Design of the drive mechanism for a reciprocating coal feeder

Material handling is undoubtedly the most important and in fact an indispensable job in industries for it is encountered at every stage right from the time raw materials enter the factory gate to the point when it leaves in form of finished products. The engineering of material handling falls under two categories depending on form of material: bulk solid handling and unit handling. In case of handling lumpy materials like coals etc. , feeder plays a vital role as an uninterrupted source of uniform feed provider to the conveyor system. Although several feeders like belt, apron, screw, feeders etc are available, reciprocating feeders are still in use because it ensures a continuous and controlled feed rate, is low in cost, its drive mechanism is simple, it can handle wide range of miscellaneous materials including lumps, easy in assembly and disassembly and maintenance requirement is quite low. The challenge which we have taken via the project, is to design a drive mechanism for a reciprocating coal feeder. We call it a challenge because we have to design various intricate components like couplings, worm reducers, gearbox etc. We call it complicated since all the components are interdependent on each other to a great extent. So we cannot design anything randomly . We have to take into considerations the smallest of small things like the various forces acting, how each component can fail under various stress conditions. We have to optimize everything right from the motor selection, to speed reduction ratio selection, to the capacity of coal which we can handle. We are going to follow the above-mentioned strategies so that our project does not remain just a theory but can become a reality for industries

Quantum Brownian Motion on noncommutative manifolds: construction, deformation and exit times

We begin with a review and analytical construction of quantum Gaussian process (and quantum Brownian motions) in the sense of [25],[10] and others, and then formulate and study in details (with a number of interesting examples) a definition of quantum Brownian motions on those noncommutative manifolds (a la Connes) which are quantum homogeneous spaces of their quantum isometry groups in the sense of [11]. We prove that bi-invariant quantum Brownian motion can be 'deformed' in a suitable sense. Moreover, we propose a noncommutative analogue of the well-known asymptotics of the exit time of classical Brownian motion. We explicitly analyze such asymptotics for a specific example on noncommutative two-torus A{\theta}, which seems to behave like a one-dimensional manifold, perhaps reminiscent of the fact that A{\theta} is a noncommutative model of the (locally one-dimensional) 'leaf-space' of the Kronecker foliation

Electromechanical response of textured ferroelectric PZT thin film stacks

Thin film piezoelectric materials with high piezoelectric coefficients such as PbZr0.52Ti0.48O3 (PZT) offer several advantages to microelectromechanical systems (MEMS) due to their low power requirements, large displacements, high work and power densities, as well as high sensitivity in a wide dynamic range. The performance of PZT-based MEMS can be further improved by increasing the piezoelectric response of PZT polycrystals via texture control. However, freestanding PZT films, in particular for MEMS, are comprised of several other films forming a stack. These additional layers serve as seeding (TiO2), buffer (SiO2), and conducting (Pt) layers with substantial thickness and stiffness compared to the main PZT layer. As a result, quantitative understanding of the mechanical behavior of each layer is required in order to extract the electromechanical response of the PZT layer itself in a stack. This dissertation research investigated (a) the mechanical behavior of highly {111} textured Pt films grown on {100}-TiO2 which is required to achieve ~100% (001)-textured PZT films, and (b) the electromechanical behavior of freestanding textured PZT film stacks, with PZT texture varying from 100% (001) to 100% (111). PZT stacks in the form of d31-type actuators were comprised of an elastic SiO2 layer, an adhesion layer of {100}-textured rutile TiO2, a metallization layer of highly {111}-textured Pt, a seed layer of PbTiO3, the PZT layer, a second Pt metallization layer, and, finally, a thin ALD layer of Al2O3 and HfO2 deposited by atomic layer deposition. Microscale uniaxial tension tests were carried out on patterned SiO2 films and combinations of layers, such as TiO2-Pt, SiO2-TiO2-Pt, SiO2-TiO2-Pt-PZT and SiO2-TiO2-Pt-PZT-Pt-ALD to determine the properties of each layer. Experiments on TiO2-Pt stacks with different Pt thickness showed that a reduction in film thickness increases the flow stress of Pt. The evolution of flow stress with plastic strain as a function of film thickness and grain size was successfully modeled, providing insight into the deformation behavior of polycrystalline metal films grown epitaxially on polycrystalline underlayers. Mechanical experiments on (SiO2-TiO2-Pt-PZT) and full PZT stacks (SiO2-TiO2-Pt-PZT-Pt-ALD) showed that the mechanical, piezoelectric and ferroelastic properties of PZT thin films depend strongly on grain orientation. The open circuit PZT modulus varied linearly with %(001) and %(111) texture factors between the two texture bounds: a lower bound for 100% (001) and an upper bound for 100% (111). Pure (001) texture exhibited maximum non-linearity and ferroelastic domain switching, contrary to pure (111) texture with more linear behavior and the least amount of switching. A micromechanics model based on the Eshelby inclusion problem was employed to calculate the strain due to domain switching. The model reproduced the experimentally observed non-linearities in the stress vs. strain curves of (001) and (111) textured PZT films. Finally, the linear piezoelectric and ferroelectric properties of textured PZT films at low and high electric fields, respectively, were calculated using laser Doppler vibrometer measurements on PZT unimorphs. All samples, except one comprised of 73% (001) and 27% (111) texture, demonstrated saturation in transverse piezoelectric coefficients beyond ~150 kV/cm. Notably, the sample with the combination of 73% (001) and 27% (111) textures showed stable transverse piezoelectric coefficients at all electric field values with technologically significant implications to ultra-low-power MEMS. The ferroelectric and linear piezoelectric coefficients (with the exception of the aforementioned sample with stable linear properties) depended strongly on film texture, and the effective transverse strain and stress coefficients varied linearly with %(001) and %(111) texture factors. PZT films with 100% (001) orientation displayed 150%, 140%, and 80% larger linear piezoelectric strain coefficient, saturated strain coefficient and saturated stress coefficient, respectively, compared to films with 100% (111) orientation for the same electric bias and the same film thickness. Finally, PZT films with pure (001) texture showed 20% higher dielectric constant and 50% higher figure of merit in sensing than films with pure (111) texture. This dissertation research provided insight into material microstructure-electromechanical property relationships for freestanding PZT film stacks. The results will assist the development of reliable low power PZT-based MEMS devices with higher actuation and better sensing characteristics

Size effects in mechanical behavior of submicron and nanometer thick textured Pt films

{111}-textured Platinum (Pt) thin films facilitate the growth of {001}-textured PZT films with high transverse piezoelectric coefficients, and serve as the electrodes for PZT films for MEMS. However, the film thickness, texture, and strain rate dependent mechanical behavior of magnetron sputtered {111}-textured freestanding Pt films are unknown, and are expected to control failure initiation of the PZT films. To this goal, freestanding Pt films with thicknesses of 50, 150, 200, 500, and 1000 nm and perfect {111}-texture were studied via uniaxial tension experiments at strain rates 10-6 ? 10 s–1. The elastic modulus, E = 164 ± 8 GPa, was independent of strain rate and film-thickness and was in very good agreement with theoretical estimates for the in-plane modulus of {111}-textured polycrystalline Pt. The yield stress increased with decreasing film-thickness: thicker films, 500 and 1000 nm, yielded early and accumulated larger plastic strain (~0.6–0.7%) when compared with the 200- and 150-nm Pt films that accumulated only 0.15% plastic strain, and the 50-nm films that failed in a brittle manner. This thickness dependence could be the result of both intergranular (grain rotation, grain boundary sliding) and intragrain (dislocation motion) plasticity taking place in thicker films as compared to only intergranular plasticity taking place in the thinner films. Strain-rate hardening was low for 1000-nm thick films, with strain-rate sensitivity m ~ 0.01, and was practically absent for all other film thicknesses. All films failed at only ~1% strain which may be attributed to localization of slip due to texture. Fracture for the 1000 nm and 500 nm films occurred at ~45o with respect to the loading direction with transgranular features and strain localization, whereas the failure of 200, 150, and 50 nm thick films was brittle

Quantum dot polarized light sources

The design, operation and performance of quantum dot spin-polarized vertical cavity surface emitting lasers (VCSELs) and single-photon sources are described and discussed. The effects of spin-induced gain anisotropy on output polarization and threshold current reduction have been studied along with the high-frequency response in a spin-polarized VCSEL. While the output circular polarization in a VCSEL follows the out-of-plane magnetization characteristics of the ferromagnetic spin injector, the output polarization of the spin-polarized single-photon source shows a switching behavior which is explained by invoking the exciton fine structure in the quantum dots and the effects of electron–hole exchange splitting due to in-plane quantum dot rotational asymmetry.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90780/1/0268-1242_26_1_014002.pd