Modeling of asphalt concrete via simulated annealing

In this study, 65 asphalt core specimens taken from D100/11 state highway section in Turkey were examined for their physical properties in the laboratory. Analysis of data was conducted to determine the effects of the varying environment temperature and varying length of exposure to these temperatures on the stability of the asphalt core samples using destructive, Marshall, method. The asphalt core samples were determined using SPSS statistical program for modeling. Simulated annealing was implemented to determine a set of unknown parameters which best matched the asphalt concrete model predictions with experimental data. This modeling procedure can be used as a guideline for experiments to improve the stability of the asphalt concrete. The stability of the asphalt concrete is taken as the main objective function with respect to voids of volume, saturated unit volume weight, air dry unit volume weight, environment temperature, and exposure time.     

Modeling of axially symmetric flow reactors

A method of calculating the velocity profiles and species concentrations in axially symmetric flow reactors is presented. The method is illustrated with a reactor consisting of three concentric tubes arranged so that reactants flow through the inner tube and inner annulus to a mixing region and the products flow out through the outer annulus. A single bimolecular reaction is used in the example. The method involves two steps; calculation of the velocity field from a solution of the Navier-Stokes equations, followed by solution of the species conservation equations. The technique provides a way of analyzing reactors with variable cross sections and sampling ports near mixing regions.     

知识流的Petri网模型

Petri网是一种用以刻画通信机制的建模工具,在流程控制上得到了广泛应用。知识管理作为一种新的管理理论,其研究尚停留在对基本概念的剖析和激励方式的探索上。知识管理的对象是“知识”,对知识流动机制的刻画能够更好地描述企业的知识资产分布情况,方便监控并进行知识管理。用Petri网作为工具对知识的流动进行建模,从而得到知识流的概念模型。解决了对知识流动的共享性、并行性、复杂性、分布性等特性的刻画,为知识管理提供了知识流的建模工具,并为进一步对知识流实施监控提供了可能性。最后对知识流模型进行了应用研究,对Petri网对于知识流的建模能力予以说明。     

高精度超声流量传感器建模

介绍基于Prandtl的流速分布经验公式、光滑管的Prandtl方程和粗糙管的Colebrook方程的超声流量传感器建模,以及超声流量计高精度测量的实现方法。通过M atlab仿真分析流速分布指数和流速分布系数的计算方法及其对流速测量的影响。最后,通过实验数据的误差分析,验证模型的正确性,其测量精度可达1%。     

Prediction of fresh and hardened properties of self-compacting concrete using support vector regression approach

Neural Computing and Applications - This article presents the feasibility of using support vector regression (SVR) technique to determine the fresh and hardened properties of self-compacting...     

Modeling fibrin aggregation in blood flow with discrete-particles

Excessive clotting can cause bleeding over a vast capillary area. We study the mesoscopic dynamics of clotting by using the fluid particle model. We assume that the plasma consists of fluid particles containing fibrin monomers, while the red blood cells and capillary walls are modeled with elastic mesh of "solid" particles. The fluid particles interact with each other with a short-ranged, repulsive dissipative force. The particles containing fibrin monomers have a dual character. The polymerization of fibrin monomers into hydrated fibrins is modeled by the change of the interactions between fluid particles from repulsive to attractive forces. This process occurs with a probability being an increasing function of the local density. We study the blood flow in microscopic capillary vessels about 100 microm long and with diameters in order of 10 microm. We show that the model of polymerization reflects clearly the role played by fibrins in clotting. Due to the density fluctuations caused the by the high acceleration, the fibrin chains are produced within a very short time (0.5 ms). Fibrin aggregation modifies the rheological properties of blood, slows down the incipient flow, and entraps the red blood cells, thus forming dangerous clots.     

Modeling steady axis-symmetric thermal plasma flow of air by a parallelized magneto-hydrodynamic flow solver

This paper discusses a parallelized magneto-hydrodynamic flow solver for modeling axis-symmetric thermal plasma flow using Cartesian grid system and taking the induced electrical and magnetic effects into account, where the magneto-hydrodynamic equations, including the continuity equation, momentum equations, energy equation, current continuity equation and turbulence transport equations are solved by a finite volume discretization in a segregated manner. The thermal plasma flow of a 476 mm long, transferred well-type plasma torch operating with air is simulated for two power conditions, i.e. I = 432 A and 901 A, to demonstrate the capability of proposed numerical model to analyze the heat and mass transfer characteristics of axis-symmetric thermal plasma flow, where the location of cathode is determined by fixing the measured voltage drop between two electrodes. The numerical calculation suggests that the high-power case can deliver an axial velocity of 400 m/s and 15,000 K in temperature at the center of torch outlet, where a strong jetting vortex is expected emitting from the torch body. The low-power case is predicted with a longer electric arc than that of the high-power one, which clearly results in a large high-temperature region between the gas inlet and cathode and unfavourable to reduce the cathode erosion and to increase thermal efficiency.     

ORICRETE: Modeling support for design and manufacturing of folded concrete structures

The paper presents a flexible and efficient modeling approach to the simulation of the folding process of general crease patterns. The development of the model has been motivated by the need to provide support for targeted design and efficient manufacturing of shell structures inspired by the origami technique. This type of structures is becoming increasingly popular in many engineering disciplines and has been referred to as origamics. In the present work the folding technique is used to produce spatial structures from continuously reinforced thin-walled cementitious composite plates without the need to construct curved spatial formworks. In order to support the targetted design and manufacturing of folded concrete (oricrete) structures numerical model has been formulated as an optimization framework with several types of optimality conditions and equality constraints. The model is used both for form-finding of the spatial structure and for the realization of the manufacturing process.     

Prediction of interface yield stress and plastic viscosity of fresh concrete using a hybrid machine learning approach

The interface yield stress and the plastic viscosity of concrete mixes critically influence their pumpability. This study constructs and verifies a data-driven method for predicting these two important parameters. The proposed method is a hybridization of Least Squares Support Vector Machine (LSSVM) and Particle Swarm Optimization (PSO). The LSSVM is employed to infer the mapping function between the two concrete mix’s parameters and their influencing factors. Moreover, in order to overcome the challenging task of fine-tuning the LSSVM model hyper-parameters, the PSO algorithm, a swarm intelligence based metaheuristic, is utilized to optimize the LSSVM prediction model. A data set including 142 experimental tests has been collected in this study to construct and verify the proposed hybrid method. Experimental results supported by the Wilcoxon signed-rank test point out that the hybridization of LSSVM and PSO (with coefficients of determination = 0.71 and 0.77 for interface yield stress and plastic viscosity predictions, respectively) can deliver predictive results superior to those of benchmark models. Hence, the hybrid model of PSO and LSSVM can be a promising alternative to assist engineers in the task of concrete structure construction.     

A success history-based adaptive differential evolution optimized support vector regression for estimating plastic viscosity of fresh concrete

Engineering with Computers - Plastic viscosity is an important parameter of fresh concrete mixes. This research investigates a machine learning-based method for constructing a functional mapping...     

网络流驱动的复杂输运网络演化模型

传统复杂网络演化模型在网络拓扑结构与边权演化的机制设计中,未考虑网络流对于输运网络演化的驱动作用。引入网络流的动态驱动机制,分析网络流的规模增长、空间距离的制约与最短路径的配流策略三种因素,在输运网络的演化过程中所发挥的作用。发现这三种因素并不足以改变复杂网络的无标度性;基于最短路径的配流机制是网络流分布不均的关键影响因素;空间距离抑制作用对于网络相配性具有关键影响作用。     

Modeling of axis-symmetric steam plasma flow in a non-transferred torch

This paper discusses the numerical modeling of steam plasma in a DC non-transferred torch equipped with well-type cathode, where the non-trivial azimuthal velocity component and turbulent effect are both taken into account. In order to investigate the complicated flow characteristics of thermal plasma due to the interaction between steam and electric arc, the flow filed inside the plasma torch is modeled by the magnetic–hydrodynamic (MHD) equations. The governing equations are then solved numerically using a non-staggered finite volume discretization based on Cartesian grid system. The anode location and maximum current density at cathode are fixed by the corresponding experimental measurement at a given flow rate. The predicted result suggests that the steam plasma can be accelerated to a mean velocity of 1500 m/s at torch outlet with the mass flow rate of 5 g/s and the system current of 180 A. A strong vortex flow structure is found inside the torch due to the introduction of azimuthal velocity at the gas inlet, which should help to stabilize the rotating arc during the torch operation.     

Modeling pedestrian flow accounting for collision avoidance during evacuation

Collision avoidance behavior has become an open challenging problem since it is one of critical factors that influence the pedestrian flow dynamics. In this paper, a cellular automaton (CA) model is developed to depict the pedestrian movements when collision avoidance behaviors exist during evacuation. Then, we utilize the proposed model to simulate the influences of the collision avoidance on the pedestrian movements during the evacuation in a classroom with two exits. The numerical results indicate that more collision avoidance behaviors have negative influences on the evacuation efficiency, and that more competition behaviors generate more collisions while have no prominent positive impacts on the evacuation efficiency. Moreover, the evacuation time increases with the decreasing number of aisles in the classroom and the number of collisions increases with the increasing number of parts in the classroom divided by aisles. The above results are helpful to develop effective evacuation strategies and design the internal layouts of buildings.     

Modeling the consumer benefit in the optimal power flow

The addition of a model of the consumer into the traditional optimal power flow (OPF) algorithm that minimizes supplier costs is investigated. The development of such a model is based on the solution of the OPF using an objective function for maximization of social welfare. A traditional OPF algorithm can be modified to solve the social welfare maximization problem by including price-dependent load models. This modification to the traditional OPF is intuitive and very simple. This modified OPF formulation facilitates simulation of spot markets for both real and reactive power. The algorithm is effective on systems of hundreds of buses, but small examples to compare the results to the traditional OPF are also insightful. The impact of price-dependent loads on systems with transmission congestion, increased fuel costs, and voltage problems can be studied.     

Modeling adiabatic temperature rise during concrete hydration: A data mining approach

This paper presents a data mining approach for modeling the adiabatic temperature rise during concrete hydration. The model was developed based on experimental data obtained in the last thirty years for several mass concrete constructions in Brazil, including some of the hugest hydroelectric power plants in operation in the world. The input of the model is a variable data set corresponding to the binder physical and chemical properties and concrete mixture proportions. The output is a set of three parameters that determine a function which is capable to describe the adiabatic temperature rise during concrete hydration. The comparison between experimental data and modeling results shows the accuracy of the proposed approach and that data mining is a potential tool to predict thermal stresses in the design of massive concrete structures.     

新型空气质量流量传感器的建模与设计

热式质量流量传感器是在层流的条件下,通过加热电阻周围温度分布的变化来反映气体流量.本文通过在流道中设计内部小流道,把流速测试段的流态变为层流,并模拟了整个流场的的速度分布,在流速测试段得到比较理想的雷诺数Re≈12～110.在小流道测试段的流速与内燃机进气管的平均流速成一固定比例系数,因此,通过测试小流道内的流速可以获得内燃机的进气量.通过模拟分析得到了在恒温加热的条件下,不同流速下的温度分布,从而获得不同流速下,测试点的距离与温度差的关系曲线,并找出了相应测试点的测试范围,最终获得了温差最大值对应的测试距离为140～210 m.通过在加热电阻两端设计了两对测温电阻,得到叠加信号对应最大流速精度为0.02 m/s.     

Modeling of fluid flow in a tube with a moving indentation

The time-dependent flow in a tube with a moving indentation is numerically simulated using a dynamic mesh model. The model was used to simulate the flow in a tube with an indentation moving at different frequencies. The model was validated for a two-dimensional channel with a moving indentation. The results exhibited good agreement with the available experimental results. The results show that a single vortex was formed at a wall frequency of 0.1 Hz and was swept out of the tube at the end of the period. At a higher frequency of 1 Hz, vortex doubling occurred with reverse flow dominating downstream of the indentation. The results also show that the wall shear stress was larger for the higher frequency case of the moving indentation.     

Modeling temperature and species fluctuations in turbulent,reacting flow

Assumed Gaussian and β probability density functions (PDFs) for temperature are used with series expansions of the reaction-rate coefficients to compute the mean reaction-rate coefficients in a turbulent, reacting flow. The series-expansion/assumed PDF approach does not require any numerical integration, which substantially reduces computational cost with little loss of accuracy. An assumed multivariate β PDF for species is investigated for use in modeling the interaction of species fluctuations and chemical combustion. The multivariate β PDF is initially evaluated through a parametric study. Results of the parametric study indicate that species fluctuations can increase or decrease the magnitude of the species production term, depending on the type of reaction. The models are then tested on a two-dimensional high-speed turbulent reacting hydrogen-air mixing layer. For the conditions tested the numerical simulations indicate that the net effect of species fluctuations is to reduce the mean species production rate.     

Modeling fluid flow in fuel cells using the lattice-Boltzmann approach

Two flow problems relevant to fuel cell modeling are simulated with the lattice-Boltzmann (LB) approach. The first is a 3D viscous flow through a section of serpentine channel and the second is a 2D channel filled or partially filled with porous medium. In the first case, attention is given to the implementation details such as inlet–outlet boundary conditions, nonuniform grid, and forcing. It was shown that the flow pattern and pressure distribution depends sensitively on the flow Reynolds number as the flow Reynolds number is increased from 10 to 1000. There also appears to be some evidence that the transition to a turbulent flow occurs at Reynolds number on the order of 1000. In the second case, the effects of multiple time scales and interface between the porous medium and clear channel are considered. It was shown that, in order to obtain correct results at the interface or near the boundary, the physical time scales of the problem must be kept larger than the lattice time. This can be achieved by using a small particle velocity in the LB scheme.