Application of Multi-Objective Evolutionary Optimization Algorithms to Reactive Power Planning Problem

This paper presents a new approach to treat reactive power (VAr) planning problem using multi-objective evolutionary algorithms (EAs). Specifically, strength Pareto EA (SPEA) and multi-objective particle swarm optimization (MOPSO) approaches have been developed and successfully applied. The overall problem is formulated as a nonlinear constrained multi-objective optimization problem. Minimizing the total incurred cost of the VAr planning problem and maximizing the amount of available transfer capability (ATC) are defined as the main objective functions. The aim is to find the optimal allocation of VAr devices in such a way that investment and operating costs are minimized and at the same time the amount of ATC is maximized. The proposed approaches have been successfully tested on IEEE 14 buses system. As a result a wide set of optimal solutions known as Pareto set is obtained and encouraging results show the superiority of the proposed approaches and confirm their potential to solve such a large-scale multi-objective optimization problem. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Significantly improved photoluminescence of the green-emitting β-sialon:Eu2+ phosphor via surface coating of TiO2

The β-sialon:Eu²⁺ phosphor particles were successfully coated by TiO₂ nanoparticles via the sol-gel method. The TiO₂-coated β-sialon:Eu²⁺ phosphor had a significantly improved photoluminescence (PL) performance under the 365 nm excitation, due to the localized surface plasmon resonance (LSPR) at the interface between the TiO₂ coating layer and phosphor surface. The emission intensity of the TiO₂-coated β-sialon:Eu²⁺ prepared with the titanium (IV) tetrabutoxide (Ti(OC₄H₉)₄, TTBO):H₂O = 1:0.5 volume ratio was dramatically increased by ~24%. When the preparation temperature was 500°C, it was responsible for superior PL intensity by considering the important domination factors of higher anatase content and spherical particle shape of the TiO₂ coating layer to the LSPR effect. The coating around the phosphor surface by the TiO₂ nanoparticles would be an effective technique to improve the PL efficiency of phosphor for the application in the white light-emitting diodes (LEDs), by utilizing the LSPR effect of the semiconductor coating layer, instead of conventional metal plasmonic materials.     

Phase diagram cuspidine (3CaO · 2SiO2 · CaF2)-CaF2

Equilibrium phase diagram for the system cuspidine (3CaO · 2SiO₂ · CaF₂)-CaF₂ has been studied by the quenching method and differential thermal analysis (DTA). Hermetically closed platinum capsules were used in both methods to prevent fluorine loss in the form of HF and SiF₄ by reaction of the CaF₂ with water vapor or SiO₂. Cuspidine congruently melts at 1680±2 K. The cuspidine-CaF₂ system presents a simple eutectic type of phase diagram. The eutectic composition and temperature are 46 mass pct 3CaO · 2SiO₂−54 mass pct CaF₂ and 1515±3 K, respectively.     

Synthesis of Linde type A zeolite-goethite nanocomposite as an adsorbent for cationic and anionic pollutants

Linde type A zeolite (LTA)-goethite nanocomposite was synthesized by adding sodium orthosilicate solution to goethite, followed by addition of sodium aluminate and NaOH solutions at 100 degrees C. Optimum condition at the Si addition step required for nanocomposite formation was pH 10.0 and Si/Fe=2.7. The final product composed mainly of LTA and goethite crystals. Formation of LTA-goethite nanocomposites in the final product was suggested by differences in IR spectra and SEM images between the final product and a mixture of LTA and goethite. The mixture separated into LTA and goethite components after washing with water, but the final product did not show such separation. Precipitation of silica on the surface of goethite and subsequent formation of Si-O-Fe bonds at the Si addition step contributed to formation of the LTA-goethite nanocomposite. The amount of adsorption of phosphate on the final product was more than 1.6 times the amount adsorbed on the mixture, indicating generation of synergistic effect in the LTA-goethite nanocomposite.     

Effects of exogenous mevalonic acid on sterol lipid classes in Larix kaempferi callus

In Japanese larch (Larix kaempferi (Lamb.) Carr.) calli, free sterol (FS), acylsterol (AS) and glycosylsterol, including the acylated type, were found in the proportion of 1.0:0.1:0.8. When the calli were cultured in the presence of 10 mM mevalonic acid (MVA), the content of AS, but not FS and glycosylsterol, was increased remarkably. The major component sterol in each sterol lipid class was usually sitosterol (more than 90%) with campesterol as a minor one. There were no differences on the sterol compositions between the calli cultured with or without MVA. When the calli cultured with 10 mM MVA for 6 weeks were transferred to the control medium without exogenous MVA, AS contents decreased to the level of the control calli. Thus, it was shown that sterol lipids, such as FS and glycosylsterols, with the structural functions was maintained in the constant content and the excess sterol biosynthesized from exogenous MVA was esterified to form AS for storage of sterol components.     

Photoluminescence and thermal stability of yellow-emitting Sr-α-SiAlON:Eu<Superscript>2+</Superscript> phosphor

Novel α-SiAlON:Eu²⁺-based yellow oxynitride phosphors with the formula Sr_0.375−x Eu _x ²⁺Si_12−m−n Al _m+n O _n N_16−n (m = 0.75, n = x = 0.004–0.04) have been prepared by firing the powder mixture of SrSi₂, α-Si₃N₄, AlN, and Eu₂O₃ at 2,000 °C for 2 h under 1 MPa nitrogen atmosphere. The luminescence properties, the dependence of the activator concentration of Eu²⁺ and the thermal stability of Sr-α-SiAlON:Eu²⁺ phosphor have been investigated in comparison with Ca-α-SiAlON:Eu²⁺ phosphor. Similar to Ca-α-SiAlON:Eu²⁺ phosphor, Sr-α-SiAlON:Eu²⁺ phosphor has the excitation wavelength ranging from the ultraviolet region to 500 nm, and exhibit intense yellow light. The strongest luminescence was achieved at about x = 0.02 with the emission peak at 578 nm, slightly shorter than that of Ca-α-SiAlON:Eu²⁺ phosphor at 581 nm. Temperature-dependent emission intensity of Sr-α-SiAlON:Eu²⁺ phosphor is comparable to that of Ca-α-SiAlON:Eu²⁺ phosphor. The results suggest that the different position of the emission peak for Sr- and Ca-α-SiAlON:Eu²⁺ depends on the composition and the Stokes shift, and the thermal stability is nearly independent of Sr and Ca or fixed by the network of (Si, Al)–(O, N) in α-SiAlON at the same Eu²⁺ concentration.     

Optimization of heterotrophic culture conditions for n-alkane utilization and phylogenetic position based on the 18S rDNA sequence of a thermotolerant Prototheca zopfii strain

This study reports on the optimization of the culture conditions for a thermotolerant eukaryotic algal strain, Prototheca zopfii RND16, which can effectively degrade and assimilate n-alkanes at elevated temperatures. RND16 was able to grow on 1% (v/v) n-alkanes (C14-C17) at temperatures up to 38 degrees C. This ability differs from a previous finding that P. zopfii did not grow on hydrocarbons under temperature conditions above 25 degrees C. Increasing the temperature from 25 degrees C to 30-35 degrees C resulted in an increase in the rate of n-alkanes consumption during growth of RND16 in quiescent culture. In shaking culture at 35 degrees C, RND16 removed a 1% n-alkanes mixture almost completely at the basal medium salinity within 8 d. However, an appreciable decrease in the extent of hydrocarbon utilization was observed with increasing salinity and substrate concentration in the medium. The slow consumption of the n-alkanes in the early stage of degradation at 25 degrees C was improved by supplementing 0.1% glucose. A comparative study on the nuclear small subunit rDNA (18S rDNA) sequences of three strains within the genus Prototheca revealed that both P. zopfii ATCC 30253, which utilize n-alkanes at room temperature and P. moriformis ATCC 50081, which does not assimilate n-alkanes, are closely related to RND16.     

Statistical Analysis of the Fatigue Life Distribution of Monolithic Silicon Nitride

Cyclic fatigue testing of silicon nitride ceramics was performed at a frequency of f = 150 Hz and a stress ratio of R = 0.1 using a piezoelectric bimorph fatigue device. Based on the method proposed by Fett and Munz, a fatigue crack growth diagram ( K ₁– V diagram) was estimated from fatigue lifetime distribution data. A change in the slope of the K _I– V diagram was observed. A statistical analysis for predicting the lifetime of ceramics exhibiting a transition in a K _I– V diagram was devised on the basis of this observation. Analytical results obtained with this method showed good agreement with experimental data.     

An autopsy case of the sinus of Valsalva aneurysm involved with tuberculous inflammation, leading to complete heart block

A case is presented of unruptured aneurysm of the non coronary sinus of Valsalva, causing involvement of A-V node and right coronary artery compression. The patient was a 68 year-old woman with a complaint of general fatigue. Electrocardiogram showed complete A-V block. Computed tomography showed an aneurysm of the non coronary sinus of Valsalva. A temporary pacemaker was implanted, but the patient developed respiratory failure and heart failure and died. At autopsy, macroscopically disseminated tuberculosis was noted in both lungs and kidneys. Microscopically a tuberculous inflammatory lesion extending into the A-V node was found. We report this rare case with some consideration of the literature.