A technique to measure wavenumber mismatch between quadratically interacting modes

Nonlinear energy cascade by means of three-wave resonant interactions is a characteristic feature of transitioning and turbulent flows. Resonant wavenumber mismatch between these interacting modes can arise from the dispersive characteristics of the interacting waves and from spectral broadening due to random effects. In this paper, a general technique is presented to estimate the average level of instantaneous wavenumber mismatch, k=k _m -k _i -k _j , between components whose frequencies obey the resonant selection condition, f _m -f _i-f _j =o. Cross-correlation of the auto-bispectrum is used to quantify the level of mismatch. The concept of bispectrum coupling coherency is introduced to determine the confidence level in the wavenumber mismatch estimates. These techniques are then applied to measure wavenumber mismatch in the transitioning field of a plane wake. The results show that the average of the instantaneous mismatch between the actual interacting modes k _m -k _i -k _j is in general not equal to the mismatch between the average wavenumbers of each interacting mode k _m -k _i -k _j .The authors wish to express their gratitude to Dr. Christoph P. Ritz of the Swiss National Science Foundation for his comments in the preparation of this work. This paper is based in part upon work supported by the Texas Advanced Research Program under Grant No. ARP 3280, and in part by the National Science Foundation under Grant No. MSM-82112O5. The digital signal processing techniques were developed under the Office of Naval Research under contract number N00014-88-k-0638     

Measurement of isomeric yield ratios for 93Nb(??,4n)89m,gNb and natMo(??,xn1p)95m,gNb reactions with 50-, 60-, and 70-MeV bremsstrahlung

We measured the isomeric yield ratios for the photonuclear reactions of ⁹³Nb(??,4n)^89m,gNb and ^natMo(??,xnp)^95m,gNb by using the activation method. The high-purity ⁹³Nb and ^natMo metallic foils in disc shape were irradiated with uncollimated bremsstrahlung beams of 50-, 60-, and 70-MeV generated from an electron linear accelerator in Pohang Accelerator Laboratory. The induced activities in the irradiated foils were measured by the high-resolution ??-ray spectrometry with a calibrated high-purity Germanium (HPGe) detector coupled to a PC-based 4?K multichannel analyzer. The reaction ⁹³Nb(??,4n)^89m,gNb was studied for the first time which has no comparable literature data. The result of ^95m,gNb isomeric pair was measured based on (??,p), (??,np), and (??,2np) reactions which is the first measurement at the intermediate energy region of 50?C70-MeV with a ^natMo target.     

Computation of compaction in compressible granular material

Equations modeling compaction in a mixture of granular high explosive and interstitial gas are solved numerically. Both phases are modeled as compressible, viscous fluids. This overcomes well known difficulties associated with computing shock jumps in the inviscid version of the equations, which cannot be posed in a fully conservative form. One-dimensional shock tube and piston-driven compaction solutions compare favorably with experiment and known analytic solutions. A simple two-dimensional extension is presented.     

Functional model of oxomolybdoenzymes: Synthesis and characterization of a molybdenum complex with sulphur and pterin ligands exhibiting saturation kinetics with pyridine N-oxide

Redox reaction between 6-acetonylisoxanthopterin (H₂pte) and [Mo^VIO₂ (ssp)] [ssp = anion of 2-(salicylideneamino) benzenethiol] in CH₃OH-C₂H₅OH medium produces a new mixed ligand compound [Mo^IV (ssp) (Hpte) (OCH₃)] (1). It has been characterized by elemental analysis, ESMS data, UV-Vis, IR,¹HNMR (1D and 2D) spectroscopy and cyclic voltammetry. Kinetics of formation of this compound as well as that of its reaction with pyridine N-oxide have been followed spectrophotometrically. Both the reactions follow substrate saturation kinetics and involve metal-centred oxygen atom transfer process. Large negative values of entropy of activation indicate the operation of associative mechanism.     

The Role of the Pars Recta and Pars Oblique of Cricothyroid Muscle in Speech Production

To evaluate the functional difference of the pars recta and pars oblique during speech production, the electromyographic activities of these muscles were measured in thyroidectomized patients. The hooked wire electrodes were inserted into the normal side of the bellies of the pars recta and pars oblique bundles. Two kinds of sentences were used to obtain pitch changes, a simple interrogative sentence and a complex sentence with stress contrasts. The pars recta and pars oblique were simultaneously activated for initial lengthening and tensing of vocal folds to produce speech. The pars oblique might be initially more active than the pars recta at the initial task of speech and the pars recta might be more active at the pitch elevation in the interrogative sentence and the stress contrast of the complex sentence. The maximum electromyographic activity range of the pars recta and pars oblique seemed to be nearly equal. These results demonstrated that the patterns of electrical activities of the two bellies are different during speech and the combined activities of the pars recta and pars oblique are important in the adjustment of the vocal fold length during speech.