The Experts below are selected from a list of 35658 Experts worldwide ranked by ideXlab platform

A H Kokabi - One of the best experts on this subject based on the ideXlab platform.

  • the modeling and process Analysis of resistance spot welding on galvanized steel sheets used in car body manufacturing
    Materials & Design, 2012
    Co-Authors: S M Hamidinejad, Farhad Kolahan, A H Kokabi
    Abstract:

    In this study, the resistance spot welding (RSW) process of the galvanized interstitial free (IF) steel sheets and galvanized bake hardenable (BH) steel sheets, used in the manufacturing of car bodies, has been modeled and optimized. The quality measure of a resistance spot welding joint is estimated from the tensile–shear strength. Furthermore, four important process parameters, namely welding current (WC), welding time (WT), electrode force (EF), and holding time (HT) are considered as the factors influencing the quality of the joints. In order to develop an accurate relationship between the process inputs (4-component vectors) and the response output (tensile–shears strength) at first a linear regression model was utilized but the Residuals Analysis revealed a non-linear behavior. Therefore, an artificial neural network (ANN) was proposed because the ANNs are capable of mapping the non-linear systems. A back propagation neural network model was developed to analyze RSW process and the interaction effects of the parameters. In the second phase of this research, Genetic Algorithm with the fitness function based on an ANN model was employed as an optimization procedure for determining a set of process parameters; as a result, the maximum joint strength was obtained. Optimization results showed high compatibility with the actual experimental data.

S M Hamidinejad - One of the best experts on this subject based on the ideXlab platform.

  • the modeling and process Analysis of resistance spot welding on galvanized steel sheets used in car body manufacturing
    Materials & Design, 2012
    Co-Authors: S M Hamidinejad, Farhad Kolahan, A H Kokabi
    Abstract:

    In this study, the resistance spot welding (RSW) process of the galvanized interstitial free (IF) steel sheets and galvanized bake hardenable (BH) steel sheets, used in the manufacturing of car bodies, has been modeled and optimized. The quality measure of a resistance spot welding joint is estimated from the tensile–shear strength. Furthermore, four important process parameters, namely welding current (WC), welding time (WT), electrode force (EF), and holding time (HT) are considered as the factors influencing the quality of the joints. In order to develop an accurate relationship between the process inputs (4-component vectors) and the response output (tensile–shears strength) at first a linear regression model was utilized but the Residuals Analysis revealed a non-linear behavior. Therefore, an artificial neural network (ANN) was proposed because the ANNs are capable of mapping the non-linear systems. A back propagation neural network model was developed to analyze RSW process and the interaction effects of the parameters. In the second phase of this research, Genetic Algorithm with the fitness function based on an ANN model was employed as an optimization procedure for determining a set of process parameters; as a result, the maximum joint strength was obtained. Optimization results showed high compatibility with the actual experimental data.

Y Blanco - One of the best experts on this subject based on the ideXlab platform.

  • quality prediction of resistance spot welding joints of 304 austenitic stainless steel
    Materials & Design, 2009
    Co-Authors: Oscar Martin, Pilar De Tiedra, Manuel Alejandro Rodenas Lopez, Manuel Sanjuan, C Garcia, F Martin, Y Blanco
    Abstract:

    Abstract The quality level of a resistance spot welding (RSW) joint of 304 austenitic stainless steel (ASS) is estimated from its tensile shear load bearing capacity (TSLBC). The quality levels are set by ultrasonic nondestructive testing. The objective of the present work is to develop a tool capable of reliably predicting the TSLBC (and consequently the quality level) of RSW joints from three welding parameters: (1) welding time (WT); (2) welding current (WC); (3) electrode force (EF). Firstly, a linear regression model is attempted but the Residuals Analysis reveals nonlinear behaviour. An artificial neural network (ANN) is proposed because the ANNs are capable of mapping nonlinear systems. The inputs are 3-component vectors, a component for each of the aforementioned welding parameters. The training of the ANN uses supervised learning mechanism. Therefore each input must come with its respective desired output (target). This target is the TSLBC of the RSW joint obtained with the respective input. The number of neurons in the hidden layers is selected considering the overfitting phenomenon: the number of neurons in the hidden layers that minimizes the validation mean square error (MSE) is 4. With the selected ANN, 3–4–4–1, the aim of the present study is achieved because this ANN produces good results in prediction from inputs nonused in the training.

Indiran S Pather - One of the best experts on this subject based on the ideXlab platform.

  • sustained release theophylline tablets by direct compression part 1 formulation and in vitro testing
    International Journal of Pharmaceutics, 1998
    Co-Authors: James Syce, Indiran S Pather, Irina Russell, Steven H Neau
    Abstract:

    In an effort to reduce production costs, a simple, direct compression sustained release formulation consisting, principally, of the drug (theophylline) and ethylcellulose was investigated. Ethylcellulose compacts well and also retards drug release. In addition, matrices of this polymer display slow surface erosion which can be enhanced by the incorporation of a swelling agent. This property was utilized in an attempt to decrease the attenuation of the release rate that is observed with matrix tablets that follow the Higuchi pattern of drug release. The release rate decreases because the external layers of the tablet become depleted and water must penetrate the deeper layers of the tablet to reach the remaining drug. The theophylline to ethylcellulose ratio and the tablet hardness were found to influence the rate of drug release. It was possible to sustain the release of a therapeutic dose of theophylline over a 12-h period. Mathematical modeling showed an equally good fit between the data and (a) the Higuchi model, or (b) a model that took into account diffusion, relaxation of the polymer, and erosion. However, the shape of the release curve was altered slightly in those tablets that eroded to a greater extent and Residuals Analysis illustrated a better fit with the latter model. The erosion mechanism can be used to lessen one of the major problems associated with hydrophobic and plastic matrix tablets, i.e. the continuous reduction in the terminal release rate with time.

  • sustained release theophylline tablets by direct compression part 1 formulation and in vitro testing
    International Journal of Pharmaceutics, 1998
    Co-Authors: James Syce, Indiran S Pather, Irina Russell, Steven H Neau
    Abstract:

    In an effort to reduce production costs, a simple, direct compression sustained release formulation consisting, principally, of the drug (theophylline) and ethylcellulose was investigated. Ethylcellulose compacts well and also retards drug release. In addition, matrices of this polymer display slow surface erosion which can be enhanced by the incorporation of a swelling agent. This property was utilized in an attempt to decrease the attenuation of the release rate that is observed with matrix tablets that follow the Higuchi pattern of drug release. The release rate decreases because the external layers of the tablet become depleted and water must penetrate the deeper layers of the tablet to reach the remaining drug. The theophylline to ethylcellulose ratio and the tablet hardness were found to influence the rate of drug release. It was possible to sustain the release of a therapeutic dose of theophylline over a 12-h period. Mathematical modeling showed an equally good fit between the data and (a) the Higuchi model, or (b) a model that took into account diffusion, relaxation of the polymer, and erosion. However, the shape of the release curve was altered slightly in those tablets that eroded to a greater extent and Residuals Analysis illustrated a better fit with the latter model. The erosion mechanism can be used to lessen one of the major problems associated with hydrophobic and plastic matrix tablets, i.e. the continuous reduction in the terminal release rate with time.

Steven H Neau - One of the best experts on this subject based on the ideXlab platform.

  • sustained release theophylline tablets by direct compression part 1 formulation and in vitro testing
    International Journal of Pharmaceutics, 1998
    Co-Authors: James Syce, Indiran S Pather, Irina Russell, Steven H Neau
    Abstract:

    In an effort to reduce production costs, a simple, direct compression sustained release formulation consisting, principally, of the drug (theophylline) and ethylcellulose was investigated. Ethylcellulose compacts well and also retards drug release. In addition, matrices of this polymer display slow surface erosion which can be enhanced by the incorporation of a swelling agent. This property was utilized in an attempt to decrease the attenuation of the release rate that is observed with matrix tablets that follow the Higuchi pattern of drug release. The release rate decreases because the external layers of the tablet become depleted and water must penetrate the deeper layers of the tablet to reach the remaining drug. The theophylline to ethylcellulose ratio and the tablet hardness were found to influence the rate of drug release. It was possible to sustain the release of a therapeutic dose of theophylline over a 12-h period. Mathematical modeling showed an equally good fit between the data and (a) the Higuchi model, or (b) a model that took into account diffusion, relaxation of the polymer, and erosion. However, the shape of the release curve was altered slightly in those tablets that eroded to a greater extent and Residuals Analysis illustrated a better fit with the latter model. The erosion mechanism can be used to lessen one of the major problems associated with hydrophobic and plastic matrix tablets, i.e. the continuous reduction in the terminal release rate with time.

  • sustained release theophylline tablets by direct compression part 1 formulation and in vitro testing
    International Journal of Pharmaceutics, 1998
    Co-Authors: James Syce, Indiran S Pather, Irina Russell, Steven H Neau
    Abstract:

    In an effort to reduce production costs, a simple, direct compression sustained release formulation consisting, principally, of the drug (theophylline) and ethylcellulose was investigated. Ethylcellulose compacts well and also retards drug release. In addition, matrices of this polymer display slow surface erosion which can be enhanced by the incorporation of a swelling agent. This property was utilized in an attempt to decrease the attenuation of the release rate that is observed with matrix tablets that follow the Higuchi pattern of drug release. The release rate decreases because the external layers of the tablet become depleted and water must penetrate the deeper layers of the tablet to reach the remaining drug. The theophylline to ethylcellulose ratio and the tablet hardness were found to influence the rate of drug release. It was possible to sustain the release of a therapeutic dose of theophylline over a 12-h period. Mathematical modeling showed an equally good fit between the data and (a) the Higuchi model, or (b) a model that took into account diffusion, relaxation of the polymer, and erosion. However, the shape of the release curve was altered slightly in those tablets that eroded to a greater extent and Residuals Analysis illustrated a better fit with the latter model. The erosion mechanism can be used to lessen one of the major problems associated with hydrophobic and plastic matrix tablets, i.e. the continuous reduction in the terminal release rate with time.