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The purpose of this paper is based on the response surface method, the authors determined the conditions for achieving the optimum rubber-sealing performance by using the maximum contact stress as the response value.

A two-dimensional model of a compression packer rubber was established by finite-element analysis software. Under the single axial load of 53.85 MPa, the four single factors of the end-face inclination angle, subthickness, height of rubber and friction coefficient of the rubber were analyzed.

Results show that the optimum sealing performance of the rubber tube is achieved when the end-face angle is equal to 45º and the thickness of the rubber tube is 9 mm. The response surface designed by Box–Behnken shows that the sealing performance of the rubber tube is the optimum when the end-face inclination angle is 48.1818°, the subthickness is 9 mm, the height of rubber is 90 mm and the friction coefficient is 0.1. Verification test results show that the model is reliable and effective.

Packer operations are performed downhole, and research on real experiments is limited. In this work, the feasibility of such experiments is determined by comparing finite-element modeling with actual experiments, and the results have guiding significance for actual downhole operations.

A little-known “lottery fever” has spread to many parts of rural China over the past 10 years. This is driven by participation in underground lotteries with local bookies. It is called liuhecai, which is the name of the Hong Kong lottery, and is based on guessing the bonus number of the Hong Kong Mark Six lottery. Such lotteries are illegal, but are an open secret. This chapter seeks to understand the meaning of this apparently irrational lottery fever: why people participate in it, why they believe the conspiracy theory that it is rigged (and yet still participate), and why similar lotteries have emerged in both capitalist Taiwan and post-socialist China at this particular time.