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An analytical electrothermal model is developed and validated using experimental measurements. This model is based on known equations of the thermoelectric theory by accounting for the influence of the temperature on the internal properties of thermoelectric generators. General expressions for the internal properties of thermoelectric generators for different ranges of temperatures are determined. The validation of the model shows that representing the variations of the electrical internal resistance and Seebeck coefficient by linear and quadratic analytic expressions, respectively, as a function of the hot-side temperature is satisfactory. The results show the importance of including the effects of the temperature on the properties of the thermoelectric generator. This is especially true because the maximum generated power is realized when the load resistance is set equal to the internal resistance. The model is used to determine characteristic curves for optimal performance of these generators under different operating hot-side temperatures and temperature differences.

[1] Temporal variability in the Earth's gravity field has been estimated from 4 years of satellite laser ranging (SLR) to five geodetic satellites, Lageos 1 and 2, Stella, Starlette, and Ajisai supplemented by over 2 years of CHAMP precise orbital positioning, attitude quaternions, and accelerometry. The study considers variability at the annual and semiannual periodicities in the full field of degrees 2-6. A singular value decomposition has been employed in an attempt to recover variability from stand-alone CHAMP data. Temporal gravity field variability from SLR and from SLR and CHAMP has been computed and compared against geophysical models for surface mass redistribution. For a 4 Â 4 field best agreement of the annual variation results in an RMS geoid difference of 0.76 mm with correlation coefficients above 0.85. On extending to a 6 Â 6 field agreement decreases to about 1.5 mm RMS in geoid height with correlations of 0.6 at the annual cycle. For the extended field the ocean mass redistribution from Ocean Circulation and Climate Advanced Modeling project and TOPEX is seen to be deficient with near comparable correlations being obtained by neglecting the ocean contribution. The semiannual signal is weaker and less well determined. For the 4 Â 4 field, correlations are no better than 0.6 with RMS of 1 mm between the SLR and geophysical models. Results show that CHAMP has a positive effect on the annual variation for a 4 Â 4 field but marginal for the extended 6 Â 6 field. CHAMP has a negative impact at the semiannual frequency.Citation: Moore, P., Q. Zhang, and A. Alothman (2005), Annual and semiannual variations of the Earth's gravitational field from satellite laser ranging and CHAMP,

The present‐day motions in and around the Arabian plate involve a broad spectrum of tectonic processes including plate subduction, continental collision, seafloor spreading, intraplate magmatism, and continental transform faulting. Therefore, good constraints on the relative plate rates and directions, and on possible intraplate deformation, are crucial to assess the seismic hazard at the boundaries of the Arabian plate and areas within it. Here we combine GNSS‐derived velocities from 168 stations located on the Arabian plate with a regional kinematic block model to provide updated estimates of the present‐day motion and internal deformation of the plate. A single Euler pole at 50.93 ± 0.15°N, 353.91 ± 0.25°E with a rotation rate of 0.524 ± 0.001°/Ma explains well almost all the GNSS station velocities relative to the ITRF14 reference frame, confirming the large‐scale rigidity of the plate. Internal strain rates at the plate‐wide scale (∼0.4 nanostrain/yr) fall within the limits for stable plate interiors, indicating that differential motions are compensated for internally, which further supports the coherent rigid motion of the Arabian plate at present. At a smaller scale, however, we identified several areas within the plate that accommodate strain rates of up to ∼8 nanostrain/yr. Anthropogenic activity and possible subsurface magmatic activity near the western margin of the Arabian plate are likely responsible for the observed local internal deformation. Put together, our results show a remarkable level of stability for the Arabian lithosphere, which can withstand the long‐term load forces associated with active continental collision in the northeast and breakup to the southwest with minimal internal deformation.

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