Video indexing through human face images using LGFA and window technique

Multimedia Tools and Applications - Adaptive video monitoring settings have been extensively deployed in recent years. Smart video monitoring technology enables the acquisition and analysis of...     

Effect of pyrophyllite on vitrification and on physical properties of triaxial porcelain

Quartz was progressively replaced by pyrophyllite in a conventional porcelain mix with a composition of 50% clay, 25% quartz and 25% feldspar. The addition resulted in early vitrification and decreased thermal expansion of the sintered specimen. Addition of up to 15% pyrophyllite decreased the fired shrinkage by 6% and improved the fired strength by around 29% compared to the standard body. The gradual increase in flexural strength with incorporation of pyrophyllite was primarily due to the elimination of stresses in the structure with a decreasing quartz content as well as to the increasing amount of secondary mullite distributed throughout the matrix forming an interlocking network. However, the firing temperature and the generation of the correct amount of properly sized mullite needles are vital in achieving the desired strength. Pyrophyllite was found to dissolve in the melt in preference to quartz. Beyond the optimum proportion of pyrophyllite, a large volume of glass formed as well as large elongated pores distributed in the matrix resulting in deterioration of mechanical properties.     

A novel method for sensing rotational speed, linear displacement and current using superconducting BPSCCO magnetic sensor

For many decades, magnetic sensors have been of great assistance to mankind in variety of functions that include simple compass based navigational systems to devices that monitor the invisible biological activities. In industries magnetic sensors are in great demand for control and measurement of linear and rotary position sensing etc, because of its non destructive and contact less way of detection. Consequently, newer, smarter and cheaper materials are continuously being explored to suit the varied needs of technological requirements. In the present communication, the characteristics of a magnetic sensor, based on the non linear electromagnetic response of the weak links present in the polycrystalline BPSCCO superconductor are reported. The second harmonic response of sintered superconducting BPSCCO pellet in an alternating magnetic field at 40 kHz and 77 K being a strong linear function of low d.c. magnetic field has been utilized for the development of highly sensitive magnetic field sensors. The noise limited resolution of the sensor is found to be 3.16 ×10^-9 T/√Hz for H_a.c = 16 Oe and frequency 40 kHz. We further demonstrate that such HTSC based magnetic sensors are capable of sensing the rotational speed, small displacement and direct current with good resolution. The experimental methods and results obtained are discussed.     

Hexagonal boundary Sierpinski carpet fractal shaped compact ultrawideband antenna with band rejection functionality

In this paper a second iteration Sierpinski carpet fractal shape UWB antenna with hexagonal boundary is presented. The antenna covers the frequency band from 3 GHz to 12 GHz (VSWR ≤ 2). The proposed antenna has the capability to reject 5.15–5.825 GHz band assigned for IEEE802.11a and HIPERLAN/2 which is achieved by embedding a ‘Y’ shaped slot in the radiator that extends to the central conductor of the CPW feed as well. A fabricated prototype is developed where the simulation and experimental results are in good agreement. Measured peak antenna gain varies from 1.25 dBi to 6 dBi within the band. The proposed antenna has a compact size of 33 mm × 32 mm that includes the substrate around the radiating element. Time domain characteristic reveal that the antenna is non-dispersive with a variation of measured group delay within 0.5 ns over the entire band.     

Adhesives with patterned sub-surface microstructures

Inspired by the complex hierarchical structures found in natural adhesives, we have embedded monolithic stack of several microchannels inside soft layers of silicon elastomers. These channels are rectangular in cross-section and their internal surfaces are textured with microscopic pillars arranged in regular arrays. Displacement controlled indentation experiment on these adhesives shows that adhesion and debonding occur not only on the surface of the adhesive but also at the interfaces of the embedded layers. These textures on the channel surface enhance adhesion via “crack arrest and initiation” mechanism. Furthermore, the adhesive is treated by hydrochloric acid so that the siloxane bonds present on the exposed surfaces are hydrolyzed generating silanol groups which on two contacting surfaces increase the effect of self adhesion hysteresis. Thus, the combined effect of surface texturing is integrated with the chemical treatment to increase adhesion.     

Magnetic behavior of weak links in bulk superconducting YBa2Cu3O7−x: Ag composite

The magnetization of a polycrystalline composite YBa₂Cu₃O_7?x :Ag_0.1 in the superconducting state is measured in the presence of a small a.c. magnetic field. With increase in field amplitude, the magnetizationM(t) changes its shape from nearly sinusoidal to square-wave like and then to a two-peak structure. A similar behavior of the magnetizationM(t), calculated from the critical-state model with intergranular critical currentJ _c =αc[μ(H ₀ +¦H¦)]^?1 is obtained. A very good fit is found between the theoretical and experimental results, and the parameters of the model are estimated.     

Matrix method for determining propagation characteristics of optical waveguides

We have transformed the scalar wave equation into a matrix eigenvalue equation, the diagonalization of which gives the guided modes and a discrete representation of the radiation modes. The method is simple and can be used for arbitrary refractive index profiles.     

Accurate method for characterising single-mode fibres: theory and experiment

We present a direct method for determining the modal field from the far-field pattern of single-mode fibres having arbitrary index profiles. Analysis of experimental data shows that the method is relatively simple compared to other methods and gives accurate results.