The changing iconography of Japanese political geography

Our world is very fluid, very complex, constantly moving, made up of a great number of interdependent components. Therefore, the locus and the orbit of a particular area play an important role in geography and in politics. The purpose of this study is to examine the iconography of orbit and freedom of movement through an analysis of the transformation of the international politico-economic structure and its impact on Japan and to make clear the footsteps of Jean Gottmann on political geography. Due to its locus being on the crossroad of international power struggles, Japan had accepted different iconographies of orbits every time she faced great mutation in her history. This, in turn, accelerated the synchronism, synergism and synthesis of different iconographies that came to converge at the crossroad. The integration of imported cultures with the Japanese traditional culture promoted the transformation of Japanese society and community to emphasize the freedom of movements. The flexibility of Japanese society and the unifying iconography of Japanese community have enabled Japan to adapt and readapt to changing politico-economic phases. Interested in the relationship between freedom of movement and iconography, Jean Gottmann spent a considerable portion of his academic life inquiring into the changing dynamics of Japanese iconography on the global scene. After a quarter-century pursuit, he contributed to the establishment of political geography in Japan.     

Concept and performance testing of a high‐capacity oil damper comprising multiple damper units

There has been a significant increase in the size of building structures in recent years. Huge structures such as high‐rise buildings and large‐domed stadiums require high‐performance structural control, including the use of high‐capacity dampers, especially in an earthquake‐prone country like Japan. The objective of the present study was the enhancement of both human and structural safety in such structures through the development of a rate‐dependent type of damper with a high damping capacity. Among the various available types of rate‐dependent dampers, the authors focused on the oil damper owing to its stable performance against long‐duration vibrations. The target maximum damping force was 6000 kN, which is higher than that of any existing oil damper utilized in building structures. The authors developed a novel concept for achieving this high capacity while maintaining the size of the damper within acceptable dimensions from an architectural point of view. The concept involves the use of multiple damper units that produce mechanically parallel damping forces spatially arranged in series. As a prototype, a 1500‐kN oil damper was fabricated by combining three 500‐kN dampers. The 1500‐kN prototype damper was conceived as a full‐scale prototype of a damper that is more slender than comparable commercially available dampers in Japan, and as a scaled model of the proposed 6000‐kN damper. Sinusoidal loading tests were conducted on the prototype damper using a frequency range of 0.1–1.5 Hz and a velocity range of 0.4–300 mm/s. The results confirmed that the damper produced the design damping forces. The results of earthquake loading tests also revealed that the damper exerted a stable damping force against a large earthquake and maintained its performance after the earthquake. The damper is particularly effective against earthquakes with long‐period components that could increase the temperature of a damper. This is afforded by its high heat capacity compared to conventional dampers. Considering that the proposed 6000‐kN damper will generate a damping force that is about 2–3 times that of the strongest conventional oil damper, existing manufacturer test machines would be inadequate for evaluating its full performance characteristics. To address this issue, the authors also propose a test method for evaluating the overall damping force. The method is premised on the fact that the characteristic feature of the proposed damper is its combination of multiple damper units. The overall performance is thus evaluated using the test results for the individual damper units while the other dampers are bypassed. This method was verified by the results of the abovementioned sinusoidal loading tests, with the error for the 1500‐kN prototype damper found to be less than 5%. Copyright © 2016 John Wiley & Sons, Ltd.     

Electrical resistivity of fcc phase iron hydrides at high pressures and temperatures

We measured the electrical resistivity of face-centered-cubic (fcc) structured iron hydrides at high pressures up to 65 GPa and high temperatures in a laser-heated diamond anvil cell. The results indicate that the resistivity of stoichiometric fcc FeH_x (x ～ 1.0) is smaller than that of fcc Fe at the same pressure and temperature conditions. The same behavior was also observed in fcc FeNiH_x (x ～ 1.0). On the other hand, hydrogen-poor fcc FeH_x (x < 0.77) showed a resistivity comparable to that of the fcc phase of pure iron. Therefore, we conclude that the stoichiometric fcc Fe (–Ni) hydride is more conductive than Fe (–Ni) with the same crystal symmetry, and the impurity resistivity of hydrogen in Fe is vanishingly small. Even if hydrogen is the major light element in the Earth's core, it would have little influence on the electrical and thermal conductivity of Fe–Ni alloys, and hence the thermal evolution of the core.     

Vegetation history after the late period of the Last Glacial Age based on phytolith records in Nangodani Valley basin,southern part of the Aso caldera,Japan

Vegetation history after the late period of the Last Glacial Age has been reconstructed using phytolith records obtained from three tephra sections in the Nangodani Valley basin, southern part of the Aso caldera, south-west Japan. The topography of the Nangodani Valley basin is divided into three types: somma (caldera rim and wall), caldera floor (central valley) and post-caldera central cone slope. The vegetation transitions after the late period of the Last Glacial Age in the basin vary between these topographic types. The differences can be explained based on human activities in the valley basin. Grassland dominated by Sasa and Pleioblastus dwarf bamboos (before 8 ka) and Miscanthus and other Andropogoneae pampas grasses (after 8 ka) occurred in the central valley and on the post-caldera central cone slope, which were strongly affected by human activities including a long period of burning. In contrast, forest with an understory of Bambusoideae plants was preserved on the caldera rim and wall, which was inaccessible because of its steep topography, during the Holocene.     

Experimental study of reaction between perovskite and molten iron to 146 GPa and implications for chemically distinct buoyant layer at the top of the core

Partitioning of oxygen and silicon between molten iron and (Mg,Fe)SiO₃ perovskite was investigated by a combination of laser-heated diamond-anvil cell (LHDAC) and analytical transmission electron microscope (TEM) to 146 GPa and 3,500 K. The chemical compositions of co-existing quenched molten iron and perovskite were determined quantitatively with energy-dispersive X-ray spectrometry (EDS) and electron energy loss spectroscopy (EELS). The results demonstrate that the quenched liquid iron in contact with perovskite contained substantial amounts of oxygen and silicon at such high pressure and temperature (P–T). The chemical equilibrium between perovskite, ferropericlase, and molten iron at the P–T conditions of the core–mantle boundary (CMB) was calculated in Mg–Fe–Si–O system from these experimental results and previous data on partitioning of oxygen between molten iron and ferropericlase. We found that molten iron should include oxygen and silicon more than required to account for the core density deficit (<10%) when co-existing with both perovskite and ferropericlase at the CMB. This suggests that the very bottom of the mantle may consist of either one of perovskite or ferropericlase. Alternatively, it is also possible that the bulk outer core liquid is not in direct contact with the mantle. Seismological observations of a small P-wave velocity reduction in the topmost core suggest the presence of chemically-distinct buoyant liquid layer. Such layer physically separates the mantle from the bulk outer core liquid, hindering the chemical reaction between them.     

Phase relations of iron–silicon alloys at high pressure and high temperature

The phase relations of Fe-6.4 wt% Si and Fe-9.9 wt% Si have been investigated up to 130 GPa and 2,600 K based on in situ synchrotron X-ray diffraction measurements in a laser-heated diamond-anvil cell along with chemical analysis of the quenched samples using a field-emission electron probe microanalyzer. We found that the maximum solubility of silicon in solid hcp-iron increases with increasing pressure. Linear extrapolation of the phase boundary between hcp + B2 and hcp phases for Fe-9.9 wt% Si suggests that the solid hcp-iron can include more than 9.9 wt% Si at the Earth’s inner-core conditions. If silicon is a major light element in the outer core, a substantial amount of silicon may be incorporated into the inner core during inner-core solidification.     

Wind-Tunnel Experiment on Logarithmic-Layer Turbulence under the Influence of Overlying Detached Eddies

A wind-tunnel experiment was carried out to test a hypothesis that the turbulence characteristics in the near-neutral surface layer are largely determined by detached eddies from above. The surrogate detached eddies were generated by using an active turbulence grid installed at the front of the test section and the parameters of the grid were chosen such that the fully developed logarithmic layer downstream consists of a turbulent flow that has similar normalized intensity to that typically observed in the near-neutral atmospheric surface layer. The effects of the detached eddies on turbulence characteristics were investigated by comparison with a second experiment without detached eddies. The influence of the detached eddies on the logarithmic layer was mostly on the coherent structures; the logarithmic layer with the detached eddies revealed a multi-layer structure similar to that found in the atmosphere where the lower part of the surface layer is dominated by sweep-like events and the upper part by ejection-like events. Our experiments show that the mean velocity gradient and the Reynolds shear stress were, however, not affected significantly by the detached eddies and hence the eddy viscosity.     

Comparison of four ensemble methods combining regional climate simulations over Asia

A number of uncertainties exist in climate simulation because the results of climate models are influenced by factors such as their dynamic framework, physical processes, initial and driving fields, and horizontal and vertical resolution. The uncertainties of the model results may be reduced, and the credibility can be improved by employing multi-model ensembles. In this paper, multi-model ensemble results using 10-year simulations of five regional climate models (RCMs) from December 1988 to November 1998 over Asia are presented and compared. The simulation results are derived from phase II of the Regional Climate Model Inter-comparison Project (RMIP) for Asia. Using the methods of the arithmetic mean, the weighted mean, multivariate linear regression, and singular value decomposition, the ensembles for temperature, precipitation, and sea level pressure are carried out. The results show that the multi-RCM ensembles outperform the single RCMs in many aspects. Among the four ensemble methods used, the multivariate linear regression, based on the minimization of the root mean square errors, significantly improved the ensemble results. With regard to the spatial distribution of the mean climate, the ensemble result for temperature was better than that for precipitation. With an increasing number of models used in the ensembles, the ensemble results were more accurate. Therefore, a multi-model ensemble is an efficient approach to improve the results of regional climate simulations.     

Volcanism in nascent back-arc basins behind the Shichito Ridge and adjacent areas in the Izu-Ogasawara arc,northwest Pacific: evidence for mixing between E-type MORB and island arc magmas at the initiation of back-arc rifting

Mineral chemistry, major and trace elements, and ⁸⁷Sr/⁸⁶Sr ratios are presented for 29 igneous rocks dredged from the northern portion of the Izu-Ogasawara arc. These rocks are compositionally bimodal. Basement gabbro and trondhjemite from the arc are extremely poor in K₂O (0.05–0.19%) and Rb (0.48–0.62 ppm), and their REE patterns and Sr isotope ratios indicate that there are island arc tholeiites. Quaternary volcanic rocks from the present volcanic front (Shichito Ridge; active arc), back-arc seamounts (east side; inactive arc) and Torishima knoll between the two back-arc depressions (incipient back-arc basins) behind the active arc have the same geochemical characteristics as the above plutonic rocks though they are not as depleted in K and Rb. Rhyolite pumice from the backarc depression is also the depleted island arc tholeiite, whereas basalts from the depression have compositions that are transitional between MORB and island arc tholeiites in trace element (Ti, Ni, Cr, V, Y and Zr) and mineral chemistries. The back-arc depression basalts have relatively high Ba_N/Ce_N(0.66–1.24), Ce_n/Yb_N(1.1–1.9) and K/Ba(45–105) and low ⁸⁷Sr/⁸⁶Sr (0.70302–0.70332) and Ba/Sr (0.1–0.2), which are similar to other back-arc basin basalts and E-type MORB, but are quite unlike the depleted island arc tholeiites. The diverse trace element and Sr isotope compositions of basalt-andesite from the back-arc depressions imply the interplay between E-type MORB and island arc tholeiite. These chemical characteristics and the relationships of (Ce/Yb)_N vs (Ba/Ce)_N and (Ce/Yb)_N vs ⁸⁷Sr/⁸⁶Sr suggest that the back-arc depression magmas are generated by mixing of E-type MORB and depleted island arc tholeiite magmas. Geochemical characters of the associated rhyolite from the depression are compatible with partial melting of lower crust.     

Characteristics of the stream network composition of drainage basins in the Japanese Islands

This research is to analyze the composition of stream networks of drainage basins in Japan and to discuss the characteristics of drainage basins in the Japanese Islands. Study areas were selected for 180 drainage basins in the entire country. In this study, a topographic map with a scale of 1:50,000 was used and inserted into the valley line by V-shaped-contour methods in each drainage basin. The streams are ordered according to Strahler's system and measured by the stream number, stream length, stream slope, drainage area, and stream fall in each drainage basin. Horton's law of drainage network composition holds good in most drainage basins in Japan. The average values of the bifurcation ratio, stream length ratio, stream slope ratio, drainage area ratio, and stream fall ratio are 4.24, 1.91, 1.98, 4.52, and 1.04, respectively. The mean bifurcation ratio of drainage basins in Japan is 4.24, and this ratio is slightly greater than in other countries. It is also greater than the theoretical value of 4.0. This implies that the slope of drainage basins in Japan is so steep and the relief energy so large that excess streams have developed to a rather marked degree. The average stream fall ratio is 1.04 for drainage basins in Japan. It suggests that drainage basins are generally considered to be in a stage of maturity in stream channel development for the Japanese Islands. The stream fall ratio, however, is slightly greater than 1.0. Although, the stream beds are nearly in dynamic equilibrium in most cases, it tends to be in a slightly aggrading state.