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Synchrotron x-ray topography with a high-resolution setup using 11-28 reflection was carried out on 4H-SiC epilayers. Four different shapes of threading-edge dislocation according to Burgers vector direction were observed. The four types of threading-edge dislocation images were calculated by computer simulation, and the experimental results correlated well with the simulation results. The detailed topographic features generated by plural screw dislocations and basal plane dislocations were also investigated. [ABSTRACT FROM AUTHOR]

In this paper, a model of active control system with state-dependent actuation time delay is investigated. Galerkin projection scheme is used to obtain its low dimensional approximation system. State-dependency and effect on dynamics and performance of actuation delay in this active control system are considered. The following results are obtained. Firstly, a state-dependent actuation delay is proposed, which has never been reported in the previous works. It displays that actuation delay is state-dependent. Secondly, employing Galerkin projection scheme, low dimensional approximation system of this delayed active control system is obtained. At last, its stability and Hopf bifurcation are investigated by Routh-Hurwitz Criterion and Hopf bifurcation theory. Using software WinPP, numerical simulation is executed and supports the theoretical results in this paper. [ABSTRACT FROM AUTHOR]

This paper presents the numerical analysis of the transient performance of the latent heat thermal energy storage unit established on finite difference method. The storage unit consists of a shell and tube arrangement with phase change material (PCM) filled in the shell space and the heat transfer fluid (HTF) flowing in the inner tube. The heat exchange between the HTF, wall and PCM has been investigated by developing a 2-D fully implicit numerical model for the storage module and solving the complete module as a conjugate problem using enthalpy transforming method. A comparative investigation of the total melting time of the PCM has been performed based on natural convection in liquid PCM during the charging process. The novelty of this paper lies in the fact it includes convection in PCM and this investigation includes a detailed parametric study which can be used as a reference to design latent heat storage. The results indicate that natural convection accelerates the melting process by a significant amount of time. In order to optimize the design of the thermal storage unit, parametric study has been accompanied to analyze the influence of various HTF working conditions and geometric dimensions on the total melting time of the PCM. Another important feature considered in this work is the influence of the inner wall of the tube carrying the HTF on the entire melting time of the PCM. An error of around 7.2% is reported when inner wall of the tube is ignored in the analysis. [ABSTRACT FROM AUTHOR]

Based on CFD method, the numerical method for the manoeuvre simulation of trimaran and asymmetric twin hull by OpenFOAM was applied in this paper. The grid independency test was carried out, and the computed result of turn and zigzag manoeuvres was compared with the result of self-propulsion experiment to validate the numerical method. Then, the numerical method was applied to simulate the turn and zigzag manoeuvres of both an actual trimaran and an actual asymmetric twin hull. By the manoeuvre simulation in calm water with hull attitude fixed and free, the effect of hull attitude on the manoeuvre of trimaran and asymmetric twin hull with different layouts and Froude number was discussed, and the importance of hull attitude for the numerical simulation of turn and zigzag manoeuvres was illustrated. The result shows that, the numerical method in this paper is valid for the manoeuvre simulation of trimaran and asymmetric twin hull, and it makes sense to take the hull attitude into account for the manoeuvre simulation of trimaran and asymmetric twin hull. [ABSTRACT FROM AUTHOR]

Coronary arteries have high curvatures, and hence, flow through them causes disturbed flow patterns, resulting in stenosis and atherosclerosis. This in turn decreases the myocardial flow perfusion, causing myocardial ischemia and infarction. Therefore, in order to understand the mechanisms of these phenomena caused by high curvatures and branching of coronary arteries, we have conducted elaborate hemodynamic analysis for both (i) idealized coronary arteries with geometrical parameters representing realistic curvatures and stenosis and (ii) patient-specific coronary arteries with stenoses. Firstly, in idealized coronary arteries with approximated realistic arterial geometry representative of their curvedness and stenosis, we have computed the hemodynamic parameters of pressure drop, wall shear stress (WSS) and wall pressure gradient (WPG), and their association with the geometrical parameters of curvedness and stenosis. Secondly, we have similarly determined the wall shear stress and wall pressure gradient distributions in four patient-specific curved stenotic right coronary arteries (RCAs), which were reconstructed from medical images of patients diagnosed with atherosclerosis and stenosis; our results show high WSS and WPG regions at the stenoses and inner wall of the arterial curves. This paper provides useful insights into the causative mechanisms of the high incidence of atherosclerosis in coronary arteries. It also provides guidelines for how simulation of blood flow in patient's coronary arteries and determination of the hemodynamic parameters of WSS and WPG can provide a medical assessment of the risk of development of atherosclerosis and plaque formation, leading to myocardial ischemia and infarction. The novelty of our paper is in our showing how in actual coronary arteries (based on their CT imaging) curvilinearity and narrowing complications affect the computed WSS and WPG, associated with risk of atherosclerosis. This is very important for cardiologists to be able to properly take care of their patients and provide remedial measures before coronary complications lead to myocardial infarctions and necessitate stenting or coronary bypass surgery. We want to go one step further and provide clinical application of our research work. For that, we are offering to cardiologists worldwide to carry out hemodynamic analysis of the medically imaged coronary arteries of their patients and compute the values of the hemodynamic parameters of WSS and WPG, so as to provide them an assessment of the risk of atherosclerosis for their patients. Graphical abstract Theme and aims: Coronary arteries have high curvatures, and hence flow through them causes disturbed flow patterns, resulting in stenosis and atherosclerosis. This in turn decreases the myocardial flow perfusion, causing myocardial ischemia and infarction. Therefore, in order to understand the mechanisms of these phenomena caused by high curvatures and branching of coronary arteries, we have conducted elaborate hemodynamic analysis for both (i) idealized coronary arteries with geometrical parameters representing curvatures and stenosis, and (ii) patient-specific coronary arteries with stenoses. Methods and results: Firstly, in idealized coronary arteries with approximated realistic arterial geometry representative of their curvedness and stenosis, we have computed the hemodynamic parameters of pressure drop, wall shear stress (WSS) and wall pressure gradient (WPG), and their association with the geometrical parameters of curvedness and stenosis. Then, we have determined the wall shear stress and wall pressure gradient distributions in four patient-specific curved stenotic right coronary arteries (RCAs), that were reconstructed from medical images of patients diagnosed with atherosclerosis and stenosis, as illustrated in Figure 1, in which the locations of the stenoses are highlighted by arrows. Figure 1: Three-dimensional CT visualization of arteries in patients with suspected coronary disease. The arteries can be seen as a combination of various curved segments with stenoses at unspecific locations highlighted by arrows. Our results show high WSS and WPG regions at the stenoses and inner wall of the arterial curves, as depicted in Figure 2. Therein, the encapsulations show (i) high WSS, and (ii) high WPG regions at the stenosis and inner wall of the arterial curves. Figure 2: WSS and WPG surface plot of realistic arteries (a), (b), (c) and (d), wherein the small squared parts are enlarged to show the detailed localized contour plots at the stenotic regions. Therein, the circular encapsulations show (i) high WSS and (ii) high WPG regions at the stenosis and inner wall of the arterial curves. Conclusion and novelty: This paper provides useful insights into the causative mechanisms of the high incidence of atherosclerosis in coronary arteries. It also provides guidelines for how simulation of blood flow in patient coronary arteries and determination of the hemodynamic parameters of WSS and WPG can provide a medical assessment of the risk of development of atherosclerosis and plaque formation, leading to myocardial ischemia and infarction. The novelty of our paper is our showing how in actual coronary arteries (based on their CT imaging), curvilinearity and narrowing complications affect the computed WSS and WPG associated with risk of atherosclerosis. This is very important for cardiologists to be able to properly take care of their patients and provide remedial measures before coronary complications lead to myocardial infarctions and necessitate stenting or coronary bypass surgery. [ABSTRACT FROM AUTHOR]

It is of crucial importance whether or not evacuees follow the evacuation signs during building evacuation. It is necessary for effective evacuation signs to be designed in a way that helps the occupants follow building safety guidelines. In this paper, 658 evacuation experiments with wearable eye tracking devices were carried out to test the effectiveness of both the setting positions and design of evacuation signs in buildings. There are four factors considered in this paper: (1) position, (2) colour, (3) graphics, and (4) (or flashing). The results show that the effect of the green "arrow" evacuation sign is the best. The effect of low (corridor) signs works better than those of high (room) signs, but the signs of low (corridor) could be blocked by the front evacuees. Obtaining the ratio of people obeying the evacuation signs under different conditions provides an effective basis for the improvement in design for building safety, and provides data support for computer simulation modelling of crowd evacuation. [ABSTRACT FROM AUTHOR]

Steam flooding is a method of injecting steam to heat the oil and decrease its viscosity so that it will be easy to flow from injector to producer. Fula North East oil field is a massive edge and bottom water reservoir with good properties and high viscosity of crude oil. As of March 2018, the oil field has been fully commissioned in steam stimulation for 3 years and the water cut rises rapidly and the oil rate declines seriously. In this paper, through comprehensive analysis of the geological properties of reservoir, production dynamics of single well and cement quality of wellbore, the steam flooding pilot test area under different well groups is screened out. Advanced thermal enhanced oil recovery simulator has been used to build the model of 279, 888 cells to design and optimize steam flooding pilot area for this field. The best well space and development program are optimized; this paper supplies a theoretical foundation for the next step of steam flooding in the whole field. The results show that the optimum steam flooding parameters for this area are steam injection temperature of 270 °C, with 5–7 MPa injection pressure, steam injection quality of more than 0.6 and steam injection rate of 1.6 m3/day/ha/m, and the final recovery ratio will reach 32.3%. [ABSTRACT FROM AUTHOR]

Purpose: In this paper, we present strategies for active vibration suppression and defect detection in a one-dimensional network of an arbitrary number of coupled spring–mass units connected in series. The choice of a spring–mass system is not arbitrary, as the latter is found in many applications throughout a wide range of fields, for instance in defense detection/shielding studies, biomedical engineering, structures engineering, computer graphics and acoustics among others. Methods: The system of differential equations that model the spring–mass systems was analyzed and solved using the Laplace transform and other analytic tools. The data used in the numerical simulations were obtained by solving the associated forward problems analytically or numerically. Some of the simulations required numerical integration and minimization routines. Results: A scheme for active vibration suppression is given via explicit formulas for the required control forces. The detect defection strategy is given in terms of an explicit formula whenever only the location or mass of a lone defect is unknown and in terms of a minimization procedure whenever more than one information about the defect(s) are unknown. Several numerical simulations were done to validate these results. Conclusion: As we show in the paper, the success of the vibration suppression scheme we developed depends on the speed and accuracy of the intervening active controls. Meanwhile, the defect detection algorithm only requires measurements in a sufficiently large time interval of the longitudinal vibrations in the first mass. [ABSTRACT FROM AUTHOR]

During technological discontinuity based on the transition from second-generation (2G) to third-generation (3G) mobile telecommunications, Chinese manufacturing firms were catching up with leaders in the global industry. Using computer simulation, the paper examines the extent to which heterogeneous demand structures and competitive regimes affect technological catching up. The paper shows that - during technological discontinuity - a slightly higher technological opportunity in combination with low appropriability and heterogeneous demand are vital for technological catching up. The complementary effects of demand within different regimes of Schumpeterian Mark I and Mark II models are discussed. [ABSTRACT FROM AUTHOR]

Context: The testing of software-intensive systems is performed in different test stages each having a large number of test cases. These test cases are commonly derived from requirements. Each test stages exhibits specific demands and constraints with respect to their degree of detail and what can be tested. Therefore, specific test suites are defined for each test stage. In this paper, the focus is on the domain of embedded systems, where, among others, typical test stages are Software- and Hardware-in-the-loop. Objective: Monitoring and controlling which requirements are verified in which detail and in which test stage is a challenge for engineers. However, this information is necessary to assure a certain test coverage, to minimize redundant testing procedures, and to avoid inconsistencies between test stages. In addition, engineers are reluctant to state their requirements in terms of structured languages or models that would facilitate the relation of requirements to test executions. Method: With our approach, we close the gap between requirements specifications and test executions. Previously, we have proposed a lightweight markup language for requirements which provides a set of annotations that can be applied to natural language requirements. The annotations are mapped to events and signals in test executions. As a result, meaningful insights from a set of test executions can be directly related to artifacts in the requirements specification. In this paper, we use the markup language to compare different test stages with one another. Results: We annotate 443 natural language requirements of a driver assistance system with the means of our lightweight markup language. The annotations are then linked to 1300 test executions from a simulation environment and 53 test executions from test drives with human drivers. Based on the annotations, we are able to analyze how similar the test stages are and how well test stages and test cases are aligned with the requirements. Further, we highlight the general applicability of our approach through this extensive experimental evaluation. Conclusion: With our approach, the results of several test levels are linked to the requirements and enable the evaluation of complex test executions. By this means, practitioners can easily evaluate how well a systems performs with regards to its specification and, additionally, can reason about the expressiveness of the applied test stage. [ABSTRACT FROM AUTHOR]

In this paper, we propose and analyze a stochastic SIVS model with saturated incidence and Lévy jumps. We first prove the existence of a global positive solution of the model. Then, with the help of semimartingale convergence theorem, we obtain a stochastic threshold of the model that completely determines the extinction and persistence of the epidemic. At last, we further study the threshold dynamics of a stochastic SIRS model with saturated or bilinear incidence by a similar method and carry out some numerical simulations to demonstrate our theoretical results. Comparing with the method given by Zhou and Zhang (Physica A 446:204–216, 2016), we find that the method used in this paper is simple and effective. [ABSTRACT FROM AUTHOR]

This paper examines the experimental performance of ultra-high-performance steel fibre-reinforced concrete (UHPSFRC) beams subjected to loads at relatively low shear span-to-depth ratios. The results and observations from six tests provide a detailed insight into the ultimate response including shear strength and failure mode of structural elements incorporating various fibre contents. The test results showed that a higher fibre content results in an increase in ultimate capacity and some enhancement in terms of ductility. Detailed nonlinear numerical validations and sensitivity studies were also undertaken in order to obtain further insights into the response of UHPSFRC beams, with particular focus on the influence of the shear span-to-depth ratio, fibre content and flexural reinforcement ratio. The parametric investigations showed that a reduction in shear span-to-depth ratio results in an increase in the member capacity, whilst a reduction in the flexural reinforcement ratio produces a lower ultimate capacity and a relatively more flexible response. The test results combined with those from numerical simulations enabled the development of a series of design expressions to estimate the shear strength of such members. Validations were performed against the results in this paper, as well as against a collated database from previous experimental studies. [ABSTRACT FROM AUTHOR]

In view of the important influence of mechanical damage on the bearing capacity of buried pipelines, the residual strength of dented pipelines has become a hot issue in the pipeline industry. In this paper, X52 steel grade, commonly used in buried pipelines, is taken as the research object. The material properties are obtained by tensile test. The difference of curvature radius at the tip of the dent is accurately considered. Based on finite element method, the limit depth and the failure pressure of the dented pipelines are studied. Results have shown that the ultimate displacement load increases exponentially with the increase in the radius of curvature. When dent depth is small, the dent will not reduce the failure pressure, no matter it is smooth or sharp. As the dent depth increases, the influence of the radius of curvature at the tip of the dent becomes significant. The critical radius of curvature from sharp dent to smooth dent is analyzed. And the corresponding relationship between it and dent depth is obtained. It is found that when the radius of curvature exceeds 50 mm, the dent depth does not affect the failure pressure of the pipeline. An expression about the two parameters is put forward, providing supplementary suggestions for the depth-based evaluation criterion. This paper affords a strong support for better assessment of dented pipelines. [ABSTRACT FROM AUTHOR]

This paper considered the problem of numerical simulation of an incompressible dam break flow consisting of three phases. The movement of the water free surface was carried out using the Newtonian fluid model, and the mud impurity movement was performed by the non-Newtonian fluid model based on the VOF method. The PISO numerical algorithm was chosen as a numerical method for solving equations. This paper discusses the problems of dynamic loads arising from the impact of a dam break flow using numerical modeling. The obtained numerical results were compared with the two experiment results, which allow confirming the behavior of the instantaneous flow and the evolution of pressure at the relative points of the obstacle. Moreover the water flow and non-Newtonian fluid for different forms of obstacles were also modeled. It was found that a non-Newtonian fluid extremely reduces the maximum shock pressure value of the water flow. [ABSTRACT FROM AUTHOR]

In this paper, we are concerned with the existence and global exponential stability of pseudo-almost-periodic solutions for quaternion-valued recurrent neural networks (RNNs) with time-varying delays. By using the Banach fixed point theorem and proof by contradiction, we directly study the existence and exponential stability of pseudo-almost-periodic solutions of the quaternion-valued systems under consideration without decomposing them into into real- or complex-valued systems. Our results obtained in this paper are new. Finally, we give a numerical example and computer simulation to illustrate the feasibility of our results. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the nonparametric regression model based on extended negatively dependent errors. Some consistency results for the estimator of the regression function g(x) are presented, including the rates of strong consistency and complete consistency, and the mean convergence. The results obtained in this paper improve and extend the corresponding ones of Yang and Wang (Acta Math Appl Sin 22(4):522–530, 1999) and Priestley and Chao (J R Stat Soc B 34:385–392, 1972). Finally, we present a numerical simulation study to verify the validity of the results established here. [ABSTRACT FROM AUTHOR]

This paper examines the structural response of reinforced concrete flat slabs, provided with fully-embedded shear-heads, through detailed three-dimensional nonlinear numerical simulations and parametric assessments using concrete damage plasticity models. Validations of the adopted nonlinear finite element procedures are carried out against experimental results from three test series. After gaining confidence in the ability of the numerical models to predict closely the full inelastic response and failure modes, numerical investigations are carried out in order to examine the influence of key material and geometric parameters. The results of these numerical assessments enable the identification of three modes of failure as a function of the interaction between the shear-head and surrounding concrete. Based on the findings, coupled with results from previous studies, analytical models are proposed for predicting the rotational response as well as the ultimate strength of such slab systems. Practical recommendations are also provided for the design of shear-heads in RC slabs, including the embedment length and section size. The analytical expressions proposed in this paper, based on a wide-ranging parametric assessment, are shown to offer a more reliable design approach in comparison with existing methods for all types of shear-heads, and are suitable for direct practical application. [ABSTRACT FROM AUTHOR]

On the basis of momentum conservation and mass conservation theory, this paper proposes mathematical model to investigate recovered water flow and contaminant diffusion in the wellbore of shale gas horizontal wells. Two significant improvements are made to conventional models. One is that the quality and velocity flow of each cluster are considered as dynamic parameters in equation of flow, and another one is that source terms and reaction terms are considered as dynamic parameters in equation of contaminant diffusion. The validity of the model of recovered water flow and contaminants diffusion is verified by comparing the predicted results with the actual production data and the experimental data in the literature. Then main factors affecting the concentration of contaminants in horizontal wells are studied systematically. It can be shown that the concentration of contaminants at wellhead increases linearly with the linear increase of the initial concentration, boundary concentration and the source term in the whole time period. The concentration of contaminants increases nonlinearly with the linear increase of the length of horizontal wellbore and flow-back average velocity of recovered water in different time periods. The research of this paper provides guidance for the control of recovered water. [ABSTRACT FROM AUTHOR]

In many motion control problems of mechatronic equipment, the control performance of the final-state of the control period is strictly important for positioning or settling issues. Totani and Nishimura proposed a final-state control (FSC) method using the compensation input for achieving such requirements in 1994. The FSC technique has been improved and applied to various kinds of actual mechanical motion control problems. In the same way, there is a similar method to solve these kinds of problems called model predictive control (MPC). However, the difference between FSC and MPC has not been fully clarified yet. This paper shows the relationship between the FSC and MPC methods. First, an updating-type FSC (UFSC) proposed by a part of the authors is introduced. Then, this paper analytically shows that the control input of UFSC agrees in the input of MPC under some conditions. This analysis makes clear the meaning of "updating" in the FSC technique for actual mechanical motion control applications. Moreover, this paper shows an application of the UFSC to a three-dimensional positioning problem with a fixed-wing airplane and performs numerical simulations to help the understanding the characteristics of the UFSC. Through the discussions of this paper, the characteristic of the FSC is clarified. [ABSTRACT FROM AUTHOR]

Solid dynamic deformation and multiphase fluid coupling driven by numerical simulation have manifested their significance for many graphics applications during the past 2 decades. For example, the fluid implicit particle (FLIP) method and shape matching constraint based on position-based dynamics (PBD) have demonstrated their unique graphics strength in fluid and solid animation, respectively. In this paper, we propose a novel integrated approach supporting the seamless unification of FLIP and dynamic shape matching. We devise new algorithms to tackle existing difficulties when handling new phenomena such as high-fidelity fluid–solid interactions, solid deformations, melting and immiscible fluid coupling. The key innovation of this paper is a unified Lagrangian framework that seamlessly blends FLIP- and PBD-based shape matching constraints toward the natural yet flexible coupling between fluid and deformable solid. Within our integrated framework, it enables many complicated fluid–solid phenomena with ease. We conduct various kinds of experiments, all the results demonstrate the advantages of our unified hybrid approach toward visual fidelity, computational efficiency, numerical stability, and application versatility. [ABSTRACT FROM AUTHOR]

We study the problem of the determination of a high precision cosmological mass function, which is of fundamental importance in several problems of astrophysics, like the building up of an halo model. The determination of a mass function through numerical simulation is time demanding, and restrict to particular cosmological parameters. Analytical methods, allow to determine high precision mass functions, without the limitations of the simulations. We improve on previous analytical models, reaching high level of precision. In particular, we improve the scheme of Del Popolo presented in older and more recent papers, based on the excursion set approach. We further improve the mass function with respect to the quoted papers, using an higher order first crossing distribution, and an improved barrier with respect previous papers. As a result, we can obtain a mass function with a precision of 1%, in the mass range ≃ (109−1015) h−1M☉, and in the redshift range 0 < z s< 10. The paper also shows how the use of the quoted improved first-crossing distribution, improves the agreement between the conditional mass function, and simulations. [ABSTRACT FROM AUTHOR]

The paper deals with the stability and bifurcation analysis of a class of simplified five-neuron bidirectional associative memory neural networks with four delays. By discussing the characteristic transcendental equation and applying Hopf bifurcation theory, some sufficient conditions which guarantee the local stability and the existence of Hopf bifurcation of the neural networks are established. With the aid of the normal form theory and center manifold theory, we obtain some specific formulae to determine the stability and the direction of the Hopf bifurcation. Computer simulations are implemented to explain the key mathematical predictions. The paper ends with a brief conclusion. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the parametric component and nonparametric component estimators in a semiparametric regression model based on φ -mixing random variables. The rth mean consistency, complete consistency, uniform rth mean consistency and uniform complete consistency are established under some suitable conditions. In addition, a simulation to study the numerical performance of the consistency of the nearest neighbor weight function estimators is provided. The results obtained in the paper improve the conditions in the literature and generalize the existing results of independent random errors to the case of φ -mixing random errors. [ABSTRACT FROM AUTHOR]

When the observed data set contains outliers, it is well known that the classical least squares method is not robust. To overcome this difficulty, Wang et al. (J Am Stat Assoc 108(502): 632–643, 2013) proposed a robust variable selection method by using the exponential squared loss (ESL) function with a tuning parameter. Although many important statistical models are investigated, to date, in the presence of outliers there is no paper to study the partially nonlinear model by using the ESL function. To fill in this gap, in this paper, we propose a robust and efficient estimation method for the partially nonlinear model based on the ESL function. Under certain conditions, we have shown that the proposed estimators can achieve the best convergence rates. Next, the asymptotic normality of the proposed estimators is established. In addition, we develop a new minorization–maximization algorithm to calculate the estimates for both non-parametric and parametric parts and present a procedure for deriving initial values. Finally, we provide a data-driven approach to select the tuning parameters. Numerical simulations and a real data analysis are used to illustrate that when there are outliers, the proposed ESL method is more robust and efficient for partially nonlinear models than the existing linear approximation method and the composite quantile regression method. [ABSTRACT FROM AUTHOR]

This paper demonstrates a methodology for flexible, dynamic systems modelling relevant to urban rail decarbonisation. Decarbonisation of urban rail is a vital component of policy and strategy to minimize anthropogenic emissions. Decarbonisation is a systems problem, however, that needs to reflect the interaction between components and processes. Dynamic computer modelling of systems for decarbonisation involves interfacing multiple models together and running them in parallel in order to observe and predict systems-level effects. This is challenging due to the diverse nature of models, achieving parallel model integration and concerns around intellectual property (IP). One solution is the multi-modelling paradigm, which supports integrated, diverse, secure interfacing of models. This paper demonstrates the application of the multi-modelling approach, using the INTO-CPS tool chain. A multi-model was developed comprising key components required for urban rail decarbonisation problems. This multi-model was tested for power consumption in four different scenarios with an example drawn from the Tyne and Wear Metro in Newcastle-upon-Tyne in the United Kingdom. These scenarios compared combinations of decarbonisation intervention (baseline rolling stock versus lightweight, regenerative braking rolling stock and baseline driving style versus energy-efficient defensive driving style), generating different power consumption profiles for each. As such, this serves as a proof of the application of the multi-modelling approach and demonstrates a number of benefits for flexible and rapid systems modelling. This paper fills a knowledge gap by demonstrating a potentially valuable tool for future systems-level decarbonisation challenges in urban rail. [ABSTRACT FROM AUTHOR]

The paper discusses the possibility of detecting local damages in complex structures typical of civil engineering, as multispan beams and trusses. Namely, it describes a procedure to identify localised cracks in structures in the elastic range of behaviour using only the values of natural frequencies in the intact configuration and in the damaged one evaluated by means of dynamic tests. The error minimisation procedure described in the paper selects the solution within a set of finite element models that simulate a range of positions and levels of damage, by identifying the damaged configuration as the one whose modal frequencies minimise the least-square difference with the measured data. The accuracy of the method is first investigated by applying it to the damage detection of a two-span steel beam, whose modal frequencies were obtained by means of experimental tests. To explore the accuracy of the proposed procedure, numerically simulated data with random noise were also generated for several positions and levels of damage and for different values of the random noise. The procedure was then extended, by means of numerical simulations, to the case of a beam with two localised damages. Finally, the procedure proposed for multispan beams is adapted to the damage identification of plane truss structures. [ABSTRACT FROM AUTHOR]

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In this paper, the competing requirements of material strength, casting formation and residual stress are considered in the design of a large bulkhead integral isothermal forging die using a design approach that incorporates an outer ring plus a die body. Thermal stress assembly was conducted to resolve the various manufacturing issues encountered in the production of this large-scale casting. This paper also proposes a design method for an expansion joint and material-saving holes to homogenize the cross-sectional thickness of the casting die by solving problems associated with defects and hot cracking during the casting process. The finite element method was used based on the equivalent liquid level descending method, the Niyama criterion, etc., to analyze the pouring of the sand model with different risers to choose the casting process. To resolve the occurrence of hot cracks during production, the design was optimized and the process was improved in combining with the simulation analysis result, after which carrying out another finite element analysis and by re-verifying the production process again. The results show that the simulated porosity, shrinkage and stress distribution are in accord with the practical production status. Based on the mechanical properties and a microstructure analysis, the tension strength of the K3 casting die at 950 °C is approximately 635 MPa, and the microstructures are typical dendrites. However, through the simulation, practical production, and analysis of the mechanical properties and microstructure, the die design method proposed in this paper offers benefits in solving casting forming problems and hot cracking of an integral oversized titanium bulkhead casting die, and a K3 superalloy die with a weight of 7.8 tons was successfully cast. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to identify (1) the type of skill evaluation methods and (2) how the effect of training was evaluated in simulation-based training (SBT) in pediatric surgery.Methods: Databases of PubMed, Cochrane Library, and Web of Science were searched for articles published from January 2000 to January 2017. Search concepts of Medical Subject Heading terms were "surgery," "pediatrics," "simulation," and "training, evaluation."Results: Of 5858 publications identified, 43 were included. Twenty papers described simulators as assessment tools used to evaluate technical skills. Reviewers differentiated between experts and trainees using a scoring system (45%) and/or a checklist (25%). Simulators as training tools were described in 23 papers. While the training's effectiveness was measured using performance assessment scales (52%) and/or surveys (43%), no study investigated the improvement of the clinical outcomes after SBT.Conclusion: Scoring, time, and motion analysis methods were used for the evaluation of basic techniques of laparoscopic skills. Only a few SBT in pediatric surgery have definite goals with clinical effect. Future research needs to demonstrate the educational effect of simulators as assessment or training tools on SBT in pediatric surgery. [ABSTRACT FROM AUTHOR]

This paper is concerned with fractional-order neural networks with proportional delays. Applying inequality technique, some sufficient criteria which ensure the stability of such fractional-order neural networks with proportional delays over a finite-time interval are established. Computer simulations are carried out to illustrate our theoretical predictions. The derived results of this paper are new and complement some earlier ones. [ABSTRACT FROM AUTHOR]

The paper discusses methodological techniques for increasing the diagnostic value of routine angiographic examinations of patients. It presents algorithms for digital processing of heart video images, which make it possible to quantitatively characterize hemodynamics in the coronary bed by determining the velocity of spread of a contrast agent through the arteries. The proposed approach includes several stages and procedures and takes account of the errors caused by the movement of the arteries due to the mechanical activity of the heart. The paper presents the results of estimating coronary blood-flow velocity in a patient with coronary heart disease, which are compared with computer simulation data. The sources of errors, ways to minimize them, and prospects for using the proposed methodology for effective angiographic diagnosis are discussed. [ABSTRACT FROM AUTHOR]

This paper presents the construction of a computer model of crater formation during nanosecond laser evaporation of matter based on the example of monocrystalline silicon. The computer simulation is used to determine the dynamics of crater formation on the material surface exposed to nanosecond laser pulses. The diameter of the obtained crater and its depth were evaluated. The corresponding experiments on laser ablation of monocrystalline silicon were also carried out. Analysis of experimental data and simulation results showed that depending on the pulse duration and energy density of laser radiation the mechanism of material removal changes. Thus, the presence of the liquid phase in the ablation process seriously affects the crater depth and diameter for the entire range of energy densities from 0.4 to 104.0 J/cm2. It is shown that the computer model makes it possible to determine the volume of removed material due to evaporation and evaluate the effect of the liquid phase on crater characteristics. [ABSTRACT FROM AUTHOR]

The droplet impact on solid surfaces is a popular research topic in which many researchers focus on stationary surfaces, only a few researches have been conducted for moving surfaces. In this paper, a high-speed photography-based droplet impact experimental platform and a VOF-based numerical simulation model are built to study the morphology of motion of a droplet after it impacted a horizontal uniformly moving surface. In the present study, the tangential and normal Weber numbers range within 70. This is because at such low Weber numbers the droplets initially spread to their maximum diameter after impacting the moving surfaces and subsequently start to rebound. The studies have confirmed that the maximum spreading factor of the droplet increases linearly with the tangential Weber number, and the spreading time increases as well. The maximum spreading factor of the droplet increases nonlinearly as a function of the normal Weber number and corresponding time initially increases and then decreases. Finally, the expression for the maximum spreading factor is fitted according to its correlation with the We number. [ABSTRACT FROM AUTHOR]

The capabilities of the numerical simulation of technological processes are limited by the accuracy and efficiency of determining the properties of materials continuously changing under repeated heating and cooling. The parameters of structural transformations are the principal factors affecting the properties of alloyed steels. In this paper, we present a method for determining the parameters of relationships describing C-shaped curves in the experimental diagrams of isothermal decomposition of austenite. The proposed approach makes it possible to reconstruct the entire C-shaped curve using a relatively small fragment near the "nose" (based on three points). The joint processing of a series of curves provides determining the parameters of ferritic, pearlitic and bainitic transformation kinetics. However, one should take into account the distinctive features of the diffusion decomposition of austenite. For example, ferrite and pearlite are formed in overlapping temperature ranges and have similar mechanical properties, but their combining into a single ferrite-pearlitic structure complicates the construction of a mathematical model for the transformation. The bainitic transformation is a transient one between diffusion and diffusionless transformations. In a part of the transformation temperature range the limit of conversion level is a function of temperature (just as in the case of martensitic transformation). It has been shown that, for the case of ferrite-pearlitic transformation, the best results can be obtained with the use of Kolmogorov–Avrami equation, whereas for the case of bainitic transformation, the best results can be obtained with the use of Austin–Rickett equation modified to take into account an incomplete conversion level of the transformation. [ABSTRACT FROM AUTHOR]

For realizing the precision dressing of worm grinding wheel of face gear, this paper studies the over-cutting phenomenon of worm grinding wheel in forming dressing and puts forward the solution. Combined with the forming principle of face gear worm and forming dressing method, the influence of the continuous dressing method on the grinding wheel helix and the relative position between the dresser and the worm are expounded. Based on the numerical simulation model and the actual machining phenomenon, two kinds of over-cutting phenomenon are discovered. To ensure the surface integrity of grinding wheel in continuous processing, the reasons and laws of over-cutting are deeply analyzed. The first kind of over-cutting can be eliminated by increasing the angle between the extended line and the axis on the dresser, and a method of estimating the minimum angle is proposed for a more reasonable design of the dresser. The second kind of over-cutting can be eliminated by choosing proper dressing interval while ensuring the utilization efficiency of worm, and the selection criteria of dressing interval in continuous dressing are put forward. To verify the proposed methods, digital model, Vericut, and SolidWorks are applied, and the results show that the proposed method can effectively solve the over-cutting problem. [ABSTRACT FROM AUTHOR]

Aerodynamic characteristics of long-span bridges with box girders have been investigated widely, and this paper presents a study on a cable-stayed bridge with two box girders in parallel arrangement. Computational fluid dynamics (CFD) numerical simulations were adopted to analyze the aerodynamic interference between the upper and the lower box girders. After checking the reliability of the numerical model, different angles of attack and different distances between the two girders were considered, and the variations of the aerodynamic characteristics were discussed, including the aerodynamic coefficients and the static pressure distributions. Then, the wind environment around the two box girders was focused, and the effect on the aerodynamic coefficients of a vehicle was also studied. The results show that the aerodynamic interference between the two box girders is strong, so the aerodynamic characteristics of the two boxes are different from those of a single box. The flow field between the boxes have higher wind velocities, which makes the aerodynamic force on the upper box and the lower box become upward and downward, respectively. Meanwhile, the aerodynamic forces on vehicles above the lower deck surface are larger due to the accelerated flow between the two boxes. [ABSTRACT FROM AUTHOR]

This paper presents results of computer simulation experiments based on density functional calculations of the atomic structure and electronic spectrum of (n = 15–17) clusters. Based on the Wade–Mingos rules, we identify general trends in the formation of monoanionic hafnium-doped Sn clusters, which make it possible to optimize prognostic studies concerned with a search for novel nanostructured materials. We compare calculation results obtained with the B3LYP, B3PW91, and PBE functionals in combination with the SDD basis set and analyze the effect of the functionals on atomic structure optimization results. An optimal strategy is proposed for computer simulation experiments dealing with modeling of the spatial structure of Sn-based clusters and confirmed by comparison with available experimental data. [ABSTRACT FROM AUTHOR]

The ultra-reliable and low-latency communication (URLLC) in the fifth generation (5G) communication has emerged many potential applications, which promotes the development of the internet of things (IoTs). In this paper, the URLLC system adopts the duty-cycle muting (DCM) mechanism to share unlicensed spectrums with the WiFi network, which guarantees the fair coexistence. Meanwhile, we use the mini-slot, user grouping, and finite block length regime to satisfy the low latency and high reliability requirements. We establish a non-convex optimization model with respect to power and spectrum, and solve it to minimize the power consumption at the devices, where the closed-form expressions are given by several mathematical derivations and the Lagrangian multiplier method. Numerical simulation results are provided to verify the feasibility and effectiveness of the proposed scheme, which improves the system spectrum efficiency and energy efficiency. [ABSTRACT FROM AUTHOR]

Mechanics of multicomponent and multiphase media is a branch of fluid mechanics. Mathematical modeling of the dynamics of inhomogeneous media is of great importance because the experimental study of many of these processes is difficult. At the same time, many models are essentially nonlinear; for this reason, numerical methods are used to integrate such models. In a number of industrial energy technologies, to remove the dispersed component of an aerosol medium, gas–drop media are affected by acoustic fields. This is the reason for the interest in studying the dynamics of aerosols in acoustic fields, revealing the fundamental regularities of such flows, and also in developing mathematical models for the dynamics of aerosol media. Materials and methods. The paper presents a continuum mathematical model of aerosol dynamics. The model takes into account both intercomponent momentum exchange and intercomponent heat transfer. The system of equations of the mathematical model is solved by the finite difference method, and a nonlinear correction scheme is used to suppress numerical oscillations. Results. Oscillations of a gas suspension in a closed container at the resonance frequency are modeled. The distributions of physical parameters of the carrier medium and the dispersed component in the process of aerosol oscillations are obtained. Conclusions. Comparison of the results of numerical calculations with physical experiment data gives a satisfactory agreement. [ABSTRACT FROM AUTHOR]

Modeling flows in fractured porous media is important in applications. One main challenge in numerical simulation is that the flow is strongly influenced by the fractures, so that the solutions typically contain complex features, which require high computational grid resolutions. Instead of using uniformly fine mesh, a more computationally efficient adaptively refined mesh is desirable. In this paper we design and analyze a novel residual-type a posteriori error estimator for staggered DG methods on general polygonal meshes for Darcy flows in fractured porous media. The method can handle fairly general meshes and hanging nodes can be simply incorporated into the construction of the method, which is highly appreciated for adaptive mesh refinement. The reliability and efficiency of the error estmator are proved. The derivation of the reliability hinges on the stability of the continuous setting in the primal formulation. A conforming counterpart that is continuous within each bulk domain for the discrete bulk pressure is defined to facilitate the derivation of the reliability. Finally, several numerical experiments including multiple non-intersecting fractures are carried out to confirm the proposed theories. [ABSTRACT FROM AUTHOR]

This paper is a study on energy efficiency prediction model of heavy-duty electric vehicles using numerical simulation. Because the current energy consumption efficiency evaluation method for electric vehicles has limitations in terms of manpower, resources, and time required, therefore a simulation model development to predict electric vehicle energy consumption efficiency is needed. Furthermore, research on heavy-duty electric vehicles is relatively insufficient compared to light-duty electric vehicles, and the need of research on heavy-duty electric vehicles is increasing. Therefore, this study develops an energy efficiency prediction model for heavy-duty electric vehicles and verifies it with the experimental results. Based on this, the applicability of the simulation method using the developed prediction model to the current energy efficiency evaluation management system for heavy-duty electric vehicles was reviewed. To verify the accuracy of the simulation model, the dynamometer test results were compared to simulation results, and the UDS protocol was used to acquire internal data for heavy-duty electric vehicles. Reliability of simulation model was secured by comparing data such as motor speed, battery voltage/current, state of charge and total driving distance of the test vehicles with data from the dynamometer experiment and the simulation model. [ABSTRACT FROM AUTHOR]

The strain-hardening behavior of soils and rocks under compression is critical for evaluating the construction stability in geological and mining engineering. Numerical simulation is an effective approach and widely used in the stability analysis of constructions. To ensure the accuracy of the simulation results, it is necessary to select appropriate constitutive models and determine the correct model parameters. The double-yield model, built in FLAC3D, is often used to describe the strain-hardening behavior of geotechnical materials. On the assumption that there is only volume yielding in the material, a relationship between the cap pressure, plastic strain in the double-yield model, and the axial stress–strain in the compression test with axial loading and four lateral-face constraints was established. Then, the cap pressure and plastic strain could be calculated directly by a series of known axial stress–strain data. With this calculation method, the double-yield model parameters can be determined quickly and accurately. This method was derived based on the constitutive equation of the double-yield model and could quickly determine the model parameters by reverse calculation according to the expected results, so it was more efficient and credible than the more widely used trial-and-error method. Based on comparisons between the calculation and trial-and-error methods, some case studies also proved its efficiency and effectiveness. Moreover, there are no requirements for the source of known stress–strain data. Therefore, this method can be applied to the model parameter assignment based on the stress–strain data from experimental tests, theoretical analyses, empirical formulas, and other numerical simulations. Highlights: A relationship between the double-yield model parameters and the axial stress-strain in a uniaxial loading test with lateral constraints was established. An approach for accurate numerical modeling of strain-hardening materials using a double-yield model was developed. Some contrastive analyses with similar studies were conducted to verify the accuracy and efficiency of the approach in this paper. [ABSTRACT FROM AUTHOR]

For the outside cabin heat exchanger of wind power generation, the overall numerical simulation plays an important role in its design and optimization. The periodic iterative simulation method proposed in this paper makes up for the deficiency of analogy research using the local model in the previous research of plate-fin heat exchanger so that the research conclusions can be directly applied to practical engineering. The effectiveness of this method is verified by comparing 10 groups of simulation results with experimental results. It is concluded that the maximum relative error of the periodic iterative simulation method is 0.9%, which meets the requirements of engineering calculation. The number of iterations can be reduced to two when only the outlet average temperature is involved, which is more convenient than the dozens of iterations. Furthermore, the effects of altitude, air velocity, air temperature, wave fin structure parameters, and generator power on the performance of heat exchanger are comprehensively analyzed. The results show that larger naturally captured air volume, lower ambient temperature, and lower altitude can effectively reduce the outlet temperature of ethylene glycol solution. When the amplitude and wavelength of the corrugated fin on the airside of the heat exchanger are 0.6 mm and 20 mm respectively, the naturally captured air volume is effectively increased, the overall heat exchange performance of the heat exchanger is further improved. [ABSTRACT FROM AUTHOR]

The conventional Arrhenius equation that estimates the heat generation of coal in numerical simulation has been widely applied. However, the aging effect markedly influences the exothermic behavior of coal at low temperature and cannot be achieved using the conventional Arrhenius equation. In this paper, an improved wire-mesh basket test was performed to measure the temperature and concentrations of CO and CO2 emitted from coal piles. The aging effect model based on the theory of equivalent oxidation exposure time successfully matched the experimental results. Then, a two-dimensional (2D) multifield coupling model of coal stockpiles was developed considering the aging effect to investigate the developments on values and moving paths of temperature and O2 concentration. Effects of decay-power factor, which determines the diminishing coal oxidation, and other main variables on spontaneous combustion of coal stockpiles were systematically investigated. The results indicated a unique critical value of 1.25 × 10–6 s−1 for decay-power factor. Increasing decay-power factor enlarged the safe storage time and hardly affected the moving paths of the hotspot. There are two critical values for particle size (0.7 mm, 9 mm) and porosity (0.18, 0.58), and one critical value for wind velocity (8.5 m s−1) and stockpile width (9 m). Porosity and stockpile width have significant effects on the self-ignition of coal stockpiles when their values are lower than the base ones (0.33 and 15 m). The model considering aging effect is expected to reliably predict the spontaneous combustion of coal stockpile and become the tool for inspecting the reasonability of the relative preventing measures. [ABSTRACT FROM AUTHOR]