Editorial – Advanced modeling and simulation in engineering sciences

NOTE: The first page of text has been automatically extracted and included below in lieu of an abstract Attracting and Retaining Women in Computer Science and Engineering: Evaluating the Results Abstract Computer science and engineering communities have been exploring a variety of activities and techniques to attract and retain more students, especially women and minorities, to computer science and computer engineering degree programs1. This paper briefly describes the efforts and results of a plan for actively recruiting young women into undergraduate computer engineering and computer science programs hosted by the University of North Texas (UNT). It also describes a series of activities aimed at improving the retention rate of students already in our programs, particularly during the freshman year. Such recruitment and retention efforts are critical to the country’s efforts to increase the number of engineering professionals, and are a priority for the Computer Science and Engineering (CSE) Department at UNT. We initially designed a three-part plan to achieve our recruitment and retention goals: • Sponsorship of portable and mobile summer computer engineering robotics camps for middle and high-school women students, coordinating with the regional Girl Scouts councils and other organizations to help with the recruitment; • Creation of an Ambassador program using young women currently enrolled in the upper division of current computer science and computer engineering programs as a form of outreach to area high schools and junior colleges; and • Expansion of our successful undergraduate mentoring program by using the Ambassador cohort mentioned above as mentors for incoming freshman and first-year transfer women entering our programs. This paper will focus primarily on the summer camp program and present an analysis of the results we have seen to date after 2 years of camp activities. Results from student surveys and parent surveys will be presented. The paper concludes with recommended changes and improvements in the program, as well as a discussion of adaptations that would create programs suitable for implementation at other institutions as well as programs aimed at a different target population. The three phases previously enumerated each build upon currently accepted educational practices. The robotics summer camp in particular used problem-based learning approaches, similar to those described in The Power of Problem-Based Learning2. This study clearly demonstrates the significant benefits of teaching students how to think by using a problem-based approach. We also developed a mobile laboratory so that the summer camp can be held at several locations, thus broadening and expanding the reach of the camps to traditionally underserved populations and geographical regions. Similarly, both the ambassador and mentoring programs derive from research showing how the recruitment and retention of women in engineering- related fields can be increased by providing opportunities to develop student-to-student relationships3, 4.

This special section of the International Journal of Geomechanics contains selected papers that are based on the presentations at the GeoHunan International Conference: Challenges and Recent Advances in Pavement Technologies and Transportation Geotechnics, held in Changsha, Hunan, China, on August 3–6, 2009. The subject of geomechanics has come a long way in developing constitutive models for geomaterials, including nontraditional materials. Yet, there are complex geomechanics problems that do not have well-defined constitutive models and solutions. Recently, advanced modeling and numerical simulation techniques such as neural network, bound theorem, and centrifuge modeling have been employed to solve some of those geomechanics problems. Owing to the rapid expansion in the use of computer software, nonlinear numerical analysis or neural network modeling has become very popular among researchers and practicing engineers in recent years. Although theoretical models have been around for a long time, it has always been challenging to develop such models. Recently, small-scale centrifuge-based simulations have shown a promising capability of modeling prototype geostructures without a gravityinduced in situ stress field. This special section contains six full-length papers covering such advanced modeling and numerical simulations, different from traditional constitutive modeling, in geomechanics. The paper contributed by Xiang et al. discusses settlement prediction on a chimney foundation by a neural network. In their work, seven models with different input series were developed. The optimal model was determined by comparing the forecasting performance. Xiao et al. carried out numerical simulations of a single pile in expansive soil and extensively studied the load transfer mechanism and soil-pile interaction. Chen and Yu present a study on centrifuge modeling, in which staged construction on a reinforced lime-stabilized embankment was simulated by spinning the model at various g-levels. Centrifuge test results were used to verify and validate their numerical analysis. A comprehensive literature review on constitutive modeling of unsaturated soil is presented by Zhang and Li. Some limitations in the framework of the Barcelona Basic Model are discussed, and a new approach is proposed to overcome the limitations. Fu et al. investigated the compressive behavior of anchored rock masses through a series of physical model tests. The test results were compared with specimens without anchor bolts. It was concluded that the improvement attributable to vertical bolts is more effective. Zhao et al. employed an upper bound limit analysis to evaluate the ultimate pullout capacity of horizontal shallow plate anchors. Dilation and nonlinear behavior of soil was found to have profound effects on the ultimate pullout capacity.

Electrical impedance tomography (EIT) is a promising method to characterize important hydrological properties of soil, sediments, and rocks. The characterization is based on the analysis of the phase response of the complex electrical conductivity in a broad frequency range (i.e. mHz to kHz). However, it is challenging to measure the small phase response of low-polarizable soils and rocks in the higher frequency range up to 10 kHz. In order to achieve the required phase accuracy in the kHz frequency range, an optimized measurement system and advanced model-based processing methods have been developed. Recently, EIT measurements at sites with low electrical conductivity have shown a new dominating phase error related to capacitive leakage currents between cable shields and soil. In order to correct this phase error, we developed an advanced finite element model that considers both leakage currents and capacitive coupling between the soil and the cable shields in the reconstruction of the complex electrical conductivity distribution. This advanced model also takes into account potential measurement errors due to high electrode impedances. The use of this advanced model reduced the new dominating error for media with low electrical conductivity. It was also found that the amount of leakage current is an additional indicator for data quality that can be used for data filtering. After application of a novel data filter based on the leakage current and the use of the advanced modelling approach, the phase error of the measured transfer impedances above 100 Hz was significantly reduced by a factor of 6 or more at 10 kHz. In addition, physically implausible positive phase values were effectively eliminated. The new correction method now enables the reconstruction of the complex electrical conductivity for frequencies up to 10 kHz at field sites with a low electrical conductivity.

Combustion instability due to thermo-acoustic interactions in high-speed propulsion devices such as gas turbines and rocket engines result from pressure waves with very large amplitudes propagating back and forth in the combustion chamber. Exposure to the pressure fluctuations over a long period of time can lead to a cataclysmic failure of engines. The underlying physics governing the generation of the thermo-acoustic instability is a complex interaction among heat release, turbulence, and acoustic waves. Currently, it is very difficult to accurately predict the expected level of oscillations in a combustor. Hence development of strategies and engineering solutions to mitigate thermo-acoustic instability is an active area of research in both academia and industry. In this work, we carry out numerical modeling of thermo-acoustic instability in a self-excited, laboratory scale, model rocket combustor developed at Purdue University. Two different turbulent combustion models to account for turbulence-chemistry interactions are considered in this study, the flamelet model and the transported probability density function (PDF) method. <br>In the flamelet modeling approach, detailed chemical kinetics can be easily incorporated at a relatively low cost in comparison to other turbulent combustion models and it also accounts for turbulence-chemistry interactions. The flamelet model study is divided into two parts. In first part, we examine the effect of different numerical approaches for implementing the flamelet model. In advanced modeling and simulations of turbulent combustion, the accuracy of model predictions is affected by physical model errors as well as errors that arise from the numerical implementation of models in simulation codes. Here we are mainly concerned with the effect of numerical implementation on model predictions of turbulent combustion. Particularly, we employ the flamelet/progress variable (FPV) model and examine the effect of various numerical approaches for the flamelet table integration, with presumed shapes of PDF, on the FPV modeling results. Three different presumed-PDF table integration approaches are examined in detail by employing different numerical integration strategies. The effect of the different presumed-PDF table integration approaches is examined on predictions of two real flames, a laboratory-scale turbulent free jet flame, Sandia Flame D and the self-excited resonance model rocket combustor. Significant difference is observed in the predictions both of the flames. The results in this study further support the claims made in previous studies that it is imperative to preserve the laminar flamelet structure during integration while using the flamelet model to achieve better predictions in simulations. In the second part of the flamelet modeling study, computational investigations of the coupling between the transient flame dynamics such as the ignition delay and local extinction and the thermo-acoustic instability developed in a self-excited resonance combustor to gain deep insights into the mechanisms of thermo-acoustic instability. A modeling framework that employs different flamelet models (the steady flamelet model and the flamelet/progress variable approach) is developed to enable the examination of the effect of the transient flame dynamics caused by the strong coupling of the turbulent mixing and finite-rate chemical kinetics on the occurrence of thermo-acoustic instability. The models are validated by using the available experimental data for the pressure signal. Parametric studies are performed to examine the effect of the occurrence of the transient flame dynamics, the effect of artificial amplification of the Damkohler number, and the effect of neglecting mixture fraction fluctuations on the predictions of the thermo-acoustic instability. The parametric studies reveal that the occurrence of transient flame dynamics has a strong influence on the onset of the thermo-acoustic instability. Further analysis is then conducted to localize the effect of a particular flame dynamic event, the ignition delay, on the thermo-acoustic instability. The reverse effect of the occurrence of the thermo-acoustic instability on the transient flame dynamics in the combustor is also investigated by examining the temporal evolution of the local flame events in conjunction with the pressure wave propagation. The above observed two-way coupling between the transient flame dynamics (the ignition delay) and the thermo-acoustic instability provides a plausible mechanism of the self-excited and sustained thermo-acoustic instability observed in the combustor.<br>The second turbulent combustion model considered in this study is the transported PDF method. The transported PDF method is one of the most attractive models because it treats the highly-nonlinear chemical reaction source term without a closure requirement and it is a generalized model for a wide range of turbulent combustion problems.Traditionally, the transported PDF method has been used to model low-Mach number, incompressible flows where the pressure is assumed to be thermodynamically constant. Since there is significant pressure fluctuations in the model rocket combustor, the flow is highly compressible and it is necessary to account for this compressibility in the transported PDF method. In the past there has been very little work to model compressible reactive flows using the transported PDF and no effort has been made to model thermo-acoustic instability using the transported PDF method. There is a pressing need to further examine and develop the transported PDF method for compressible reactive flows to broaden our understanding of physical phenomenon like thermo-acoustic instability, interaction between combustion and strong shock and expansion waves, coupling between acoustic and heat release which are observed in high-speed turbulent combustion problems. To address this, a modeling framework for compressible turbulent reactive flows by the using the transported PDF method is developed. This framework is validated in a series of test cases ranging from pure mixing to a supersonic turbulent jet flame. The framework is then used to study the thermo-acoustic interactions in the self-excited model rocket combustor.

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Modular construction is the off-site fabrication and assembly of building components in a controlled factory environment, offering advantages in terms of time efficiency, quality control, and addressing labour shortages over traditional construction methods. While several studies have evaluated the seismic performance of steel modular buildings, limited studies have evaluated the seismic performance of composite modular buildings (CMBs) that incorporate composite elements, such as concrete-filled steel tubes (CFSTs). Moreover, the promising findings from steel modular buildings highlight the need to evaluate the seismic performance of CMBs, as this would facilitate the expansion of current design Standards to include modular construction. This study investigates the seismic performance of a 10-storey CMB with CFST columns. The methodology included developing a 3D finite element model in OpenSees software using advanced material models and modelling approaches to accurately simulate the nonlinear response. Modal analysis, nonlinear pushover analysis, and nonlinear time history analyses using a selected suite of ground motions were performed. Results indicated that Australian Standards underestimate the fundamental period, ductility, and overstrength of CMBs. The structure demonstrated robust performance, with generally low residual inter-storey drifts, suggesting minimal permanent deformation. The promising seismic performance of mid-rise CMBs with CFST columns in low-to-moderate seismicity suggests their potential safe application in high seismicity regions. • A novel joining method was used for composite modular buildings under earthquake. • Seismic performance of buildings is investigated using OpenSees software. • The joining method can be safely used for modular buildings under earthquake.

Computational Science and Engineering (CSE) software is typically developed using research funding where the primary focus is research and development of advanced algorithms and modeling capabilities. As a result, formal software engineering is seldom a primary goal. CSE software developers intend to write good software, but often lack the training, resources or time to adopt advanced formal methods and practices. In this paper, we present a list of practices identified from the Trilinos project that we believe most CSE software teams can adopt and from which they can benefit.

On soft terrain, such as deep snow, track sinkage often exceeds vehicle ground clearance and the vehicle belly comes into contact with the terrain surface. This paper describes the results of a detailed investigation into the effects of design features, particularly the combined effects of initial track tension (i.e., the tension in the track system when the vehicle is stationary on a level, hard surface) and vehicle belly attitude (nose-up or nose-down), on soft ground mobility of tracked vehicles. The investigation was carried out using the latest version of an advanced computer simulation model, known as NTVPM, developed under the auspices of Vehicle Systems Development Corporation. The results show that the initial track tension has a significant effect on soft ground mobility, particularly when track sinkage is greater than vehicle ground clearance. When the vehicle belly is in contact with terrain surface, its attitude also has a notable effect on vehicle performance at low initial track tensions. However, its effect on mobility decreases with the increase in initial track tension. It is demonstrated that NTVPM is a useful and effective tool for design and performance evaluation of tracked vehicles from a traction perspective.

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Big data to smart data in Alzheimer's disease: Real-world examples of advanced modeling and simulation

Accurate modelling of sheet metal forming can contribute significantly to reduction of lead time and development costs in manufacturing industries. The current way to improve the finite element model accuracy is to combine advanced constitutive material models and advanced tribological models. For model validation purposes the geometry of the forming tools needs to be updated and the most relevant parameters of the forming press needs to be incorporated. The addition of a simple and easier to control model test can offer additional information on difficult to characterize parameters of the industrial process. The industrial validation case presented in this paper demonstrates that the Tata Steel constitutive material model has similar prediction capability as the state of the art material model used at Volvo Cars for regular process development for automotive parts production. In both industrial and model tests the tribological system appears to affect significantly the overall model accuracy. The model tests suggests that further work is needed in order to improve the tribological model description at high contact pressure and high strain levels.

In the last decade, an increasing trend has been observed in the use of advanced anisotropic material models to improve the numerical predictions about sheet metal-forming processes. Among the actions following this trend, the use of non-associated flow rule (NAFR) models has been presented as an alternative to the classic associated flow rule (AFR) models. In this work, the influence of the flow rule in advanced anisotropic models has been analysed, following a systematic methodology. To evaluate both advantages and disadvantages of the flow rule, models with similar flexibility (i.e. with 8 and 16 parameters) have been compared by performing a finite element (FE) simulation of a cup-drawing process to study earing phenomena regarding accuracy, computational time and complexity. From the present study, it has been concluded that the main drivers on the final cup-drawing profile prediction are the model flexibility and the coefficient selection rather than the flow rule. Even though the NAFR formulation is complex when compared to the AFR regarding numerical implementation, this study shows that the total simulation time in a cup-drawing process while using explicit FE solvers is reduced in some cases, this one being strongly dependent on the material parameter definition.

The phrase “Publish or perish” is now becoming a harsh reality in every stage of the career in the daily lives of people working in academia. universities, institutions, and academic journals are now equally involved in this prevalent culture of publish or perish.If students, do not publish means they may have a hard time finding a job. If a new faculty, do not publish means not making progress on the track to tenure. If established researchers, don’t get published in a prestigious journal, it may result in a loss of research funding or their position with the university. If the university or institutions do not publish, they may Face budgetary pressures, fail to attract research funding, and one of the best ways to do that is to be published more and more in prestigious journals. In the case of journals, the increase in submissions from academic researchers under pressure to get published raises their operating costs to process them all if they change any article processing or publication fee. If there is no fee changed then it may be meeting the obligation to publish. Furthermore, the pressure to maintain prominence via Impact Scores and other measures of perceived rank generates increased pressure to publish ground-breaking research that will gather media attention and larger numbers of citations in the era when so many new journals are being published every year. In any case, it is a vicious cycle which has harsh consequences.

This chapter contains sections titled: Introduction The Euler–Bernoulli Beam Equation Euler–Bernoulli Beam Theory GWSh Reformulation Timoshenko Beam Theory Mechanical Vibrations of a Beam Fluid Mechanics, Potential Flow Electromagnetic Plane Wave Propagation Convection–Radiation Finned Cylinder Heat Transfer Chapter Summary Exercises Computer Labs References