Dynamics of segregation and fluidization of binary mixtures in a cylindrical fluidized bed

Dynamics of segregation and fluidization of unary particles and binary mixtures in a cylindrical fluidized bed is investigated using temporally– and spatially–resolved measurements of solids volume fraction (α_s) performed using Electrical Capacitance Tomography (ECT). Through the comparison with high-speed imaging, we have shown that ECT can be used to measure the segregation behavior in cylindrical fluidized beds quantitatively. ECT measurements have been used further to quantify the effects of mixture composition, particle–diameter ratio, and superficial gas velocity on the bed segregation behavior. Dynamics of fluidization behavior is characterized using the time–evolution of local α_s fluctuations, corresponding frequency distribution, and bubble size distribution. Further, a relation between the measured variance of α_s fluctuations at different radial locations and corresponding flow structures under different fluidization conditions is established. The present work helps to understand dynamics of segregation and fluidization of binary mixtures and to provide a database for validation of Eulerian multifluid CFD models.     

Evolution of Grain-Boundary Microstructure and Texture in Interstitial-Free Steel Processed by Equal-Channel Angular Extrusion

The equal-channel angular extrusion (ECAE) of Ti-bearing interstitial-free (IF) steel was performed following two different routes, up to four passes, at a temperature of 300 °C. The ECAE led to a grain refinement to submicron size. After the second pass, the grain size attained saturation thereafter. The microstructural analysis indicated the presence of coincident-site lattice (CSL) boundaries in significant fraction, in addition to a high volume fraction of high-angle random boundaries and some low-angle boundaries after the deformation. Among the special boundaries, Σ3 and Σ13 were the most prominent ones and their fraction depended on the processing route followed. A deviation in the misorientation angle distribution from the Mackenzie distribution was noticed. The crystallographic texture after the first pass resembled that of simple shear, with the {112}, {110}, and {123} aligned to the macroscopic shear plane.     

Novel adhesion promotion of aluminium for aerospace environments

This study focuses on analysing the durability of adhesive bonds formed in samples of Aluminium 6063, Titanium Nitride deposited Al 6063 and Anodized Al 6063 using epoxy adhesive Weicon A. Two types of studies are performed, first, samples of Aluminium 6063, Titanium Nitride deposited Al 6063 and Anodized Al 6063, are bonded by an epoxy adhesive Weicon A. Second, the samples are bonded by the adhesive with reinforcement of Ca₂SiO₄ nanoparticles in different proportions. The samples are examined using the scanning electron microscopy to study the morphology of the coating. A lap shear test is performed to determine the strength of the adhesive after the specimens were subjected to harsh chemical environments. A thermogravimetric analysis is performed on the adhesive to understand the effect of nanoparticles in the thermal stability in the Weicon A. It is understood from the tests that the titanium nitride coated Al 6063 samples bonded with Weicon A exhibited greater bond strength and also retained the strength when exposed to harsh environments. The inclusion of calcium silicate nano-particles showcased a considerable reduction in the bond strength. The thermal stability of Weicon A seems to be unaffected by the inclusion of calcium silicate nanoparticles.     

Design and performance of high-gain free-electron lasers withgrazing incidence, unstable ring resonators

Grazing incidence, ring resonators have been proposed for high-grain free-electron lasers to alleviate the problem of inordinately high irradiance on intracavity optics. Such resonators are also relatively compact, and consequently, their alignment tolerances are more manageable. A geometric design algorithm and detailed computer analysis of a high-gain free-electron ring laser with hyperboloid-paraboloid grazing incidence telescopes is presented. A 3-D wave optics computer code is used to determine the loaded-cavity transverse-mode characteristics of the high-gain unstable ring and to examine the issue of transverse-mode control as a function of the key resonator parameters. Perturbation sensitivity of the individual elements is also determined and compared to that of a corresponding long stable resonator     

A novel fractional order fuzzy PID controller and its optimal time domain tuning based on integral performance indices

A novel fractional order (FO) fuzzy Proportional-Integral-Derivative (PID) controller has been proposed in this paper which works on the closed loop error and its fractional derivative as the input and has a fractional integrator in its output. The fractional order differ-integrations in the proposed fuzzy logic controller (FLC) are kept as design variables along with the input–output scaling factors (SF) and are optimized with Genetic Algorithm (GA) while minimizing several integral error indices along with the control signal as the objective function. Simulations studies are carried out to control a delayed nonlinear process and an open loop unstable process with time delay. The closed loop performances and controller efforts in each case are compared with conventional PID, fuzzy PID and PI^λD^μ controller subjected to different integral performance indices. Simulation results show that the proposed fractional order fuzzy PID controller outperforms the others in most cases.     

DiGVis: A system for comprehension and creation of directed graphs for the visually challenged

One of the major barriers for the social inclusion of blind persons is the limited access to graphics-based learning resources which are highly vision oriented. This paper presents a cost-effective tool which facilitates comprehension and creation of virtual directed graphs, such as flowcharts, using alternate modalities of audio and touch. It provides a physically accessible virtual spatial workspace and multimodal interface to non-visually represent directed graphs in interactive manner. The concept of spatial query is used to aid exploration and mental visualization through audio and tactile feedback. A unique aspect of the tool, named DiGVis, offers compatible representations of directed graphs for the sighted and non-sighted persons. A study with 28 visually challenged subjects indicates that the tool facilitates comprehension of layout and directional connectivity of elements in a virtual diagram. Further, in a pilot study, blind persons could independently comprehend a virtual flowchart layout and its logical steps. They were also able to create the flowchart data without sighted assistance using DiGVis. A comparison with sighted subjects using DiGVis for similar task demonstrates the effectiveness of the technique for inclusive education.