A geometric method of sector decomposition

We propose a new geometric method of IR factorization in sector decomposition. The problem is converted into a set of problems in convex geometry. The latter problems are solved using algorithms in combinatorial geometry. This method provides a deterministic algorithm and never falls into an infinite loop. The number of resulting sectors depends on the algorithm of triangulation. Our test implementation shows smaller number of sectors comparing with other existing methods with iterations.     

Enhancement of turbulent jet diffusion flame blowout limits by annular counterflow

The effects of a proposed combustion technique, named as annular counterflow, on the enhancement of jet diffusion flame blowout limits were investigated by a series of experiments conducted for the present study. Annular counterflow was formed in a concentric annulus, in which fuel jet was ejected from a nozzle and air was sucked into an outer cylinder encompassing the nozzle. Three fuel nozzles and outer cylinders of different sizes were utilized to perform the experiments. Schlieren technique and normal video filming were employed for the visualization of diverse flame morphologies triggered by the said flow. Gas samplings were taken and scrutinized by the use of a gas chromatograph. Results showed that the blowout limits can be enhanced dramatically by an increase in volume flow rates of air‐suction. Mixing enhancement is achieved with frequent and strong outward ejection of fluids from the cold jet when this technique is applied. The blowout limits are further extended when the diameter of outer cylinders becomes smaller and/or that of the fuel nozzle becomes larger. The base widths of lifted flames were found to be narrower in the interim of annular counterflow application. The rates of increase in flame lift‐off heights and base widths along with an increase in fuel flow velocities become sluggish when the volume flow rates of air are increased. The amount of fuel that was sucked into the outer cylinder was found to be negligible and trivial. A model based on annular and coaxial jet was developed to predict the lifted flame base width and blowout limits. The coincidence between the prediction and experimental results unambiguously validates that the momentum of air‐suction dominates the beneficial effect. Copyright © 2001 John Wiley & Sons, Ltd.     

Coal liquefaction mechanism using a tritium tracer method

To determine the behavior of hydrogen in tetralin, the reaction of tetralin with tritiated gaseous hydrogen was studied in a flow reactor at 400–450°C, 2.5–9.8 MPa for various residence times. The amount of hydrogen exchange between tetralin and tritiated hydrogen was estimated from the balance of hydrogen and tritium. Although yields of methylindan and naphthalene, and the hydrogen-exchange ratio (HER) of tetralin increased monotonously with residence time, these values were scarcely influenced by the reaction pressure at every temperature. It was thought that the formation of tetralyl radicals in this system would be the rate-determining step for both the conversions of tetralin into methylindan and naphthalene, and the hydrogen exchange of tetralin. Conversions of tetralin into methylindan and naphthalene, and the hydrogen-exchange reaction using the autoclave were very close to those using the flow reactor.     

Two-phase eutectic cell growth modles and extension to off-mono-variant region

Abstract

CoTe and CoTe₂ nanorods with average diameter of 100 nm were synthesized by a simple hydrothermal process, and different CoTe₂ nanostructures were obtained by changing the NaOH concentration. CoTe nanorods exhibit weak ferromagnetism while CoTe₂ nanorods present paramagnetic behavior. Different magnetic behaviors occur in the other CoTe₂ nanostructures due to Na⁺ entrance into CoTe₂ crystals. A first-principles study on Na-doped CoTe₂ confirms the magnetic characteristics.     

Pulsed Laser Processing of Carbon and Silicon Clusters and Thin Films

Abstract

Several new processes have been developed for the preparation of fullerenes and thin films by using a pulsed excimer laser. The irradiation of a pulsed KrF excimer laser beam onto a C₆₀ powder target produced single phase C₆₀ thin films when the laser energy fluence was in the range between 40 and 50mJ/cm². By atomic force microscopy, the laser-deposited C₆₀ thin film was verified to have a surface far smoother that the surfaces of films produced by the conventional evaporation method. The stainless steel rods coated with this film exhibited an excellent tribological property. Cluster formation from SiC and other carbides MC_n(M=Ti,W,B) was investigated by laser desorption time-of-flight mass spectrometry. No clear indication was observed for the production of such clusters as (SiC)₆₀ and (M_xC_60-x) from the sintered targets directly as well as from the films laser deposited from the targets. However, C₆₀ and C₇₀ were found to exists in the laser-deposited films, indicating a new applicability of pulsed laser processing for segregative cluster synthesis from solid solution. Preliminiary results on thin film deposition via pulsed ablation of (Ba,Na)_xSi₄₆ clathrate were also presented.     

Preparation and characterization of Mg–Al layered double hydroxides intercalated with benzenesulfonate and benzenedisulfonate

Mg–Al layered double hydroxides (Mg–Al LDHs) intercalated with benzenesulfonate (BS^–) and benzenedisulfonate (BDS^2–) ions were prepared by coprecipitation and characterized by X-ray diffraction, FT-IR spectroscopy, and chemical analyses. The intercalated BS^– and BDS^2– maintained their intrinsic molecular structures within the Mg–Al LDH interlayers. At low intercalation levels, the benzene ring of BS^– in BS · Mg–Al LDH was inclined at 30° relative to the plane of the brucite-like layers of Mg–Al LDH. With increasing BS^– content, the benzene ring adopted an additional configuration perpendicular to the Mg–Al LDH layers. In BDS-intercalated Mg–Al LDH, the benzene ring of BDS^2– was tilted at 26° relative to the plane of the Mg–Al LDH layers. Intercalation levels of BDS^2– were smaller than those of BS^– despite the greater charge density of BDS^2–, which was likely attributable to a greater degree of electrostatic repulsion between intercalated anions.     

Erbium-doped fiber amplifier for video distribution networks

The possibility of an application of Er-doped fiber amplifiers to AM-FDM (frequency division multiplexing) or FM-FDM video distribution networks is discussed. The measured noise and modulation distortion properties of ER-doped fiber amplifiers are good enough to meet even the severe quality standards set for trunk lines. A carrier-to-noise ratio (CNR) of 57 dB for an AM-FDM transmission was measured. A second-order harmonic distortion (HD2) of less than -56 dB was measured by the monotone method (modulation depth m=50%), and a cross modulation distortion (XM) of less than -63 dB was measured by the two-tone method (m=25%×channel). On the basis of these values, composite second-order distortion (CSO) and XM in a 40-channel transmission were estimated as less than -57 dB and -73 dB, respectively. Significant reduction of noise and modulation distortion is made possible by optimizing the length of Er-doped fiber amplifiers and using input- and output-port isolators     

Conceptual design of rain radar for the tropical rainfall measuring mission

Specifications for a spaceborne rain radar for tropical rainfall measurement are described. A spaceborne rain radar has problems peculiar to rain observation from space. The radar must have a fast scanning mechanism to cover a large swath. Very weak rain echoes compared to the sea or land surface signal must be detected. These capabilities must be attained under the severe power consumption and mass limitations of the satellite bus. The fast scanning requirement forces application of an electrically scanning mechanism. This requirement also causes a severe limitation of the available number of independent samples. The requirement for weak rain echoes excludes application of the pulse compression technique, which is a very conventional technique for other active microwave sensors on board satellites. Under these constraints, a rain radar with an electrically scanning planar antenna at 13-8 GHz is proposed.     

Relationship between Expression of Onco-Related miRNAs and the Endoscopic Appearance of Colorectal Tumors

Accumulating data indicates that certain microRNAs (miRNAs or miRs) are differently expressed in samples of tumors and paired non-tumorous samples taken from the same patients with colorectal tumors. We examined the expression of onco-related miRNAs in 131 sporadic exophytic adenomas or early cancers and in 52 sporadic flat elevated adenomas or early cancers to clarify the relationship between the expression of the miRNAs and the endoscopic morphological appearance of the colorectal tumors. The expression levels of miR-143, -145, and -34a were significantly reduced in most of the exophytic tumors compared with those in the flat elevated ones. In type 2 cancers, the miRNA expression profile was very similar to that of the exophytic tumors. The expression levels of miR-7 and -21 were significantly up-regulated in some flat elevated adenomas compared with those in exophytic adenomas. In contrast, in most of the miR-143 and -145 down-regulated cases of the adenoma-carcinoma sequence and in some of the de novo types of carcinoma, the up-regulation of oncogenic miR-7 and/or -21 contributed to the triggering mechanism leading to the carcinogenetic process. These findings indicated that the expression of onco-related miRNA was associated with the morphological appearance of colorectal tumors.