Seasonal dependence of the longitudinal variations of nighttime ionospheric electron density and equivalent winds at southern midlatitudes

It has been indicated that the observed Weddell Sea anomaly (WSA) appeared to be an extreme manifestation of the longitudinal variations in the Southern Hemisphere, since the WSA is characterized by greater evening electron density than the daytime density in the region near the Weddell Sea. In the present study, the longitudinal variations of the nighttime F2-layer peak electron density at southern midlatitudes are analyzed using the observations of the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites between 2006 and 2008. It is found that significant longitudinal difference (> 150%) relative to the minimum density at each local time prevails in all seasons, although the WSA phenomenon is only evident in summer under this solar minimum condition. Another interesting feature is that in summer, the maximum longitudinal differences occur around midnight (~ 23:00–00:00 LT) rather than in the evening (19:00–21:00 LT) in the evening, when the most prominent electron density enhancement occurs for the WSA phenomenon. Thus the seasonal–local time patterns of the electron density longitudinal variations during nighttime at southern midlatitudes cannot be simply explained in terms of the WSA. Meanwhile, the variations of the geomagnetic configuration and the equivalent magnetic meridional winds/upward plasma drifts are analyzed to explore their contributions to the longitudinal variations of the nighttime electron density. The maximum longitudinal differences are associated with the strongest wind-induced vertical plasma drifts after 21:00 LT in the Western Hemisphere. Besides the magnetic declination–zonal wind effects, the geographic meridional winds and the magnetic inclination also have significant effects on the upward plasma drifts and the resultant electron density

The Case Record of Ba-Yu-Quan Anchor Slab Retaining Wall

Anchor slab retaining wall is a kind of retaining structure, which consists of prefabricated rib-columns, panel slabs, tie-bars and anchor slabs embedded in earth fill. Since the structure was first used and developed in China in 1974, many such structure have been built on railways and other engineering projects. The reviewer of Second International Conference on Case Histories in Geotechnical Engineering gave a comments about this structure as follows: Chinese method anchor slab the construction should interest the western world . Ba-Yu-Quan anchor slab retaining wall has been instrumented to measure the load on the tie-bar, the horizontal displacement of the rib-columns, the horizontal earth pressure acting at the panel slabs, and the backfill settlement at different positions. This paper presents project description, construction of the project, data obtained from field observations and the comparison result with analysis and predicted values

Coupling of Light and Mechanics in a Photonic Crystal Waveguide

Observations of thermally driven transverse vibration of a photonic crystal waveguide (PCW) are reported. The PCW consists of two parallel nanobeams with a 240 nm vacuum gap between the beams. Models are developed and validated for the transduction of beam motion to phase and amplitude modulation of a weak optical probe propagating in a guided mode (GM) of the PCW for probe frequencies far from and near to the dielectric band edge. Since our PCW has been designed for near-field atom trapping, this research provides a foundation for evaluating possible deleterious effects of thermal motion on optical atomic traps near the surfaces of PCWs. Longer term goals are to achieve strong atom-mediated links between individual phonons of vibration and single photons propagating in the GMs of the PCW, thereby enabling opto-mechanics at the quantum level with atoms, photons, and phonons. The experiments and models reported here provide a basis for assessing such goals, including sensing mechanical motion at the Standard Quantum Limit (SQL).Comment: 13 pages, 13 figure

Optimal Energy Dissipation in Sliding Friction Simulations

Non-equilibrium molecular dynamics simulations, of crucial importance in sliding friction, are hampered by arbitrariness and uncertainties in the removal of the frictionally generated Joule heat. Building upon general pre-existing formulation, we implement a fully microscopic dissipation approach which, based on a parameter-free, non-Markovian, stochastic dynamics, absorbs Joule heat equivalently to a semi-infinite solid and harmonic substrate. As a test case, we investigate the stick-slip friction of a slider over a two-dimensional Lennard-Jones solid, comparing our virtually exact frictional results with approximate ones from commonly adopted dissipation schemes. Remarkably, the exact results can be closely reproduced by a standard Langevin dissipation scheme, once its parameters are determined according to a general and self-standing variational procedure

Some Considerations in Seismic Analysis of Spatial Structure Acounting for Soil-Structure Interaction

p. 323-332The seismic analysis of spatial structure in the last 40 years was developed from the static to the dynamic analysis, from the elastic analysis to the elasto-plastic analysis, from the deterministic to the stochastic analysis, and from the uniform seismic excitation in one dimension to the non-uniform seismic excitation in multi-dimensions. The practices show that the model of the spatial structure should be built not only including the roof structure, but the supporting structure and even the foundation as well. Seismic analyses for the nuclear plant, the offshore flatform and the high-rise building have shown that the seismic response of those structures considering the soil-structure interaction (SSI) effect varied a lot compared with that of rigid-connected model. However, few studies have been done for seismic analysis of spatial structures accounting for soil-structure interaction. In present paper, the 3D BNWF(Beam On Nonlinear Winkler Foundation ) SSI model for the shallow foundation and the 3D dynamic p-y model for the deep foundation, the earhtquake input model, the elasto-plastic hysteritic model suitable for the superstructure and the substructure are put forward for the seismic analysis of spatial structure. The research will lay a good foundation for the 3D nonlinear analysis of spatial structure incoporating the SSI under strong earthquake shaking and further promote the performance based design of the spatial structure.Xue, SD.; Luan, XB. (2009). Some Considerations in Seismic Analysis of Spatial Structure Acounting for Soil-Structure Interaction. Editorial Universitat Politècnica de València. http://hdl.handle.net/10251/652