Scrotal Lipoma - A Case Study

Lipoma is one of the commonest benign mesenchymal tumor. It occurs with an incidence of 1% of the population. It is composed of fat cells of adult type. It may occur any where in the body, hence called Universal tumor or ubiquitous tumor. But lipomas with in the scrotum are rare and are included under para testicular or extra testicular tumors. To date, definite etiology of lipoma remains uncertain. One theory suggests cytokine release may trigger pre-adipocyte differentiation and maturation. Here we report a case of scrotal lipoma presented as a painless swelling in the scrotum

Dimensional instability studies in machining of Inconel 718 nickel based superalloy as applied to aerogas turbine components

Inconel 718 alloy is used extensively in aerogas turbines and this alloy is most difficult to machine and highly prone to dimensional instability after machining. Such detrimental phenomenon poses an enormous problem in engine assembly and affects structural integrity. This paper highlights the systematic research work undertaken to study the plastic deformation characteristics of Inconel 718, and the effect of process variables on machined surface, subsurface, and dimensional instability. Also illustrated is the technique developed for simultaneous optimization of several process variables such as cutting speed, feed, depth of cut, rake angle, and tool nose radius to control the residual stresses and dimensional instability within the acceptable tolerance band of the component. Prediction equations were developed for residual stress, dimensional instability, tool life, surface finish, and material removal rate. Predicted data were validated experimentally. This paper also presents the qualitative and quantitative data on dimensional instability with specific case studies of jet engine components, and it clearly illustrates the approach followed to develop a technique to control such detrimental effect

Photoelastic Investigation of Turbine Rotor Blade Shrouds

This paper deals with the photoelastic stress analysis carried out to investigate the premature failure of low pressure turbine rotor blade shrouds of an experimental gas turbine. Stress distribution at the shroud aerofoil interface was studied for the original rectangular shroud geometry by stress freezing the photoelastic model blades under rotating conditions. The combined influence of taper shroud geometry and larger fillet radius in mitigating the shroud stress is studied by the three dimensional photoelastic technique and an optimised shroud geometry subject to the stress requirements of blade material is suggested

Control of bow shock induced three-dimensional separation using bleed through holes

The unsteady three-dimensional separated flow on a wall induced by a square protrusion (approximately twice the local boundary layer thickness in width and height), and its control by means of passive suction through holes, is investigated using wind tunnel experiments at Mach $2.87$. The baseline flow without any control was characterized and compared against the cases with bleed. A bow-shaped separation line on the wall with a mid-span separation length of $5.57\delta$ from protrusion face was traced from oil-flow visualization. The averaged pressure distribution surveyed using static pressure ports placed on the wall has mapped plateau, high-pressure, and a low-pressure region in the separated flow, distinctive to three-dimensional interactions. Ten control configurations were tested with suction holes placed along mid-span in the different pressure zones. Significant spanwise `Mean Reduction in Separation Length' of up to $0.93\delta$ was observed from oil-flow visualization. A comparison of observations from various control configurations suggested that bleeding the flow from the high-pressure region could in general delay the separation and reduce the bubble size. Further, time-resolved schlieren visualizations have confirmed reduction in both `mid-span separation length' and `shock-intermittent-region' with the introduction of suction in high-pressure region. Fourier and Proper Orthogonal Decomposition analysis done on the schlieren data has confirmed the presence of low-frequency separation-shock oscillations at Strouhal Numbers of order $10^{-2}$, both with and without control. Furthermore, the amplitudes of separation-shock oscillations in the spectrum were reduced with the introduction of suction simultaneously from two holes placed in high and low-pressure regions

On the zeros of a class of generalised Dirichlet series-XIV

We prove a general theorem on the zeros of a class of generalised Dirichlet series. We quote the following results as samples. Theorem A. Let 0<θ<1/2 and let {an} be a sequence of complex numbers satisfying the inequality |∑Nm=1am − N| ≤ (1/2 − θ)−1 for N = 1,2,3,...,also for n = 1,2,3,...,let α n be real and |αn| ≤ C(θ) where C(θ) > 0 is a certain (small)constant depending only on θ. Then the number of zeros of the function ∑Nn=1an (n + αn)−s = ζ (s) + ∑∞n=1 (an(n + αn)−s − n−s) in the rectangle (½−δ ≤ δ ≤ ½+δ,T ≤ t ≤ 2T) (where 0 < δ < 1/2) is ≥ C(θ,δ)T logT where C(θ,δ) is a positive constant independent of T provided T ≥ T0(θ,δ) a large positive constant. Theorem B. In the above theorem we can relax the condition on a n to |∑Nm=1am − N| ≤ (½ −θ)−1 Nφ and |aN| ≤ (½−θ)−1. Then the lower bound for the number of zeros in (σ ≥ ½−δ,T ≤ t ≤ 2T) is > C(θ,δ) Tlog T(log logT)−1. The upper bound for the number of zeros in σ ≥ ½ +δ,T ≤ t ≤ 2T) is O(T) provided ∑n≤xan = x + Os(x2) for every ε > 0

Study of Unsteadiness due to 3-D Shock-Boundary Layer Interaction in Flow over a Square-faced Protuberance

The dynamics of shock-induced unsteady separated flow past a three-dimensional square-faced protuberance is investigated through wind tunnel experiments. Time-resolved schlieren imaging and unsteady surface pressure measurements are the diagnostics employed. Dynamic Mode Decomposition (DMD) of schlieren snapshots, and analysis of spectrum and correlations in pressure data are used to characterize and resolve the flow physics. The mean shock foot in the centreline is found to exhibit a Strouhal number of around 0.01, which is also the order of magnitude of the Strouhal numbers reported in the literature for two-dimensional shock-boundary layer interactions. The wall pressure spectra, in general, shift towards lower frequencies as we move away from (spanwise) centreline with some variation in the nature of peaks. The cross-correlation analysis depicts the strong dependence of the mean shock oscillations to the plateau region, and disturbances are found to travel upstream from inside the separation bubble. Good coherence is observed between the spanwise mean shock foot locations till a strouhal number of about 0.015 indicating that the 3-D shock foot largely moves to-and-fro in a coherent fashion.Comment: 16 pages, 21 figure