Fuel cell vehicles have a high potential to reduce both energy consumption and carbon dioxide emissions. However, due to the low density, hydrogen gas limits the amount of hydrogen stored on board. ...This restriction also prevents wide penetration of fuel cells. Hydrogen storage is the key technology towards the hydrogen society. Currently high-pressure tanks and liquid hydrogen tanks are used for road tests, but both technologies do not meet all the requirements of future fuel cell vehicles. This paper briefly explains the current status of conventional technologies (simple containment) such as high-pressure tank systems and cryogenic storage. Another method, hydrogen-absorbing alloy has been long investigated but it has several difficulties for the vehicle applications such as low temperature discharge characteristics and quick charge capability due to its reaction heat. We tested a new idea of combining metal hydride and high pressure. It will solve some difficulties and improve performance such as gravimetric density. This paper describes the latest material and system development.
A novel dual‐wire antenna to obtain wideband circular polarisation is proposed. The antenna consists of curl elements with a balanced feed above a ground plane. Using the moment method, an antenna ...with balanced feedlines having two sources is analysed first. Analysis reveals that the antenna shows a 3 dB axial‐ratio bandwidth of 36%. Next, an antenna with quasi‐balanced feedlines having one source to simplify the feed system is investigated. It is found both numerically and experimentally that the axial‐ratio bandwidth remains unchanged, and a VSWR of less than two is obtained.
Mercury's metallic core is expected to have formed under highly reducing conditions, resulting in the presence of significant quantities of silicon alloyed to iron. Here we present the phase diagram ...of the Fe-FeSi system, reconstructed from in situ X-ray diffraction measurements at pressure and temperature conditions spanning over those expected for Mercury's core, and ex situ chemical analysis of recovered samples. Under high pressure, we do not observe a miscibility gap between the cubic fcc and B2 structures, but rather the formation of a re-entrant bcc phase at temperatures close to melting. Upon melting, the investigated alloys are observed to evolve towards two distinct Fe-rich and Fe-poor liquid compositions at pressures below 35-38 GPa. The evolution of the phase diagram with pressure and temperature prescribes a range of possible core crystallization regimes, with strong dependence on the Si abundance of the core.
A novel method of exciting a circularly polarised (CP) loop antenna is proposed using the moment method. A horizontal square loop above the ground plane has two corners connected to a vertical, ...branched feedline with one source. First, the authors show the radiation characteristics of a reference antenna whose corners are excited with two sources having the same amplitudes and a phase difference of 90°. Next, we excite the loop corners with one source using the branched feedline. It is found that when the branch location along the feedline is selected, the antenna radiates a CP wave. The frequency responses of the antenna show that the 3 dB axial‐ratio bandwidth is 12%, where the gain is more than 7.3 dBi. The simulated results are verified with experimental ones.
Fission-fragment mass distributions were measured for ^{237-240}U, ^{239-242}Np, and ^{241-244}Pu populated in the excitation-energy range from 10 to 60 MeV by multinucleon transfer channels in the ...reaction ^{18}O+^{238}U at the Japan Atomic Energy Agency tandem facility. Among them, the data for ^{240}U and ^{240,241,242}Np were observed for the first time. It was found that the mass distributions for all the studied nuclides maintain a double-humped shape up to the highest measured energy in contrast to expectations of predominantly symmetric fission due to the washing out of nuclear shell effects. From a comparison with the dynamical calculation based on the fluctuation-dissipation model, this behavior of the mass distributions was unambiguously attributed to the effect of multichance fission.
The usefulness of graphene for electronics has been limited because it does not have an energy bandgap. Although graphene nanoribbons have non-zero bandgaps, lithographic fabrication methods ...introduce defects that decouple the bandgap from electronic properties, compromising performance. Here we report direct measurements of a large intrinsic energy bandgap of approximately 50 meV in nanoribbons (width, approximately 100 nm) fabricated by high-temperature hydrogen-annealing of unzipped carbon nanotubes. The thermal energy required to promote a charge to the conduction band (the activation energy) is measured to be seven times greater than in lithographically defined nanoribbons, and is close to the width of the voltage range over which differential conductance is zero (the transport gap). This similarity suggests that the activation energy is in fact the intrinsic energy bandgap. High-resolution transmission electron and Raman microscopy, in combination with an absence of hopping conductance and stochastic charging effects, suggest a low defect density.
The ecological roles of dissolved organic matter (DOM) in seawater have not been well understood. One definite function of DOM stems from its complexation ability with trace metals under the ...conditions of seawater. A chemical complexation model of the marine system was introduced in order to clarify the ecological roles of strong organic ligands in DOM related to the acquisition of bioactive metals (Cu, Fe and Zn) by phytoplankton, assuming that two types of strong organic ligands coexist in oceanic DOM and complexes with bioactive metals. The results reveal that the weaker organic ligand, rather than the stronger one, plays a significant role in the reduction of Cu toxicity for phytoplankton growth. It is suggested that the presence of reactions with Cu that are competitive to the strong organic ligand causes extremely low Fe concentrations in seawater and leads to Fe deficiency for phytoplankton growth. Therefore, it is concluded that the strong ligands in DOM play a chemical role in controlling free ion concentration levels of bioactive metals in the marine environment.
An overview of the recently renovated high-pressure X-ray diffraction (XRD) BL10XU beamline for the diamond anvil cell at SPring-8 is presented. The renovation includes the replacement of the X-ray ...source and monochromator, enhanced focusing systems for high-energy XRD, and recent progress in the sample environment control techniques that are available for high-pressure studies. Other simultaneous measurement techniques for combination with XRD, such as Raman scattering spectroscopy and Mössbauer spectroscopy, have been developed to obtain complementary information under extreme conditions. These advanced techniques are expected to make significant contributions to in-depth understanding of various and complicated high-pressure phenomena. The experience gained with the BL10XU beamline could help promote high-pressure research in future synchrotron radiation facilities.
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