Application of the finite element method to minimum mass design of a bar with two specified natural frequencies

In the first part of the present paper, a problem of minimum mass design of a bar with two specified longitudinal natural frequencies is treated. A discussion is given to whether the bar thus optimally designed has any other natural frequencies between the two specified natural frequencies or not. In the second part of the paper, an extension is made to a problem in which some inequality constraints on the mass distribution are also imposed. Optimality conditions for the inequality constraints are presented.These problems are formulated by the use of the finite element method. The Newton-Raphson method is employed to solve the necessary conditions for optimality. A computational algorithm is developed. Some numerical results are shown.     

Post-irradiation studies on knock-out and pseudo-recoil releases of fission products from fissioning UO2

By using post-irradiation techniques, in-pile releases of ¹³³Xe, ^85mKr, ⁸⁸Kr, ⁸⁷Kr and ¹³⁸Xe from UO₂ fissioning at low temperatures below about 200° C are studied: these are analyzed into a time-dependent knock-out and time-independent pseudo-recoil releases. For the latter, a “self knock-out” mechanism is proposed: when a fission fragment loses thoroughly its energy near the UO₂ surface and stops there, it will knock out the surface substances and accordingly the fragment (i.e. the fission product) will be released. The effective thickness of the layer where the self knock-out occurs is found to be ~7Å. As for the knock-out release, the following is estimated from its dependence on various factors: the knock-out release of fission products occurs from the surface layer with the effective thickness of ~20Å: the shape of UO₂ matrix knocked out by one fission fragment passing through the surface is equivalent to a cylinder ~32Å diameter by ~27Å thick, (i.e. the knock-out coefficient for UO₂ is ~660 uranium atoms per knock-out event). On the basis of the above estimations, the conclusions derived from the past in-pile studies of fission gas releases are evaluated.     

Modulation characteristics of 1.3 ?m buried-stripe InGaAsP laser up to 2 Gbit/s data rates

Modulation experimenting on a buried-stripe (b.s.) InGaAsP laser emitting at 1.3 ?m was carried out up to 2 Gbit/s. The b.s. laser is free from relaxation oscillation, which degrades modulated optical pube waveforms, especially at high data rates. The repeater gain of 1.6 Gbit/s transmission systems is improved by 9 dB compared with previously reported experiments. Modulation characteristics up to 2 Gbit/s are reported.     

LanV, a bifunctional enzyme: aromatase and ketoreductase during landomycin A biosynthesis

LanV is involved in the biosynthesis of landomycin A. The exact function of this enzyme was elucidated with combinatorial biosynthesis by using Streptomyces fradiae mutants that produce urdamycin A. After expression of lanV in S. fradiae DeltaurdM, which is a mutant that accumulates rabelomycin, urdamycinon B and urdamycin B were found to be produced by the strain. This result indicates that LanV is involved in the 6-ketoreduction of the angucycline core, which preceeds a 5,6-dehydration reaction. 9-C-D-Olivosyltetrangulol was also produced by this strain; this demonstrates that LanV catalyses the aromatization of ring A of the angucycline structure. Coexpression of lanV and lanGT2 in S. fradiae AO, a mutant that lacks all four urdamycin glycosyltransferases, resulted in the production of tetrangulol and the glycoside landomycin H, both of which have an aromatic ring A. As glycosylated angucyclines were not observed after expression of lanGT2 in the absence of lanV, we conclude that LanGT2 needs an aromatized ring A for substrate recognition.     

Growth control of ice crystals by poly(vinyl alcohol) and antifreeze protein in ice slurries

Effect of poly(vinyl alcohol) (PVA) in inhibiting an increase in ice crystal size in isothermal ice slurries was investigated, and then compared with the effect of an antifreeze protein (AFP), NaCl, and three other polymers, namely, poly(ethylene glycol), poly(vinyl pyrrolidone), and poly(acrylic acid). First, ice slurries, in which the initial size distribution of ice crystals was known, were isothermally preserved for given periods of time (typically 300 min) in the presence of PVA, AFP type I, NaCl, or the other three polymers. Then, the average size of the ice crystals was measured using image processing. Both the PVA and AFP type I completely inhibited the increase in ice crystal size at such low concentrations that the melting temperature of the solution was , whereas NaCl and the other three polymers clearly increased the ice crystal size due to Ostwald ripening. This inhibition effect of PVA and AFP type I was caused by thermal hysteresis, which is often taken as the primary manifestation of non-equilibrium antifreeze activity of these additives and defined as the difference between the melting temperature and non-equilibrium freezing temperature at which ice crystals start to grow in solution. The increase in ice crystal size was inhibited when the thermal hysteresis surpassed the driving potential for Ostwald ripening. Using PVA, which exhibits thermal hysteresis, is a novel technique to completely inhibit the increase in ice crystal size in isothermal ice slurries.     

H2O-tolerant monolithic catalysts for preferential oxidation of carbon monoxide in the presence of hydrogen

Pt–Fe/mordenite (4 wt% Pt–0.5 wt% Fe) powder catalysts were wash-coated onto ceramic straight-channel monoliths by using silica- and/or alumina-sol as a binder, and were evaluated for the preferential oxidation of carbon monoxide (PROX) in a hydrogen-rich gas. In a synthetic reformate gas (1% CO, 1% O₂, 5% H₂O, 20% CO₂, and balance H₂), the CO concentration was reduced to less than 20 ppm at temperatures ranging from 100 to 130 °C. After a certain period of the PROX reaction, condensation of H₂O in the pores of the mordenite-support occurred over the monolithic catalyst, which was wash-coated with alumina-sol, in the lower temperature range (100–120 °C), resulting in a rapid increase in CO concentration. The monolithic catalyst wash-coated with silica-sol, however, showed an excellent tolerance against H₂O condensation and offered a stable catalytic performance, maintaining a CO concentration of ca. 20 ppm for 200 h. The H₂O-tolerant characteristic was attributed to the relatively small adsorption amount of H₂O over the silica-modified monolithic catalyst.     

Application of step‐response test for evaluation of uncertainty of standard measuring system for lightning‐impulse high voltage

In evaluating the uncertainty of the standard measuring system for lightning‐impulse high voltages, which is composed of a standard voltage divider, a digital recorder, and calibrators, step‐response tests of the standard voltage divider may be useful. In this paper, a convolution algorithm is employed to calculate the output impulse voltage waveforms from measured step‐response waveforms. The uncertainties of peak‐value measurement due to the influence of the nominal epoch, uncertainty of the peak‐value measurement due to dispersion of the AC scale factor, and uncertainty of the virtual front‐time measurement due to long‐term stability are evaluated. Furthermore, the error of the virtual front time of the output waveforms is discussed. The front part of the step‐response waveform, t≤ T₃₀%, does not influence the error of the virtual front time. Therefore, for the standard voltage divider, the step‐response parameters, that is, the experimental response time, partial response time, settling time, and overshoot, have almost nothing to do with the error of the virtual front time. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 180(2): 24–32, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21279     

Optical Nanoscale Pool‐on‐Surface Design for Control Sensing Recognition of Multiple Cations

General design of optical chemical nanosensors is needed to develop efficient sensing systems with high flexibility, and low capital cost for control recognition of toxic analytes. Here, we designed optical chemical nanosensors for simple, high‐speed detection of multiple toxic metal ions. The systematic design of the nanosensors was based on densely patterned chromophores with intrinsic mobility, namely, “building‐blocks” onto three‐dimensional (3D) nanoscale structures. The ability to precisely modify the nanoscale pore surfaces by using a broad range of chromophores that have different molecular sizes and characteristics enables detection of multiple toxic ions. A key feature of this building‐blocks design strategy is that the surface functionality and good adsorption characteristics of the fabricated nanosensor arrays enabled the development of “pool‐on‐surface” sensing systems in which high flux of the metal analytes across the probe molecules was achieved without significant kinetic hindrance. Such a sensing design enabled sensitive recognition of metal ions up to sub‐picomolar detection limits (～10^?11 mol dm^?3), for first time, with rapid response time within few seconds. Moreover, because these sensing pools exhibited long‐term stability, reversibility and selectivity in detecting most pollutant cations, for example, Cr(VI), Pb(II), Co(II), and Pd(II) ions, they are practical and inexpensive. The key result in our study is that the pool‐on‐surface design for optical nanosensors exhibited significant ion‐selective ability of these target ions from environmental samples and waste disposals.     

Size dependence of THz region dielectric properties for barium titanate fine particles

Barium titanate (BaTiO₃) crystallites with various particle sizes from 22 to 500 nm were prepared by the two-step thermal decomposition method of barium titanyl oxalate. Various characterizations revealed that these particles were impurity-free, defect-free, dense BaTiO₃ particles. The powder dielectric measurement clarified that the dielectric constant of BaTiO₃ particles with a size of around 58 nm exhibited a maximum of over 15,000. To explain this size dependence, the THz region dielectric properties of BaTiO₃ fine particles, especially Slater mode frequency, were measured using the far infrared (FIR) reflection method. As the result, the lowest Slater mode frequency was obtained at 58 nm. This tendency was completely consistent with particle size dependence of the dielectric constant.