Optimal boiler control through real-time monitoring of unburned carbon in fly ash by laser-induced breakdown spectroscopy

A laser-induced breakdown spectroscopy (LIBS) technique has been applied for detection of unburned carbon in fly ash, and an automated LIBS unit has been developed and applied in a 1000-MW pulverized-coal-fired power plant for real-time measurement, specifically of unburned carbon in fly ash. Good agreement was found between measurement results from the LIBS method and those from the conventional method (Japanese Industrial Standard 8815), with a standard deviation of 0.27%. This result confirms that the measurement of unburned carbon in fly ash by use of LIBS is sufficiently accurate for boiler control. Measurements taken by this apparatus were also integrated into a boiler-control system with the objective of achieving optimal and stable combustion. By control of the rotating speed of a mill rotary separator relative to measured unburned-carbon content, it has been demonstrated that boiler control is possible in an optimized manner by use of the value of the unburned-carbon content of fly ash.     

Fourier synthesis image reconstruction by use of one-dimensional position-sensitive detectors

An improvement of Fourier synthesis optics for hard x-ray imaging is described, and the basic performance of the new optics is confirmed through numerical simulations. The original concept of the Fourier synthesis imager utilizes nonposition-sensitive hard x-ray detectors coupled to individual bigrid modulation collimators. The improved concept employs a one-dimensional position-sensitive detector (such as a CdTe strip detector) instead of the second grid layer of each bigrid modulation collimator. This improves the imaging performance in several respects over the original design. One performance improvement is a two-fold increase in the average transmission, from 1/4 to 1/2. The second merit is that both the sine and cosine components can be derived from a single grid-detector module, and hence the number of imaging modules can be halved. Furthermore, it provides information along the depth direction simultaneously. This in turn enables a three-dimensional imaging hard x-ray microscope for medical diagnostics, incorporating radioactive tracers. A conceptual design of such a microscope is presented, designed to provide a field of view of 4 mm and a spatial resolution of 400 microm.     

Characterization of polymer films using a slow positron beam

Polymer structures have been investigated using positron annihilation lifetime spectroscopy (PALS) with a slow positron beam as well as a conventional radioactive source (²²Na). The properties of the free volume holes near the polymer surface were studied as a function of the positron implantation energy. The longest lifetime was associated with ortho-positronium (o-Ps) annihilation in the free volume holes. In polytetrafluoroethylene film, the lifetime of o-Ps was observed to decrease with increasing positron implantation depth, and a significant change in the o-Ps lifetime was found at a short distance (about 10 nm) from the surface, while its intensity increased. This result implies that near the polymer surface the free volume holes become larger that in the bulk. The effect of temperature on the polymer sub-surface layers was also studied. For high molecular weight polystyrene, the glass transition temperature for the sub-surface was lower than that for the bulk and thermal expansion coefficient of the sub-surface layers was found to be larger than the bulk value. Electronic Publication     

Formation of Ti<Subscript>3</Subscript>SiC<Subscript>2</Subscript> from Ti-Si-TiC powders by pulse discharge sintering (PDS) technique

Ti/Si/TiC powder mixture with molar ratios of 2:2:3 were sintered at various temperatures from 700–1300 °C for 15 min by PDS technique. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used for the evaluation of phase composition in different samples for the understanding of the sintering mechanism for this system. Results showed that Ti₅Si₃ formed as the intermediate phase during sintering. The reaction between Ti₅Si₃ and TiC as well as Si induces the formation of Ti₃SiC₂, and TiSi₂ appears as the byproduct in this process. At temperature above 1000 °C, TiSi₂ reacts with TiC to form Ti₃SiC₂. High Ti₃SiC₂ phase content bulk material can be synthesized at 1300 °C for 15 min.     

Surface wetting phenomena of plasma polymer-coated sheets of poly(l-lactic acid)/poly(butylene succinate)

Water-repellent surfaces were fabricated on blend sheets of poly(l-lactic acid)/poly(butylene succinate) with various blending ratios by the successive processing; (1) plasma etching, followed by (2) the hydrophobic plasma polymer coating. Rough morphology was formed effectively on the mosaic structured surface of blend sheets via the oxidative etching, and advanced water repellency was achieved after the thin membrane coating was synthesized with a hydrophobic plasma polymer coating by use of hexamethyldisiloxane or hexamethyldisilazane. High water repellency is expressed through the columnar hair-like structured model, where the air-water surface interaction in the voids is taken into account.     

Growth and proliferation of bone marrow mesenchymal stem cells affected by type I collagen,fibronectin and bFGF

Bone marrow mesenchymal stem cells (MSCs) can differentiate into a various type cells. It has been identified that MSCs are an attractive cell source for various tissue engineering and play a central role in the repair and regeneration of mesenchymal tissue. Expansion of MSCs in vitro is prerequisite for their applications in tissue engineering. In this study, we evaluated the effects of type I collagen (Col I), fibronectin (Fn) and basic fibroblast growth factor (bFGF) on growth and proliferation of human MSCs (hMSCs) by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphe-nyltetra-zolium bromide (MTT) assay. Our results show that low-dose bFGF (5–20 ng/ml) has a promotion effects for growth and proliferation of hMSCs. The proliferation, however, was back to the level similar to the control one (without bFGF treatment) after exposure to high-dose bFGF (40 ng/ml). Application of Col I, coating on the silicone surface or mixed with medium directly, yielded an obvious decrease in growth and proliferation of hMSCs. Moreover, the inhibitory effects exhibited a dose-dependence manner. On the other hand, Fn coating did not promote the growth and proliferation of hMSCs, and also did not inhibit proliferation, but enhanced the adhesion of hMSCs to silicone surface. These findings indicate that Col I decreases the growth and proliferation of hMSCs and is not suitable for encouraging expansion of hMSCs in vitro. Low-dose bFGF could be preferred as medium supplementation for hMSCs expansion and Fn is a better coating material for hMSCs adhesion.     

An efficient contention resolution algorithm for input queuing atm cross-connect switches

This paper describes an efficient contention resolution algorithm and its distributed implementation for large capacity input queuing cross-connect switches, which will establish virtual paths in future broadband ATM networks. The algorithm dynamically allocates sending time to cells held in input queues when no contention is indicated in the designated output ports. An expression for the mean delay and the cell loss probability for random traffic are derived through an approximate analysis. Input cells are served on a first-come, first-served basis as conventional contention resolution algorithms whose throughput saturates at 58 per cent because of head of line blocking in input queues. The proposed algorithm achieves a maximum throughput of 76 per cent.     

Annealing effect on temperature coefficient of resistivity in La1−xSrxMnO3 ceramics

We investigated annealing effects of La_1?xSr_xMnO₃ (x = 0–0.6) on electrical resistivity and the temperature coefficient of resistivity (TCR). The annealed samples’ resistivity was lower than those of non-annealed samples. For example, annealing changed the resistivity of x = 0.3 at 25 °C from 4.50 × 10^?5 to 3.71 × 10^?5 Ω m. Remarkable difference in TCR was observed after annealing, for x = 0.3, 0.45, and 0.5. For x = 0.3, the TCR after annealing was 4000 ppm/°C, which was 1250 ppm/°C greater than that before annealing. We investigated (1) crystal phase, (2) Mn average valence, (3) Mott insulator–metal transition temperature, and (4) microstructure. The microstructure was remarkably varied for annealed x = 0.3 and 0.5. The average grain size of the x = 0.3 increased from 1.60 up to 2.38 μm. Results show that annealing affects resistivity and TCR because of grain growth during annealing.     

Development of multianode photomultiplier tube

We have developed a multianode photomultiplier tube (MAPMT) which has a sensitive cathode diameter of 36 mm and an anode with 88 segments. The position sensitivity of the tube was studied by using light from a LED and scintillation light from a scintillation-fiber bundle. We observed particle tracks for the first time by using a single photomultiplier tube.