Reliability evaluation of protective system with scheduled and unscheduled maintenance

Protective systems have two contradictory failures: one is failed-dangerous and the other is failed-safe. Scheduled maintenance is carried out to prevent these failures. Unscheduled maintenance is also carried out when the protective system shuts down the plant to be protected. This paper develops an integral equation for a statistically expected cumulative loss which is caused by the failures of the protective system and the plant. This equation represents special cases number of normal and spurious shutdowns, and hazards. An optimal scheduled maintenance interval is obtained, minimizing the expected loss.     

Thermal effects in non-adiabatic binary distillation effects of partial condensation of mixed vapors on the rates of heat and mass transfer and prediction of H. T. U.

In order to investigate thermal effects in binary distillation, theoretical approaches were made by use of a laminar boundary layer theory with uniform suction or blowing at the interface to give the following correlations for heat and mass fluxes:Nu_Gx = 0.332 Re_Gx^{$\text{1}\text{2}$}Pr_G^{$\text{1}\text{3}$}g(F(0), Pr_G)Sh_Gx(J_Axs/N_Ax) = 0.332 Re_Gx^{$\text{1}\text{2}$}Sc_G^{$\text{1}\text{3}$}g(F(0), Sc_G). From the energy balance at the vapor—liquid interface the factors which affect interfacial velocities or F(0) were discussed.Measurements of heat and mass fluxes in a vertical flat-plate wetted-wall column for the methanol-water system were made and gave a good agreement with the theory.A new method for the prediction of H_OG in binary distillation under partial condensation was proposed. The calculated H_OG's gave a fairly good agreement with the observed results.     

Correlation between oxygen-deficient center formation and volume compaction in synthetic SiO2 glass upon ArF or F2 excimer-laser irradiation

Correlations between the refractive-index change and the concentration of an oxygen-deficient center (ODC) induced by thermal treatments and laser irradiation are examined to clarify the origin of laser-induced volume compaction in synthetic SiO2 glasses. A linear correlation between them was clearly observed for thermally induced ODC, whereas no correlation was found for ArF or F2 laser irradiation. The results demonstrate that the dominant origin of laser-induced compaction is not ODC formation. Furthermore, we found that the presence of H2 in SiO2 glass had no influence on volume compaction but enhanced crack formation upon laser irradiation, a phenomenon most likely due to stress corrosion.     

Surface-plasmon-enhanced light emitters based on InGaN quantum wells

Since 1993, InGaN light-emitting diodes (LEDs) have been improved and commercialized, but these devices have not fulfilled their original promise as solid-state replacements for light bulbs as their light-emission efficiencies have been limited. Here we describe a method to enhance this efficiency through the energy transfer between quantum wells (QWs) and surface plasmons (SPs). SPs can increase the density of states and the spontaneous emission rate in the semiconductor, and lead to the enhancement of light emission by SP-QW coupling. Large enhancements of the internal quantum efficiencies (eta(int)) were measured when silver or aluminium layers were deposited 10 nm above an InGaN light-emitting layer, whereas no such enhancements were obtained from gold-coated samples. Our results indicate that the use of SPs would lead to a new class of very bright LEDs, and highly efficient solid-state light sources.     

On-column derivatization using redox activity of porous graphitic carbon stationary phase: an approach to enhancement of separation selectivity of liquid chromatography

A new on-column derivatization method based on the redox activity of porous graphitic carbon (PGC) packing materials was presented for enhancement of separation selectivity of HPLC. Two PGC packing materials were used as the solid redox agents as well as the stationary phase, and their redox activities were investigated using trans-1,2-diaminocyclohexanetetraacetate (DCTA) complexes of some metal ions as probe compounds. It was found that the redox property of PGC was modified by treating them with a solution containing a reducing agent, sodium sulfite or hydroxylammonium chloride. The original PGC packings oxidized Co(II)-DCTA to Co(III)-DCTA during elution, while the PGC treated with a reducing agent showed reduction activity converting Co(III)-DCTA to Co(II)-DCTA. These two cobalt complexes do not form their individual chromatographic zones but migrate as a single zone of their mixture on the PGC column contrary to the chromatographic behavior on a C18 bonded silica, on which Co(II)-DCTA and Co(III)-DCTA can be separated. Treatment of the PGC column with a reducing agent solution transforms the oxidative activity of the original PGC packing to a reductive one from the upper part of the column, so that the retention time of the cobalt complex can be controlled by changing the volume of the reducing agent solution to be used for treatment of the PGC column. The selective separation and determination of cobalt in a reference manganese nodule sample by the developed method was demonstrated.     

Pulse electric current sintering of alumina/nickel nanocomposites

Typical magnetically functionalized Al₂O₃/Ni nanocomposite materials were fabricated by pulse electric current sintering process. The rapid densification and various microstructures were accomplished with controlling PECS temperature. The PECSed Al₂O₃/Ni system exhibited peculiar mechanical and magnetic properties with microstructure developments. The mechanical properties of Al₂O₃/Ni nanocomposite were optimized as controlling microstructures, and fine metal dispersion into the Al₂O₃ matrix give to the various ferromagnetic properties. Electronic Publication     

Levels and enantiomeric signatures of methyl sulfonyl PCB and DDE metabolites in livers of harbor porpoises (Phocoena phocoena) from the Southern North Sea

The concentration of 26 methyl sulfonyl metabolites of polychlorinated biphenyls (MeSO2-PCBs) and of p,p'-DDE (MeSO2-DDE) were determined in 19 liver samples from harbor porpoises (Phocoena phocoena) stranded between 1997 and 2000 on the Belgian and French North Sea Coasts. The total concentration of MeSO2-PCBs ranged from 39 to 4221 ng/g lipid weight (lw) and were generally higher in adults (age > 2 yr, range 969-4,221 ng/g lw) than in juveniles (age < 2 yr, range 39-1815 ng/g lw). The concentrations of MeSO2-DDE were generally also higher in adults (21-96 ng/g lw) than in juveniles (0.5-60 ng/g lw). Congeners 3- and 4-MeSO2-CB101 were the dominating metabolites in all samples. Due to their preferential retention in the liver, the MeSO2-PCB congeners could be divided into two groups. The first group was dominated by the 3-MeSO2-PCB congeners and consisted of MeSO2-CB31, -CB49, -CB52, -CB87, and -CB101, which all have a 2,5-chlorine substitution in the phenyl ring containing the methyl sulfonyl group. The second group was dominated by the 4-MeSO2-PCB congeners and consisted of MeSO2-CB64, -CB91, -CB110, and -CB132, which all have a 2,3,6-chlorine substitution. The ratios of sum of PCBs/sum of MeSO2-PCBs and p,p'-DDE/MeSO2-DDE differed greatly between individual subjects and ranged from 15 to 419 and from 17 to 1088, respectively. The ratio between the precursor PCB congeners and their corresponding metabolites ranged from 0.6 (CB49) to 175 (CB174). Enantiomeric fractions (EFs) for MeSO2-PCB atropisomers, which include 3-MeSO2-CB132, 3-MeSO2-CB149, 4-MeSO2-CB149, 3-MeSO2-CB174, and 4-MeSO2-CB174, were also measured in 8 out of the 19 subjects. High enantiomeric excess (EF > 0.73 or EF < 0.23) for the measured chiral MeSO2-PCB congeners was found in all samples. This result may suggest that one atropisomer may be preferentially formed in harbor porpoises or that the atropisomers are retained in a highly selective manner.