Numerical Characterisation of Jet-Vane based Thrust Vector Control Systems

Computational fluid dynamics methodology was used in characterising jet vane based thrust vector control systems of tactical missiles. Three-dimensional Reynolds Averaged Navier-Stokes equations were solved along with two-equation turbulence model for different operating conditions. Nonlinear regression analysis was applied to the detailed CFD database to evolve a mathematical model for the thrust vector control system. The developed model was validated with series of ground based 6-Component static tests. The proven methodology is applied toa new configuration.Defence Science Journal, Vol. 65, No. 4, July 2015, pp. 261-264, DOI: http://dx.doi.org/10.14429/dsj.65.796

Single Server Interdependent Queueing Model using Baileys Bulk Service rule

In this paper, we consider the single server queueing system having Baileys bulk service rule with phase wise. In this model various system characteristics like probability that the system emptiness, variability of the system size and the coefficient of variation are obtained. DOI: 10.17762/ijritcc2321-8169.150520

Assessment en leren als een twee-eenheid: Onderzoek naar de impact van assessment op leren

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Numerical Simulation of Supersonic Combustion with Parallel Injection of Hydrogen Fuel

Thermochemical exploration of mixing and combustion of parallel hydrogen injection into supersonic vitiated air stream in a divergent duct is presented. Three-dimensional Navier Stokes equations along with twoequation turbulence models and Eddy dissipation concept (EDC)-based combustion models are solved using commercial CFD software. Chemical reaction for H2-air system is modelled by two different simple chemical kinetic schemes namely; infinitely fast rate kinetics as well as the single-step finite rate kinetics. Grid convergence of the solution is demonstrated and a grid convergence index-based error estimate has been provided. Insight into the mixing and combustion of high-speed turbulent reacting flow is obtained through the analysis of various thermochemical variables. Very good comparisons are obtained for the exit profiles for various fluid dynamical and chemical variables for the mixing case. For reacting case, the comparison between the experimental and the numerical values are reasonable. Parametric studies were carried out to study the effect of different turbulence models and turbulent Schmidt numbers. It is seen that Wilcox k-w turbulence model performed better than the other two-equation turbulence models in its class. Strong dependence of flow behaviour on turbulent Schmidt number was observed. The results indicate that simple chemical kinetics is adequate to describe the H2-air reaction in the scramjet combustor.Defence Science Journal, 2010, 60(5), pp.465-475, DOI:http://dx.doi.org/10.14429/dsj.60.5

Dual Polarization Single Port Inset Feed Microstrip Patch Array Antenna

This paper present the designs of array antenna from type of inset-fed microstrip patch antenna by using single port oriented at 45° and -45°. The antennas are capable to generate dualpolarization radiation pattern centered at 45° and -45°. Combinations of two patches using quarter-wave impedance matching technique has been used to designs the array antennas operate at 2.4 GHz. The designs are simulated using Microwave Office 2004 and were fabricated on FR4 substrate with a dielectric constant εr =4.7, tan δ =0.019 and thickness =1.6mm. The simulation and measurement result have been compared. The 3 design 1x2 array antennas yield a bandwidth greater than 5%. The gain of the proposed antennas is also stable with operated frequency. The result showed that the combination of more patches in array can improve the return loss and gain performances. 

Algorithmic construction of static perfect fluid spheres

Perfect fluid spheres, both Newtonian and relativistic, have attracted considerable attention as the first step in developing realistic stellar models (or models for fluid planets). Whereas there have been some early hints on how one might find general solutions to the perfect fluid constraint in the absence of a specific equation of state, explicit and fully general solutions of the perfect fluid constraint have only very recently been developed. In this article we present a version of Lake's algorithm [Phys. Rev. D 67 (2003) 104015; gr-qc/0209104] wherein: (1) we re-cast the algorithm in terms of variables with a clear physical meaning -- the average density and the locally measured acceleration due to gravity, (2) we present explicit and fully general formulae for the mass profile and pressure profile, and (3) we present an explicit closed-form expression for the central pressure. Furthermore we can then use the formalism to easily understand the pattern of inter-relationships among many of the previously known exact solutions, and generate several new exact solutions.Comment: Uses revtex4. V2: Minor clarifications, plus an additional section on how to turn the algorithm into a solution generalization technique. This version accepted for publication in Physical Review D. Now 7 page

Measuring adaptive expertise: development and validation of an instrument

Individuals with adaptive expertise possess the skills to deal with novel problems. Whereas this concept has been around since the mid-1980s, no instrument exists that provides a good operationalization of the theoretical construct. This inhibits the further development of research on adaptive expertise and the evaluation of employees' adaptive expertise levels. Adaptive expertise has been unanimously described as a composition of domain-specific and innovative skills. Some researchers argue that metacognitive skills are also crucial. This study aimed to establish whether an instrument measuring adaptive expertise is composed of these three dimensions. In addition, it was tested whether such an instrument is influenced by task variety and work experience, as previously reported in literature. A sample of 383 professionals and graduates were used to test the Adaptive Expertise Inventory. Through exploratory factor analysis (EFA), (E/CFA), and confirmatory factor analysis (CFA), the quality of the instrument was evaluated. Good model fit was achieved. The final instrument consisted of two dimensionsi.e., domain-specific and innovative skillswith five items each. Regression analysis showed that not work experience, but task variety is related to level of adaptive expertise. The Adaptive Expertise Inventory proved to be a valid instrument for measuring adaptive expertise

A Novel CFD Method to Estimate Heat Transfer Coefficient for High Speed Flows

Accurate prediction of surface temperature of high speed aerospace vehicle is very necessary for the selection of material and determination of wall thickness. For aerothermal characterisation of any high speed vehicle in its full trajectory, it requires number of detailed computational fluid dynamics (CFD) calculations with different isothermal calculations. From the detailed CFD calculations for different flow conditions and geometries, it is observed that heat transfer coefficients scale with the difference of adiabatic wall temperature and skin temperature. A simple ‘isothermal method’, is proposed to calculate heat flux data with only two CFD simulations one on adiabatic condition and other on isothermal condition. The proposed methodology is validated for number of high speed test cases involving external aerodynamic heating as well as high speed combusting flow. The computed heat fluxes and surface temperatures matches well with experimental and flight measured values