The present work investigates equilibrium conditions and dissociation enthalpy of hydrates formed from CO 2 -TBAB(tetra-n-butylammonium bromide)-water mixtures. Differential Thermal Analysis (DTA) was used for Hydrate-Liquid-Vapour (H-L-V) equilibrium condition determination in a TBAB concentration range from 4.43 to 9.01 wt% and in a CO 2 pressure range from 0.3 to 2.5 MPa. The results showed that the presence of TBAB allowed decreasing the formation pressure of CO 2 hydrate by approximately 74 and 87% at 283 and 279 K, respectively. Moreover, pressure reductions were dependent on the TBAB concentration. The dissociation enthalpy and the composition of double hydrate formed from 9.01 wt% TBAB solution were determined by both the DTA and Clapeyron equation. The DTA method resulted in 313.2 kJ per kg of hydrate for the dissociation enthalpy and 2.51CO 2 •TBAB•38H 2 O for composition of the double hydrate. For the use of Clapeyron equation, the volume change was defined by taking into account the gas solubility in the liquid phase. The calculation results showed a discrepancy with the experimental data obtained by DTA, suggesting the limited application of Clapeyron equation in the CO 2 -TBAB-water system.

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SUMMARYThe steady-forced and earthquake responses of SDF systems with a non-linear uid viscous damper (FVD) are investigated. The energy dissipation capacity of the FVD is characterized by the supplemental damping ratio sd and its non-linearity by a parameter designated . It is found that the structural response is most e ectively investigated in terms of sd and because (1) these two parameters are dimensionless and independent, and (2) the structural response varies linearly with the excitation intensity. Damper non-linearity has essentially no in uence on the peak response of systems in the velocity-sensitive spectral region, but di erences up to 14% were observed in the other spectral regions. The structural deformation is reduced by up to 25% when sd = 5%; and by up to 60% when sd = 30%. Non-linear FVDs are advantageous because they achieve essentially the same reduction in system responses but with a signiÿcantly reduced damper force. For practical applications, a procedure is presented to estimate the design values of structural deformation and forces for a system with nonlinear FVD directly from the design spectrum. It is demonstrated that the earthquake-induced force in a non-linear FVD can be estimated from the damper force in a corresponding system with linear FVD, its peak deformation, and peak relative velocity; however, the relative velocity should not be approximated by the pseudo-velocity as this approximation introduces a large error in the damper force. Finally, a procedure is presented to determine the non-linear damper properties necessary to limit the structural deformation to some design value or the structural capacity for a given design spectrum.

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In this paper we prove some results about the stable homotopy and cohomotopy of spaces related to the infinite real protective space RP∞. These include M. E. Mahowald's conjecture on the limit of stable homotopy of stunted real projective spaces RP2N+m/RP2N−m as N, m → ∞, G. Segal's Burnside ring conjecture forand the stable analogue of a conjecture of D. Sullivan on RP∞.