NUMERICAL ANALYSIS OF TURBULENT GAS-SOLID FLOWS IN A ROUGH HORIZONTAL CHANNEL USING THE EULERIAN TWO-FLUID MODEL

Turbulent gas-solid flows are encountered in many industrial processes including pneumatic transport of granular materials such as pulverized coal, circulating fluidized beds and dust and particle-exhaust pollution control systems. Modelling the gas-solid flow is a major challenge since the flow is turbulent which renders the system non-linear. In addition, the presence of particles further complicates the flow. The two-fluid formulation is a popular approach for modelling gas-particle flows that describes the motion of both phases in an Eulerian framework. The current dissertation explores the effects of wall roughness on the particle-phase properties of a turbulent gas-solid flow in a horizontal channel. An in-house numerical code is modified to simulate a fully developed turbulent gas-solid flow; the numerical code is based on the two-fluid formulation adopted from the model of Rao et al. (2011). The gas-solid flow in the horizontal channel is asymmetric due to the gravity acting transverse to the flow. Three different studies were conducted to document the response of the particle-phase properties to different flow conditions. The first study focuses on the effect of hydrodynamic roughness on the gas-solid flow. The hydrodynamic effect of wall roughness was implemented in the model using a two-layer version of the k - ε model based on Durbin et al. (2001). The thesis documents outcomes of the simulations that compare the flow for the rough wall with that for the smooth wall. It was found that the hydrodynamic roughness energized the particles present in the flow via turbulence modulation. Wall roughness alters the particle-wall interactions. The particle-wall interactions were characterized using the boundary conditions of Johnson and Jackson (1987), which defined the specularity coefficient. The second study focuses specifically on the role of the specularity coefficient in characterizing wall roughness. The channel wall is rough from a particle perspective. The outcomes of the simulations were compared to the experimental study of Sommerfeld and Kussin (2004). The experiment explores the effect of different levels of wall roughness on the particle-phase properties. The dissertation documents the comparisons between the simulations and the experimental data for the mean solids velocity and the solids volume fraction profiles. The profiles for properties like turbulence kinetic energy, granular temperature, solids viscosity and solids shear stress for different levels of roughness were also documented and analyzed. It was found that specularity coefficient plays a significant role in characterizing the wall roughness. The predicted profiles for the mean solids velocity and the solids volume fraction deviated from the experimental profile in the near-wall region. The degree of deviation from the experimental data decreased with an increase in the specularity coefficient. This implies that the specularity coefficient is less effective for walls with smaller roughness. The third study focuses on the sensitivity of the particle-phase properties to three different parameters; the specularity coefficient, the mass loading and the Stokes number. Increasing the specularity coefficient increases the number of diffuse particle-wall collisions. It was found that increasing specularity coefficient increased the granular temperature, which resulted in higher predictions for the solids viscosity and the solids shear stress. The increase in the mass loading increased the number of particles present in the flow. It was found that the increase in mass loading increased the granular temperature by increasing the frequency of particle-wall collisions. The effect of particle inertia was investigated by increasing the Stokes number. The solids velocity monotonically decreases with an increase in the Stokes number while the behaviour of the granular temperature and solids shear stress were more complicated

Fault Discrimination in Wireless Sensor Networks

In current times, one of the promising and interesting areas of research is Wireless Sensor Networks. A Wireless Sensor Network consists of spatially distributed sensors to monitor environmental and physical conditions such as temperature, sound, pressure etc. It is built of nodes where each node is connected to one or more sensors. They are used for Medical applications, Security monitoring, Structural monitoring and Traffic monitoring etc. The number of sensor nodes in a Wireless Sensor Network can vary in the range of hundreds to thousands. In this project work we propose a distributed algorithm for detection of faults in a Wireless Sensor Network and to classify the faulty nodes. In our algorithm the sensor nodes are classified as being Fault Free, Transiently Faulty or Intermittently Faulty considering the energy differences from its neighbors in different rounds of the algorithm run. We have shown the simulation results in the form of the output messages from the nodes depicting their health and also compared the results in form of graphs for different average node degrees and different number of rounds of our algorithm run

The effect of ripe papaya, Carica papaya, as natural carotenoids meal on body pigmentation and growth performance in banded gourami, Trichogaster fasciata

The present investigation elucidates the synergistic effects of improvised ecological parameters and ripe papaya (Carica papaya) meal on skin pigmentation, growth performance and survival of Banded gourami, Trichogaster fasciata, under confined environment. A feeding trial of 60 days was done with initial length groups from 6.6 to 9.7 cm using five isonitrogenous experimental diets formulated by supplementing graded levels of carotenoids at 1 to 5% and a control without carotenoids. Two ecological parameters temperature and light intensity were elevated using artificial modulators. At the onset of the feeding trial, the total carotenoid concentration in fish muscle in both male (2.94±0.07 μg.g-1) and female (2.54±0.05 μg.g-1), respectively, which significantly increased, highest being in male (6.86±0.12 μg.g-1) and female (5.96±0.07μg.g-1) fishes fed with 4% papaya meal. Positive correlation, (0.98) in male and (0.97) female was observed between elevated levels of dietary carotenoids and body pigmentation which revealed that incorporation of dietary carotenoids resulted in a significant increase in total carotenoid concentration in chromatophores. Congenial effects were observed on body indices was revealed by positive correlation of weight (0.79) to elevated levels of carotenoid and 100% survival rate of the fishes. The feeding regimes showed ripe papaya meal as cheap natural colour enhancer source can be safely supplemented at 4% levels in the diets to increase the skin pigmentation and optimum conditioning in optimized captive environment having temperature range of 26-28oC and light intensity 344.0-346 Lux, without any xenobiotic effect on Banded gourami.

(Half) Wormholes under Irrelevant Deformation

Recently it has been shown by Almheiri and Lin [1] that the reconstruction of black-hole interior is sensitive to knowing the exact coupling of the boundary theory even if the coupling is irrelevant. This motivates us to enlarge the set of the one-time and two-time toy models inspired from the SYK by deforming the same with \textit{irrelevant} coupling. We find that both half-wormholes as well as the wormholes persist in presence of the deformation, leading to a similar mechanism for curing the factorization problem. While for the one time case, the deformed partition function and its moments change by an overall factor, which can completely be absorbed into a renormalization of coupling, for the two time (or coupled one time) SYK we find non-trivial dynamics of the saddles as the couplings are varied. Curiously, the \textit{irrelevant} deformations that we consider can also be thought of as an ensemble average over an overall scaling of the original undeformed Hamiltionian with an appropriate probability distribution, this allows for the possibility that half-wormholes may also be present in suitably defined ensemble of theories.Comment: 15 pages+ Appendix, 5 figure

The neutron production rate measurement of an indigenously developed compact D-D neutron generator

One electrostatic accelerator based compact neutron generator was developed. The deuterium ions generated by the ion source were accelerated by one accelerating gap after the extraction from the ion source and bombarded to a target. Two different types of targets, the drive - in titanium target and the deuteriated titanium target were used. The neutron generator was operated at the ion source discharge potential at +Ve 1 kV that generates the deuterium ion current of 200 mA at the target while accelerated through a negative potential of 80 kV in the vacuum at 1.3×10-2 Pa filled with deuterium gas. A comparative study for the neutron yield with both the targets was carried out. The neutron flux measurement was done by the bubble detectors purchased from Bubble Technology Industries. The number of bubbles formed in the detector is the direct measurement of the total energy deposited in the detector. By counting the number of bubbles the total dose was estimated. With the help of the ICRP-74 neutron flux to dose equivalent rate conversion factors and the solid angle covered by the detector, the total neutron flux was calculated. In this presentation the operation of the generator, neutron detection by bubble detector and estimation of neutron flux has been discussed

Using Conditional Inference Forests to Identify the Factors Affecting Crash Severity on Arterial Corridors

Introduction The study aims at identifying traffic/highway design/driver-vehicle information significantly related with fatal/severe crashes on urban arterials for different crash types. Since the data used in this study are observational (i.e., collected outside the purview of a designed experiment), an information discovery approach is adopted for this study. Method Random Forests, which are ensembles of individual trees grown by CART (Classification and Regression Tree) algorithm, are applied in numerous applications for this purpose. Specifically, conditional inference forests have been implemented. In each tree of the conditional inference forest, splits are based on how good the association is. Chi-square test statistics are used to measure the association. Apart from identifying the variables that improve classification accuracy, the methodology also clearly identifies the variables that are neutral to accuracy, and also those that decrease it. Results The methodology is quite insightful in identifying the variables of interest in the database (e.g., alcohol/ drug use and higher posted speed limits contribute to severe crashes). Failure to use safety equipment by all passengers and presence of driver/passenger in the vulnerable age group (more than 55 years or less than 3 years) increased the severity of injuries given a crash had occurred. A new variable, ‘element’ has been used in this study, which assigns crashes to segments, intersections, or access points based on the information from site location, traffic control, and presence of signals. Impact The authors were able to identify roadway locations where severe crashes tend to occur. For example, segments and access points were found to be riskier for single vehicle crashes. Higher skid resistance and k-factor also contributed toward increased severity of injuries in crashes

Resummed transverse momentum distribution of pseudo-scalar Higgs boson at NNLOA_A+NNLL

In this article we have studied the transverse momentum distribution of the pseudo-scalar Higgs boson at the Large Hadron Collider (LHC). The small \pt region which provides the bulk of the cross section is not accessible to fixed order perturbation theory due to the presence of large logarithms in the series. Using the universal infrared behaviour of the QCD we resum these large logarithms up to next-to-next-to-leading logarithmic (NNLL) accuracy. We observe a significant reduction in theoretical uncertainties due to the unphysical scales at NNLL level compared to the previous order. We present the $p_T$ distribution matched to NNLO$_A$+NNLL, valid for the whole $p_T$ region and provide a detailed phenomenological study in the context of both 14 TeV and 13 TeV LHC using different choices of masses, scales and parton distribution functions which will be useful for the search of such particle at the LHC in near future.Comment: 20 pages, 8 figures, 2 table

Subspace coverings with multiplicities

We study the problem of determining the minimum number $f(n,k,d)$ of affine subspaces of codimension $d$ that are required to cover all points of $\mathbb{F}_2^n\setminus \{\vec{0}\}$ at least $k$ times while covering the origin at most $k-1$ times. The case $k=1$ is a classic result of Jamison, which was independently obtained by Brouwer and Schrijver for $d = 1$. The value of $f(n,1,1)$ also follows from a well-known theorem of Alon and F\"uredi about coverings of finite grids in affine spaces over arbitrary fields. Here we determine the value of this function exactly in various ranges of the parameters. In particular, we prove that for $k \ge 2^{n-d-1}$ we have $f(n,k,d)=2^d k - \left \lfloor \frac{k}{2^{n-d}} \right \rfloor$, while for $n > 2^{2^d k-k-d+1}$ we have $f(n,k,d)= n + 2^dk-d-2$, and also study the transition between these two ranges. While previous work in this direction has primarily employed the polynomial method, we prove our results through more direct combinatorial and probabilistic arguments, and also exploit a connection to coding theory.Comment: 15 page

Spectral Form Factors of Topological Phases

Signatures of dynamical quantum phase transitions and chaos can be found in the time evolution of generalized partition functions such as spectral form factors (SFF) and Loschmidt echos. While a lot of work has focused on the nature of such systems in a variety of strongly interacting quantum theories, in this work, we study their behavior in short-range entangled topological phases - particularly focusing on the role of symmetry protected topological zero modes. We show, using both analytical and numerical methods, how the existence of such zero modes in any representative system can mask the SFF with large period (akin to generalized Rabi) oscillations hiding any behavior arising from the bulk of the spectrum. Moreover, in a quenched disordered system these zero modes fundamentally change the late time universal behavior reflecting the chaotic signatures of the zero energy manifold. Our study uncovers the rich physics underlying the interplay of chaotic signatures and topological characteristics in a quantum system.Comment: 6+4 pages, 6 figure

Strong blocking sets and minimal codes from expander graphs

A strong blocking set in a finite projective space is a set of points that intersects each hyperplane in a spanning set. We provide a new graph theoretic construction of such sets: combining constant-degree expanders with asymptotically good codes, we explicitly construct strong blocking sets in the $(k-1)$-dimensional projective space over $\mathbb{F}_q$ that have size $O( q k )$. Since strong blocking sets have recently been shown to be equivalent to minimal linear codes, our construction gives the first explicit construction of $\mathbb{F}_q$-linear minimal codes of length $n$ and dimension $k$, for every prime power $q$, for which $n = O (q k)$. This solves one of the main open problems on minimal codes.Comment: 20 page