Adaptive-edge search for power plant start-up scheduling

Power plant start-up scheduling is aimed at minimizing the start-up time while limiting maximum turbine-rotor stresses. A shorter start-up time not only reduces fuel and electricity consumption during the start-up process, but also increases its capability of adapting to changes in electricity demand. The start-up scheduling problem can be formulated as a function optimization problem with constraints. We have constructed an efficient and robust search model-a genetic algorithm (GA) with an enforcement operation-which forces the search along the edge of the feasible space, where the optimal schedule is supposed to exist. However, this model has to perform a prior Monte Carlo test to obtain the enforcement gains used for the implementation of the enforcement operation. In this paper, we attempt to eliminate the Monte Carlo test by proposing a self-reliant search model by introducing a GA with an adaptive enforcement operation that can generate and adapt enforcement gains during the search process. The test results of this proposed model show that the overall number of time-consuming dynamic simulations for the constraints calculation can be reduced further, thus increasing the overall efficiency of finding the optimal or near-optimal schedules     

Sol-gel preparation and properties of TiO2-P2O5 bulk glasses

Monolithic transparent and colorless, or Ti³⁺-free TiO₂-P₂O₅ glasses containing very large amounts of TiO₂ (up to 93 mol%) were successfully prepared by heat-treating the xerogels, which were made from titanium tetraisopropoxide and triethyl phosphate, through the sol-gel reaction. The density and refractive index n_632.8 nm of the sol-gel-derived glasses were higher than the melt-derived glasses of the corresponding compositions. The glasses of TiO₂ content of larger than 80 mol% seemed somewhat porous, but n_632.8 nm of these glasses was very high as 2.2-2.3. Higher density and higher n_632.8 nm than the melt-derived glasses were considered to be due to more abundance of six-fold coordinated Ti⁴⁺ ions.     

Two methods to prepare nanorings/nanoholes for the fabrication of vertical nanotransistors

A self-assembled monolayer of polystyrene (PS) beads is formed on a silicon wafer by spin-coating. After drying at 80?°C, a thin film of metal/oxide is deposited. During the deposition, the PS beads are detached due to forces such as the inner stress induced by plasma sputtering deposition, mechanical vibration, and centrifugal shearing induced by substrate rotation, resulting in nanoring/nanohole formation. Further experiments demonstrate that the PS?detachment can be controlled by scanning probe microscopy (SPM) tip manipulation. We believe this is a promising set of processes for fabricating nanodevice structures such as those of vertical nanotransistors, which provides high flexibility for nanocrystal characterizations and application for single-electron devices.     

Fluorescence-labeled peptide pI markers for capillary isoelectric focusing

Nineteen fluorescent pH standards or pI markers ranging pH 3.64-10.12 were developed for use in capillary isoelectric focusing using laser-induced fluorescence detection. Tetra- to tridecapeptides containing one cysteine residue were designed to focus sharply at their respective isoelectric points by including amino acids that contain charged side chains, the pKa values of which are close to the corresponding pI values. An iodoacetylated derivative of tetramethylrhodamine was coupled to the thiol group of cysteine to yield fluorescent pI markers. The pI values of the labeled peptides were precisely determined after isoelectric focusing on polyacrylamide gel slabs by direct measurement of the pH of the focused bands. The markers were subjected to capillary isoelectric focusing for 10-15 min in coated capillaries under conditions of low electroosmosis and were detected by means of a scanning laser-induced fluorescence detector down to a level of subpicomolar range. The markers permitted the calibration of a wide-range pH gradient formed in a capillary by fluorescence detection for the first time and should facilitate the development of highly sensitive analytical methods based on a combination of capillary isoelectric focusing and laser-induced fluorescence detection.     

Coating of polymethylmethacrylate with transparent SiO2 thin films by a sol-gel method

In order to improve the surface characteristics of polymethylmethacrylate (PMMA), oxide thin-film coatings were applied using the sol-gel dip-coating technique. The Si(OC₂H₅)₄ (TEOS), CH₃Si(OC₂H₅)₃ (MTES) or Ti(O-i-C₃H₇)₄ (TIP) was used as a starting material for SiO₂ or TiO₂ coating. The hardness of the alkoxy-derived oxide-coated PMMA was increased from 200 MPa for non-coated PMMA with increasing film thickness. By optimizing the heating conditions and the hydrolysis conditions, and by repeating the dip-coating/heating processes, a hardness as high as 325 MPa was achieved in the PMMA triply coated with the TEOS-derived SiO₂ film using the withdrawal velocity of 0.30 mms^–1 and heat treatment at 80°C. The increase in hardness with the thickness of coating film was saturated before reaching that of bulk silica-dried gel (ca. 500 MPa), which may be due to the increased porous nature of the thick films.     

Three-dimensional simulation of crack extension in brittle polycrystalline materials

Crack extension resistance in brittle polycrystals was investigated from the viewpoint of three-dimensional microcrack evolution. Even in the case of macroscopically two-dimensional cracks, inhomogeneous distribution of microscopic stress along the crack front gives rise to three-dimensional structures of extended crack surfaces. Numerical simulations of macroscopic crack extension were carried out, which showed that three-dimensional distribution of grain-by-grain thermal stress leads to a significant increase in the crack extension resistance. It was concluded that three-dimensional interpretation on the microscopic inhomogeneity is necessary for the correct comprehension of macroscopic crack extension behavior in brittle polycrystals.     

Fibrous hydroxyapatite grown in the gel system: effects of pH of the solution on the growth rate and morphology

In the preparation of fibrous hydroxyapatite (HAp), using the gel system consisting of agar gel containing calcium nitrate and over-layered (NH₄)₂HPO₄ solution, the pH of the solution was found to greatly influence the growth rate and morphology of the resultant products. In particular, a pH value of about 9–10 produced straight fibrous HAp in the shortest time. Also, the Ca/P molar ratio of the product increased with the pH value of the starting solution. The growth rate and morphology of the product were correlated to the ion species present in the solution at different pHs.     

Preparation of various DLC films by T-shaped filtered arc deposition and the effect of heat treatment on film properties

Different types of diamond-like carbon (DLC) films (ta-C, a-C, ta-C:H and a-C:H) were prepared on super hard alloy (WC-Co) substrate using a T-shape filtered arc deposition (T-FAD) system. At first, the film properties, such as structure, hydrogen content, density, hardness, elastic modulus, were measured. Ta-C prepared with a DC bias of −100 V showed the highest density (3.1 g/cm³) and hardness (70-80 GPa), and the lowest hydrogen content (less than 0.1 at. %). It was found that the hardness of the DLC film is proportional to approximately the third power of film density. The DLC films were then heated for 60 min in an electric furnace at 550 °C in N₂. Only the ta-C film hardly change its structure, although other films were graphitized. The 200-nm thick ta-C film was then heated for 60 min through the temperature range from 400 to 800 °C in N₂ with 2 vol.% of O₂ and the film structure found to be stable up to 700 °C. The substrate was oxidized at 800 °C, indicating the ta-C film had a thermal barrier function up to that temperature.     

紧凑型荧光灯的光效和寿命的改进

本文详尽地阐述了紧凑型节能荧光灯（ＣＦＬ）的发展趋势，并从理论上和实践上探讨了影响它的寿命和光效的各个因素，对ＣＦＬ灯管设计、生产工艺和新材料应用等方面，提出了一系列切实可行的改进措施。     

Current status of acute respiratory infections in children under five years of age in Nairobi, Kenya

Two hundreds and twenty-six children under five years of age with pneumonia were recruited from an urban poor area in Nairobi, Kenya, and examined for pathogens for 1 year from February 1997. One hundred and twenty-eight of the 226 patients were pathogen-positive cases. The patients under 1-year-old were 61.8% of the pathogen-positive cases. A total 192 organisms were isolated from 128 pathogen-positive patients. Streptococcus pneumoniae had the highest prevalence rate of 31.3%, followed by respiratory syncytial virus with 10.4%, Candida albicans with 9.9%, Moraxella (B) catarrhalis with 7.8%. In S. pneumoniae, 66.7% of the organism was resistant to oxacillin. It was also shown that 51.1% and 65.1% of the S. pneumoniae strains were resistant to gentamicin and trimethoprim/sulfam, respectively. From these results, it is clear that a lot of multi-drug resistant S. pneumoniae strains including penicillin-resistant S. pneumoniae were frequently detected in an urban poor area.