Analytical and experimental investigation of mistuning in propfan flutter

An analytical and experimental investigation of the effects of mistuning on propfan subsonic flutter was performed. The analytical model is based on the normal modes of a rotating composite blade and a three-dimensinal subsonic unsteady lifting surface aerodynamic theory. Theoretical and experimental results are compared for selected cases at different blade pitch angles, rotational speeds, and free-stream Mach numbers. The comparison shows a reasonably good agreement between theory and experiment. Both theory and experiment showed that combined mode shape, frequency, and aerodynamic mistuning can have a beneficial or adverse effect on blade damping depending on Mach number. Additional parametric results showed that alternative blade frequency mistuning does not have enough potential for it to be used as a passive flutter control in propfans similar to the one studied. It can be inferred from the results that a laminated composite propfan blade can be tailored to optimize its flutter speed by selecting the proper ply angles

Recurrent Respiratory Papillomatosis (RRP)—Juvenile Onset

In this article, we describe the treatment of long standing juvenile-onset recurrent respiratory papillomatosis (JORRP) with eventual transformation to carcinoma in a patient who lived to the age of 73. Treatment modalities consisted of bronchoscopy and local excision initially. Later, YAG and CO2 laser debulking were used. Radiotherapy, chemotherapy with carboplatin (300 mg/m2) and 5-FU (600 mg/m2), oral methotrexate (5–7.5 mg/week), pegylated Interferon, indole-3-carbamide, and intralesional cidofovir were also utilized in the treatment of this patient. Except for methotrexate, each of the treatment regimens used in this patient, initially decreased growth of the papillomas and improved symptoms experienced by the patient. Interestingly, we found that this patient’s long standing JORRP initially responded to a chemotherapy regimen of 4 cycles of carboplatin (300 mg/m2) and 5-FU (600 mg/m2) as well. Ultimately, the disease became resistant to all forms of treatment and progressed. The patient eventually succumbed to the disease after an approximate 77 year course

Planetary Nebulae with Ultra-Violet Imaging Telescope (UVIT): Far Ultra-violet halo around the Bow Tie nebula (NGC 40)

Context. NGC 40 is a planetary nebula with diffuse X-ray emission, suggesting an interaction of the high speed wind from WC8 central star (CS) with the nebula. It shows strong Civ 1550 {\AA} emission that cannot be explained by thermal processes alone. We present here the first map of this nebula in C IV emission, using broad band filters on the UVIT. Aims. To map the hot C IV emitting gas and its correspondence with soft X-ray (0.3-8 keV) emitting regions, in order to study the shock interaction with the nebula and the ISM. This also illustrates the potential of UVIT for nebular studies. Methods. Morphological study of images of the nebula obtained at an angular resolution of about 1.3" in four UVIT filter bands that include C IV 1550 {\AA} and C II] 2326 {\AA} lines and UV continuum. Comparisons with X-ray, optical, and IR images from literature. Results. The C II] 2326 {\AA} images show the core of the nebula with two lobes on either side of CS similar to [N II]. The C IV emission in the core shows similar morphology and extant as that of diffuse X-ray emission concentrated in nebular condensations. A surprising UVIT discovery is the presence of a large faint FUV halo in FUV Filter with {\lambda}eff of 1608 {\AA}. The UV halo is not present in any other UV filter. FUV halo is most likely due to UV fluorescence emission from the Lyman bands of H2 molecules. Unlike the optical and IR halo, FUV halo trails predominantly towards south-east side of the nebular core, opposite to the CS's proper motion direction. Conclusions. Morphological similarity of C IV 1550 {\AA} and X-ray emission in the core suggests that it results mostly from interaction of strong CS wind with the nebula. The FUV halo in NGC 40 highlights the existence of H2 molecules extensively in the regions even beyond the optical and IR halos.Comment: 4 pages, 5 figures, accepted for publication as a letter in Astronomy & Astrophysic

Selection of optimum combination of fans for bord and pillar coal mines - A Case Study

A good design of ventilation system for a mine should supply adequate air flow for all workings. One of the objectives of the ventilation planning is to select optimum operating points for the fan and its combinations to achieve the required air flow rate. It will improve the safety conditions and minimise the total air power consumption. The objective of this study is to increase ventilation quantity with low operating pressure and effective utilisation of the main mechanical ventilator. Ventilation simulator and CFD modelling studies were conducted with different combinations of fans. Operating parallel fans with the same capacity and blade angle at the return air shaft is the best possible solution for achieving this objective. A detailed case study of the pressure survey of the ventilation network and the simulation results is presented

A comparative study of the consistent and simplified finite element analyses of Eigenvalue, problems

Classical displacement method of the finite element analysis of eigenvalue problems requires the use of consistent and conforming elements. However, simpler approaches based on relaxing the condition of consistency of the element descriptions, such as lumped inertia force method and others are also found to yield satisfactory results. In this paper we make a comparative study of the consistent and simplified approaches with reference to four representative problems. In the simplified approach studied in this paper, the contribution of straining modes in the derivation of the mass and geometric stiffness matrices is neglected and this simplifies their derivation substantially. The results indicate that this simplification introduces only small errors in the eigenvalues

Assessment of accuracies of finite eigenvalues

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Bounds and error control for eigenvalues

Control and estimation of errors are important but difficult aspects of any analysis from which the numerical results are necessarily approximate. The order of difficulty is greater for local or distributed quantities like stresses and displacements than for global Of integrated parameter~ like eigenvalues and stiffnesses. To really bound a desired quantity between a pair of dose upper and lower bounds one should obtain either an oscillatory but clear convergence or, preferably, two rapidly converging sequences one from above and the other from below. Application of the two complementary variational principles of energy and complimentary energy, when both are possible to apply, do yield upper and lower bound approximations. But these or other alternate methods are generally expensive. On the other hand it would be advantageous if one basic procedure could be perturbed in a simple manner to provide both lower and upper bounds and to refine the solution and control the errors without undue effort. This paper discusses this concept and presents three powerful methods to closely bound any desired parameter in a problem. These are particularly valuable for eigenvalue problems

General theory of cylindrical vibrations tubes. Part IV. Uncoupled torsional vibrations of open tubes

Based on the ease in satisfying the free edge boundary conditio/I, open tubes are classified into two types, A and B. Type B tubes have more complicated free-edge boundary condition than that of type A tubes. An alternate formulation is evolved for type B tubes; this makes the free-edge boundary condition as simple as in type A tubes. A simply-supported open tube with the cross-section given by p=S/2π sin 2πS/S, is analysed exactly as well as by using approximation equations; errors in using the first order approximation equations are discussed. A simply-supported open tube of I-section, representative of type B tubes, is analysed by using first and second approximation equations

Planetary Nebulae with UVIT II: Revelations from FUV vision of Butterfly Nebula NGC 6302

The high excitation planetary nebula, NGC 6302, has been imaged in two far-ultraviolet (FUV) filters, F169M (Sapphire; {\lambda}$_{\rm eff}$: 1608 {\AA}) and F172M (Silica; {\lambda}$_{\rm eff}$: 1717 {\AA}) and two NUV filters, N219M (B15; {\lambda}$_{\rm eff}$: 2196 {\AA}) and N279N (N2; {\lambda}$_{\rm eff}$: 2792 {\AA}) with the Ultra Violet Imaging Telescope (UVIT). The FUV F169M image shows faint emission lobes that extend to about 5 arcmin on either side of the central source. Faint orthogonal collimated jet-like structures are present on either side of the FUV lobes through the central source. These structures are not present in the two NUV filters nor in the FUV F172M filter. Optical and IR images of NGC 6302 show bright emission bipolar lobes in the east-west direction with a massive torus of molecular gas and dust seen as a dark lane in the north-south direction. The FUV lobes are much more extended and oriented at a position angle of 113{\deg}. They and the jet-like structures might be remnants of an earlier evolutionary phase, prior to the dramatic explosive event that triggered the Hubble type bipolar flows approximately 2200 years ago. The source of the FUV lobe and jet emission is not known, but is likely due to fluorescent emission from H$_2$ molecules. The cause of the difference in orientation of optical and FUV lobes is not clear and, we speculate, could be related to two binary interactions.Comment: 9 pages, 5 figures, accepted for publication in Astronomy & Astrophysic

General theory of vibrations of cylindrical tubes

The equations governing torsional vibrations of unstiffened cylindrical tubes have been presented. Methods proposed in Part I are illustrated by considering the torsional vibrations of doubly symmetric tubes. An exact solution of a simply supported tube with the boundary of the cross section given by p=s/2π cos 2π S/S is presented. A free- free tube of rectangular cross section is analysed by using first order approximation equations and the results are in good agreement with earlier work