Golden State Baptist College

This paper studies coalition formation among individuals who differ in productivity. The output of a coalition is determined by the sum of productivities if the coalition exceeds a minimal threshold of members. We consider competitive societies in which the surplus of a coalition is split according to productivity and egalitarian societies in which coalitions split their surplus equally. Preferences of coalition members depend on their material payoffs, but are also influenced by positional concerns, which relate their material payoffs to the average material payoff in the coalition. Our analysis uses two stability notions, the Core and the Myopic Stable Set. Both competitive and egalitarian societies lead to segregated partition structures. For competitive societies, all stable allocations are based on bottom-up segregation, i.e., individuals with adjacent productivities form coalitions and if some individuals are not part of a productive coalition, then these are the most productive ones. For egalitarian societies, we obtain top-down segregation in all stable allocations. Again it holds that individuals with adjacent productivities form coalitions, but now the least productive individuals may not be part of any productive coalition. If all individuals have different productivity levels, then the material efficiency of competitive societies is below that of egalitarian societies.

We report on a comprehensive set of observations of gamma-ray burst 050716, detected by the Swift satellite and subsequently followed-up rapidly in X-ray, optical and near-infrared (NIR) wavebands. The prompt emission is typical of long-duration bursts, with two peaks in a time interval of T 90 = 68 s (15-350 keV). The prompt emission continues at lower flux levels in the X-ray band, where several smaller flares can be seen on the top of a decaying light curve that exhibits an apparent break around 220 s post-trigger. This temporal break is roughly coincident with a spectral break. The latter can be related to the extrapolated evolution of the break energy in the prompt y -ray emission, and is possibly the manifestation of the peak flux break frequency of the internal shock passing through the observing band. A possible 3o change in the X-ray absorption column is also seen during this time. The late-time afterglow behaviour is relatively standard, with an electron distribution power-law index of p = 2; there is no notable temporal break out to at least 10 d. The broad-band optical/NIR to X-ray spectrum indicates a redshift of z ≥ 2 for this burst, with a host-galaxy extinction value of E B-V ≈ 0.7 that prefers a small magellanic cloud (SMC)-like extinction curve.

Abstract Cement Systems require conformance of specific parameters for the longevity of the system placed as a sheath. Challenges of the system design are exacerbated considering the environment for placement of the sheath. HPHT cement systems require special design attention, and the authors propose to share one such case history in designing of the HPHT system for Eastern India Offshore. HPHT cement systems require not only modified testing procedures, but products also. HPHT cement system products are required to withstand BHST temperatures for the life of the well without considerably altering the slurry system properties. Modified test procedures and products requirements for slurry system bring additional logistical challenges like preparation and availability of right cement blend for testing and preparing the slurry system for the application. Considering the temperature gradient of 2.23°F/100ft, bottom hole static temperature (BHST) for the 7" liner job was 467°F. The mud weight for the section was planned between 14-16 ppg (1.67 to 1.9 sg). Computed BHCT alone was considered inadequate and determination of the hot spot in the wellbore was required. Computerized simulator was used for the purpose. Results show that the hot spot temperature predicted by the simulator was higher than the computed BHCT and the depth of the hot spot was shallower than TVD as normally anticipated. The simulator runs are recommended for determination of hot spot for HPHT testing of cement systems in particular. The simulator considers effects of various fluids pumped and their contact times along with the heat capacities during the application. Product choice for preparation of the Cement systems used earlier for the high temperatures encountered in Western India offshore were reviewed and preliminary testing was carried out on the basis of the prognosed temperature. However predictions from the temperature simulator yielded higher temperatures for the East coast well. This required a different product set for the cement system design. The authors feel that the review of this case history and the design challenges at this technology meet shall potentially benefit the design engineers in understanding and enhancing their knowledge about design practices for HPHT cement systems.