The ability of a real-time optimization (RTO) system to track the changing optimum closely relies on an accurate model for representing the plant behavior. This paper investigates the effect of model ...fidelity on RTO performance using a simulated industrial boiler network case study. Three optimization approaches with very different modeling fidelity are investigated: (1) model-free direct search method; (2) model-based method using a simplified efficiency curve model; and (3) model-based method using a fundamental model. The model-free direct search method builds a locally linear model using plant data. It takes many steps to reach the optimum, which causes a significant profit loss during tracking. This tracking loss can be reduced by using the model-based RTO system. The RTO system with an updated, detailed fundamental model is able to track fast and large disturbances because the model is accurate in a large range of operation. The RTO system with a simplified efficiency model requires periodic experimentation to correct for the disturbances, which can cause a significant profit loss during experimentation and tracking. This study demonstrates how quantitative performance measures improve as higher fidelity models are used in real-time operations optimization.
A procedure for the extraction of free amino acids was applied to isolate
S-methylmethionine (SMM) from late harvest Petit Manseng grapes. Grapes were destemmed and crushed, and the obtained ...clarified must was percolated through cation-exchange resins (Dowex 50 WX4-100). The retained compounds were eluted with ammonia solution and the extract was finally concentrated. Taking into account the potential DMS (PDMS using heat-alkaline treatment assay) of the initial grape juice used (51.5
nmol
mL
−1) and the concentration factor of the extract (17.9-fold), the PDMS of the final extract (678
nmol
mL
−1) gave an overall recovery of 73.5% for juice SMM. This compound was identified and quantified (484.5
nmol
mL
−1 relatively to
2H
3-SMM used as internal standard) by its selective detection in this extract without derivatization by MALDI-TOF-MS using instrumentation and procedures previously reported to analyze SMM in complex natural extracts. SMM and 22 other amino acids in the initial must and in the final SMM extract were also determined using a Biochrom 30 amino acid analyser with post-column ninhydrin derivatization. SMM peak identification and quantification (401.2
nmol
mL
−1 relatively to norleucine used as internal standard) were carried out by comparison with commercial SMM.
This paper presents a sequential set of tests for model-based Real-Time Optimization (RTO) system design, using the framework of the Design Cost Criteria to evaluate design alternatives. Design Cost ...is defined as the “lost profit” due to offset from the optimal plant operations and variance of the RTO system predictions of optimal operations. Necessary conditions for elimination of offset are presented, which can be implemented in a sequential fashion to concentrate increasing effort on only those models which have satisfied the previous conditions. A method for approximating the variance of the predicted plant optimum is developed. From these tools, a key parameter selection procedure is synthesized and illustrated with a reactor operations optimization example.
In this paper, a novel website is described that provides interactive learning for undergraduate process control. The site engages the students through a set of questions that follow the topic ...sequence in a standard course. The questions begin with simple, yet essential, terminology and definitions, and then move on to engineering applications. Students can request hints for many questions, and they receive feedback for correct and incorrect answers. The software enables students to learn on their own schedule and at their own pace. Suggestions are provided to enable the instructor to complement this computer tool with guidance on self-study learning skills. Those interested cna visity the site, http://www.pc-education.mcmaster.ca, which is open for instructors and students interested in process control.
This paper presents methods for the statistical analysis of plant operations optimization results with special consideration for real-time optimization (RTO) applications. The key challenge is to ...determine whether the results of an optimization calculation should be implemented in the plant. Since feedback data used to correct the model include noise and the effects of high-frequency disturbances, the results of the model-based optimization calculations are corrupted by a stochastic component. The methods developed in this paper apply multivariable statistical hypothesis tests based on control charts in order to distinguish between high-frequency disturbances propagated through the calculations and significant changes in the plant optimization variables with the goals of reducing the frequency of unnecessary changes in the implemented independent optimization variables and increasing plant profits. Only the statistically significant results are implemented in the plant. Case studies indicate that increased profit can be obtained by implementing fewer changes to the process because the preponderance of changes due to noise are rejected whereas most meaningful changes are implemented.
This paper presents a novel robust Model Predictive Control (MPC) method for real-time supply chain optimization under uncertainties. This method optimizes the closed-loop economic performance of ...supply chain systems and addresses different sources of uncertainties located external to and within the feedback loop. The future system behavior is predicted by a closed-loop model, which includes both the open-loop system model and a controller model described by an optimization problem. The robust MPC formulation involves the solution of a constrained, bi-level stochastic optimization problem, which is transformed into a tractable problem involving a limited number of deterministic conic optimization problems solved reliably using an interior point method. The robust controller is applied to a real industrial multi-echelon supply chain optimization problem, and its performance is shown to reduce stock-outs without excessive inventories.
The two rings of (50000) Quaoar Pereira, C. L.; Sicardy, B.; Morgado, B. E. ...
Astronomy & astrophysics,
05/2023, Letnik:
673
Journal Article
Recenzirano
Odprti dostop
Context.
Quaoar is a classical trans-Neptunian object (TNO) with an area-equivalent diameter of 1100 km and an orbital semi-major axis of 43.3 astronomical units. Based on stellar occultations ...observed between 2018 and 2021, an inhomogeneous ring (Q1R, i.e., Quaoar’s first ring) has been detected around this body.
Aims.
A new stellar occultation by Quaoar was observed on August 9, 2022, with the aim of improving Quaoar’s shape models and the physical parameters of Q1R, while searching for additional material around the body.
Methods.
The occultation provided nine effective chords across Quaoar, pinning down its size, shape, and astrometric position. Large facilities, such as Gemini North and the Canada-France-Hawaii Telescope (CFHT), were used to obtain high acquisition rates and signal-to-noise ratios. The light curves were also used to characterize the Q1R ring (radial profiles and orbital elements).
Results.
Quaoar’s elliptical fit to the occultation chords yields the limb with an apparent semi-major axis of 579.5 ± 4.0 km, apparent oblateness of 0.12 ± 0.01, and area-equivalent radius of 543 ± 2 km. Quaoar’s limb orientation is consistent with Q1R and Weywot orbiting in Quaoar’s equatorial plane. The orbital radius of Q1R is refined to a value of 4057 ± 6 km. The radial opacity profile of the more opaque ring profile follows a Lorentzian shape that extends over 60 km, with a full width at half maximum (FWHM) of ∼5 km and a peak normal optical depth of 0.4. Besides the secondary events related to the already reported rings, new secondary events detected during the August 2022 occultation in three different data sets are consistent with another ring around Quaoar with a radius of 2520 ± 20 km, assuming the ring is circular and co-planar with Q1R. This new ring has a typical width of 10 km and a normal optical depth of ∼0.004. Just as Q1R, it also lies outside Quaoar’s classical Roche limit.
PDF
