Summary Equatorial field-aligned irregularities have been studied by using low-latitude echotrain and hybrid whistlers observed at Sakushima Station (geomag. lat. 24°). The structure is discussed in relation to the propagation mode trapped by field-aligned irregularities. We then find that the field-aligned irregularities responsible for the trapping of low latitude whistlers are of such small dimension as the HF ducts. 相似文献
Experimental studies have been carried out on the dynamic stability of a cantilever cylindrical shell partially filled with liquid, under vertical excitation. Two polyester test cylinders with radius 100 mm, thickness 0.25 mm, and lengths 113 and 227 mm were used. The test cylinder was harmonically excited with constant acceleration- or displacement-amplitude. It was found that not only the parametric principal instability resonance but also the parametric combination involving two natural vibrations, each of which has the same circumferential wave number but different axial mode numbers, could occur. The latter type of vibration apparently has not been previously studied. By varying the dimensionless water height from 0.25 to 1.0 stepwise by 0.25 increments, the instability regions and vibration modes were determined for the two test cylinders. The response waves of shell wall and liquid free surface, and axial and circumferential vibration modes were also observed. 相似文献
Theoretical analyses are presented for the dynamic stability of a clamped-free cylindrical shell partially filled with liquid, under vertical excitation. In the analyses, the dynamic version of the Donnell equations and the velocity potential theory were used for the motions of the shell and the liquid, respectively. The problem was solved by using the modified Galerkin method so as to satisfy the boundary conditions. The equations of motion coupling the shell and the liquid were derived from a type of coupled Mathieu's equation. It is found that the parametric principal resonance could occur, as well as the parametric combination resonance of the sum type, involving two natural vibrations with the same circumferential wave number but with different axial mode number. The latter type of parametric resonance apparently has not been previously studied. The instability regions where parametric resonance occurs were determined by using Hsu's method.17 To compare with the experimental results which had been stated in a companion paper,15 detailed numerical calculations were carried out for the two test cylinders partially filled with water. Excellent agreement between theory and experiment was demonstrated for the instability regions. 相似文献
Ensemble averages of temperature before and after step-like temperature fluctuations reveal the presence of inverted ramps in a stable surface layer. Normalized frequency of upward steps increases with increasing stability, whereas normalized magnitude of the temperature step decreases with stability and becomes constant at about Ri = 1. These results suggest that the significance of temperature steps increases as stability increases. In moderate stability, the temperature pattern shows a gradual decrease after an upward step, which can be called a time-inverted ramp. Descending air and large downward heat flux are observed in a time-inverted ramp, suggesting a contribution from an ordered motion in wind. On the other hand, the temperature steps are related to gravity waves in strong stability. 相似文献
Two-to threefold inward increase of 10Be, 9Be, Cu and Ni have been found in surface layers of marine ferromanganese deposits. We interpret this phenomenon as reflecting the manner in which the Be isotopes and probably other trace metals (e.g. Cu and Ni) are incorporated. On reaching the sea floor exchangeable Be is released from its carrier phase to the pore water of the ferromanganese deposits, diffuses inward and gets fixed into the deposits. The fixation process may be related to the mineralogical reorganizations suggested by previous studies. We have modeled this concept and applied it to a Mn crust on which detailed analyses of Cu, Ni and natural decay-series nuclides, as well as Be isotopes are made. Post-depositional fixation of Th isotopes may also occur. The redistributions of Be and Th isotopes are confined to regions very close to the surface of the deposits. For all practical purposes, they will not affect growth rate determinations conventionally done using these isotopes. The “linearly” extrapolated ratio to the surface from deep layers of a Mn deposit does not necessarily represent that ratio in sea water. 相似文献
When a subduction-zone earthquake occurs, the tsunami height must be predicted to cope with the damage generated by the tsunami. Therefore, tsunami height prediction methods have been studied using simulation data acquired by large-scale calculations. In this research, we consider the existence of a nonlinear power law relationship between the water pressure gauge data observed by the Dense Oceanfloor Network System for Earthquakes and Tsunamis (DONET) and the coastal tsunami height. Using this relationship, we propose a nonlinear parametric model and conduct a prediction experiment to compare the accuracy of the proposed method with those of previous methods and implement particular improvements to the extrapolation accuracy.
We used more than 25,000 nutrient samples to elucidate for the first time basin-scale distributions and seasonal changes of surface ammonium (NH4+) and nitrite (NO2?) concentrations in the Pacific Ocean. The highest NH4+, NO2?, and nitrate (NO3?) concentrations were observed north of 40°N, in the coastal upwelling region off the coast of Mexico, and in the Tasman Sea. NH4+ concentrations were elevated during May–October in the western subarctic North Pacific, May–December in the eastern subarctic North Pacific, and June–September in the subtropical South Pacific. NO2? concentrations were highest in winter in both hemispheres. The seasonal cycle of NH4+ was synchronous with NO2?, NO3?, and satellite chlorophyll a concentrations in the western subtropical South Pacific, whereas it was synchronous with chlorophyll-a but out of phase with NO2? and NO3? in the subarctic regions. 相似文献
This paper addresses the study conducted on the performance of landfill liner interface parameters. Interface shear strength
parameters for various combinations of 9 different lining materials were studied and presented in this paper. This comprehensive
testing program covers the interfaces between: (1) soil and compacted clay liner (CCL), (2) geomembrane (HDPEs or PVC) and
soil, (3) geosynthetic clay liner (GCL)/CCL and soil, (4) geomembrane and geotextile, (5) geotextile and soil, (6) geotextile
and GCL/CCL, and (7) geomembrane and GCL/CCL. The experiments were conducted for both at dry or optimum moisture condition
and at saturated or wet condition. The interface performance under both conditions were compared to access the material performances.
Tabulated summaries of interface test data under dry or optimum moisture condition (OMO) and saturated or wet condition are
presented in the paper. 相似文献