Computation of optimal singular controls

Computation of optimal singular control

Primers and Probe to Identify Mycobacterium Tuberculosis Complex

Methods and nucleic acids for rapid, reliable and sensitive detection of Mycobacterium tuberculosis (MTB) complex pathogen in a biological sample. Oligonucleotides are provided which amplify MTB DNA and which are useful in carrying out real time PCR of DNA obtained from formalin-fixed and paraffin-embedded tissue samples

Direct esterification of poly (ethylene glycol) with amino acid hydrochlorides

Diesters of poly (ethylene glycol) with various a amino acid hydrochlorides were synthesized using dicyclohexyl carbodiimide as coupling agent. The use of hydrochloride as amino protecting group in dicyclohexyl carbodiimide mediated condensation reactions of amino acids was demonstrated for the first time

Phase decorrelation, streamwise vortices and acoustic radiation in mixing layers

Several direct numerical simulations were performed and analyzed to study various aspects of the early development of mixing layers. Included are the phase jitter of the large-scale eddies, which was studied using a 2-D spatially-evolving mixing layer simulation; the response of a time developing mixing layer to various spanwise disturbances; and the sound radiation from a 2-D compressible time developing mixing layer

Enhancement of reactivity and increased usage of low lime class -F-fly ash-possible avenues

The low lime class-F fly ash available in the country shows high degree of variability in the quality, higher content of crystallites , lower glassy phase which accounts for lower of usage in cement and concrete . The time reactivity test used for assessing the pozzolanicity of fly ash did not always correlate with its observed reactivity in Blended cements . An alternative rapid alkali reactivity rest developed at the authors ' laboratory is illustrated in the paper. The paper also discusses the possibility of increasing the reactivity of fly ash and effect of the reactive fly ash on characteristics of PPC and concrete. The paper further discusses other avenues of fly ash utilisation, which could be categorised as low, medium and high value applications. One of such applications developed at the authors ' laboratory that merits special interest, is the Hydrogel process of clinkerisation , which has a potential for utilisation of 20-30% fly ash as a raw material in cement manufacture

Towards the prediction of supersonic jet noise predictions using a unified asymptotic approximation for the adjoint vector Green's function

In this paper we continue efforts aimed at modeling jet noise using self-consistent analytical approaches within the generalized acoustic analogy (GAA) formulation. The GAA equations show that the far-field pressure fluctuation is given by a convolution product between a propagator tensor that depends on the (true) non-parallel jet mean flow and a generalized fluctuating stress tensor that is a stationary random function of time and includes the usual fluctuating Reynolds’ stress tensor as well as enthalpy fluctuation components. Here, we focus on approximating the propagator tensor by determining an appropriate asymptotic solution to the adjoint vector Green’s function that it depends on by using an asymptotic approach at all frequencies of interest for jet noise prediction. The Green’s function is then rationally approximated by a composite formula in which the GSA (Goldstein-Sescu-Afsar, J. Fluid Mech., vol. 695, pp. 199-234, 2012) non-parallel flow Green’s function asymptotic solution is used at low frequencies and the O(1) frequency parallel flow Green’s function is used for all frequencies thereafter. The former solution uses the fact that non-parallelism will have a leading order effect on the Green’s function everywhere in the jet under a distinguished scaling in which the jet spread rate is of the same order as the Strouhal number for a slowly-diverging mean flow expansion. Since this solution, however, is expected to apply up to the peak frequency, the latter O(1) frequency Green’s function in a parallel flow must be used at frequencies thereafter. We investigate the predictive capability of the composite Green’s function for the prediction of supersonic axi-symmetric round jets at fixed jet Mach number of 1.5 and two different temperature ratios (isothermal & heated) using Large-eddy simulation data. Our results show that, in the first instance, excellent jet noise predictions are obtained using the non-parallel flow asymptotic approach, remarkably, up to a Strouhal number of 0.5. This is true for both heated and un-heated jets. Furthermore, we develop the analytical approach required to extend this solution by appropriate asymptotic approximation to O(1) frequencies

GMAW metal transfer mode identification from welding sound

© 2019 Australian Acoustical Society Annual Conference, AAS 2018. All rights reserved. Gas Metal Arc Welding (GMAW) is an arc welding process that forms an electric arc between a consumable electrode and the base metal with a shielding gas to protect the arc. In GMAW, there are various metal transfer modes such as the short circuit mode, the globular mode, the spray mode, and the rotational transfer mode, which show different arc stabilities, weld pool penetrations and spatter production. Identifying the metal transfer mode is critical for process monitoring and quality control of GMAW. In this paper, a m ethod for metal transfer mode identification from the welding sound is presented. A recorder mounted on the welder helmet is used to record the sound signals generated by GMAW under different metal transfer modes, which are analysed in both time and frequency domains. New psychoacoustic parameters based on the auditory perception of an expert welder are extracted to distinguish the metal transfer modes. The Gaussian Mixture Model (GMM) is utilised to identify the metal transfer mode from the welding sound signals and a 10-fold cross validation shows 90% recognition accuracy

Synchronization of organ pipes: experimental observations and modeling

We report measurements on the synchronization properties of organ pipes. First, we investigate influence of an external acoustical signal from a loudspeaker on the sound of an organ pipe. Second, the mutual influence of two pipes with different pitch is analyzed. In analogy to the externally driven, or mutually coupled self-sustained oscillators, one observes a frequency locking, which can be explained by synchronization theory. Further, we measure the dependence of the frequency of the signals emitted by two mutually detuned pipes with varying distance between the pipes. The spectrum shows a broad ``hump'' structure, not found for coupled oscillators. This indicates a complex coupling of the two organ pipes leading to nonlinear beat phenomena.Comment: 24 pages, 10 Figures, fully revised, 4 big figures separate in jpeg format. accepted for Journal of the Acoustical Society of Americ

On modeling pressure diffusion in non-homogeneous shear flows

New models are proposed for the 'slow and 'rapid' parts of the pressure diffusive transport based on the examination of DNS databases for plane mixing layers and wakes. The model for the 'slow' part is non-local, but requires the distribution of the triple-velocity correlation as a local source. The latter can be computed accurately for the normal component from standard gradient diffusion models, but such models are inadequate for the cross component. More work is required to remedy this situation

Molecular tailoring of thermoreversible copolymer gels: some new mechanistic insights

We earlier reported the role of hydrophobic and hydrogen bonding interactions on the transition temperatures of thermoreversible copolymer gels. We show here that the chemical structure of the hydrophobe and its concentration determine the transition temperatures [lower critical solution temperature (LCST)] and the heat of transition of new hydrophobically modified poly(N-isopropyl acrylamide) [PNIPAm] copolymer gels. The gels, prepared by copolymerizing NIPAm monomer with hydrophobic comonomers containing increasing lengths of alkyl side groups and a terminal carboxyl acid group, showed lower LCST and lower heat of transition when compared to pure PNIPAm gel. The experimental results were also compared with theoretical calculations based on a lattice-fluid-hydrogen-bond [LFHB] model. We show experimentally and theoretically that a linear correlation exists between the transition temperature and length of the hydrophobic alkyl side group. Also, in apparent contradiction to previous work, we found a reduction in the heat of transition with increasing hydrophobicity. We propose that the presence of the terminal carboxyl acid group on the hydrophobic side chain of the comonomer prevents the association of water molecules around the hydrophobe, thereby causing a reduction in the heat of transition. The LFHB model supports this argument