Pressure loading of detonation waves through 90-degree bend in high pressure H2–O2–N2 mixtures

Detonation experiments are conducted to investigate the detonation wave behavior in steam pipelines of boiling water reactors. Accumulated gases in BWRs are stoichiometric hydrogen/oxygen mixtures diluted with steam at 7 MPa. In the experiment, flammable gas mixture diluted with nitrogen at room temperature and up to 5 MPa is used to achieve equivalent detonation condition. Two test pieces are used, one is straight tube and the other is 90-degree bend. No initial pressure dependency in detonation wave behavior is observed in the experiments. However, in the straight tube tests, detonation velocities higher than theoretical values are measured when the initial pressures are greater than 2.3 MPa. This result is considered as attribution of real gas effect. In the 90-degree bend experiments, pressure time histories reveal pressure loads greater than the straight tube portion at two locations. One is a high pressure peak at the extrados of the bend and the other is a double pressure peak just downstream of the bend outlet. Second pressure peak just downstream of the bend outlet is due to transverse wave propagation. Additionally, the largest impulse is observed not at the extrados of the bend but at the intrados of bend outlet. These results show the importance of more investigations on transverse wave behaviors in failure potential evaluation.     

Initial step of anthracene‐sensitized photoacid generation from diphenyliodonium hexafluorophosphate in an epoxy matrix studied by steady‐state and laser‐flash photolyses

The anthracene‐sensitized photodecomposition of diphenyliodonium hexafluorophosphate was studied in an epoxy matrix. From steady‐state photolysis, the generation of protons, which are considered to be the actual initiators of the polymerization of epoxides, was confirmed. In addition, 9‐phenylanthracene was detected as a main product from anthracene. From time‐resolved laser‐flash photolysis, a broad absorption band with a peak at about 500 nm was observed that was thought to be due to the precursor of 9‐phenylanthracene. On the basis of these results, we propose electron transfer from anthracene in the excited singlet state to the diphenyliodonium cation as the initial step of photoacid generation. This process is followed by fast chemical reactions, which generate 9‐phenylanthracene and protons, and back electron transfer from the diphenyliodine radical to the anthracene cation radical. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2937–2946, 2001     

A diode-pumped, self-starting, all-solid-state self-mode-locked Cr:LiSGAF laser

In this paper, a self-starting, diode-pumped self-mode-locked Cr:LiSGAF laser, which produced a stable pulse train of 45 fs duration with about 20 mW-average power at the repeated rate of 90 MHz, was presented. Self-mode-locked operation can be obtained whether there is the semiconductor saturable absorber mirror (SESAM) in the Cr:LiSGAF laser cavity or not, and with the SESAM in the cavity, the self-mode-locked operation could self-start. The shortest pulses, as short as 38 fs, which were not very stable, were obtain with the SESAM in the cavity.     

Cu chemistry of YBa2Cu3O6+x investigated by nuclear quadrupole resonance

The nuclear quadrupole resonance (NQR) technique has been utilized to characterize the local oxygen coordination of inequivalent Cu sites in YBa₂Cu₃O_6+x(0 ≤ x ≤ 0.91). Essentially, four distinct NQR lines which correspond to 2, 3,4 oxygen coordinated Cu sites in the Cu-O chains and 5 oxygen coordinated Cu sites in the Cu-O planes have been observed. The zero-field NQR frequencies of these are centered at about 30.1, 24.0, 22.0 and 31.5 MHz for ⁶³Cu, respectively. For the antiferromagnetic ordered state (x ≤ 0.3), antiferromagnetic nuclear resonance (AFNR) has been observed at 90 MHz with quadrupole splittings associated with the moment-bearing Cu sites in the Cu-O planes. The relative intensities of these resonance lines depend on the oxygen content, and this gives us a microscopic understanding of the Cu chemistry of this system.     

Large‐scale SPH simulations of droplet impact onto a liquid surface up to the consequent formation of Worthington jet

In this study, the whole process of liquid droplet impact onto a liquid surface up to the consequent formation of the central column was simulated using the smoothed particle hydrodynamics method (SPH), and compared with an experiment using a high‐speed video camera. The surface tension tensor for the particle‐based expression was adequately included as the gradient of the surface tension and that enabled the simulation leading to the formations of crater and crown as well as the consequent central column. The simulated time series of the crater depth and diameter and crown height corresponded quantitatively well with the experimental result up to the rebound motion while discrepancies remained as a lower central column height in the simulation, and this seemed to be ascribed to the difficulty in realizing the complex surface structure that inevitably appeared in the fast rebound motion. Copyright © 2009 John Wiley & Sons, Ltd.     

Openness of momentum maps and persistence of extremal relative equilibria

We prove that for every proper Hamiltonian action of a Lie group G in finite dimensions the momentum map is locally G-open relative to its image (i.e. images of G-invariant open sets are open). As an application we deduce that in a Hamiltonian system with continuous Hamiltonian symmetries, extremal relative equilibria persist for every perturbation of the value of the momentum map, provided the isotropy subgroup of this value is compact. We also demonstrate how this persistence result applies to an example of ellipsoidal figures of rotating fluid. We also provide an example with plane point vortices which shows how the compactness assumption is related to persistence.     

Novel hydrogen peroxide sensors based on peroxidase-carrying poly[pyrrole-co-[4-(3-pyrrolyl)butanesulfonate]] copolymer films.

Amperometric hydrogen peroxide biosensors were fabricated by incorporating horseradish peroxidase (HRP) into poly[pyrrole-co-[4-(3-pyrrolyl)butanesulfonate]] (Py-PS) copolymer films deposited on an SnO2 electrode surface by electropolymerization. The HRP/Py-PS electrodes exhibited an extended dynamic range and a markedly improved operational and storage stability, compared with HRP-incorporated polypyrrole (PPy) electrodes prepared under similar conditions. The linear range was expanded from 10(-7)-10(-4) M to 10(-7)-10(-3) M H2O2. In about 80 measurements over three weeks, the HRP/Py-PS electrode retained 60% of its initial response, while the HRP/PPy electrode almost completely lost activity. The influence of the electrodeposition solution pH on the sensor response was also investigated. Our results suggest that an expansion of the linear range and an enhancement of lifetime are due to electrostatic interactions of HRP with a negatively-charged Py-PS copolymer.     

Implementing an efficient minimum capacity cut algorithm

In this paper, we present an efficient implementation of theO(mn + n ² logn) time algorithm originally proposed by Nagamochi and Ibaraki (1992) for computing the minimum capacity cut of an undirected network. To enhance computation, various ideas are added so that it can contract as many edges as possible in each iteration. To evaluate the performance of the resulting implementation, we conducted extensive computational experiments, and compared the results with that of Padberg and Rinaldi's algorithm (1990), which is currently known as one of the practically fastest programs for this problem. The results indicate that our program is considerably faster than Padberg and Rinaldi's program, and its running time is not significantly affected by the types of the networks being solved.Corresponding author.