Lessons from Earthquakes in Recent Times and their Effects on the Development of Geotechnology

This paper first reviews the earthquakes that occurred since 1995 and then outlines the significant lessons learnt from disasters. The discussion then goes into the induced development of engineering practices that were triggered by those disasters. It is clear that major development occurred in design philosophies, soil improvement, and facilities for research. The last section of this paper addresses the compound effects of earthquakes and rainfall that may make the extent of the disasters worse.     

Convergence acceleration and accuracy improvement in power bus impedance calculation with a fast algorithm using cavity modes

Based on the cavity-mode model, we have developed a fast algorithm for calculating power bus impedance in multilayer printed circuit boards. The fast algorithm is based on a closed-form expression for the impedance Z matrix of a rectangular power bus structure; this expression was obtained by reducing the original double infinite series into a single infinite series under an approximation. The convergence of the single series is further accelerated analytically. The accelerated single summation enables much faster computation, since use of only a few terms is enough to obtain good accuracy. In addition, we propose two ways to compensate for the error due to the approximation involved in the process of reducing the double series to the single series, and have demonstrated that these two techniques are almost equivalent.     

Multipath structure for FSR expansion in waveguide-based optical ring resonator

A multipath structure of a ring resonator is proposed to expand the free spectral range. Simulation work indicates that the multipath ring resonator has 25 GHz-adjacent-channel crosstalk of -41 dB, maximum interchannel crosstalk of -18 dB, and -1 dB bandwidth of 4 GHz for a typical expansion factor of 10. The results show the advantages of characteristics compared with a double-cavity ring resonator and a triple-coupler ring resonator.     

A consideration of ternary C-H-O diagram for diamond deposition using microwave in-liquid and gas phase plasma

The purpose of this study is to clarify the mechanism of diamond synthesis using an in-liquid plasma chemical vapor deposition (CVD) method. We investigated the chemical reactions from a liquid mixture of methanol and ethanol (in-liquid plasma CVD) and a gas mixture of methane and hydrogen (gas-phase CVD). Carbon monoxide (CO) is firstly synthesized and then a chemical reaction using the remaining carbon (C) and hydrogen (H) is induced to synthesize a carbon substance. Residual H radicals act as an etchant removing the incompletely binding carbon atom that hinders diamond crystal growth. From spectroscopic measurements, CO peaks were clearly observed when the oxygen component is contained in the raw materials. From the experimental results of carbon deposits using various liquid and gas mixtures as the raw materials, we found that the region of the remaining H and C after CO synthesis satisfying H/C > 20 is necessary to synthesize diamonds using in-liquid plasma CVD method. The region of H/C > 20 in the Bachmann C-H-O diagram nearly agrees with the experimental results of synthesizing diamonds.     

The influence of side chains on formation of inclusion complexes prepared with polyolefin and cyclodextrins

We investigated the formation of inclusion complexes (ICs) between cyclodextrins (CDs) with different cavity size and polyolefin (PO) with different side chains by using Fourier transform infrared (FTIR) spectroscopy, wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry. The analysis of FTIR spectra revealed that the resultants were complexes of CD and PO, and the analysis of WAXD revealed that the molecules of CD had a channel structure due to the formation of ICs. We found that IC could not be obtained when the cavity size of CD was small for PO molecules to thread and it was too large for cross-sectional area of PO molecules. Thus, it was found that PO1 with few side chains could form IC with α-CD, and PO2 with ethyl side chain could form IC with β-CD and γ-CD, while the PO3 with 2-methyl-propyl side chain could form IC with γ-CD. These results suggest that the cross-sectional areas of polymer and the cavity size of CDs play critical roles in the formation of ICs. It is only possible to form ICs when the polymer chains can tread into cavities of CDs, and the space between the polymer and CD is suitable to provide enough intermolecular interaction to keep the structure of IC stable.     

Guided-mode resonant grating filter with an antireflection structured surface

We describe a new structure of guided-mode resonant grating (GMRG) filters with low sideband reflectance. This GMRG filter consists of a high-index thin film on an antireflective structured surface called "moth-eye structure." Since the high-index film undulates along the surface structure, the film acts as a modulated optical waveguide. An incident light wave satisfying a resonant condition is reflected by the GMRG filter, and nonresonant light waves pass through the filter. This GMRG filter is valid for reducing reflection of nonresonant light waves in a wide spectral range. The resonant reflection of this new filter was investigated by numerical calculation based on an electromagnetic grating analysis. In the case of a triangular antireflective surface structure whose thickness is 2x greater than its period, the sideband reflectance for nonresonant light waves was lower than 0.5% for TM-polarized light in a wide range of wavelengths.     

Cytotoxic 2,3-secoaromadendrane-type sesquiterpenoids from the liverwort Plagiochila ovalifolia

The ether extract of the Japanese liverwort, Plagiochila ovalifolia Mitt. (Plagiochilaceae) yielded three 2,3-secoaromadendrane-type sesquiterpenoids, plagiochiline-A-15-yl octanoate, 14-hydroxyplagiochiline-A-15-yl 2E,4E-dodecadienoate and 14-hydroxyplagiochiline-A-15-yl 2E,4E,8Z-tetradecatrienoate. The two latter compounds were first isolated from the Plagiochila species. The structures of the new compounds were elucidated by spectroscopy. Plagiochiline-A-15-yl octanoate and 14-hydroxyplagiochiline-A-15-yl 2E,4E-dodecadienoate showed significant cytotoxicity against P-388 murine leukemia tumor cells, both compounds exhibiting an ID50 of 0.05 microgram/ml. Plagiochiline A also showed cytotoxic activity. The ID50 was 3.0 micrograms/ml.     

Facile synthesis and thermal properties of waterglass-based silica xerogel nanocomposites containing reduced graphene oxide

In this study, new rGO-silica xerogel nanocomposites (SX-rGO) and its glass fiber reinforced composites (GFR-SX-rGO) were prepared, and its microstructure and thermal properties were evaluated. The raw material was a mixed dispersion prepared by adding 0.01–2.5?wt% of reduced graphene oxide (rGO) to waterglass (6% SiO₂). A hydrogel was prepared via sol-gel reaction of this raw material, which was then immersed in hydrochloric acid, hydrophobized in a siloxane/2-propanol reaction system, and then dried at ambient pressure to obtain a hydrophobic carbon-silica xerogel composite. The obtained samples were characterized by N₂ physisorption (at 77?K), solid ²⁹Si Magic angle spinning nuclear magnetic resonance spectroscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, differential scanning calorimetry, thermogravimetric analysis, hydrophobicity, and thermal conductivity. It was found that as the amount of rGO was increased, the specific surface area of the nanocomposite decreased by ~25% from 535 to 403?cm²/g, and the average pore size and pore volume were almost halved. The thermal decomposition temperature of the SX-rGO was increased markedly by the addition of rGO. Moreover, the GFR-SX-rGO-0.5 showed low density (0.208?g/cm³), high contact angle (146°) and low thermal conductivity (0.0199?W/mK).