Analysis of machining characteristics in electrochemical etching using laser masking

Electrochemical etching using laser masking (EELM), which is a combination of laser beam irradiation for masking and electrochemical etching, allows the micro fabrication of stainless steel without photolithography technology. The EELM process can produce various micro patterns and multilayered structures. In this study, the machining characteristics of EELM were investigated. Changes in characteristics of recast layer formation and the protective effect of the recast layer according to the laser masking conditions and electrochemical etching conditions were investigated by field emission scanning electron microscopy (FE-SEM), focused ion beam (FIB) and X-ray photoelectron spectroscopy (XPS). The oxidized recast layer with a thickness of 500 nm was verified to yield a superior protective effect during electrochemical etching and good form accuracy. Finally, micro patterns and structures were fabricated by EELM.     

Transition of metallic and insulating Ti sub-oxides in bipolar resistive switching TiO x /TiO y frameworks due to oxygen vacancy drifts

Bilayer TiO _x (oxygen rich, region 1)/TiO _y (oxygen poor, region 2) homojunctions were evaluated as resistive switching elements where the TiO _x layers were designed with various oxygen contents. Depending on the oxygen ion content, controllable memory windows were observed by changing the off-state (high-resistance state), while the on-state (low resistance) was left with very little change. The cause of the variable memory windows in resistive switching phenomena appears to be the increasing amounts of movable oxygen ions between the TiO _x and TiO _y layers. In addition, the X-ray photoelectron spectroscopy measurements of the initial, low resistance, and high-resistance states in the homojunctions demonstrated the possible change of metallic and insulating Ti sub-oxide phases at the interfaces and oxygen ion rich region due to the migration of oxygen ions.     

Accumulative uncertainties in the quantitative evaluation of signals from fish

The accuracy of the acoustical method used in quantitative assessment of fish populations is mainly dependent on the measurement of the time varying echo signals and the evaluation of the fish target strengths. Various types of accumulative uncertainties involved in the measurement and estimation of different physical variables associated with the two way propagation of the acoustic signals between the fish target and the echo sounder system are investigated in this paper. The accumulative uncertainties are so high that an attempt to obtain an accuracy of, say, 0.5 dB in the conventional target strength calibration routines would have little meaning for any practical fishstock assessment survey. A new dynamic calibration method is proposed and discussed.     

Structure of ionic and electronic defects in cobalt bronze NaxCoO2

Thermogravimetric and electrical conductivity measurements of cobalt bronze Na_0.7CoO₂ have been carried out in the temperature range 990-670 K and over oxygen pressures from 100 to 10 kPa. It has been stated that in addition to defects in the sodium sublattice (sodium vacancies and electron holes) in this material there are also ionic defects in the oxygen-cobalt sublattice. The proposed method of analysis of defect type, based on the calculation of derivative of the function ln (def) = f(lnP_O2) shows the existence of cobalt ions Co³⁺ in the sodium sites.     

Generalized variational inequalities with generalized coercivity conditions

Some results due to Fang and Peterson on generalized variational inequalities in the space ? ⁿ are extended to infinite-dimensional spaces. Theorems on the existence of solutions of such inequalities under generalized coercivity conditions are obtained.     

Strong factorization property of Macdonald polynomials and higher-order Macdonald’s positivity conjecture

We prove a strong factorization property of interpolation Macdonald polynomials when q tends to 1. As a consequence, we show that Macdonald polynomials have a strong factorization property when q tends to 1, which was posed as an open question in our previous paper with Féray. Furthermore, we introduce multivariate q, t-Kostka numbers and we show that they are polynomials in q, t with integer coefficients by using the strong factorization property of Macdonald polynomials. We conjecture that multivariate q, t-Kostka numbers are in fact polynomials in q, t with nonnegative integer coefficients, which generalizes the celebrated Macdonald’s positivity conjecture.     

Determination of mercury species by the diffusive gradient in thin film technique and liquid chromatography – atomic fluorescence spectrometry after microwave extraction

A diffusive gradient in thin films technique (DGT) was combined with liquid chromatography (LC) and cold vapor atomic fluorescence spectrometry (CV-AFS) for the simultaneous quantification of four mercury species (Hg²⁺, CH₃Hg⁺, C₂H₅Hg⁺, and C₆H₅Hg⁺). After diffusion through an agarose diffusive layer, the mercury species were accumulated in resin gels containing thiol-functionalized ion-exchange resins (Duolite GT73, and Ambersep GT74). A microwave-assisted extraction (MAE) in the presence of 6 M HCl and 5 M HCl (55 °C, 15 min) was used for isolation of mercury species from Ambersep and Duolite resin gels, respectively. The extraction efficiency was higher than 95.0% (RSD 3.5%). The mercury species were separated with a mobile phase containing 6.2% methanol + 0.05% 2-mercaptoethanol + 0.02 M ammonium acetate with a stepwise increase of methanol content up to 80% in the 16th min on a Zorbax C18 reverse phase column. The LODs of DGT–MAE–LC–CV-AFS method were 38 ng L⁻¹ for CH₃Hg⁺, 13 ng L⁻¹ for Hg²⁺, 34 ng L⁻¹ for C₂H₅Hg⁺ and 30 ng L⁻¹ for C₆H₅Hg⁺ for 24 h DGT accumulation at 25 °C.     

KINETICS OF SEEDED EMULSION POLYMERIZATION OF STYRENE UNDER BATCH AND CONTINUOUS MONOMER ADDITION CONDITIONS

Kinetics of seeded emulsion polymerization of styrene at 90°C was studied, n calculated using both Rp = kpCnN/NA and n - (a/4) (I₀(a)/I₁(a)) agreed very well with each other and indicated a significant gel effect even under relatively monomer-rich conditions. However, significant deviation of n values occurred in starved runs with slower monomer addition. Under these conditions, diffusion of monomer through the polymer matrix became rate limiting. A monomer-rich shell as the main polymerization site was deduced from the rate data and the thickness of the shell was estimated     

Measurement of isomeric yield ratios for the natHo(γ,xn)164m,g;162m,gHo reactions in the bremsstrahlung energy region from 45 to 65 MeV

We have measured the isomeric yield ratios for the ^164m,gHo and the ^162m,gHo isomeric pairs formed via photonuclear reactions ¹⁶⁵Ho(γ,n)^164m,gHo and ¹⁶⁵Ho(γ,3n)^162m,gHo in the bremsstrahlung energy region from 45 to 65 MeV in steps of ?E = 5 MeV by the activation method. The induced γ-activities of the irradiated holmium foils were measured by a coaxial high-purity germanium detector coupled to a PC-based multichannel analyzer. In order to improve the accuracy of the experimental results the necessary corrections were made. The experimental results at bremsstrahlung energies of 45, 50, 55, 60, and 65 MeV are 0.408 ± 0.027, 0.413 ± 0.027, 0.427 ± 0.029, 0.452 ± 0.032, and 0.448 ± 0.031 for the ^164m,gHo isomeric pair, and 0.587 ± 0.041, 0.624 ± 0.044, 0.652 ± 0.045, 0.637 ± 0.045, and 0.668 ± 0.046 for the ^162m,gHo isomeric pair, respectively. The present results are the first measurements at bremsstrahlung energies just above the giant dipole resonance region. The obtained results confirm the dependence of isomeric ratios on the incident photon energy as observed in some earlier experiments.