• Advances in Computational Design
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• v.2 no.3
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• pp.225-240
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• 2017

This paper presents the application of multiple linear regression (MLR) and artificial neural network (ANN) techniques for developing the models to predict the unconfined compressive strength (UCS) and Brazilian tensile strength (BTS) of the fiber reinforced cement stabilized fly ash mixes. UCS and BTS is a highly nonlinear function of its constituents, thereby, making its modeling and prediction a difficult task. To establish relationship between the independent and dependent variables, a computational technique like ANN is employed which provides an efficient and easy approach to model the complex and nonlinear relationship. The data generated in the laboratory through systematic experimental programme for evaluating UCS and BTS of fiber reinforced cement fly ash mixes with respect to 7, 14 and 28 days' curing is used for development of the MLR and ANN model. The data used in the models is arranged in the format of four input parameters that cover the contents of cement and fibers along with maximum dry density (MDD) and optimum moisture contents (OMC), respectively and one dependent variable as unconfined compressive as well as Brazilian tensile strength. ANN models are trained and tested for various combinations of input and output data sets. Performance of networks is checked with the statistical error criteria of correlation coefficient (R), mean square error (MSE) and mean absolute error (MAE). It is observed that the ANN model predicts both, the unconfined compressive and Brazilian tensile, strength quite well in the form of R, RMSE and MAE. This study shows that as an alternative to classical modeling techniques, ANN approach can be used accurately for predicting the unconfined compressive strength and Brazilian tensile strength of fiber reinforced cement stabilized fly ash mixes.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2270-2273
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• 2003

Fuzzy logic control has been widely implemented in air conditioning and ventilation systems which has uncertainty or high robust system. Since the dynamic behaviors of the systems contain complexity and uncertainty in its parameters , several fuzzy logic controllers had been implemented to control room temperature in the field of air conditioning system. In this paper, the fuzzy logic control has been developed to control room temperature and humidity in the precision air conditioning systems. The nonlinear mathematical model was formulated using energy and continuity equations. MATLAB was used to simulate the fuzzy logic control of the multi-variable air conditioning systems. The simulation results show that fuzzy logic controller can reduce the steady-state errors of the room temperature and relative humidity in multivariable air conditioning systems. The offset are less than 0.5 degree Celsius and 3 percent in relative humidity respectively under random step disturbance in heating load and moisture load respectively

• Journal of Environmental Science International
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• v.17 no.8
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• pp.891-898
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• 2008

This study was conducted to develop the effects of site environmental factors on estimation of site index function for Chamaecyparis obtusa Endlicher stands. We derived nonlinear growth equation and the draw site index curves by applying this estimated equation. This study with Chapman-Richards function showed significant P-value which was less then 0.0001 and $R^2$ value 0.5947. This study was conducted to develop the feasible site index equation of Chamaecyparis obtusa Endlicher. For the table, the data of 82 sample areas that were thought to be without errors among the data of Chamaecyparis obtusa Endlicher sample area located on the value-oriented forest location chart were used and estimated. After analyzing the quantification method I based on 13 environmental factors to develop the score table for the site-index estimation of Chamaecyparis obtusa Endlicher, $R^2$ value of the model was 0.7555. It has been analyzed that the scope value of Soil moisture in horizon A was 7.5045, that of total soil depth was 6.3896, that of topography was 5.3471, that of slope was 4.7000 and that of aspect was 3.2038. After analyzing the partial correlation to examine the factors that affected most the site-index of Chamaecyparis obtusa Endlicher, it has been noted that the partial correlation of climatic zone was 0.4987, which was highest, and it was followed by Soil moisture in horizon A (0.4592), slope (0.4537), topography (0.3299) and total soil depth (0.1035). As a result of conducting the significance test for partial correlation, it has been found that topography, climatic zone, parent rock, slope, altitude, aspect, Soil moisture in horizon A, soil hardness in horizon A and total soil depth were recognized significant with 1% of significance level and sedimentary type and soil texture in horizon A were recognized significant with 5% of significance level.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.1D
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• pp.73-82
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• 2011

Generally, an unsaturated condition was not considered to predict the long-term strength and drainage behaviors on compacted road foundations. However, it is logical way to consider the unsaturated condition and hysteresis behavior on road foundations like subbase and subgrade. For more quantitative analysis, rational experimental approach requires proper laboratory tool and material model, and hydraulic properties of pavement geomaterials under unsaturated conditions. In this study, therefore, laboratory data from the soil-water characteristic curve tests were used to predict suction and unsaturated permeability on pavement foundations and the results were analyzed based on the nonlinear fitting model considered. In addition to that, the unsaturated moisture capacity of each material is discussed.

• Steel and Composite Structures
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• v.34 no.4
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• pp.511-524
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• 2020

In this research, a simple four-variable trigonometric integral shear deformation model is proposed for the static behavior of advanced functionally graded (AFG) ceramic-metal plates supported by a two-parameter elastic foundation and subjected to a nonlinear hygro-thermo-mechanical load. The elastic properties, including both the thermal expansion and moisture coefficients of the plate, are also supposed to be varied within thickness direction by following a power law distribution in terms of volume fractions of the components of the material. The interest of the current theory is seen in its kinematics that use only four independent unknowns, while first-order plate theory and other higher-order plate theories require at least five unknowns. The "in-plane displacement field" of the proposed theory utilizes cosine functions in terms of thickness coordinates to calculate out-of-plane shear deformations. The vertical displacement includes flexural and shear components. The elastic foundation is introduced in mathematical modeling as a two-parameter Winkler-Pasternak foundation. The virtual displacement principle is applied to obtain the basic equations and a Navier solution technique is used to determine an analytical solution. The numerical results predicted by the proposed formulation are compared with results already published in the literature to demonstrate the accuracy and efficiency of the proposed theory. The influences of "moisture concentration", temperature, stiffness of foundation, shear deformation, geometric ratios and volume fraction variation on the mechanical behavior of AFG plates are examined and discussed in detail.

• Journal of Korea Water Resources Association
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• v.33 no.3
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• pp.375-382
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• 2000

The surface hydrology of large watershed is susceptible to several preferred stable states with transitions between stable states induced by stochastic fluctuations. This comes about due to the close coupling of land surface and atmospheric interaction. An interesting and important issue is the duration of residence in each mode. In this study, mean transition tunes between the stable modes are analyzed for the Han River Basin. On the basis of historical data, the nonlinear water balance model is calibrated for the Han River Basin. The transition times between the stable modes in the model are studied based on the stochastic representation of the physical processes and on the calibrated model parameters. This study has implications for prediction of the transition time between stable modes or residence times, that is, the time the system spends in a given stable modes, since this would be equivalent to predicting the duration of drought or wet conditions.

• Geotechnical Engineering
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• v.4 no.2
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• pp.33-44
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• 1988

The Taechong Dam completed in 1980 is a composite dam at which a junction was formed partly by butting the core against the end face of the concrete gravity section and partly by the core overlapping the upstream face of the concrete. In order to evaluate the performance of the junction, the interfaces between the concrete dam and core of the embankment dam were well instrumented with total pressure cells and piezometers. A nonlinear incremental finite element analysis simulating its construction behaviour was carried out under plane strain conditions. Material parameters for the core are determined from triaxial tests on the specimens, sampled in the quarry site and compacted to the field dry density at the field moisture content. Material parameters for the filter, transition materials and the rockfill are estimated from literature. When compared with the earth pressures measured at the interfaces, the analytical results show good agreement in the core, however, there are some discrepancy in the shell. A nonlinear model for pore pressure response is used successfully to predict the pore pressures at the interface in the core.

• Water for future
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• v.27 no.3
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• pp.45-54
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• 1994

Basic theory of fractal dimension is introduced and performed for the generated time series using the water balance model. The water balance equation over a large area is analyzed at seasonal time scales. In the generation and modification of mesoscale circulation local recycling of precipitation and dynamic effects of soil moisture are explicitly included. Time delay is incorporated in the analysis. Depending on the parameter values, the system showed different senarios in the evolution such as fixed point, limit cycle, and chaotic types of behavior. The stochastic behavior of the generated time series is due to deterministic chaos which arises from a nonlinear dynamic system with a limited number of equations whose trajectories are highly sensitive to initial conditions. The presence of noise arose from the characterization of the incoming precipitation, destroys the organized structure of the attractor. The existence of the attractor although noise is present is very important to the short-term prediction of the evolution. The implications of this nonlinear dynamics are important for the interpretation and modeling of hydrologic records and phenomena.

• Journal of the Korean Society of Safety
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• v.11 no.4
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• pp.143-150
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• 1996

This is an explicit-Implicit, finite element analysis for linear as well as nonlinear hygrothermal stress problems. Additional features, such as moisture diffusion equation, crack element and virtual crack extension(VCE ) method for evaluating J-integral are implemented in this program. The Linear Elastic Fracture Mechanics(LEFM) Theory is employed to estimate the crack driving force under the transient condition for and existing crack. Pores in materials are assumed to be saturated with moisture in the liquid form at the room temperature, which may vaporize as the temperature increases. The vaporization effects on the crack driving force are also studied. The Ideal gas equation is employed to estimate the thermodynamic pressure due to vaporization at each time step after solving basic nodal values. A set of field equations governing the time dependent response of porous media are derived from balance laws based on the mixture theory Darcy's law Is assumed for the fluid flow through the porous media. Perzyna's viscoplastic model incorporating the Von-Mises yield criterion are implemented. The Green-Naghdi stress rate is used for the invariant of stress tensor under superposed rigid body motion. Isotropic elements are used for the spatial discretization and an iterative scheme based on the full newton-Raphson method is used for solving the nonlinear governing equations.

• Computers and Concrete
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• v.20 no.2
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• pp.119-127
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• 2017

Time-dependent buckling of embedded straight concrete columns armed with Silicon dioxide($SiO_2$) nano-particles exposed to fire is investigated in the present study for the fire time. The column is simulated mathematically with Timoshenko beam model. The governing mass conservation equations to describe heat and moisture transport in concrete containing free water, water vapor, and dry air in conjunction with the conversion of energy are considered. The characteristics of the equivalent composite are determined using Mori-Tanaka approach. The foundation around the column is simulated with spring and shear layer. Employing nonlinear strains-displacements, energy methods and Hamilton's principal, the governing equations are derived. Differential quadrature method (DQM) is used in order to obtain the critical buckling load and critical buckling time of structure. The influences of volume percent of $SiO_2nano-particles$, geometrical parameters, elastic foundation and concrete porosity are investigated on the time-dependent buckling behaviours of structure. Numerical results indicate that reinforcing the concrete column with $SiO_2nano-particles$, the structure becomes stiffer and the critical buckling load and time increase.