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Hikaru YABUTA Hiroshi NARAOKA Kinya SAKANISHI Hiroyuki KAWASHIMA 《Meteoritics & planetary science》2005,40(5):779-787
Abstract— Chemical structures of the insoluble organic matter (IOM) from the Antarctic CM2 chondrites (Yamato [Y‐] 791198, 793321; Belgica [B‐] 7904; Asuka [A‐] 881280, 881334) and the Murchison meteorite were analyzed by solid‐state 13C nuclear magnetic resonance (NMR) spectroscopy. Different types of carbons were characterized, such as aliphatic carbon (Ali‐C), aliphatic carbon linked to hetero atom (Hetero‐Ali‐C), aromatic carbon (Aro‐C), carboxyls (COOR), and carbonyls (C=O). The spectra of the IOM from Murchison and Y‐791198 showed two major peaks: Ali‐C and Aro‐C, while the spectra from the other meteorites showed only one major peak of Aro‐C. Carbon distribution was determined both by manual integration and deconvolution. For most IOM, the Aro‐C was the most abundant (49.8–67.8%) of all carbon types. When the ratios of Ali‐C to Aro‐C (Ali/Aro) were plotted with the atomic hydrogen to carbon ratio (H/C), a correlation was observed. If we use the H/C as a parameter for the thermal alteration event on the meteorite parent body, this result shows a different extent of thermal alteration. In addition, IOM with a lower Ali/Aro showed a lower ratio of Ali‐C to COOR plus C=O (Ali / (COOR + C=O)). This result suggests that the ratio of CO moieties to aliphatic carbon in IOM might reflect chemical oxidation that was involved in hydrothermal alteration. 相似文献
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M. Akashi Noam Soker Ehud Behar John Blondin 《Monthly notices of the Royal Astronomical Society》2007,375(1):137-144
We calculate the X-ray emission from both constant and time-evolving shocked fast winds blown by the central stars of planetary nebulae (PNe) and compare our calculations with observations. Using spherically symmetric numerical simulations with radiative cooling, we calculate the flow structure and the X-ray temperature and luminosity of the hot bubble formed by the shocked fast wind. We find that a constant fast wind gives results that are very close to those obtained from the self-similar solution. We show that in order for a fast shocked wind to explain the observed X-ray properties of PNe, rapid evolution of the wind is essential. More specifically, the mass-loss rate of the fast wind should be high early on when the speed is ∼300–700 km s−1 , and then it needs to drop drastically by the time the PN age reaches ∼1000 yr. This implies that the central star has a very short pre-PN (post-asymptotic giant branch) phase. 相似文献
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Masahiro Sugiyama Osamu Akashi Kenichi Wada Amit Kanudia Jun Li John Weyant 《Climatic change》2014,123(3-4):397-411
Energy efficiency is one of the main options for mitigating climate change. An accurate representation of various mechanisms of energy efficiency is vital for the assessment of its realistic potential. Results of a questionnaire show that the EMF27 models collectively represent known channels of energy efficiency reasonably well, addressing issues of energy efficiency barriers and rebound effects. The majority of models, including general equilibrium models, have an explicit end-use representation for the transportation sector. All participating partial equilibrium models have some capability of reflecting the actual market behavior of consumers and firms. The EMF27 results show that energy intensity declines faster under climate policy than under a baseline scenario. With a climate policy roughly consistent with a global warming of two degrees, the median annual improvement rate of energy intensity for 2010–2030 reaches 2.3 % per year [with a full model range of 1.3–2.9 %/yr], much faster than the historical rate of 1.3 % per year. The improvement rate increases further if technology is constrained. The results suggest that the target of the United Nations’ “Sustainable Energy for All” initiative is consistent with the 2-degree climate change target, as long as there are no technology constraints. The rate of energy intensity decline varies significantly across models, with larger variations at the regional and sectoral levels. Decomposition of the transportation sector down to a service level for a subset of models reveals that to achieve energy efficiency, a general equilibrium model tends to reduce service demands while partial equilibrium models favor technical substitution. 相似文献
4.
CuiHua Huang Fei Peng Itaru Shibata Jun Luo Xian Xue Kinya Akashi Atsushi Tsunekawa Tao Wang 《寒旱区科学》2019,11(1):81-92
Biological soil crusts(BSCs) play important roles in the carbon(C) balance in arid regions. Net C balance of BSCs is strongly dependent on rainfall and consequent activation of microbes in the BSCs. The compensation-rainfall size for BSCs(the minimum rainfall amount for a positive net C balance) is assumed to be different with BSCs of different developmental stages. A field experiment with simulated rainfall amount(SRA) of 0, 1, 5, 10, 20, and 40 mm was conducted to examine the C fluxes and compensation-rainfall size of BSCs in different parts of fixed dunes in the ecotone between the Badain Jaran Desert and the Minqin Oasis. We found algae-lichen crust on the interdunes and crest, algae crust on the leeward side, and lichen-moss crust on the windward. Even a small rainfall(1 mm) can activate both photosynthesis and respiration of all types of BSCs. The gross ecosystem production, ecosystem respiration, and net ecosystem exchange were significantly affected by SRA, hours after the simulated rainfall, position on a dune, and their interactions. The rapid activation of photosynthesis provides a C source and therefore could be responsible for the increase of C efflux after each rewetting. C-uptake and-emission capacity of all the BSCs positively correlated with rainfall size, with the lowest C fluxes on the leeward side. The compensation rainfall for a net C uptake was 3.80, 15.54, 8.62, and 1.88 mm for BSCs on the interdunes, the leeward side, the crest, and the windward side, respectively. The whole dune started to show a net C uptake with an SRA of 5 mm and maximized with an SRA of about 30 mm. The compensation-rainfall size is negatively correlated with chlorophyll content. Our results suggest that BSCs will be favored in terms of C balance, and sand dune stabilization could be sustained with an increasing frequency of 5-10 mm rainfall events in the desert-oasis transitional zone.- 相似文献
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The feasibility of two low-carbon society (LCS) scenarios, one with and one without nuclear power and carbon capture and storage (CCS), is evaluated using the AIM/Enduse[Global] model. Both scenarios suggest that achieving a 50% emissions reduction target (relative to 1990 levels) by 2050 is technically feasible if locally suited technologies are introduced and the relevant policies, including necessary financial transfers, are appropriately implemented. In the scenario that includes nuclear and CCS options, it will be vital to consider the risks and acceptance of these technologies. In the scenario without these technologies, the challenge will be how to reduce energy service demand. In both scenarios, the estimated investment costs will be higher in non-Annex I countries than in Annex I countries. Finally, the enhancement of capacity building to support the deployment of locally suited technologies will be central to achieving an LCS. Policy relevance Policies to reduce GHG emissions up to 2050 are critical if the long-term target of stabilizing the climate is to be achieved. From a policy perspective, the cost and social acceptability of the policy used to reduce emissions are two of the key factors in determining the optimal pathways to achieve this. However, the nuclear accident at Fukushima highlighted the risk of depending on large-scale technologies for the provision of energy and has led to a backlash against the use of nuclear technology. It is found that if nuclear and CCS are used it will be technically feasible to halve GHG emissions by 2050, although very costly. However, although the cost of halving emissions will be about the same if neither nuclear nor CCS is used, a 50% reduction in emissions reduction will not be achievable unless the demand for energy service is substantially reduced. 相似文献
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Muhammad Akashi Noam Soker Ehud Behar 《Monthly notices of the Royal Astronomical Society》2006,368(4):1706-1716
We calculate the X-ray emission from the shocked fast wind blown by the central stars of planetary nebulae (PNe) and compare with observations. Using spherically symmetric self-similar solutions, we calculate the flow structure and X-ray temperature for a fast wind slamming into a previously ejected slow wind. We find that the observed X-ray emission of six PNe can be accounted for by shocked wind segments that were expelled during the early-PN phase, if the fast wind speed is moderate, v 2 ∼ 400–600 km s−1 , and the mass-loss rate is a few times 10−7 M⊙ yr−1 . We find, as proposed previously, that the morphology of the X-ray emission is in the form of a narrow ring inner to the optical bright part of the nebula. The bipolar X-ray morphology of several observed PNe, which indicates an important role of jets, rather than a spherical fast wind, cannot be explained by the flow studied here. 相似文献
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The two-dimensional equation of motion containing the pressure gradient and Coriolis force is numerically solved for the wind field in and above the layers of a horizontally homogeneous canopy with a vertical distribution of leaf-area densities. The solution shows that, in the case of descending through the canopy, the wind vector turns with an angle which depends on the profile of leaf-area densities. In particular, for the canopy of a forest consisting of upper layers with higher densities and lower layers with smaller densities, the turning is striking; a secondary maximum in wind profile appears in the lower layers.Variations of the aerodynamic parameters for the flow above the canopy are indicated with respect to the leaf-area density. The roughness length varies in such a manner that a maximum appears in intermediate density values, depending on the shape of the profile of leaf-area density. In the case of very dense canopies, the shearing stress acting on the flow above the canopy is determined by the contribution from only the upper canopy elements, but not by that from the lower parts of the canopy. 相似文献
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Equivalent linear method considering frequency dependent characteristics of stiffness and damping 总被引：4，自引：0，他引：4
Nozomu Yoshida Satoshi Kobayashi Iwao Suetomi Kinya Miura 《Soil Dynamics and Earthquake Engineering》2002,22(3)
Equivalent linear dynamic response analysis of ground is based on complex moduli and Fourier series expansion; therefore, it is not an equivalent method but an approximate method. Two deficiencies in the conventional equivalent linear method represented by SHAKE are described first. The maximum shear strength is overestimated, resulting in overestimation of the peak acceleration under a strong ground motion, and the amplification is underestimated at high frequency. The latter sometimes results in underestimation of the peak acceleration under weak ground shaking, and gives an incident wave with unrealistic large accelerations or a divergence of analysis in deconvolution analysis under strong ground motion. Both deficiencies are shown to come from the same cause, i.e. computing the effective strain as a constant fraction of the maximum strain. Since this is a key concept of the equivalent linear analysis, one cannot overcome both deficiencies at the same time in the conventional method. An apparent frequency dependence in stiffness and damping is shown to appear in the dynamic response, although soil itself does not show frequency dependent characteristics. Following this observation, the effective strain is expressed in terms of frequency from the similarity concept of the strain–frequency relationship between time domain and frequency domain. This enables the reduction of both deficiencies at the same time, resulting in a marked improvement in the equivalent linear analysis. The accuracy of the proposed method is examined by the simulations of three vertical array records during large earthquakes. The proposed method always gives much better prediction than conventional equivalent linear methods for both convolution and deconvolution analyses, and it is confirmed to be applicable at more than 1% shear strain. 相似文献
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Kinya Hibino Toshisuke Kashiwagi Shoji Okuno Kaori Yajima Yukio Uchihori Hisashi Kitamura Takeshi Takashima Mamoru Yokota Kenji Yoshida 《Astrophysics and Space Science》2007,309(1-4):541-544
We have developed radiation detectors using the new synthetic diamonds. The diamond detector has an advantage for observations
of “low/medium” energy gamma rays as a Compton telescope. The primary advantage of the diamond detector can reduce the photoelectric
effect in the low energy range, which is background noise for tracking of the Compton recoil electron. A concept of the Diamond
Compton Telescope (DCT) consists of position sensitive layers of diamond-striped detector and calorimeter layer of CdTe detector.
The key part of the DCT is diamond-striped detectors with a higher positional resolution and a wider energy range from 10 keV
to 10 MeV. However, the diamond-striped detector is under development. We describe the performance of prototype diamond detector
and the design of a possible DCT evaluated by Monte Carlo simulations.
相似文献
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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
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