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An unsteady flow and heat transfer problem with viscous dissipation of a third order fluid placed within two long parallel flat porous walls is studied in present work. The governing equations are non- dimensionalized and finally a non-linear coupled system of partial differential equation is obtained. An approximated solution is obtained using finite difference method of fully implicit form. With help of high speed MATLAB programming numerical solution is procured and presented graphically. Investigation is made on effect of different physical parameters on flow and heat profile. The notable finding in the current work is that for smaller values of visco-elastic parameter ®, the velocity rises with raising the values of ®. But for larger visco-elastic parametric values of ®, a reversed effect is seen on velocity field. Also with the increase of viscous-dissipation parameter, more viscous-dissipation heat generated that increases the temperature field.

An improved technique of resin delivery, called double-bag progressive compression method (DBPCM), has been developed to manufacture composite parts associated with the vacuum infusion (VI) process...

Both cryosurgery and radiofrequency ablation (RFA) for solid liver tumor treatment are available as minimally invasive procedures that induce changes to the tumor’s thermal environment in order to destroy cancer cells. However, one of the critical factors that impedes cryosurgery and RFA’s successful outcomes is the relatively high recurrence rate caused by the inability to ablate a large damaged tissue zone that envelopes targeted tumors, resulting in therapy failure. To overcome these challenges, a hybrid cryo-RFA system under thermal stress control is proposed in this study. A three-dimensional finite difference analysis is employed to simulate the combined cryosurgery and RF heating protocol. Based on the data acquired from measured experiments, the simulated results derived have demonstrated close agreement with experimental data, with a maximum deviation of 4.8%. We investigated the impacts of varying cryoprobe’s holding temperature and cooling rates on tissue damage. Results have revealed that the tissue damage region is enhanced by properly increasing the cryoprobe’s cooling rate, but the increase of cryoprobe’s cooling rate cannot enlarges the tissue damage area without limit in the freezing process. In addition, the employment of a hybrid cryo-RFA system markedly promotes the destruction of cancer tissue in contrast to conventional stand-alone RF heating or cryosurgery.

Geofoam is one of the geosynthetic products that can be used in geotechnical applications. According to researches, expanded polystyrene (EPS) geofoam placed directly against a rigid retaining wall has been proposed as a strategy to reduce static loads on the wall. This study employed a finite difference analysis using a 2-D FLAC computer program by considering yielding and nonyielding states for retaining walls to explore the effectiveness of geofoam panels in improving the static performance of cantilever retaining walls. Retaining walls at heights of 3, 6, and 9 meters and geofoam panels with densities of 15, 20, and 25 (kg/m3) at three relative thicknesses of t/H = 0.05, 0.2, and 0.4 were modelled in this numerical study. In addition, the performance of the double EPS buffer system, which involves two vertical geofoam panels, in retaining walls’ stability with four panel spacing (50, 100, 150, and 200 cm) was also evaluated in this research. The results showed that use of EPS15 with density equal to 15 (kg/m3) which has the lowest density among other geofoam panels has a significant role in reduction of lateral stresses, although the performance of geofoam in nonyielding retaining walls is better than yielding retaining walls.

Radiofrequency ablation (RFA) for liver tumors is a minimally invasive procedure that uses electrical energy and heat to destroy cancer cells. One of the critical factors that impedes its successful outcome is the thermal heat sink effects from complex vascular systems that give rise to incomplete destruction of the target tumor tissue, resulting in therapy failure. To better understand the thermal influence of the complex vascular system during RFA, this work proposes the employment of two 3D fractal tree-like branched networks to investigate which key factors of the tree-like vascular system impact heating process. A three-dimensional finite difference analysis is employed to simulate the RFA treatment. Based on the data acquired from the measured experiments, the simulated results derived from combining the Pennes bioheat model and the boundary condition-enforced immersed boundary method (IBM) have demonstrated close agreement with experimental data with a maximum discrepancy of ±8.3%. We employed the orthogonal design approach to analyze 3 factors, namely, the blood vessel's volume, the average distance between probe center and the blood vessel system and the number of the selected part's branches at three different levels. Results have revealed that the distance between RFA probe and blood vessel plays a major role during the heating process compared with the other two factors. In addition, both the ablating rates and the volume of damaged tissue are slightly reduced with increasing number of blood vessel branches.

Radiofrequency ablation (RFA) for liver tumors is a minimally invasive procedure that uses electrical energy and heat to destroy cancer cells. One of the critical factors that impedes its successful outcome is the use of inappropriate radiofrequency levels that will not completely destroy the target tumor tissues, resulting in therapy failure. Additionally, the surrounding healthy tissues may suffer from serious damage due to excessive ablation. To address these challenges, this work proposes the employment of injected nanoparticles to thermally promote the ablation efficacy of conventional RFA. A three-dimensional finite difference analysis is employed to simulate the RFA treatment. Based on the data acquired from measured experiments, the simulation results have demonstrated close agreement with experimental data with a maximum discrepancy of within ±8.7%. Several types of nanoparticles were selected to evaluate their influences on liver tissue's thermal and electrical properties. We analysed the effects of nanoparticles on liver RFA via a tumor rending process incorporating several clinically-extracted tumor profiles and vascular systems. Simulations were conducted to explore the temperature difference responses between conventional RFA treatment and one with the inclusion of assisted nanoparticles on several irregularly-shaped tumors. Results have indicated that applying selected nanoparticles with high thermal conductivity and electrical conductivity on the targeted tissue zone promotes heating rate while sustaining a similar ablation zone that experiences lower maximum temperature when compared with the conventional RFA treatment. In sum, incorporating thermally-enhancing nanoparticles promotes heat transfer during the RFA treatment, resulting in improved ablation efficiency.

The performances of 2 K Joule–Thomson (J-T) heat exchanger are related to the operation efficiency and economy of the superfluid helium cryogenic system, and the helically finned-tube heat exchanger (HFHE) is designed and tested. Heat transfer characteristics of the HFHE are investigated by a finite difference analysis method, and the design optimization of the HFHE is performed by the orthogonal test and variance analysis method. Meanwhile, the influences of the geometrical parameters on the performances are discussed. The experimental investigation of the HFHE is carried out in the superfluid helium cryogenic system, and the performances of the HFHE are verified experimentally. The results are shown that the calculated performances of the HFHE cause by heat transfer are in reasonable agreement with the experimental results, which indicates that the thermal calculation model of the HFHE is more accurate. Moreover, the deviations of pressure drop of cold fluid between the calculation and measurement are analyzed and the friction factor is modified in this paper.

Resistive sintering is a new method which enables the production of different material types by using mechanical load and electric current. For the required process performance, it is necessary to set the parameters such as current, voltage, dissipated power, electric energy, and production time correctly. The container is an important component of the resistive sintering system. Container electrical resistance is a value that is difficult to calculate in terms of the geometry of the build and to measure due to the smallness of the value. In this study, assuming that the container temperature is constant, the Laplace equation of the electric potential is solved in the cylindrical coordinates considering the axial symmetry by the finite difference method and then the electrical current and resistance of the sintering container was calculated by post-processing of the solved electric potential using Ohm's law in vector form. The volumetric power density is used to calculate the dissipated power in the container and the container current is calculated on the stiff area. It is seen that the current density is almost doubled at the stiff-container edges and the power density at these points reaches its maximum. At points distant from the stiffs, the electrical potential is almost constant and the potential difference is negligible. The main source of heating is shown to be the resistance of the stiffs. The resistance of the structure is found to be about 70 mu Omega. This method given here can be used in more sophisticated models to size an ECAS system.

In this paper, the ultimate bearing capacity of two closely spaced rigid strip footings with rough base on granular soil is examined based on enhanced limit equilibrium, plastic limit analy...

Over the past several decades, iconic and public buildings have become targets of terrorist bomb attacks, but most of these buildings were built without consideration of blast loading scenarios. Key load-carrying elements such as concrete columns are probably the most critical structural components for structural protection against bomb threats. Failures of columns may trigger catastrophic progressive collapse if there is insufficient structural redundancy. In this chapter, field blast tests on columns made of ultra-high performance concrete (UHPC) material that developed in Chapter 2, Development, testing, and numerical simulation of ultra-high performance concrete at material level, are presented. Test results showed that UHPC columns had excellent blast-resistant capability, only small mid-height deflection and minor concrete damage was observed after the blasting tests. Meanwhile, to quantify blast-induced damage and assess residual loading capacity of UHPC columns, static axial loading tests on postblast UHPC columns were carried out. Undamaged control samples were tested to provide benchmarks. Damage index and residual loading capacity of UHPC columns after various blast loadings were obtained. It was found that column cast with microsteel fiber-reinforced UHPC preserved more than 70% of its loading capacity after 35 kg TNT detonation at 1.5 m standoff distance, while high-strength concrete column only maintained 40% loading capacity after 8 kg TNT detonation at 1.5 m standoff distance. Finite element analysis and finite difference analysis are also conducted to reproduce the column response under these blast loads and yield damage evaluation curves for UHPC columns.

A finite difference analysis was performed to investigate the behavior of one-way reinforced concrete slabs exposed to fire. The objective of the study was to investigate the fire resistance and the fire risk after extinguishing the fire. Firstly, the fire resistance was obtained using the ISO834 standard fire without cooling phase. Secondly, the ISO834 parametric fire with cooling phase was applied to study the effect of cooling time. Accordingly, the critical time for cooling was identified and the corresponding failure time was calculated. Moreover, the maximum risk time which is the time between the fire extinguishing and the collapse of slab was obtained. Sixteen one-way reinforced concrete slabs were considered to study the effect of important parameters namely: the concrete cover thickness; the plaster; and the live load ratio. Equations for heat transfer through the slab thickness were used in the fire resistance calculations. Studying the cooling time revealed that the slabs are still prone to collapse although they were cooled before their fire resistance. Moreover, increasing the concrete cover thickness and the presence of plaster led to an increase in the maximum risk time. However, the variation in the live load ratio has almost no effect on such time.

Infrared Thermography is one of the advanced NDE methods that is becoming attractive due to its ability to inspect non invasively large areas in short times and provide full field images in a non contact nature. While initially the method started as a qualitative technique for defect detection alone, with the advent of lock in and pulsed techniques, quantitative defect detection was made possible. While these techniques have been applied in case of ceramics and composites for defect quantification, defect sizing and quantification using these methods have not been systematically attempted in case of stainless steels. A systematic study has been undertaken to evaluate the accuracy of these empirical Pulsed Thermography (PT) techniques for defect size and depth estimation in type 316 L austenitic stainless steels. Theoretical modelling based on finite difference analysis using Thermo Calc 6L software has also been done and the results compared.

Chloride diffusuion is regarded as the dominant chloride transport process in concrete and the main cause of the corrosion of steel in concrete structures exposed to chloride-rich environments. Surface biodeposition can be applied to both new and existing concrete structures to restrain this deterioration. To gain comprehensive overview to the protective mechanism of surface biodeposition, a theoretical study of chloride diffusion through surface-biodeposited concrete is required. This paper proposes a physical model for surface biodeposited concrete, and develops a theoretical model to predict chloride diffusion of surface-biodeposited concrete structures. The model describes movement and retention of moisture and chloride by means of balance equations and diffusion laws. The influences of biodeposition and substrate properties on chloride diffusion are studied by a finite difference model. Results indicate that chloride diffusion is controlled by both the biodeposition and the substrate.

In this paper, the vacancy migration in Cu interconnect of large scale integration caused by stress induced voiding was calculated using the α multiplication method. Then, the effect of weight coefficient, α, on stress induced vacancy diffusion analysis was investigated and the validity of the α multiplication method was verified. Furthermore, the method of the vacancy diffusion analysis coupled with thermal stress analysis which can consider the history of thermal stress due to temperature changes was proposed. The results of the vacancy diffusion analysis coupled with the thermal stress analysis were compared with the analytical results of the vacancy migration without the effect of history of thermal stress. As a result, the maximum site of vacancy accumulation was found to be qualitatively in good agreement between them. However, the quantitative value of maximum vacancy concentration obtained by the vacancy diffusion analysis coupled with thermal stress analysis was found to be much higher and the vacancy distribution is found to be much more localized.

It was presented for the results of 3D finite difference analysis on the behavior of single pile in clay. Firstly, it was discussed to the effect of model’s mesh fineness and soil parameters on pile response. And it was founded that the mesh size less than 0.2d (diameter of pile) was reasonable. In additions, when the soil was soft or the E(soil elastic modulus) was small, the effect E of on lateral capacity of pile was larger than the soil was stiff clay with soil elastic modulus increasing. Lastly, the results of the numerical simulation carried out in this study were compared with a published field lateral loading tests, a good correlation between the field test and the numerical simulation was obtained based on reasonable mesh size and material parameters.

The objective of this research was to develop and validate a more accurate method to analyze and calculate the inactivation of Listeria monocytogenes in frankfurter packages during postlethality hot water immersion heating and the subsequent cooling processes. Finite difference analysis with implicit scheme was used to simulate the heat transfer process during in-package pasteurization of frankfurters. A volumetrically distributed simulation method was developed to calculate the lethality of the thermal treatment. The simulation method was validated using frankfurter packages inoculated with a 4-strain cocktail of L. monocytogenes. Experimental results showed that the numerical analysis model could accurately simulate the heat transfer process during heating and cooling of frankfurter packages. The simulated temperatures on the surface or in the middle of the package matched very closely with the experimental observations. Using the simulated temperature distribution in the packages, the integrated lethality simulation method, based on the volumetric distribution of bacteria, could accurately predict the reduction in the bacterial counts. The calculation results were on average within 0.3 log(CFU/g) difference from the experimental observations, while the General Method systematically underestimated the bacterial reductions by approximately 0.9 log(CFU/g). The study shows that the integrated lethality method is more accurate than the General Method in calculating the lethality of thermal processes for conduction-heated foods.

Curing characteristics of thick composite parts have long been known to be a function of thickness and location within the parts. While cure state as a function of thickness has often been modeled, actual experimental verification has been difficult. In this work, disposable and permanently mounted dielectric sensors were used to characterize the cure in polyester sheet molding compound at various locations through the thickness of the part in a simulated molding environment. Using established tech niques, the dielectric and temperature information were combined to yield local cure state information for each sensor. Parts under five millimeters thick were found to cure rather uniformly, while parts greater than this had increasing degrees of nonuniformity in cure behavior through the thickness. Cure time differences of up to three minutes, between center and edge, were observed in parts 20 millimeters thick. These observed cure state data are compared to finite difference model predictions. The model simulations show that in thick parts, a cure "wave" develops, starting at the SMC/mold interface and proceeds toward the center of the part. The "wave" increases in velocity as it moves toward the center of the part. The overall effect is that a relatively uniform cure rate is observed at the SMC/mold interface while in the middle of the SMC part, a long induction period occurs, followed by an extremely fast cure. The model predictions, which are confirmed by the sensor cure data, may be used to predict the behavior and molding cycle time required for new parts during the design process.

A simple finite-difference model was developed to describe the heat transfer in the capillary fringe during the heating of packed beds in a steam environment, using glass beads as the model medium. This model is based on transient heat conduction equation and was developed in an Excel spreadsheet. Laboratory experiments were used to collect properties data and to test the model.

Publication suite à la confèrence : 8th Int. Conf. on Mechanical and Physical Behaviour of Materials Under Dynamic Loading (Dijon 2006); International audience; A new experimental torsion test is developed to achieve intermediate strain rates. The gauge length of the classical torsion bar (27 mm) is reduced within the range 0 to 5 mm. Analytical predictions with simple constitutive equation show that strain rates achieve the magnitude of 250 s - 1. A finite difference analysis is proposed to simulate the test with more evolved constitutive equations. A comparison between experimental and numerical results shows a good agreement.

Open and short circuits as used in MMICs (monolithic microwave integrated circuits) are investigated by means of a finite difference method in the frequency domain. Both mode conversion and finite metallization thickness are accounted for. For the open stub, noticeable mode conversion is observed, whereas the short circuit behavior shows a significant dependence on metallization thickness. >

The evolution, design, and characterization of a novel leadframe for plastic encapsulated devices are described, with details of its application in a 160-lead plastic quad flat pack. The challenges of putting a 400 mils square die dissipating 2.5 to 3 watts into this package were examined by finite difference analysis, and various arrangements of the leadframe were simulated until an optimum layout was derived. The leadframe was then refined in consultation with the frame manufacturers and device assemblers to achieve a solution which met all the manufacturability criteria. It was tested using a thermal test chip similar in size to the production chip, and its performance was compared with the options available. The test set-up used a miniature chamber in which the temperature was controlled by means of a bank of Peltier cells. The junction to ambient thermal resistance of the new design of leadframe was 28.6 degrees C per watt, a reduction of almost 25% over the standard leadframe. >

It is shown that a finite difference method for numerically determining the propagation characteristics of optical waveguide devices can be extended to deal with structures containing complex refractive indices in a straightforward manner. The resulting complex finite difference method has been validated and its potential as a design tool demonstrated with studies of a silicon based p-i-n optical rib waveguide modulator and a semiconductor laser.

Nonisothermal crystallizing kinetics for nucleated polyethylene terephthalate (PET) are combined with transient heat transfer models to predict crystalline levels throughout the process of extruding and thermoforming crystallizing PET (CPET). The analysis includes: PET molecular weight effect (through IV) Nucleant level effect Cooling of extruded sheet on chill rolls Convection in the thermoforming oven Oven radiant heater temperature Radiation interchange efficiency in the heating oven Equilibration Mold surface temperature and atmosphere Cooling time The analysis compares distributed parameter finite difference analysis with a lumped parameter method. Material-environmental parametric studies are conducted using the lumped parameter method. The patent literature data are confirmed using an expanded version of the lumped parameter method.

Compositional changes in the alloy beneath scales have been examined for the oxidation of Ni-27.4%Cr and Ni-40.2% Cr in 1 atm oxygen in the temperature range 1073–1473°K. Calculations of the rate of approach of the interfacial alloy composition to a constant value are compared with experimental data. Theoretical chromium depletion profiles obtained using both a finite difference analysis and an analytical expression are shown to be essentially equivalent and in good agreement with experimental measurements. The consequences of alloy depletion for the scaling behavior, when the protective scale is ruptured, are discussed.

An improved finite difference analysis has been used to calculate self-consistent axisymmetric cellular shapes. The results obtained are compared with the analytical models which have been proposed to describe array growth. It is concluded that the analytical models should be used with extreme caution in the cellular region. A preliminary examination of the stability of the steady state shapes has been made numerically. The results are compared with experiment where it is found that neither the minimum undercooling condition nor marginal stability analysis as applied, correctly predicts the growth conditions. The model includes solute diffusion in the solid so that the extent of microsegregation is fully described for the first time.

Comparison is made between the numerical solution for temperature histories at a nuclear waste site and the analytical solution of a correlated thermal problem. The differences between both solutions are found. Both problems are nonlinear diffusion problems connected with the disposal of nuclear wastes.

The behavior of a unidirectional fiber-reinforced composite ma terial subjected to a shear loading in the direction of the filaments is of fundamental importance in the understanding of composite material behavior. The shear stiffness and strength values asso ciated with this type of loading can be considered as fundamental properties characterizing the material. The problem of a doubly periodic rectangular array of parallel elastic filaments of doubly symmetric but otherwise arbitrary shape contained in an elastic matrix material subjected to shear stress components in the directions of the filament axes has been formulated using a theory of elasticity analysis. A finite difference representation of the governing partial differential equations of equilibrium and stress-displacement equations has been utilized in obtaining a solution by a systematic over-relaxation procedure. Numerical results have been obtained for a variety of filament cross-sectional shapes, various filament-to-matrix shear modulus ratios (ranging from zero to infinity), and a range of filament spacings varying from filaments nearly in contact to extremely wide spacings in which interaction effects between filaments are essentially zero. Theoretical results have been compared with the limited experimental data presently available. The results obtained permit a detailed description of the micro mechanical behavior of a composite material subjected to longitudinal shear loading. A study of local stress distributions in the composite provides a means of predicting shear strength as well as stiffness as a function of the material properties of the constituents and their geometry. 1. S. W. Tsai, "Strength Characteristics of Composite Materials," NASA Contractor Report NASA CR-224, April 1965. 2. S. W. Tsai, D. F. Adams, and D. R. Doner, "Effect of Constituent Material Properties on the Strength of Fiber-Reinforced Composite Materials," Air Force Materials Laboratory Contractor Report AFML-TR-66-190, August 1966. 3. Z. Hashin and B. W. Rosen, "The Elastic Moduli of Fiber-reinforced Materials," J. Applied Mechanics, Vol. 31E (1964), p. 223. 4. C. H. Chen and Shun Cheng, "Mechanical Properties of Fiber-reinforced Com posites and of Perforated Solids," J. Composite Materials, Vol. 1 (1967), p. 30. 5. H. B. Wilson, Jr. and J. G. Goree, "Transverse Shear Loading in an Elastic Matrix Containing Two Elastic Circular Cylindrical Inclusions," Mathematical Studies of Composite Materials III, Rohm and Haas Company Report, Hunts ville, Alabama, June 1966.

The stress distributions in two thick circular plates with diameter to thickness ratios of 5 and 7 are obtained from a finite difference analysis and a three-dimensional frozen stress study. The results are compared with those obtained from a rational use of thin-plate theory and also with those given by the British Standard B.S. 1500 Design Code. It is shown that the finite difference study employing a relatively coarse net yields comparative field stress values to those provided by the frozen stress study and that a rational use of thin-plate theory gives a closer approximation to the peak stresses than those predicted by the design code. The assumption of linear bending stress employed in the thin-plate theory, however, is shown to be only approximately true for the plates of practical proportions studied.

AN ANALYSIS IS DEVELOPED FOR THE DETERMINATION OF THE COMPRESSIVE STRESS-STRAIN CURVE OF CONCRETE IN FLEXURE. THE METHOD IS BASED ON USING A "LEAST SQUARES" FIT OF A POLYNOMIAL EXPRESSION TO EXPERIMENTAL DATA FROM REINFORCED OR PRESTRESSED CONCRETE BEAM TESTS. IT IS SHOWN THAT THE METHOD GIVES BETTER CORRELATION WITH EXPERIMENTALLY MEASURED MOMENTS THAN THE FINITE DIFFERENCE ANALYSIS AND CAN BE EASILY ADAPTED TO THE COMPUTER. /ACI/

We present a new rapid approach to the analysis of strongly guiding and longitudinally varying semiconductor rib waveguide structures. Our technique, which is a synthesis of the beam propagation and finite difference methods is Hermitian, second-order accurate and intrinsically stable.