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李发根 《上海交通大学学报(英文版)》2008,13(6):679-683
We show that the Zhang-Yang-Zhu-Zhang identity-based authenticatable ring signcryption scheme is not secure against chosen plaintext attacks.Furthermore, we propose an improved scheme that remedies the weakness of the Zhang-Yang-Zhu-Zhang scheme.The improved scheme has shorter ciphertext size than the Zhang-Yang-Zhu-Zhang scheme.We then prove that the improved scheme satisfies confidentiality, unforgeability, anonymity and authenticatability. 相似文献
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Masaru Tsujimoto Takashi Uehiro Hiroshi Esaki Takeshi Kinoshita Ken Takagi Susumu Tanaka Hiroshi Yamaguchi Hideo Okamura Masuho Satou Yoshimasa Minami 《Journal of Marine Science and Technology》2009,14(1):89-103
To acquire the wind energy of the oceans, a sailing wind farm has been proposed. The wind farm considered is composed of a
semisubmersible floating structure, 11 windmills, four sails, six thrusters, and storage for hydrogen. To maximize the acquired
energy, an effective algorithm to search for optimum routes was developed. The algorithm is based on the fact that beam winds
yield a maximum of acquired energy. This feature reduces the computation time, and, consequently, efficient route optimization
becomes possible in a reasonable time. After setting an operational area for the wind farm, navigation simulations for a 1-year
period were carried out. A numerical weather forecast was used as well as the responses of the floating structure, such as
the speed of the structure, the output power of the windmills, and the time of course changes. In the simulation, the wind
farm evades rough seas to avoid structural damage, and an optimum route is searched for. The capacity factor of the system
was used to evaluate the efficiency of the optimized routes. From the simulations, the maximum capacity factor achieved was
42.6%. The dependency of the capacity factor on the initial position of the wind farm was also examined. It was shown that
offshore from Sanriku in northeastern Japan is an area suited to the operation of the wind farm. The effect of the initial
position on consecutive periods of operation is discussed. 相似文献
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日本城市轨道交通概况 总被引:1,自引:1,他引:0
介绍了日本3处主要城市地区(东京都、京阪神地区、中京地区)轨道交通线网的状况以及日本铁道公司的管理情况、生产能力.把轨道交通公司每个员工平均创造运营收入作为一个重要的衡量指标,衡量运营的业绩.简要介绍了日本的一些轨道交通制式. 相似文献
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Ken Takagi 《Journal of Marine Science and Technology》2006,11(2):100-110
The diffraction and radiation problems of a two dimensional multihull structure were investigated by application of the scattering
matrix theory. The scattering matrix theory is widely used to analyze wave interaction problems in various scientific fields.
The research is focused on the zeros of the wave exciting force near resonance, which occurs both in the diffraction problem
and the radiation problem. At the zeros of the wave exciting force, the wave exciting force for the overall structure is zero,
but each demihull undergoes wave excitation. At near-resonant frequencies, the amplitude of the traveling wave between adjacent
demihulls becomes very large and the demihulls experience very large wave forces. A number of simple equations for representing
the hydrodynamic properties of the multihull structure at the zeros and near-resonant frequencies are obtained. Numerical
examples show that these simple equations well explain the hydrodynamic forces and the wave system in the spaces between the
demihulls. 相似文献
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The very large mobile offshore structure (VLMOS) for wind power generation is one example of challenging future technologies
to create a new backbone of energy resource of our country. The National Institute for Environmental Studies Japan has been
studying this concept and found that increasing the capacity factor and reducing the weight of the structure are keys to make
this concept successful. We investigated the navigation logic to improve the capacity factor and performed a fatigue assessment
to ensure the structural safety of light weight design. Taking the knowledge on the seasonal weather condition in the Pacific
Ocean into consideration, improved strategy of the VLMOS navigation for maximizing the generating power is proposed. Navigation
simulations show that it is easy to achieve more than 40% capacity factor and to escape from high seas. Using wind and wave
data obtained from the navigation simulations, an assessment of the fatigue damage has been performed. It is stated that the
structure has enough fatigue strength for a 100 years of operation even if wind turbines get more than 40% of the capacity
factor. 相似文献
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