Grazing exit electron probe microanalysis of submicrometer inclusions in metallic materials

Grazing exit electron probe microanalysis (GE-EPMA) is a new method of EPMA in which characteristic X-rays emitted from only near-surface regions of a specimen are detected at extremely low exit angles near 0 degrees (the grazing exit condition). This technique requires the analytical objects exist on a flat surface. Therefore, the GE-EPMA analysis has been used only for the analysis of particles or a thin film on a flat substrate so that there were only few applications for practical analysis. As a new application, we have carried out GE-EPMA analysis of approximately 0.2-microm inclusions on stainless steel, which appeared to be a projection on the specimen surface with chemical etching. The GE-EPMA quantitative results were in excellent agreement with those of inclusions that were extracted from the stainless steel and analyzed by EPMA with conventional exit condition (30 degrees). This method could be, therefore, applied to the analysis of the submicrometer inclusion in a wide variety of metallic materials if the inclusion appears to be a projection with chemical etching treatment.     

Experimental exploration of discrepancies in F-number correlation of flammability limits

Flammability limits measurement has been made by ASHRAE method for some 20 kinds of combustible gases and vapors. These compounds have been selected mainly because the literature values of flammability limits are not consistent with the F-number calculated ones [J. Hazard. Mater. A 82 (2001) 113]. As a result, it has been found that the newly obtained values of flammable range are classified into three groups. For the first group of compounds, the present values agree well to the literature values. For the second group, the present values do not agree to the literature values but agree with the calculated ones. For the third group ones, the present values neither agree to the literature values nor to the calculated ones. There are 4, 13, and 6 compounds in the respective groups.     

Robot-vision architecture for real-time 6-DOF object localization

This paper presents a new robot-vision system architecture for real-time moving object localization. The 6-DOF (3 translation and 3 rotation) motion of the objects is detected and tracked accurately in clutter using a model-based approach without information of the objects’ initial positions. An object identification task and an object tracking task are combined under this architecture. The computational time-lag between the two tasks is absorbed by a large amount of frame memory. The tasks are implemented as independent software modules using stereo-vision-based methods which can deal with objects of various shapes with edges, including planar to smooth-curved objects, in cluttered environments. This architecture also leads to failure-recoverable object tracking, because the tracking processes can be automatically recovered, even if the moving objects are lost while tracking. Experimental results obtained with prototype systems demonstrate the effectiveness of the proposed architecture.     

Bond-order potential for transition metal carbide cluster for the growth simulation of a single-walled carbon nanotube

A classical many-body potential for transition metal carbide cluster is developed in the form of the bond-order type potential function. The parameter sets between carbon atoms and several transition metal atoms (Fe, Co and Ni) are constructed by fitting binding energies from Density Functional Theory (DFT) calculations. Using the potential function, clustering process of carbon atoms to a small metal cluster is studied by classical molecular dynamics (MD) simulation. The number of hexagonal rings in the Co cluster increases about twice as fast as in the Fe cluster. This implies that the graphitic lattice interacts more strongly with Co atoms than with Fe atoms. A Co cluster has a crystal structure where metal atoms are regularly allocated and embedded in the hexagonal carbon network in the simulation. In contrast, carbon atoms cover the entire surface in case of the Fe cluster. Additionally, the potential energy surface that a carbon atom feels from a 2D closed-packed facet is examined using a hypothetical FCC(1 1 1) facet of several transition metals. The potential energy minima are distributed on the hexagonal network showing the 2D closed-packed facet can be a template where a graphene is formed.     

Discharge characteristics and low‐voltage driving of high‐Xe‐content PDPs

Abstract— High‐Xe‐content PDPs attain improved luminous efficiency, but with sacrifices of higher sustain and address voltages and slower discharge build‐up. By examining PDPs with 3.5–100% Xe contents, it was revealed that space‐charge priming as well as wall‐charge accumulation are effective in obtaining low‐voltage and high‐speed operation. In addition, it was found that the effectiveness is emphasized for higher‐Xe‐pressure PDPs. In this respect, erase addressing is more favorable than write addressing, especially for high‐Xe‐pressure PDPs. The formative time lag of the discharge and diffusion/drift of the space charges are shorter for high Xe contents. In this respect, high‐Xe‐content PDPs have a potential for high‐speed addressing, if driven adequately. The use of space‐charge priming, however, is limited by the duration between the priming and scan pulses. Accumulation of wall charges is limited by ignition of a self‐erase discharge with which all the wall charges are dissipated. Although the highest efficiency and luminance are attained with a 100%‐Xe panel, the optimum Xe gas content, considering the sustain pulse voltage and drive voltage margin, would be 70% Xe + Ne.     

The Principles of Eliminating Pulsating Torque in Current Source Inverter Induction Motor Systems

The problem of reducing the pulsating torque in current source inverter induction motor systems is investigated. Two typical approaches presented in recent publications are analyzed by making clear 1) the correlation among the current harmonics and the torque harmonics, and 2) the conceptual contradiction existing between these two approaches. By synthesizing the analyzed results, fundamental principles for treating the current harmonics and torque harmonics are established. In addition, the method for evaluating the degree of torque ripple is described, along with a proposed criterion for torque ripple content. By applying this criterion to these two approaches, objective estimates of degree of torque pulsations, which were unfeasible so far, are now made possible.     

Growth monitoring and classification of rice fields using multitemporal RADARSAT-2 full-polarimetric data

Spaceborne synthetic aperture radar (SAR) can be used for agricultural monitoring. In this study, three single-polarimetric and four full-polarimetric observation data sets were analysed. A rice paddy field in northern Japan was used as the study site; the data for this site were obtained using RADARSAT-2, which carries a full-polarimetric C-band SAR. Soybean and grass fields were also present within the paddy fields. The temporal change in the backscattering coefficient of the rice paddy fields for the single-polarization data agreed with the temporal change obtained for a rice growth model based on radiative transfer theory. A three-component decomposition approach was applied to the full-polarimetric data. With each rice growth stage, the volume scattering component ratio increased, whereas the surface scattering component ratio generally decreased. The soybean and grass fields showed a smaller double-bounce scattering component than the rice fields for all the acquired data. The results of this study show that multitemporal observation by full-polarimetric SAR has great potential to be utilized for estimating rice-planted areas and monitoring rice growth.     

Sampling error of daily mean surface wind speed and air specific humidity due to Sun-synchronous satellite sampling and its reduction by multi-satellite sampling

To quantify the sampling error of wind speed (W) and the surface air specific humidity (Q _a) resulting from Sun-synchronous polar-orbit satellite sampling and the effect of single- and multi-satellite sampling, we compared satellite-simulated data with true daily mean data using buoy data. True daily mean data were obtained by averaging buoy data at all available times over 24 h, while satellite-simulated data were the averages of buoy data sampled at satellite passing times (once or twice each day). The difference between true and satellite-simulated data was defined as the sampling error. The sampling error of the daily mean data of W and Q _a depends considerably on the satellite observation time and location. Although the sampling error is fairly reduced if multi-satellite sampling is employed, a noticeable sampling error remains in some cases if a wrong sampling combination is employed. Therefore, multi-satellite data should be carefully used to obtain more accurate global data.     

Synthesis of novel organocobalt poly(arylene-vinylene)s containing (cyclobutadiene)cobalt moieties in the main chain

Summary Organocobalt poly(arylene-vinylene)s composed of 1,2- or 1,3- linkage at their cyclobutadiene moieties (3 and 4, respectively) were prepared by the Heck reaction of p-divinylbenzene with (cyclobutadiene)cobalt-containing monomers having two aryl bromide moieties (1 and 2, respectively). The number average molecular weights (M _n) of the obtained organocobalt poly(arylene-vinylene)s (3 and 4) were 4,100 and 4,000, respectively (GPC, on the basis of polystyrene). UV-vis spectra of 3 and 4 exhibited main π-π^* absorption peaks at 362 and 397 nm, respectively, which were ca. 60 nm bathochromically shifted from those of the corresponding monomeric units. Both polymers were found to show thermotropic liquid crystallinity in the range of room temperature to ca. 80 °C by employing differential scanning calorimetry (DSC) and the optical measurement using crossed polarizers. Received: 2 July 1999/Accepted: 29 July 1999