Finite-Difference Time-Domain (FDTD) method. When modelling objects that are small compared with the wavelength, for example biological cells at radio frequencies, the standard Finite-Difference Time-Domain (FDTD) method requires extremely small time-step sizes, which may lead to excessive computation times. The problem can be overcome by implementing a quasi-static approximate version of FDTD, based on transferring the working frequency to a higher frequency and scaling back to the frequency of interest after the field has been computed. An approach to modeling and analysis of biological cells, incorporating the Hodgkin and Huxley membrane model, is presented here. Since the external medium of the biological cell is lossy material, a modified Berenger absorbing boundary condition is used to truncate the computation grid. Linear assemblages of cells are investigated and then Floquet periodic boundary conditions are imposed to imitate the effect of periodic replication of the assemblages. Thus, the analysis of a large structure of cells is made more computationally efficient than the modeling of the entire structure. The total fields of the simulated structures are shown to give reasonable and stable results at 900MHz, 1800MHz and 2450MHz. This method will facilitate deeper investigation of the phenomena in the interaction between EM fields and biological systems. Moreover, the nonlinear response of biological cell exposed to a 0.9GHz signal was discussed on observing the second harmonic at 1.8GHz. In this, an electrical circuit model has been proposed to calibrate the performance of nonlinear RF energy conversion inside a high quality factor resonant cavity with known nonlinear device. Meanwhile, the first and second harmonic responses of the cavity due to the loading of the cavity with the lossy material will also be demonstrated. The results from proposed mathematical model, give good indication of the input power required to detect the weakly effects of the second harmonic signal prior to perform the measurement. Hence, this proposed mathematical model will assist to determine how sensitivity of the second harmonic signal can be detected by placing the required specific input power.
4
Bertrand, Fleurianne [Verfasser]. "Approximated flux boundary conditions for Raviart-Thomas finite elements on domains with curved boundaries and applications to first-order system least squares / Fleurianne Bertrand". Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2014. http://d-nb.info/1063982103/34.
M, Hafez M., Gottlieb David e Langley Research Center, a cura di. Stability analysis of intermediate boundary conditions in approximate factorization schemes. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1986.
M, Hafez M., Gottlieb David e Langley Research Center, a cura di. Stability analysis of intermediate boundary conditions in approximate factorization schemes. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1986.
LeVeque, Randall J. Intermediate boundary conditions for LOD, ADI and approximate factorization methods. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1985.
Syed, Hasnain H. Electromagnetic scattering by coated convex surfaces and wedges simulated by approximate boundary conditions. Ann Arbor, Mich: University of Michigan, Radiation Laboratory, Dept. of Electrical Engineering and Computer Science, 1992.
Senior, T. B. A., e John L. Volakis. Approximate Boundary Conditions in Electromagnetics (Ieee Electromagnetic Waves Series). Institution of Electrical Engineers, 1995.
Thenumerical solution of ordinary differential equations (ODEs)with boundary conditions is studied here. Functions are approximated by polynomials in a Chebychev basis. Sections then cover spectral discretization, sampling, interpolation, differentiation, integration, and the basic ODE. Following Trefethen et al., differential operators are approximated as rectangular matrices. Boundary conditions add additional rows that turn them into square matrices. These can then be diagonalized using standard linear algebra methods. After studying various simple model problems, this method is applied to the Orr–Sommerfeld equation, deriving results originally due to Orszag. The difficulties of pushing spectral methods to higher dimensions are outlined.
8
Wang, Bin. Intraseasonal Modulation of the Indian Summer Monsoon. Oxford University Press, 2018. http://dx.doi.org/10.1093/acrefore/9780190228620.013.616.
The strongest Indian summer monsoon (ISM) on the planet features prolonged clustered spells of wet and dry conditions often lasting for two to three weeks, known as active and break monsoons. The active and break monsoons are attributed to a quasi-periodic intraseasonal oscillation (ISO), which is an extremely important form of the ISM variability bridging weather and climate variation. The ISO over India is part of the ISO in global tropics. The latter is one of the most important meteorological phenomena discovered during the 20th century (Madden & Julian, 1971, 1972). The extreme dry and wet events are regulated by the boreal summer ISO (BSISO). The BSISO over Indian monsoon region consists of northward propagating 30–60 day and westward propagating 10–20 day modes. The “clustering” of synoptic activity was separately modulated by both the 30–60 day and 10–20 day BSISO modes in approximately equal amounts. The clustering is particularly strong when the enhancement effect from both modes acts in concert. The northward propagation of BSISO is primarily originated from the easterly vertical shear (increasing easterly winds with height) of the monsoon flows, which by interacting with the BSISO convective system can generate boundary layer convergence to the north of the convective system that promotes its northward movement. The BSISO-ocean interaction through wind-evaporation feedback and cloud-radiation feedback can also contribute to the northward propagation of BSISO from the equator. The 10–20 day oscillation is primarily produced by convectively coupled Rossby waves modified by the monsoon mean flows. Using coupled general circulation models (GCMs) for ISO prediction is an important advance in subseasonal forecasts. The major modes of ISO over Indian monsoon region are potentially predictable up to 40–45 days as estimated by multiple GCM ensemble hindcast experiments. The current dynamical models’ prediction skills for the large initial amplitude cases are approximately 20–25 days, but the prediction of developing BSISO disturbance is much more difficult than the prediction of the mature BSISO disturbances. This article provides a synthesis of our current knowledge on the observed spatial and temporal structure of the ISO over India and the important physical processes through which the BSISO regulates the ISM active-break cycles and severe weather events. Our present capability and shortcomings in simulating and predicting the monsoon ISO and outstanding issues are also discussed.
Capitoli di libri sul tema "Approximate boundary conditions":
1
Senior, Thomas B. A. "Derivation and Application of Approximate Boundary Conditions". In Directions in Electromagnetic Wave Modeling, 477–83. Boston, MA: Springer US, 1991. http://dx.doi.org/10.1007/978-1-4899-3677-6_48.
Hoffmann, Guy, e Carlo Benocci. "Approximate Wall Boundary Conditions for Large Eddy Simulations". In Fluid Mechanics and Its Applications, 222–28. Dordrecht: Springer Netherlands, 1995. http://dx.doi.org/10.1007/978-94-011-0457-9_40.
Avalos, George, e Irena Lasiecka. "Exact-Approximate Boundary Controllability of Thermoelastic Systems under Free Boundary Conditions". In Control of Distributed Parameter and Stochastic Systems, 3–11. Boston, MA: Springer US, 1999. http://dx.doi.org/10.1007/978-0-387-35359-3_1.
Zhu, Biao, e Zhide Qiao. "Calculation of Wing Flutter Using Euler Equations with Approximate Boundary Conditions". In Computational Fluid Dynamics 2008, 107–12. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-01273-0_11.
Szilard, L., A. M. Weinberg, E. P. Wigner e R. F. Christy. "Approximate Boundary Conditions for Diffusion Equation at Interface Between Two Media". In Nuclear Energy, 509–12. Berlin, Heidelberg: Springer Berlin Heidelberg, 1992. http://dx.doi.org/10.1007/978-3-642-77425-6_34.
Gupta, Nishi, e Md Maqbul. "Approximate Solutions to Pseudo-Parabolic Equation with Initial and Boundary Conditions". In Nonlinear Dynamics and Applications, 925–34. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-99792-2_78.
Kapustyan, Volodymyr O., e Ivan O. Pyshnograiev. "Approximate Optimal Control for Parabolic–Hyperbolic Equations with Nonlocal Boundary Conditions and General Quadratic Quality Criterion". In Advances in Dynamical Systems and Control, 387–401. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-40673-2_21.
Barros, W. Q., A. P. Pires e Á. M. M. Peres. "Approximate Solution for One-Dimensional Compressible Two-Phase Immiscible Flow in Porous Media for Variable Boundary Conditions". In Integral Methods in Science and Engineering, 1–17. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-07171-3_1.
Hristov, Jordan. "On a Non-linear Diffusion Model of Wood Impregnation: Analysis, Approximate Solutions, and Experiments with Relaxing Boundary Conditions". In Advances in Mathematical Modelling, Applied Analysis and Computation, 25–53. Singapore: Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-19-0179-9_2.
Atti di convegni sul tema "Approximate boundary conditions":
1
Ripoll, J., e M. Nieto-Vesperinas. "Approximate Boundary Conditions for Index Mismatched Diffuse-Diffuse Interfaces". In Biomedical Topical Meeting. Washington, D.C.: OSA, 1999. http://dx.doi.org/10.1364/bio.1999.ama5.
Pan, G. D., e A. Abubakar. "Iterative Solution of 3D Helmholtz Equation with Approximate Boundary Conditions". In 75th EAGE Conference and Exhibition incorporating SPE EUROPEC 2013. Netherlands: EAGE Publications BV, 2013. http://dx.doi.org/10.3997/2214-4609.20130230.
Yuferev, S. "Application of approximate boundary conditions to electromagnetic transient scattering problems". In 3rd International Conference on Computation in Electromagnetics (CEM 96). IEE, 1996. http://dx.doi.org/10.1049/cp:19960157.
Pestov, Leonid, e Dmytro Strelnikov. "Approximate boundary controllability of wave equation with mixed boundary conditions and sound-speed reconstruction". In 2019 Days on Diffraction (DD). IEEE, 2019. http://dx.doi.org/10.1109/dd46733.2019.9016430.
Gao, Chao, Shijun Luo, Feng Liu e David Schuster. "Calculation of Airfoil Flutterby an Euler Method with Approximate Boundary Conditions". In 16th AIAA Computational Fluid Dynamics Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2003. http://dx.doi.org/10.2514/6.2003-3830.
Camberos, Jose´ A. "Implementing Approximate Boundary Conditions for Finite-Volume Time-Domain Electromagnetic Code". In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-39345.
In addition to the governing equations, a properly posed mathematical problem requires a statement of the solution bounds and boundary conditions. Numerical methods applied to solve the governing equations must also implement proper solution bounds and boundary conditions. In developing a finite-volume, time-domain solver for electromagnetic computations, the author implemented a variety of approximate boundary conditions formulated to mimic reflecting metallic boundaries and truncated solution-domain (outer) boundaries. These approximate boundary conditions are presented and discussed in context of selected results for predicting the radar-cross section of various shapes (with analytic solutions available for comparison).
7
Hoying, Donald, e Donald Hoying. "Approximate unsteady non-reflecting boundary conditions for the three-dimensional Euler equations". In 33rd Joint Propulsion Conference and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1997. http://dx.doi.org/10.2514/6.1997-2739.
The paper deals with a steady coupled dissipative layer, called Marangoni mixed convection boundary layer, which can be formed along the interface of two immiscible fluids, in surface driven flows. The mixed convection boundary layer is generated besides the Marangoni convection effects induced flow over the surface due to an imposed temperature gradient, there are also buoyancy effects due to gravity and external pressure gradient effects. We shall use a model proposed by Chamkha wherein the Marangoni coupling condition has been included into the boundary conditions at the interface. The similarity equations are first determined, and the approximate analytical solutions are obtained by an efficient transformation, asymptotic expansion and Pade´ approximant technique. The features of the flow and temperature fields as well as the interface velocity and heat transfer at the interface are discussed for some values of the governing parameters. The associated fluid mechanics was analyzed in detail.
9
Wiktor, Michal, Piotr Kowalczyk e Michal Mrozowski. "Approximate analytical boundary conditions for efficient finite difference frequency domain simulations in cylindrical coordinates". In 2006 International Conference on Microwaves, Radar & Wireless Communications. IEEE, 2006. http://dx.doi.org/10.1109/mikon.2006.4345280.
Venkataraman, P. "Approximate Analytical Solutions to Nonlinear Inverse Boundary Value Problems". In ASME 2016 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/detc2016-59306.
A nontraditional approach to the nonlinear inverse boundary value problem is illustrated using multiple examples of the Poisson equation. The solutions belong to a class of analytical solutions defined through Bézier functions. The solution represents a smooth function of high order over the domain. The same procedure can be applied to both the forward and the inverse problem. The solution is obtained as a local minimum of the residuals of the differential equations over many points in the domain. The Dirichlet and Neumann boundary conditions can be incorporated directly into the function definition. The primary disadvantage of the process is that it generates continuous solution even if continuity and smoothness are not expected for the solution. In this case they will generate an approximate analytical solution to either the forward or the inverse problem. On the other hand, the method does not need transformation or regularization, and is simple to apply. The solution is also good at damping the perturbations in measured data driving the inverse problem. In this paper we show that the method is quite robust for linear and nonlinear inverse boundary value problem. We compare the results with a solution to a nonlinear inverse boundary value problem obtained using a traditional approach. The application involves a mixture of symbolic and numeric computations and uses a standard unconstrained numerical optimizer.
Rapporti di organizzazioni sul tema "Approximate boundary conditions":
1
Babuska, Ivo, Victor Nistor e Nicolae Tarfulea. Approximate Dirichlet Boundary Conditions in the Generalized Finite Element Method (PREPRINT). Fort Belvoir, VA: Defense Technical Information Center, febbraio 2006. http://dx.doi.org/10.21236/ada478502.
Hailiang, Zhang. PR-469-173823-R02 In-Line Inspection and Evaluation of Pinholes in Oil and Gas Pipelines - Phase II. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), settembre 2020. http://dx.doi.org/10.55274/r0011780.
Pinhole leaks have been reported as a significant cause of oil and gas pipeline failures in recent years. From 2010 to 2015, at least 131 significant incidents involving oil and gas pipelines in the United States (101 and 30, respectively) were attributed to pinhole leaks. The 9th European Gas Pipeline Incident Data Group Report states that as of 2013, the five-year moving average failure frequency for pinholes was equal to an approximate annual rate of 0.105 failures per 1,000 kilometers of pipeline. Pinholes may result from normal pipeline corrosion during routine operations, such as micro-biologically induced corrosion, or can be created by third-party activities, such as illegal tapping. These small leaks have become a major risk for many pipeline companies. Pinhole leaks are more likely to lead to serious consequences than larger leaks because they are difficult to discover through normal monitoring and patrolling. An undetected pinhole leak can lead to significant soil and groundwater pollution over time. The research objective of this phase is to improve the results based on the research of phase one. The major work of this phase are following. In response to the problems found in the pull test of phase one, a number of defects with different sizes have been designed, including pinhole, pitting and grooves, were added to further subdivide the detection boundary conditions. The NDT verification tool for pinhole defects was compared and selected, and the appropriate ultrasonic scanning system was selected as the NDT method for internal pinhole verification. According to the actual ILI report, two pinholes and three pittings were selected for dig verification, and the results were comprehensively compared and analyzed with the pull test.
3
Chien, Stanley, Yaobin Chen, Lauren Christopher, Mei Qiu e Zhengming Ding. Road Condition Detection and Classification from Existing CCTV Feed. Purdue University, 2022. http://dx.doi.org/10.5703/1288284317364.
The Indiana Department of Transportation (INDOT) has approximately 500 digital cameras along highways in populated areas of Indiana. These cameras are used to monitor traffic conditions around the clock, all year round. Currently, the videos from these cameras are observed one-by-one by human operators looking for traffic conditions and incidents. The main objective of this research was to develop an automatic, real-time system to monitor traffic conditions and detect incidents automatically. The Transportation and Autonomous Systems Institute (TASI) of the Purdue School of Engineering and Technology at Indiana University-Purdue University Indianapolis (IUPUI) and the Traffic Management Center of INDOT developed a system that monitors the traffic conditions based on the INDOT CCTV video feeds. The proposed system performs traffic flow estimation, incident detection, and classification of vehicles involved in an incident. The research team designed the system, including the hardware and software components added to the existing INDOT CCTV system; the relationship between the added system and the currently existing INDOT system; the database structure for traffic data extracted from the videos; and a user-friendly, web-based server for showing the incident locations automatically. The specific work in this project includes vehicle-detection, road boundary detection, lane detection, vehicle count over time, flow-rate detection, traffic condition detection, database development, web-based graphical user interface (GUI), and a hardware specification study. The preliminary prototype of some system components has been implemented in the Development of Automated Incident Detection System Using Existing ATMS CCT (SPR-4305).
4
Bajwa, Abdullah, Tim Kroeger e Timothy Jacobs. PR-457-17201-R04 Residual Gas Fraction Estimation Based on Measured Engine Parameters - Phase IV. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), settembre 2021. http://dx.doi.org/10.55274/r0012176.
Based on experimental characterization of the scavenging behavior of a cross-scavenged, piston-aspirated, two-stroke, natural gas engine in phase III of the current project, a computationally inexpensive simple scavenging model was improved in this phase. Experimental results using fast nondispersive infrared (NDIR) CO2 measurements from the cylinder and the exhaust, as well as experiments using unburned fuel pre-mixed in the scavenging chamber as a tracer for short-circuiting during scavenging, were used in this phase to validate the improved model. The model represents the fundamental phenomenological characteristics revealed by those experiments. The experiments and literature show that scavenging takes place by the following phenomena: blowdown, displacement of residuals by incoming air, mixing of residuals and air, and short-circuiting of fresh air. To reflect this, the improved hybrid model features the following: isentropic blowdown, non-isothermal perfect displacement, non-isothermal perfect mixing, and a concurrent direct short-circuiting of air (unmixed with residuals). The validated improved hybrid model rectified the primary shortcoming of the phase III model. By adding the discrete short-circuiting zone, trapped mass could be modeled at both medium and high crankshaft speeds, whereas the phase III model could not capture the full scope of scavenging inefficiencies at medium speed using its perfect mixing stage alone. Furthermore, using the hybrid model to predict NOx using an exponential NO and shy;x-TER curve fit revealed that the improved phase IV hybrid model predicts NOx approximately as well as the experimentally-calculated TER from the phase III experiments. Additionally, GT-Power, a 1D fluid dynamics and engine simulation software, was used to identify whether hybrid model tuning could be aided by relatively inexpensive 1D simulation rather than CFD or fast NDIR experiments. Using three-pressure analysis (with in-cylinder, exhaust, and scavenging chamber pressures as boundary conditions) and scavenging profiles derived from the hybrid model itself, GT-Power was shown to be a plausible tool for scavenging model tuning.
