Extended Le Chatelier's formula for carbon dioxide dilution effect on flammability limits

Carbon dioxide dilution effect on the flammability limits was measured for various flammable gases. The obtained values were analyzed using the extended Le Chatelier's formula developed in a previous study. As a result, it has been found that the flammability limits of methane, propane, propylene, methyl formate, and 1,1-difluoroethane are adequately explained by the extended Le Chatelier's formula using a common set of parameter values. Ethylene, dimethyl ether, and ammonia behave differently from these compounds. The present result is very consistent with what was obtained in the case of nitrogen dilution.     

A 12 MHz data cycle 4 Mb DRAM with pipeline operation

A 12 MHz data-cycle 4 Mb DRAM (dynamic RAM) with pipeline operation was designed and fabricated using 0.8 μm twin-tub CMOS technology. The pipeline DRAM outputs data corresponding to addresses that were accepted in the previous inverted random access storage (RAS) input cycle. The latter half of the previous read operation and the first half of the next read operation take place simultaneously, so the inverted RAS input cycle time is reduced. This pipeline DRAM technology needs no additional chip area and no process modification. A 95 ns inverted RAS input cycle time was obtained under worst conditions while this value is 125 ns for conventional DRAMs     

Calculation of minimum ignition energy of premixed gases

The minimum ignition energy of premixed gases has been calculated by using two theoretical expressions and compared with the experimental data. One expression considers the amount of energy that the minimal flame should have, and the other the heat loss from the surface of the minimal flamelet. The former is a cubic function of the quenching distance while the latter is a quadratic function of quenching distance. It has been found that the latter expression gives a better fit to the experimental data than the former, though the discrepancy is considerable even for the latter expression. The calculated widths of the fronts of the minimal flame for various fuels were about one-order of magnitude smaller than the corresponding experimentally determined quenching distances, although no clear correlation relationship between the two quantities was found.     

Photosensitive GeO2-SiO2 films for ultraviolet laser writing of channel waveguides and bragg gratings with Cr-loaded waveguide structure

Irradiation with intense ultraviolet laser pulses induced a large refractive-index change in 30GeO2-70SiO2 waveguide-grade thin films prepared by the plasma-enhanced chemical vapor deposition method, which contained a large amount of photoactive Ge2+ defects. The maximum index change in the as-deposited films by KrF and XeF excimer laser irradiation was estimated to be 1.2 x 10(-3) and 0.28 x 10(-3), respectively. These results clearly indicate that the photorefractivity of GeO2-SiO2 glasses is due to a Ge2+ defect in origin. The channel waveguide and the planar Bragg gratings were directly written in the photoactive Ge(2+)-enriched GeOs-SiO2 thin films by pulsed ultraviolet laser irradiation with a Cr-metal-loaded-type waveguide structure.     

Surface plasmon resonance near-infrared spectroscopy

Near-infrared (NIR) spectroscopy is ill-suited to microanalysis because of its low absorptivity. We have developed a highly sensitive detection method for NIR spectroscopy based on absorption-sensitive surface plasmon resonance (SPR). The newly named SPR-NIR spectroscopy, which may open the way for NIR spectroscopy in microanalysis and surface science, is realized by an attachment of the Kretschmann configuration equipped with a mechanism for fine angular adjustment of incident light. The angular sweep of incident light enables us to make a tuning of a SPR peak for an absorption band of sample medium. From the dependences of wavelength, incident angle, and thickness of a gold film on the intensity of the SPR peak, it has been found that the absorbance can be enhanced by approximately 100 times compared with the absorbance obtained without the gold film under optimum conditions. This article reports the details of the experimental setup and the characteristics of absorption-sensitive SPR in the NIR region, together with some experimental results obtained by using it.     

Flammability limits of isobutane and its mixtures with various gases

Flammability limits of isobutane and five kinds of binary mixtures of isobutane were measured by the ASHRAE method. Propane, nitrogen, carbon dioxide, chloroform, and HFC-125 (1,1,1,2,2-pentafluoroethane) were used as the counter part gases in the mixtures. The observed data were analyzed using the equations based on Le Chatelier's formula. The flammability limits of mixtures with propane were well explained by the original Le Chatelier's formula. The flammability limits of mixtures with nitrogen and the ones with carbon dioxide were adequately analyzed by the extended Le Chatelier's formula. It was found that the extended Le Chatelier's formula is also applicable to the flammability limits of mixtures with chloroform and HFC-125.     

Higher-order structural analysis of bacterial poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanote] highly oriented films

Bacterial poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanoate] (PHBH) highly oriented films were prepared by the combination of roll and uniaxial drawing processes. The change in the higher-order structure of PHBH films was investigated by wide-angle X-ray diffraction (WAXD) and small angle X-ray scattering (SAXS). Extended films, which show superior mechanical properties and high ductility, have complicated structures. By roll extension, both deformed and undeformed spherulites co-exist, the former inclined to the direction perpendicular to the film surface. The latter were destroyed by further uniaxial extension. The tie-molecules between uniaxially oriented lamellae were extended and transformed to the β-form with a planar zig-zag conformation. Three kinds of structures, c-axis parallel to the uniaxial drawing direction, c-axis inclining to the normal vector of the film surface, and the β-form between lamellae, are intermingled in the film.     

Decomposition of chlorofluorocarbons in the presence of water over zeolite catalyst

The decomposition of chlorofluorocarbons (CFCs) in the presence of water was examined over a variety of solid acid catalysts. More than 40% of the conversion of CFC was observed on HY zeolite, H-mordenite, H-ZSM-5, γ-Al₂O₃, and SiO₂TiO₂ catalysts, and the selectivity to CO and CO₂ was nearly 100% except on γ-Al₂O₃. Although the H-mordenite had the highest activity among the tested catalysts, it was gradually deactivated during the reaction due to the elimination of Al atoms from the zeolite framework. A good relationship was found between the reactivity on H-mordenite and the bond energy of CCl in compounds of CCl₄, CCl₃F, CCl₂F₂, and CClF₃, suggesting that the rate controlling step was the cleavage of the CCl bond.     

Property of upgraded solid product from low rank coal by thermal reaction with solvent

The upgrading process for the production of clean solid fuel from subbituminous and brown coals is receiving current attention. We propose upgrading of low rank coal with solvent at 350–450 °C under 2 MPa of initial nitrogen atmosphere. Upgrading of German Fortuna brown coal (heating value: 25.4 MJ/kg, daf) at 440 °C in the presence of t-decalin gave 66 wt.% of solid products with heating value of 35.4 MJ/kg, daf. Gaseous product consisted of mainly carbon dioxide (80 wt.%) and methane. Therefore, cracking of carboxylic functional group took place effectively in this condition. Ignition temperature of the upgraded solid product, measured by thermogravimetry under airflow, increased to higher than 400 °C, while raw brown coal showed corresponding temperature of 290 °C. From the XRD patterns by X-ray diffractometry for the upgraded product, distribution of aromatic stacking layer number (N) shifted to larger N by upgrading with solvent. It is obvious that the effective carbonization occurs under these conditions. This suggests the possibility to produce value-added solid fuel or carbonaceous liquid and solid chemicals, from low rank coal, whose quality is comparable to the bituminous coal.     

Molecular dynamics study of wearless friction in sub-micrometer size mechanisms and actuators based on an atomistic simplified model

Frictional resistance accompanying steady sliding motion is studied systematically as a function of various experimental parameters by means of molecular dynamics simulation using a two-dimensional model. Exploration of universal features lying in wearless friction in mesoscopic systems revealed unique dependence of the frictional force on sliding velocity, applied load, and mean temperature. Atomistic origin of this dependence is discussed in terms of “size effect” on the basis of a hypothesis that the frictional power corresponds to the rate of energy dissipation via forced vibration and subsequent energy transfer between normal phonon modes due to anharmonicity of inter-particle potential.