An evaluation of the one percent clustered sample of the 1990 Census of China

We describe and evaluate a one percent clustered sample of the 1990 Census of China, the largest publicly-available micro sample of any Chinese census, using direct inspection as well as comparisons with published data drawn from the complete enumeration. In the absence of official documentation, we elucidate the basis of the clustering; detect duplicate cases; report corrected totals; and make comparisons between the sample data and tabulations based on the complete enumeration at the province and county levels. Although the sample contains several anomalies, we conclude that it is broadly serviceable.1990 Census, China, evaluation, sample data

Rapid 3-D Raytracing For Optimal Seismic Survey Design

Zhang, Jie; Lavely, Eugene; Toksoz, M. NafiA useful approach to optimal seismic survey design is to simulate the seismic response for a suite of a priori subsurface models and shot-receiver templates. The response can be used to evaluate many criteria such as subsurface coverage, target resolution, noise sensitivity, aquisition footprint, data redundancy, long-wavelength statics resolution, and others. A key requirement for practical implementation is the use of an accurate and rapid simulation method. For most cases survey optimization for a highly detailed 3D model would not be useful because (1) such information is often not available, (2) some of the conclusions may not be robust to small changes in the model, and (3) simulation of generally varying complex models would be prohibitively expensive. Instead, a more useful model class for survey design would be 3D models with constant velocity layers separated by arbitrary (and possibly complex) interfaces. The models may be from conjecture or previous seismic surveys. We present a rapid 3D raytracing method optimized for the computation of reflection and refraction wavefronts from a point source in this model class. We demonstrate that the method simulates wave phenomena such as diffraction and head wave propagation. The approach is extremely fast since it avoids traveltime expansion in the volume between interfaces, and solves a simple 2D problem on each interface. Other methods require local propagators (even in constant velocity regions), whereas our approach enables large jumps of wavefronts from interface to interface. The calculation of 3D reflection or refraction traveltimes for a model with an arbitrary interface from one source to any number of receivers requires less than 1 sec of CPU time on a DEC 3000/500 workstation. We briefly review how our new method can be used to facilitate survey resolution computations. We also develop a method for estimating an efficient source-receiver distribution for resolving an assumed 3D structure. To design the receiver distribution, we calculate continuous traveltime slices at the surface from a given source template and plot the RMS curvatures of the wavefronts. The spatial density of the receiver coverage should be in proportion to the locally-varying magnitude of the RMS curvature. Similarly, to determine the optimal source distribution, we sum the RMS curvatures of the wavefront traveltimes due to each source in the entire survey area. In the same way, the magnitude of the curvatures suggests the most important areas for source locations.Gas Research Institute (Contract 5096-210-3781)Massachusetts Institute of Technology. Earth Resources Laboratory. Reservoir Delineation Consortiu

Theoretical investigations in helioseismology

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1990.Includes bibliographical references.by Eugene M. Lavely.Ph.D

Effects of Large-Scale Convection on p-mode Frequencies

We describe an approach for finding the eigenfrequencies of solar acoustic modes (p modes) in a convective envelope in the WKB limit. This approximation restricts us to examining the effects of fluid motions which are large compared to the mode wavelength, but allows us to treat the three-dimensional mode as a localized ray. The method of adiabatic switching is then used to investigate the frequency shifts resulting from simple perturbations to a polytropic model of the convection zone as well as from two basic models of a convective cell. We find that although solely depth-dependent perturbations can give frequency shifts which are first order in the strength of the perturbation, models of convective cells generate downward frequency shifts which are second order in the perturbation strength. These results may have implications for resolving the differences between eigenfrequencies derived from solar models and those found from helioseismic observations.Comment: 27 pages + 6 figures; accepted for publication in Ap

Meridional Circulation and Global Solar Oscillations

We investigate the influence of large-scale meridional circulation on solar p-modes by quasi-degenerate perturbation theory, as proposed by \cite{lavely92}. As an input flow we use various models of stationary meridional circulation obeying the continuity equation. This flow perturbs the eigenmodes of an equilibrium model of the Sun. We derive the signatures of the meridional circulation in the frequency multiplets of solar p-modes. In most cases the meridional circulation leads to negative average frequency shifts of the multiplets. Further possible observable effects are briefly discussed.Comment: 14 pages, 5 figures, submittted to Solar Physics Topical Issue "HELAS

Reynolds stress and heat flux in spherical shell convection

14 pages, 15 figures, submitted to Astron. Astrophys. Version with higher resolution figures can be found at http://www.helsinki.fi/~kapyla/publ.htmlContext. Turbulent fluxes of angular momentum and heat due to rotationally affected convection play a key role in determining differential rotation of stars. Aims. We compute turbulent angular momentum and heat transport as functions of the rotation rate from stratified convection. We compare results from spherical and Cartesian models in the same parameter regime in order to study whether restricted geometry introduces artefacts into the results. Methods. We employ direct numerical simulations of turbulent convection in spherical and Cartesian geometries. In order to alleviate the computational cost in the spherical runs and to reach as high spatial resolution as possible, we model only parts of the latitude and longitude. The rotational influence, measured by the Coriolis number or inverse Rossby number, is varied from zero to roughly seven, which is the regime that is likely to be realised in the solar convection zone. Cartesian simulations are performed in overlapping parameter regimes. Results. For slow rotation we find that the radial and latitudinal turbulent angular momentum fluxes are directed inward and equatorward, respectively. In the rapid rotation regime the radial flux changes sign in accordance with earlier numerical results, but in contradiction with theory. The latitudinal flux remains mostly equatorward and develops a maximum close to the equator. In Cartesian simulations this peak can be explained by the strong 'banana cells'. Their effect in the spherical case does not appear to be as large. The latitudinal heat flux is mostly equatorward for slow rotation but changes sign for rapid rotation. Longitudinal heat flux is always in the retrograde direction. The rotation profiles vary from anti-solar (slow equator) for slow and intermediate rotation to solar-like (fast equator) for rapid rotation. The solar-like profiles are dominated by the Taylor-Proudman balance.Peer reviewe

Spatiotemporal patterns of population in mainland China, 1990 to 2010

According to UN forecasts, global population will increase to over 8 billion by 2025, with much of this anticipated population growth expected in urban areas. In China, the scale of urbanization has, and continues to be, unprecedented in terms of magnitude and rate of change. Since the late 1970s, the percentage of Chinese living in urban areas increased from ~18% to over 50%. To quantify these patterns spatially we use time-invariant or temporally-explicit data, including census data for 1990, 2000, and 2010 in an ensemble prediction model. Resulting multi-temporal, gridded population datasets are unique in terms of granularity and extent, providing fine-scale (~100 m) patterns of population distribution for mainland China. For consistency purposes, the Tibet Autonomous Region, Taiwan, and the islands in the South China Sea were excluded. The statistical model and considerations for temporally comparable maps are described, along with the resulting datasets. Final, mainland China population maps for 1990, 2000, and 2010 are freely available as products from the WorldPop Project website and the WorldPop Dataverse Repository