Shock wave induced primary thermal fragmentation of coal particles

Coal particles when subjected to shock waves can undergo rapid fragmentation, pyrolysis, and combustion, causing enhanced process intensity and efficiency. Particle fragmentation plays a crucial role in this process. Exposure of coal particles to a shock wave is modelled in the present work as combined convection and radiation at the surface and conduction in the interior. Local temperatures within a coal particle and the corresponding thermal stresses are computed to study particle failure. Particle fracture is modelled by a three-parameter Weibull probability to predict the failure location and time. Simulations indicate that pulverized coal of size up to 250 μm subjected to a shock wave for varying operational, thermal, and physical parameters can experience initial failure within 150 μs. Particles of size d ≥ 50 μm or higher wave strengths (with Mach numbers M ≥ 5) mostly trigger exfoliation, while interior fragmentation dominates at smaller sizes (d ≤ 25 μm). An initial fracture study reveals that pulverized coal with predominant sizes d ≤ 100 μm and the coal rank from lignite to bituminous coal is potentially suitable for detonation combustion in waves at Mach numbers M = 3–6. Coal particles under continuous exposure to post-shock conditions undergo recursive exfoliation until the core is 20–40 μm, after which an interior fragmentation phase is seen until the core is about 1–3 μm. Much finer coal particles, of the order of internal fragmenting cores, are hardly fractured due to low thermal stresses caused by rapid uniform heating. The fracture model approach for studying shock-induced combustion is validated by a reasonable match of the computed ignition delay with experiments. The fragmentation history indicates a substantial increase in the particle surface area and temperature under shock exposure, as against conventional combustion, leading to an increased order of the burning rates at the onset of ignition, which can sustain through the entire burning phase.     

GTD analysis of the radiation patterns of conical horns

The far-field radiation patterns of conical horns of arbitrary flare angles excited in theTE_{11}mode are obtained employing the geometric theory of diffraction (GTD) based on the theory of Kouyoumjian and Pathak [3] and the slope diffraction technique [4]. The analysis presented enables one to predict accurately radiation patterns over the main beam, near and far sidelobes, and the becklobe of the horn. Validity of the analysis is established by satisfactory agreement between the calculated and measured patterns of an experimental conical horn. The radiation patterns of wide-flare corrugated conical horns excited in theHE_{11}mode of operation have also been calculated over the main beam, which contains most of the radiated energy (up to -40 dB with respect to boresight field), employing slope diffraction technique, and a good agreement is noticed between the calculated and measured radiation patterns.     

Pattern analysis of paraboloids fed by rectangular waveguides employing multipole expansion techniques

A multipole expansion technqiue is developed for calculating the co-polar and cross-polar radiation patterns of a prime-focus paraboloid fed by a dominant-mode rectangular waveguide feed. Initially, the feed radiation pattern is expressed in terms of electric and magnetic multipoles of different orders which are subsequently used to obtain the secondary radiation patterns (co-polar and cross-polar) in explicit closed form in the form of a rapid by a converging algebraic series. The validity of the analysis is effectively demonstrated by calculating the co-polar and cross-polar patterns of a typical paraboloid and comparing and results with calculations based on the direct numerical integration of the physical optics currents induced on the reflector surface.     

Application of holography in jet acoustic studies

Source strength distribution on a jet boundary was obtained from measurements using the principle of acoustic holography. Measurements were conducted in an open field. Measurement of acoustic pressure on a cylindrical two-dimensional contour located close to the vibrating jet boundary was used to obtain the acoustic source strength distribution at the jet boundary. Particular attention was focussed on back projection of the sound field on to a cylindrical surface. A jet emanating from 5 mm convergent nozzle was used for the holography experiments, assuming axisymmetry. Experimental results were compared with results obtained from holography     

Assessing Consumers’ Co‐production and Future Participation On Value Co‐creation and Business Benefit: an F-P-C-B Model Perspective

Information Systems Frontiers - Co-production and active participation of the consumers are considered to have enhanced the value co-creation activities that would ensure business benefits of a...     

Diagnosis of Alzheimer's disease using Naive Bayesian Classifier

In the world of modern medicine, though there is lot of medical achievements, some diseases still continue to pest the human race. Unfortunately, dementia is one such disease. All over the world, a large number of people are suffering from dementia. Dementia is a brain-related disease. Diagnosis of the disease at the earlier stage is the requirement of the day. Alzheimer's disease (AD) is one of the types of the dementia, and around 60 % of demented are affected from Alzheimer’s disease (Salmon and Bondi in Neuro psychological assessment of dementia. National Institutes of Health, 2010). All over the world, there are around 35 million people suffering from AD and this number is expected to double by 2030 and more than triple by 2050, that is to 115 million (Prince et al. in World Alzheimer report 2013: journey of caringan analysis of long-term care for dementia. Kings College, London, 2013). Diagnosis of this disease at an early stage will help the patients to lead a quality life for the remaining tenure of their life. In this paper, the authors have collected data of 466 subjects by conducting neuropsychological tests. The authors focus on diagnosis of AD for neuropsychological tests using Naive Bayes.

     

Bioconjugation of luminescent silicon quantum dots to gadolinium ions for bioimaging applications

Luminescent imaging agents and MRI contrast agents are desirable components in the rational design of multifunctional nanoconstructs for biological imaging applications. Luminescent biocompatible silicon quantum dots (SiQDs) and gadolinium chelates can be applied for fluorescence microscopy and MRI, respectively. Here, we report the first synthesis of a nanocomplex incorporating SiQDs and gadolinium ions (Gd(3+)) for biological applications. The nanoconstruct is composed of a PEGylated micelle, with hydrophobic SiQDs in its core, covalently bound to DOTA-chelated Gd(3+). Dynamic light scattering reveals a radius of 85 nm for these nanoconstructs, which is consistent with the electron microscopy results depicting radii ranging from 25 to 60 nm. Cellular uptake of the probes verified that they maintain their optical properties within the intracellular environment. The magnetic resonance relaxivity of the nanoconstruct was 2.4 mM(-1) s(-1) (in terms of Gd(3+) concentration), calculated to be around 6000 mM(-1) s(-1) per nanoconstruct. These desirable optical and relaxivity properties of the newly developed probe open the door for use of SiQDs in future multimodal applications such as tumour imaging.     

Detonation initiated disintegration of coal particle due to the maximum strain energy theory

Fragmentation behaviour of coal particles subjected to detonation wave is being studied. Detonation wave is initiated by a plasma cartridge at one end of a detonation tube. Coal particles are subjected to a shock whose temperature depends on the Mach number of the detonation wave. Temperature shock is found to generate thermal stresses which may fragment the coal particles. A non-dimensional mathematical model for the heat transfer process in the coal particle is proposed. Thermal stresses are calculated at various times and radii while maximum strain energy theory is used to understand the failure behavior viz., the time, temperature and location of fracture. A physical model for coal particle fragmentation when subjected to detonation wave is also proposed. The study suggests that detonation combustion of coal is qualitatively different from conventional method.     

Radiation characteristics of dielectric tube antennas

A study of the radiation characteristics of dielectric tube antennas is made with a possibility of its application in communications satellites. It has been shown through a systematic analysis that a multimoded dielectric tube shows a dip in the boresight region which is suitable for satellite antennas.     

A high performance oscillatory combustor burning low-grade coal

A high-performance oscillatory combustor for burning low-grade coal was developed and operated continuously for periods of up to 24 hours. The oscillatory combustor is of extremely simple mechanical design. It has an output capacity of 15–25 kW and its system and combustion efficiencies are 65% and close to 100% respectively. The developed oscillatory combustor is environment-friendly and its pollutant emission is far below that of conventional combustors burning low-grade coal.