• Smart Structures and Systems
• /
• v.15 no.3
• /
• pp.665-682
• /
• 2015

Structural identification or St-Id is 'the parametric correlation of structural response characteristics predicted by a mathematical model with analogous characteristics derived from experimental measurements'. This paper describes a St-Id exercise on Humber Bridge that adopted a novel two-stage approach to first calibrate and then validate a mathematical model. This model was then used to predict effects of wind and temperature loads on global static deformation that would be practically impossible to observe. The first stage of the process was an ambient vibration survey in 2008 that used operational modal analysis to estimate a set of modes classified as vertical, torsional or lateral. In the more recent second stage a finite element model (FEM) was developed with an appropriate level of refinement to provide a corresponding set of modal properties. A series of manual adjustments to modal parameters such as cable tension and bearing stiffness resulted in a FEM that produced excellent correspondence for vertical and torsional modes, along with correspondence for the lower frequency lateral modes. In the third stage traffic, wind and temperature data along with deformation measurements from a sparse structural health monitoring system installed in 2011 were compared with equivalent predictions from the partially validated FEM. The match of static response between FEM and SHM data proved good enough for the FEM to be used to predict the un-measurable global deformed shape of the bridge due to vehicle and temperature effects but the FEM had limited capability to reproduce static effects of wind. In addition the FEM was used to show internal forces due to a heavy vehicle to to estimate the worst-case bearing movements under extreme combinations of wind, traffic and temperature loads. The paper shows that in this case, but with limitations, such a two-stage FEM calibration/validation process can be an effective tool for performance prognosis.

• Journal of Biosystems Engineering
• /
• v.29 no.6 s.107
• /
• pp.495-500
• /
• 2004

This study was performed to develop thin layer drying equations for low temperature. Thin layer drying tests of short grain rough rice were conducted at three low temperature levels of 15, 25, $35^{\circ}C$ and two relative humidity levels of 30, $50\%$, respectively. The measured moisture ratios were fitted to the selected four drying models (Page, Thompson, Simplified diffusion and Lewis model) using stepwise multiple regression analysis. The overall drying rate increased as the drying air temperature was increased and as relative humidity was decreased, but the effect of temperature increase was dominant. Half response time (Moisture ratio=0.5) of drying was affected by both drying temperature and relative humidity at drying temperature of below $25^{\circ}C$, but at $35^{\circ}C$ was mainly affected by drying temperature. The results of comparing coefficients of determination and root mean square error of moisture ratio for low drying models showed that Page model was found to fit adequately to all drying test data.

• Coupled systems mechanics
• /
• v.11 no.2
• /
• pp.107-119
• /
• 2022

The aim of the work presented in this paper is development of numerical model for prediction of temperature distribution in pavement according to the measured meteorological parameters, with introduction of non-linear heat transfer coefficient which is a function of temerature difference between the air and the pavement. Developed model calculates heat radiated from the pavement back in the air, which is an important part of the heat trasfer process in the open air surfaces. Temperature of the pavement surface, heat radiation together with many meteorological parameters were measured in series during two years in order to validate the model and calibrate model parameters. Special finite element method for temperature heat transfer towards the soil together with the time integration scheme are used to solve the governing equation. It is proved that non-linear heat transfer coefficient, which is a function of time and temperature difference between the air and the pavement, is required to decribe this phenomena. Proposed model includes heat tranfer coefficient callibration for specific climate region, through the iterative inverse procedure.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
• /
• v.1 no.1
• /
• pp.1-8
• /
• 2005

Aquifer Thermal Energy Storage (ATES) can be a cost-effective and renewable geothermal energy source, depending on site-specific and thermohydraulic conditions. To design an effective ATES system having the effect of groundwater movement, understanding of thermohydraulic processes is necessary. The heat transfer phenomena for an aquifer heat storage are simulated by using FEFLOW with the scenario of heat pump operation with pumping and waste water reinjection in a two layered confined aquifer model. Temperature distribution of the aquifer model is generated, and hydraulic heads and temperature variations are monitored at the both wells during 365 days. The average groundwater velocities are determined with two hydraulic gradient sets according to boundary conditions, and the effect of groundwater flow are shown at the generated thermal distributions of three different depth slices. The generated temperature contour lines at the hydraulic gradient of 0.001 are shaped circular, and the center is moved less than 5 m to the direction of groundwater flow in 365 days simulation period. However at the hydraulic gradient of 0.01, the contour center of the temperature are moved to the end of east boundary at each slice and the largest movement is at bottom slice. By the analysis of thermal interference data between two wells the efficiency of the heat pump system model is validated, and the variation of heads is monitored at injection, pumping and no operation mode.

• Structural Engineering and Mechanics
• /
• v.66 no.1
• /
• pp.85-96
• /
• 2018

This study investigates the response of functionally graded (FG) gas pipe under unsteady internal pressure and temperature. The pipe is proposed to be manufactured from FGMs rather than custom carbon steel, to reduce the erosion, corrosion, pressure surge and temperature variation effects caused by conveying of gases. The distribution of material graduations are obeying power and sigmoidal functions varying with the pipe thickness. The sigmoidal distribution is proposed for the 1st time in analysis of FG pipe structure. A Two-dimensional (2D) plane strain problem is proposed to model the pipe cross-section. The Fourier law is applied to describe the heat flux and temperature variation through the pipe thickness. The time variation of internal pressure is described by using exponential-harmonic function. The proposed problem is solved numerically by a two-dimensional (2D) plane strain finite element ABAQUS software. Nine-node isoparametric element is selected. The proposed model is verified with published results. The effects of material graduation, material function, temperature and internal pressures on the response of FG gas pipe are investigated. The coupled temperature and displacement FEM solution is used to find a solution for the stress displacement and temperature fields simultaneously because the thermal and mechanical solutions affected greatly by each other. The obtained results present the applicability of alternative FGM materials rather than classical A106Gr.B steel. According to proposed model and numerical results, the FGM pipe is more effective in natural gas application, especially in eliminating the corrosion, erosion and reduction of stresses.

• Proceedings of the ESK Conference
• /
• 1998.04a
• /
• pp.188-193
• /
• 1998

The purpose of the study is to develop a numerical model based on experimental data to estimate the thermal comfort in the driving room of a motorcar. For the ecperiments, three air temperature level of 21, 23, 25 .deg. C are set to measure variable such as average skin temperature, R-R interval, the comfort sensation, and the performance level. By performing statistical analysis with the results obtainted, it is observed that two physiological factors-average skin temperature and R-R interval have significant relation with the thermal comfort in the driving room. Thus, those two factors are included as parameters in the proposed model to estimate the thermal comfort.

• Progress in Superconductivity and Cryogenics
• /
• v.4 no.1
• /
• pp.50-54
• /
• 2002

Penetration depth of Nb electrodes in $Nb/A1O_x/Nb$ Josephson junctions has been measured by resistive method. For a given applied field, the total flux through the junction is temperature dependent because the penetration depth of Nb electrode varies with temperature. If the total flux equals an integral multiple of the flux quantum at certain temperatures, resistive peaks appear at those temperatures. The penetration depth of Nb can be determined by applying the above condition, The temperature dependence of penetration depth was found to be well described by the two-fluid model.

• Bulletin of the Korean Chemical Society
• /
• v.8 no.2
• /
• pp.73-79
• /
• 1987

In this work we have investigated temperature dependence of spin-rotational relaxation rate, $(1/T_1)_{SR}$, of methyl carbon-13's in 2-bromo-p-xylene, 2,5-dimethylaniline, and 2,5-dimethylanisole and have found that temperature behaviors of two methyl carbon-13's in ortho- and meta-position, respectively, are substantially different. It has been confirmed that the modified Burke-Chan model proposed by Park et al. can nicely explain different temperature dependence of $(1/T_1)_{SR}$ for these two methyl carbon-13's while the original Burke-Chan model fails to do so.

• Proceedings of the KSRS Conference
• /
• 2005.10a
• /
• pp.47-51
• /
• 2005

Using satellite images, an optimal solution to water motion has been presented in this study. Since temperature patterns are suitable tracers in water motion, Sea Surface Temperature (SST) images of Caspian Sea taken by MODIS sensor on board Terra satellite have been used in this study. Two daily SST images with 24 hours time interval are used as input data. Computation of templates correspondence between pairs of images is crucial within motion algorithms using non-rigid body objects. Image matching methods have been applied to estimate water body motion within the two SST images. The least squares matching technique, as a flexible technique for most data matching problems, offers an optimal spatial solution for the motion estimation. The algorithm allows for simultaneous local radiometric correction and local geometrical image orientation estimation. Actually, the correspondence between the two image templates is modeled both geometrically and radiometrically. Geometric component of the model includes six geometric transformation parameters and radiometric component of the model includes two radiometric transformation parameters. Using the algorithm, the parameters are automatically corrected, optimized and assessed iteratively by the least squares algorithm. The method used in this study, has presented more efficient and robust solution compared to the traditional motion estimation schemes.

• 한국연소학회:학술대회논문집
• /
• 2002.11a
• /
• pp.173-184
• /
• 2002

In order to evaluate the devolatilization models of pulverized coal, various devolatilization models are examined for the numerical analysis of Drop Tube Furnace.The results of analysis are compared with the experimental results. A numerical study was conducted to explore the sensitivities of the predictions to variation of the model parameters. It helps to elucidate the source of the discrepancies. Three different wall temperature conditions of the DTF, 1100, 1300 and $1500^{\circ}C$ were considered in this analysis. Two fuels are U.S.A. Alaska coal and Australia Drayton coal. The results of analysis with constant rate model, single kinetic rate model and two competing rate modes well presented fast volatile matter release in the early devolatilization. However, in the latter devolatilization they did not coincide with experimental results which presented tardy volatile matter release on account of pyrolysis of high molecular substance. On the other hand, the results of analysis with DAEM(Distribute Activation Energy Model) coincided with experiment al results in overall devolatilization.