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211.
Ikkoh Funaki Hidenori Kojima Hiroshi Yamakawa Yoshinori Nakayama Yukio Shimizu 《Astrophysics and Space Science》2007,307(1-3):63-68
To propel a spacecraft in the direction leaving the Sun, a magnetic sail (MagSail) blocks the hypersonic solar wind plasma
flow by an artificial magnetic field. In order to simulate the interaction between the solar wind and the artificially deployed
magnetic field produced around a magnetic sail spacecraft, a laboratory simulator was designed and constructed inside a space
chamber. As a solar wind simulator, a high-power magnetoplasmadynamic arcjet is operated in a quasisteady mode of 0.8 ms duration.
It can generate a simulated solar wind that is a high-speed (above 20 km/s), high-density (1018 m−3) hydrogen plasma plume of ∼0.7 m in diameter. A small coil (2 cm in diameter), which is to simulate a magnetic sail spacecraft
and can obtain 1.9-T magnetic field strength at its center, was immersed inside the simulated solar wind. Using these devices,
the formation of a magnetic cavity (∼8 cm in radius) was observed around the coil, which indicates successful simulation of
the plasma flow of a MagSail in the laboratory. 相似文献
212.
Experiments related to impacts onto three-component targets which could simulate cometary nucleus or planetary regolith cemented by ices are presented here. The impact velocities are from 133 to 632 m s−1. The components are powdered mineral (pyrophylite), H2O ice, and CO2 ice mixed 1:1:0.74 by mass. The porosity of fresh samples is about 0.48. Two types of the samples were studied: nonheated samples and samples heated by thermal radiation. Within the samples a layered structure was formed. The cratering pattern strongly depended on the history of the samples. The craters formed in nonheated targets had regular shapes. The volume was easy to be determined and it was proportional to impact energy E. The crater depth scales as E0.5. Impacts on the thermally stratified target led to ejection of a large amount of material from the loose sub-crustal layer. For some particular interval of impact velocity a cratering pattern can demonstrate unusual properties: small hole through the rigid crust and considerable mass transfer (radially, outward of the impact point) within sub-crustal layer. 相似文献
213.
214.
Frictional discharge at fault asperities: Origin of fractal seismo-electromagnetic radiation 总被引:1,自引:0,他引:1
To investigate the relation between the rock friction and the fractal electromagnetic radiation before the main-shock of earthquakes, we conducted a friction experiment simulating the motion of an asperity on a fault plane, and observed photon emissions due to electric discharge by dielectric breakdown of ambient gases from friction contacts between rock minerals. This indicates that frictional discharges (plasma generations) could occur locally at microscopic asperities on fault surfaces. From concepts on the fractal size-distribution and temporal evolution of fault asperities, the frictional discharge occurring at asperities on the fault plane can be one of origins of the fractal electromagnetic radiation (Benioff electromagnetic radiation) prior to earthquakes. 相似文献
215.
Previous researchers proposed that trachybasalt temper with “poikilitic” sanidine, found in pottery from the Mesa Verde region of the American Southwest, was procured along the eastern Chuska Mountains. This served as one line of evidence that Chaco Canyon was a regional trade center linked to the Chuska Mountains in the ninth to thirteenth centuries. Recent geologic studies, however, revealed other potential sources for the trachybasalt temper. A comparison of petrographic features and geochemical signatures of poikilitic sanidine in rock samples and potsherds shows no definitive correlation of temper materials and a specific geologic source. Several outcrops of trachybasalt are identified as less viable prospects, but the results do not support the idea that the sanidine‐rich temper was exclusively gathered in the Chuska Mountains. This conclusion opens up the possibility that raw materials were gathered from local sources that were more accessible, reducing the dependence on a regional trade center. 相似文献
216.
Residential segregation is a multidimensional phenomenon that encompasses several conceptually distinct aspects of geographical separation between populations. While various indices have been developed as a response to different definitions of segregation, the reliance on such single-figure indices could oversimplify the complex, multidimensional phenomena. In this regard, this paper suggests an alternative graph-based approach that provides more detailed information than simple indices: The concentration profile graphically conveys information about how evenly a population group is distributed over the study region, and the spatial proximity profile depicts the degree of clustering across different threshold levels. These graphs can also be summarized into single numbers for comparative purposes, but the interpretation can be more accurate by inspecting the additional information. To demonstrate the use of these methods, the residential patterns of three major ethnic groups in Auckland, namely Māori, Pacific peoples, and Asians, are examined using the 2006 census data. 相似文献
217.
Yukio Sadahiro 《Transactions in GIS》2023,27(1):260-274
This article develops a method for analyzing spatial and temporal event patterns. Events in this article refer to zero-dimensional objects in the spatiotemporal dimension, which represent the occurrence of crimes, traffic accidents, earthquakes, and so forth. The spatial clustering of sequential events and the increase and decrease in events over time are discussed. These patterns are often observed and analyzed in various academic fields, such as criminology, epidemiology, and geography. However, analytical methods for these patterns have not yet been fully developed. To fill the research gap, this article proposes a new method for analyzing these event patterns. Two statistical measures are utilized, one represents the degree of the spatial clustering of sequential events, and the other evaluates the increase and decrease of events over time. The method is applied to the analysis of the spatial and temporal patterns of the openings of new shops and restaurants in Shibuya-ku, Tokyo. The results gave us interesting empirical findings and indicated the soundness of the method. 相似文献
218.
为调查饱和珊瑚砂液化相关特性与发展规律,针对饱和Chibishi珊瑚砂,开展一系列不排水循环三轴试验,研究相对密度Dr和循环应力比CSR对饱和Chibishi珊瑚砂的超孔隙水压力Δu、轴向应变εa及动强度特性的影响,并分析不同地区珊瑚砂抗液化强度的差异性。结果表明,饱和Chibishi珊瑚砂的Δu发展模式根据不同的CSR水平可以分为前期均匀增长型、前期突增型和后期突增型;此外,采用一种新的孔压模型对前期均匀增长型、前期突增型的孔压比ru进行表征,Chibishi珊瑚砂在相同的Dr条件下,双幅应变εDA达到5%的循环次数N随着CSR水平的增加而逐渐减小;各珊瑚砂在同一里氏震级对应的等效循环振动次数下,抗液化强度CRR的增长模式存在显著差异。研究结果可丰富对珊瑚砂液化特征的认知,同时对近岸和沿海工程的抗震设计提供参考依据。 相似文献