Computation of optimal singular controls

Computation of optimal singular control

Stacking faults in double hexagonal close-packed crystals

Possible deviations in the regular ....ABACA.... sequence of stacking (0004) close-packed planes in the double hexagonal close-packed (d.h.c.p.) structure have been considered. Six intrinsic and one extrinsic type stacking faults have been suggested. The schemes of stacking sequences have been usefully considered in terms of the configurational symbols suggested by Jagodzinski. Extending the Hirth and Lothe procedure, estimates of theoretical fault energies are given in terms of the number of pairs of planes of separation N which are not in the shceme of perfect structure sequence. Relative fault energies have been arrived at reckoning only the first and second nearest neighbour interactions for three ideal situations: (a) the transformation energy of d.h.c.p. structure to either f.c.c. or h.c.p. structure is the same; (b) d.h.c.p. ⇌ f.c.c. transformation occurs; and (c) d.h.c.p. ⇌ h.c.p. transformation occurs

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

Comparison of antiemetic activity of palonosetron with granisetron in postoperative nausea and vomiting after laparoscopic gynaecological surgeries

Background: Granisetron is currently one of the commonly used drugs for prevention of postoperative nausea and vomiting (PONV) which is one of the most common distressing complications of laparoscopic surgeries and anesthesia. Palonosetron has emerged as alternative for PONV in adults. Thus, the study was aimed to conduct a comparison of the efficacy and adverse effects of granisetron with palonosetron to prevent PONV in patients undergoing general anaesthesia for elective laparoscopic gynaecological surgeries.Methods: This was a prospective, randomized, double blinded and a comparative study and was performed in Lokmanya Municipal Medical College and general Hospital, Sion, Mumbai, India on 60 patients undergoing elective laparoscopic gynaecologic surgeries, requiring general anaesthesia with endotracheal intubation.Results: Both granisetron 2.5 mg and palonosetron 75 µg are comparable in all respects. They have almost similar incidences in nausea, retching, vomiting and administration of rescue antiemetic at 0-2 hrs, 3 hrs, 12 hrs and 24 hrs postoperatively. The values were not significantly different. The adverse effects seen with both the drugs were not statistically significant.Conclusions: From the study this can be concluded that both the drugs are effective as prophylactic antiemetic in preventing PONV in laparoscopic gynaecological surgeries which are supposed to be highly emetogenic surgery

Evaluation of Noise Radiation Mechanisms in Turbulent Jets

Data from the direct numerical simulation (DNS) of a turbulent, compressible (Mach = 1.92) jet has been analyzed to investigate the process of sound generation. The overall goals are to understand how the different scales of turbulence contribute to the acoustic field, and to understand the role that linear instability waves play in the noise produced by supersonic turbulent jets. Lighthill’s acoustic analogy was used to predict the radiate sound from turbulent source terms computed from the DNS data. Preliminary computations (for the axisymmetric mode of the acoustic field) showgood agreement between the acoustic field determined from DNS and acoustic analogy. Further work is needed to refine the calculations and investigate the source terms. Work was also begun to test the validity of linear stability wave models of sound generation in supersonic jets. An adjoint-based method was developed to project the DNS data onto the most unstable linear stability mode at different streamwise positions. This will allow the evolution of the wave and its radiated acoustic field, determined by solving the linear equations, to be compared directly with the evolution of the near and far-field fluctuations in the DNS

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

Fuzzy -Fold BCI-Positive Implicative Ideals in BCI-Algebras

We consider the notion of fuzzy -fold positive implicative ideals in BCI-algebras. We analyse many properties of fuzzy -fold positive implicative ideals. We also establish an extension properties for fuzzy n-fold positive implicative ideals in BCI-algberas. This work generalizes the corresponding results in the crisp case

A two-species continuum model for aeolian sand ripples

We formulate a continuum model for aeolian sand ripples consisting of two species of grains: a lower layer of relatively immobile clusters, with an upper layer of highly mobile grains moving on top. We predict analytically the ripple wavelength, initial ripple growth rate and threshold saltation flux for ripple formation. Numerical simulations show the evolution of realistic ripple profiles from initial surface roughness via ripple growth and merger.Comment: 9 pages, 3 figure

Computational issues and algorithm assessment for shock/turbulence interaction problems

The paper provides an overview of the challenges involved in the computation of flows with interactions between turbulence, strong shockwaves, and sharp density interfaces. The prediction and physics of such flows is the focus of an ongoing project in the Scientific Discovery through Advanced Computing (SciDAC) program. While the project is fundamental in nature, there are many important potential applications of scientific and engineering interest ranging from inertial confinement fusion to exploding supernovae. The essential challenges will be discussed, and some representative numerical results that highlight these challenges will be shown. In addition, the overall approach taken in this project will be outlined