In situ flash X-ray observation of projectile penetration processes and crater cavity growth in porous gypsum target analogous to low-density asteroids     

Minami Yasui  Masahiko Arakawa  Sunao Hasegawa  Yukihiro Fujita  Toshihiko Kadono 《Icarus》2012,221(2):646-657

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Halving global GHG emissions by 2050 without depending on nuclear and CCS     

Osamu Akashi  Tatsuya Hanaoka  Toshihiko Masui  Mikiko Kainuma 《Climatic change》2014,123(3-4):611-622

In this paper, we assessed the technological feasibility and economic viability of the mid-term (until 2050) GHG emission reduction target required for stabilization of radiative forcing at 2.6 W/m2. Given the apparent uncertainty surrounding the future deployment of nuclear and CCS technologies, we intensively investigated emission reduction scenarios without nuclear and CCS. The analysis using AIM/Enduse[Global] shows the emission reduction target is technologically feasible, but the cost for achieving the target becomes very high if nuclear and CCS options are limited. The main reason for the cost rise is that additional investment for expensive technologies is required in order to compensate for emission increases in the steel, cement and power generation sectors in the absence of CCS. On the other hand, if material efficiency improvement measures, such as material substitution, efficient use of materials and recycling, are taken, the cost of achieving the emission reduction target is significantly reduced. The result indicates the potentially important role of material efficiency improvement in curbing the cost of significant GHG emission reductions without depending on nuclear and CCS.  相似文献   

Linking two centuries of tree growth and glacier dynamics with climate changes in Kamchatka     

Jiri Dolezal  Jan Altman  Valentina P. Vetrova  Toshihiko Hara 《Climatic change》2014,124(1-2):207-220

Glaciers around the world retreated as the climate warmed substantially. For the majority of alpine and arctic areas, however, the lack of meteorological data over a long period makes it difficult to build long-term climate and glacial fluctuation relationships, emphasizing the importance of natural proxy archives. Here we use the 230-year record of stem radial growth of birch trees (Betula ermanii) from the treeline forests above the receding glaciers in eastern maritime Kamchatka to analyse temporal variations of climate as well as glacial advance and retreat. Glaciers in Kamchatka Peninsula represent the southern limit of glaciation in far eastern Eurasia, which makes them prone to global warming. Using instrumental climate data (1930–1996) from local meteorological stations, we find that the July temperature had most prominent positive impact on birch growth. On the contrary, smaller ring increments are associated with the positive summer and net annual ice mass balance of Koryto Glacier. The prevailing trend of higher summer temperatures and lower snowfall over the past 70 years has enhanced tree growth while causing the glacier’s surface to lower by about 35 m and its front to retreat by about 490 m. Assuming these same relationships between climate, tree growth, and glacier mass balance also existed in the past, we use tree rings as a proxy record of climatically induced temporary halts in the glacier’s retreat over the past two centuries, which in total was over 1,000 m. Both direct observations and tree ring proxies indicate several prolonged warm periods (1990s, 1960s, 1930–1940s, 1880–1900s) interspersed with cooler periods (1984–1985, 1970–1976, 1953–1957, 1912–1926, 1855–1875, 1830–1845, 1805–1820 and 1770–1780) when the glacier re-advanced, creating several consecutive terminal moraine ridges. We conclude that birch tree-rings are suitable for assessing tree growth/climate/glacial relationships over a longer timescale in maritime Kamchatka.  相似文献   

A ground-based observation of the LCROSS impact events using the Subaru Telescope     

Peng K. Hong  Seiji Sugita  Yasuhito Sekine  Naruhisa Takatoh  Tetsuharu Fuse  Hideyo Kawakita  Eliot F. Young  Kosuke Kurosawa  Junichi Haruyama  Toshihiko Kadono  Shunichi Kamata  Tomohiko Sekiguchi  Hirotomo Noda 《Icarus》2011,214(1):21-29

The Lunar Crater Observation and Sensing Satellite (LCROSS) mission was an impact exploration searching for a volatile deposit in a permanently shadowed region (PSR) by excavating near-surface material. We conducted infrared spectral and imaging observations of the LCROSS impacts from 15 min before the first collision through 2 min after the second collision using the Subaru Telescope in order to measure ejecta dust and water. Such a ground-based observation is important because the viewing geometry and wavelength coverage are very different from the LCROSS spacecraft. We used the Echelle spectrograph with spectral resolution λ/Δλ ∼ 10,000 to observe the non-resonant H₂O rotational emission lines near 2.9 μm and the slit viewer with a K′ filter for imaging observation of ejecta plumes. Pre-impact calculations using a homogeneous projectile predicted that 2000 kg of ejecta and 10 kg of H₂O were excavated and thrown into the analyzed area immediately above the slit within the field of view (FOV) of the K′ imager and the FOV of spectrometer slit, respectively. However, no unambiguous emission line of H₂O or dust was detected. The estimated upper limits of the amount of dust and H₂O from the main Centaur impact were 800 kg and 40 kg for the 3σ of noise in the analyzed area within the imager FOV and in the slit FOV, respectively. If we take 1σ as detection limit, the upper limits are 300 kg and 14 kg, respectively. Although the upper limit for water mass is comparable to a prediction by a standard theoretical prediction, that for dust mass is significantly smaller than that predicted by a standard impact theory. This discrepancy in ejecta dust mass between a theoretical prediction and our observation result suggests that the cratering process induced by the LCROSS impacts may have been substantially different from the standard cratering theory, possibly because of its hollow projectile structure.  相似文献