The performance of CBN tools in the machining of titanium alloys

Advancements in the aerospace, nuclear and other industries require the enhanced in-service performance of engineering components. These requirements have resulted in the large scale development and use of heat-resistant and high-strength materials such as titanium alloys, which pose considerable machining problems. In this study on machining of titanium alloy using CBN tools, the machining performance was evaluated in terms of cutting force, specific cutting pressure, cutting temperature, chip strain and surface finish.     

An improvement to the interacting multiple model (IMM) algorithm

Computing the optimal conditional mean state estimate for a jump Markov linear system requires exponential complexity, and hence, practical filtering algorithms are necessarily suboptimal. In the target tracking literature, suboptimal multiple-model filtering algorithms, such as the interacting multiple model (IMM) method and generalized pseudo-Bayesian (GPB) schemes, are widely used for state estimation of such systems. We derive a reweighted interacting multiple model algorithm. Although the IMM algorithm is an approximation of the conditional mean state estimator, our algorithm is a recursive implementation of a maximum a posteriori (MAP) state sequence estimator. This MAP estimator is an instance of a previous version of the EM algorithm known as the alternating expectation conditional maximization (AECM) algorithm. Computer simulations indicate that the proposed reweighted IMM algorithm is a competitive alternative to the popular IMM algorithm and GPB methods     

Physical layer impairment-aware shared path protection in wavelength-routed optical networks

The Journal of Supercomputing - In this paper, physical layer impairment (PLI)-aware shared path protection (SPP) scheme for single-link failures in transparent optical WDM mesh networks is...     

Location and Sizing of Defects in Coated Metallic Pipes Using Limited View Scattered Data in Frequency Domain

The inverse problem of reconstructing the location and size of defects in a coated metallic pipe from single frequency limited view electromagnetic scattered field is considered. Specifically, the paper addresses the problem of assessing shape changes in the shadow region entailed by limited view data in 2D by operating in an intermediate size parameter (ka) range. The inverse scattering problem is formulated as a non-linear optimization problem solved through genetic algorithm that seeks to minimize in the least-squared sense the difference between measured data and simulated data through iterations of the solution to a forward problem. The hybrid finite element boundary integral formulations were used to solve the forward problem of coated metallic pipe with defects. The proposed inversion methodology was applied for shadow region shape change assessment to determine whether a metal pipe is coated or not, and to reconstruct the location and size of corrosion-like defect, over a range of size parameters. The study is carried out using transverse electric and transverse magnetic polarized fields. To understand the effect of coating on backscattered fields, parametric studies are conducted using numerical data. A range for size parameter \(2.0\le ka\le 4\) was found to produce the highest contrast between defect free pipe and coated metallic pipes with defects in the deep shadow region. The experiments are carried out using vector network analyzer in an anechoic chamber. The inversion results obtained using measured data were found be in good agreement with inversion results obtained using synthetic data. Estimated extent of corrosion in deep shadow region of a coated metallic pipe was found to be within 9 % of actual extent of corrosion.     

Free vibration studies on typical large flexible spacecraft appendages under vacuum conditions

This paper deals with theoretical and experimental investigations on the free vibration characteristics of representative large flexible solar array appendages used in spacecrafts under vacuum environmental conditions prevailing in space. Eight different configurations of solar panels with varied flexibility and surface area have been studied. The theoretical results, namely the modal parameters, have been correlated with results from experiments. These are performed on solar arrays of different configurations under varied parameters of panel flexibility, vacuum and amplitudes of vibration.     

Mixed convection in wall plumesConvection mixte dans les panaches parietauxErzwungene und freie konvektion bei wandauftriebsströmungenCмeшaннaя кoнвeкция в cвoБoднoкoнвeктивныч cтpyяч нa cтeнкe

An analysis is presented for mixed convection effects in a wall plume flow. The results apply downstream from the source. The method of matched asymptotic expansions has been used to obtain a consistent solution by simultaneously including both the effects of mixed convection and of higher order boundary layer corrections. Several subtle and interesting features of this flow arise and are explained. The unexpected role played by Prandtl number is clearly illustrated. For example, the effect of an aiding imposed forced flow is to reduce surface shear stress, for Pr = 0.7, and to increase it for Pr = 6.7. Further, it has been shown that such a Prandtl number effect on the surface shear stress is dependent on the kind of heating condition imposed at the surface. Results of numerical calculations are presented for two values of Prandtl number, 0.7 and 6.7, as characteristic of air and water, respectively. The overall effect of mixed convection on the downstream decay of surface temperature and on the maximum value of tangential velocity is seen to be greater in air than in water.     

Analysis of flange joints with elastic bolt

The contact zone and pressure distribution between two elastic plates joined by an elastic bolt and nut are estimated using finite element analysis. Smooth interfacial conditions are assumed in all the regions of contact. Eight node axisymmetric ring elements are used to model the structure. The matrix solution is obtained through frontal technique and this solution technique is shown to be very efficient for the iterative scheme adopted to determine the extent of contact. A parametric study is conducted varying the elastic properties of bolt and plate materials, bolt head diameter and thickness of the plates. The method of approach presented in this paper provides a solution with a realistic idealization of tension flange joints.     

Fundamental materials studies of undoped, In-doped, and As-doped Hg1−xCdxTe

Variable magnetic-field Hall and transient photoconductance-lifetime measurements were performed on a series of undoped, In-doped, and As-doped HgCdTe samples grown by molecular beam epitaxy (MBE). Use of quantitative mobility-spectrum analysis (QMSA) combined with multiple carrier-fitting (MCF) techniques indicates that the majority of samples contain an interfacial n-type layer that significantly influences the interpretation of the electrical measurements. This n-type layer completely masks the high-quality electrical properties of undoped or low n-type In-doped HgCdTe, as well as complicating the interpretation of activation in As-doped p-type HgCdTe. Introduction of an intentional n-type background, typically created through doping with In to “recover” high mobility, is actually shown to increase the “bulk” layer conductivity to a level comparable to the interface layer conductivity. Photoconductance-lifetime measurements suggest that In-doping may introduce Shockley-Read-Hall (SRH) recombination centers. Variable-field Hall analysis is shown to be essential for characterizing p-type material. Photoconductance-lifetime measurements suggest that trapping states may be introduced during the incorporation and activation of As. Two distinctly different types of temperature dependencies were observed for the lifetimes of As-doped samples.