A numerical model based on the System Dynamics was established to prospect the global environment in a time span of forthcoming 50 years. The model deals with global air temperature, CO2 concentration, forest stock and human society through the economic activity as the main variables. In the model, so-called CO2 emission right that will be introduced in near future in the diplomatic circle between developed and under developing counties is also considered. One of the features slightly differs from former analogous studies is providing all information at readers’ hand in our web-site that is requisite to consist the model, in short, a set of quoted, derived or assumed equations and basic data.
Tapered FRP tubes have high energy absorption performance under axial compressive load. FRP will be useful for structural material of a shock absorber in the various industries. And in order to evaluate the behavior of this material, several experimental tests and numerical simulations using FEM are carried out recently. However, it is difficult to simulate the crushing behavior of tapered FRP tubes, so called “Progressive Crushing” with FEM, because the crushing mechanism contains various kinds of fractures such as delamination, fiber fracture and so on. In this study, we proposed a special purpose FEM based on experimental data that is useful for the crush-worthiness analysis of FRP tube.
In the process of optimization with a large nonlinear dynamic analysis, a large amount of computational cost is required to obtain the optimal design. A large portion of this cost can be avoided using Response Surface Model (RSM) by approximating the more costly analysis. Therefore, various optimization problems with this cost were applied by this method. But, on the other hand, this method is not enough advantage for a cost of the process of design. Because, this cost is larger than the requirement time for improving design. We guess this time usually is about one week. Therefore our aim is to reduce a computational cost of the process of optimization to obtain the optimal design within one week. We propose a VCM (Variable Complexity Model) approach using both the simple model with RSM and complex model during the optimization procedure. In this paper, we applied our method to the optimization problem with a nonlinear dynamic crash analysis, and obtained good results.
In education support system research, the resources based on Web are the component databases, which are distributed by the education organizations. They are autonomous in management and heterogeneous in data model. The goal of our research is to provide the developers and uses with an integrated view and uniform interface of all the component databases. A composite 5-layer architecture including application, WWW server, event processing, driver interface and databases is presented. In addition, some key issues such as global data dictionary and uniform name service are discussed in this paper. The experiments show that the architecture and technology is feasible and practical.
For quasi-isotropic CFRP laminates, the elastic stress-strain behavior is expected to be the same in any directions. But fracture and/or strength of them may depend on the loading direction. In this paper, compressive tests are carried out for the specimens, cut out in several directions and lengths from two kinds of stacking sequence laminates, to investigate the influence of loading direction on the compressive strength. A FEM code is used to analyze the stresses in the specimens and the Tsai-Wu failure criterion is employed to predict the compressive strength of the laminates for the various loading directions and specimen lengths. The comparisons between the calculating results and experimental ones are discussed.
In this paper, an implicit elasto-plastic finite element analysis at finite strains based on a multiplicative decomposition of the deformation gradient is applied to solid/fluid coupling problem. A homogeneous compression tests for a hardening materials under plane strain condition show that the numerical results exhibit a quadratic rate of convergence and are insensitive to the mesh refinement and to the discrete time step. An inhomogeneous example under the compressive displacement exhibits a linear rate of convergence because of using an interpolation approximation of the pore pressure, however, the number of iteration is constant after some time steps. These solutions have a high accuracy in the sense that the equation of motion and continuity condition in the weak sense are satisfied at each model points within a given tolerance and the constitutive equations are satisfied with a high accuracy by the return mapping algorithm.
In the present study, a mechanism of fractal image of laminates on lamination parameters is discussed in detail, and a stacking sequence optimization method using the mechanism is proposed for complicated structures that include both of in-plane and out-of-plane lamination parameters. The new method employs branch and bound method for the optimizations of stacking sequences. For the estimation of the fractal branch of stacking sequences, the new method requires approximation of the objective function of the optimizations with quadratic polynomials using both in-plane and out-of-plane lamination parameters. The new method is applied to a stacking sequence optimization problem of a maximization of buckling load of a composite cylindrical shell structure. The method gives successfully optimal stacking sequences and validity was confirmed of this new method.
Usually, main parts of computer programs of structural calculation consist of complicated mathematical expressions, and generally speaking, these expressions are classified into two categories. One category represents relational expressions which are derived directly from physical laws, mathematical formulas and geometrical constraints, and the other category represents calculative expressions which are derived from numerical methods applied in the structural computation. The aim of this paper is to introduce a new tool in the object oriented programming for the purpose of making computer programs in structural calculation simple and easy to write. We introduce a new object class which represents an relational mathematical expression, and a new computational mechanism relating to the object class. One can assume that the relational expression holds throughout the program if one declares and makes the instances at the beginning of the program. By the use of the new tool of OOP in the structural calculation, one can separate relational expressions, which should be declared at the beginning of the program, and the other calculative expressions. As a result, one can make computer programs, whose main part consists of calculative expressions only, by assuming that the declared relational expressions hold throughout the program.
Adequate support radiuses and weight functions in a MLPG method, were verified first. It is mentioned that accurate solutions are obtained in a MLPG method when support radiuses are set so that the order of a basis vector used in approximating a displacement might agree with the number of overlapping sub-domains at an arbitrary position in a global domain. While, there is the case of being not able to make the order of a basis vector agree with the number of the overlapping sub-domains when symmetrical weight functions are used. In this case, the employment of unsymmetrical weight functions can make the order of a basis vector agree with the number of the overlapping sub-domains. Then static and dynamic analyses of bars were carried out in using the results of the above verification.
This paper describes a local contact search method using a multilayer neural network and its application to a smoothed contact surface with Gregory patches. Contact search process consists of two phases: a global search phase for finding the nearest node-segment pair and a local search phase for finding an exact local coordinate of the contact point within the segment. In the present method, the multilayer neural network is utilized for finding the local coordinate of the contact point in the local search phase. The fundamental formulation of the neuro-based local contact search method is described in detail, and its application to smoothed contact surfaces with Gregory patches, that can describe a smooth surface over an irregular mesh. Its basic performance is tested through sample analyses.
The purpose of this study is to develop a procedure for performing a dynamic analysis in the case that a multibody system in three dimensions moves along a nonlinear trajectory at variable velocity. The finite-element equations of motion were derived in the case that the multibody system undergoes large translational and rotational displacements in three dimensions. A computational code for time history response analysis of multibody systems was then developed. Time history responses on the model system comprised of two flexible links and a rigid body moving along a nonlinear trajectory were calculated using the derived computational codes.
In the previous paper regarding the numerical schemes for conservation of vorticity using Helmholtz element and for conservation of irrotational component, we have proposed a DNS for Leonard and Crosses terms in incompressible fluid. In the simulation, an implicit method has been used, dependent on the backward development scheme from time stage n+1 using Taylor series with terms of 4th order in time axis. All of time differentials in the Taylor series have been replaced with spatial differentials using Navier-Stokes equation, regarding in the appearance of 5th order multiple correlations. Thus this scheme is valid as a DNS for terms above. In this report, we tried to extend this scheme further with the help of Reynolds terms for the establishment of a DNS for Reynolds stresses. In the new scheme, we used an implicit method with terms of 2nd order in time axis for Reynolds stresses in the similar manner as described above. Accordingly, for the 2nd term, the transport equations of 3rd order multiple correlations of fluctuations and εij were required. Furthermore, in the 3rd order correlation of these transport equations, 4th order multiple correlations of fluctuations and others should be introduced. The main point in this report was that these values were calculated numerically by the direct use of the 4th order Taylor series as described.
In high-Reynolds number viscous aircraft flows, very fine and stretched grids are generally required to resolve accurately thin boundary layers developed along the body surface. An application of tetrahedral single unstructured grids has several difficulties in computational efficiency and solution accuracy and so a hybrid unstructured grid technique is incorporated into a CFD-based design system, CASPER. To validate the present code, we carried out hybrid unstructured Navier-Stokes computations of transonic and high Reynolds number flows around a typical transport aircraft, ONERA Model M5 configuration. With respect to wing surface pressure distributions, forces and moment coefficients and boundary layer transition lines, the present computed results are quantitatively compared with the other computed results and wind-tunnel testing data. Especially, the drag prediction is remarkably improved by the following three strategies: i) high resolution of chord surface grids around each leading edge, ii) extension of Shima’s Normalized Unstructured Mesh method, and iii) modification of transition parameters in Spalart-Allmaras one-equation turbulence model.
Japan atomic energy research institute (JAERI) is promoting to construct the liquid metal target as a neutron source of neutron scattering experiment facility. The liquid metal target is planned to receive MW class proton pulse beam and high-intensity spalletion reactions occur in the target generating neutorons. Under such condition, high density heat is released and consequently strong pressure wave is generated. The pressure wave propagates through mercury and reflects on the container of target made of hard stainless steel. On the other hand, in some experiments, the fact is shown that some pits type scratch is created on wall when strong pressure wave reflects on it. If the phenomenon happens in mercury target, it makes the life span of container shorter. Therefore, a coupled simulation study was carried out to reveal the process of the scratch generation.
In development of advanced aircraft at the next generation, high flight maneuverability is required according to magnifying an operating limitation. A close-coupled canard aircraft such as Eurofighter is proposed as an example of advanced aerodynamic configuration. Three-dimensional Reynolds-Averaged Navier-Stokes simulations are carried out for subsonic and transonic flows over the canard-wing-body-tail and the canard-wing-body configurations of the close-coupled canard aircraft by introducing hybrid unstructured grid technique together with Spalart-Allmaras one-equation turbulence model. With respect to surface pressure distributions and force and moment coefficients, the present computed results are quantitatively compared to the wind-tunnel testing data and the Euler computed results. The present computed results show good prediction in estimation of canard deflection effect on aerodynamic performance except pitching moment coefficient. It becomes clear that the present hybrid unstructured CFD solver is expected to be a powerful tool for aerodynamic design of advanced aircraft.
In numerical simulations of developing flows in space, the computational domain has to be truncated from the unbounded physical domain. When the finite difference method is used, the Sommerfeld radiation condition (SRC) is often used. However it is not clear which value of the convective velocity is appropriate for jets. We compare the four different convective velocities: the mean velocity over the exit boundary (SRC1), the arithmetic mean of the maximum and the minimum velocity at the exit boundary (SRC2), the local instantaneous velocity (SRC3) and the numerical velocity calculated from Orlanski’s formulation (SRC4). The test problems are flows which Lamb dipole moves in uniform flow. It is shown that SRC4 gives good results without reflection and deformation of the vortex.
When we construct three dimensional blood vessel modeling for numerical blood flow analysis, the extraction of coordinate data of contour on blood vessel region from two dimensional medical image obtained by medical equipments such as MRI, CT, ultrasonic echocardiography through manual image treatment demands many labour and times for researchers. To solve above mentioned problem, we developed an automatic shape extraction method using Snake for contour extraction and pattern recognition by Genetic Algorithm. We can attain to extract automatically the required contour data from medical image for blood vessel modeling on numerical flow analysis. We apply the abdominal aorta and renal artery modeling for numerical analysis of hemodynamics.
This paper presents a new evolutionary optimization method on dynamics of three-dimensional structures based on finite element modeling. An optimum structural design can be obtained from a simply small structure by allowing finite elements to be added as well as removed. The structural optimization method is developed using two kinds of sensitivity functions based on Rayleigh Quotient and strain energy. Especially, the authors take into consideration a problem of the mode-switching phenomenon that causes the convergence of the method to be difficult, and develop a way to solve the problem by a sensitivity function to consider the contribution rate of each natural mode. The method is examined using two 3 dimensional small structural models. The design objective of the examples is to shift the lowest natural frequency up to a target frequency.
We have proposed a CFD scheme using Helmholtz-element. This element, based on the Helmholtz’s theorem, satisfies the continuity condition for incompressible fluid as strong solution, and therefore, is of some advantages for CFD. However, it is difficult to apply voxel-element using the basis function to arbitrary boundary, since the element requires C1-continuity, and its velocity in rotation form of vector potential evidently has directional non-equality. A finite patch element has been proposed, in which the basic element expressed with basis function fa is further modified and reinforced with basis function of the patch element fb: fa + fb or fa×fb. In this study, we propose a boundary fitting technique in very simple form using the patch element.
Two methods for evaluating tapping inspection aptitude of retort sterilized can body, Air Injection Method and FE Simulation Method, were developed. Optimum can bottom shape was investigated by the Statistical Design Support System combined with the FE Simulation Method. Depth of annular bead and bottom curvature were found to be dominant for each characteristic value. Evaluation results of the characteristic values for these optimum shapes by the FE Simulation Method and the Air Injection Method indicated qualitative consistency with those expected by optimization, and showed the improvement of tapping inspection aptitude of retort sterilized can body, as expected.
Developing processes of flows in Taylor-Couette system between two cylinders are investigated by a three-dimensional numerical method. The length of cylinders is short and it is comparable with the gap width between cylinders. The inner cylinder suddenly begins to rotate, and the outer cylinder and end walls of cylinders are stationary. In fully developed flows, the normal two-cell mode, anomalous one-cell mode, twin-cell mode and time-dependent mode appear. A new method which estimates the variation of the circumferential velocity component is introduced to identify critical points where axisymmetric flows change to three-dimensional flows. The flows of the time-dependent mode are classified into four types. The types of the mode show their characteristic power spectrum and they appear at transient steps during the flow development leading to a chaotic state.
Analyses of natural convection are performed using an analytical model consisting of two concentric spheres. The parameters used in the calculation are Pr=0.71, 0.025 and Ra=100. · Results obtained for Pr=0.71, Ra=229,330 and Ra=749,760 are compared with results of visualization experiments carried out by Yin et al., and good agreement is confirmed. Mutual relationships among the coriolis force, lorentz force and temperature are discussed. For the analysis of an induction magnetic field, the B method is developed and analyzed using the two concentric spheres with analytical model. The results obtained are compared with those obtained by the φ method, and the efficacy of the B method is demonstrated.
We present a modification method of Lattice Boltzmann Method (LBM), which is named Multi-Components Expansion Method, which enables to simulate multi-components fluid with energy reservation. In process of multi-components interaction, this modification method is able to maintain density reservation of each components as well as total momentum and energy reservation of a system. An advantage of this method is a flexible application to most LBM models. There shows an example of Rayleigh-Tayler instability problem under gravity by binary-components LBM model based on single component LBM model and Multi-Components Expansion Method.
A multi-element airfoil flow shows inherently strong complexity for variations in angle of attack and slat and flap settings in high-lift systems. So far, several CFD code validations have been undertaken for high-lift flows. However, in spite of a great deal of efforts, even in two-dimensional computations, the current CFD codes fail to predict flow phenomena that govern high-lift aerodynamics with sufficient accuracy and efficiency. Currently, a two-dimensional compressible Navier-Stokes code with Spalart-Allmaras one-equation turbulence model and an unstructured multigrid method was developed and newly incorporated into a CFD-based design system of TRDI-JDA. For the code validation, the subsonic flows around two- and five-element airfoil configurations are computed. With respect to wing surface pressure coefficient distributions, boundary-layer velocity profiles and forces and moment coefficients, the present computed results are compared quantitatively with the wind-tunnel testing data. As a result, the present code is expected to be a powerful tool to predict and improve high-lift characteristics of multiple elements in aircraft design process.
As an educational materials, the basic principle of the quantum computer is considered by using a logic gate which is equivalent to square root of NOT. An unitary matrix which corresponds to √NOT gate is explicitly expressed in terms of the change of an isolated spin system. It is insisted that the consideration of the motion of the classical spin is more effective than that we expected in the basic study of quantum computer.
The finite cover method (FCM) is known as one of the generalized finite element methods and enjoys peculiar elements that partially have physical domains. We name them the generalized elements in this study and exmaine their performance within the framework of the finite element method (FEM). First, the elements with rectangular physical domain are studied by means of eigenvalues and eigenmodes of stiffness matrices. Secondly, the deformability of the elements with non-rectangular physical domain is also examined in comaprison with the corresponding FE solutions. Thirdly, assuming practical situations, in which sevral sizes of generalized elements are utilzed together, we report the cancellation errors in constructing global stiffness matrix when they have physical domans of significantly different order. Finally, after making the convergence study for the cook’s membrane problem and compiling all the results in this study, we conclude that the performance of generalized elements in the FCM are equivalent to or slightly superior to that of the FEM. It is to be noted that the studies also apply to the X-FEM and the GFEM.
The use of the ultrasound-imaging platform in medical facilities has significantly increased in recent years due to its superior capability, namely high resolution, less damage to the human body and so on. Though the doctors diagnose a tissue characterization of a liver by observing an image obtained by ultrasound, a diagnostic result seems to make a difference according to experience of doctors. Therefore a quantitative analysis method concerning ultrasonography is required. This paper proposes a CAD (Computer Aided Diagnosis) by an expert system, which has two mechanisms of estimation (Type I: inside roughness, Type II: edge angle). After the effectiveness of Type I and II are confirmed respectively, an estimation combined with two Types is applied to three kinds of condition of the liver, namely normal, chronic hepatitis and liver cirrhosis. As a result, three conditions are exactly recognized and our proposed system is suitable for estimating the tissue characterization of the liver.
In this paper, dynamic simulation study of the running performance of the AGT vehicle with the single-axle bogies are described to show the characteristics of the single-axle bogie in realistic situation. The multibody dynamics modeler, DADS, is used to build the dynamic model of AGT vehicle with single-axle bogies and this is used to demonstrate the vehicle motion in actual guideway. By using multibody dynamics model, a computer simulation in case of earthquake is carried out. The result obtained from the computer simulation show the motion of the vehicles in case of an earthquake was clarified.
Traveling salesman problems (TSPs) are well studied as combinatorial optimization problems. In this paper we propose a multiple heuristic search algorithm for solving the TSPs. Three kinds of TSP instances are used in our experiments: double concentric circle, fractal and random instances. The double concentric circle instances were set with tighter conditions compared with conventional experiments and the city numbers range from 48 to 14,400. Firstly, the algorithm was applied to the double concentric circle instances and it shows that the search ability of the proposed algorithm is robust with the increase of the city numbers in the double concentric circle instances. Furthermore, the algorithm was applied to the fractal and random instances. A considerable result was presented in fractal instances. The results of our experiment show that the proposed algorithm is extremely more effective for the double concentric circle and fractal instances which have the self-similarity than for the random instances.