मात्स्यिकी से आजीविका प्राप्त करने के पारिप्रेक्ष्य में जल‌ ‌जीव (बहुउद्देशीय) आहार संयंत्र की विनिदिष्ट भूमिका

कृपया पूरा लेख पढे

Simulation of Thermo-fluid Interactions in Cryogenic Stage Turbine Startup System Using AUSM+-UP-based Higher-order Accurate Flow Solver

High-speed turbines are used in upper stage liquid engines of launch vehicles and the most common ones include LH2 and LOX turbines used in the cryogenic stages. The main constraints in the design of turbine system for a liquid engine are thermal loads, mass flow and pressure drops in various systems ahead of the turbine inlet. The temperature of the combustion products/gases reaching the turbine blades must be well below the melting point of the turbine blade material and the mass flow rate must be sufficient to generate the required power. Turbine can be started in two ways, by generating gases using a solid propellant-based spinner motor, and using compressed gases stored in gas bottles. The first method involves design challenges but requires less space and weight. On the other hand, second method is simple but requires more space. Because of the space and weight constraints associated with the upper stages, first method is preferred and discussed in this paper. It consists of a solid propellant-based spinner motor with a convergent-divergent nozzle, a guiding duct connecting nozzle exit, and the turbine inlet manifold in the form of a torroid with nozzle block having 39 guiding nozzles. The combustion products generated by the spinner motor are guided to the manifold through the guiding duct. Inlet manifold acts as a reservoir and supplies hot gases uniformly to the turbine through 39 nozzles. This study addresses the role of  computational fluid dynamics in the design of turbine startup system using unstructured cell-centered AUSM+-UP-based finite volume solver with the twoequation turbulence model. The flow and the thermal characteristics of the solid motor with a convergentdivergent nozzle were studied to evaluate the gas temperature, operating pressure, and flow velocities. The guiding duct along with the inlet manifold was analysed separately to find the drop in temperature and pressure within the system. From the simulation results, the mass flow through each guiding nozzle, and hence, energy available could be evaluated to ensure proper functioning of the turbine.Defence Science Journal, 2009, 59(3), pp.215-229, DOI:http://dx.doi.org/10.14429/dsj.59.151

A CASE STUDY ON GAS RECOVERY UNIT FOR R-22

The present research is concerned with proper recovery of the R-22 [1] gas, which is widely used in various R.A.C. fields on the system failure and reusing these recovered gases again for the future use. It is well known that various cooling units are widely spread in their applications and are circulating R-22 as a refrigerant. It is intended to recover this type of refrigerant by any means preventing its ill effects on environment. The time required for recovering is less, hence the system requires less time. The recovery rate of the unit ranges between 1 to 2 kg/min for 1 ton capacity of the system. We can use the unit for any ton capacity of the breakdown system refrigeration and air conditioning system to recover the gas. The. Global warming [2] is the process wherein the average temperature of the Earth\u27s near surface air increases, owing largely to various man-made activities. Though there are some natural causes for this rise in temperature, they stand to be insignificant when compared to the man-made causes. Understanding global warming & green house gas causes and effects can give us a brief idea of the dreadful phenomena our future generations may have to face. There are some of the prominent global warming causes and effects

Numerical Simulation of Interaction of Sonic Jet with High Speed Flow over a Blunt Body using Solution Mapped Higher Order Accurate AUSM+-UP Based Flow Solver

The development of a numerical procedure based on AUSM+-UP scheme using higher order accurate reconstruction method is presented. A code based on this is used for the simulation of film cooling for reentry module. Here the convective fluxes are evaluated using AUSM+-UP scheme. Least square based derivative evaluation is used to compute diffusive fluxes. The numerical code has been successfully validated using standard experimental data for counter flow injection. Analysis has been carried out for a simple axisymmetric reentry module with and without film cooling, for a free stream Mach number of 8.0. The predicted adiabatic wall temperatures were compared for both the cases. Film cooling is found to be effective for this configuration and injected coolant remains confined to the boundary layer formed by the free stream from nose tip to the aft end of the module. Numerical simulation of film cooling provides vital information required for design of effective cooling system such as number of counter flow injectors, their dimensions and locations, injection pressure and temperature, mass flow rate required etc

A high-performance matrix-matrix multiplication methodology for CPU and GPU architectures

Current compilers cannot generate code that can compete with hand-tuned code in efficiency, even for a simple kernel like matrix–matrix multiplication (MMM). A key step in program optimization is the estimation of optimal values for parameters such as tile sizes and number of levels of tiling. The scheduling parameter values selection is a very difficult and time-consuming task, since parameter values depend on each other; this is why they are found by using searching methods and empirical techniques. To overcome this problem, the scheduling sub-problems must be optimized together, as one problem and not separately. In this paper, an MMM methodology is presented where the optimum scheduling parameters are found by decreasing the search space theoretically, while the major scheduling sub-problems are addressed together as one problem and not separately according to the hardware architecture parameters and input size; for different hardware architecture parameters and/or input sizes, a different implementation is produced. This is achieved by fully exploiting the software characteristics (e.g., data reuse) and hardware architecture parameters (e.g., data caches sizes and associativities), giving high-quality solutions and a smaller search space. This methodology refers to a wide range of CPU and GPU architectures

Phase Field Model for Three-Dimensional Dendritic Growth with Fluid Flow

We study the effect of fluid flow on three-dimensional (3D) dendrite growth using a phase-field model on an adaptive finite element grid. In order to simulate 3D fluid flow, we use an averaging method for the flow problem coupled to the phase-field method and the Semi-Implicit Approximated Projection Method (SIAPM). We describe a parallel implementation for the algorithm, using Charm++ FEM framework, and demonstrate its efficiency. We introduce an improved method for extracting dendrite tip position and tip radius, facilitating accurate comparison to theory. We benchmark our results for two-dimensional (2D) dendrite growth with solvability theory and previous results, finding them to be in good agreement. The physics of dendritic growth with fluid flow in three dimensions is very different from that in two dimensions, and we discuss the origin of this behavior

GBT/MUSTANG-2 9' resolution imaging of the SZ effect in MS0735.6+7421: Confirmation of the SZ cavities through direct imaging

Context. Mechanical feedback from active galactic nuclei is thought to be the dominant feedback mechanism quenching cooling flows and star formation in galaxy cluster cores. It, in particular, manifests itself by creating cavities in the X-ray emitting gas, which are observed in many clusters. However, the nature of the pressure supporting these cavities is not known. Aims. Using the MUSTANG-2 instrument on the Green Bank Telescope (GBT), we aimed to measure thermal Sunyaev-Zeldovich (SZ) effect signals associated with the X-ray cavities in MS0735.6+7421, a moderate-mass cluster that hosts one of the most energetic active galactic nucleus outbursts known. We used these measurements to infer the level of nonthermal sources of pressure that support the cavities, such as magnetic fields and turbulence, as well as relativistic and cosmic ray components. Methods. We used the preconditioned gradient descent method to fit a model for the cluster, cavities, and central point source directly to the time-ordered data of the MUSTANG-2 signal. We used this model to probe the thermodynamic state of the cavities. Results. We show that the SZ signal associated with the cavities is suppressed compared to the expectations for a thermal plasma with temperatures of a few tens of keV. The smallest value of the suppression factor, f, that is consistent with the data is 0.4, lower than what has been inferred in earlier work. Larger values of f are possible once the contribution of the cocoon shock surrounding the cavities is taken into account. Conclusions. We conclude that in the 'thermal' scenario, when half of the pressure support comes from electrons with a Maxwellian velocity distribution, the temperature of these electrons must be greater than 100 keV at 2.5 confidence. Alternatively, electrons with nonthermal momentum distribution could contribute to the pressure, although existing data do not distinguish between these two scenarios. The baseline model with cavities located in the sky plane yields a best-fitting value of the thermal SZ signal suppression inside cavities of 0.5, which, at face value, implies a mix of thermal and nonthermal pressure support. Larger values of f (up to 1, i.e., no thermal SZ signal from the cavities) are still possible when allowing for variations in the line-of-sight geometry

Inferences from Surface Brightness Fluctuations of Zwicky 3146 via the Sunyaev-Zel’dovich Effect and X-Ray Observations

The galaxy cluster Zwicky 3146 is a sloshing cool-core cluster at z = 0.291 that in Sunyaev-Zel’dovich (SZ) imaging does not appear to exhibit significant pressure substructure in the intracluster medium. We perform a surface brightness fluctuation analysis via Fourier amplitude spectra on SZ (MUSTANG-2) and X-ray (XMM-Newton) images of this cluster. These surface brightness fluctuations can be deprojected to infer pressure and density fluctuations from the SZ and X-ray data, respectively. In the central region (Ring 1, r < 100′′ = 440 kpc, in our analysis), we find fluctuation spectra that suggest injection scales around 200 kpc (∼140 kpc from pressure fluctuations and ∼250 kpc from density fluctuations). When comparing the pressure and density fluctuations in the central region, we observe a change in the effective thermodynamic state from large to small scales, from isobaric (likely due to the slow sloshing) to adiabatic (due to more vigorous motions). By leveraging scalings from hydrodynamical simulations, we find an average 3D Mach number ≈0.5. We further compare our results to other studies of Zwicky 3146 and, more broadly, to other studies of fluctuations in other clusters

Linking the dust and chemical evolution: Taurus and Perseus -- New collisional rates for HCN, HNC, and their C, N, and H isotopologues

HCN, HNC, and their isotopologues are ubiquitous molecules that can serve as chemical thermometers and evolutionary tracers to characterize star-forming regions. Despite their importance in carrying information that is vital to studies of the chemistry and evolution of star-forming regions, the collision rates of some of these molecules have not been available for rigorous studies in the past. We perform an up-to-date gas and dust chemical characterization of two different star-forming regions, TMC 1-C and NGC 1333-C7, using new collisional rates of HCN, HNC, and their isotopologues. We investigated the possible effects of the environment and stellar feedback in their chemistry and their evolution. With millimeter observations, we derived their column densities, the C and N isotopic fractions, the isomeric ratios, and the deuterium fractionation. The continuum data at 3 mm and 850 $\mu$m allowed us to compute the emissivity spectral index and look for grain growth as an evolutionary tracer. The H$^{13}$CN/HN$^{13}$C ratio is anticorrelated with the deuterium fraction of HCN, thus it can readily serve as a proxy for the temperature. The spectral index $(\beta\sim 1.34-2.09)$ shows a tentative anticorrelation with the H$^{13}$CN/HN$^{13}$C ratio, suggesting grain growth in the evolved, hotter, and less deuterated sources. Unlike TMC 1-C, the south-to-north gradient in dust temperature and spectral index observed in NGC 1333-C7 suggests feedback from the main NGC 1333 cloud. With this up-to-date characterization of two star-forming regions, we found that the chemistry and the physical properties are tightly related. The dust temperature, deuterium fraction, and the spectral index are complementary evolutionary tracers. The large-scale environmental factors may dominate the chemistry and evolution in clustered star-forming regions.Comment: 25 pages, 20 figure