Simple Numerical Simulation Model Research Articles

Bidirectional and nested model for numerical simulation and machine learning: a case study of long-term settlement prediction of tunnel

Numerical simulation and machine learning are commonly adopted research methods in engineering. This paper proposes a bidirectional and nested model for numerical simulation and machine learning (BNNM). This model permits numerical simulation methods and machine learning methods to participate in each other’s calculation process. It helps overcome the obstruction of unclear mechanisms and inaccurate parameters in numerical simulation methods, and avoid overfitting problem caused by too many features in machine learning methods. Moreover, BNNM frees machine learning methods from the dependence on a specific set of labels. The BNNM helps train machine learning models using obtainable labels, and output results that cannot be easily obtained using field, experiment, and numerical simulations. To illustrate its construction method and performance, a representative BNNM model is constructed using BPNN, in addition to a simple numerical simulation model. This model predicts the long-term settlement of shield tunnel. The results show that the representative model effectively reduces the modelling difficulty associated with numerical simulation and improves prediction accuracy of BPNN model. The model also derives long-term constitutive models of various soils with only the tunnel settlement data set. Although a simplified constitutive model was used, the main advantages of the BNNM model have been highlighted.

Cluster-based learning and evolution algorithm for optimization

In this work, we present a cluster-based learning and evolution optimizer (CLEO) for solving optimization problems. CLEO is a metaheuristic algorithm that uses cluster-based manipulation of the problem space during the exploration phase, followed by fine-tuning solutions in the exploitation phase using updated knowledge of the problem space. We propose two approaches based on this new algorithm: one using only Latin hypercube sampling (LHS) and the other using LHS in combination with reservoir engineering insights. In addition to ensuring realistic simulation scenarios, we employed intuitive engineering insights to reveal how empirical knowledge enhances efficiency. Also, we propose simulating the partial life instead of the complete lifespan in the second approach. Technical results obtained at the end of this period are processed and used to find the optimized field development plan (FDP). We conducted both deterministic and probabilistic studies to assess the performance of the proposed approaches for various decision variables, both numerous and restricted. We validated the algorithm by optimizing the FDP for a simple numerical simulation model and a giant field-scale model, and compared our approaches to four well-established optimizers (particle swarm optimization (PSO), differential evolution (DE), designed exploration controlled evolution (DECE), and iterative discrete Latin hypercube sampling method (IDLHC)) in terms of simulation time and objective function results. Overall, the comparison demonstrates the advantages of the newly proposed algorithm. The results indicate that our first approach performs as well as any well-established optimizer, notably when working with large scale optimization problems. The second approach has slightly lower objective function results than the first one, but it is the most efficient among the compared algorithms, as the best FDP can be obtained by covering as little as 40% of the field's life. This attribute makes it an excellent alternative for developing oil and gas fields, which are fraught with uncertainty and errors in time-consuming simulation models. As a feasibility study on a complex and expensive compositional model, using second approach resulted in a 75% increase in efficiency while saving 120 days.

A Simple Numerical Simulation Model for Liner Friction Welding by Particle Method

A Simple Numerical Simulation Model for Liner Friction Welding by Particle Method

Researches on calculation methods of aquifer influx for gas reservoirs with aquifer support

Abstract The existence of aquifers in gas reservoirs has important influences on the development of gas wells. Water will invade into gas reservoirs when formation pressure decreases during the production of a gas well and then change the well production characteristics severely. It is very important to research the aquifer invasion mechanisms and evaluate the aquifer influx for good knowing and exploring the gas reservoir. In this paper, we have conducted three methods to research the aquifer influx characteristics by evaluating the value of aquifer influx and aquifer influx rate that vary with the production time. Three methods are the Blasingame method, the FMB (Flowing Material Balance) method and the MBE (Material Balance Equation) method. Based on the Blasingame conventional type-curves, the normalized well production data of a gas well influenced by aquifers can be divided into three influx periods: no-aquifer, early-aquifer and middle-late-aquifer influx period. The no-aquifer influx period production data are used to determine well initial gas in place and as a base, and the early-aquifer influx period production data are used to obtain aquifer influx and aquifer influx rate quantitatively. The novel three methods presented can elucidate the aquifer influx characteristics clearly and determine aquifer influx rate quantitatively just using well dynamic production data based on the Fetkovich model. Meanwhile, a simple numerical simulation model was built to verify the three methods, which shows that these three methods are reliable and really have strong practicability in developing gas field reservoirs with aquifer support.

Observing propagating jet meanders in a numerical simulation of large-scale oceanic and atmospheric dynamics

Theoretical physicists investigate wavenumber-frequency spectra of various flow regimes using a simple numerical simulation model.

Semi-active structural vibration control of base-isolated buildings using magnetorheological dampers

In recent years, several solutions for structural vibration control of buildings have been proposed. In particular, the combination of base-isolated structures with complementary variable damping devices has been successful in reducing the base isolator displacements without increasing the building superstructure response when subjected to earthquake loads. In this paper, a magnetorheological device is installed on a 2-DOF mechanical model mounted on an experimental uniaxial shaking table. A simple numerical simulation model is derived for the experimental setup and it represents a typical base-isolated structure with a semi-active vibration controller. The control law combines a force tracking integral action with a clipped on–off adaptation rule that changes the magnetorheological damping in real time. The effectiveness of the proposed solution is demonstrated for both earthquake-like and real earthquake input ground motions. A comparison between the numerical and the experimental results validates the numerical simulations and it gives confidence in using this model for validation and evaluation of other semi-active control solutions based on magnetorheological dampers.

Climate Policy with Technology Transfers and Permit Trading

In this paper, we analyze technology transfers (TT) and tradable emission rights, which are core issues of the ongoing climate negotiations. Subsidizing TT leads to the adoption of better abatement technologies in the South, thereby reducing the international permit price. This is beneficial for the North as long as it is a permit buyer; hence it chooses to subsidize TT. By contrast, the permit selling South suffers from the lower permit price and its welfare usually deteriorates, despite receiving subsidies. We also consider how TT affects countries’ non-cooperative choices of permit endowments and find that it tends to reduce overall emissions. Finally, a simple numerical simulation model illustrates the results and explores some further comparative statics.

The Focused Beam Forming with a Monolithic 2D Phased Array

A new type of the monolithic acoustic scanner based on a near-surface quasicomposite two-dimensional array, implemented in the solid elastic substrate was proposed. It provides a simple means of focusing and scanning a beam of acoustic waves, radiated into the depth of the elastic solid substrate. A chirped surface acoustic wave is converted into a focused bulk wave by scattering from an array composed of a 2D periodic system of regions with varying material parameters, located at the surface of a surface acoustic waves substrate. In the paper, a simple numerical simulation model is presented to analyse the in∞uences of the dynamical and geometrical parameters of the surface structure, as well as the in∞uences of incident surface acoustic waves signal proflle on the focal distribution.

Biquadratic Exchange Coupling in Epitaxial Co$_{2}$MnSi/Cr/Fe Trilayers

Interlayer exchange coupling (IEC) behavior in epitaxial Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> MnSi (20 nm)/Cr/Fe (7 nm) trilayers has been investigated against Cr spacer thickness (t <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Cr</sub> = 0.3-6.3 nm). High-quality trilayer samples have grown on a Cr (5 nm)/Au (30 nm)/Cr (15 nm) buffer layer on a MgO substrate by ultrahigh vacuum (UHV) compatible dc sputtering method. A simple numerical simulation model has been used to explain magnetization process, which shows good agreement with the experimental M-H curves. The values of bilinear and biquadratic coupling energy (J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> and J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) and the cubic anisotropy energy of Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> MnSi and Fe (K <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CMS</sub> and K <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Fe</sub> ) have been determined uniquely from the simulations. As a result, we have found a dominating contribution of biquadratic (90deg) coupling and absence of bilinear (180deg) coupling in all the samples with nonferromagnetic coupling. It has also been found that, the energetical competition between 90deg coupling energy and anisotropy energy largely affects the magnetization process due to different easy directions of bottom Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> MnSi (110) and Fe (100).

A simple numerical simulation model for space charge field formation in photorefractive materials

A simple numerical simulation model of space charge field formation in photorefractive materials is presented. The model considers microscopic statistical events occurring during writing of a phase grating by a light intensity pattern in weakly photoconducting materials. The model properly describes many characteristics of photorefraction phenomena found in the literature.

Contractionary devaluation with black markets for foreign exchange

Analyses of the possible contractionary effects of exchange rate devaluation typically assume the foreign exchange market to be unified, thereby ignoring the large fraction of transactions taking place in the black markets for foreign exchange that exist in many developing countries. This paper explores how the existence of these black markets may alter the impact of an official devaluation on aggregate output. It is argued that devaluation will be followed by less immediate contraction in a black market economy than in a unified market economy, both because the black market exchange rate will depreciate by less than the official rate, and because many of the devaluation's contractionary effects will occur in anticipation of the official devaluation itself. These propositions are tested using a simple numerical simulation model.

Effect of magnetic particle chain formation on the entropy change in superparamagnetic nanocomposite systems

Abstract A simple numerical simulation model was developed to study the effect of magnetic particle-chain formation on the entropy change of a superparamagnetic nanocomposite system comprised of magnetic and nonmagnetic particles. The random deposition of these particles results in the formation of chains that have the magnetic particles in contact. The number and length distributions of these chains depend on the relationship between the number of magnetic particles and the number of nonmagnetic particles within the composite. These chains increase the equivalent size of the particles resulting in a net decrease in the entropy change of the system. This decrease in the entropy change also depends on the dilution of the composite by nonmagnetic particles. For large particles, dilution increases the entropy change; whereas for small particles, dilution reduces the entropy change. Results from this simple model provide further insight into existing theories on how to enhance the magnetocaloric effect in superparamagnetic nanocomposite systems.

Contractionary Devaluation with Black Markets for Foreign Exchange

Analyses of the possible contractionary effects of exchange rate devaluation typically assume the foreign exchange market to be unified, thereby ignoring the large fraction of transactions taking place in the black market for foreign exchange that exist in many developing countries. This paper explores how the existence of these black markets may alter the impact of an official devaluation on aggregate output. It is argued that devaluations will be followed by less immediate contraction in a black­market economy than in a unified-market economy, both because the black market exchange rate will depreciate by less than the official rate, and because many of the devaluation's contractionary effects will occur in anticipation of the official devaluation itself. These propositions are tested using a simple numerical simulation model.

A numerical simulation of the effects of oceanic finestructure on acoustic transmission

A simple numerical simulation model is presented which includes the effects of oceanic finestructure together with previously developed theoretical treatments of the effects of internal waves on acoustic transmission. The wave equation solution to particular layer geometries developed by Brekhovskikh [Waves in Layered Media (Academic, New York, 1960)] is combined with the theoretical model of acoustic scattering based on internal waves developed by Desaubies [J. Acoust. Soc. Am. 64, 1460–1469 (1978)]. In this treatment it is assumed that a single finestructure layer is passively advected by internal waves. The layer modulates the effects of internal waves. Experiments carried out at Cobb Seamount over a fixed, horizontal, wholly refracted path indicate that the power spectrum of the phase fluctuations is fit almost exactly by models based on internal waves only, while the power spectrum of the log amplitude fluctuations is not. In the present treatment the predictions of the phase fluctuations remain unaffected by the presence of finestructure, and the predicted power spectrum of the log amplitude is in considerably better agreement with observation.

A numerical simulation of the effects of oceanic finestructure on acoustic transmission

A simple numerical simulation model is presented which includes the effects of oceanic finestructure together with previously developed theoretical treatments of the effects of internal waves on acoustic transmission. The wave equation solution to particular layer geometries developed by Brekhovskikh [Waves in Layered Media (Academic, New York, 1960)] is combined with the theoretical model of acoustic scattering based on internal waves developed by Desaubies [J. Acoust. Soc. Am. 64, 1460–1469 (1978)]. In this treatment it is assumed that a single finestructure layer is passively advected by internal waves. The layer modulates the effects of internal waves. Experiments carried out at Cobb Seamount over a fixed, horizontal, wholly refracted path indicate that the power spectrum of the phase fluctuations is fit almost exactly by models based on internal waves only, while the power spectrum of the log amplitude fluctuations is not. In the present treatment the predictions of the phase fluctuations remain unaf...