NISCAIR Online Periodicals Repository Collection: IJEMS Vol.19(1) [February 2012]

Direct search optimization technique for the solution of inverse nonlinear heat conduction problem

Title: Direct search optimization technique for the solution of inverse nonlinear heat conduction problem

Authors: Mehta, R C

Abstract: An iterative procedure is used to calculate the transient temperature in a finite slab with temperature dependent thermal conductivity. Closed-form constant property solution is considered as the initial guess to solve the heat conduction equation. The results obtained by this method are in good agreement with the numerical solution. The iterative method for the solution of the nonlinear heat conduction equation has the advantage that temperatures can be directly found at any specified time and location whereas the numerical approach requires the development of temperature profile from right from the initial state. The present paper includes a direct search optimization method for the estimation of the convective heat transfer coefficient from the transient temperature data measured in one-dimensional finite slab with the linear variation of thermal conductivity with temperature. The direct search optimization method does not need calculation of the sensitivity coefficient. The algorithm does not depend on the future-temperature information. The convective heat transfer coefficients are estimated in a typical rocket nozzle using the measured transient temperature at the outer surface. The results computed by the present algorithm are in good agreement with the numerical solution.

Page(s): 67-71

Preparation and properties of linear low density polyethylene based nanocomposite films for food packaging

Title: Preparation and properties of linear low density polyethylene based nanocomposite films for food packaging

Authors: Manikantan, M R; Varadharaju, N

Abstract: Packaging of foods in high barrier and strong materials is essential to attain food safety, and nanocomposite technology leads in search of the above kind of packaging material. The effect of compatibilizer, nanoclay and thickness of film on morphology, oxygen transmission rate (OTR), water vapor transmission rate (WVTR), tensile strength and percent elongation of linear low density polyethylene (LLDPE)-based nanocomposite films are studied using response surface methodology. The maximum reduction in OTR and WVTR over the control (0% compatibilizaer, 0% nanoclay and 100 µm film thickness) is 24.7% and 64.9%, respectively in the treatment having 5% compatibilizer, 2% nanoclay and 100 µm thickness. The regression models are developed for the prediction of OTR and WVTR. The maximum increase in the tensile strength and percent elongation over the control (0% compatibilizaer, 0% nanoclay and 100 µm film thickness) is 54% and 7.64%, respectively. Treatment having 5% compatibilizer, 2% nanoclay and 100 µm thickness of nanocomposite films showed better morphological, barrier and strength characteristics than other treatments. This paper helps to design the packaging films according to the requirement of foods to be stored using the developed regression models.

Page(s): 54-66

Electrical conductivity of Ca-doped YFeO₃

Title: Electrical conductivity of Ca-doped YFeO₃

Authors: Jacob, K T; Rajitha, G; Dasgupta, N

Abstract: Electrical conductivity and Seebeck coefficient of calcium-doped YFeO₃, a potential cathode material in solid oxide fuel cells (SOFC), are measured as function of temperature and composition in air to resolve conflicts in the literature both on the nature of conduction (n- or p-type) and the types of defects (majority and the minority) present. Compositions of Y_1-xCa_xFeO_3−δ with x = 0.0, 0.025, 0.05 and 0.1 are studied in the temperature range from 625 to 1250 K. All Y_1-xCa_xFeO_3−δ samples show p-type semiconducting behaviour. Addition of Ca up to 5% dramatically increases the conductivity of YFeO₃; increase is more gradual up to 10%. A second phase Ca₂Fe₂O₅ appears in the microstructure for Ca concentrations in excess of 11%.

Page(s): 47-53

An investigation of geometrical defect of cold embossing part utilizing FEM and image processing technique

Title: An investigation of geometrical defect of cold embossing part utilizing FEM and image processing technique

Authors: Abdullah, A B; Sapuan, S M; Samad, Z; Khaleed, H M T; Aziz, N A

Abstract: Accuracy of the forging parts becomes critical as the process depends on many factors. Defect may harm the assembly and tends to affect the performance of the parts. Therefore, it must be understood and detected as soon as the manufacturing begins. The size and complexity of the part limit the defect to be assessed. This study intent to investigate the defect of the cold embossing pin located at the head of a propeller blade. This is to ensure accurate assembly of the blade. In this work, the effects of design and process parameters on the formation of defect are studied using 2-D finite element analysis. The defect can be measured based on the incomplete filling of the region using the captured images from the FE result. The results seem to show that there is less effect from the diameter of punch and internal cavity, but more obvious due to the distance to the edge. The FE results are in good agreement with the experimental results.

Page(s): 41-46

NISCAIR Online Periodicals Repository Collection: IJEMS Vol.19(1) [February 2012]

Direct search optimization technique for the solution of inverse nonlinear heat conduction problem

Preparation and properties of linear low density polyethylene based nanocomposite films for food packaging

Electrical conductivity of Ca-doped YFeO3

An investigation of geometrical defect of cold embossing part utilizing FEM and image processing technique

Electrical conductivity of Ca-doped YFeO₃