MHD effect of mixed convection boundary-layer flow of Powell-Eyring fluid past nonlinear stretching surface

Sufficient conditions are found for the existence of similar solutions of the mixed convection flow of a Powell-Eyring fluid over a nonlinear stretching permeable sur- face in the presence of magnetic field. To achieve this, one parameter linear group trans- formation is applied. The governing momentum and energy equations are transformed to nonlinear ordinary differential equations by use of a similarity transformation. These equations are solved by the homotopy analysis method （HAM） to obtain the approximate solutions. The effects of magnetic field, suction, and buoyancy on the Powell-Eyring fluid flow with heat transfer inside the boundary layer are analyzed. The effects of the non- Newtonian fluid （Powell-Eyring model） parameters ε and δon the skin friction and local heat transfer coefficients for the cases of aiding and opposite flows are investigated and discussed. It is observed that the momentum boundary layer thickness increases and the thermal boundary layer thickness decreases with the increase in ε whereas the momentum boundary layer thickness decreases and thermal boundary layer thickness increases with the increase in δ for both the aiding and opposing mixed convection flows.

Evaluation of computer imaging technique for predicting the SPAD readings in potato leaves

Facilitating non-contact measurement,a computer-imaging system was devised and evaluated to predict the chlorophyll content in potato leaves.A charge-coupled device(CCD)camera paired with two optical filters and light chamber was used to acquire green(550±40 nm)and red band(700±40 nm)images from the same leaf.Potato leaves from 15 plants differing in coloration(green to yellow)and age were selected for this study.Histogram based image features,such as mean and variances of green and red band images,were extracted from the histogram.Regression analyses demonstrated that the variations in SPAD meter reading could be explained by themeangrayandvariances of gray scale values.The fitted least square models based on the mean gray scale levels were inversely related to the chlorophyll content of the potato leaf with a R^2 of 0.87 using a green band image and with an R2 of 0.79 using a red band image.With the extracted four image features,the developed multiple linear regression model predicted the chlorophyll content with a high R^2 of 0.88).The multiple regression model(using all features)provided an average prediction accuracy of 85.08% and amaximum accuracy of 99.8%.The prediction model using only mean gray value of red band showed an average accuracy of 81.6% with a maximum accuracy of 99.14%.

MORPHOTROPIC PHASE BOUNDARY AND DIELECTRIC RELAXATION STUDY OF(Bi_(0.5)Na_(0.5))TiO_(3)-BaTiO_(3)LEAD-FREE CERAMIC

We report the temperature and frequency dependence impedance spectroscopy of(1-x)(Bi_(0.5)Na_(0.5))TiO_(3-x)BaTiO_(3)(abbreviated as BNT-BT)ceramics with 0≤x≤0.07 prepared by conventional solid-state route.X-ray diffraction analysis indicated that a solid solution is formed when BaTiO_(3)diffuses into the(Bi_(0.5)Na_(0.5))TiO_(3)lattice and a morphotropic phase boundary between rhombohedral and tetragonal locates at x=0.07.The microstructure indicated that the grain size reduces and the shape changes from rectangular to quasi-spherical with increase in BaTiO_(3)content.Complex Impedance Spectroscopy analysis suggested the presence of temperature-dependent relaxation process in the materials.The modulus mechanism indicated the nonDebye type of conductivity relaxation in the materials,which is supported by impedance data.The activation energies have been calculated from impedance,electric modulus studies and dc conductivity which suggests that the conductions are ionic in nature.The activation energy increases with increase of BT content up to x=0.05 and decreases at x=0.07 which also indicates the presence of morphotropic phase boundary at x=0.07.