Effect of pressure and temperature on the reaction of coal with alcohol-alkali

The ethanol-NaOH reaction of Taiheiyo coal (C, 77.5; H, 6.3 wt%) was examined under a pressure of 0.1–8 MPa nitrogen or hydrogen, at 300 °C for 1 h. Almost all of the products are extracted with pyridine for the entire pressure range and the extraction yield with ethanol increases with pressure, even under nitrogen. The yield of the products extracted with ethanol is higher when the coal is reacted under hydrogen than when reacted under nitrogen. The explanation for these results is that, under pressure, the hydrogen produced from the reaction of alcohol and NaOH is enclosed for a longer period in the solvent, thus accelerating the hydrogenation reaction of the coal, also under hydrogen pressure, the reaction is particularly accelerated because the hydrogenation takes place with the hydrogen gas. At 300 °C, the ethanol-extraction yield is much higher than the benzene-extraction yield, but the latter increases rapidly and approaches that of the ethanol-extraction yield as the temperature rises to 400 °C. This is because the polar groups, e.g. as hydroxyl groups which are rich in the low-temperature products, decrease with the temperature rise.     

Resolution of a controversy surrounding the focusing mechanisms ofsynthetic aperture radar images of ocean waves

This paper addresses key problems regarding the focusing of synthetic aperture radar (SAR) images of ocean surface waves, explaining why applying a processor defocus will generally yield an enhanced image, why the same defocus applies to both image modulations brought about by the radar cross section and by the velocity bunching process, and why the effects apply to both single-look and multilook systems independently of look relocation. Two interpretations are given for the case when surface scatterers are stationary, but modulated in reflectivity (radar cross section) by a propagating wavefield. The first interpretation is what will be called a “degrade-and-shift” model. In it, a processor focusing adjustment degrades a point image. However, the overall image can be enhanced because an appropriate defocus results in a shifting of points in such a way that the image can most closely resemble the image of the time-invariant (or “frozen”) reflectivity. The second interpretation is a “defocus-and-refocus” model in which the image of a time-varying reflectivity is defocused and may be refocused to enhance the image. In justifying this “defocus-and-refocus” model, it is shown that the radar return from stationary scatterers of time-varying reflectivities is identical to that from physically moving scatterers of constant reflectivity. Thus, the two interpretations are not contradictory; they are, fundamentally, equivalent. The models support the use of a processor defocus corresponding to one half the wave phase velocity. Both qualitative and quantitative illustrations of the effects are given. Finally, it is shown that the same defocusing effect applies to image modulations brought about by the velocity bunching process     

Direct coupling of VCSELs to plastic optical fibers using guideholes patterned in a thick photoresist

In this letter, we report a simple passive alignment method to couple plastic optical fibers (POFs) to vertical-cavity surface-emitting lasers (VCSELs) for use in parallel optical interconnects. Polymer guide holes were fabricated directly on the top of VCSELs by means of standard photolithography using SU-8 epoxy-based thick photoresist. Perfluorinated graded-index POFs were inserted and fixed in the guide holes to provide butt-coupled packaging modules. For a VCSEL of 15-μm diameter and a POF of 124-μm core diameter, coupling efficiencies were obtained between about 80% and 50%, depending on drive current. The standard deviation of the efficiency at a drive current of 10 mA was 5.9% for a 1 × 5 array     

Effect of antenna polarisation on rain scattering

The effect of the polarisations of antennas on the received power from rain scattering was examined at 34.8 GHz by rotating the ?/2 polariser in the receiving antenna system. It is found that the experimental result is explained satisfactorily by the scattering theory.     

A study of nanosize Fe3O4 deposited on carbon matrix

Nanosized crystalline Fe3O4 (with an average particle size of 16 nm) was successfully synthesized on a carbon matrix surface. The prepared sample was heat-treated in the temperature range 300 degrees C - 750 degrees C to remove residual impurities and to obtain a final product with a 77:23 ratio between magnetite and the carbon support. The sample was subjected to physicochemical and electrochemical tests. The purity of the phase and the particles size was determined by X-ray diffraction analysis and confirmed by field emission scanning electron micrographs. The specific surface area of the sample measured by the B.E.T method was 120 m2 g(-1). A series of electrochemical tests including EIS, CV and long-term constant current cycling have been performed. The obtained reversible capacity within 15 cycles was in the range 400-550 mA h x g(-1). The electrochemical behavior of the test sample and its possible practical use as an anode material in lithium secondary batteries are discussed.     

Time-dependent dielectric breakdown (TDDB) distribution in n-MOSFET with HfSiON gate dielectrics under DC and AC stressing

This paper discusses time-dependent dielectric breakdown (TDDB) in n-FETs with HfSiON gate stacks under various stress conditions. It was found that the slope of Weibull distribution of T_bd, Weibull β, changes with stress conditions, namely, DC stress, unipolar AC stress and bipolar AC stresses. On the other hand, the time evolution component of stress-induced leakage current (SILC) was not changed by these stresses. These experimental results indicate that the modulation of electron trapping/de-trapping and hole trapping/de-trapping by stress condition changes the defect size in high-k gate dielectrics. Therefore, the control of injected carrier and the characteristics of trapping can provide the steep Weibull distribution of T_bd, leading to long-term reliability in scaled CMOS devices with high-k gate stacks.     

Computer simulation of a porous positive electrode for lithium batteries

The discharge characteristics of a Li/Li_yCoO₂ cell were simulated by numerical calculations. Based on the program proposed by Newman's group, the change in entropy due to lithium-ion insertion into the active materials was introduced into the open-circuit potential (OCP) for more practical applications. The OCP of LiCoO₂ (y = 1) at a full-discharge state was 3.82 V, which was determined from the original program. However, it should show a rapid decrease to minus infinity when discharge is complete (y = 1), which is due to the introduced entropy term. In addition, the local use of active materials across the Li_yCoO₂ electrode was not uniform, whereas the original program showed a constant value throughout the electrode. Based on the present results, the introduction of an entropy term to the OCP of Li_yCoO₂ works reasonably well for more practical applications.     

ESD robustness improvement for integrated DMOS transistors —the different gate‐voltage dependence of It2 between VDMOS and LDMOS transistors

This paper presents the device‐level electrostatic discharge (ESD) robustness improvement for integrated vertical double‐diffused MOS (VDMOS) and lateral double‐diffused MOS (LDMOS) transistors by changing device structure. The ESD robustness of VDMOS transistor was improved by preventing current concentration and that of LDMOS transistor was improved by relaxing the electric field under the LOCOS oxide. We found the different gate‐voltage dependence of the second breakdown current (I_t2) between VDMOS and LDMOS transistors. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Analysis of Snapback Phenomena in VDMOS Transistor having the High Second Breakdown Current: A High ESD Mechanism Analysis

We proposed the balanced vertical double - diffused MOS (B-VDMOS) transistor. The B-VDMOS transistor is not destroyed by avalanche breakdown and acquires the high second breakdown current. Owing to the high second breakdown current, the B-VDMOS transistor has high electrostatic discharge (ESD) robustness. This paper presents the mechanism of the snapback phenomena and clarifies the cause that the B-VDMOS transistor has the high second breakdown current. We find the cause that current does not become concentrated even after avalanche breakdown in the B-VDMOS transistor. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Tetrodotoxin poisoning due to smooth-backed blowfish Lagocephalus inermis and toxicity of L. inermis caught off the Kyushu coast, Japan

Food poisoning due to ingestion of a puffer fish occurred in Nagasaki Prefecture, Japan, in October 2008, causing neurotoxic symptoms similar to those of tetrodotoxin (TTX) poisoning. In the present study, we identified the species, toxicity, and toxins using the remaining samples of the causative puffer fish. The puffer fish was identified as smooth-backed blowfish Lagocephalus inermis by nucleotide sequence analysis of the 16S rRNA and cytochrome b gene fragments of muscle mitochondrial DNA. The residual liver sample showed toxicity as high as 1,230 mouse unit (MU)/g by bioassay and TTX was detected by liquid chromatography/mass spectrometry analysis. We therefore concluded that the food poisoning was due to TTX caused by consumption of the toxic liver of L. inermis. This is the first report that the liver of L. inermis caught in Japanese waters is strongly toxic, with levels exceeding 1,000 MU/g. In this context, we re-examined the toxicity of L. inermis collected off the coast of Japan. Of 13 specimens assayed, 12 were toxic, although the toxicity varied markedly among individuals and tissues. Because the intestine and ovary of L. inermis have been considered non-toxic, it is particularly noteworthy that these organs were determined to be toxic, with a maximum toxicity of 43.6 MU/g and 10.0 MU/g, respectively. Furthermore, kidney, gallbladder, and spleen, whose toxicity has been unknown, were frequently found to be weakly toxic with levels ranging from 10 to 99 MU/g. Therefore, further study is needed to re-examine the toxicity of smooth-backed blowfish L. inermis in the coastal waters of Japan.