No abstract

The calculation of the steady state operability characteristics of nonlinear high-dimensional processes is a difficult task computationally as it involves the mapping of high-dimensional, constrained input sets through the nonlinear process model to a high-dimensional output set. The reverse mapping, from outputs to inputs, also of interest, is equally challenging. In this paper we propose the selection of a finite number of points as an adequately accurate representation of the overall input-output mapping of the detailed model. This approach is motivated by the well established design of experiments (DoE) [Montgomery, D. C. Design and Analysis of Experiments; Wiley: New York, 2005. Box, G. E. P.; Draper, N. R. Response Surfaces, Mixtures, and Ridge Analysis; Wiley: Hoboken, NJ, 2007. Box, G. E. P.; Hunter, J. S.; Hunter, W. G. Statistics for Experimenters: Design, Innovation and Discovery, 2nd ed.; John Wiley & Sons, Inc.: Hoboken, NJ, 2004.] methodology which has been successful in experimentally investigating similar relationships for processes that have not yet been modeled. For this reason, the proposed approach is called design of selective calculations (DoSC). The mapping of only selective points and the development of an interpolative response surface model for the output points enables the calculation of the desired operability sets with a much reduced number of calculations without any significant loss of accuracy. The applicability of the developed method is illustrated with two motivating examples and a plant-wide industrial process, the Tennessee Eastman challenge problem. Of particular interest is the demonstration that the response surface model with quadratic terms is rich enough to accurately describe even the complex phenomenon of input multiplicity. When input multiplicity exists, the image of the boundary of the input set does not fully describe the boundary of the image set. In such a case, mapping only the boundaries of the related sets is not sufficient. Besides its overall computational economy, the proposed method overcomes this important additional challenge.

Salt deposits are commonly regarded as ideal hosts for geologic energy reservoirs. Underground cavern construction-induced damage in salt is reduced by self-healing. Thus, studying the influencing factors on such healing processes is important. This research uses ultrasonic technology to monitor the longitudinal wave velocity variations of stress-damaged rock salts during self-recovery experiments under different recovery conditions. The influences of stress-induced initial damage, temperature, humidity, and oil on the self-recovery of damaged rock salts are analyzed. The wave velocity values of the damaged rock salts increase rapidly during the first 200 h of recovery, and the values gradually increase toward stabilization after 600 h. The recovery of damaged rock salts is subjected to higher initial damage stress. Water is important in damage recovery. The increase in temperature improves damage recovery when water is abundant, but hinders recovery when water evaporates. The presence of residual hydraulic oil blocks the inter-granular role of water and restrains the recovery under triaxial compression. The results indicate that rock salt damage recovery is related to the damage degree, pore pressure, temperature, humidity, and presence of oil due to the sealing integrity of the jacket material.

No abstract

This paper presents the development of load-transfer curves that can be used to estimate the displacement under axial load of driven piles in sand. The maximum skin friction and end-bearing stress are obtained from new ISO 19901-4 cone penetration test (CPT)-based formulations, which were calibrated using a high-quality database of static pile load tests compiled for this purpose. The load–displacement responses measured in the 71 static load tests in this database are used to derive CPT-based non-linear load-transfer curves. It is shown that good estimations of pile displacements can be obtained using CPT data and the normalised formats of shaft and base load-transfer functions provided in the American Petroleum Institute and ISO 19901-4 recommendations.