Development of a thermal and structural analysis procedure for cooled radial turbines

A procedure for computing the rotor temperature and stress distributions in a cooled radial turbine are considered. Existing codes for modeling the external mainstream flow and the internal cooling flow are used to compute boundary conditions for the heat transfer and stress analysis. The inviscid, quasi three dimensional code computes the external free stream velocity. The external velocity is then used in a boundary layer analysis to compute the external heat transfer coefficients. Coolant temperatures are computed by a viscous three dimensional internal flow cade for the momentum and energy equation. These boundary conditions are input to a three dimensional heat conduction code for the calculation of rotor temperatures. The rotor stress distribution may be determined for the given thermal, pressure and centrifugal loading. The procedure is applied to a cooled radial turbine which will be tested at the NASA Lewis Research Center. Representative results are given

A new multi line-cusp magnetic field plasma device (MPD) with variable magnetic field for fundamental plasma studies

One of the fundamental problems is the understanding of physics of electrostatic and electromagnetic fluctuations in multi-scale plasma turbulence. Especially so, in continuously connected plasma regions with varying degree of magnetization. Examples range from multiscale plasmas in Magnetron-like devices to astrophysical plasmas confined by magnetic dipole structures, solar wind driven collision-less and weakly collisional plasmas around Earth, to mention a few. Such plasmas are dominated by both electron scale and ion scale physics as well as finite beta effects. To investigate such processes in laboratory experiments requires excellent control of continuously connected regions of nearly zero plasma beta with finite beta regions as well as the gradient length scales of mean density and temperatures. To address some of these phenomena at laboratory scale, a new multi-line cusp configured plasma device (MPD) consisting of electromagnets with core material has been constructed with a capability to experimentally control the relative volume fractions of magnetized to unmagntized plasma volume as well as accurate control on the gradient length scales of mean density and temperature profiles. The hot tungsten cathode produced Argon plasma in the MPD has been characterised using single Langmuir probes. Argon plasma has been produced in the device over a wide range of pressure 5 x 10-5 mBar to 1 x 10-3 mBar, achieving plasma density range from 109 to 1011cm-3 and temperature in the range 1eV to 8eV

Quantum paramagnetic ground states on the honeycomb lattice and field-induced transition to N\'eel order

Motivated by recent experiments on Bi$_3$Mn$_4$O$_{12}$(NO$_3$), and a broader interest arising from numerical work on the honeycomb lattice Hubbard model, we have studied the effect of a magnetic field on honeycomb lattice spin models with quantum paramagnetic ground states. For a model with frustrating second-neighbor exchange, $J_2$, we use a Lindemann-like criterion within spin wave theory to show that N\'eel order melts beyond a critical $J_2$. The critical $J_2$ increases with a magnetic field, implying the existence of a field-induced paramagnet-N\'eel transition over a range of $J_2$. We also study bilayer model using a spin-$S$ generalization of bond operator mean field theory. We show that there is a N\'eel-dimer transition for various spin values with increasing bilayer coupling, and that the resulting interlayer dimer state undergoes a field induced transition into a state with transverse N\'eel order. Finally, we study a spin-3/2 model which interpolates between the Heisenberg model and the Affleck-Kennedy-Lieb-Tasaki (AKLT) parent Hamiltonian. Using exact diagonalization, we compute the fidelity susceptibility to locate the Neel-AKLT quantum critical point, obtain the spin gap of the AKLT parent Hamiltonian, and argue that AKLT state also undergoes field-induced Neel ordering.Comment: 8 pages, revised longer version of arXiv:1012.0316. Corrected factor of 2 error in Eq.[16], replotted Fig.[4] and revised the critical $J_c/J_1$ needed to stabilize interlayer dimer state. We thank S. V. Isakov for discussions which uncovered this erro

Computational identification and characterization of putative miRNAs in Nasonia species

MicroRNAs are important at post transcriptional regulation in eukaryotes. Nasonia genus is becoming increasingly popular model in present days due to genetic advantages it possesses over Drosophila. Nasonia species are found distributed throughout the world, expect for N. longicornis, and N. giraulti. In this study, we use the sequential method of blasting all known invertebrate miRNA genes against the Nasonia vitripennis, Nasonia longicornis, and Nasonia giraulti genomes. We identify 40, 31 and 29 putative pre-​miRNAs and mature sequences in N. vitripennis, N. giraulti and N. longicornis resp. A cross species comparison of putative miRNA sequences and their statistical characteristics reveals that there are no huge differences between the species, except for few miRNAs which are reported. We also find that the minimal folding energy index for three Nasonia species pre-​miRNA's av. is around -​0.85 ± 0.11. Further, we report that U is predominant at the 5' end of mature sequence, which being a typical characteristic of plant miRNAs. Using MiRanda, we predict nearly 471 potential sites in the N. vitripennis genome. Thus concluding our study to be the beginning of understanding the Nasonia's non coding RNAs and may play an important role in effective pest management in near future

A geometric constraint over k-dimensional objects and shapes subject to business rules

This report presents a global constraint that enforces rules written in a language based on arithmetic and first-order logic to hold among a set of objects. In a first step, the rules are rewritten to Quantifier-Free Presburger Arithmetic (QFPA) formulas. Secondly, such formulas are compiled to generators of k-dimensional forbidden sets. Such generators are a generalization of the indexicals of cc(FD). Finally, the forbidden sets generated by such indexicals are aggregated by a sweep-based algorithm and used for filtering. The business rules allow to express a great variety of packing and placement constraints, while admitting efficient and effective filtering of the domain variables of the k-dimensional object, without the need to use spatial data structures. The constraint was used to directly encode the packing knowledge of a major car manufacturer and tested on a set of real packing problems under these rules, as well as on a packing-unpacking problem

Effects on LDEF exposed copper film and bulk

Two forms of copper were exposed to the Long Duration Exposure Facility (LDEF) Mission 1 environment: a copper film, initially 74.2 plus or minus 1.1 nm thick sputter coated on a fused silica flat and a bulk piece of oxygen-free, high conductivity (OFHC) copper. The optical density of the copper film changed from 1.33 to 0.70 where exposed, and the film thickness increased to 106.7 plus or minus 0.5 nm where exposed. The exposed area appears purple by reflection and green by transmission for the thin film and maroon color for the bulk copper piece. The exposed areas increased in thickness, but only increase in the thickness of the thin film sample could be readily measured. The increase in film thickness is consistent with the density changes occurring during conversion of copper to an oxide. However, we have not been able to confirm appreciable conversion to an oxide by x-ray diffraction studies. We have not yet subjected the sample to e-beams or more abusive investigations out of concern that the film might be modified